docs: rewrite AGENTS.md as a 10-mode project instruction set

Replaces the 19-line stub with a structured instruction set that the AI
agent reads when working in this repo. Four sections:

1. Repository map — entry points, core internal packages with the real
   file each concern lives in, and the test surface (narrow test
   command, snapshot tooling, race-flags-on-Windows caveat).
2. Conventions — Go 1.25 / toolchain 1.26.4, charm.land v2 pin, mvdan.cc
   shell parsing, gofmt/vet gates, the no-hex-outside-theme rule, the
   model.go/view.go split, error-wrapping discipline.
3. Ten discrete agent modes — Add slash command, Add tool, Add
   provider, Add model entry, Add specialist, Add sandbox rule,
   Modify the TUI, Debug a failing test, Cut a release, Run a security
   or quality audit. Each mode names the files to touch, the pattern
   to follow (with a concrete sibling file cited), what NOT to do, and
   the runnable verification command.
4. Hard rules across all modes — never destructive without explicit
   user message, never edit unread files, never widen tool permissions
   without a test, never delete tests, never commit secrets.

Every file path cited in the doc is one that actually exists on this
branch. No external references, no "inspired by", no credits — pure
project-specific instructions for working on Zero.

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

AGENTS.MD

@@ -1,16 +1,311 @@
 ---
-description: Use Go-native project commands; Node is only for the npm wrapper.
+description: Project-level instruction set for the AI agent working in this repo. Ten discrete modes covering the recurring engineering workflows on Zero.
 globs: "*.go, *.js, package.json, .github/workflows/*.yml, docs/*.md"
 alwaysApply: false
 ---
 
-Default to Go commands in this repository.
+# AGENTS.md
 
-- Use `go run ./cmd/zero` to launch the local CLI.
-- Use `go test ./...` for the repository test suite.
-- Use `go run ./cmd/zero-release build` to build the release-facing binary.
-- Use `go run ./cmd/zero-release smoke` to smoke-test the built binary.
-- Use `go run ./cmd/zero-release package` and `go run ./cmd/zero-release verify` for release artifact checks.
-- Use `go run ./cmd/zero-perf-bench` for performance smoke work.
-- Do not add Bun or TypeScript build/test dependencies for repository validation.
-- Use Node only when directly exercising the npm wrapper at `bin/zero.js`.
+Instructions for the AI agent working inside the `zero` repository. Read this before any non-trivial change.
+
+## 1. Repository map
+
+### Entry points
+
+- `cmd/zero` — primary CLI binary. Run with `go run ./cmd/zero`.
+- `cmd/zero-release` — release tooling. `build`, `smoke`, `package`, `verify`. Never bypass.
+- `cmd/zero-seccomp` — Linux seccomp profile generator for the sandbox.
+- `cmd/zero-perf-bench` — performance smoke work.
+- `cmd/zero-pr-review` — local PR-review runner.
+- `bin/zero.js` — npm wrapper around the Go binary. Touch only when adjusting the npm surface.
+
+### Core internal packages
+
+- `agent/` — the agent loop. Prompt in, tool calls out, results back, repeat. `guardrails.go` holds the loop's stop and confirmation thresholds. `loop.go` is the main state machine.
+- `tui/` — terminal UI built on `charm.land/bubbletea/v2` and `charm.land/lipgloss/v2`. `model.go` holds state, `view.go` is pure render, `command_center.go` dispatches slash commands, `theme.go` owns every color and border (hex literals are forbidden elsewhere).
+- `providers/` — LLM adapters. One subdir per provider: `openai/`, `anthropic/`, `gemini/`, `providerio/`. `factory.go` registers them.
+- `sandbox/` — exec gating and risk classification. `risk.go` defines patterns, `engine.go` decides allow/deny, `paths.go` and `pathlists.go` handle allow/deny lists.
+- `sessions/` — session state, persistence, resume, title generation.
+- `specialist/` — sub-agent routing. Specialists run scoped tasks with their own tool whitelist. `builtin.go` declares the interface, `runtime.go` runs them, `manifest.go` and `exec.go` are the execution paths.
+- `swarm/` — multi-agent coordination for batched work.
+- `mcp/` — Model Context Protocol client and tool bridge.
+- `modelregistry/` — model catalog, capability flags (vision, tool calls, reasoning efforts), cost data. `catalog.go` is `DefaultModelEntries`.
+- `providercatalog/` — provider descriptors (base URLs, auth env vars, default model).
+- `tools/` — agent-callable tools. Each tool implements the `Tool` interface in `tools/types.go`. `registry.go` is the central map; `CoreToolsScoped` / `CoreReadOnlyToolsScoped` / `CoreWriteToolsScoped` / `CoreShellToolsScoped` / `CoreNetworkTools` are the registration sites.
+- `cli/` — top-level command wiring. `app.go` is the entry, `command_center.go` dispatches subcommands, per-feature files (`exec.go`, `sessions.go`, `setup.go`, etc.) implement each subcommand.
+
+Other packages worth knowing: `config/`, `redaction/`, `secrets/`, `imageinput/`, `cron/`, `doctor/`, `browser/`, `background/`, `lsp/`, `hooks/`, `update/`, `usage/`, `verify/`, `testrunner/`, `selfverify/`, `workspaceindex/`, `worktrees/`, `workspaceseed/`, `specmode/`, `streamjson/`, `notify/`, `keyring/`, `observability/`, `oauth/`, `provideroauth/`, `provideronboarding/`, `providerhealth/`, `providermodelcatalog/`, `providermodeldiscovery/`, `npmwrapper/`, `agenteval/`, `zerocommands/`, `zerogit/`, `zeroruntime/`, `release/`, `review/`, `repomap/`, `repoinfo/`, `search/`, `skills/`, `plugins/`.
+
+### Test surface
+
+- Tests live next to the file they cover (`foo.go` → `foo_test.go`). No separate `tests/` tree.
+- Snapshot tests use `charmbracelet/x/exp/golden` (visible in `go.sum`).
+- `go test ./internal/<pkg>/ -run TestX -v` for narrow runs; `go test ./...` for the full suite.
+- No `-race` on Windows (no gcc toolchain). On Linux/macOS, `-race` is fine.
+
+## 2. Conventions
+
+- Go 1.25, toolchain `go1.26.4`. Charm libs are pinned to v2 (`charm.land/bubbletea/v2`, `charm.land/lipgloss/v2`).
+- Shell parsing uses `mvdan.cc/sh/v3`, not `os/exec` + string concatenation. Never invent your own shell tokenizer.
+- `gofmt -l <files>` and `go vet ./...` must pass before commit. CI enforces both.
+- The npm wrapper at `bin/zero.js` is the only Node-touching surface; everything else is Go-native. Do not add Bun or TypeScript build deps.
+- Theme tokens are the single source of truth for color and border. Hex literals anywhere except `internal/tui/theme.go` are rejected.
+- The TUI split is strict: `model.go` owns state, `view.go` is pure render. Styling calls (`Style.Render`, `NewStyle`) live in `view.go` and render helpers under `tui/`; `model.go` may call `lipgloss.Width` for column measurements but never applies styles.
+- Errors are wrapped with `fmt.Errorf("...: %w", err)` and surface context. Never swallow errors silently.
+- Public API changes require a one-line note in the PR body explaining the impact and the migration path.
+
+## 3. Ten agent modes
+
+Each mode is a discrete workflow the AI agent adopts when the task matches. Pick the mode at the start of the task; do not blend them.
+
+### Mode 1 — Add a slash command
+
+Touch files:
+
+- `internal/tui/commands.go` — add a `commandDefinition` entry. Set `name`, `aliases`, `usage`, `group`, `description`, `kind` (one of the `commandKind` constants in this file).
+- `internal/tui/command_center.go` — add a `case command<Name>:` branch to the slash-command dispatch. Match the dispatch shape used by existing commands: read `command.text`, mutate model state, append a transcript row.
+- `internal/tui/<feature>.go` — co-locate the handler with the related feature. Handler signature is `(model, args) (model, string)` where the string is the status text the transcript displays.
+- `internal/tui/view.go` or `internal/tui/command_output.go` — only if the command renders a card or panel; reuse the existing `commandCard` and `commandOutput` helpers.
+
+Pattern to follow: copy `commandEffort` end-to-end (definition in `commands.go`, dispatch in `command_center.go`, handler in `session_controls.go`). Do not invent a new shape.
+
+What NOT to do:
+
+- Do not register the command in two places. One definition, one dispatch, one handler.
+- Do not read input from `m.input.Value()` inside the handler. The dispatch already passes `command.text`.
+- Do not mutate `m.picker` from inside a slash-command handler. Use `m.openXxxPicker()` if a picker is needed.
+
+Verification:
+
+```
+go build ./cmd/zero
+go test ./internal/tui/ -run Test<Command> -v
+```
+
+### Mode 2 — Add a tool
+
+Touch files:
+
+- `internal/tools/<name>.go` — implement the `Tool` interface from `internal/tools/types.go`. Required methods: `Name()`, `Description()`, `Parameters()`, `Safety()`, `Run(ctx, args) Result`. Fill `Safety{ SideEffect, Permission, Reason }` honestly.
+- `internal/tools/registry.go` — register the tool by adding it to the appropriate `CoreToolsScoped` variant (read-only, write, shell, network, or full). The factory functions decide which tool set a context gets.
+- `internal/tools/<name>_test.go` — table-driven test covering the happy path, each error path declared in the schema, and one permission-boundary case.
+
+Pattern to follow: copy `internal/tools/read_file.go` end-to-end. It demonstrates the `Tool` interface, the schema pattern, and the test layout.
+
+What NOT to do:
+
+- Do not call `os/exec` directly. The bash tool is the only path; everything else routes through `mvdan.cc/sh/v3` indirectly or uses Go stdlib.
+- Do not mutate `m.transcript` from inside a tool. Tools return `Result`; the agent loop appends to the transcript.
+- Do not skip `Safety`. Every tool must declare `SideEffect` and `Permission`.
+- Do not add new top-level deps. If a tool needs a library, justify it in the PR body.
+
+Verification:
+
+```
+go test ./internal/tools/ -run Test<Name> -v
+go vet ./internal/tools/
+```
+
+### Mode 3 — Add a provider
+
+Touch files:
+
+- `internal/providers/<name>/` — new subdir. Mirror `internal/providers/openai/` (factory wiring, request types, response mapping, image / tool-call handling, tests).
+- `internal/providers/factory.go` — register the new provider in the factory switch.
+- `internal/providercatalog/catalog.go` — add a `Descriptor` entry (ID, display name, default base URL, auth env vars, default model, capabilities).
+- `internal/cli/...` — only if the provider needs a new flag. Mirror existing flags before adding new ones.
+
+Pattern to follow: copy `internal/providers/openai/`. It has factory wiring, request shaping, content-part conversion, image blocks, and tests for every code path.
+
+What NOT to do:
+
+- Do not skip the image / vision path. Even if your first model doesn't support vision, the provider must handle `zeroruntime.ImageBlock` correctly (Anthropic `image` block, OpenAI `image_url`, Gemini `inlineData`).
+- Do not invent your own HTTP client. Reuse the one in `internal/providers/openai/` or `internal/providerio/`.
+- Do not hardcode model IDs. They live in `internal/modelregistry/`.
+
+Verification:
+
+```
+go test ./internal/providers/<name>/ -v
+go test ./internal/providers/ -v
+go test ./internal/providercatalog/ -v
+```
+
+### Mode 4 — Add a model entry
+
+Touch files:
+
+- `internal/modelregistry/catalog.go` — extend `DefaultModelEntries()` with the new model. Fields: ID, Provider, DisplayName, ContextWindow, Capabilities (`vision`, `tool_call`, `reasoning`), ReasoningEfforts (if applicable), Cost.
+
+Pattern to follow: open `catalog.go`, find the existing entry for the same provider, copy the row, edit the values. Same shape, same fields.
+
+What NOT to do:
+
+- Do not invent capabilities. Set only the ones the model actually supports. If unsure, leave the capability unset.
+- Do not add cost data you cannot cite. If you don't have a source, leave the cost fields zero and note it in the PR.
+
+Verification:
+
+```
+go test ./internal/modelregistry/ -v
+go test ./internal/tui/ -run TestModel -v
+```
+
+### Mode 5 — Add a specialist
+
+Touch files:
+
+- `internal/specialist/<name>.go` — implement the specialist. Read `internal/specialist/builtin.go` for the interface and `runtime.go` for the execution model.
+- `internal/specialist/registry.go` — register the specialist. Update the routing table so the main agent knows when to dispatch to it.
+
+Pattern to follow: copy `internal/specialist/exec.go` (or another existing specialist). The shape is consistent.
+
+What NOT to do:
+
+- Do not give a specialist access to tools the main agent doesn't. Specialists have their own whitelist.
+- Do not let a specialist call another specialist. One level of dispatch only.
+- Do not register a specialist without a routing rule. Routing without a rule is unreachable code.
+
+Verification:
+
+```
+go test ./internal/specialist/ -v
+go test ./internal/agent/ -v
+```
+
+### Mode 6 — Add a sandbox rule
+
+Touch files:
+
+- `internal/sandbox/risk.go` — add a pattern to the appropriate risk bucket (`destructive`, `destructive_catastrophic`, `network`, `credential`, etc.).
+- `internal/sandbox/engine.go` — only if the rule needs a new decision branch.
+- `internal/sandbox/risk_hardening_test.go` (or a sibling test file) — write a failing test FIRST that exercises the new pattern.
+
+Pattern to follow: read `risk.go` to see the existing pattern classification. The `add()` helper takes `(pattern, RiskLevel)`. New rules sit alongside their category.
+
+What NOT to do:
+
+- Do not weaken an existing rule. If you find a false positive, write a more specific pattern that excludes the safe case rather than removing the dangerous one.
+- Do not add a rule without a test. Sandbox regressions are silent and dangerous.
+- Do not skip `requestPaths` checks. When a command takes paths, the sandbox must validate them against the workspace + grant scope.
+
+Verification:
+
+```
+go test ./internal/sandbox/ -v
+go test ./internal/sandbox/ -run TestRisk -v
+```
+
+### Mode 7 — Modify the TUI
+
+Touch files:
+
+- `internal/tui/model.go` — state only. Add fields, add cases to `Update()`, add dispatch logic. Never apply lipgloss styles here.
+- `internal/tui/view.go` — pure render. Read from `model`, render to styled strings. Every style application lives here or in a `render*` helper.
+- `internal/tui/<feature>.go` — split when the feature is large. Look at the existing per-feature files (`picker.go`, `session.go`, `transcript_body.go`, etc.) for the convention.
+- `internal/tui/theme.go` — only if you need a new color or border. Add a named token with a hex value; never inline a hex elsewhere.
+
+Pattern to follow: open `model.go` and `view.go` side-by-side. Find the feature you're extending. The state mutation lives in `model.go`; the renderer lives in `view.go`. Tests live in `*_test.go` next to each.
+
+What NOT to do:
+
+- Do not apply lipgloss styles from `model.go`.
+- Do not store styled strings in the model. Store raw values; render at draw time.
+- Do not bypass `m.transcript`. Every visible row goes through `appendTranscriptRow`.
+- Do not add a hex color literal anywhere except `theme.go`.
+
+Verification:
+
+```
+gofmt -l internal/tui/
+go vet ./internal/tui/
+go test ./internal/tui/ -count=1
+```
+
+### Mode 8 — Debug a failing test
+
+Steps:
+
+1. Run narrow: `go test ./internal/<pkg>/ -run Test<Name> -v -count=1`. Read the failure verbatim — the assertion message is the most reliable signal.
+2. Read the test. The test is the contract. Do not rewrite the test to match broken behavior.
+3. Read the production code under test. Find the divergence between what the test expects and what the code does.
+4. Fix the production code. If the production code is right and the test was wrong, fix the test — but only after proving the production behavior is correct.
+5. Run narrow again. Then run the package. Then run the adjacent packages. Then run `go test ./...` to catch regressions.
+
+What NOT to do:
+
+- Do not `t.Skip()` to make a test pass. Skip with a TODO comment and a linked issue at most.
+- Do not delete a failing test without understanding why it was added.
+- Do not change a test's expected value without a commit message explaining why.
+- Do not modify `time.Now()` or any clock source to make a timing-sensitive test pass.
+
+Verification:
+
+```
+go test ./internal/<pkg>/ -run Test<Name> -v -count=1
+go test ./internal/<pkg>/ -count=1
+go test ./...
+```
+
+### Mode 9 — Cut a release
+
+Touch files:
+
+- `cmd/zero-release` only. No manual `git tag`. No manual binary upload. No edits to `CHANGELOG.md` by hand.
+
+Pattern to follow: run `go run ./cmd/zero-release build`, then `go run ./cmd/zero-release smoke`, then `go run ./cmd/zero-release package`, then `go run ./cmd/zero-release verify`. The release tooling is the contract.
+
+What NOT to do:
+
+- Do not push a tag by hand. The release tooling owns tag creation.
+- Do not skip `smoke`. If smoke fails, the release fails.
+- Do not edit `CHANGELOG.md` manually. The release tooling generates it from `git log` since the previous tag.
+- Do not bypass `verify`. Verification is the last gate.
+
+Verification:
+
+```
+go run ./cmd/zero-release build
+go run ./cmd/zero-release smoke
+go run ./cmd/zero-release package
+go run ./cmd/zero-release verify
+```
+
+### Mode 10 — Run a security or quality audit
+
+Touch files (read-only by default; edits only after explicit user approval):
+
+- `internal/sandbox/` — destructive-command classification in `risk.go`, decision logic in `engine.go`, path allow/deny in `paths.go` and `pathlists.go`. Audit coverage: do destructive paths actually get caught? Are grant scopes respected? Are `..` traversals blocked?
+- `internal/secrets/` — env handling. Audit: are secrets redacted in logs? Are `os.Getenv` calls going through the keyring when configured?
+- `internal/redaction/` — output redaction. Audit: is the redaction list current? Are there new tool outputs that need redaction entries?
+- `internal/providers/` — provider auth. Audit: are API keys read from env, never persisted? Are provider adapters validating their inputs?
+- `internal/mcp/` — MCP server trust. Audit: are MCP server outputs treated as data, never as instructions? Is the schema validated?
+- `internal/hooks/` — pre/post command hooks. Audit: do hooks have a way to abort? Is the abort path tested?
+- `docs/audit/` — read the most recent `*-deep-audit*.md` and `*-reverification.md` to see what's already been reviewed. Do not re-audit a category already covered.
+
+Pattern to follow: pick one subsystem per audit pass. Read the code, run the existing tests, write a one-page report naming each finding with a `file:line` anchor and an exploitability classification (`exploitable | plausible | theoretical`).
+
+What NOT to do:
+
+- Do not audit and edit in the same pass. Audit first, get user sign-off, then fix.
+- Do not propose fixes that disable a security control to silence a false positive. Tighten the rule instead.
+- Do not skip the audit because a recent audit covered the area. Confirm the diff since the last audit is empty.
+- Do not write findings without a `file:line` anchor. Vague findings get deleted.
+
+Verification:
+
+```
+go test ./internal/sandbox/ -v
+go test ./internal/secrets/ -v
+go test ./internal/redaction/ -v
+go test ./internal/mcp/ -v
+```
+
+## 4. Hard rules across all modes
+
+- Never run `rm -rf`, `git reset --hard`, or force-push without an explicit user message.
+- Never edit a file you have not read in full first.
+- Never widen `Permission` from `prompt` to `allow` for a tool without a test that proves the wider permission is safe.
+- Never delete a test. The test is a contract.
+- Never bypass `go vet` or `gofmt` with a `// nolint:` comment unless the PR body explains why.
+- Never commit secrets, even temporarily. If a secret lands in a commit, revert the commit and rotate the secret.

docs/oauth-subscriptions.md

@@ -0,0 +1,184 @@
+# OAuth logins & using ChatGPT / Claude subscriptions
+
+Zero supports two distinct things people mean by "log in with OAuth":
+
+1. **OAuth login for a provider/gateway** that issues a *standard* bearer token —
+   fully built in (`zero auth login …`). Zero attaches the token to model calls
+   automatically.
+2. **Using a ChatGPT or Claude *subscription*** (Plus / Pro / Max) instead of a
+   pay-per-token API key — only possible through a **local proxy**, for the
+   reasons documented below. Zero ships a convenience preset and this recipe.
+
+---
+
+## 1. OAuth login for a provider or gateway (built in)
+
+For any OAuth 2.0 / OIDC provider that returns a normal access token usable as
+`Authorization: Bearer …` on its API, configure it with `ZERO_OAUTH_<NAME>_*`
+env vars and log in:
+
+```sh
+export ZERO_OAUTH_ACME_CLIENT_ID=…
+export ZERO_OAUTH_ACME_AUTHORIZE_URL=https://acme.example/oauth/authorize
+export ZERO_OAUTH_ACME_TOKEN_URL=https://acme.example/oauth/token
+export ZERO_OAUTH_ACME_SCOPES="openid profile"
+zero auth login acme            # browser (loopback); --device for headless
+zero auth status
+```
+
+When a login exists for a provider, the **OpenAI and Anthropic** providers send
+`Authorization: Bearer <fresh-token>` (auto-refreshed; one refresh-and-retry on a
+`401`) instead of the API key. With no login they use the API key exactly as
+before. Tokens are stored 0600 (or the OS keyring with
+`ZERO_OAUTH_STORAGE=keyring`) and never logged. See `zero auth --help`.
+
+### In the setup wizard (`/provider`)
+
+Running `/provider` opens a **"How do you want to connect?"** chooser:
+
+```text
+❯ Sign in with OAuth                 One-click browser login (OpenRouter, xAI)
+  Paste an API key / browse providers  Any of 20+ providers, local, or a proxy
+```
+
+Pick **Sign in with OAuth** → the list of providers that do real OAuth → choose one:
+
+```text
+❯ OpenRouter    browser sign-in · creates a key
+  xAI (Grok)    browser or device code
+```
+
+- **OpenRouter / xAI** are real OAuth: your browser opens to approve → done (no
+  key to paste). OpenRouter mints a key; xAI stores a refreshable token. The same
+  chooser appears in first-run onboarding. (xAI uses an opt-in preset — set
+  `ZERO_OAUTH_ALLOW_PRESETS=1` or your own `ZERO_OAUTH_XAI_*`; see below.)
+- **Device code (headless / SSH):** for a provider that supports it (xAI), press
+  **d** on the list to get a code to enter on another device instead of opening a
+  browser. On an SSH session or headless Linux box (no `DISPLAY`) device code is
+  used automatically; set `ZERO_OAUTH_DEVICE=1` to force it anywhere. The CLI
+  equivalent is `zero auth login xai --device`.
+- **ChatGPT / Claude are intentionally not in this list** — they can't do in-app
+  OAuth (see §2). Use *Paste an API key / browse providers* + a local proxy
+  (`chatgpt-proxy` / `custom-anthropic-compatible`), as described below.
+
+### Built-in OAuth providers
+
+- **OpenRouter (no env needed)** — `zero auth openrouter` opens a browser, you
+  approve, and it **mints an OpenRouter API key** (public PKCE flow, no client_id).
+  In the interactive setup wizard, pick **OpenRouter** and press **ctrl+o** at the
+  key step to do the same inline ("Log in with OAuth"). The minted key is saved to
+  the provider profile and used normally.
+- **xAI (Grok) — opt-in preset** — xAI's flow needs an OAuth `client_id`. Zero
+  ships a built-in preset for the public Grok-CLI client, but to keep third-party
+  client identities out of the default credential path it is **off by default**.
+  Enable it with `export ZERO_OAUTH_ALLOW_PRESETS=1`, then `zero auth login xai`
+  (browser, or `--device` for headless) works one-click; the token is used directly
+  on `api.x.ai/v1`. Without the opt-in, set `ZERO_OAUTH_XAI_CLIENT_ID` (and
+  endpoints, or an issuer) yourself via `ZERO_OAUTH_XAI_*`. Either way the preset is
+  fully overridable by `ZERO_OAUTH_XAI_*` (env wins), and it requires a
+  SuperGrok / X Premium+ subscription; the client_id is an undocumented public
+  Grok-CLI client that may change without notice.
+
+Any field of a preset is overridable via `ZERO_OAUTH_<NAME>_*`. For a fully custom
+OAuth/OIDC provider, set those env vars (see `zero auth --help`) and
+`zero auth login <name>`.
+
+---
+
+## 2. ChatGPT / Claude subscriptions — why a proxy is required
+
+We researched this carefully. As of mid-2026, a **subscription** OAuth token does
+**not** work as a drop-in bearer against the standard APIs:
+
+- **OpenAI (ChatGPT):** a "Sign in with ChatGPT" token only works against
+  ChatGPT's own backend (`chatgpt.com/backend-api/codex/responses`, the Responses
+  API), **not** `api.openai.com`. That backend is **Cloudflare bot-protected** —
+  non-browser / headless clients get `cf-mitigated: challenge` → `403`. It also
+  requires mimicking the official Codex client (originator + account-id header).
+- **Anthropic (Claude):** the Messages API **rejects** subscription OAuth tokens
+  for third-party use unless the request spoofs the Claude Code identity
+  (`anthropic-beta: oauth-2025-04-20`, `claude-cli` UA, and a verbatim
+  *"You are Claude Code…"* system prompt) — and **even then** tool-using requests
+  on Max plans are routed to a disabled billing lane and `400`. Anthropic's policy
+  **prohibits** subscription-token use outside Claude Code / claude.ai, and the
+  timeline hardened through 2026: a **Feb 19 2026** docs update spelled out that
+  Free/Pro/Max OAuth tokens may not be used in third-party tools or the Agent SDK,
+  then on **April 4 2026** enforcement landed and subscription OAuth tokens
+  **stopped working in third-party harnesses** (starting with OpenClaw, then the
+  rest). As of mid-2026 the only supported ways to drive Claude from a third-party
+  tool are a standard **API key** or pay-as-you-go **"Extra Usage"** billing —
+  both per-token, not the flat subscription. The request to allow subscription use
+  (claude-code #37205) was closed *"not planned."*
+
+So Zero does **not** call those backends directly or spoof those clients — that
+would be fragile, account-risky, and (for Anthropic) against the vendor's terms.
+The robust, supported pattern is a **local proxy** that holds your subscription
+session and exposes a clean OpenAI- or Anthropic-compatible endpoint on
+`127.0.0.1`. The proxy absorbs the Cloudflare / client-spoofing surface; Zero
+just points at it.
+
+### ChatGPT via a local proxy
+
+Run a local ChatGPT OAuth proxy that exposes an OpenAI-compatible endpoint (these
+typically listen on `127.0.0.1:10531/v1`). Then use the built-in **`chatgpt-proxy`**
+preset (no API key — the proxy authenticates):
+
+```jsonc
+// ~/.config/zero/config.json (or ./.zero/config.json)
+{
+  "activeProvider": "chatgpt",
+  "providers": [
+    {
+      "name": "chatgpt",
+      "catalogID": "chatgpt-proxy",     // OpenAI-compatible, local, no key
+      "baseURL": "http://localhost:10531/v1", // override for your proxy's port
+      "model": "gpt-5"                   // whatever model your proxy serves
+    }
+  ]
+}
+```
+
+```sh
+zero exec --prompt "say hi"   # routes through the proxy → your ChatGPT plan
+```
+
+### Claude via a local proxy
+
+There is no single canonical Claude OAuth-proxy port, so use the generic
+**`custom-anthropic-compatible`** entry pointed at your proxy's Anthropic-compatible
+endpoint:
+
+```jsonc
+{
+  "activeProvider": "claude",
+  "providers": [
+    {
+      "name": "claude",
+      "catalogID": "custom-anthropic-compatible",
+      "baseURL": "http://localhost:<port>",  // your Claude proxy
+      "apiKey": "unused-by-proxy",
+      "model": "claude-sonnet-4.5"
+    }
+  ]
+}
+```
+
+---
+
+## 3. Supported alternatives (no proxy)
+
+- **API key (recommended, simplest):** set `OPENAI_API_KEY` / `ANTHROPIC_API_KEY`
+  (or per-profile `apiKey`) and use the `openai` / `anthropic` catalog providers.
+  Bills as API usage.
+- **Anthropic subscription automation, sanctioned:** spawn the real `claude` CLI
+  (e.g. `claude -p …`) as a subprocess — the only path Anthropic recognizes as a
+  first-class subscription session.
+
+---
+
+## Notes
+
+- The `chatgpt-proxy` base URL / port and model are defaults you override for your
+  setup; they are not an endorsement of any specific proxy implementation.
+- Subscription-via-proxy depends on third-party tools and undocumented vendor
+  backends; it can break without notice. The API-key path is the stable one.

go.mod

@@ -1,37 +1,36 @@
 module github.com/Gitlawb/zero
 
-go 1.24.2
+go 1.25.0
 
 toolchain go1.26.4
 
 require (
-	github.com/charmbracelet/bubbles v1.0.0
-	github.com/charmbracelet/bubbletea v1.3.10
-	github.com/charmbracelet/lipgloss v1.1.1-0.20250404203927-76690c660834
-	github.com/charmbracelet/x/ansi v0.11.6
+	charm.land/bubbles/v2 v2.1.0
+	charm.land/bubbletea/v2 v2.0.7
+	charm.land/lipgloss/v2 v2.0.4
+	github.com/atotto/clipboard v0.1.4
+	github.com/charmbracelet/colorprofile v0.4.3
+	github.com/charmbracelet/x/ansi v0.11.7
 	github.com/ledongthuc/pdf v0.0.0-20250511090121-5959a4027728
-	golang.org/x/sys v0.38.0
-	mvdan.cc/sh/v3 v3.11.0
+	golang.org/x/sys v0.46.0
+	mvdan.cc/sh/v3 v3.13.1
 )
 
 require (
-	github.com/atotto/clipboard v0.1.4 // indirect
-	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
-	github.com/charmbracelet/colorprofile v0.4.1 // indirect
-	github.com/charmbracelet/x/cellbuf v0.0.15 // indirect
+	github.com/charmbracelet/ultraviolet v0.0.0-20260615092913-2399af76d5b1 // indirect
+	github.com/charmbracelet/x/exp/golden v0.0.0-20260615092313-b57e5e6d29bb // indirect
 	github.com/charmbracelet/x/term v0.2.2 // indirect
-	github.com/clipperhouse/displaywidth v0.9.0 // indirect
-	github.com/clipperhouse/stringish v0.1.1 // indirect
-	github.com/clipperhouse/uax29/v2 v2.5.0 // indirect
-	github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f // indirect
-	github.com/lucasb-eyer/go-colorful v1.3.0 // indirect
-	github.com/mattn/go-isatty v0.0.20 // indirect
-	github.com/mattn/go-localereader v0.0.1 // indirect
-	github.com/mattn/go-runewidth v0.0.19 // indirect
-	github.com/muesli/ansi v0.0.0-20230316100256-276c6243b2f6 // indirect
+	github.com/charmbracelet/x/termios v0.1.1 // indirect
+	github.com/charmbracelet/x/windows v0.2.2 // indirect
+	github.com/clipperhouse/displaywidth v0.11.0 // indirect
+	github.com/clipperhouse/uax29/v2 v2.7.0 // indirect
+	github.com/go-quicktest/qt v1.102.0 // indirect
+	github.com/lucasb-eyer/go-colorful v1.4.0 // indirect
+	github.com/mattn/go-runewidth v0.0.24 // indirect
 	github.com/muesli/cancelreader v0.2.2 // indirect
-	github.com/muesli/termenv v0.16.0 // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
+	github.com/rogpeppe/go-internal v1.15.0 // indirect
 	github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e // indirect
-	golang.org/x/text v0.30.0 // indirect
+	golang.org/x/exp v0.0.0-20260611194520-c48552f49976 // indirect
+	golang.org/x/sync v0.21.0 // indirect
 )

go.sum

@@ -1,31 +1,33 @@
+charm.land/bubbles/v2 v2.1.0 h1:YSnNh5cPYlYjPxRrzs5VEn3vwhtEn3jVGRBT3M7/I0g=
+charm.land/bubbles/v2 v2.1.0/go.mod h1:l97h4hym2hvWBVfmJDtrEHHCtkIKeTEb3TTJ4ZOB3wY=
+charm.land/bubbletea/v2 v2.0.7 h1:7qw2tTAVar7m7klOPBYfTB0mniv/RuexsYwMRNxSeL0=
+charm.land/bubbletea/v2 v2.0.7/go.mod h1:DGW2q8gvzHnOpMpZTORs0aySVHCox5C+2Svk0fci1qs=
+charm.land/lipgloss/v2 v2.0.4 h1:lcPeVtcp23SNra7lHy8iYE4UC2aIipVQ47sbGyyxR5Q=
+charm.land/lipgloss/v2 v2.0.4/go.mod h1:0653x8epbZSzdDfO/XPS1a/uYPOBeSsCssOpJOqDzik=
 github.com/atotto/clipboard v0.1.4 h1:EH0zSVneZPSuFR11BlR9YppQTVDbh5+16AmcJi4g1z4=
 github.com/atotto/clipboard v0.1.4/go.mod h1:ZY9tmq7sm5xIbd9bOK4onWV4S6X0u6GY7Vn0Yu86PYI=
-github.com/aymanbagabas/go-osc52/v2 v2.0.1 h1:HwpRHbFMcZLEVr42D4p7XBqjyuxQH5SMiErDT4WkJ2k=
-github.com/aymanbagabas/go-osc52/v2 v2.0.1/go.mod h1:uYgXzlJ7ZpABp8OJ+exZzJJhRNQ2ASbcXHWsFqH8hp8=
-github.com/charmbracelet/bubbles v1.0.0 h1:12J8/ak/uCZEMQ6KU7pcfwceyjLlWsDLAxB5fXonfvc=
-github.com/charmbracelet/bubbles v1.0.0/go.mod h1:9d/Zd5GdnauMI5ivUIVisuEm3ave1XwXtD1ckyV6r3E=
-github.com/charmbracelet/bubbletea v1.3.10 h1:otUDHWMMzQSB0Pkc87rm691KZ3SWa4KUlvF9nRvCICw=
-github.com/charmbracelet/bubbletea v1.3.10/go.mod h1:ORQfo0fk8U+po9VaNvnV95UPWA1BitP1E0N6xJPlHr4=
-github.com/charmbracelet/colorprofile v0.4.1 h1:a1lO03qTrSIRaK8c3JRxJDZOvhvIeSco3ej+ngLk1kk=
-github.com/charmbracelet/colorprofile v0.4.1/go.mod h1:U1d9Dljmdf9DLegaJ0nGZNJvoXAhayhmidOdcBwAvKk=
-github.com/charmbracelet/lipgloss v1.1.1-0.20250404203927-76690c660834 h1:ZR7e0ro+SZZiIZD7msJyA+NjkCNNavuiPBLgerbOziE=
-github.com/charmbracelet/lipgloss v1.1.1-0.20250404203927-76690c660834/go.mod h1:aKC/t2arECF6rNOnaKaVU6y4t4ZeHQzqfxedE/VkVhA=
-github.com/charmbracelet/x/ansi v0.11.6 h1:GhV21SiDz/45W9AnV2R61xZMRri5NlLnl6CVF7ihZW8=
-github.com/charmbracelet/x/ansi v0.11.6/go.mod h1:2JNYLgQUsyqaiLovhU2Rv/pb8r6ydXKS3NIttu3VGZQ=
-github.com/charmbracelet/x/cellbuf v0.0.15 h1:ur3pZy0o6z/R7EylET877CBxaiE1Sp1GMxoFPAIztPI=
-github.com/charmbracelet/x/cellbuf v0.0.15/go.mod h1:J1YVbR7MUuEGIFPCaaZ96KDl5NoS0DAWkskup+mOY+Q=
+github.com/aymanbagabas/go-udiff v0.4.1 h1:OEIrQ8maEeDBXQDoGCbbTTXYJMYRCRO1fnodZ12Gv5o=
+github.com/aymanbagabas/go-udiff v0.4.1/go.mod h1:0L9PGwj20lrtmEMeyw4WKJ/TMyDtvAoK9bf2u/mNo3w=
+github.com/charmbracelet/colorprofile v0.4.3 h1:QPa1IWkYI+AOB+fE+mg/5/4HRMZcaXex9t5KX76i20Q=
+github.com/charmbracelet/colorprofile v0.4.3/go.mod h1:/zT4BhpD5aGFpqQQqw7a+VtHCzu+zrQtt1zhMt9mR4Q=
+github.com/charmbracelet/ultraviolet v0.0.0-20260615092913-2399af76d5b1 h1:4+r3uOJ69ueRBt4okgEfWZeXs3BD36HcDBmOIAUlETk=
+github.com/charmbracelet/ultraviolet v0.0.0-20260615092913-2399af76d5b1/go.mod h1:f/jRa757WUmaOZrbPspXymbg/GnbF+rwe4OLsG7aXYo=
+github.com/charmbracelet/x/ansi v0.11.7 h1:kzv1kJvjg2S3r9KHo8hDdHFQLEqn4RBCb39dAYC84jI=
+github.com/charmbracelet/x/ansi v0.11.7/go.mod h1:9qGpnAVYz+8ACONkZBUWPtL7lulP9No6p1epAihUZwQ=
+github.com/charmbracelet/x/exp/golden v0.0.0-20260615092313-b57e5e6d29bb h1:m1Uub9uM7meZ8ofVyeRfK7M/knCi3sF2gKn9kldVW0I=
+github.com/charmbracelet/x/exp/golden v0.0.0-20260615092313-b57e5e6d29bb/go.mod h1:6fMpcW6iwN/kX+xJ52eqVWsDiBTe0UJD24JLoHFe+P0=
 github.com/charmbracelet/x/term v0.2.2 h1:xVRT/S2ZcKdhhOuSP4t5cLi5o+JxklsoEObBSgfgZRk=
 github.com/charmbracelet/x/term v0.2.2/go.mod h1:kF8CY5RddLWrsgVwpw4kAa6TESp6EB5y3uxGLeCqzAI=
-github.com/clipperhouse/displaywidth v0.9.0 h1:Qb4KOhYwRiN3viMv1v/3cTBlz3AcAZX3+y9OLhMtAtA=
-github.com/clipperhouse/displaywidth v0.9.0/go.mod h1:aCAAqTlh4GIVkhQnJpbL0T/WfcrJXHcj8C0yjYcjOZA=
-github.com/clipperhouse/stringish v0.1.1 h1:+NSqMOr3GR6k1FdRhhnXrLfztGzuG+VuFDfatpWHKCs=
-github.com/clipperhouse/stringish v0.1.1/go.mod h1:v/WhFtE1q0ovMta2+m+UbpZ+2/HEXNWYXQgCt4hdOzA=
-github.com/clipperhouse/uax29/v2 v2.5.0 h1:x7T0T4eTHDONxFJsL94uKNKPHrclyFI0lm7+w94cO8U=
-github.com/clipperhouse/uax29/v2 v2.5.0/go.mod h1:Wn1g7MK6OoeDT0vL+Q0SQLDz/KpfsVRgg6W7ihQeh4g=
-github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f h1:Y/CXytFA4m6baUTXGLOoWe4PQhGxaX0KpnayAqC48p4=
-github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f/go.mod h1:vw97MGsxSvLiUE2X8qFplwetxpGLQrlU1Q9AUEIzCaM=
-github.com/go-quicktest/qt v1.101.0 h1:O1K29Txy5P2OK0dGo59b7b0LR6wKfIhttaAhHUyn7eI=
-github.com/go-quicktest/qt v1.101.0/go.mod h1:14Bz/f7NwaXPtdYEgzsx46kqSxVwTbzVZsDC26tQJow=
+github.com/charmbracelet/x/termios v0.1.1 h1:o3Q2bT8eqzGnGPOYheoYS8eEleT5ZVNYNy8JawjaNZY=
+github.com/charmbracelet/x/termios v0.1.1/go.mod h1:rB7fnv1TgOPOyyKRJ9o+AsTU/vK5WHJ2ivHeut/Pcwo=
+github.com/charmbracelet/x/windows v0.2.2 h1:IofanmuvaxnKHuV04sC0eBy/smG6kIKrWG2/jYn2GuM=
+github.com/charmbracelet/x/windows v0.2.2/go.mod h1:/8XtdKZzedat74NQFn0NGlGL4soHB0YQZrETF96h75k=
+github.com/clipperhouse/displaywidth v0.11.0 h1:lBc6kY44VFw+TDx4I8opi/EtL9m20WSEFgwIwO+UVM8=
+github.com/clipperhouse/displaywidth v0.11.0/go.mod h1:bkrFNkf81G8HyVqmKGxsPufD3JhNl3dSqnGhOoSD/o0=
+github.com/clipperhouse/uax29/v2 v2.7.0 h1:+gs4oBZ2gPfVrKPthwbMzWZDaAFPGYK72F0NJv2v7Vk=
+github.com/clipperhouse/uax29/v2 v2.7.0/go.mod h1:EFJ2TJMRUaplDxHKj1qAEhCtQPW2tJSwu5BF98AuoVM=
+github.com/go-quicktest/qt v1.102.0 h1:HSQxCeh5YZH3EL3W39ixjtyaEhcWSXQHtHnMBzSs474=
+github.com/go-quicktest/qt v1.102.0/go.mod h1:p4lGIVX+8Wa6ZPNDvqcxq36XpUDLh42FLetFU7odllI=
 github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
 github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
@@ -34,33 +36,23 @@ github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/ledongthuc/pdf v0.0.0-20250511090121-5959a4027728 h1:QwWKgMY28TAXaDl+ExRDqGQltzXqN/xypdKP86niVn8=
 github.com/ledongthuc/pdf v0.0.0-20250511090121-5959a4027728/go.mod h1:1fEHWurg7pvf5SG6XNE5Q8UZmOwex51Mkx3SLhrW5B4=
-github.com/lucasb-eyer/go-colorful v1.3.0 h1:2/yBRLdWBZKrf7gB40FoiKfAWYQ0lqNcbuQwVHXptag=
-github.com/lucasb-eyer/go-colorful v1.3.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
-github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
-github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
-github.com/mattn/go-localereader v0.0.1 h1:ygSAOl7ZXTx4RdPYinUpg6W99U8jWvWi9Ye2JC/oIi4=
-github.com/mattn/go-localereader v0.0.1/go.mod h1:8fBrzywKY7BI3czFoHkuzRoWE9C+EiG4R1k4Cjx5p88=
-github.com/mattn/go-runewidth v0.0.19 h1:v++JhqYnZuu5jSKrk9RbgF5v4CGUjqRfBm05byFGLdw=
-github.com/mattn/go-runewidth v0.0.19/go.mod h1:XBkDxAl56ILZc9knddidhrOlY5R/pDhgLpndooCuJAs=
-github.com/muesli/ansi v0.0.0-20230316100256-276c6243b2f6 h1:ZK8zHtRHOkbHy6Mmr5D264iyp3TiX5OmNcI5cIARiQI=
-github.com/muesli/ansi v0.0.0-20230316100256-276c6243b2f6/go.mod h1:CJlz5H+gyd6CUWT45Oy4q24RdLyn7Md9Vj2/ldJBSIo=
+github.com/lucasb-eyer/go-colorful v1.4.0 h1:UtrWVfLdarDgc44HcS7pYloGHJUjHV/4FwW4TvVgFr4=
+github.com/lucasb-eyer/go-colorful v1.4.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
+github.com/mattn/go-runewidth v0.0.24 h1:cpokDiIn0MGnhdHwuWnJBITySJ20QyNGnY2kR/ay2DU=
+github.com/mattn/go-runewidth v0.0.24/go.mod h1:XBkDxAl56ILZc9knddidhrOlY5R/pDhgLpndooCuJAs=
 github.com/muesli/cancelreader v0.2.2 h1:3I4Kt4BQjOR54NavqnDogx/MIoWBFa0StPA8ELUXHmA=
 github.com/muesli/cancelreader v0.2.2/go.mod h1:3XuTXfFS2VjM+HTLZY9Ak0l6eUKfijIfMUZ4EgX0QYo=
-github.com/muesli/termenv v0.16.0 h1:S5AlUN9dENB57rsbnkPyfdGuWIlkmzJjbFf0Tf5FWUc=
-github.com/muesli/termenv v0.16.0/go.mod h1:ZRfOIKPFDYQoDFF4Olj7/QJbW60Ol/kL1pU3VfY/Cnk=
 github.com/rivo/uniseg v0.4.7 h1:WUdvkW8uEhrYfLC4ZzdpI2ztxP1I582+49Oc5Mq64VQ=
 github.com/rivo/uniseg v0.4.7/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
-github.com/rogpeppe/go-internal v1.14.1 h1:UQB4HGPB6osV0SQTLymcB4TgvyWu6ZyliaW0tI/otEQ=
-github.com/rogpeppe/go-internal v1.14.1/go.mod h1:MaRKkUm5W0goXpeCfT7UZI6fk/L7L7so1lCWt35ZSgc=
+github.com/rogpeppe/go-internal v1.15.0 h1:D0RCU5rMAp+SpgkiNdrjfJ+LX4J1M32V2NeCY7EJ6hc=
+github.com/rogpeppe/go-internal v1.15.0/go.mod h1:DrUVZyrJU+txYW5/1kwtXQSMFio52ZOxX7yM1VHvnxs=
 github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e h1:JVG44RsyaB9T2KIHavMF/ppJZNG9ZpyihvCd0w101no=
 github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e/go.mod h1:RbqR21r5mrJuqunuUZ/Dhy/avygyECGrLceyNeo4LiM=
-golang.org/x/exp v0.0.0-20231006140011-7918f672742d h1:jtJma62tbqLibJ5sFQz8bKtEM8rJBtfilJ2qTU199MI=
-golang.org/x/exp v0.0.0-20231006140011-7918f672742d/go.mod h1:ldy0pHrwJyGW56pPQzzkH36rKxoZW1tw7ZJpeKx+hdo=
-golang.org/x/sys v0.0.0-20210809222454-d867a43fc93e/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
-golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
-golang.org/x/text v0.30.0 h1:yznKA/E9zq54KzlzBEAWn1NXSQ8DIp/NYMy88xJjl4k=
-golang.org/x/text v0.30.0/go.mod h1:yDdHFIX9t+tORqspjENWgzaCVXgk0yYnYuSZ8UzzBVM=
-mvdan.cc/sh/v3 v3.11.0 h1:q5h+XMDRfUGUedCqFFsjoFjrhwf2Mvtt1rkMvVz0blw=
-mvdan.cc/sh/v3 v3.11.0/go.mod h1:LRM+1NjoYCzuq/WZ6y44x14YNAI0NK7FLPeQSaFagGg=
+golang.org/x/exp v0.0.0-20260611194520-c48552f49976 h1:X8Hz2ImujgbmetVuW+w2YkyZChE3cBpZi2P158rTG9M=
+golang.org/x/exp v0.0.0-20260611194520-c48552f49976/go.mod h1:vnf4pv9iKZXY58sQE1L86zmNWJ4159e1RkcWiLCkeEY=
+golang.org/x/sync v0.21.0 h1:HLII4xRRTtCRkxYp4HNFF0Js/Og6q2i++KXbg0gHCwM=
+golang.org/x/sync v0.21.0/go.mod h1:9xrNwdLfx4jkKbNva9FpL6vEN7evnE43NNNJQ2LF3+0=
+golang.org/x/sys v0.46.0 h1:noSf2Fq6F8DBgS+LysIkx7rIExoNHJsxOAtPp4rthXw=
+golang.org/x/sys v0.46.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
+mvdan.cc/sh/v3 v3.13.1 h1:DP3TfgZhDkT7lerUdnp6PTGKyxxzz6T+cOlY/xEvfWk=
+mvdan.cc/sh/v3 v3.13.1/go.mod h1:lXJ8SexMvEVcHCoDvAGLZgFJ9Wsm2sulmoNEXGhYZD0=

internal/agent/guardrails.go

@@ -90,11 +90,48 @@ func toolFailureStopAnswer(toolName string, count int) string {
 		"Please check the request or adjust the tool arguments."
 }
 
+// The no-output stop answer is assembled from these fixed parts (only the turn
+// count varies). IsNoProgressStop matches all three so a legitimate message that
+// merely quotes the marker substring is not misclassified as a failed empty run.
+const (
+	noOutputStopPrefix = "Agent stopped after "
+	noOutputStopMarker = "with no output (no visible text and no tool calls)"
+	noOutputStopSuffix = "to avoid consuming tokens without making progress."
+)
+
 // noOutputStopAnswer is the final answer returned when the no-output guard
 // stops the run. The turn count is interpolated at the call site.
 func noOutputStopAnswer(turns int) string {
-	return "Agent stopped after " + strconv.Itoa(turns) +
-		" turns with no output (no visible text and no tool calls) to avoid consuming tokens without making progress."
+	return noOutputStopPrefix + strconv.Itoa(turns) + " turns " + noOutputStopMarker + " " + noOutputStopSuffix
+}
+
+// IsNoProgressStop reports whether content IS the no-output guardrail stop answer
+// (a run that produced no visible text and no tool calls). It matches the EXACT
+// structure noOutputStopAnswer emits — prefix + "<int> turns " + marker + " " +
+// suffix, where only the integer turn count varies — rather than just looking for
+// the three parts in order. A loose check (prefix && contains-marker && suffix)
+// would misclassify a genuine assistant/tool message that merely quotes the
+// marker amid other prose, which would wrongly hide a real session from /resume
+// and skip its title generation.
+func IsNoProgressStop(content string) bool {
+	trimmed := strings.TrimSpace(content)
+	if !strings.HasPrefix(trimmed, noOutputStopPrefix) {
+		return false
+	}
+	rest := trimmed[len(noOutputStopPrefix):]
+	const turnsSep = " turns "
+	sep := strings.Index(rest, turnsSep)
+	if sep < 0 {
+		return false
+	}
+	// The text between the prefix and " turns " must be exactly the bare integer
+	// count; anything else means this isn't the guard's own answer.
+	if _, err := strconv.Atoi(rest[:sep]); err != nil {
+		return false
+	}
+	// The marker must be immediately followed (one space) by the suffix and then
+	// end — no arbitrary text wedged in between.
+	return rest[sep+len(turnsSep):] == noOutputStopMarker+" "+noOutputStopSuffix
 }
 
 // Reminder markers are stable substrings used both to build the reminder text

internal/agent/no_progress_stop_test.go

@@ -0,0 +1,36 @@
+package agent
+
+import "testing"
+
+func TestIsNoProgressStopRequiresFullStructure(t *testing.T) {
+	// The actual guardrail answer (any turn count) is recognized.
+	for _, turns := range []int{1, 3, 12} {
+		if !IsNoProgressStop(noOutputStopAnswer(turns)) {
+			t.Fatalf("the real no-output stop answer (turns=%d) should be recognized", turns)
+		}
+	}
+
+	// A legitimate message that merely QUOTES the marker must NOT be classified as
+	// a no-progress stop — that would wrongly hide a real session from /resume.
+	rejected := []string{
+		`The previous run ended "with no output (no visible text and no tool calls)" so here is what I did instead.`,
+		"with no output (no visible text and no tool calls)", // bare marker, no prefix/suffix
+		"Agent stopped after 3 turns.",                       // prefix only
+		"to avoid consuming tokens without making progress.", // suffix only
+		"Here is your e-commerce site.",                      // unrelated
+		"",
+		// Hostile input: prefix + marker + suffix ALL present, but the marker is
+		// quoted mid-sentence rather than being the guard's own structured answer.
+		// A loose prefix/contains/suffix check misclassifies this.
+		`Agent stopped after 3 turns. The marker is "with no output (no visible text and no tool calls)" so here it is: to avoid consuming tokens without making progress.`,
+		// Arbitrary text wedged between the marker and the suffix.
+		"Agent stopped after 3 turns with no output (no visible text and no tool calls) and then some more text to avoid consuming tokens without making progress.",
+		// Non-integer "turn count" between the prefix and the marker.
+		"Agent stopped after several turns with no output (no visible text and no tool calls) to avoid consuming tokens without making progress.",
+	}
+	for _, content := range rejected {
+		if IsNoProgressStop(content) {
+			t.Fatalf("content must not be classified as a no-progress stop: %q", content)
+		}
+	}
+}

internal/agent/system_prompt.md

@@ -71,6 +71,17 @@ work.
   managers). It is not a substitute for the file tools.
 - Treat tool output as ground truth. If a command fails, read the error, form a
   hypothesis, and address the root cause; do not retry the same call blindly.
+- When a web search or fetch tool is available, search the web before answering
+  about an external entity, product, library, model, company, version, or recent
+  release you do not recognize. Do not guess, and do not assume the most common
+  meaning of an ambiguous name — use the conversation's domain (this is an AI /
+  software tool) to disambiguate. If the first results look off-topic, refine the
+  query and search again before answering; never reply that you don't know without
+  searching first.
+- Do not web-search timeless facts, fundamentals, or anything answerable from the
+  workspace — read the code with the file tools instead. Keep queries short (a few
+  words), start broad then narrow, and scale the number of searches to the
+  question: one for a single fact, a few for a deeper answer.
 
 ## Permission and safety
 

internal/agent/system_prompt_test.go

@@ -19,6 +19,8 @@ func TestCoreSystemPromptIncludesCodingQualityRules(t *testing.T) {
 		"verify after edits",
 		"honor the active permission mode",
 		"avoid broad refactors",
+		"search the web before answering",
+		"do not recognize",
 		"final response",
 	} {
 		if !strings.Contains(prompt, want) {

internal/agenteval/suite.go

@@ -186,10 +186,6 @@ func validateFileList(taskPath string, field string, files []string, required bo
 	return problems
 }
 
-func validateExpectedChangedFiles(taskPath string, files []string) []string {
-	return validateFileList(taskPath, "expectedChangedFiles", files, true)
-}
-
 func validateStringList(taskPath string, field string, values []string) []string {
 	problems := []string{}
 	seen := map[string]int{}

internal/browser/open.go

@@ -0,0 +1,38 @@
+// Package browser opens a URL in the user's default web browser. It is used by
+// interactive flows (e.g. the provider setup wizard's OAuth login) that need to
+// hand the user off to a browser for authorization.
+package browser
+
+import (
+	"fmt"
+	"os/exec"
+	"runtime"
+)
+
+// OpenURL launches url in the default browser. It returns once the launcher
+// process has started (it does not wait for the browser to close). A failure to
+// start the launcher is returned so callers can fall back to printing the URL.
+func OpenURL(url string) error {
+	name, args := openCommand(runtime.GOOS, url)
+	cmd := exec.Command(name, args...)
+	if err := cmd.Start(); err != nil {
+		return fmt.Errorf("browser: open url: %w", err)
+	}
+	// Reap the short-lived launcher (open/xdg-open/rundll32 exit promptly) so it
+	// does not linger as a zombie; the browser window itself is independent.
+	go func() { _ = cmd.Wait() }()
+	return nil
+}
+
+// openCommand returns the launcher command + args for a platform. Split out as a
+// pure function so the per-OS choice is unit-testable without spawning anything.
+func openCommand(goos, url string) (string, []string) {
+	switch goos {
+	case "darwin":
+		return "open", []string{url}
+	case "windows":
+		return "rundll32", []string{"url.dll,FileProtocolHandler", url}
+	default: // linux and other unixes
+		return "xdg-open", []string{url}
+	}
+}

internal/browser/open_test.go

@@ -0,0 +1,27 @@
+package browser
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestOpenCommand(t *testing.T) {
+	cases := []struct {
+		goos string
+		name string
+		args []string
+	}{
+		{"darwin", "open", []string{"https://x.test"}},
+		{"linux", "xdg-open", []string{"https://x.test"}},
+		{"freebsd", "xdg-open", []string{"https://x.test"}},
+		{"windows", "rundll32", []string{"url.dll,FileProtocolHandler", "https://x.test"}},
+	}
+	for _, tc := range cases {
+		t.Run(tc.goos, func(t *testing.T) {
+			name, args := openCommand(tc.goos, "https://x.test")
+			if name != tc.name || !reflect.DeepEqual(args, tc.args) {
+				t.Fatalf("openCommand(%s) = %q %v, want %q %v", tc.goos, name, args, tc.name, tc.args)
+			}
+		})
+	}
+}

internal/cli/app.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"path/filepath"
 	"strings"
 	"time"
 
@@ -23,6 +24,7 @@ import (
 	"github.com/Gitlawb/zero/internal/sessions"
 	"github.com/Gitlawb/zero/internal/skills"
 	"github.com/Gitlawb/zero/internal/specialist"
+	"github.com/Gitlawb/zero/internal/swarm"
 	"github.com/Gitlawb/zero/internal/tools"
 	"github.com/Gitlawb/zero/internal/tui"
 	"github.com/Gitlawb/zero/internal/update"
@@ -103,7 +105,10 @@ func defaultAppDeps() appDeps {
 			return config.ResolveMCP(options)
 		},
 		newProvider: func(profile config.ProviderProfile) (zeroruntime.Provider, error) {
-			return providers.New(profile, providers.Options{UserAgent: userAgent()})
+			return providers.New(profile, providers.Options{
+				UserAgent:     userAgent(),
+				OAuthResolver: oauthResolverForProfile(profile),
+			})
 		},
 		probeProviderHealth: providerhealth.Probe,
 		newSessionStore: func() *sessions.Store {
@@ -240,6 +245,8 @@ func runWithDeps(args []string, stdout io.Writer, stderr io.Writer, deps appDeps
 	case "exec":
 		// Forward leading --add-dir occurrences so exec's own parser collects them.
 		return runExec(append(addDirFlagArgs(addDirs), args[1:]...), stdout, stderr, deps)
+	case "daemon":
+		return runDaemon(args[1:], stdout, stderr, deps)
 	case "config":
 		return runConfig(args[1:], stdout, stderr, deps)
 	case "models":
@@ -274,6 +281,8 @@ func runWithDeps(args []string, stdout io.Writer, stderr io.Writer, deps appDeps
 		return runHooks(args[1:], stdout, stderr, deps)
 	case "mcp":
 		return runMCP(args[1:], stdout, stderr, deps)
+	case "auth":
+		return runAuth(args[1:], stdout, stderr, deps)
 	case "sandbox":
 		return runSandbox(args[1:], stdout, stderr, deps)
 	case "update":
@@ -415,8 +424,26 @@ func runInteractiveTUIWithSetup(stderr io.Writer, deps appDeps, permissionMode a
 	if err != nil {
 		return writeAppError(stderr, "failed to resolve user config path: "+err.Error(), 1)
 	}
+	doctorUserConfigPath := ""
+	projectConfigPath := ""
+	if resolveOptions, optErr := config.DefaultResolveOptions(workspaceRoot); optErr == nil {
+		doctorUserConfigPath = resolveOptions.UserConfigPath
+		projectConfigPath = resolveOptions.ProjectConfigPath
+	}
 
 	needsSetup := setupRequired(resolved)
+	if needsSetup && !forceSetup {
+		// The active provider lacks a usable credential, but if another saved
+		// provider already has one, fall back to it instead of forcing onboarding
+		// again. Saved logins persist across launches; switch the active provider
+		// any time with `zero provider use <name>`. Onboarding only runs when no
+		// configured provider is usable (a genuinely fresh setup).
+		if usable, ok := firstUsableProvider(resolved.Providers); ok {
+			resolved.Provider = usable
+			resolved.ActiveProvider = usable.Name
+			needsSetup = false
+		}
+	}
 	setupVisible := forceSetup || needsSetup
 	configPath := ""
 	if setupVisible {
@@ -507,20 +534,24 @@ func runInteractiveTUIWithSetup(stderr io.Writer, deps appDeps, permissionMode a
 	})
 	lastKnownMCPConfig := mcpConfig
 	return deps.runTUI(context.Background(), tui.Options{
-		Cwd:                workspaceRoot,
-		UserConfigPath:     userConfigPath,
-		ProviderName:       resolved.Provider.Name,
-		ModelName:          resolved.Provider.Model,
-		ProviderProfile:    resolved.Provider,
-		FavoriteModels:     resolved.Preferences.FavoriteModels,
-		Provider:           provider,
-		NewProvider:        deps.newProvider,
-		Registry:           registry,
-		SessionStore:       deps.newSessionStore(),
-		SandboxStore:       sandboxStore,
-		MCPConfig:          mcpConfig,
-		MCPPermissionStore: mcpPermissionStore,
-		MCPTokenStore:      mcpTokenStore,
+		Cwd:                  workspaceRoot,
+		UserConfigPath:       userConfigPath,
+		DoctorUserConfigPath: doctorUserConfigPath,
+		ProjectConfigPath:    projectConfigPath,
+		ProviderName:         resolved.Provider.Name,
+		ModelName:            resolved.Provider.Model,
+		ProviderProfile:      resolved.Provider,
+		FavoriteModels:       resolved.Preferences.FavoriteModels,
+		Provider:             provider,
+		NewProvider:          deps.newProvider,
+		ProbeProviderHealth:  deps.probeProviderHealth,
+		UserAgent:            userAgent(),
+		Registry:             registry,
+		SessionStore:         deps.newSessionStore(),
+		SandboxStore:         sandboxStore,
+		MCPConfig:            mcpConfig,
+		MCPPermissionStore:   mcpPermissionStore,
+		MCPTokenStore:        mcpTokenStore,
 		MCPCommand: func(ctx context.Context, args []string) tui.MCPCommandResult {
 			if ctx == nil {
 				ctx = context.Background()
@@ -582,12 +613,37 @@ func newCoreRegistryScoped(workspaceRoot string, scope tools.PathScope) *tools.R
 	return registry
 }
 
-func registerSpecialistTools(registry *tools.Registry, workspaceRoot string) (*specialist.Runtime, error) {
+// agentToolRuntime bundles the specialist runtime with the swarm it backs so
+// their lifetimes (and shutdown) stay paired: registerSpecialistTools brings up
+// both, closeSpecialistRuntime tears down both.
+type agentToolRuntime struct {
+	specialist *specialist.Runtime
+	swarm      *swarm.Swarm
+}
+
+func registerSpecialistTools(registry *tools.Registry, workspaceRoot string) (*agentToolRuntime, error) {
 	paths, err := specialist.DefaultPaths(workspaceRoot)
 	if err != nil {
 		return nil, err
 	}
-	return specialist.RegisterTools(registry, specialist.Executor{Paths: paths})
+	executor := specialist.Executor{Paths: paths}
+	runtime, err := specialist.RegisterTools(registry, executor)
+	if err != nil {
+		return nil, err
+	}
+	// The swarm reuses the same specialist executor to launch each member, so
+	// every member runs under the orchestrator's sandbox + policy. Mailbox state
+	// lives under the workspace so its files fall within the sandbox write rules.
+	sw, err := swarm.New(swarm.Options{
+		BaseDir:  filepath.Join(workspaceRoot, ".zero", "swarm"),
+		Launcher: swarm.NewSpecialistLauncher(executor),
+	})
+	if err != nil {
+		runtime.Close()
+		return nil, err
+	}
+	swarm.RegisterTools(registry, sw)
+	return &agentToolRuntime{specialist: runtime, swarm: sw}, nil
 }
 
 func shouldRegisterExecSpecialistTools(options execOptions) bool {
@@ -609,12 +665,17 @@ func closeMCPRuntime(stderr io.Writer, runtime mcpToolRuntime) {
 	}
 }
 
-func closeSpecialistRuntime(stderr io.Writer, runtime *specialist.Runtime) {
+func closeSpecialistRuntime(stderr io.Writer, runtime *agentToolRuntime) {
 	if runtime == nil {
 		return
 	}
-	if err := runtime.Close(); err != nil {
-		_, _ = fmt.Fprintf(stderr, "[zero] specialist_cleanup_error: %s\n", err)
+	if runtime.swarm != nil {
+		runtime.swarm.Close()
+	}
+	if runtime.specialist != nil {
+		if err := runtime.specialist.Close(); err != nil {
+			_, _ = fmt.Fprintf(stderr, "[zero] specialist_cleanup_error: %s\n", err)
+		}
 	}
 }
 
@@ -637,6 +698,7 @@ Usage:
 
 Commands:
   exec       Run a one-shot prompt through the Go agent runtime
+  daemon     Manage the local background worker daemon (start/stop/status/run/attach)
   setup      Guide first-run provider setup
   config     Inspect resolved Go configuration without leaking secrets
   models     List Zero model registry entries
@@ -655,6 +717,7 @@ Commands:
   tools      Scaffold and list local Zero plugin-tools
   hooks      Inspect Zero hook configuration
   mcp        Manage MCP backend settings
+  auth       Log in to model providers via OAuth
   sandbox    Inspect sandbox policy and persistent grants
   update     Check for Zero CLI updates
   worktrees  Prepare isolated git worktrees

internal/cli/app_test.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"testing"
 	"time"
@@ -59,10 +60,38 @@ func TestRunPrintsHelp(t *testing.T) {
 	}
 }
 
+func setCLIUserConfigRoot(t *testing.T) string {
+	t.Helper()
+
+	root := t.TempDir()
+	switch runtime.GOOS {
+	case "windows":
+		t.Setenv("APPDATA", root)
+	case "darwin":
+		t.Setenv("HOME", root)
+	default:
+		t.Setenv("XDG_CONFIG_HOME", root)
+	}
+
+	configRoot, err := os.UserConfigDir()
+	if err != nil {
+		t.Fatalf("UserConfigDir() error = %v", err)
+	}
+	return configRoot
+}
+
 func TestRunNoArgsLaunchesSetupTUIWithNilProviderWhenNoProviderConfigured(t *testing.T) {
 	var stdout bytes.Buffer
 	var stderr bytes.Buffer
 	cwd := t.TempDir()
+	setCLIUserConfigRoot(t)
+	projectConfigPath := filepath.Join(cwd, ".zero", "config.json")
+	if err := os.MkdirAll(filepath.Dir(projectConfigPath), 0o700); err != nil {
+		t.Fatalf("create project config parent: %v", err)
+	}
+	if err := os.WriteFile(projectConfigPath, []byte("{}"), 0o600); err != nil {
+		t.Fatalf("write project config: %v", err)
+	}
 	userConfigPath := filepath.Join(t.TempDir(), "zero", "config.json")
 	var launchedOptions tui.Options
 
@@ -104,6 +133,12 @@ func TestRunNoArgsLaunchesSetupTUIWithNilProviderWhenNoProviderConfigured(t *tes
 	if launchedOptions.UserConfigPath != userConfigPath {
 		t.Fatalf("UserConfigPath = %q, want %q", launchedOptions.UserConfigPath, userConfigPath)
 	}
+	if launchedOptions.DoctorUserConfigPath != "" {
+		t.Fatalf("DoctorUserConfigPath = %q, want empty for missing user config", launchedOptions.DoctorUserConfigPath)
+	}
+	if launchedOptions.ProjectConfigPath != projectConfigPath {
+		t.Fatalf("ProjectConfigPath = %q, want %q", launchedOptions.ProjectConfigPath, projectConfigPath)
+	}
 	if launchedOptions.Provider != nil {
 		t.Fatalf("Provider = %#v, want nil", launchedOptions.Provider)
 	}

internal/cli/auth.go

@@ -0,0 +1,403 @@
+package cli
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/oauth"
+	"github.com/Gitlawb/zero/internal/provideroauth"
+	"github.com/Gitlawb/zero/internal/redaction"
+)
+
+// runAuth dispatches `zero auth <command>` for provider OAuth login. It is
+// additive and independent of `zero mcp oauth` (MCP server auth), which is
+// unchanged.
+func runAuth(args []string, stdout io.Writer, stderr io.Writer, deps appDeps) int {
+	if len(args) == 0 {
+		return writeExecUsageError(stderr, "auth subcommand required. Use `zero auth status`.")
+	}
+	if args[0] == "-h" || args[0] == "--help" || args[0] == "help" {
+		if err := writeAuthHelp(stdout); err != nil {
+			return exitCrash
+		}
+		return exitSuccess
+	}
+	switch args[0] {
+	case "login":
+		return runAuthLogin(args[1:], stdout, stderr, deps)
+	case "logout":
+		return runAuthLogout(args[1:], stdout, stderr, deps)
+	case "status":
+		return runAuthStatus(args[1:], stdout, stderr, deps)
+	case "refresh":
+		return runAuthRefresh(args[1:], stdout, stderr, deps)
+	case "openrouter":
+		return runAuthOpenRouter(args[1:], stdout, stderr, deps)
+	default:
+		return writeExecUsageError(stderr, fmt.Sprintf("unknown auth subcommand %q", args[0]))
+	}
+}
+
+// runAuthOpenRouter runs OpenRouter's browser PKCE login and prints the freshly
+// minted API key. Unlike `auth login` (which stores an OAuth bearer token),
+// OpenRouter's flow mints a normal API key; the setup wizard saves it to a
+// provider profile, while this command prints it for manual configuration.
+func runAuthOpenRouter(args []string, stdout io.Writer, stderr io.Writer, _ appDeps) int {
+	for _, a := range args {
+		if a == "-h" || a == "--help" || a == "help" {
+			_ = writeAuthHelp(stdout)
+			return exitSuccess
+		}
+	}
+	// openrouter takes no positional args or flags; reject the unexpected so a
+	// typo/unsupported flag fails fast instead of silently running the login.
+	if len(args) > 0 {
+		return writeExecUsageError(stderr, fmt.Sprintf("zero auth openrouter takes no arguments (got %q)", args[0]))
+	}
+	key, err := provideroauth.OpenRouterLogin(context.Background(), provideroauth.OpenRouterOptions{
+		Out:        stdout,
+		HTTPClient: &http.Client{Timeout: 30 * time.Second},
+		// ZERO_OPENROUTER_BASE_URL overrides the endpoint (self-hosted gateway or tests).
+		BaseURL: strings.TrimSpace(os.Getenv("ZERO_OPENROUTER_BASE_URL")),
+	})
+	if err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	if _, err := fmt.Fprintf(stdout, "\nOpenRouter login complete — new API key minted.\nUse it with zero, e.g.:\n  export OPENROUTER_API_KEY=%s\n(or add it to a provider profile with catalogID \"openrouter\").\n", key); err != nil {
+		return exitCrash
+	}
+	return exitSuccess
+}
+
+// authArgs is the parsed form of an auth subcommand's arguments.
+type authArgs struct {
+	positional []string
+	json       bool
+	device     bool
+	watch      bool
+	scopes     []string
+	help       bool
+}
+
+func parseAuthArgs(sub string, args []string) (authArgs, error) {
+	var parsed authArgs
+	addScope := func(scope string) error {
+		scope = strings.TrimSpace(scope)
+		if scope == "" {
+			return fmt.Errorf("--scope requires a non-empty value")
+		}
+		parsed.scopes = append(parsed.scopes, scope)
+		return nil
+	}
+	for i := 0; i < len(args); i++ {
+		arg := args[i]
+		switch {
+		case arg == "-h" || arg == "--help" || arg == "help":
+			parsed.help = true
+		case arg == "--json":
+			parsed.json = true
+		case arg == "--device":
+			parsed.device = true
+		case arg == "--watch":
+			parsed.watch = true
+		case arg == "--scope":
+			if i+1 >= len(args) {
+				return authArgs{}, fmt.Errorf("--scope requires a value")
+			}
+			i++
+			if err := addScope(args[i]); err != nil {
+				return authArgs{}, err
+			}
+		case strings.HasPrefix(arg, "--scope="):
+			if err := addScope(strings.TrimPrefix(arg, "--scope=")); err != nil {
+				return authArgs{}, err
+			}
+		case strings.HasPrefix(arg, "-"):
+			return authArgs{}, fmt.Errorf("unknown flag %q", arg)
+		default:
+			parsed.positional = append(parsed.positional, arg)
+		}
+	}
+	if parsed.help {
+		return parsed, nil // help short-circuits flag validation
+	}
+	if err := validateAuthFlags(sub, parsed); err != nil {
+		return authArgs{}, err
+	}
+	return parsed, nil
+}
+
+// validateAuthFlags rejects flags a subcommand does not accept, so an ambiguous
+// invocation fails fast instead of silently ignoring a flag.
+func validateAuthFlags(sub string, a authArgs) error {
+	allowed := map[string]map[string]bool{
+		"login":   {"device": true, "scope": true},
+		"logout":  {"json": true},
+		"status":  {"json": true},
+		"refresh": {"watch": true},
+	}[sub]
+	bad := func(name string) error { return fmt.Errorf("zero auth %s does not accept %s", sub, name) }
+	if a.json && !allowed["json"] {
+		return bad("--json")
+	}
+	if a.device && !allowed["device"] {
+		return bad("--device")
+	}
+	if a.watch && !allowed["watch"] {
+		return bad("--watch")
+	}
+	if len(a.scopes) > 0 && !allowed["scope"] {
+		return bad("--scope")
+	}
+	return nil
+}
+
+// newAuthManager builds an oauth.Manager backed by the file store, printing the
+// authorization URL / device code to stdout. The store path honors
+// ZERO_OAUTH_TOKENS_PATH (env), so callers/tests can redirect it. Setting
+// ZERO_OAUTH_STORAGE=encrypted-file selects the AES-256-GCM encrypted-at-rest
+// backend (a per-user secret is created beside the token file).
+func newAuthManager(deps appDeps, out io.Writer) (*oauth.Manager, error) {
+	// Validate ZERO_OAUTH_STORAGE up front: a mistyped value must fail fast rather
+	// than silently change the backend. Empty = default (plaintext 0600 file);
+	// "encrypted-file" = AES-256-GCM; "keyring" = the OS keyring.
+	storage := strings.ToLower(strings.TrimSpace(os.Getenv("ZERO_OAUTH_STORAGE")))
+	switch storage {
+	case "", "file", "encrypted-file", "keyring":
+	default:
+		return nil, fmt.Errorf("invalid ZERO_OAUTH_STORAGE %q (supported: file, encrypted-file, keyring)", storage)
+	}
+	store, err := oauth.NewStore(oauth.StoreOptions{
+		Now:     deps.now,
+		Storage: storage,
+	})
+	if err != nil {
+		return nil, err
+	}
+	return oauth.NewManager(oauth.ManagerOptions{
+		Store:      store,
+		HTTPClient: &http.Client{Timeout: 30 * time.Second},
+		Now:        deps.now,
+		Out:        out,
+		// The opener prints the URL so headless shells can copy it; the URL
+		// carries no token material. A real browser launch is intentionally not
+		// performed (the sandbox/headless contexts make printing the safer default).
+		OpenBrowser: func(string) error { return nil },
+	})
+}
+
+func runAuthLogin(args []string, stdout io.Writer, stderr io.Writer, deps appDeps) int {
+	parsed, err := parseAuthArgs("login", args)
+	if err != nil {
+		return writeExecUsageError(stderr, err.Error())
+	}
+	if parsed.help {
+		_ = writeAuthHelp(stdout)
+		return exitSuccess
+	}
+	if len(parsed.positional) != 1 {
+		return writeExecUsageError(stderr, "usage: zero auth login <provider> [--device] [--scope <scope>]")
+	}
+	manager, err := newAuthManager(deps, stdout)
+	if err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	status, err := manager.Login(context.Background(), oauth.LoginOptions{
+		Provider:    parsed.positional[0],
+		Device:      parsed.device,
+		ExtraScopes: parsed.scopes,
+	})
+	if err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	if _, err := fmt.Fprintf(stdout, "Logged in to %s.\n%s\n", parsed.positional[0], oauth.FormatStatuses([]oauth.Status{status})); err != nil {
+		return exitCrash
+	}
+	return exitSuccess
+}
+
+func runAuthLogout(args []string, stdout io.Writer, stderr io.Writer, deps appDeps) int {
+	parsed, err := parseAuthArgs("logout", args)
+	if err != nil {
+		return writeExecUsageError(stderr, err.Error())
+	}
+	if parsed.help {
+		_ = writeAuthHelp(stdout)
+		return exitSuccess
+	}
+	if len(parsed.positional) != 1 {
+		return writeExecUsageError(stderr, "usage: zero auth logout <provider>")
+	}
+	provider := parsed.positional[0]
+	manager, err := newAuthManager(deps, stdout)
+	if err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	removed, err := manager.Logout(provider)
+	if err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	if parsed.json {
+		payload := struct {
+			Provider string `json:"provider"`
+			Removed  bool   `json:"removed"`
+		}{Provider: provider, Removed: removed}
+		if err := writePrettyJSON(stdout, payload); err != nil {
+			return exitCrash
+		}
+		return exitSuccess
+	}
+	msg := fmt.Sprintf("No OAuth login stored for %s.\n", provider)
+	if removed {
+		msg = fmt.Sprintf("Logged out of %s.\n", provider)
+	}
+	if _, err := fmt.Fprint(stdout, msg); err != nil {
+		return exitCrash
+	}
+	return exitSuccess
+}
+
+func runAuthStatus(args []string, stdout io.Writer, stderr io.Writer, deps appDeps) int {
+	parsed, err := parseAuthArgs("status", args)
+	if err != nil {
+		return writeExecUsageError(stderr, err.Error())
+	}
+	if parsed.help {
+		_ = writeAuthHelp(stdout)
+		return exitSuccess
+	}
+	if len(parsed.positional) > 1 {
+		return writeExecUsageError(stderr, "usage: zero auth status [provider]")
+	}
+	manager, err := newAuthManager(deps, stdout)
+	if err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	statuses, err := manager.StatusAll()
+	if err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	if len(parsed.positional) == 1 {
+		statuses = filterAuthStatuses(statuses, parsed.positional[0])
+	}
+	if parsed.json {
+		payload := struct {
+			Logins []oauth.Status `json:"logins"`
+		}{Logins: statuses}
+		if err := writePrettyJSON(stdout, payload); err != nil {
+			return exitCrash
+		}
+		return exitSuccess
+	}
+	if _, err := fmt.Fprintln(stdout, oauth.FormatStatuses(statuses)); err != nil {
+		return exitCrash
+	}
+	return exitSuccess
+}
+
+func runAuthRefresh(args []string, stdout io.Writer, stderr io.Writer, deps appDeps) int {
+	parsed, err := parseAuthArgs("refresh", args)
+	if err != nil {
+		return writeExecUsageError(stderr, err.Error())
+	}
+	if parsed.help {
+		_ = writeAuthHelp(stdout)
+		return exitSuccess
+	}
+	if len(parsed.positional) != 1 {
+		return writeExecUsageError(stderr, "usage: zero auth refresh <provider>")
+	}
+	provider := parsed.positional[0]
+	manager, err := newAuthManager(deps, stdout)
+	if err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	key := oauth.ProviderKey(provider)
+	if parsed.watch {
+		return runAuthRefreshWatch(manager, key, provider, stdout, stderr)
+	}
+	if _, err := manager.Handle401(context.Background(), key); err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	if _, err := fmt.Fprintf(stdout, "Refreshed OAuth token for %s.\n", provider); err != nil {
+		return exitCrash
+	}
+	return exitSuccess
+}
+
+// runAuthRefreshWatch keeps a provider's token fresh in the foreground until
+// interrupted. This is the opt-in proactive-refresh scheduler surface (for a
+// long-running external process that reads the token file). It validates a
+// refreshable token exists first, then schedules refreshes before each expiry.
+func runAuthRefreshWatch(manager *oauth.Manager, key, provider string, stdout io.Writer, stderr io.Writer) int {
+	ctx, stop := signalContext()
+	defer stop()
+	// Validate (and refresh-if-needed) once up front so a missing/non-refreshable
+	// token fails fast instead of silently watching nothing.
+	if _, err := manager.GetFresh(ctx, key); err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	scheduler := oauth.NewRefreshScheduler()
+	scheduler.Start(ctx, manager, key)
+	defer scheduler.Stop()
+	if _, err := fmt.Fprintf(stdout, "Watching %s — refreshing before expiry. Press Ctrl+C to stop.\n", provider); err != nil {
+		return exitCrash
+	}
+	<-ctx.Done()
+	return exitSuccess
+}
+
+func filterAuthStatuses(statuses []oauth.Status, provider string) []oauth.Status {
+	want := oauth.ProviderKey(provider)
+	filtered := make([]oauth.Status, 0, 1)
+	for _, st := range statuses {
+		if st.Key == want {
+			filtered = append(filtered, st)
+		}
+	}
+	return filtered
+}
+
+func writeAuthHelp(w io.Writer) error {
+	_, err := fmt.Fprint(w, `Usage:
+  zero auth <command>
+
+Commands:
+  login <provider> [--device] [--scope <scope>]   Log in to a provider via OAuth
+  logout <provider>                               Delete a provider's stored login
+  status [provider]                               Show login presence/expiry (never the token)
+  refresh <provider> [--watch]                    Force a token refresh (--watch keeps it fresh)
+  openrouter                                      Log in to OpenRouter in the browser; mints an API key
+
+A provider is any OAuth 2.0 / OIDC server. "openrouter" ('zero auth openrouter')
+works out of the box. "xai" ('zero auth login xai') uses a built-in preset that is
+off by default — enable it with ZERO_OAUTH_ALLOW_PRESETS=1, or set the
+ZERO_OAUTH_XAI_* vars yourself. Any preset field is overridable via the env vars
+below. For a custom provider named <name>, set:
+  ZERO_OAUTH_<NAME>_CLIENT_ID       (required)
+  ZERO_OAUTH_<NAME>_CLIENT_SECRET   (optional)
+  ZERO_OAUTH_<NAME>_AUTHORIZE_URL   ZERO_OAUTH_<NAME>_TOKEN_URL
+  ZERO_OAUTH_<NAME>_DEVICE_URL      ZERO_OAUTH_<NAME>_ISSUER_URL (for discovery)
+  ZERO_OAUTH_<NAME>_SCOPES          ZERO_OAUTH_<NAME>_FLOW (loopback|device)
+Endpoint URLs must be https (loopback exempt).
+
+Storage: tokens are written 0600 under $XDG_CONFIG_HOME/zero (override with
+ZERO_OAUTH_TOKENS_PATH). Set ZERO_OAUTH_STORAGE=encrypted-file to encrypt them at
+rest with AES-256-GCM (a per-user secret beside the file), or
+ZERO_OAUTH_STORAGE=keyring to use the OS keyring (macOS Keychain / Linux
+secret-tool). MCP server tokens share the same store.
+
+Flags:
+      --device   Use the device-code flow (headless/SSH; no browser)
+      --scope    Add an OAuth scope (repeatable)
+      --watch    Keep the token fresh in the foreground (refresh only)
+      --json     Print result as JSON (status/logout)
+  -h, --help     Show this help
+`)
+	return err
+}

internal/cli/auth_test.go

@@ -0,0 +1,158 @@
+package cli
+
+import (
+	"bytes"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/Gitlawb/zero/internal/oauth"
+)
+
+// withAuthStore points the provider OAuth store at a temp file for the test.
+func withAuthStore(t *testing.T) string {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "oauth-tokens.json")
+	t.Setenv("ZERO_OAUTH_TOKENS_PATH", path)
+	return path
+}
+
+func TestRunAuthRejectsInvalidStorageMode(t *testing.T) {
+	withAuthStore(t)
+	// A mistyped value must fail fast, not silently fall back to plaintext while
+	// the user believes encryption is active.
+	t.Setenv("ZERO_OAUTH_STORAGE", "encryptd")
+	var stdout, stderr bytes.Buffer
+	if code := runWithDeps([]string{"auth", "status"}, &stdout, &stderr, appDeps{}); code == exitSuccess {
+		t.Fatalf("invalid ZERO_OAUTH_STORAGE should fail, got success; stdout=%q", stdout.String())
+	}
+	if !strings.Contains(stderr.String(), "ZERO_OAUTH_STORAGE") {
+		t.Fatalf("error should name the offending env var, stderr=%q", stderr.String())
+	}
+}
+
+func TestRunAuthStatusEmpty(t *testing.T) {
+	withAuthStore(t)
+	var stdout, stderr bytes.Buffer
+	if code := runWithDeps([]string{"auth", "status"}, &stdout, &stderr, appDeps{}); code != exitSuccess {
+		t.Fatalf("exit = %d stderr=%s", code, stderr.String())
+	}
+	if !strings.Contains(stdout.String(), "No OAuth provider logins are stored.") {
+		t.Fatalf("status output = %q", stdout.String())
+	}
+}
+
+func TestRunAuthStatusReportsLoginWithoutSecret(t *testing.T) {
+	path := withAuthStore(t)
+	store, err := oauth.NewStore(oauth.StoreOptions{FilePath: path})
+	if err != nil {
+		t.Fatalf("NewStore: %v", err)
+	}
+	if err := store.Save(oauth.ProviderKey("demo"), oauth.Token{
+		AccessToken: "super-secret", RefreshToken: "super-secret-rt", Account: "[email protected]",
+	}); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	var stdout, stderr bytes.Buffer
+	if code := runWithDeps([]string{"auth", "status"}, &stdout, &stderr, appDeps{}); code != exitSuccess {
+		t.Fatalf("exit = %d stderr=%s", code, stderr.String())
+	}
+	out := stdout.String()
+	if !strings.Contains(out, "demo") || !strings.Contains(out, "[email protected]") {
+		t.Fatalf("status should show provider + account: %q", out)
+	}
+	if strings.Contains(out, "super-secret") {
+		t.Fatalf("status leaked token material: %q", out)
+	}
+}
+
+func TestRunAuthLogoutNothing(t *testing.T) {
+	withAuthStore(t)
+	var stdout, stderr bytes.Buffer
+	if code := runWithDeps([]string{"auth", "logout", "demo"}, &stdout, &stderr, appDeps{}); code != exitSuccess {
+		t.Fatalf("exit = %d stderr=%s", code, stderr.String())
+	}
+	if !strings.Contains(stdout.String(), "No OAuth login stored for demo") {
+		t.Fatalf("logout output = %q", stdout.String())
+	}
+}
+
+func TestRunAuthLoginValidation(t *testing.T) {
+	withAuthStore(t)
+	var stdout, stderr bytes.Buffer
+	// Missing provider.
+	if code := runWithDeps([]string{"auth", "login"}, &stdout, &stderr, appDeps{}); code == exitSuccess {
+		t.Fatal("login with no provider should fail")
+	}
+	// --json is rejected for the interactive login.
+	stdout.Reset()
+	stderr.Reset()
+	if code := runWithDeps([]string{"auth", "login", "demo", "--json"}, &stdout, &stderr, appDeps{}); code == exitSuccess {
+		t.Fatal("login --json should be rejected")
+	}
+}
+
+func TestRunAuthLoginUnknownProvider(t *testing.T) {
+	withAuthStore(t)
+	var stdout, stderr bytes.Buffer
+	if code := runWithDeps([]string{"auth", "login", "does-not-exist"}, &stdout, &stderr, appDeps{}); code == exitSuccess {
+		t.Fatal("unknown provider login should fail")
+	}
+	if !strings.Contains(stderr.String(), "not configured") {
+		t.Fatalf("stderr = %q, want not-configured error", stderr.String())
+	}
+}
+
+func TestRunAuthRefreshNoToken(t *testing.T) {
+	withAuthStore(t)
+	t.Setenv("ZERO_OAUTH_DEMO_CLIENT_ID", "client") // so config resolves; refresh still fails (no token)
+	var stdout, stderr bytes.Buffer
+	if code := runWithDeps([]string{"auth", "refresh", "demo"}, &stdout, &stderr, appDeps{}); code == exitSuccess {
+		t.Fatal("refresh with no stored token should fail")
+	}
+}
+
+func TestRunAuthRejectsWrongFlags(t *testing.T) {
+	withAuthStore(t)
+	cases := [][]string{
+		{"auth", "login", "demo", "--watch"},       // watch is refresh-only
+		{"auth", "login", "demo", "--json"},        // json not for interactive login
+		{"auth", "status", "demo", "--device"},     // device is login-only
+		{"auth", "logout", "demo", "--scope", "x"}, // scope is login-only
+		{"auth", "refresh", "demo", "--json"},      // json not for refresh
+		{"auth", "login", "demo", "--scope", ""},   // empty scope rejected
+	}
+	for _, args := range cases {
+		var stdout, stderr bytes.Buffer
+		if code := runWithDeps(args, &stdout, &stderr, appDeps{}); code == exitSuccess {
+			t.Errorf("args %v should be rejected, got success", args)
+		}
+	}
+}
+
+func TestRunAuthOpenRouterRejectsArgs(t *testing.T) {
+	withAuthStore(t)
+	var stdout, stderr bytes.Buffer
+	// An unexpected arg/flag must fail fast, not silently run the login.
+	if code := runWithDeps([]string{"auth", "openrouter", "--json"}, &stdout, &stderr, appDeps{}); code == exitSuccess {
+		t.Fatalf("openrouter with an unexpected flag should fail; stdout=%q", stdout.String())
+	}
+	// --help still works.
+	stdout.Reset()
+	stderr.Reset()
+	if code := runWithDeps([]string{"auth", "openrouter", "--help"}, &stdout, &stderr, appDeps{}); code != exitSuccess {
+		t.Fatalf("openrouter --help should succeed, stderr=%q", stderr.String())
+	}
+}
+
+func TestRunAuthHelp(t *testing.T) {
+	var stdout, stderr bytes.Buffer
+	if code := runWithDeps([]string{"auth", "--help"}, &stdout, &stderr, appDeps{}); code != exitSuccess {
+		t.Fatalf("exit = %d", code)
+	}
+	for _, want := range []string{"zero auth", "login", "logout", "status", "refresh", "--device"} {
+		if !strings.Contains(stdout.String(), want) {
+			t.Fatalf("help missing %q:\n%s", want, stdout.String())
+		}
+	}
+}

internal/cli/backends.go

@@ -17,6 +17,13 @@ type backendStatusOptions struct {
 }
 
 func runBackends(args []string, stdout io.Writer, stderr io.Writer, deps appDeps) int {
+	if len(args) > 0 {
+		switch args[0] {
+		case "doctor":
+			return runBackendsDoctor(args[1:], stdout, stderr, deps)
+		}
+	}
+
 	options, help, err := parseBackendsArgs(args)
 	if err != nil {
 		return writeExecUsageError(stderr, err.Error())
@@ -44,6 +51,44 @@ func runBackends(args []string, stdout io.Writer, stderr io.Writer, deps appDeps
 	return exitSuccess
 }
 
+type backendDoctorOptions struct {
+	json bool
+}
+
+func runBackendsDoctor(args []string, stdout io.Writer, stderr io.Writer, deps appDeps) int {
+	options, help, err := parseBackendsDoctorArgs(args)
+	if err != nil {
+		return writeExecUsageError(stderr, err.Error())
+	}
+	if help {
+		if err := writeBackendsDoctorHelp(stdout); err != nil {
+			return exitCrash
+		}
+		return exitSuccess
+	}
+
+	report, err := backendDoctorReport(deps)
+	if err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	if options.json {
+		if err := writePrettyJSON(stdout, report); err != nil {
+			return exitCrash
+		}
+		if !report.OK {
+			return exitProvider
+		}
+		return exitSuccess
+	}
+	if _, err := fmt.Fprintln(stdout, redaction.RedactString(formatBackendDoctorReport(report), redaction.Options{})); err != nil {
+		return exitCrash
+	}
+	if !report.OK {
+		return exitProvider
+	}
+	return exitSuccess
+}
+
 func parseBackendsArgs(args []string) (backendStatusOptions, bool, error) {
 	options := backendStatusOptions{}
 	for _, arg := range args {
@@ -59,6 +104,21 @@ func parseBackendsArgs(args []string) (backendStatusOptions, bool, error) {
 	return options, false, nil
 }
 
+func parseBackendsDoctorArgs(args []string) (backendDoctorOptions, bool, error) {
+	options := backendDoctorOptions{}
+	for _, arg := range args {
+		switch arg {
+		case "-h", "--help", "help":
+			return options, true, nil
+		case "--json":
+			options.json = true
+		default:
+			return options, false, execUsageError{fmt.Sprintf("unknown backends doctor flag %q", arg)}
+		}
+	}
+	return options, false, nil
+}
+
 func backendLifecycleSnapshot(deps appDeps) (zerocommands.BackendLifecycleSnapshot, error) {
 	cwd, err := deps.getwd()
 	if err != nil {
@@ -86,6 +146,32 @@ func backendLifecycleSnapshot(deps appDeps) (zerocommands.BackendLifecycleSnapsh
 	return zerocommands.NewBackendLifecycleSnapshot(servers, hookResult.Config.Hooks, pluginResult.Plugins), nil
 }
 
+func backendDoctorReport(deps appDeps) (zerocommands.BackendDoctorReport, error) {
+	cwd, err := deps.getwd()
+	if err != nil {
+		return zerocommands.BackendDoctorReport{}, fmt.Errorf("failed to resolve workspace: %w", err)
+	}
+
+	cfg, err := deps.resolveMCPConfig(cwd)
+	if err != nil {
+		return zerocommands.BackendDoctorReport{}, err
+	}
+	hookResult, err := deps.loadHooks(hooks.LoadOptions{Cwd: cwd})
+	if err != nil {
+		return zerocommands.BackendDoctorReport{}, err
+	}
+	pluginResult, err := deps.loadPlugins(plugins.LoadOptions{Cwd: cwd})
+	if err != nil {
+		return zerocommands.BackendDoctorReport{}, err
+	}
+
+	return zerocommands.NewBackendDoctorReport(zerocommands.BackendDoctorInput{
+		MCP:     cfg,
+		Hooks:   hookResult,
+		Plugins: pluginResult,
+	}), nil
+}
+
 func formatBackendLifecycleSnapshot(snapshot zerocommands.BackendLifecycleSnapshot) string {
 	lines := []string{"Zero Backends:"}
 	lines = append(lines, fmt.Sprintf("  MCP servers: %d", len(snapshot.MCPServers)))
@@ -135,16 +221,52 @@ func formatBackendLifecycleSnapshot(snapshot zerocommands.BackendLifecycleSnapsh
 	return strings.Join(lines, "\n")
 }
 
+func formatBackendDoctorReport(report zerocommands.BackendDoctorReport) string {
+	lines := []string{
+		"Zero backend doctor",
+		"Overall: " + string(report.Status),
+	}
+	for _, check := range report.Checks {
+		target := ""
+		if check.Target != "" {
+			target = " " + check.Target
+		}
+		lines = append(lines, fmt.Sprintf("[%s] %s%s - %s", check.Status, check.ID, target, check.Message))
+		if check.Action != "" {
+			lines = append(lines, "  action: "+check.Action)
+		}
+	}
+	return strings.Join(lines, "\n")
+}
+
 func writeBackendsHelp(w io.Writer) error {
 	_, err := fmt.Fprint(w, `Usage:
   zero backends [flags]
+  zero backends doctor [flags]
 
 Inspect MCP, hook, and plugin backend lifecycle state without connecting to
 external MCP servers.
 
+Commands:
+  doctor    Diagnose MCP, hook, and plugin backend setup
+
 Flags:
       --json    Print backend lifecycle data as JSON
   -h, --help    Show this help
 `)
 	return err
 }
+
+func writeBackendsDoctorHelp(w io.Writer) error {
+	_, err := fmt.Fprint(w, `Usage:
+  zero backends doctor [flags]
+
+Diagnose MCP, hook, and plugin backend setup without connecting to external MCP
+servers or executing hooks/plugins.
+
+Flags:
+      --json    Print backend diagnostics as JSON
+  -h, --help    Show this help
+`)
+	return err
+}

internal/cli/backends_test.go

@@ -5,7 +5,12 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
 	"strings"
+	"sync/atomic"
 	"testing"
 
 	"github.com/Gitlawb/zero/internal/config"
@@ -153,3 +158,220 @@ func TestRunBackendsTextAndHelp(t *testing.T) {
 		}
 	}
 }
+
+func TestRunBackendsDoctorJSONAndTextWithoutConnectingMCP(t *testing.T) {
+	cwd := t.TempDir()
+	secret := "sk-proj-" + strings.Repeat("b", 24)
+	deps := appDeps{
+		getwd: func() (string, error) { return cwd, nil },
+		resolveMCPConfig: func(workspaceRoot string) (config.MCPConfig, error) {
+			if workspaceRoot != cwd {
+				t.Fatalf("workspaceRoot = %q, want %q", workspaceRoot, cwd)
+			}
+			return config.MCPConfig{Servers: map[string]config.MCPServerConfig{
+				"remote": {
+					Type: "http",
+					URL:  "https://api.example.com/mcp?token=" + secret,
+				},
+				"broken": {
+					Type: "http",
+				},
+			}}, nil
+		},
+		loadHooks: func(options hooks.LoadOptions) (hooks.LoadResult, error) {
+			if options.Cwd != cwd {
+				t.Fatalf("hook Cwd = %q, want %q", options.Cwd, cwd)
+			}
+			return hooks.LoadResult{Diagnostics: []hooks.Diagnostic{{
+				Kind:    hooks.DiagnosticSchema,
+				Message: "schema failed " + secret,
+				HookID:  "zero.bad",
+			}}}, nil
+		},
+		loadPlugins: func(options plugins.LoadOptions) (plugins.LoadResult, error) {
+			if options.Cwd != cwd {
+				t.Fatalf("plugin Cwd = %q, want %q", options.Cwd, cwd)
+			}
+			return plugins.LoadResult{Plugins: []plugins.LoadedPlugin{{
+				ID:      "zero.docs",
+				Name:    "Docs",
+				Enabled: true,
+				Source:  plugins.SourceProject,
+			}}}, nil
+		},
+		registerMCPTools: func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error) {
+			return nil, errors.New("zero backends doctor must not connect to MCP servers")
+		},
+	}
+
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+	exitCode := runWithDeps([]string{"backends", "doctor", "--json"}, &stdout, &stderr, deps)
+	if exitCode != exitProvider {
+		t.Fatalf("exitCode = %d, want %d stderr=%s stdout=%s", exitCode, exitProvider, stderr.String(), stdout.String())
+	}
+	if strings.Contains(stdout.String(), secret) || strings.Contains(stdout.String(), "sk-proj-") {
+		t.Fatalf("backend doctor JSON leaked secret material:\n%s", stdout.String())
+	}
+	var payload zerocommands.BackendDoctorReport
+	if err := json.Unmarshal(stdout.Bytes(), &payload); err != nil {
+		t.Fatalf("backend doctor JSON failed to decode: %v\n%s", err, stdout.String())
+	}
+	if payload.OK {
+		t.Fatalf("payload.OK = true, want false for invalid MCP/hook diagnostic: %#v", payload.Checks)
+	}
+	if payload.Status != zerocommands.BackendDoctorStatusFail {
+		t.Fatalf("payload.Status = %q, want %q", payload.Status, zerocommands.BackendDoctorStatusFail)
+	}
+	assertBackendDoctorPayloadCheck(t, payload, "backend.mcp.invalid", "broken")
+	assertBackendDoctorPayloadCheck(t, payload, "backend.hooks.diagnostic", "zero.bad")
+
+	stdout.Reset()
+	stderr.Reset()
+	exitCode = runWithDeps([]string{"backends", "doctor"}, &stdout, &stderr, deps)
+	if exitCode != exitProvider {
+		t.Fatalf("text exitCode = %d, want %d stderr=%s", exitCode, exitProvider, stderr.String())
+	}
+	for _, want := range []string{"Zero backend doctor", "[fail] backend.mcp.invalid", "zero mcp add broken", "[fail] backend.hooks.diagnostic"} {
+		if !strings.Contains(stdout.String(), want) {
+			t.Fatalf("backend doctor text missing %q:\n%s", want, stdout.String())
+		}
+	}
+}
+
+func TestRunBackendsDoctorHelp(t *testing.T) {
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+	exitCode := runWithDeps([]string{"backends", "doctor", "--help"}, &stdout, &stderr, appDeps{})
+	if exitCode != exitSuccess {
+		t.Fatalf("exitCode = %d stderr=%s", exitCode, stderr.String())
+	}
+	for _, want := range []string{"Usage:", "zero backends doctor", "--json"} {
+		if !strings.Contains(stdout.String(), want) {
+			t.Fatalf("backend doctor help missing %q:\n%s", want, stdout.String())
+		}
+	}
+}
+
+func TestRunBackendsDoctorDoesNotConnectOrExecuteConfiguredBackends(t *testing.T) {
+	cwd := t.TempDir()
+	hookSentinel := filepath.Join(cwd, "hook-ran")
+	pluginToolSentinel := filepath.Join(cwd, "plugin-tool-ran")
+	pluginHookSentinel := filepath.Join(cwd, "plugin-hook-ran")
+	helperCommand := os.Args[0]
+	helperArgs := func(path string) []string {
+		return []string{"-test.run=TestBackendDoctorHelperProcess", "--", "--zero-backend-doctor-sentinel", path}
+	}
+
+	var hits int32
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		atomic.AddInt32(&hits, 1)
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer server.Close()
+
+	hookConfigPath := filepath.Join(cwd, ".zero", "hooks.json")
+	writeBackendDoctorJSON(t, hookConfigPath, map[string]any{
+		"enabled": true,
+		"hooks": []any{map[string]any{
+			"id":      "zero.sentinel",
+			"event":   "sessionStart",
+			"command": helperCommand,
+			"args":    helperArgs(hookSentinel),
+		}},
+	})
+	pluginDir := filepath.Join(cwd, ".zero", "plugins", "sentinel")
+	writeBackendDoctorJSON(t, filepath.Join(pluginDir, "plugin.json"), map[string]any{
+		"schemaVersion": 1,
+		"id":            "zero.sentinel",
+		"name":          "Sentinel",
+		"version":       "1.0.0",
+		"tools": []any{map[string]any{
+			"name":    "sentinel_tool",
+			"command": helperCommand,
+			"args":    helperArgs(pluginToolSentinel),
+		}},
+		"hooks": []any{map[string]any{
+			"name":    "sentinel_hook",
+			"event":   "sessionStart",
+			"command": helperCommand,
+			"args":    helperArgs(pluginHookSentinel),
+		}},
+	})
+
+	deps := appDeps{
+		getwd: func() (string, error) { return cwd, nil },
+		resolveMCPConfig: func(string) (config.MCPConfig, error) {
+			return config.MCPConfig{Servers: map[string]config.MCPServerConfig{
+				"remote": {Type: "http", URL: server.URL + "/mcp"},
+			}}, nil
+		},
+		loadHooks: func(options hooks.LoadOptions) (hooks.LoadResult, error) {
+			return hooks.LoadConfig(hooks.LoadOptions{
+				Cwd:               options.Cwd,
+				UserConfigPath:    filepath.Join(cwd, "missing-user-hooks.json"),
+				ProjectConfigPath: hookConfigPath,
+			})
+		},
+		loadPlugins: func(options plugins.LoadOptions) (plugins.LoadResult, error) {
+			return plugins.Load(plugins.LoadOptions{
+				Roots: []plugins.Root{{Source: plugins.SourceProject, Path: filepath.Join(cwd, ".zero", "plugins")}},
+				Cwd:   options.Cwd,
+			})
+		},
+		registerMCPTools: func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error) {
+			return nil, errors.New("zero backends doctor must not register MCP tools")
+		},
+	}
+
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+	exitCode := runWithDeps([]string{"backends", "doctor", "--json"}, &stdout, &stderr, deps)
+	if exitCode != exitSuccess {
+		t.Fatalf("exitCode = %d stderr=%s stdout=%s", exitCode, stderr.String(), stdout.String())
+	}
+	if got := atomic.LoadInt32(&hits); got != 0 {
+		t.Fatalf("backend doctor connected to MCP HTTP server %d time(s)", got)
+	}
+	for _, sentinel := range []string{hookSentinel, pluginToolSentinel, pluginHookSentinel} {
+		if _, err := os.Stat(sentinel); !errors.Is(err, os.ErrNotExist) {
+			t.Fatalf("backend doctor executed configured backend command, sentinel=%s err=%v", sentinel, err)
+		}
+	}
+}
+
+func assertBackendDoctorPayloadCheck(t *testing.T, report zerocommands.BackendDoctorReport, id string, target string) {
+	t.Helper()
+	for _, check := range report.Checks {
+		if check.ID == id && check.Target == target {
+			return
+		}
+	}
+	t.Fatalf("check %s/%s not found in %#v", id, target, report.Checks)
+}
+
+func writeBackendDoctorJSON(t *testing.T, path string, value any) {
+	t.Helper()
+	if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
+		t.Fatalf("create dir for %s: %v", path, err)
+	}
+	data, err := json.MarshalIndent(value, "", "  ")
+	if err != nil {
+		t.Fatalf("marshal %s: %v", path, err)
+	}
+	if err := os.WriteFile(path, data, 0o600); err != nil {
+		t.Fatalf("write %s: %v", path, err)
+	}
+}
+
+func TestBackendDoctorHelperProcess(t *testing.T) {
+	for index, arg := range os.Args {
+		if arg != "--zero-backend-doctor-sentinel" || index+1 >= len(os.Args) {
+			continue
+		}
+		if err := os.WriteFile(os.Args[index+1], []byte("executed"), 0o600); err != nil {
+			os.Exit(2)
+		}
+		os.Exit(0)
+	}
+}

internal/cli/daemon.go

@@ -0,0 +1,672 @@
+package cli
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"os/signal"
+	"path/filepath"
+	"strings"
+	"syscall"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/background"
+	"github.com/Gitlawb/zero/internal/daemon"
+	"github.com/Gitlawb/zero/internal/daemon/remote"
+)
+
+// runDaemon dispatches the `zero daemon ...` subcommands. The daemon supervises a
+// pool of headless `zero exec` workers and routes sessions to them over an
+// owner-only local control socket. It is an ADDITIVE surface — interactive and
+// one-shot exec are unchanged.
+func runDaemon(args []string, stdout io.Writer, stderr io.Writer, _ appDeps) int {
+	if len(args) == 0 {
+		return writeDaemonUsage(stderr, exitUsage)
+	}
+	sub, rest := args[0], args[1:]
+	switch sub {
+	case "start":
+		return runDaemonStart(rest, stdout, stderr)
+	case "stop":
+		return runDaemonStop(rest, stdout, stderr)
+	case "status":
+		return runDaemonStatus(rest, stdout, stderr)
+	case "run":
+		return runDaemonRun(rest, stdout, stderr)
+	case "attach":
+		return runDaemonAttach(rest, stdout, stderr)
+	case "serve-remote":
+		return runDaemonServeRemote(rest, stdout, stderr)
+	case "link":
+		return runDaemonLink(rest, stdout, stderr)
+	case "-h", "--help", "help":
+		return writeDaemonUsage(stdout, exitSuccess)
+	default:
+		fmt.Fprintf(stderr, "unknown daemon subcommand %q\n", sub)
+		return writeDaemonUsage(stderr, exitUsage)
+	}
+}
+
+func writeDaemonUsage(w io.Writer, code int) int {
+	fmt.Fprint(w, `Usage: zero daemon <command>
+
+Commands:
+  start [--foreground]      Start the daemon (background by default).
+  stop                      Gracefully stop the running daemon.
+  status                    Show daemon / pool / session status.
+  run --session <id> [--cwd <dir>] [--prompt <text>] [exec flags...]
+                            Create/route a session and stream its output.
+  attach <session>          Attach to a running session's stream.
+  serve-remote --addr <host:port> --tls-cert <f> --tls-key <f> [--bundle-dir <d>]
+                            Serve an opt-in, TLS-only network bridge to this
+                            daemon. Requires a bearer token in $ZERO_DAEMON_REMOTE_TOKEN
+                            (or $ZERO_DAEMON_REMOTE_TOKEN_FILE). --bundle-dir enables
+                            git-bundle uploads, extracted into per-link work trees.
+  link --remote <host:port> --repo <dir> --id <name> [--out <file>]
+                            Upload repo's git history to the remote as a bundle and
+                            print the extracted remote path. --out saves a session
+                            link file (0600). Accepts --token/--ca-cert/--server-name.
+  link --show <file>        Print a saved session link.
+
+run and attach accept --remote <host:port> [--token <t>] [--ca-cert <f>]
+[--server-name <name>] to drive a remote daemon over the bridge instead of the
+local socket. Use the link's remote path as --cwd to run against a linked repo.
+`)
+	return code
+}
+
+// runDaemonStart starts the daemon. Without --foreground it spawns a detached
+// background process running the foreground daemon and returns once it is up.
+func runDaemonStart(args []string, stdout io.Writer, stderr io.Writer) int {
+	foreground := false
+	for _, a := range args {
+		switch a {
+		case "--foreground", "-f":
+			foreground = true
+		case "-h", "--help":
+			return writeDaemonUsage(stdout, exitSuccess)
+		default:
+			return writeExecUsageError(stderr, fmt.Sprintf("unknown flag %q for daemon start", a))
+		}
+	}
+	paths, err := daemon.DefaultPaths()
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	if foreground {
+		return runDaemonForeground(paths, stdout, stderr)
+	}
+	return runDaemonStartDetached(paths, stdout, stderr)
+}
+
+// runDaemonForeground runs the daemon in this process until SIGINT/SIGTERM. Each
+// worker is a headless `zero exec` child with the sandbox re-entrancy markers
+// scrubbed (NewExecLauncher) so it establishes its own sandbox.
+func runDaemonForeground(paths daemon.Paths, stdout io.Writer, stderr io.Writer) int {
+	launcher, err := daemon.NewExecLauncher(daemon.ExecLauncherConfig{})
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	logf := func(line string) { fmt.Fprintln(stderr, "[daemon] "+line) }
+	pool, err := daemon.NewPool(daemon.PoolOptions{Launcher: launcher, Log: logf})
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	mgr, err := daemon.NewSessionManager(daemon.SessionManagerOptions{Pool: pool})
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	srv, err := daemon.NewServer(daemon.ServerOptions{Paths: paths, Manager: mgr, Pool: pool, Log: logf})
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+
+	sigCh := make(chan os.Signal, 1)
+	signal.Notify(sigCh, os.Interrupt, syscall.SIGTERM)
+	go func() {
+		<-sigCh
+		srv.Shutdown()
+	}()
+
+	if err := srv.Serve(); err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	return exitSuccess
+}
+
+// runDaemonStartDetached spawns the foreground daemon as a detached background
+// process (its own process group, output to a log file) and waits for it to bind.
+func runDaemonStartDetached(paths daemon.Paths, stdout io.Writer, stderr io.Writer) int {
+	if daemonReachable(paths) {
+		fmt.Fprintln(stdout, "zero daemon is already running")
+		return exitSuccess
+	}
+	exe, err := os.Executable()
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	if err := os.MkdirAll(filepath.Dir(paths.Socket), 0o700); err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	logPath := filepath.Join(filepath.Dir(paths.Socket), "daemon.log")
+	logFile, err := os.OpenFile(logPath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o600)
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	defer logFile.Close()
+
+	cmd := exec.Command(exe, "daemon", "start", "--foreground")
+	cmd.Stdout = logFile
+	cmd.Stderr = logFile
+	background.ConfigureChildProcessGroup(cmd) // own process group: outlives this shell
+	if err := cmd.Start(); err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	_ = cmd.Process.Release()
+
+	deadline := time.Now().Add(5 * time.Second)
+	for time.Now().Before(deadline) {
+		if daemonReachable(paths) {
+			fmt.Fprintf(stdout, "zero daemon started (socket %s)\n", paths.Socket)
+			return exitSuccess
+		}
+		time.Sleep(25 * time.Millisecond)
+	}
+	return writeAppError(stderr, "daemon did not come up within timeout; see "+logPath, exitCrash)
+}
+
+func runDaemonStop(args []string, stdout io.Writer, stderr io.Writer) int {
+	if helpRequested(args) {
+		return writeDaemonUsage(stdout, exitSuccess)
+	}
+	if len(args) > 0 {
+		return writeExecUsageError(stderr, "daemon stop takes no arguments")
+	}
+	paths, err := daemon.DefaultPaths()
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	client, err := daemon.Dial(paths.Socket)
+	if err != nil {
+		fmt.Fprintln(stdout, "zero daemon is not running")
+		return exitSuccess
+	}
+	defer client.Close()
+	if err := client.Shutdown(); err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	fmt.Fprintln(stdout, "zero daemon stopped")
+	return exitSuccess
+}
+
+func runDaemonStatus(args []string, stdout io.Writer, stderr io.Writer) int {
+	if helpRequested(args) {
+		return writeDaemonUsage(stdout, exitSuccess)
+	}
+	if len(args) > 0 {
+		return writeExecUsageError(stderr, "daemon status takes no arguments")
+	}
+	paths, err := daemon.DefaultPaths()
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	client, err := daemon.Dial(paths.Socket)
+	if err != nil {
+		fmt.Fprintln(stdout, "zero daemon is not running")
+		return exitSuccess
+	}
+	defer client.Close()
+	report, err := client.Status()
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	fmt.Fprintf(stdout, "daemon pid=%d version=%d socket=%s\n", report.PID, report.Version, report.Socket)
+	fmt.Fprintf(stdout, "pool size=%d busy=%d queue=%d\n", report.PoolSize, len(report.Workers), report.QueueDepth)
+	for _, s := range report.Sessions {
+		fmt.Fprintf(stdout, "  session %s state=%s lines=%d\n", s.ID, s.State, s.Lines)
+	}
+	return exitSuccess
+}
+
+func runDaemonRun(args []string, stdout io.Writer, stderr io.Writer) int {
+	session, cwd, prompt := "", "", ""
+	var remoteFlags remoteDialFlags
+	var forward []string
+	for i := 0; i < len(args); i++ {
+		a := args[i]
+		value := func() (string, bool) {
+			if i+1 >= len(args) {
+				return "", false
+			}
+			i++
+			return args[i], true
+		}
+		switch {
+		case a == "-h" || a == "--help":
+			return writeDaemonUsage(stdout, exitSuccess)
+		case a == "--remote":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--remote requires a value")
+			}
+			remoteFlags.Addr = v
+		case strings.HasPrefix(a, "--remote="):
+			remoteFlags.Addr = strings.TrimPrefix(a, "--remote=")
+		case a == "--token":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--token requires a value")
+			}
+			remoteFlags.Token = v
+		case strings.HasPrefix(a, "--token="):
+			remoteFlags.Token = strings.TrimPrefix(a, "--token=")
+		case a == "--ca-cert":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--ca-cert requires a value")
+			}
+			remoteFlags.CACert = v
+		case strings.HasPrefix(a, "--ca-cert="):
+			remoteFlags.CACert = strings.TrimPrefix(a, "--ca-cert=")
+		case a == "--server-name":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--server-name requires a value")
+			}
+			remoteFlags.ServerName = v
+		case strings.HasPrefix(a, "--server-name="):
+			remoteFlags.ServerName = strings.TrimPrefix(a, "--server-name=")
+		case a == "--session":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--session requires a value")
+			}
+			session = v
+		case strings.HasPrefix(a, "--session="):
+			session = strings.TrimPrefix(a, "--session=")
+		case a == "--cwd":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--cwd requires a value")
+			}
+			cwd = v
+		case strings.HasPrefix(a, "--cwd="):
+			cwd = strings.TrimPrefix(a, "--cwd=")
+		case a == "--prompt" || a == "-p":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--prompt requires a value")
+			}
+			prompt = v
+		case strings.HasPrefix(a, "--prompt="):
+			prompt = strings.TrimPrefix(a, "--prompt=")
+		default:
+			// Forwarded verbatim to the worker `zero exec` (reuses exec's own flag
+			// parsing for per-session run options).
+			forward = append(forward, a)
+		}
+	}
+	if strings.TrimSpace(session) == "" {
+		return writeExecUsageError(stderr, "daemon run requires --session <id>")
+	}
+	if prompt == "" && len(forward) == 0 {
+		return writeExecUsageError(stderr, "daemon run requires --prompt <text> or exec args")
+	}
+	client, err := dialForCLI(remoteFlags)
+	if err != nil {
+		return writeAppError(stderr, daemonDialError(remoteFlags, err), exitCrash)
+	}
+	defer client.Close()
+	if err := client.Run(session, cwd, prompt, forward, func(line string) { fmt.Fprintln(stdout, line) }); err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	return exitSuccess
+}
+
+func runDaemonAttach(args []string, stdout io.Writer, stderr io.Writer) int {
+	session := ""
+	var remoteFlags remoteDialFlags
+	extra := 0
+	for i := 0; i < len(args); i++ {
+		a := args[i]
+		value := func() (string, bool) {
+			if i+1 >= len(args) {
+				return "", false
+			}
+			i++
+			return args[i], true
+		}
+		switch {
+		case a == "-h" || a == "--help":
+			return writeDaemonUsage(stdout, exitSuccess)
+		case a == "--remote":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--remote requires a value")
+			}
+			remoteFlags.Addr = v
+		case strings.HasPrefix(a, "--remote="):
+			remoteFlags.Addr = strings.TrimPrefix(a, "--remote=")
+		case a == "--token":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--token requires a value")
+			}
+			remoteFlags.Token = v
+		case strings.HasPrefix(a, "--token="):
+			remoteFlags.Token = strings.TrimPrefix(a, "--token=")
+		case a == "--ca-cert":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--ca-cert requires a value")
+			}
+			remoteFlags.CACert = v
+		case strings.HasPrefix(a, "--ca-cert="):
+			remoteFlags.CACert = strings.TrimPrefix(a, "--ca-cert=")
+		case a == "--server-name":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--server-name requires a value")
+			}
+			remoteFlags.ServerName = v
+		case strings.HasPrefix(a, "--server-name="):
+			remoteFlags.ServerName = strings.TrimPrefix(a, "--server-name=")
+		case session == "":
+			session = a
+		default:
+			extra++
+		}
+	}
+	if strings.TrimSpace(session) == "" {
+		return writeExecUsageError(stderr, "daemon attach requires a <session> id")
+	}
+	if extra > 0 {
+		return writeExecUsageError(stderr, "daemon attach accepts exactly one <session> id")
+	}
+	client, err := dialForCLI(remoteFlags)
+	if err != nil {
+		return writeAppError(stderr, daemonDialError(remoteFlags, err), exitCrash)
+	}
+	defer client.Close()
+	if err := client.Attach(session, func(line string) { fmt.Fprintln(stdout, line) }); err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	return exitSuccess
+}
+
+// daemonDialError tailors the connect-failure message for local vs remote.
+func daemonDialError(flags remoteDialFlags, err error) string {
+	if strings.TrimSpace(flags.Addr) != "" {
+		return "failed to reach remote daemon at " + flags.Addr + ": " + err.Error()
+	}
+	return "zero daemon is not running (start it with `zero daemon start`)"
+}
+
+// runDaemonServeRemote starts the local daemon plus an opt-in, TLS-only network
+// bridge. TLS and a bearer token are mandatory (fail closed): it refuses to
+// start without a cert/key pair and a token from the environment.
+func runDaemonServeRemote(args []string, stdout io.Writer, stderr io.Writer) int {
+	addr, certFile, keyFile, bundleDir := "", "", "", ""
+	minVersion, maxConns := 0, 0
+	for i := 0; i < len(args); i++ {
+		a := args[i]
+		value := func() (string, bool) {
+			if i+1 >= len(args) {
+				return "", false
+			}
+			i++
+			return args[i], true
+		}
+		switch {
+		case a == "-h" || a == "--help":
+			return writeDaemonUsage(stdout, exitSuccess)
+		case a == "--addr":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--addr requires a value")
+			}
+			addr = v
+		case strings.HasPrefix(a, "--addr="):
+			addr = strings.TrimPrefix(a, "--addr=")
+		case a == "--tls-cert":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--tls-cert requires a value")
+			}
+			certFile = v
+		case strings.HasPrefix(a, "--tls-cert="):
+			certFile = strings.TrimPrefix(a, "--tls-cert=")
+		case a == "--tls-key":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--tls-key requires a value")
+			}
+			keyFile = v
+		case strings.HasPrefix(a, "--tls-key="):
+			keyFile = strings.TrimPrefix(a, "--tls-key=")
+		case a == "--min-version":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--min-version requires a value")
+			}
+			minVersion = atoiOrZero(v)
+		case a == "--max-conns":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--max-conns requires a value")
+			}
+			maxConns = atoiOrZero(v)
+		case a == "--bundle-dir":
+			v, ok := value()
+			if !ok {
+				return writeExecUsageError(stderr, "--bundle-dir requires a value")
+			}
+			bundleDir = v
+		case strings.HasPrefix(a, "--bundle-dir="):
+			bundleDir = strings.TrimPrefix(a, "--bundle-dir=")
+		default:
+			return writeExecUsageError(stderr, fmt.Sprintf("unknown flag %q for daemon serve-remote", a))
+		}
+	}
+	if strings.TrimSpace(addr) == "" {
+		return writeExecUsageError(stderr, "daemon serve-remote requires --addr <host:port>")
+	}
+	// Fail closed: TLS cert/key + a bearer token are mandatory.
+	tlsConfig, err := remote.ServerTLSConfig(certFile, keyFile)
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	token, err := remote.TokenFromEnv()
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	auth, err := remote.NewTokenAuthenticator(token)
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	paths, err := daemon.DefaultPaths()
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	launcher, err := daemon.NewExecLauncher(daemon.ExecLauncherConfig{})
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	logf := func(line string) { fmt.Fprintln(stderr, "[daemon] "+line) }
+	pool, err := daemon.NewPool(daemon.PoolOptions{Launcher: launcher, Log: logf})
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	mgr, err := daemon.NewSessionManager(daemon.SessionManagerOptions{Pool: pool})
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	srv, err := daemon.NewServer(daemon.ServerOptions{Paths: paths, Manager: mgr, Pool: pool, Log: logf})
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	bridge, err := remote.NewBridge(remote.BridgeOptions{
+		Server: srv, Authenticator: auth, MinVersion: minVersion, MaxConnections: maxConns, BundleDir: bundleDir, Log: logf,
+	})
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+
+	// Serve the local control socket too, so local clients keep working.
+	go func() {
+		if serveErr := srv.Serve(); serveErr != nil {
+			logf("local serve error: " + serveErr.Error())
+		}
+	}()
+
+	serveErr := make(chan error, 1)
+	go func() { serveErr <- bridge.ListenAndServeTLS(addr, tlsConfig) }()
+
+	sigCh := make(chan os.Signal, 1)
+	signal.Notify(sigCh, os.Interrupt, syscall.SIGTERM)
+
+	fmt.Fprintf(stdout, "zero daemon remote bridge listening on %s (TLS)\n", addr)
+	select {
+	case <-sigCh:
+		srv.Shutdown()
+		_ = bridge.Close()
+		<-serveErr // wait for the accept loop to unwind
+		return exitSuccess
+	case err := <-serveErr:
+		// Bind/serve failed before any signal (e.g. address in use).
+		srv.Shutdown()
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+}
+
+// runDaemonLink uploads a repo's git history to a remote bridge as a bundle
+// (link without --show), or prints a saved session link (--show <file>).
+func runDaemonLink(args []string, stdout io.Writer, stderr io.Writer) int {
+	var addr, repo, id, token, caCert, serverName, out, show string
+	// flags maps each "--name" to the string it sets; both "--name v" and
+	// "--name=v" forms are accepted.
+	flags := map[string]*string{
+		"--remote": &addr, "--repo": &repo, "--id": &id, "--token": &token,
+		"--ca-cert": &caCert, "--server-name": &serverName, "--out": &out, "--show": &show,
+	}
+	for i := 0; i < len(args); i++ {
+		a := args[i]
+		if a == "-h" || a == "--help" {
+			return writeDaemonUsage(stdout, exitSuccess)
+		}
+		name, inlineVal, hasInline := a, "", false
+		if eq := strings.IndexByte(a, '='); eq >= 0 {
+			name, inlineVal, hasInline = a[:eq], a[eq+1:], true
+		}
+		dst, ok := flags[name]
+		if !ok {
+			return writeExecUsageError(stderr, fmt.Sprintf("unknown flag %q for daemon link", a))
+		}
+		if hasInline {
+			*dst = inlineVal
+			continue
+		}
+		if i+1 >= len(args) {
+			return writeExecUsageError(stderr, fmt.Sprintf("%s requires a value", name))
+		}
+		i++
+		*dst = args[i]
+	}
+
+	if strings.TrimSpace(show) != "" {
+		link, err := remote.LoadSessionLink(show)
+		if err != nil {
+			return writeAppError(stderr, err.Error(), exitCrash)
+		}
+		fmt.Fprintf(stdout, "link %s -> %s on %s\n", link.LinkID, link.RemotePath, link.Address)
+		return exitSuccess
+	}
+
+	if strings.TrimSpace(addr) == "" || strings.TrimSpace(repo) == "" || strings.TrimSpace(id) == "" {
+		return writeExecUsageError(stderr, "daemon link requires --remote, --repo, and --id (or --show <file>)")
+	}
+	if strings.TrimSpace(token) == "" {
+		token, _ = remote.TokenFromEnv() // best effort; UploadRepoBundle rejects an empty token
+	}
+	link, err := remote.UploadRepoBundle(remote.RemoteConfig{
+		Address:    addr,
+		Token:      token,
+		CACertFile: caCert,
+		ServerName: serverName,
+	}, repo, id)
+	if err != nil {
+		return writeAppError(stderr, err.Error(), exitCrash)
+	}
+	fmt.Fprintf(stdout, "uploaded %s; remote repo at %s\n", link.LinkID, link.RemotePath)
+	fmt.Fprintf(stdout, "run it with: zero daemon run --remote %s --cwd %s ...\n", link.Address, link.RemotePath)
+	if strings.TrimSpace(out) != "" {
+		if err := link.Save(out); err != nil {
+			return writeAppError(stderr, err.Error(), exitCrash)
+		}
+		fmt.Fprintf(stdout, "saved session link to %s\n", out)
+	}
+	return exitSuccess
+}
+
+// remoteDialFlags holds the optional flags that redirect run/attach to a remote
+// daemon. When Addr is empty the local control socket is used.
+type remoteDialFlags struct {
+	Addr       string
+	Token      string
+	CACert     string
+	ServerName string
+}
+
+// dialForCLI returns a daemon.Client for either the local socket (Addr empty) or
+// a remote bridge (Addr set). For remote, the token falls back to the env.
+func dialForCLI(flags remoteDialFlags) (*daemon.Client, error) {
+	if strings.TrimSpace(flags.Addr) == "" {
+		paths, err := daemon.DefaultPaths()
+		if err != nil {
+			return nil, err
+		}
+		return daemon.Dial(paths.Socket)
+	}
+	token := strings.TrimSpace(flags.Token)
+	if token == "" {
+		token, _ = remote.TokenFromEnv() // best effort; DialRemote rejects an empty token
+	}
+	return remote.DialRemote(remote.RemoteConfig{
+		Address:    flags.Addr,
+		Token:      token,
+		CACertFile: flags.CACert,
+		ServerName: flags.ServerName,
+	})
+}
+
+func atoiOrZero(s string) int {
+	n := 0
+	for _, r := range strings.TrimSpace(s) {
+		if r < '0' || r > '9' {
+			return 0
+		}
+		n = n*10 + int(r-'0')
+	}
+	return n
+}
+
+// daemonReachable reports whether a daemon is accepting connections (a successful
+// handshake). Used for the single-instance check and start-up wait.
+func daemonReachable(paths daemon.Paths) bool {
+	client, err := daemon.Dial(paths.Socket)
+	if err != nil {
+		return false
+	}
+	_ = client.Close()
+	return true
+}
+
+func helpRequested(args []string) bool {
+	for _, a := range args {
+		if a == "-h" || a == "--help" {
+			return true
+		}
+	}
+	return false
+}

internal/cli/daemon_test.go

@@ -0,0 +1,123 @@
+package cli
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+// isolateDaemonPaths points DefaultPaths at a temp dir so the test never touches
+// a real daemon on the dev machine.
+func isolateDaemonPaths(t *testing.T) {
+	t.Helper()
+	t.Setenv("XDG_RUNTIME_DIR", t.TempDir())
+}
+
+func runDaemonCLI(t *testing.T, args ...string) (int, string, string) {
+	t.Helper()
+	var out, errb bytes.Buffer
+	code := runDaemon(args, &out, &errb, appDeps{})
+	return code, out.String(), errb.String()
+}
+
+func TestDaemonUsage(t *testing.T) {
+	code, _, _ := runDaemonCLI(t)
+	if code != exitUsage {
+		t.Fatalf("no-args exit = %d, want exitUsage", code)
+	}
+	code, out, _ := runDaemonCLI(t, "--help")
+	if code != exitSuccess || !strings.Contains(out, "Usage: zero daemon") {
+		t.Fatalf("--help exit=%d out=%q", code, out)
+	}
+}
+
+func TestDaemonUnknownSubcommand(t *testing.T) {
+	code, _, errb := runDaemonCLI(t, "frobnicate")
+	if code != exitUsage {
+		t.Fatalf("unknown subcommand exit = %d, want exitUsage", code)
+	}
+	if !strings.Contains(errb, "unknown daemon subcommand") {
+		t.Fatalf("stderr = %q, want unknown-subcommand message", errb)
+	}
+}
+
+func TestDaemonRunRequiresSession(t *testing.T) {
+	isolateDaemonPaths(t)
+	code, _, errb := runDaemonCLI(t, "run", "--prompt", "hi")
+	if code != exitUsage {
+		t.Fatalf("run without --session exit = %d, want exitUsage", code)
+	}
+	if !strings.Contains(errb, "--session") {
+		t.Fatalf("stderr = %q, want a --session hint", errb)
+	}
+}
+
+func TestDaemonRunRequiresPromptOrArgs(t *testing.T) {
+	isolateDaemonPaths(t)
+	code, _, errb := runDaemonCLI(t, "run", "--session", "s1")
+	if code != exitUsage {
+		t.Fatalf("run without prompt/args exit = %d, want exitUsage", code)
+	}
+	if !strings.Contains(errb, "--prompt") {
+		t.Fatalf("stderr = %q, want a --prompt hint", errb)
+	}
+}
+
+func TestDaemonStopWhenNotRunning(t *testing.T) {
+	isolateDaemonPaths(t)
+	code, out, _ := runDaemonCLI(t, "stop")
+	if code != exitSuccess {
+		t.Fatalf("stop (not running) exit = %d, want exitSuccess", code)
+	}
+	if !strings.Contains(out, "not running") {
+		t.Fatalf("stop output = %q, want 'not running'", out)
+	}
+}
+
+func TestDaemonStatusWhenNotRunning(t *testing.T) {
+	isolateDaemonPaths(t)
+	code, out, _ := runDaemonCLI(t, "status")
+	if code != exitSuccess {
+		t.Fatalf("status (not running) exit = %d, want exitSuccess", code)
+	}
+	if !strings.Contains(out, "not running") {
+		t.Fatalf("status output = %q, want 'not running'", out)
+	}
+}
+
+func TestDaemonAttachRequiresSession(t *testing.T) {
+	isolateDaemonPaths(t)
+	code, _, errb := runDaemonCLI(t, "attach")
+	if code != exitUsage {
+		t.Fatalf("attach without session exit = %d, want exitUsage", code)
+	}
+	if !strings.Contains(errb, "session") {
+		t.Fatalf("stderr = %q, want a session hint", errb)
+	}
+}
+
+func TestDaemonRunWhenNotRunning(t *testing.T) {
+	isolateDaemonPaths(t)
+	code, _, errb := runDaemonCLI(t, "run", "--session", "s1", "--prompt", "hello")
+	if code != exitCrash {
+		t.Fatalf("run (no daemon) exit = %d, want exitCrash", code)
+	}
+	if !strings.Contains(errb, "not running") {
+		t.Fatalf("stderr = %q, want 'not running'", errb)
+	}
+}
+
+func TestDaemonSubcommandsRejectExtraArgs(t *testing.T) {
+	isolateDaemonPaths(t)
+	cases := [][]string{
+		{"stop", "oops"},
+		{"status", "oops"},
+		{"attach", "s1", "extra"},
+	}
+	for _, args := range cases {
+		code, _, errb := runDaemonCLI(t, args...)
+		if code != exitUsage {
+			t.Fatalf("%v exit = %d, want exitUsage (reject extra args); stderr=%q", args, code, errb)
+		}
+	}
+}

internal/cli/exec.go

@@ -19,7 +19,6 @@ import (
 	"github.com/Gitlawb/zero/internal/providers"
 	"github.com/Gitlawb/zero/internal/sandbox"
 	"github.com/Gitlawb/zero/internal/sessions"
-	"github.com/Gitlawb/zero/internal/specialist"
 	"github.com/Gitlawb/zero/internal/specmode"
 	"github.com/Gitlawb/zero/internal/streamjson"
 	"github.com/Gitlawb/zero/internal/tools"
@@ -163,7 +162,7 @@ func runExec(args []string, stdout io.Writer, stderr io.Writer, deps appDeps) in
 	if options.allowEscalation {
 		registry.Register(tools.NewEscalateModelTool())
 	}
-	var specialistRuntime *specialist.Runtime
+	var specialistRuntime *agentToolRuntime
 	if shouldRegisterExecSpecialistTools(options) {
 		var err error
 		specialistRuntime, err = registerSpecialistTools(registry, workspaceRoot)
@@ -368,6 +367,12 @@ func runExec(args []string, stdout io.Writer, stderr io.Writer, deps appDeps) in
 		Mode:      notify.Mode(strings.TrimSpace(execNotifyMode(options, resolved))),
 		FocusMode: notify.FocusAlways,
 	})
+	// Opt-in webhook fan-out (ZERO_NOTIFY_WEBHOOK_URL). Headless runs can safely
+	// log a failed delivery to stderr (never stdout). The sink redacts before
+	// logging, so a token in the URL or message is masked.
+	notify.MaybeAddWebhookSink(notifier, os.Getenv, func(format string, args ...any) {
+		fmt.Fprintf(stderr, "[notify] "+format+"\n", args...)
+	})
 	if options.useSpec {
 		return runExecSpecDraft(execSpecDraftRun{
 			options:            options,
@@ -704,7 +709,8 @@ func buildExecSandboxEngine(workspaceRoot string, resolved config.ResolvedConfig
 // depth — it guarantees that even a direct/programmatic caller passing a typo
 // can never WIDEN the ceiling back to the High default.
 // applyConfiguredSandboxPolicy overlays every config-sourced sandbox knob onto
-// the default policy: the autonomy ceiling and the network mode.
+// the default policy (the autonomy ceiling and the network mode), plus the
+// ZERO_SANDBOX_AUTO_ALLOW_BASH environment opt-in.
 func applyConfiguredSandboxPolicy(policy sandbox.Policy, cfg config.SandboxConfig) sandbox.Policy {
 	policy = applyConfiguredAutonomyCeiling(policy, cfg.MaxAutonomy)
 	if network := strings.TrimSpace(cfg.Network); network != "" {
@@ -721,6 +727,12 @@ func applyConfiguredSandboxPolicy(policy sandbox.Policy, cfg config.SandboxConfi
 	if cfg.MonitorDenials {
 		policy.MonitorDenials = true
 	}
+	// ZERO_SANDBOX_AUTO_ALLOW_BASH opts into auto-allowing a *sandboxed* shell
+	// command without a prompt — the active sandbox is the safety boundary, and
+	// the engine only honors this when the shell sandbox is actually active. Like
+	// the flags above it only ever turns the opt-in ON; unset/blank stays off
+	// (prompt), and an explicit config opt-in is preserved.
+	policy = sandbox.ApplyAutoAllowBashEnv(policy)
 	return policy
 }
 

internal/cli/oauth_credential_test.go

@@ -0,0 +1,47 @@
+package cli
+
+import (
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/config"
+	"github.com/Gitlawb/zero/internal/oauth"
+)
+
+func TestProviderHasOAuthLogin(t *testing.T) {
+	xai := config.ProviderProfile{Name: "xai", CatalogID: "xai"}
+	if providerHasOAuthLogin(xai, nil) {
+		t.Fatal("no stored login must be false")
+	}
+	if !providerHasOAuthLogin(xai, map[string]bool{"xai": true}) {
+		t.Fatal("a stored login keyed by name must be true")
+	}
+	if !providerHasOAuthLogin(config.ProviderProfile{Name: "grok", CatalogID: "xai"}, map[string]bool{"xai": true}) {
+		t.Fatal("a stored login keyed by catalog id must be true")
+	}
+}
+
+func TestSetupRequiredRecognizesOAuthLogin(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "tok.json")
+	t.Setenv("ZERO_OAUTH_TOKENS_PATH", path)
+	store, err := oauth.NewStore(oauth.StoreOptions{FilePath: path})
+	if err != nil {
+		t.Fatalf("NewStore: %v", err)
+	}
+	if err := store.Save(oauth.ProviderKey("xai"), oauth.Token{AccessToken: "tok", ExpiresAt: time.Now().Add(time.Hour)}); err != nil {
+		t.Fatalf("seed token: %v", err)
+	}
+
+	// xai has no inline key (env-only) but IS logged in via OAuth → no setup.
+	loggedIn := config.ResolvedConfig{Provider: config.ProviderProfile{Name: "xai", CatalogID: "xai", APIKeyEnv: "XAI_API_KEY"}}
+	if setupRequired(loggedIn) {
+		t.Fatal("a provider with a stored OAuth login must not require onboarding")
+	}
+
+	// A keyless provider with no OAuth login still requires setup.
+	noLogin := config.ResolvedConfig{Provider: config.ProviderProfile{Name: "openai", CatalogID: "openai", APIKeyEnv: "OPENAI_API_KEY"}}
+	if !setupRequired(noLogin) {
+		t.Fatal("a keyless provider with no OAuth login must require onboarding")
+	}
+}

internal/cli/oauth_provider.go

@@ -0,0 +1,67 @@
+package cli
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/config"
+	"github.com/Gitlawb/zero/internal/oauth"
+	"github.com/Gitlawb/zero/internal/providers/providerio"
+)
+
+// providerOAuthName resolves the OAuth login name for a provider profile. It is
+// the name a user logs in under (`zero auth login <name>`) whose token then
+// authenticates this provider's model calls. For now it is the profile name;
+// the provider presets map well-known kinds (openai/anthropic) to canonical
+// names on top of this.
+func providerOAuthName(profile config.ProviderProfile) string {
+	return strings.TrimSpace(profile.Name)
+}
+
+// oauthResolverForProfile returns a TokenResolver that authenticates a provider's
+// model calls with the user's OAuth login, or nil when no login exists for this
+// provider. Returning nil for the no-login case keeps API-key users free of any
+// per-request store lookups: the resolver is only attached once a login is
+// present at construction time.
+func oauthResolverForProfile(profile config.ProviderProfile) providerio.TokenResolver {
+	name := providerOAuthName(profile)
+	if name == "" {
+		return nil
+	}
+	store, err := oauth.NewStore(oauth.StoreOptions{})
+	if err != nil {
+		return nil
+	}
+	key := oauth.ProviderKey(name)
+	if _, ok, loadErr := store.Load(key); loadErr != nil || !ok {
+		// No login (or an unreadable/invalid key) → API-key auth, no resolver.
+		return nil
+	}
+	manager, err := oauth.NewManager(oauth.ManagerOptions{
+		Store:      store,
+		HTTPClient: &http.Client{Timeout: 30 * time.Second},
+	})
+	if err != nil {
+		return nil
+	}
+	return func(ctx context.Context, forceRefresh bool) (string, string, bool, error) {
+		var token string
+		var rerr error
+		if forceRefresh {
+			token, rerr = manager.Handle401(ctx, key)
+		} else {
+			token, rerr = manager.GetFresh(ctx, key)
+		}
+		if errors.Is(rerr, oauth.ErrNoToken) {
+			// The login was removed since construction → fall back to the API key.
+			return "", "", false, nil
+		}
+		if rerr != nil {
+			return "", "", false, rerr
+		}
+		return "Authorization", "Bearer " + token, true, nil
+	}
+}

internal/cli/sandbox_test.go

@@ -662,6 +662,19 @@ func TestApplyConfiguredSandboxPolicyHardeningFlags(t *testing.T) {
 	}
 }
 
+func TestApplyConfiguredSandboxPolicyHonorsAutoAllowBashEnv(t *testing.T) {
+	// Unset/blank: the opt-in stays off so a sandboxed bash command still prompts.
+	t.Setenv(sandbox.EnvAutoAllowBash, "")
+	if got := applyConfiguredSandboxPolicy(sandbox.DefaultPolicy(), config.SandboxConfig{}); got.AutoAllowBashWhenSandboxed {
+		t.Fatal("auto-allow-bash must be off when ZERO_SANDBOX_AUTO_ALLOW_BASH is unset")
+	}
+	// Truthy: the env opt-in is wired through the central policy builder.
+	t.Setenv(sandbox.EnvAutoAllowBash, "true")
+	if got := applyConfiguredSandboxPolicy(sandbox.DefaultPolicy(), config.SandboxConfig{}); !got.AutoAllowBashWhenSandboxed {
+		t.Fatal("ZERO_SANDBOX_AUTO_ALLOW_BASH=true must enable AutoAllowBashWhenSandboxed")
+	}
+}
+
 func newSandboxTestStore(t *testing.T) *sandbox.GrantStore {
 	t.Helper()
 	store, err := sandbox.NewGrantStore(sandbox.StoreOptions{

internal/cli/setup.go

@@ -3,11 +3,13 @@ package cli
 import (
 	"fmt"
 	"io"
+	"net/url"
 	"strconv"
 	"strings"
 	"unicode"
 
 	"github.com/Gitlawb/zero/internal/config"
+	"github.com/Gitlawb/zero/internal/oauth"
 	"github.com/Gitlawb/zero/internal/providercatalog"
 	"github.com/Gitlawb/zero/internal/providerhealth"
 	"github.com/Gitlawb/zero/internal/provideronboarding"
@@ -285,8 +287,108 @@ func setupRequired(resolved config.ResolvedConfig) bool {
 	if !config.HasProviderProfile(resolved.Provider) {
 		return true
 	}
-	_, missing := setupMissingCredentialEnv(resolved.Provider)
-	return missing
+	if _, missing := setupMissingCredentialEnv(resolved.Provider); !missing {
+		return false
+	}
+	// A stored OAuth login (e.g. `zero auth login xai`) is a credential too, even
+	// though the profile has no inline key / env var — so a logged-in provider
+	// must not trigger onboarding.
+	return !providerHasOAuthLogin(resolved.Provider, oauthLoggedInProviders())
+}
+
+// providerHasOAuthLogin reports whether a stored OAuth login exists for the
+// provider, keyed by its profile name or catalog id.
+func providerHasOAuthLogin(profile config.ProviderProfile, oauthLogins map[string]bool) bool {
+	for _, name := range []string{strings.TrimSpace(profile.Name), strings.TrimSpace(profile.CatalogID)} {
+		if name != "" && oauthLogins[name] {
+			return true
+		}
+	}
+	return false
+}
+
+// oauthLoggedInProviders returns the set of provider names that have a stored
+// OAuth token, so credential checks recognize an OAuth login (not just inline
+// keys / env vars). Errors degrade to an empty set (no logins).
+func oauthLoggedInProviders() map[string]bool {
+	out := map[string]bool{}
+	store, err := oauth.NewStore(oauth.StoreOptions{})
+	if err != nil {
+		return out
+	}
+	statuses, err := store.Status(oauth.KeyPrefixProvider)
+	if err != nil {
+		return out
+	}
+	for _, status := range statuses {
+		if status.HasToken {
+			out[strings.TrimPrefix(status.Key, oauth.KeyPrefixProvider)] = true
+		}
+	}
+	return out
+}
+
+// firstUsableProvider returns the saved provider best suited to run without
+// onboarding: the first usable (inline credential present, or no-auth/local)
+// non-local provider, else the first usable local one. It lets the CLI fall back
+// to an already-configured login when the active provider happens to lack a
+// credential, instead of re-running onboarding every launch.
+func firstUsableProvider(providers []config.ProviderProfile) (config.ProviderProfile, bool) {
+	var localFallback config.ProviderProfile
+	haveLocal := false
+	for _, profile := range providers {
+		if !config.HasProviderProfile(profile) {
+			continue
+		}
+		// A profile whose catalog entry no longer resolves AND that has no explicit
+		// BaseURL has no endpoint to talk to, so it cannot become a working
+		// provider — skip it rather than picking a fallback that fails at first use.
+		// (A stale CatalogID with a BaseURL still works as a custom endpoint.)
+		if catalogID := strings.TrimSpace(profile.CatalogID); catalogID != "" && strings.TrimSpace(profile.BaseURL) == "" {
+			if _, err := providercatalog.Require(catalogID); err != nil {
+				continue
+			}
+		}
+		if _, missing := setupMissingCredentialEnv(profile); missing {
+			continue
+		}
+		if providerProfileIsLocal(profile) {
+			if !haveLocal {
+				localFallback = profile
+				haveLocal = true
+			}
+			continue
+		}
+		return profile, true
+	}
+	if haveLocal {
+		return localFallback, true
+	}
+	return config.ProviderProfile{}, false
+}
+
+// providerProfileIsLocal reports whether a provider points at a local endpoint
+// (a loopback URL or a catalog entry flagged Local), so the fallback prefers a
+// remote keyed provider that is more likely reachable.
+func providerProfileIsLocal(profile config.ProviderProfile) bool {
+	if catalogID := strings.TrimSpace(profile.CatalogID); catalogID != "" {
+		if descriptor, err := providercatalog.Require(catalogID); err == nil && descriptor.Local {
+			return true
+		}
+	}
+	base := strings.TrimSpace(profile.BaseURL)
+	if base == "" {
+		return false
+	}
+	parsed, err := url.Parse(base)
+	if err != nil {
+		return false
+	}
+	switch strings.ToLower(parsed.Hostname()) {
+	case "localhost", "127.0.0.1", "::1":
+		return true
+	}
+	return false
 }
 
 func formatSetupComplete(result tui.SetupResult) string {

internal/cli/setup_fallback_test.go

@@ -0,0 +1,91 @@
+package cli
+
+import (
+	"testing"
+
+	"github.com/Gitlawb/zero/internal/config"
+)
+
+func TestFirstUsableProviderPrefersRemoteKeyed(t *testing.T) {
+	providers := []config.ProviderProfile{
+		{Name: "ollama", CatalogID: "ollama", BaseURL: "http://localhost:11434/v1", APIKey: "k"},      // usable but local
+		{Name: "moonshot", CatalogID: "moonshot", BaseURL: "https://api.moonshot.ai/v1", APIKey: "k"}, // usable, remote
+		{Name: "xai", CatalogID: "xai", APIKeyEnv: "XAI_API_KEY"},                                     // not usable (env only, no inline key)
+	}
+	got, ok := firstUsableProvider(providers)
+	if !ok || got.Name != "moonshot" {
+		t.Fatalf("want remote keyed provider (moonshot), got %q ok=%v", got.Name, ok)
+	}
+}
+
+func TestFirstUsableProviderFallsBackToLocal(t *testing.T) {
+	providers := []config.ProviderProfile{
+		{Name: "xai", CatalogID: "xai", APIKeyEnv: "XAI_API_KEY"},                                // not usable
+		{Name: "ollama", CatalogID: "ollama", BaseURL: "http://localhost:11434/v1", APIKey: "k"}, // local, usable
+	}
+	got, ok := firstUsableProvider(providers)
+	if !ok || got.Name != "ollama" {
+		t.Fatalf("want local usable fallback (ollama), got %q ok=%v", got.Name, ok)
+	}
+}
+
+func TestFirstUsableProviderNoneUsable(t *testing.T) {
+	providers := []config.ProviderProfile{
+		{Name: "xai", CatalogID: "xai", APIKeyEnv: "XAI_API_KEY"},
+		{Name: "openai", CatalogID: "openai", APIKeyEnv: "OPENAI_API_KEY"},
+	}
+	if got, ok := firstUsableProvider(providers); ok {
+		t.Fatalf("no provider has a credential, want ok=false, got %q", got.Name)
+	}
+}
+
+// A keyless local proxy (chatgpt-proxy, RequiresAuth=false) is usable without a
+// credential, so it can serve as a fallback rather than forcing onboarding.
+func TestFirstUsableProviderAcceptsKeylessLocalProxy(t *testing.T) {
+	providers := []config.ProviderProfile{
+		{Name: "xai", CatalogID: "xai", APIKeyEnv: "XAI_API_KEY"},
+		{Name: "chatgpt", CatalogID: "chatgpt-proxy", BaseURL: "http://localhost:10531/v1"},
+	}
+	got, ok := firstUsableProvider(providers)
+	if !ok || got.Name != "chatgpt" {
+		t.Fatalf("want keyless local proxy fallback, got %q ok=%v", got.Name, ok)
+	}
+}
+
+// A profile whose catalog entry no longer resolves and that carries no explicit
+// BaseURL has no endpoint, so it must be skipped rather than selected as a
+// fallback that fails at first use. A stale CatalogID with a BaseURL still works.
+func TestFirstUsableProviderSkipsUnresolvableCatalogWithoutBaseURL(t *testing.T) {
+	providers := []config.ProviderProfile{
+		{Name: "ghost", CatalogID: "no-such-catalog-entry", APIKey: "k"}, // unusable: no endpoint
+		{Name: "custom", CatalogID: "no-such-catalog-entry", BaseURL: "https://api.custom.test/v1", APIKey: "k"},
+	}
+	got, ok := firstUsableProvider(providers)
+	if !ok || got.Name != "custom" {
+		t.Fatalf("want custom-endpoint fallback, got %q ok=%v", got.Name, ok)
+	}
+}
+
+func TestProviderProfileIsLocal(t *testing.T) {
+	cases := []struct {
+		name    string
+		baseURL string
+		want    bool
+	}{
+		{"loopback name", "http://localhost:11434/v1", true},
+		{"loopback v4", "http://127.0.0.1:8080", true},
+		{"loopback v6", "http://[::1]:10531/v1", true},
+		{"remote", "https://api.moonshot.ai/v1", false},
+		{"contains-localhost-substring", "https://notlocalhost.com/v1", false},
+		{"host-with-127-substring", "https://api127.0.0.1.example.com", false},
+		{"empty", "", false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := providerProfileIsLocal(config.ProviderProfile{BaseURL: tc.baseURL})
+			if got != tc.want {
+				t.Fatalf("providerProfileIsLocal(%q) = %v, want %v", tc.baseURL, got, tc.want)
+			}
+		})
+	}
+}

internal/config/resolver_test.go

@@ -1094,7 +1094,8 @@ func TestResolveProviderProfileExtendedJSONAliases(t *testing.T) {
 			"auth_scheme": "raw",
 			"auth_header_value": "header-secret",
 			"custom_headers": {"X-Zero": "1"},
-			"model_id": "custom-model"
+			"model_id": "custom-model",
+			"parse_think_tags": true
 		}]
 	}`)
 
@@ -1119,6 +1120,30 @@ func TestResolveProviderProfileExtendedJSONAliases(t *testing.T) {
 	if profile.CustomHeaders["X-Zero"] != "1" {
 		t.Fatalf("CustomHeaders = %#v, want X-Zero header", profile.CustomHeaders)
 	}
+	if profile.ParseThinkTags == nil || !*profile.ParseThinkTags {
+		t.Fatalf("ParseThinkTags = %#v, want true", profile.ParseThinkTags)
+	}
+}
+
+func TestResolveProviderProfileParseThinkTagsFalseAlias(t *testing.T) {
+	path := writeConfig(t, `{
+		"activeProvider": "custom",
+		"providers": [{
+			"name": "custom",
+			"provider_kind": "openai-compatible",
+			"base_url": "https://custom.example/v1",
+			"model_id": "custom-model",
+			"parse_think_tags": false
+		}]
+	}`)
+
+	resolved, err := Resolve(ResolveOptions{UserConfigPath: path, Env: map[string]string{}})
+	if err != nil {
+		t.Fatalf("Resolve() error = %v", err)
+	}
+	if resolved.Provider.ParseThinkTags == nil || *resolved.Provider.ParseThinkTags {
+		t.Fatalf("ParseThinkTags = %#v, want explicit false", resolved.Provider.ParseThinkTags)
+	}
 }
 
 func TestResolveRejectsUnknownProviderCatalogID(t *testing.T) {

internal/config/types.go

@@ -34,6 +34,7 @@ type ProviderProfile struct {
 	AuthHeaderValue string            `json:"authHeaderValue,omitempty"`
 	CustomHeaders   map[string]string `json:"customHeaders,omitempty"`
 	Model           string            `json:"model,omitempty"`
+	ParseThinkTags  *bool             `json:"parseThinkTags,omitempty"`
 	Description     string            `json:"description,omitempty"`
 }
 
@@ -51,6 +52,7 @@ func HasProviderProfile(profile ProviderProfile) bool {
 		strings.TrimSpace(profile.AuthHeaderValue) != "" ||
 		profile.CustomHeaders != nil ||
 		strings.TrimSpace(profile.Model) != "" ||
+		profile.ParseThinkTags != nil ||
 		strings.TrimSpace(profile.Description) != ""
 }
 
@@ -304,6 +306,8 @@ func (profile *ProviderProfile) UnmarshalJSON(data []byte) error {
 		CustomHeadersSnake   map[string]string `json:"custom_headers"`
 		Model                string            `json:"model"`
 		ModelID              string            `json:"model_id"`
+		ParseThinkTags       *bool             `json:"parseThinkTags"`
+		ParseThinkTagsSnake  *bool             `json:"parse_think_tags"`
 		Description          string            `json:"description"`
 	}
 
@@ -325,6 +329,7 @@ func (profile *ProviderProfile) UnmarshalJSON(data []byte) error {
 	profile.AuthHeaderValue = firstNonEmpty(raw.AuthHeaderValue, raw.AuthHeaderValueSnake)
 	profile.CustomHeaders = firstNonNilMap(raw.CustomHeaders, raw.CustomHeadersSnake)
 	profile.Model = strings.TrimSpace(firstNonEmpty(raw.Model, raw.ModelID))
+	profile.ParseThinkTags = firstNonNilBool(raw.ParseThinkTags, raw.ParseThinkTagsSnake)
 	profile.Description = strings.TrimSpace(raw.Description)
 	return nil
 }
@@ -348,6 +353,15 @@ func firstNonNilMap(values ...map[string]string) map[string]string {
 	return nil
 }
 
+func firstNonNilBool(values ...*bool) *bool {
+	for _, value := range values {
+		if value != nil {
+			return value
+		}
+	}
+	return nil
+}
+
 func copyStringMap(values map[string]string) map[string]string {
 	if values == nil {
 		return nil

internal/config/writer.go

@@ -72,6 +72,43 @@ func SetActiveProvider(path string, name string) (FileConfig, error) {
 	return FileConfig{}, fmt.Errorf("provider %q not found", name)
 }
 
+func SetProviderModel(path string, name string, model string) (FileConfig, error) {
+	path = strings.TrimSpace(path)
+	if path == "" {
+		return FileConfig{}, fmt.Errorf("config path is required")
+	}
+	name = strings.TrimSpace(name)
+	if name == "" {
+		return FileConfig{}, fmt.Errorf("provider name is required")
+	}
+	model = strings.TrimSpace(model)
+	if model == "" {
+		return FileConfig{}, fmt.Errorf("model is required")
+	}
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return FileConfig{}, fmt.Errorf("read config %s: %w", path, err)
+	}
+
+	cfg := FileConfig{}
+	if err := json.Unmarshal(data, &cfg); err != nil {
+		return FileConfig{}, fmt.Errorf("invalid config JSON %s: %w", path, err)
+	}
+
+	for index := range cfg.Providers {
+		if strings.EqualFold(cfg.Providers[index].Name, name) {
+			cfg.Providers[index].Model = model
+			if err := writeConfigFile(path, cfg); err != nil {
+				return FileConfig{}, err
+			}
+			return cfg, nil
+		}
+	}
+
+	return FileConfig{}, fmt.Errorf("provider %q not found", name)
+}
+
 func SetFavoriteModels(path string, models []string) (FileConfig, error) {
 	path = strings.TrimSpace(path)
 	if path == "" {

internal/config/writer_test.go

@@ -150,6 +150,72 @@ func TestSetActiveProviderTightensExistingConfigFilePermissions(t *testing.T) {
 	}
 }
 
+func TestSetProviderModelUpdatesConfiguredProvider(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "zero.json")
+	writeConfigFixture(t, path, FileConfig{
+		ActiveProvider: "openai",
+		Providers: []ProviderProfile{
+			{
+				Name:         "openai",
+				ProviderKind: ProviderKindOpenAI,
+				APIKey:       "sk-test",
+				Model:        "gpt-4.1",
+			},
+			{
+				Name:         "anthropic",
+				ProviderKind: ProviderKindAnthropic,
+				Model:        "claude-sonnet-4.5",
+			},
+		},
+	}, 0o600)
+
+	cfg, err := SetProviderModel(path, " OpenAI ", " gpt-4.1-mini ")
+	if err != nil {
+		t.Fatalf("SetProviderModel() error = %v", err)
+	}
+
+	if cfg.Providers[0].Model != "gpt-4.1-mini" {
+		t.Fatalf("updated provider model = %q, want gpt-4.1-mini", cfg.Providers[0].Model)
+	}
+	if cfg.Providers[0].APIKey != "sk-test" {
+		t.Fatalf("provider credential was not preserved: %#v", cfg.Providers[0])
+	}
+	if cfg.Providers[1].Model != "claude-sonnet-4.5" {
+		t.Fatalf("unrelated provider changed: %#v", cfg.Providers[1])
+	}
+
+	persisted := readConfigFixture(t, path)
+	if persisted.Providers[0].Model != "gpt-4.1-mini" {
+		t.Fatalf("persisted provider model = %q, want gpt-4.1-mini", persisted.Providers[0].Model)
+	}
+	if persisted.ActiveProvider != "openai" {
+		t.Fatalf("active provider changed to %q", persisted.ActiveProvider)
+	}
+}
+
+func TestSetProviderModelRejectsUnknownProviderWithoutRewriting(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "zero.json")
+	before := writeConfigFixture(t, path, FileConfig{
+		ActiveProvider: "openai",
+		Providers: []ProviderProfile{
+			{Name: "openai", ProviderKind: ProviderKindOpenAI, Model: "gpt-4.1"},
+		},
+	}, 0o600)
+
+	_, err := SetProviderModel(path, "anthropic", "claude-sonnet-4.5")
+	if err == nil {
+		t.Fatal("SetProviderModel() error = nil, want error")
+	}
+
+	after, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("read config: %v", err)
+	}
+	if string(after) != string(before) {
+		t.Fatalf("config was rewritten for unknown provider\nbefore: %s\nafter: %s", before, after)
+	}
+}
+
 func TestUpsertProviderTightensExistingConfigFilePermissions(t *testing.T) {
 	if runtime.GOOS == "windows" {
 		t.Skip("Windows does not expose POSIX mode bits reliably")

internal/daemon/backoff.go

@@ -0,0 +1,41 @@
+package daemon
+
+import (
+	"math/rand"
+	"time"
+)
+
+// Backoff bounds. Mirrors reference-daemon-code-agent-js/worker-manager.js:
+// backoffMs(consecutive) = jitter(min(1000 * 2**consecutive, 300000)).
+const (
+	backoffUnit = time.Second
+	backoffCap  = 5 * time.Minute
+)
+
+// backoffBase returns the un-jittered exponential delay for a 1-based restart
+// count: min(1s * 2^attempt, 5m). attempt<=0 yields the unit delay.
+func backoffBase(attempt int) time.Duration {
+	if attempt <= 0 {
+		return backoffUnit
+	}
+	// Shift carefully: cap before overflow. 2^attempt * 1s exceeds the cap well
+	// before any int64 overflow (cap is 5m), so clamp once it would exceed it.
+	d := backoffUnit
+	for i := 0; i < attempt; i++ {
+		d *= 2
+		if d >= backoffCap {
+			return backoffCap
+		}
+	}
+	return d
+}
+
+// BackoffWithJitter returns backoffBase(attempt) scaled by a uniform random
+// factor in [0.5, 1.5), matching worker-manager.js jitter(base) =
+// base*(0.5 + random()). The jitter de-synchronizes simultaneous restarts so a
+// fleet of workers does not thunder back at the same instant.
+func BackoffWithJitter(attempt int) time.Duration {
+	base := backoffBase(attempt)
+	factor := 0.5 + rand.Float64() //nolint:gosec // jitter, not security-sensitive
+	return time.Duration(float64(base) * factor)
+}

internal/daemon/backoff_test.go

@@ -0,0 +1,38 @@
+package daemon
+
+import (
+	"testing"
+	"time"
+)
+
+func TestBackoffBaseExponentialAndCap(t *testing.T) {
+	cases := []struct {
+		attempt int
+		want    time.Duration
+	}{
+		{0, 1 * time.Second},
+		{1, 2 * time.Second},
+		{2, 4 * time.Second},
+		{3, 8 * time.Second},
+		{20, backoffCap}, // far past the cap
+	}
+	for _, tc := range cases {
+		if got := backoffBase(tc.attempt); got != tc.want {
+			t.Fatalf("backoffBase(%d) = %s, want %s", tc.attempt, got, tc.want)
+		}
+	}
+}
+
+func TestBackoffWithJitterBounds(t *testing.T) {
+	for attempt := 1; attempt <= 6; attempt++ {
+		base := backoffBase(attempt)
+		lo := time.Duration(float64(base) * 0.5)
+		hi := time.Duration(float64(base) * 1.5)
+		for i := 0; i < 200; i++ {
+			got := BackoffWithJitter(attempt)
+			if got < lo || got >= hi {
+				t.Fatalf("BackoffWithJitter(%d) = %s, want in [%s,%s)", attempt, got, lo, hi)
+			}
+		}
+	}
+}

internal/daemon/client.go

@@ -0,0 +1,130 @@
+package daemon
+
+import (
+	"fmt"
+	"net"
+	"time"
+)
+
+// Client is a control-socket client used by the `zero daemon run|attach|status|
+// stop` subcommands. It performs the version handshake on Dial.
+type Client struct {
+	conn net.Conn
+}
+
+// Dial connects to the daemon control socket and completes the handshake.
+func Dial(socketPath string) (*Client, error) {
+	conn, err := net.DialTimeout("unix", socketPath, 5*time.Second)
+	if err != nil {
+		return nil, err
+	}
+	c := &Client{conn: conn}
+	if err := c.handshake(); err != nil {
+		_ = conn.Close()
+		return nil, err
+	}
+	return c, nil
+}
+
+// NewClientConn completes the control handshake on an already-connected
+// transport (e.g. a TLS connection the remote bridge has authenticated) and
+// returns a Client ready for Run/Attach/Status. It takes ownership of conn and
+// closes it on handshake failure.
+func NewClientConn(conn net.Conn) (*Client, error) {
+	c := &Client{conn: conn}
+	if err := c.handshake(); err != nil {
+		_ = conn.Close()
+		return nil, err
+	}
+	return c, nil
+}
+
+func (c *Client) handshake() error {
+	if err := WriteControl(c.conn, Ctrl{Type: CtrlHello, Version: ProtoVersion}); err != nil {
+		return err
+	}
+	reply, err := ReadControl(c.conn)
+	if err != nil {
+		return err
+	}
+	if reply.Type != CtrlHelloOK {
+		return fmt.Errorf("daemon: handshake rejected: %s", reply.Message)
+	}
+	return nil
+}
+
+// Close closes the connection.
+func (c *Client) Close() error { return c.conn.Close() }
+
+// Run starts/routes a session and streams its stream-json output lines to onLine
+// until the session ends. It returns the session's terminal error, if any.
+func (c *Client) Run(session, cwd, prompt string, args []string, onLine func(string)) error {
+	if err := WriteControl(c.conn, Ctrl{Type: CtrlRun, Session: session, Cwd: cwd, Prompt: prompt, Args: args}); err != nil {
+		return err
+	}
+	return c.streamLoop(onLine)
+}
+
+// Attach streams a running session's output (buffered history + live) to onLine.
+func (c *Client) Attach(session string, onLine func(string)) error {
+	if err := WriteControl(c.conn, Ctrl{Type: CtrlAttach, Session: session}); err != nil {
+		return err
+	}
+	return c.streamLoop(onLine)
+}
+
+func (c *Client) streamLoop(onLine func(string)) error {
+	for {
+		msg, err := ReadControl(c.conn)
+		if err != nil {
+			return err
+		}
+		switch msg.Type {
+		case CtrlAck:
+			// dispatch acknowledged; keep reading
+		case CtrlData:
+			if onLine != nil {
+				onLine(msg.Line)
+			}
+		case CtrlEnd:
+			return nil
+		case CtrlError:
+			return fmt.Errorf("daemon: %s", msg.Message)
+		default:
+			return fmt.Errorf("daemon: unexpected message %q", msg.Type)
+		}
+	}
+}
+
+// Status requests the daemon/worker/session status report.
+func (c *Client) Status() (*StatusReport, error) {
+	if err := WriteControl(c.conn, Ctrl{Type: CtrlStatus}); err != nil {
+		return nil, err
+	}
+	msg, err := ReadControl(c.conn)
+	if err != nil {
+		return nil, err
+	}
+	if msg.Type == CtrlError {
+		return nil, fmt.Errorf("daemon: %s", msg.Message)
+	}
+	if msg.Type != CtrlStatusResult || msg.Status == nil {
+		return nil, fmt.Errorf("daemon: unexpected status reply %q", msg.Type)
+	}
+	return msg.Status, nil
+}
+
+// Shutdown asks the daemon to drain and stop.
+func (c *Client) Shutdown() error {
+	if err := WriteControl(c.conn, Ctrl{Type: CtrlShutdown}); err != nil {
+		return err
+	}
+	msg, err := ReadControl(c.conn)
+	if err != nil {
+		return err
+	}
+	if msg.Type == CtrlError {
+		return fmt.Errorf("daemon: %s", msg.Message)
+	}
+	return nil
+}

internal/daemon/launcher.go

@@ -0,0 +1,165 @@
+package daemon
+
+import (
+	"bufio"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/Gitlawb/zero/internal/background"
+	"github.com/Gitlawb/zero/internal/sandbox"
+)
+
+// reentrancyMarkers are the env vars zero sets on a command it has ALREADY
+// wrapped in a sandbox. The daemon MUST strip them from every worker's
+// environment: a worker that inherited them would trip zero's re-entrancy guard
+// (sandbox.IsAlreadySandboxed needs BOTH) and run with a pass-through plan —
+// i.e. UNSANDBOXED — silently defeating the sandbox. Stripping them forces each
+// worker to (re)establish its own sandbox. This is the daemon's #1 security
+// invariant: it must NOT bypass the sandbox.
+var reentrancyMarkers = []string{sandbox.EnvSandboxed, sandbox.EnvSandboxBackend}
+
+// scrubWorkerEnv returns env with the sandbox re-entrancy markers removed. Every
+// other variable is preserved — including the ZERO_SANDBOX_* policy config the
+// worker reads to rebuild its own policy — so the sandbox policy is PROPAGATED,
+// not bypassed. The caller's slice is never mutated.
+func scrubWorkerEnv(env []string) []string {
+	out := make([]string, 0, len(env))
+	for _, kv := range env {
+		drop := false
+		for _, marker := range reentrancyMarkers {
+			if strings.HasPrefix(kv, marker+"=") {
+				drop = true
+				break
+			}
+		}
+		if !drop {
+			out = append(out, kv)
+		}
+	}
+	return out
+}
+
+// execWorker is a WorkerHandle backed by a `zero exec` child process speaking
+// stream-json on stdout.
+type execWorker struct {
+	cmd    *exec.Cmd
+	stdout io.ReadCloser
+	lines  *scannerLines
+	pid    int
+}
+
+func (w *execWorker) Stdout() Lines { return w.lines }
+func (w *execWorker) Pid() int      { return w.pid }
+
+func (w *execWorker) Wait() (int, error) {
+	err := w.cmd.Wait()
+	if err == nil {
+		return 0, nil
+	}
+	var exitErr *exec.ExitError
+	if errors.As(err, &exitErr) {
+		return exitErr.ExitCode(), nil
+	}
+	return -1, err
+}
+
+func (w *execWorker) Kill() error {
+	if w.cmd.Process == nil {
+		return nil
+	}
+	// background.TerminateProcess is the cross-platform terminate (kills the
+	// process group on POSIX, taskkill /T on Windows).
+	return background.TerminateProcess(w.cmd.Process.Pid)
+}
+
+// scannerLines adapts a bufio.Scanner to the Lines interface.
+type scannerLines struct {
+	sc *bufio.Scanner
+}
+
+func (s *scannerLines) Next() (string, bool, error) {
+	if s.sc.Scan() {
+		return s.sc.Text(), true, nil
+	}
+	if err := s.sc.Err(); err != nil {
+		return "", false, err
+	}
+	return "", false, nil
+}
+
+// ExecLauncherConfig configures the production worker launcher.
+type ExecLauncherConfig struct {
+	// Executable is the zero binary to spawn (defaults to os.Executable()).
+	Executable string
+	// BaseArgs are prepended before the per-session args (defaults to the headless
+	// stream-json exec invocation `exec --output-format stream-json`).
+	BaseArgs []string
+	// Env is the base environment for workers (defaults to os.Environ()). The
+	// re-entrancy markers are always scrubbed from it.
+	Env []string
+}
+
+// NewExecLauncher builds a Launcher that spawns `zero exec` workers which speak
+// stream-json on stdout. Each worker:
+//   - runs with the re-entrancy markers SCRUBBED from its env (so it establishes
+//     its own sandbox; the daemon never bypasses the sandbox), while the rest of
+//     the policy config/env is propagated;
+//   - is placed in its own process group (background.ConfigureChildProcessGroup)
+//     so Kill / drain can terminate it and any children cleanly;
+//   - has its per-session working directory (spec.Cwd) and flags (spec.Args)
+//     applied. The pool does the os/exec itself and uses internal/background only
+//     for process-group setup + cross-platform terminate.
+func NewExecLauncher(cfg ExecLauncherConfig) (Launcher, error) {
+	exe := cfg.Executable
+	if exe == "" {
+		resolved, err := os.Executable()
+		if err != nil {
+			return nil, fmt.Errorf("daemon: locate zero executable: %w", err)
+		}
+		exe = resolved
+	}
+	baseArgs := cfg.BaseArgs
+	if baseArgs == nil {
+		baseArgs = []string{"exec", "--output-format", "stream-json"}
+	}
+	baseEnv := cfg.Env
+	if baseEnv == nil {
+		baseEnv = os.Environ()
+	}
+	env := scrubWorkerEnv(baseEnv)
+
+	return func(ctx context.Context, spec WorkerSpec) (WorkerHandle, error) {
+		args := make([]string, 0, len(baseArgs)+len(spec.Args))
+		args = append(args, baseArgs...)
+		args = append(args, spec.Args...)
+
+		cmd := exec.CommandContext(ctx, exe, args...)
+		cmd.Dir = spec.Cwd
+		cmd.Env = env
+		cmd.Stdin = nil // the prompt is passed via flags; no streamed stdin input
+		background.ConfigureChildProcessGroup(cmd)
+
+		stdout, err := cmd.StdoutPipe()
+		if err != nil {
+			return nil, fmt.Errorf("daemon: worker stdout pipe: %w", err)
+		}
+		if err := cmd.Start(); err != nil {
+			return nil, fmt.Errorf("daemon: start worker: %w", err)
+		}
+
+		scanner := bufio.NewScanner(stdout)
+		// Allow long stream-json lines up to the control-frame cap.
+		scanner.Buffer(make([]byte, 0, 64*1024), MaxFrameSize)
+		return &execWorker{
+			cmd:    cmd,
+			stdout: stdout,
+			lines:  &scannerLines{sc: scanner},
+			pid:    cmd.Process.Pid,
+		}, nil
+	}, nil
+}

internal/daemon/launcher_test.go

@@ -0,0 +1,102 @@
+package daemon
+
+import (
+	"context"
+	"runtime"
+	"strings"
+	"testing"
+
+	"github.com/Gitlawb/zero/internal/sandbox"
+)
+
+func TestScrubWorkerEnvRemovesReentrancyMarkers(t *testing.T) {
+	in := []string{
+		"PATH=/bin",
+		sandbox.EnvSandboxed + "=1",
+		"ZERO_SANDBOX_AUTO_ALLOW_BASH=1", // policy config — must be PRESERVED
+		sandbox.EnvSandboxBackend + "=bubblewrap",
+		"HOME=/home/u",
+	}
+	out := scrubWorkerEnv(in)
+
+	for _, kv := range out {
+		if strings.HasPrefix(kv, sandbox.EnvSandboxed+"=") || strings.HasPrefix(kv, sandbox.EnvSandboxBackend+"=") {
+			t.Fatalf("re-entrancy marker not scrubbed: %q", kv)
+		}
+	}
+	want := map[string]bool{"PATH=/bin": true, "ZERO_SANDBOX_AUTO_ALLOW_BASH=1": true, "HOME=/home/u": true}
+	got := map[string]bool{}
+	for _, kv := range out {
+		got[kv] = true
+	}
+	for w := range want {
+		if !got[w] {
+			t.Fatalf("scrub dropped a non-marker var: %q", w)
+		}
+	}
+	if len(out) != len(want) {
+		t.Fatalf("scrub result = %v, want exactly %d preserved vars", out, len(want))
+	}
+	if len(in) != 5 {
+		t.Fatal("scrubWorkerEnv must not mutate the caller's slice")
+	}
+}
+
+// TestExecLauncherScrubsEnvEndToEnd proves the spawned WORKER PROCESS actually
+// receives an environment without the re-entrancy markers — the security
+// invariant. It uses /bin/sh to dump the worker env, so it is POSIX-only.
+func TestExecLauncherScrubsEnvEndToEnd(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("uses the POSIX env dumper /bin/sh -c env")
+	}
+	launcher, err := NewExecLauncher(ExecLauncherConfig{
+		Executable: "/bin/sh",
+		BaseArgs:   []string{"-c", "env"},
+		Env: append([]string{"KEEP=yes"},
+			sandbox.EnvSandboxed+"=1",
+			sandbox.EnvSandboxBackend+"=bubblewrap"),
+	})
+	if err != nil {
+		t.Fatalf("NewExecLauncher: %v", err)
+	}
+	h, err := launcher(context.Background(), WorkerSpec{})
+	if err != nil {
+		t.Fatalf("launch: %v", err)
+	}
+	lines := h.Stdout()
+	var got []string
+	for {
+		line, ok, lerr := lines.Next()
+		if lerr != nil {
+			t.Fatalf("read worker stdout: %v", lerr)
+		}
+		if !ok {
+			break
+		}
+		got = append(got, line)
+	}
+	if _, err := h.Wait(); err != nil {
+		t.Fatalf("worker wait: %v", err)
+	}
+
+	keepSeen := false
+	for _, l := range got {
+		if strings.HasPrefix(l, sandbox.EnvSandboxed+"=") || strings.HasPrefix(l, sandbox.EnvSandboxBackend+"=") {
+			t.Fatalf("worker process still has a re-entrancy marker in its env: %q", l)
+		}
+		if l == "KEEP=yes" {
+			keepSeen = true
+		}
+	}
+	if !keepSeen {
+		t.Fatalf("worker env lost a non-marker var (KEEP=yes); got %v", got)
+	}
+}
+
+func TestNewExecLauncherDefaults(t *testing.T) {
+	// With no Executable it resolves the test binary's own path (os.Executable),
+	// and constructs without error.
+	if _, err := NewExecLauncher(ExecLauncherConfig{}); err != nil {
+		t.Fatalf("NewExecLauncher with defaults: %v", err)
+	}
+}

internal/daemon/lock.go

@@ -0,0 +1,87 @@
+package daemon
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"strconv"
+	"strings"
+)
+
+// Single-instance lock. Mirrors reference-daemon-code-agent-js/supervisor.js's
+// lock file: a PID file created with O_EXCL. A second start fails; a STALE lock
+// left by a dead daemon (the recorded PID is no longer alive) is reclaimed so the
+// daemon recovers from an unclean shutdown without manual cleanup.
+
+// ErrAlreadyRunning is returned when a live daemon already holds the lock.
+var ErrAlreadyRunning = errors.New("daemon: another instance is already running")
+
+// fileLock is an acquired single-instance lock.
+type fileLock struct {
+	path string
+}
+
+// processAlive reports whether pid is a live process. Implemented per-platform
+// (lock_posix.go / lock_windows.go). It is a package var so tests can stub it.
+var processAlive = osProcessAlive
+
+// acquireLock takes the single-instance lock at path, reclaiming a stale lock
+// whose recorded PID is dead. isAlive overrides the liveness check (tests pass a
+// stub); nil uses the real processAlive.
+func acquireLock(path string, isAlive func(pid int) bool) (*fileLock, error) {
+	if isAlive == nil {
+		isAlive = processAlive
+	}
+	// At most two passes: create, or detect-stale-then-retry once.
+	for attempt := 0; attempt < 2; attempt++ {
+		f, err := os.OpenFile(path, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
+		if err == nil {
+			// A failed PID write would leave a malformed lock file that another
+			// process reads as stale (unparsable PID) and wrongly reclaims, breaking
+			// the single-instance guarantee — so on write failure, remove it and fail.
+			if _, werr := fmt.Fprintf(f, "%d\n", os.Getpid()); werr != nil {
+				_ = f.Close()
+				_ = os.Remove(path)
+				return nil, werr
+			}
+			if cerr := f.Close(); cerr != nil {
+				_ = os.Remove(path)
+				return nil, cerr
+			}
+			return &fileLock{path: path}, nil
+		}
+		if !errors.Is(err, fs.ErrExist) {
+			return nil, err
+		}
+		pid, perr := readPidFile(path)
+		if perr == nil && pid > 0 && isAlive(pid) {
+			return nil, fmt.Errorf("%w (pid %d)", ErrAlreadyRunning, pid)
+		}
+		// Stale lock (dead PID or unreadable) — remove and retry once.
+		if rmErr := os.Remove(path); rmErr != nil && !errors.Is(rmErr, fs.ErrNotExist) {
+			return nil, rmErr
+		}
+	}
+	return nil, ErrAlreadyRunning
+}
+
+// release removes the lock file. Safe to call once.
+func (l *fileLock) release() error {
+	if l == nil || l.path == "" {
+		return nil
+	}
+	if err := os.Remove(l.path); err != nil && !errors.Is(err, fs.ErrNotExist) {
+		return err
+	}
+	return nil
+}
+
+// readPidFile reads and parses the PID recorded in a lock file.
+func readPidFile(path string) (int, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return 0, err
+	}
+	return strconv.Atoi(strings.TrimSpace(string(data)))
+}

internal/daemon/lock_posix.go

@@ -0,0 +1,22 @@
+//go:build !windows
+
+package daemon
+
+import (
+	"errors"
+	"syscall"
+)
+
+// osProcessAlive reports whether pid is a live process on POSIX. Signal 0 does
+// not deliver a signal; it only checks existence/permission. ESRCH means no such
+// process (dead); EPERM means it exists but we may not signal it (alive).
+func osProcessAlive(pid int) bool {
+	if pid <= 0 {
+		return false
+	}
+	err := syscall.Kill(pid, 0)
+	if err == nil {
+		return true
+	}
+	return errors.Is(err, syscall.EPERM)
+}

internal/daemon/lock_test.go

@@ -0,0 +1,77 @@
+package daemon
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+func TestLockSingleInstance(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "daemon.lock")
+	alive := func(int) bool { return true }
+
+	l1, err := acquireLock(path, alive)
+	if err != nil {
+		t.Fatalf("first acquireLock: %v", err)
+	}
+	// Second acquire while the holder is "alive" must be refused.
+	if _, err := acquireLock(path, alive); !errors.Is(err, ErrAlreadyRunning) {
+		t.Fatalf("second acquireLock err = %v, want ErrAlreadyRunning", err)
+	}
+	// After release, a new acquire succeeds.
+	if err := l1.release(); err != nil {
+		t.Fatalf("release: %v", err)
+	}
+	l2, err := acquireLock(path, alive)
+	if err != nil {
+		t.Fatalf("acquire after release: %v", err)
+	}
+	_ = l2.release()
+}
+
+func TestLockStaleRecovery(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "daemon.lock")
+	// Simulate a stale lock from a crashed daemon: a PID file whose process is
+	// dead.
+	if err := os.WriteFile(path, []byte("4242\n"), 0o600); err != nil {
+		t.Fatalf("write stale lock: %v", err)
+	}
+	dead := func(int) bool { return false }
+	l, err := acquireLock(path, dead)
+	if err != nil {
+		t.Fatalf("stale-lock recovery failed: %v", err)
+	}
+	// The lock now records OUR pid, not the stale one.
+	data, _ := os.ReadFile(path)
+	if strings.TrimSpace(string(data)) != strconv.Itoa(os.Getpid()) {
+		t.Fatalf("reclaimed lock pid = %q, want %d", strings.TrimSpace(string(data)), os.Getpid())
+	}
+	_ = l.release()
+}
+
+func TestLockReleaseRemovesFile(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "daemon.lock")
+	l, err := acquireLock(path, func(int) bool { return true })
+	if err != nil {
+		t.Fatalf("acquireLock: %v", err)
+	}
+	if err := l.release(); err != nil {
+		t.Fatalf("release: %v", err)
+	}
+	if _, err := os.Stat(path); !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("lock file still present after release: %v", err)
+	}
+}
+
+func TestProcessAliveSelfAndDead(t *testing.T) {
+	if !osProcessAlive(os.Getpid()) {
+		t.Fatal("osProcessAlive(self) = false, want true")
+	}
+	// PID 0 / negative are never live.
+	if osProcessAlive(0) || osProcessAlive(-1) {
+		t.Fatal("osProcessAlive must reject non-positive pids")
+	}
+}

internal/daemon/lock_windows.go

@@ -0,0 +1,27 @@
+//go:build windows
+
+package daemon
+
+import "golang.org/x/sys/windows"
+
+// osProcessAlive reports whether pid is a live process on Windows. It opens the
+// process for limited query access; a successful open with a non-exited status
+// means the PID is live. x/sys is already a module dependency.
+func osProcessAlive(pid int) bool {
+	if pid <= 0 {
+		return false
+	}
+	handle, err := windows.OpenProcess(windows.PROCESS_QUERY_LIMITED_INFORMATION, false, uint32(pid))
+	if err != nil {
+		return false
+	}
+	defer windows.CloseHandle(handle)
+	var code uint32
+	if err := windows.GetExitCodeProcess(handle, &code); err != nil {
+		// Could not query; treat the open as proof of life (conservative: do not
+		// reclaim a lock we are unsure about).
+		return true
+	}
+	const stillActive = 259 // STILL_ACTIVE
+	return code == stillActive
+}

internal/daemon/paths.go

@@ -0,0 +1,42 @@
+package daemon
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// DefaultDir returns the per-user directory for the daemon's runtime files:
+// $XDG_RUNTIME_DIR/zero when set (a tmpfs owned by the user on Linux), otherwise
+// ~/.zero. Mirrors supervisor.js / config.js choosing a per-user runtime dir.
+func DefaultDir() (string, error) {
+	if rt := strings.TrimSpace(os.Getenv("XDG_RUNTIME_DIR")); rt != "" {
+		return filepath.Join(rt, "zero"), nil
+	}
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(home, ".zero"), nil
+}
+
+// Paths bundles the daemon's socket, lock, and status file paths.
+type Paths struct {
+	Socket string
+	Lock   string
+	Status string
+}
+
+// DefaultPaths returns the daemon control-socket, lock, and status file paths
+// under DefaultDir.
+func DefaultPaths() (Paths, error) {
+	dir, err := DefaultDir()
+	if err != nil {
+		return Paths{}, err
+	}
+	return Paths{
+		Socket: filepath.Join(dir, "daemon.sock"),
+		Lock:   filepath.Join(dir, "daemon.lock"),
+		Status: filepath.Join(dir, "daemon.status"),
+	}, nil
+}

internal/daemon/pool.go

@@ -0,0 +1,355 @@
+package daemon
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+	"time"
+)
+
+// Exit codes a worker may use to signal restart policy. Mirrors
+// reference-daemon-code-agent-js/worker-manager.js EXIT_TEMPFAIL/EXIT_PERMANENT.
+const (
+	// ExitTempfail asks for a retry after a fixed cool-off (transient failure).
+	ExitTempfail = 75
+	// ExitPermanent asks the daemon to STOP retrying this work (fatal).
+	ExitPermanent = 76
+)
+
+// defaultPoolSize, defaultMaxAttempts and defaultKillTimeout are used when a
+// PoolOptions field is left zero.
+const (
+	defaultPoolSize    = 4
+	defaultMaxAttempts = 5
+	defaultKillTimeout = 5 * time.Second
+)
+
+// ErrPoolDraining is returned by Run once the pool is shutting down.
+var ErrPoolDraining = errors.New("daemon: pool is draining")
+
+// ErrPermanent is returned when a worker exits ExitPermanent or the attempt cap
+// is exhausted; the request must not be retried.
+var ErrPermanent = errors.New("daemon: worker failed permanently")
+
+// WorkerSpec describes the worker to launch for one session attempt.
+type WorkerSpec struct {
+	Session string
+	Cwd     string
+	// Args are the per-session exec flags (e.g. --prompt ...), parsed by the CLI
+	// and appended after `exec` by the production launcher.
+	Args []string
+}
+
+// WorkerHandle is a launched worker process the pool supervises. The production
+// launcher wraps an exec.Cmd running `zero exec -i/-o stream-json`; tests inject
+// a fake. Stdout yields the worker's stream-json event lines.
+type WorkerHandle interface {
+	Stdout() Lines
+	// Wait blocks until the worker exits and returns its process exit code.
+	Wait() (int, error)
+	// Kill force-terminates the worker (used on drain timeout).
+	Kill() error
+	Pid() int
+}
+
+// Lines is a stream of stream-json output lines from a worker. Next returns the
+// next line and io-EOF-style ok=false when the stream ends.
+type Lines interface {
+	Next() (line string, ok bool, err error)
+}
+
+// Launcher spawns a worker for a single attempt. It must apply the sandbox/env
+// policy (the production launcher scrubs the re-entrancy markers so the worker
+// re-establishes its own sandbox — see newExecLauncher).
+type Launcher func(ctx context.Context, spec WorkerSpec) (WorkerHandle, error)
+
+// PoolOptions configures a Pool. Zero fields take documented defaults.
+type PoolOptions struct {
+	// Size is the max number of concurrent workers (lease slots). Sessions beyond
+	// this queue until a slot frees.
+	Size int
+	// Launcher spawns a worker. Required.
+	Launcher Launcher
+	// MaxAttempts caps the total attempts per request (first + retries). When
+	// exhausted, Run returns ErrPermanent (mirrors capping consecutive restarts).
+	MaxAttempts int
+	// KillTimeout bounds graceful termination before SIGKILL-equivalent on drain.
+	KillTimeout time.Duration
+	// Backoff returns the delay before retry attempt n (1-based crash count).
+	// Defaults to BackoffWithJitter; tests inject a deterministic function.
+	Backoff func(attempt int) time.Duration
+	// TempfailDelay is the cool-off after an ExitTempfail exit. Defaults to 30s.
+	TempfailDelay time.Duration
+	// Log, when set, receives one line per lifecycle event.
+	Log func(string)
+}
+
+// Pool is a bounded, self-healing worker pool. A crashed worker never takes down
+// the pool: Run retries on a fresh worker with backoff up to MaxAttempts, and an
+// ExitPermanent worker stops retries. Drain stops new work and kills stragglers.
+type Pool struct {
+	opts  PoolOptions
+	slots chan struct{}
+
+	mu       sync.Mutex
+	draining bool
+	active   map[int]WorkerHandle // pid -> handle, for drain/kill + status
+	nextID   int
+
+	drainOnce sync.Once
+	drained   chan struct{}
+}
+
+// workerStat tracks one in-flight request's restart count (local to Run).
+type workerStat struct {
+	id       int
+	restarts int
+}
+
+// NewPool builds a pool from opts, filling defaults.
+func NewPool(opts PoolOptions) (*Pool, error) {
+	if opts.Launcher == nil {
+		return nil, errors.New("daemon: pool requires a Launcher")
+	}
+	if opts.Size <= 0 {
+		opts.Size = defaultPoolSize
+	}
+	if opts.MaxAttempts <= 0 {
+		opts.MaxAttempts = defaultMaxAttempts
+	}
+	if opts.KillTimeout <= 0 {
+		opts.KillTimeout = defaultKillTimeout
+	}
+	if opts.TempfailDelay <= 0 {
+		opts.TempfailDelay = 30 * time.Second
+	}
+	if opts.Backoff == nil {
+		opts.Backoff = BackoffWithJitter
+	}
+	return &Pool{
+		opts:    opts,
+		slots:   make(chan struct{}, opts.Size),
+		active:  map[int]WorkerHandle{},
+		drained: make(chan struct{}),
+	}, nil
+}
+
+// Size returns the configured max concurrency.
+func (p *Pool) Size() int { return p.opts.Size }
+
+func (p *Pool) logf(format string, args ...any) {
+	if p.opts.Log != nil {
+		p.opts.Log(fmt.Sprintf(format, args...))
+	}
+}
+
+// acquire takes a lease slot, queuing until one frees or ctx is cancelled / the
+// pool drains.
+func (p *Pool) acquire(ctx context.Context) error {
+	p.mu.Lock()
+	draining := p.draining
+	p.mu.Unlock()
+	if draining {
+		return ErrPoolDraining
+	}
+	select {
+	case p.slots <- struct{}{}:
+		return nil
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-p.drained:
+		return ErrPoolDraining
+	}
+}
+
+func (p *Pool) release() { <-p.slots }
+
+// QueueDepth reports how many lease slots are currently in use.
+func (p *Pool) QueueDepth() int { return len(p.slots) }
+
+// Sink receives a worker's stream-json output lines for one request.
+type Sink interface {
+	Line(line string)
+}
+
+// Run leases a worker slot and dispatches spec to a worker, streaming its
+// stream-json lines to sink. It is at-least-once with bounded retries: a worker
+// that crashes (non-zero, non-permanent) is retried on a fresh worker after a
+// backoff; ExitPermanent or exhausting MaxAttempts returns ErrPermanent. Run
+// queues when all slots are busy. The returned int is the final worker exit code.
+func (p *Pool) Run(ctx context.Context, spec WorkerSpec, sink Sink) (int, error) {
+	if err := p.acquire(ctx); err != nil {
+		return 0, err
+	}
+	defer p.release()
+
+	// Lease hook: a sink that tracks queue->running state is notified the instant
+	// a worker slot is leased (mirrors lease.js acquiring a worker for a session).
+	if s, ok := sink.(interface{ Started() }); ok {
+		s.Started()
+	}
+
+	stat := p.newStat()
+	var lastErr error
+	for attempt := 1; attempt <= p.opts.MaxAttempts; attempt++ {
+		if p.isDraining() {
+			return 0, ErrPoolDraining
+		}
+		code, err := p.runOnce(ctx, stat.id, spec, sink)
+		switch {
+		case err != nil:
+			lastErr = err
+			if ctx.Err() != nil {
+				return 0, ctx.Err()
+			}
+			p.logf("worker %d launch/run error: %v", stat.id, err)
+		case code == 0:
+			return 0, nil // clean success
+		case code == ExitPermanent:
+			p.logf("worker %d exited permanently (code=%d) — not retrying", stat.id, code)
+			return code, ErrPermanent
+		case code == ExitTempfail:
+			lastErr = fmt.Errorf("worker %d tempfail (code=%d)", stat.id, code)
+			p.logf("worker %d tempfail — retry after %s", stat.id, p.opts.TempfailDelay)
+			if !p.sleep(ctx, p.opts.TempfailDelay) {
+				return 0, ctx.Err()
+			}
+			continue // tempfail retries do not count against the crash backoff
+		default:
+			lastErr = fmt.Errorf("worker %d exited code=%d", stat.id, code)
+		}
+
+		if attempt == p.opts.MaxAttempts {
+			break
+		}
+		stat.restarts++
+		delay := p.opts.Backoff(stat.restarts)
+		p.logf("worker %d restart %d after backoff %s", stat.id, stat.restarts, delay)
+		if !p.sleep(ctx, delay) {
+			return 0, ctx.Err()
+		}
+	}
+	if lastErr == nil {
+		lastErr = ErrPermanent
+	}
+	return ExitPermanent, fmt.Errorf("%w: %v", ErrPermanent, lastErr)
+}
+
+// runOnce launches a single worker, pumps its output to sink, and returns its
+// exit code. The worker handle is tracked so Drain can kill it.
+func (p *Pool) runOnce(ctx context.Context, id int, spec WorkerSpec, sink Sink) (int, error) {
+	handle, err := p.opts.Launcher(ctx, spec)
+	if err != nil {
+		return 0, err
+	}
+	p.track(handle)
+	defer p.untrack(handle)
+
+	// Pump stdout lines until the stream ends.
+	lines := handle.Stdout()
+	for {
+		line, ok, lerr := lines.Next()
+		if lerr != nil {
+			break
+		}
+		if !ok {
+			break
+		}
+		if sink != nil {
+			sink.Line(line)
+		}
+	}
+	return handle.Wait()
+}
+
+func (p *Pool) newStat() *workerStat {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	p.nextID++
+	return &workerStat{id: p.nextID}
+}
+
+func (p *Pool) track(h WorkerHandle) {
+	p.mu.Lock()
+	p.active[h.Pid()] = h
+	p.mu.Unlock()
+}
+
+func (p *Pool) untrack(h WorkerHandle) {
+	p.mu.Lock()
+	delete(p.active, h.Pid())
+	p.mu.Unlock()
+}
+
+func (p *Pool) isDraining() bool {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	return p.draining
+}
+
+// sleep waits d, returning false if ctx is cancelled first. A non-positive d
+// returns immediately.
+func (p *Pool) sleep(ctx context.Context, d time.Duration) bool {
+	if d <= 0 {
+		return ctx.Err() == nil
+	}
+	timer := time.NewTimer(d)
+	defer timer.Stop()
+	select {
+	case <-timer.C:
+		return true
+	case <-ctx.Done():
+		return false
+	}
+}
+
+// Drain stops accepting new work, gives in-flight workers a grace window
+// (KillTimeout) to finish on their own, then force-kills any straggler. It
+// returns as soon as the pool is idle (graceful) or the window elapses. Safe to
+// call once; subsequent calls are no-ops.
+func (p *Pool) Drain() {
+	p.drainOnce.Do(func() {
+		p.mu.Lock()
+		p.draining = true
+		p.mu.Unlock()
+		close(p.drained)
+
+		// Grace window: poll until idle or the deadline.
+		deadline := time.Now().Add(p.opts.KillTimeout)
+		for time.Now().Before(deadline) {
+			p.mu.Lock()
+			n := len(p.active)
+			p.mu.Unlock()
+			if n == 0 {
+				return // all workers drained gracefully
+			}
+			time.Sleep(5 * time.Millisecond)
+		}
+
+		// Timed out: force-kill remaining workers.
+		p.mu.Lock()
+		handles := make([]WorkerHandle, 0, len(p.active))
+		for _, h := range p.active {
+			handles = append(handles, h)
+		}
+		p.mu.Unlock()
+		for _, h := range handles {
+			p.logf("drain: killing straggler worker pid=%d", h.Pid())
+			_ = h.Kill()
+		}
+	})
+}
+
+// WorkerStats returns a snapshot of the currently-active (busy) workers, bounded
+// by the pool size. The on-demand pool keeps no idle workers, so an empty result
+// means the pool is idle.
+func (p *Pool) WorkerStats() []WorkerStatus {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	out := make([]WorkerStatus, 0, len(p.active))
+	for pid := range p.active {
+		out = append(out, WorkerStatus{PID: pid, State: "busy"})
+	}
+	return out
+}

internal/daemon/pool_test.go

@@ -0,0 +1,248 @@
+package daemon
+
+import (
+	"context"
+	"errors"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+// --- test doubles ---------------------------------------------------------
+
+type fakeLines struct {
+	lines []string
+	i     int
+}
+
+func (f *fakeLines) Next() (string, bool, error) {
+	if f.i >= len(f.lines) {
+		return "", false, nil
+	}
+	l := f.lines[f.i]
+	f.i++
+	return l, true, nil
+}
+
+type fakeWorker struct {
+	pid      int
+	out      []string
+	exitCode int
+	killed   int32
+	waitCh   chan struct{} // when non-nil, Wait blocks until closed (drain tests)
+}
+
+func (w *fakeWorker) Stdout() Lines { return &fakeLines{lines: w.out} }
+func (w *fakeWorker) Wait() (int, error) {
+	if w.waitCh != nil {
+		<-w.waitCh
+	}
+	return w.exitCode, nil
+}
+func (w *fakeWorker) Kill() error {
+	atomic.StoreInt32(&w.killed, 1)
+	if w.waitCh != nil {
+		select {
+		case <-w.waitCh:
+		default:
+			close(w.waitCh)
+		}
+	}
+	return nil
+}
+func (w *fakeWorker) Pid() int { return w.pid }
+
+// seqLauncher hands out the given workers in order, then errors.
+func seqLauncher(workers ...*fakeWorker) (Launcher, *int32) {
+	var calls int32
+	l := func(_ context.Context, _ WorkerSpec) (WorkerHandle, error) {
+		n := atomic.AddInt32(&calls, 1)
+		idx := int(n) - 1
+		if idx >= len(workers) {
+			return nil, errors.New("no more fake workers")
+		}
+		return workers[idx], nil
+	}
+	return l, &calls
+}
+
+type collectSink struct {
+	mu    sync.Mutex
+	lines []string
+}
+
+func (c *collectSink) Line(line string) {
+	c.mu.Lock()
+	c.lines = append(c.lines, line)
+	c.mu.Unlock()
+}
+
+// --- tests ----------------------------------------------------------------
+
+func TestPoolRunStreamsAndSucceeds(t *testing.T) {
+	launcher, calls := seqLauncher(&fakeWorker{pid: 1, out: []string{"a", "b"}, exitCode: 0})
+	pool, err := NewPool(PoolOptions{Size: 2, Launcher: launcher})
+	if err != nil {
+		t.Fatalf("NewPool: %v", err)
+	}
+	sink := &collectSink{}
+	code, err := pool.Run(context.Background(), WorkerSpec{Session: "s"}, sink)
+	if err != nil || code != 0 {
+		t.Fatalf("Run = (%d,%v), want (0,nil)", code, err)
+	}
+	if len(sink.lines) != 2 || sink.lines[0] != "a" || sink.lines[1] != "b" {
+		t.Fatalf("sink lines = %v, want [a b]", sink.lines)
+	}
+	if *calls != 1 {
+		t.Fatalf("launcher calls = %d, want 1", *calls)
+	}
+}
+
+func TestPoolRunRetriesWithBackoff(t *testing.T) {
+	launcher, calls := seqLauncher(
+		&fakeWorker{pid: 1, exitCode: 1},                      // crash
+		&fakeWorker{pid: 2, exitCode: 1},                      // crash
+		&fakeWorker{pid: 3, exitCode: 0, out: []string{"ok"}}, // success
+	)
+	var backoffArgs []int
+	pool, _ := NewPool(PoolOptions{
+		Size: 1, Launcher: launcher, MaxAttempts: 5,
+		Backoff: func(attempt int) time.Duration { backoffArgs = append(backoffArgs, attempt); return 0 },
+	})
+	sink := &collectSink{}
+	code, err := pool.Run(context.Background(), WorkerSpec{Session: "s"}, sink)
+	if err != nil || code != 0 {
+		t.Fatalf("Run = (%d,%v), want (0,nil)", code, err)
+	}
+	if *calls != 3 {
+		t.Fatalf("launcher calls = %d, want 3 (2 crashes + success)", *calls)
+	}
+	// Backoff invoked between attempts with an increasing 1-based restart count.
+	if len(backoffArgs) != 2 || backoffArgs[0] != 1 || backoffArgs[1] != 2 {
+		t.Fatalf("backoff attempts = %v, want [1 2]", backoffArgs)
+	}
+}
+
+func TestPoolRunPermanentStopsImmediately(t *testing.T) {
+	launcher, calls := seqLauncher(&fakeWorker{pid: 1, exitCode: ExitPermanent})
+	pool, _ := NewPool(PoolOptions{Size: 1, Launcher: launcher, Backoff: func(int) time.Duration { return 0 }})
+	code, err := pool.Run(context.Background(), WorkerSpec{Session: "s"}, &collectSink{})
+	if !errors.Is(err, ErrPermanent) {
+		t.Fatalf("Run err = %v, want ErrPermanent", err)
+	}
+	if code != ExitPermanent {
+		t.Fatalf("Run code = %d, want %d", code, ExitPermanent)
+	}
+	if *calls != 1 {
+		t.Fatalf("permanent exit must not retry; launcher calls = %d, want 1", *calls)
+	}
+}
+
+func TestPoolRunCapExhausted(t *testing.T) {
+	launcher, calls := seqLauncher(
+		&fakeWorker{pid: 1, exitCode: 1},
+		&fakeWorker{pid: 2, exitCode: 1},
+		&fakeWorker{pid: 3, exitCode: 1},
+	)
+	pool, _ := NewPool(PoolOptions{Size: 1, Launcher: launcher, MaxAttempts: 3, Backoff: func(int) time.Duration { return 0 }})
+	_, err := pool.Run(context.Background(), WorkerSpec{Session: "s"}, &collectSink{})
+	if !errors.Is(err, ErrPermanent) {
+		t.Fatalf("Run err = %v, want ErrPermanent after cap", err)
+	}
+	if *calls != 3 {
+		t.Fatalf("launcher calls = %d, want 3 (== MaxAttempts)", *calls)
+	}
+}
+
+func TestPoolRunTempfailRetries(t *testing.T) {
+	launcher, calls := seqLauncher(
+		&fakeWorker{pid: 1, exitCode: ExitTempfail},
+		&fakeWorker{pid: 2, exitCode: 0, out: []string{"ok"}},
+	)
+	pool, _ := NewPool(PoolOptions{Size: 1, Launcher: launcher, TempfailDelay: time.Millisecond})
+	code, err := pool.Run(context.Background(), WorkerSpec{Session: "s"}, &collectSink{})
+	if err != nil || code != 0 {
+		t.Fatalf("Run = (%d,%v), want (0,nil)", code, err)
+	}
+	if *calls != 2 {
+		t.Fatalf("launcher calls = %d, want 2 (tempfail + success)", *calls)
+	}
+}
+
+func TestPoolQueuesWhenFull(t *testing.T) {
+	block := make(chan struct{})
+	first := &fakeWorker{pid: 1, waitCh: block}
+	second := &fakeWorker{pid: 2, exitCode: 0}
+	launcher, _ := seqLauncher(first, second)
+	pool, _ := NewPool(PoolOptions{Size: 1, Launcher: launcher})
+
+	started := make(chan struct{})
+	go func() {
+		close(started)
+		_, _ = pool.Run(context.Background(), WorkerSpec{Session: "a"}, &collectSink{})
+	}()
+	<-started
+	// Wait until the first run holds the only slot.
+	waitFor(t, func() bool { return pool.QueueDepth() == 1 })
+
+	secondDone := make(chan struct{})
+	go func() {
+		_, _ = pool.Run(context.Background(), WorkerSpec{Session: "b"}, &collectSink{})
+		close(secondDone)
+	}()
+	// The second run must NOT complete while the slot is held.
+	select {
+	case <-secondDone:
+		t.Fatal("second run completed while the only slot was busy (no queueing)")
+	case <-time.After(50 * time.Millisecond):
+	}
+	// Free the slot; the queued run now proceeds.
+	close(block)
+	select {
+	case <-secondDone:
+	case <-time.After(2 * time.Second):
+		t.Fatal("queued run did not proceed after slot freed")
+	}
+}
+
+func TestPoolDrainKillsStraggler(t *testing.T) {
+	block := make(chan struct{})
+	straggler := &fakeWorker{pid: 1, waitCh: block}
+	launcher, _ := seqLauncher(straggler)
+	pool, _ := NewPool(PoolOptions{Size: 1, Launcher: launcher, MaxAttempts: 1, KillTimeout: 10 * time.Millisecond})
+
+	runDone := make(chan struct{})
+	go func() {
+		_, _ = pool.Run(context.Background(), WorkerSpec{Session: "a"}, &collectSink{})
+		close(runDone)
+	}()
+	waitFor(t, func() bool { return pool.QueueDepth() == 1 })
+
+	pool.Drain() // KillTimeout elapses, straggler is force-killed
+	if atomic.LoadInt32(&straggler.killed) != 1 {
+		t.Fatal("Drain must kill a straggler still running after KillTimeout")
+	}
+	select {
+	case <-runDone:
+	case <-time.After(2 * time.Second):
+		t.Fatal("run did not finish after drain kill")
+	}
+
+	// A new Run after drain is refused.
+	if _, err := pool.Run(context.Background(), WorkerSpec{Session: "b"}, &collectSink{}); !errors.Is(err, ErrPoolDraining) {
+		t.Fatalf("Run after drain err = %v, want ErrPoolDraining", err)
+	}
+}
+
+func waitFor(t *testing.T, cond func() bool) {
+	t.Helper()
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		if cond() {
+			return
+		}
+		time.Sleep(time.Millisecond)
+	}
+	t.Fatal("condition not met within timeout")
+}

internal/daemon/protocol.go

@@ -0,0 +1,184 @@
+// Package daemon implements zero's long-running daemon/server mode: a local
+// control server that supervises a pool of headless `zero exec` worker processes
+// and routes multiple agent sessions to them over an owner-only local socket.
+//
+// It reuses zero's existing building blocks rather than inventing new ones:
+//   - internal/background : child-process group setup + cross-platform terminate.
+//   - internal/streamjson : the line-based agent event protocol on worker stdio.
+//   - internal/cli (exec) : a worker is a `zero exec -i/-o stream-json` process.
+//
+// The control plane (this file) is a small framed codec mirrored from the
+// reference daemon's protocol.js: a 4-byte big-endian length prefix, a 1-byte
+// frame kind, then a JSON control payload, with a 1 MiB frame cap and a
+// version-negotiation handshake. The agent event stream itself stays stream-json.
+package daemon
+
+import (
+	"encoding/binary"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+)
+
+// Wire constants. Mirrors reference-daemon-code-agent-js/protocol.js
+// (FRAME_DATA/FRAME_CTRL, HEADER_SIZE, MAX_FRAME_SIZE, PROTO_VERSION).
+const (
+	// ProtoVersion is the control-protocol version advertised in the handshake.
+	ProtoVersion = 1
+	// MaxFrameSize caps a single control frame payload at 1 MiB. A larger
+	// advertised length is rejected before any allocation (fail closed).
+	MaxFrameSize = 1 << 20
+	// frameHeaderSize is 4 bytes big-endian length + 1 byte kind.
+	frameHeaderSize = 5
+)
+
+// FrameKind tags a frame's payload. Mirrors protocol.js FRAME_DATA/FRAME_CTRL.
+type FrameKind uint8
+
+const (
+	// KindData carries an opaque payload (e.g. a stream-json line). Reserved for
+	// future use; the control plane uses KindCtrl.
+	KindData FrameKind = 0
+	// KindCtrl carries a JSON-encoded control message (see Ctrl).
+	KindCtrl FrameKind = 1
+)
+
+// ErrFrameTooLarge is returned when a frame's advertised payload length exceeds
+// MaxFrameSize. The reader rejects it without allocating the buffer.
+var ErrFrameTooLarge = errors.New("daemon: control frame exceeds size cap")
+
+// ErrUnknownFrameKind is returned for a frame whose kind byte is not recognized.
+var ErrUnknownFrameKind = errors.New("daemon: unknown control frame kind")
+
+// WriteFrame writes a single framed message: [uint32BE len][uint8 kind][payload].
+// It rejects an over-cap payload before writing anything so a buggy/hostile caller
+// cannot emit a frame a conforming reader would refuse.
+func WriteFrame(w io.Writer, kind FrameKind, payload []byte) error {
+	if len(payload) > MaxFrameSize {
+		return fmt.Errorf("%w (%d > %d)", ErrFrameTooLarge, len(payload), MaxFrameSize)
+	}
+	header := make([]byte, frameHeaderSize)
+	binary.BigEndian.PutUint32(header[:4], uint32(len(payload)))
+	header[4] = byte(kind)
+	if _, err := w.Write(header); err != nil {
+		return err
+	}
+	if len(payload) == 0 {
+		return nil
+	}
+	_, err := w.Write(payload)
+	return err
+}
+
+// ReadFrame reads a single framed message. It validates the advertised length
+// against MaxFrameSize BEFORE allocating, so an oversize or hostile frame is
+// rejected (ErrFrameTooLarge) rather than triggering a huge allocation. An
+// unrecognized kind byte yields ErrUnknownFrameKind after the payload is drained
+// so the stream stays in sync.
+func ReadFrame(r io.Reader) (FrameKind, []byte, error) {
+	header := make([]byte, frameHeaderSize)
+	if _, err := io.ReadFull(r, header); err != nil {
+		return 0, nil, err
+	}
+	length := binary.BigEndian.Uint32(header[:4])
+	if length > MaxFrameSize {
+		return 0, nil, fmt.Errorf("%w (%d > %d)", ErrFrameTooLarge, length, MaxFrameSize)
+	}
+	kind := FrameKind(header[4])
+	payload := make([]byte, length)
+	if length > 0 {
+		if _, err := io.ReadFull(r, payload); err != nil {
+			return 0, nil, err
+		}
+	}
+	if kind != KindData && kind != KindCtrl {
+		return kind, nil, ErrUnknownFrameKind
+	}
+	return kind, payload, nil
+}
+
+// CtrlType is the discriminator for a control message.
+type CtrlType string
+
+const (
+	// CtrlHello is the client's opening handshake; Version is the highest control
+	// version it speaks.
+	CtrlHello CtrlType = "hello"
+	// CtrlHelloOK is the daemon's handshake reply with the negotiated Version.
+	CtrlHelloOK CtrlType = "hello_ok"
+	// CtrlRun asks the daemon to create/route a session and stream its output.
+	CtrlRun CtrlType = "run"
+	// CtrlAttach asks the daemon to attach the client to a running session's stream.
+	CtrlAttach CtrlType = "attach"
+	// CtrlStatus requests daemon/worker/session status.
+	CtrlStatus CtrlType = "status"
+	// CtrlStatusResult carries the status payload (see StatusReport in Status).
+	CtrlStatusResult CtrlType = "status_result"
+	// CtrlData carries one stream-json line of agent output back to the client.
+	CtrlData CtrlType = "data"
+	// CtrlAck acknowledges receipt/dispatch of a request (at-least-once dispatch).
+	CtrlAck CtrlType = "ack"
+	// CtrlEnd marks the end of a session's stream.
+	CtrlEnd CtrlType = "end"
+	// CtrlShutdown asks the daemon to drain and stop.
+	CtrlShutdown CtrlType = "shutdown"
+	// CtrlError carries a human-readable error for the client.
+	CtrlError CtrlType = "error"
+)
+
+// Ctrl is a control message carried in a KindCtrl frame as JSON. Unused fields
+// are omitted so frames stay small.
+type Ctrl struct {
+	Type    CtrlType `json:"type"`
+	Version int      `json:"version,omitempty"`
+	Session string   `json:"session,omitempty"`
+	Cwd     string   `json:"cwd,omitempty"`
+	Args    []string `json:"args,omitempty"`
+	Prompt  string   `json:"prompt,omitempty"`
+	// Line is one stream-json event line (for CtrlData).
+	Line string `json:"line,omitempty"`
+	// Message is a human-readable detail (for CtrlError / CtrlAck).
+	Message string `json:"message,omitempty"`
+	// Status is populated on CtrlStatusResult.
+	Status *StatusReport `json:"status,omitempty"`
+}
+
+// WriteControl marshals a control message into a KindCtrl frame.
+func WriteControl(w io.Writer, msg Ctrl) error {
+	payload, err := json.Marshal(msg)
+	if err != nil {
+		return err
+	}
+	return WriteFrame(w, KindCtrl, payload)
+}
+
+// ReadControl reads the next frame and decodes it as a control message. A
+// non-control frame yields ErrUnknownFrameKind so the caller fails closed.
+func ReadControl(r io.Reader) (Ctrl, error) {
+	kind, payload, err := ReadFrame(r)
+	if err != nil {
+		return Ctrl{}, err
+	}
+	if kind != KindCtrl {
+		return Ctrl{}, ErrUnknownFrameKind
+	}
+	var msg Ctrl
+	if err := json.Unmarshal(payload, &msg); err != nil {
+		return Ctrl{}, fmt.Errorf("daemon: decode control message: %w", err)
+	}
+	return msg, nil
+}
+
+// NegotiateVersion picks the protocol version both ends can speak: the lower of
+// the client's advertised version and ProtoVersion. A non-positive client
+// version is invalid and yields ok=false so the daemon can reject the connection.
+func NegotiateVersion(clientVersion int) (int, bool) {
+	if clientVersion <= 0 {
+		return 0, false
+	}
+	if clientVersion < ProtoVersion {
+		return clientVersion, true
+	}
+	return ProtoVersion, true
+}

internal/daemon/protocol_test.go

@@ -0,0 +1,120 @@
+package daemon
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"io"
+	"strings"
+	"testing"
+)
+
+func TestFrameRoundTrip(t *testing.T) {
+	var buf bytes.Buffer
+	payloads := [][]byte{[]byte("hello"), {}, []byte(strings.Repeat("x", 4096))}
+	for _, p := range payloads {
+		if err := WriteFrame(&buf, KindCtrl, p); err != nil {
+			t.Fatalf("WriteFrame: %v", err)
+		}
+	}
+	for i, want := range payloads {
+		kind, got, err := ReadFrame(&buf)
+		if err != nil {
+			t.Fatalf("ReadFrame[%d]: %v", i, err)
+		}
+		if kind != KindCtrl {
+			t.Fatalf("frame[%d] kind = %d, want KindCtrl", i, kind)
+		}
+		if !bytes.Equal(got, want) {
+			t.Fatalf("frame[%d] payload = %q, want %q", i, got, want)
+		}
+	}
+}
+
+func TestControlRoundTrip(t *testing.T) {
+	var buf bytes.Buffer
+	msg := Ctrl{Type: CtrlRun, Session: "s1", Cwd: "/tmp", Args: []string{"--prompt", "hi"}}
+	if err := WriteControl(&buf, msg); err != nil {
+		t.Fatalf("WriteControl: %v", err)
+	}
+	got, err := ReadControl(&buf)
+	if err != nil {
+		t.Fatalf("ReadControl: %v", err)
+	}
+	if got.Type != CtrlRun || got.Session != "s1" || got.Cwd != "/tmp" || len(got.Args) != 2 {
+		t.Fatalf("round-trip mismatch: %+v", got)
+	}
+}
+
+func TestWriteFrameRejectsOversize(t *testing.T) {
+	var buf bytes.Buffer
+	err := WriteFrame(&buf, KindCtrl, make([]byte, MaxFrameSize+1))
+	if !errors.Is(err, ErrFrameTooLarge) {
+		t.Fatalf("WriteFrame oversize err = %v, want ErrFrameTooLarge", err)
+	}
+	if buf.Len() != 0 {
+		t.Fatalf("oversize WriteFrame must not emit any bytes, wrote %d", buf.Len())
+	}
+}
+
+func TestReadFrameRejectsOversizeBeforeAlloc(t *testing.T) {
+	// A header advertising a 4 GiB payload must be rejected without reading or
+	// allocating that payload.
+	header := make([]byte, frameHeaderSize)
+	binary.BigEndian.PutUint32(header[:4], MaxFrameSize+1)
+	header[4] = byte(KindCtrl)
+	_, _, err := ReadFrame(bytes.NewReader(header))
+	if !errors.Is(err, ErrFrameTooLarge) {
+		t.Fatalf("ReadFrame oversize err = %v, want ErrFrameTooLarge", err)
+	}
+}
+
+func TestReadFrameUnknownKind(t *testing.T) {
+	var buf bytes.Buffer
+	// Hand-write a frame with an unknown kind byte (7) and a small payload.
+	header := make([]byte, frameHeaderSize)
+	binary.BigEndian.PutUint32(header[:4], 2)
+	header[4] = 7
+	buf.Write(header)
+	buf.Write([]byte("ab"))
+	_, _, err := ReadFrame(&buf)
+	if !errors.Is(err, ErrUnknownFrameKind) {
+		t.Fatalf("unknown kind err = %v, want ErrUnknownFrameKind", err)
+	}
+}
+
+func TestReadFrameTruncated(t *testing.T) {
+	// Header promises 10 bytes but only 3 follow → unexpected EOF.
+	var buf bytes.Buffer
+	header := make([]byte, frameHeaderSize)
+	binary.BigEndian.PutUint32(header[:4], 10)
+	header[4] = byte(KindCtrl)
+	buf.Write(header)
+	buf.Write([]byte("abc"))
+	_, _, err := ReadFrame(&buf)
+	if err == nil || errors.Is(err, ErrFrameTooLarge) {
+		t.Fatalf("truncated frame err = %v, want a read error", err)
+	}
+	if !errors.Is(err, io.ErrUnexpectedEOF) {
+		t.Fatalf("truncated frame err = %v, want io.ErrUnexpectedEOF", err)
+	}
+}
+
+func TestNegotiateVersion(t *testing.T) {
+	cases := []struct {
+		client int
+		want   int
+		wantOK bool
+	}{
+		{client: 1, want: 1, wantOK: true},
+		{client: 99, want: ProtoVersion, wantOK: true}, // clamp down to ours
+		{client: 0, want: 0, wantOK: false},
+		{client: -3, want: 0, wantOK: false},
+	}
+	for _, tc := range cases {
+		got, ok := NegotiateVersion(tc.client)
+		if got != tc.want || ok != tc.wantOK {
+			t.Fatalf("NegotiateVersion(%d) = (%d,%v), want (%d,%v)", tc.client, got, ok, tc.want, tc.wantOK)
+		}
+	}
+}

internal/daemon/remote/auth.go

@@ -0,0 +1,169 @@
+// Package remote adds an OPT-IN, TLS-only network bridge on top of zero's local
+// daemon (internal/daemon). It lets a remote client drive the SAME daemon
+// SessionManager/Pool over the network, behind bearer-token authentication and a
+// protocol-version floor. The local Unix-socket daemon is unchanged and remains
+// the default; nothing here activates unless `zero daemon serve-remote` is run.
+//
+// Security (fail closed):
+//   - TLS is mandatory; the bridge refuses to serve without a cert/key.
+//   - A connection is authenticated BEFORE any control frame is dispatched; a
+//     failed/absent token closes the connection (after a small backoff) and no
+//     session frame is ever processed.
+//   - Tokens are compared in constant time and are never logged.
+//   - The control-frame size cap and version negotiation from internal/daemon are
+//     reused unchanged; oversize/old-version handshakes are rejected.
+//   - A remote-driven session runs through the same daemon dispatch, so it stays
+//     under the same sandbox + risk model — remote never bypasses local controls.
+package remote
+
+import (
+	"crypto/subtle"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/Gitlawb/zero/internal/daemon"
+)
+
+// Env vars the bridge reads for its bearer token.
+const (
+	EnvToken     = "ZERO_DAEMON_REMOTE_TOKEN"
+	EnvTokenFile = "ZERO_DAEMON_REMOTE_TOKEN_FILE"
+)
+
+// ErrUnauthorized is returned when a token does not match.
+var ErrUnauthorized = errors.New("remote: unauthorized")
+
+// Authenticator verifies a bearer token presented by a remote client.
+type Authenticator interface {
+	Authenticate(token string) error
+}
+
+// TokenAuthenticator compares a presented token against a fixed secret in
+// constant time.
+type TokenAuthenticator struct {
+	token string
+}
+
+// NewTokenAuthenticator builds a token authenticator, refusing an empty secret
+// (fail closed — a bridge must never accept everyone).
+func NewTokenAuthenticator(token string) (*TokenAuthenticator, error) {
+	token = strings.TrimSpace(token)
+	if token == "" {
+		return nil, errors.New("remote: a non-empty auth token is required")
+	}
+	return &TokenAuthenticator{token: token}, nil
+}
+
+// Authenticate reports nil when token matches the configured secret.
+func (a *TokenAuthenticator) Authenticate(token string) error {
+	if subtle.ConstantTimeCompare([]byte(token), []byte(a.token)) == 1 {
+		return nil
+	}
+	return ErrUnauthorized
+}
+
+// TokenFromEnv resolves the bridge token from EnvToken, or a file named by
+// EnvTokenFile. It never logs the token.
+func TokenFromEnv() (string, error) {
+	if t := strings.TrimSpace(os.Getenv(EnvToken)); t != "" {
+		return t, nil
+	}
+	if file := strings.TrimSpace(os.Getenv(EnvTokenFile)); file != "" {
+		data, err := os.ReadFile(file)
+		if err != nil {
+			return "", fmt.Errorf("remote: read token file: %w", err)
+		}
+		t := strings.TrimSpace(string(data))
+		if t == "" {
+			return "", errors.New("remote: token file is empty")
+		}
+		return t, nil
+	}
+	return "", fmt.Errorf("remote: set %s or %s", EnvToken, EnvTokenFile)
+}
+
+// Attestation is an optional post-token hook (e.g. workload attestation). The
+// default is a no-op; a deployment can supply a stricter implementation.
+type Attestation interface {
+	Verify(meta map[string]string) error
+}
+
+type noopAttestation struct{}
+
+func (noopAttestation) Verify(map[string]string) error { return nil }
+
+// Connection modes negotiated in the auth handshake. The default (empty) is a
+// daemon session, preserving the original behavior; "bundle" requests a one-shot
+// git-bundle upload instead of a session.
+const (
+	ModeSession = "session"
+	ModeBundle  = "bundle"
+)
+
+// authRequest is the first frame a remote client sends (before the daemon
+// hello). Token is never logged.
+type authRequest struct {
+	Token   string            `json:"token"`
+	Version int               `json:"version"`
+	Meta    map[string]string `json:"meta,omitempty"`
+	// Mode selects the connection's purpose: "" / "session" => a daemon session
+	// (default), "bundle" => a git-bundle upload. Unknown modes are rejected.
+	Mode string `json:"mode,omitempty"`
+}
+
+// authResponse is the bridge's reply to the auth handshake.
+type authResponse struct {
+	OK      bool   `json:"ok"`
+	Version int    `json:"version,omitempty"`
+	Message string `json:"message,omitempty"`
+}
+
+func writeAuthRequest(w io.Writer, req authRequest) error {
+	payload, err := json.Marshal(req)
+	if err != nil {
+		return err
+	}
+	return daemon.WriteFrame(w, daemon.KindCtrl, payload)
+}
+
+func readAuthRequest(r io.Reader) (authRequest, error) {
+	kind, payload, err := daemon.ReadFrame(r)
+	if err != nil {
+		return authRequest{}, err
+	}
+	if kind != daemon.KindCtrl {
+		return authRequest{}, errors.New("remote: expected auth frame")
+	}
+	var req authRequest
+	if err := json.Unmarshal(payload, &req); err != nil {
+		return authRequest{}, fmt.Errorf("remote: decode auth request: %w", err)
+	}
+	return req, nil
+}
+
+func writeAuthResponse(w io.Writer, resp authResponse) error {
+	payload, err := json.Marshal(resp)
+	if err != nil {
+		return err
+	}
+	return daemon.WriteFrame(w, daemon.KindCtrl, payload)
+}
+
+func readAuthResponse(r io.Reader) (authResponse, error) {
+	kind, payload, err := daemon.ReadFrame(r)
+	if err != nil {
+		return authResponse{}, err
+	}
+	if kind != daemon.KindCtrl {
+		return authResponse{}, errors.New("remote: expected auth response frame")
+	}
+	var resp authResponse
+	if err := json.Unmarshal(payload, &resp); err != nil {
+		return authResponse{}, fmt.Errorf("remote: decode auth response: %w", err)
+	}
+	return resp, nil
+}

internal/daemon/remote/auth_test.go

@@ -0,0 +1,67 @@
+package remote
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestTokenAuthenticator(t *testing.T) {
+	if _, err := NewTokenAuthenticator("  "); err == nil {
+		t.Fatal("empty token must be rejected (fail closed)")
+	}
+	a, err := NewTokenAuthenticator("s3cret")
+	if err != nil {
+		t.Fatalf("NewTokenAuthenticator: %v", err)
+	}
+	if err := a.Authenticate("s3cret"); err != nil {
+		t.Fatalf("matching token should authenticate: %v", err)
+	}
+	if err := a.Authenticate("wrong"); !errors.Is(err, ErrUnauthorized) {
+		t.Fatalf("mismatch err = %v, want ErrUnauthorized", err)
+	}
+	if err := a.Authenticate(""); !errors.Is(err, ErrUnauthorized) {
+		t.Fatalf("empty presented token err = %v, want ErrUnauthorized", err)
+	}
+}
+
+func TestTokenFromEnv(t *testing.T) {
+	// Clear both so the no-config path errors.
+	t.Setenv(EnvToken, "")
+	t.Setenv(EnvTokenFile, "")
+	if _, err := TokenFromEnv(); err == nil {
+		t.Fatal("TokenFromEnv with neither var set must error")
+	}
+	// Direct env.
+	t.Setenv(EnvToken, "from-env")
+	if tok, err := TokenFromEnv(); err != nil || tok != "from-env" {
+		t.Fatalf("TokenFromEnv(env) = %q, %v", tok, err)
+	}
+	// File (env takes precedence, so clear env first).
+	t.Setenv(EnvToken, "")
+	file := filepath.Join(t.TempDir(), "tok")
+	if err := os.WriteFile(file, []byte("  from-file\n"), 0o600); err != nil {
+		t.Fatalf("write token file: %v", err)
+	}
+	t.Setenv(EnvTokenFile, file)
+	if tok, err := TokenFromEnv(); err != nil || tok != "from-file" {
+		t.Fatalf("TokenFromEnv(file) = %q, %v", tok, err)
+	}
+	// Empty file fails closed.
+	if err := os.WriteFile(file, []byte("   \n"), 0o600); err != nil {
+		t.Fatalf("rewrite token file: %v", err)
+	}
+	if _, err := TokenFromEnv(); err == nil {
+		t.Fatal("empty token file must error")
+	}
+}
+
+func TestServerTLSConfigRequiresCertKey(t *testing.T) {
+	if _, err := ServerTLSConfig("", ""); err == nil {
+		t.Fatal("ServerTLSConfig must require a cert and key (TLS mandatory)")
+	}
+	if _, err := ServerTLSConfig("/nope/cert.pem", "/nope/key.pem"); err == nil {
+		t.Fatal("ServerTLSConfig must error on unreadable cert/key")
+	}
+}

internal/daemon/remote/bridge.go

@@ -0,0 +1,255 @@
+package remote
+
+import (
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"net"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/daemon"
+)
+
+const (
+	defaultMaxConnections   = 32
+	defaultHandshakeTimeout = 10 * time.Second
+	defaultAuthFailDelay    = 250 * time.Millisecond
+	// defaultMaxBundleBytes caps a single uploaded git bundle (256 MiB) so a
+	// remote peer cannot exhaust the host's disk.
+	defaultMaxBundleBytes = 256 << 20
+)
+
+// Bridge serves authenticated remote connections and drives the local daemon's
+// control dispatch for each one.
+type Bridge struct {
+	server           *daemon.Server
+	auth             Authenticator
+	attest           Attestation
+	minVersion       int
+	handshakeTimeout time.Duration
+	authFailDelay    time.Duration
+	bundleDir        string
+	maxBundleBytes   int64
+	log              func(string)
+	sem              chan struct{}
+
+	mu       sync.Mutex
+	listener net.Listener
+}
+
+// BridgeOptions configures a Bridge.
+type BridgeOptions struct {
+	// Server is the local daemon to drive (required).
+	Server *daemon.Server
+	// Authenticator verifies bearer tokens (required).
+	Authenticator Authenticator
+	// Attestation is an optional post-token hook; nil => no-op.
+	Attestation Attestation
+	// MinVersion is the lowest control-protocol version accepted; 0 =>
+	// daemon.ProtoVersion.
+	MinVersion int
+	// MaxConnections bounds concurrent remote connections; 0 => default.
+	MaxConnections int
+	// HandshakeTimeout bounds the auth handshake; 0 => default.
+	HandshakeTimeout time.Duration
+	// AuthFailDelay slows brute-force attempts; <0 => none, 0 => default.
+	AuthFailDelay time.Duration
+	// BundleDir is the directory under which uploaded git bundles are extracted
+	// into per-link working trees. Empty disables bundle uploads entirely (a
+	// bundle-mode connection is then refused — opt-in, fail closed).
+	BundleDir string
+	// MaxBundleBytes caps a single uploaded bundle; 0 => default.
+	MaxBundleBytes int64
+	Log            func(string)
+}
+
+// NewBridge validates options and builds a Bridge.
+func NewBridge(opts BridgeOptions) (*Bridge, error) {
+	if opts.Server == nil {
+		return nil, errors.New("remote: bridge requires a daemon server")
+	}
+	if opts.Authenticator == nil {
+		return nil, errors.New("remote: bridge requires an authenticator")
+	}
+	minVersion := opts.MinVersion
+	if minVersion <= 0 {
+		minVersion = daemon.ProtoVersion
+	}
+	maxConns := opts.MaxConnections
+	if maxConns <= 0 {
+		maxConns = defaultMaxConnections
+	}
+	handshakeTimeout := opts.HandshakeTimeout
+	if handshakeTimeout <= 0 {
+		handshakeTimeout = defaultHandshakeTimeout
+	}
+	authFailDelay := opts.AuthFailDelay
+	switch {
+	case authFailDelay < 0:
+		authFailDelay = 0
+	case authFailDelay == 0:
+		authFailDelay = defaultAuthFailDelay
+	}
+	attest := opts.Attestation
+	if attest == nil {
+		attest = noopAttestation{}
+	}
+	maxBundleBytes := opts.MaxBundleBytes
+	if maxBundleBytes <= 0 {
+		maxBundleBytes = defaultMaxBundleBytes
+	}
+	return &Bridge{
+		server:           opts.Server,
+		auth:             opts.Authenticator,
+		attest:           attest,
+		minVersion:       minVersion,
+		handshakeTimeout: handshakeTimeout,
+		authFailDelay:    authFailDelay,
+		bundleDir:        strings.TrimSpace(opts.BundleDir),
+		maxBundleBytes:   maxBundleBytes,
+		log:              opts.Log,
+		sem:              make(chan struct{}, maxConns),
+	}, nil
+}
+
+func (b *Bridge) logf(format string, args ...any) {
+	if b.log != nil {
+		b.log(fmt.Sprintf(format, args...))
+	}
+}
+
+// ListenAndServeTLS binds a TLS listener on addr and serves until the listener
+// is closed (via Close). It refuses to serve without a TLS config (no plaintext
+// remote bridge).
+func (b *Bridge) ListenAndServeTLS(addr string, tlsConfig *tls.Config) error {
+	if tlsConfig == nil {
+		return errors.New("remote: TLS config is required; refusing to serve a plaintext remote bridge")
+	}
+	listener, err := tls.Listen("tcp", addr, tlsConfig)
+	if err != nil {
+		return fmt.Errorf("remote: listen %s: %w", addr, err)
+	}
+	b.mu.Lock()
+	b.listener = listener
+	b.mu.Unlock()
+	return b.Serve(listener)
+}
+
+// Close stops the listener started by ListenAndServeTLS, causing Serve to
+// return. Safe to call before serving or more than once.
+func (b *Bridge) Close() error {
+	b.mu.Lock()
+	listener := b.listener
+	b.listener = nil // clear so a repeat Close is a no-op, not a closed-listener error
+	b.mu.Unlock()
+	if listener != nil {
+		return listener.Close()
+	}
+	return nil
+}
+
+// Serve accepts connections from listener until it returns an error (e.g. it is
+// closed). Each connection is authenticated, then handed to the daemon's control
+// dispatch. Connections beyond MaxConnections are refused immediately.
+func (b *Bridge) Serve(listener net.Listener) error {
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			return err
+		}
+		select {
+		case b.sem <- struct{}{}:
+		default:
+			// At capacity: refuse fast (fail closed) rather than queueing.
+			b.logf("remote: refused connection (at capacity)")
+			_ = conn.Close()
+			continue
+		}
+		go func() {
+			defer func() { <-b.sem }()
+			b.handle(conn)
+		}()
+	}
+}
+
+// handle authenticates conn then drives the daemon dispatch. It always closes
+// conn (directly on a failed handshake, or via ServeConn on success).
+func (b *Bridge) handle(conn net.Conn) {
+	// Bound the auth handshake so a stalled peer cannot hold a connection slot.
+	_ = conn.SetDeadline(time.Now().Add(b.handshakeTimeout))
+	req, err := readAuthRequest(conn)
+	if err != nil {
+		_ = conn.Close()
+		return
+	}
+	if req.Version < b.minVersion {
+		b.deny(conn, "unsupported protocol version")
+		return
+	}
+	if err := b.auth.Authenticate(req.Token); err != nil {
+		b.deny(conn, "unauthorized")
+		return
+	}
+	if err := b.attest.Verify(req.Meta); err != nil {
+		b.deny(conn, "attestation failed")
+		return
+	}
+	// Resolve the connection mode before accepting it. Validating here (before the
+	// success response) lets the bridge fail closed: an unknown mode, or a bundle
+	// upload when bundle transfer is disabled, is denied without side effects.
+	mode := req.Mode
+	if mode == "" {
+		mode = ModeSession
+	}
+	switch mode {
+	case ModeSession:
+	case ModeBundle:
+		if b.bundleDir == "" {
+			b.deny(conn, "bundle transfer not enabled")
+			return
+		}
+	default:
+		b.deny(conn, "unsupported mode")
+		return
+	}
+	if err := writeAuthResponse(conn, authResponse{OK: true, Version: daemon.ProtoVersion}); err != nil {
+		_ = conn.Close()
+		return
+	}
+	// Clear the handshake deadline: a session may stream, and a bundle upload may
+	// transfer many megabytes, for a long time.
+	_ = conn.SetDeadline(time.Time{})
+	switch mode {
+	case ModeBundle:
+		b.handleBundle(conn) // receives + extracts the bundle, then closes conn
+	default:
+		b.server.ServeConn(conn) // performs the daemon handshake + one command, then closes conn
+	}
+}
+
+// deny rejects an unauthenticated connection after a small backoff (to slow
+// brute force). The reason is generic and never includes any token material.
+func (b *Bridge) deny(conn net.Conn, message string) {
+	if b.authFailDelay > 0 {
+		time.Sleep(b.authFailDelay)
+	}
+	_ = writeAuthResponse(conn, authResponse{OK: false, Message: message})
+	_ = conn.Close()
+}
+
+// ServerTLSConfig builds a server TLS config from a cert/key pair, refusing if
+// either is missing (TLS is mandatory for the remote bridge).
+func ServerTLSConfig(certFile, keyFile string) (*tls.Config, error) {
+	certFile = strings.TrimSpace(certFile)
+	keyFile = strings.TrimSpace(keyFile)
+	if certFile == "" || keyFile == "" {
+		return nil, errors.New("remote: a TLS cert and key are required for serve-remote")
+	}
+	cert, err := tls.LoadX509KeyPair(certFile, keyFile)
+	if err != nil {
+		return nil, fmt.Errorf("remote: load TLS keypair: %w", err)
+	}
+	return &tls.Config{Certificates: []tls.Certificate{cert}, MinVersion: tls.VersionTLS12}, nil
+}

internal/daemon/remote/bridge_test.go

@@ -0,0 +1,342 @@
+package remote
+
+import (
+	"context"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"errors"
+	"math/big"
+	"net"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/daemon"
+)
+
+// ---- fake daemon worker (the daemon's test fakes are unexported) -------------
+
+type fakeLines struct{ ch <-chan string }
+
+func (l fakeLines) Next() (string, bool, error) {
+	line, ok := <-l.ch
+	return line, ok, nil
+}
+
+type fakeWorker struct {
+	ch  chan string
+	pid int
+}
+
+func (w *fakeWorker) Stdout() daemon.Lines { return fakeLines{ch: w.ch} }
+func (w *fakeWorker) Wait() (int, error)   { return 0, nil }
+func (w *fakeWorker) Kill() error          { return nil }
+func (w *fakeWorker) Pid() int             { return w.pid }
+
+// staticLauncher emits the given lines then ends the stream.
+func staticLauncher(lines ...string) daemon.Launcher {
+	return func(_ context.Context, _ daemon.WorkerSpec) (daemon.WorkerHandle, error) {
+		ch := make(chan string, len(lines))
+		for _, l := range lines {
+			ch <- l
+		}
+		close(ch)
+		return &fakeWorker{ch: ch, pid: 1}, nil
+	}
+}
+
+// blockingLauncher returns a worker whose stream stays open until release is
+// closed, so a session (and its bridge connection slot) is held open.
+func blockingLauncher(release <-chan struct{}) daemon.Launcher {
+	return func(_ context.Context, _ daemon.WorkerSpec) (daemon.WorkerHandle, error) {
+		ch := make(chan string)
+		go func() {
+			<-release
+			close(ch)
+		}()
+		return &fakeWorker{ch: ch, pid: 1}, nil
+	}
+}
+
+func newBridgeServer(t *testing.T, launcher daemon.Launcher) *daemon.Server {
+	t.Helper()
+	dir := t.TempDir()
+	pool, err := daemon.NewPool(daemon.PoolOptions{Size: 4, Launcher: launcher, KillTimeout: 200 * time.Millisecond})
+	if err != nil {
+		t.Fatalf("NewPool: %v", err)
+	}
+	mgr, err := daemon.NewSessionManager(daemon.SessionManagerOptions{Pool: pool})
+	if err != nil {
+		t.Fatalf("NewSessionManager: %v", err)
+	}
+	srv, err := daemon.NewServer(daemon.ServerOptions{
+		Paths:   daemon.Paths{Socket: filepath.Join(dir, "s.sock"), Lock: filepath.Join(dir, "s.lock"), Status: filepath.Join(dir, "s.status")},
+		Manager: mgr,
+		Pool:    pool,
+	})
+	if err != nil {
+		t.Fatalf("NewServer: %v", err)
+	}
+	t.Cleanup(srv.Shutdown)
+	return srv
+}
+
+// genTestCert writes a self-signed cert/key (valid for 127.0.0.1) to temp files.
+func genTestCert(t *testing.T) (certFile, keyFile string) {
+	t.Helper()
+	key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatalf("genkey: %v", err)
+	}
+	tmpl := &x509.Certificate{
+		SerialNumber: big.NewInt(1),
+		Subject:      pkix.Name{CommonName: "zero-remote-test"},
+		NotBefore:    time.Now().Add(-time.Hour),
+		NotAfter:     time.Now().Add(time.Hour),
+		KeyUsage:     x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
+		ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		IsCA:         true,
+		IPAddresses:  []net.IP{net.ParseIP("127.0.0.1"), net.ParseIP("::1")},
+		DNSNames:     []string{"localhost"},
+	}
+	der, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, &key.PublicKey, key)
+	if err != nil {
+		t.Fatalf("create cert: %v", err)
+	}
+	dir := t.TempDir()
+	certFile = filepath.Join(dir, "cert.pem")
+	keyFile = filepath.Join(dir, "key.pem")
+	certOut, _ := os.Create(certFile)
+	_ = pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: der})
+	_ = certOut.Close()
+	keyDER, _ := x509.MarshalECPrivateKey(key)
+	keyOut, _ := os.Create(keyFile)
+	_ = pem.Encode(keyOut, &pem.Block{Type: "EC PRIVATE KEY", Bytes: keyDER})
+	_ = keyOut.Close()
+	return certFile, keyFile
+}
+
+// startBridge starts a TLS bridge on 127.0.0.1:0 and returns its address + cert.
+func startBridge(t *testing.T, srv *daemon.Server, opts BridgeOptions) (addr, caCert string) {
+	t.Helper()
+	certFile, keyFile := genTestCert(t)
+	tlsConfig, err := ServerTLSConfig(certFile, keyFile)
+	if err != nil {
+		t.Fatalf("ServerTLSConfig: %v", err)
+	}
+	opts.Server = srv
+	bridge, err := NewBridge(opts)
+	if err != nil {
+		t.Fatalf("NewBridge: %v", err)
+	}
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	tlsLn := tls.NewListener(ln, tlsConfig)
+	go func() { _ = bridge.Serve(tlsLn) }()
+	t.Cleanup(func() { _ = tlsLn.Close() })
+	return ln.Addr().String(), certFile
+}
+
+func TestBridgeRunStatusRoundTrip(t *testing.T) {
+	srv := newBridgeServer(t, staticLauncher(`{"type":"event","seq":1}`, `{"type":"event","seq":2}`))
+	auth, _ := NewTokenAuthenticator("tok")
+	addr, ca := startBridge(t, srv, BridgeOptions{Authenticator: auth})
+
+	client, err := DialRemote(RemoteConfig{Address: addr, Token: "tok", CACertFile: ca})
+	if err != nil {
+		t.Fatalf("DialRemote: %v", err)
+	}
+	var got []string
+	if err := client.Run("sess-1", "", "hello", nil, func(l string) { got = append(got, l) }); err != nil {
+		t.Fatalf("Run: %v", err)
+	}
+	_ = client.Close()
+	if len(got) != 2 || got[0] != `{"type":"event","seq":1}` {
+		t.Fatalf("run output = %v", got)
+	}
+
+	// Status over a fresh remote connection (same protocol as local).
+	statusClient, err := DialRemote(RemoteConfig{Address: addr, Token: "tok", CACertFile: ca})
+	if err != nil {
+		t.Fatalf("DialRemote(status): %v", err)
+	}
+	report, err := statusClient.Status()
+	if err != nil {
+		t.Fatalf("Status: %v", err)
+	}
+	_ = statusClient.Close()
+	if report == nil || report.PID == 0 {
+		t.Fatalf("status report = %+v", report)
+	}
+}
+
+func TestBridgeRejectsBadToken(t *testing.T) {
+	srv := newBridgeServer(t, staticLauncher())
+	auth, _ := NewTokenAuthenticator("correct")
+	addr, ca := startBridge(t, srv, BridgeOptions{Authenticator: auth, AuthFailDelay: -1})
+
+	_, err := DialRemote(RemoteConfig{Address: addr, Token: "wrong", CACertFile: ca})
+	if !errors.Is(err, ErrUnauthorized) {
+		t.Fatalf("DialRemote(bad token) err = %v, want ErrUnauthorized", err)
+	}
+}
+
+func TestBridgeRejectsLowVersion(t *testing.T) {
+	srv := newBridgeServer(t, staticLauncher())
+	auth, _ := NewTokenAuthenticator("tok")
+	// Require a version higher than the client speaks (daemon.ProtoVersion).
+	addr, ca := startBridge(t, srv, BridgeOptions{Authenticator: auth, MinVersion: daemon.ProtoVersion + 1, AuthFailDelay: -1})
+
+	_, err := DialRemote(RemoteConfig{Address: addr, Token: "tok", CACertFile: ca})
+	if err == nil {
+		t.Fatal("DialRemote with a below-min version must be rejected")
+	}
+}
+
+func TestBridgeRequiresVerifiableCert(t *testing.T) {
+	srv := newBridgeServer(t, staticLauncher())
+	auth, _ := NewTokenAuthenticator("tok")
+	addr, _ := startBridge(t, srv, BridgeOptions{Authenticator: auth})
+	// No CA configured + a self-signed server cert => verification must fail
+	// (NEVER InsecureSkipVerify).
+	if _, err := DialRemote(RemoteConfig{Address: addr, Token: "tok"}); err == nil {
+		t.Fatal("DialRemote must reject an untrusted self-signed cert")
+	}
+}
+
+func TestListenAndServeTLSRequiresConfig(t *testing.T) {
+	srv := newBridgeServer(t, staticLauncher())
+	auth, _ := NewTokenAuthenticator("tok")
+	bridge, _ := NewBridge(BridgeOptions{Server: srv, Authenticator: auth})
+	if err := bridge.ListenAndServeTLS("127.0.0.1:0", nil); err == nil {
+		t.Fatal("ListenAndServeTLS(nil) must refuse to serve plaintext")
+	}
+}
+
+func TestListenAndServeTLSServesAndCloses(t *testing.T) {
+	srv := newBridgeServer(t, staticLauncher(`{"type":"event","seq":1}`))
+	auth, _ := NewTokenAuthenticator("tok")
+	certFile, keyFile := genTestCert(t)
+	tlsConfig, err := ServerTLSConfig(certFile, keyFile)
+	if err != nil {
+		t.Fatalf("ServerTLSConfig: %v", err)
+	}
+	bridge, err := NewBridge(BridgeOptions{Server: srv, Authenticator: auth})
+	if err != nil {
+		t.Fatalf("NewBridge: %v", err)
+	}
+	// Bind an ephemeral port, discover it, then serve via ListenAndServeTLS by
+	// passing the same addr (it rebinds) — instead we bind here to learn the port
+	// and serve through the public entry on that exact address.
+	probe, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("probe listen: %v", err)
+	}
+	addr := probe.Addr().String()
+	_ = probe.Close()
+
+	serveErr := make(chan error, 1)
+	go func() { serveErr <- bridge.ListenAndServeTLS(addr, tlsConfig) }()
+
+	// Wait until it accepts a connection, then drive one run.
+	var client *daemon.Client
+	deadline := time.Now().Add(2 * time.Second)
+	for {
+		client, err = DialRemote(RemoteConfig{Address: addr, Token: "tok", CACertFile: certFile, Timeout: 300 * time.Millisecond})
+		if err == nil {
+			break
+		}
+		if time.Now().After(deadline) {
+			t.Fatalf("bridge never came up: %v", err)
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+	var got []string
+	if err := client.Run("s", "", "hi", nil, func(l string) { got = append(got, l) }); err != nil {
+		t.Fatalf("Run: %v", err)
+	}
+	_ = client.Close()
+	if len(got) != 1 {
+		t.Fatalf("got %d lines, want 1", len(got))
+	}
+	// Close stops the accept loop; a second Close is a no-op (not an error).
+	if err := bridge.Close(); err != nil {
+		t.Fatalf("Close: %v", err)
+	}
+	if err := bridge.Close(); err != nil {
+		t.Fatalf("second Close should be a no-op, got: %v", err)
+	}
+	select {
+	case <-serveErr: // ListenAndServeTLS returned after Close
+	case <-time.After(2 * time.Second):
+		t.Fatal("ListenAndServeTLS did not return after Close")
+	}
+}
+
+func TestBridgeResumeAfterReconnect(t *testing.T) {
+	srv := newBridgeServer(t, staticLauncher(`{"type":"event","seq":1}`, `{"type":"event","seq":2}`))
+	auth, _ := NewTokenAuthenticator("tok")
+	addr, ca := startBridge(t, srv, BridgeOptions{Authenticator: auth})
+
+	// First connection runs the session to completion.
+	c1, err := DialRemote(RemoteConfig{Address: addr, Token: "tok", CACertFile: ca})
+	if err != nil {
+		t.Fatalf("DialRemote 1: %v", err)
+	}
+	if err := c1.Run("sess-resume", "", "hi", nil, func(string) {}); err != nil {
+		t.Fatalf("Run: %v", err)
+	}
+	_ = c1.Close()
+
+	// A new connection re-attaches and replays the buffered session output —
+	// the dropped first connection did not lose the session.
+	c2, err := DialRemote(RemoteConfig{Address: addr, Token: "tok", CACertFile: ca})
+	if err != nil {
+		t.Fatalf("DialRemote 2: %v", err)
+	}
+	defer c2.Close()
+	var replayed []string
+	if err := c2.Attach("sess-resume", func(l string) { replayed = append(replayed, l) }); err != nil {
+		t.Fatalf("Attach: %v", err)
+	}
+	if len(replayed) != 2 {
+		t.Fatalf("re-attach replayed %d lines, want 2", len(replayed))
+	}
+}
+
+func TestBridgeConnectionCap(t *testing.T) {
+	release := make(chan struct{})
+	defer close(release)
+	srv := newBridgeServer(t, blockingLauncher(release))
+	auth, _ := NewTokenAuthenticator("tok")
+	addr, ca := startBridge(t, srv, BridgeOptions{Authenticator: auth, MaxConnections: 1})
+
+	// First connection holds the only slot with a blocking run.
+	c1, err := DialRemote(RemoteConfig{Address: addr, Token: "tok", CACertFile: ca})
+	if err != nil {
+		t.Fatalf("DialRemote 1: %v", err)
+	}
+	defer c1.Close()
+	runErr := make(chan error, 1)
+	go func() { runErr <- c1.Run("sess-block", "", "hi", nil, func(string) {}) }()
+
+	// Wait until the slot is in use, then a second dial must be refused.
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		c2, err := DialRemote(RemoteConfig{Address: addr, Token: "tok", CACertFile: ca, Timeout: 500 * time.Millisecond})
+		if err != nil {
+			return // refused as expected
+		}
+		_ = c2.Close()
+		time.Sleep(20 * time.Millisecond)
+	}
+	t.Fatal("second connection was not refused at the connection cap")
+}

internal/daemon/remote/bundle.go

@@ -0,0 +1,378 @@
+package remote
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/daemon"
+)
+
+// gitTimeout bounds a single git invocation (bundle create/verify, clone) so a
+// hung git process cannot pin a connection or the upload path indefinitely.
+const gitTimeout = 2 * time.Minute
+
+// bundleChunkSize is the per-frame payload when streaming a bundle file. It is
+// kept comfortably under daemon.MaxFrameSize (1 MiB).
+const bundleChunkSize = 512 << 10
+
+// bundleHeader is the first control frame of a bundle upload (after the auth
+// handshake): it declares the link id and the exact byte size that follows.
+type bundleHeader struct {
+	LinkID string `json:"link_id"`
+	Size   int64  `json:"size"`
+}
+
+// bundleResult is the bridge's reply once the bundle is received and extracted.
+type bundleResult struct {
+	OK      bool   `json:"ok"`
+	Path    string `json:"path,omitempty"`
+	Message string `json:"message,omitempty"`
+}
+
+func writeBundleHeader(w io.Writer, h bundleHeader) error {
+	payload, err := json.Marshal(h)
+	if err != nil {
+		return err
+	}
+	return daemon.WriteFrame(w, daemon.KindCtrl, payload)
+}
+
+func readBundleHeader(r io.Reader) (bundleHeader, error) {
+	kind, payload, err := daemon.ReadFrame(r)
+	if err != nil {
+		return bundleHeader{}, err
+	}
+	if kind != daemon.KindCtrl {
+		return bundleHeader{}, errors.New("remote: expected bundle header frame")
+	}
+	var h bundleHeader
+	if err := json.Unmarshal(payload, &h); err != nil {
+		return bundleHeader{}, fmt.Errorf("remote: decode bundle header: %w", err)
+	}
+	return h, nil
+}
+
+func writeBundleResult(w io.Writer, res bundleResult) error {
+	payload, err := json.Marshal(res)
+	if err != nil {
+		return err
+	}
+	return daemon.WriteFrame(w, daemon.KindCtrl, payload)
+}
+
+func readBundleResult(r io.Reader) (bundleResult, error) {
+	kind, payload, err := daemon.ReadFrame(r)
+	if err != nil {
+		return bundleResult{}, err
+	}
+	if kind != daemon.KindCtrl {
+		return bundleResult{}, errors.New("remote: expected bundle result frame")
+	}
+	var res bundleResult
+	if err := json.Unmarshal(payload, &res); err != nil {
+		return bundleResult{}, fmt.Errorf("remote: decode bundle result: %w", err)
+	}
+	return res, nil
+}
+
+// ---- server side -----------------------------------------------------------
+
+// handleBundle receives an uploaded bundle, extracts it into a per-link working
+// tree, and reports the outcome. It always closes conn.
+func (b *Bridge) handleBundle(conn net.Conn) {
+	defer func() { _ = conn.Close() }()
+	res := b.receiveBundle(conn)
+	if !res.OK {
+		b.logf("remote: bundle upload rejected: %s", res.Message)
+	}
+	_ = writeBundleResult(conn, res)
+}
+
+// receiveBundle reads the header + framed bundle bytes, verifies the bundle, and
+// extracts it under bundleDir. Every failure returns a non-OK result rather than
+// panicking, and the staged temp file is always removed.
+func (b *Bridge) receiveBundle(conn net.Conn) bundleResult {
+	hdr, err := readBundleHeader(conn)
+	if err != nil {
+		return bundleResult{Message: "read bundle header: " + err.Error()}
+	}
+	id, err := sanitizeLinkID(hdr.LinkID)
+	if err != nil {
+		return bundleResult{Message: err.Error()}
+	}
+	if hdr.Size <= 0 || hdr.Size > b.maxBundleBytes {
+		return bundleResult{Message: fmt.Sprintf("invalid bundle size %d (max %d)", hdr.Size, b.maxBundleBytes)}
+	}
+
+	tmp, err := os.CreateTemp("", "zero-remote-*.bundle")
+	if err != nil {
+		return bundleResult{Message: "stage bundle: " + err.Error()}
+	}
+	tmpName := tmp.Name()
+	defer func() { _ = os.Remove(tmpName) }()
+	if err := streamFramesToFile(conn, tmp, hdr.Size); err != nil {
+		_ = tmp.Close()
+		return bundleResult{Message: "receive bundle: " + err.Error()}
+	}
+	if err := tmp.Close(); err != nil {
+		return bundleResult{Message: "stage bundle: " + err.Error()}
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), gitTimeout)
+	defer cancel()
+	if err := gitBundleVerify(ctx, tmpName); err != nil {
+		return bundleResult{Message: "bundle verify: " + err.Error()}
+	}
+	dest := filepath.Join(b.bundleDir, id)
+	if !withinDir(b.bundleDir, dest) {
+		return bundleResult{Message: "invalid link id"}
+	}
+	if err := extractBundle(ctx, tmpName, dest); err != nil {
+		return bundleResult{Message: "extract bundle: " + err.Error()}
+	}
+	return bundleResult{OK: true, Path: dest}
+}
+
+// streamFramesToFile copies exactly size bytes from KindData frames on r into w.
+// A non-data frame, or any frame that would overrun the declared size, is an
+// error (fail closed) so a peer cannot write past the cap.
+func streamFramesToFile(r io.Reader, w io.Writer, size int64) error {
+	remaining := size
+	for remaining > 0 {
+		kind, payload, err := daemon.ReadFrame(r)
+		if err != nil {
+			return err
+		}
+		if kind != daemon.KindData {
+			return errors.New("expected bundle data frame")
+		}
+		if int64(len(payload)) > remaining {
+			return errors.New("bundle exceeds declared size")
+		}
+		if _, err := w.Write(payload); err != nil {
+			return err
+		}
+		remaining -= int64(len(payload))
+	}
+	return nil
+}
+
+// extractBundle clones bundleFile into a staging dir, then atomically renames it
+// over dest (replacing any prior extraction for this link id). git clone needs a
+// non-existent target, so the staging+rename keeps the live dest intact on error.
+func extractBundle(ctx context.Context, bundleFile, dest string) error {
+	parent := filepath.Dir(dest)
+	if err := os.MkdirAll(parent, 0o700); err != nil {
+		return err
+	}
+	staging, err := os.MkdirTemp(parent, ".staging-*")
+	if err != nil {
+		return err
+	}
+	defer func() { _ = os.RemoveAll(staging) }()
+	cloneDest := filepath.Join(staging, "repo")
+	if err := gitClone(ctx, bundleFile, cloneDest); err != nil {
+		return err
+	}
+	if err := os.RemoveAll(dest); err != nil {
+		return err
+	}
+	return os.Rename(cloneDest, dest)
+}
+
+// ---- client side -----------------------------------------------------------
+
+// UploadRepoBundle creates a git bundle of repoDir's full history and uploads it
+// to the remote bridge over an authenticated, bundle-mode TLS connection. The
+// bridge extracts it into a per-link working tree and returns its path, captured
+// in the returned SessionLink. repoDir must be a git work tree.
+func UploadRepoBundle(cfg RemoteConfig, repoDir, linkID string) (*SessionLink, error) {
+	id, err := sanitizeLinkID(linkID)
+	if err != nil {
+		return nil, err
+	}
+	repoDir = strings.TrimSpace(repoDir)
+	if repoDir == "" {
+		return nil, errors.New("remote: repo dir is required")
+	}
+	if !isGitWorktree(repoDir) {
+		return nil, fmt.Errorf("remote: %s is not a git repository", repoDir)
+	}
+
+	// Reserve a unique temp name, then let git create the bundle fresh at it.
+	tmp, err := os.CreateTemp("", "zero-bundle-*.bundle")
+	if err != nil {
+		return nil, fmt.Errorf("remote: stage bundle: %w", err)
+	}
+	tmpName := tmp.Name()
+	_ = tmp.Close()
+	_ = os.Remove(tmpName)
+	defer func() { _ = os.Remove(tmpName) }()
+
+	ctx, cancel := context.WithTimeout(context.Background(), gitTimeout)
+	defer cancel()
+	if err := gitBundleCreate(ctx, repoDir, tmpName); err != nil {
+		return nil, fmt.Errorf("remote: create bundle: %w", err)
+	}
+	sum, size, err := hashFile(tmpName)
+	if err != nil {
+		return nil, fmt.Errorf("remote: hash bundle: %w", err)
+	}
+
+	conn, err := dialAuthenticated(cfg, ModeBundle)
+	if err != nil {
+		return nil, err
+	}
+	defer func() { _ = conn.Close() }()
+
+	if err := writeBundleHeader(conn, bundleHeader{LinkID: id, Size: size}); err != nil {
+		return nil, fmt.Errorf("remote: send bundle header: %w", err)
+	}
+	if err := streamFileFrames(conn, tmpName); err != nil {
+		return nil, fmt.Errorf("remote: send bundle: %w", err)
+	}
+	res, err := readBundleResult(conn)
+	if err != nil {
+		return nil, fmt.Errorf("remote: bundle result: %w", err)
+	}
+	if !res.OK {
+		return nil, fmt.Errorf("remote: bundle rejected: %s", res.Message)
+	}
+
+	return &SessionLink{
+		Address:      strings.TrimSpace(cfg.Address),
+		ServerName:   strings.TrimSpace(cfg.ServerName),
+		CACertFile:   strings.TrimSpace(cfg.CACertFile),
+		LinkID:       id,
+		RemotePath:   res.Path,
+		BundleSHA256: sum,
+	}, nil
+}
+
+// streamFileFrames writes the file at path to w as a sequence of KindData frames.
+func streamFileFrames(w io.Writer, path string) error {
+	f, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = f.Close() }()
+	buf := make([]byte, bundleChunkSize)
+	for {
+		n, err := f.Read(buf)
+		if n > 0 {
+			if werr := daemon.WriteFrame(w, daemon.KindData, buf[:n]); werr != nil {
+				return werr
+			}
+		}
+		if err == io.EOF {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+	}
+}
+
+// ---- git + path helpers ----------------------------------------------------
+
+func gitBundleCreate(ctx context.Context, repoDir, outFile string) error {
+	return runGit(ctx, repoDir, "bundle", "create", outFile, "--all")
+}
+
+func gitBundleVerify(ctx context.Context, bundleFile string) error {
+	return runGit(ctx, "", "bundle", "verify", bundleFile)
+}
+
+func gitClone(ctx context.Context, bundleFile, destDir string) error {
+	return runGit(ctx, "", "clone", "--quiet", bundleFile, destDir)
+}
+
+// isGitWorktree reports whether dir is inside a git work tree.
+func isGitWorktree(dir string) bool {
+	cmd := exec.Command("git", "-C", dir, "rev-parse", "--is-inside-work-tree")
+	out, err := cmd.CombinedOutput()
+	return err == nil && strings.TrimSpace(string(out)) == "true"
+}
+
+// runGit runs a git subcommand, returning a concise single-line error on failure.
+func runGit(ctx context.Context, dir string, args ...string) error {
+	cmd := exec.CommandContext(ctx, "git", args...)
+	if dir != "" {
+		cmd.Dir = dir
+	}
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		msg := firstLine(strings.TrimSpace(string(out)))
+		if msg == "" {
+			msg = err.Error()
+		}
+		return fmt.Errorf("git %s: %s", args[0], msg)
+	}
+	return nil
+}
+
+// sanitizeLinkID validates a link id used as a single path component under the
+// bundle dir. It allows letters, digits, '-', '_', '.', forbids the traversal
+// names, and caps the length — so it can never escape the bundle dir.
+func sanitizeLinkID(id string) (string, error) {
+	id = strings.TrimSpace(id)
+	if id == "" {
+		return "", errors.New("remote: link id is required")
+	}
+	if len(id) > 128 {
+		return "", errors.New("remote: link id too long (max 128)")
+	}
+	if id == "." || id == ".." {
+		return "", errors.New("remote: invalid link id")
+	}
+	for _, r := range id {
+		switch {
+		case r >= 'a' && r <= 'z', r >= 'A' && r <= 'Z', r >= '0' && r <= '9', r == '-', r == '_', r == '.':
+		default:
+			return "", errors.New("remote: link id may only contain letters, digits, '-', '_', '.'")
+		}
+	}
+	return id, nil
+}
+
+// withinDir reports whether target resolves to a path inside root.
+func withinDir(root, target string) bool {
+	rel, err := filepath.Rel(root, target)
+	if err != nil {
+		return false
+	}
+	return rel != ".." && !strings.HasPrefix(rel, ".."+string(os.PathSeparator))
+}
+
+// hashFile returns the hex SHA-256 and byte size of the file at path.
+func hashFile(path string) (sum string, size int64, err error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return "", 0, err
+	}
+	defer func() { _ = f.Close() }()
+	h := sha256.New()
+	n, err := io.Copy(h, f)
+	if err != nil {
+		return "", 0, err
+	}
+	return hex.EncodeToString(h.Sum(nil)), n, nil
+}
+
+func firstLine(s string) string {
+	if i := strings.IndexByte(s, '\n'); i >= 0 {
+		return s[:i]
+	}
+	return s
+}

internal/daemon/remote/bundle_test.go

@@ -0,0 +1,193 @@
+package remote
+
+import (
+	"context"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"testing"
+)
+
+// initTestRepo creates a temp git work tree with one committed file and returns
+// its path. It sets a deterministic identity so it does not depend on global git
+// config.
+func initTestRepo(t *testing.T, file, content string) string {
+	t.Helper()
+	dir := t.TempDir()
+	run := func(args ...string) {
+		cmd := exec.Command("git", args...)
+		cmd.Dir = dir
+		cmd.Env = append(os.Environ(),
+			"GIT_AUTHOR_NAME=t", "[email protected]",
+			"GIT_COMMITTER_NAME=t", "[email protected]")
+		if out, err := cmd.CombinedOutput(); err != nil {
+			t.Fatalf("git %v: %v\n%s", args, err, out)
+		}
+	}
+	run("init", "-q")
+	run("config", "user.email", "[email protected]")
+	run("config", "user.name", "t")
+	if err := os.WriteFile(filepath.Join(dir, file), []byte(content), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	run("add", ".")
+	run("commit", "-q", "-m", "init")
+	return dir
+}
+
+func TestGitBundleRoundTrip(t *testing.T) {
+	repo := initTestRepo(t, "a.txt", "content")
+	ctx := context.Background()
+	bundle := filepath.Join(t.TempDir(), "x.bundle")
+	if err := gitBundleCreate(ctx, repo, bundle); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	if err := gitBundleVerify(ctx, bundle); err != nil {
+		t.Fatalf("verify: %v", err)
+	}
+	dest := filepath.Join(t.TempDir(), "clone")
+	if err := gitClone(ctx, bundle, dest); err != nil {
+		t.Fatalf("clone: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(dest, "a.txt")); err != nil {
+		t.Fatalf("cloned tree missing file: %v", err)
+	}
+}
+
+func TestIsGitWorktree(t *testing.T) {
+	repo := initTestRepo(t, "f", "x")
+	if !isGitWorktree(repo) {
+		t.Fatal("a git repo should be detected")
+	}
+	if isGitWorktree(t.TempDir()) {
+		t.Fatal("a plain dir should not be detected as a git repo")
+	}
+}
+
+func TestSanitizeLinkID(t *testing.T) {
+	for _, ok := range []string{"proj", "proj-1", "a_b.c", "ABC123"} {
+		if _, err := sanitizeLinkID(ok); err != nil {
+			t.Fatalf("sanitizeLinkID(%q) unexpected error: %v", ok, err)
+		}
+	}
+	for _, bad := range []string{"", "   ", ".", "..", "a/b", "a\\b", "a b", "a$b", string(make([]byte, 200))} {
+		if _, err := sanitizeLinkID(bad); err == nil {
+			t.Fatalf("sanitizeLinkID(%q) should error", bad)
+		}
+	}
+}
+
+func TestWithinDir(t *testing.T) {
+	root := t.TempDir()
+	if !withinDir(root, filepath.Join(root, "child")) {
+		t.Fatal("child should be within root")
+	}
+	if withinDir(root, filepath.Dir(root)) {
+		t.Fatal("parent should not be within root")
+	}
+}
+
+func TestSessionLinkSaveLoad(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "link.json")
+	link := SessionLink{Address: "host:9000", ServerName: "host", LinkID: "proj-1", RemotePath: "/bundles/proj-1", BundleSHA256: "deadbeef"}
+	if err := link.Save(path); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	if runtime.GOOS != "windows" {
+		info, err := os.Stat(path)
+		if err != nil {
+			t.Fatalf("stat: %v", err)
+		}
+		if perm := info.Mode().Perm(); perm != 0o600 {
+			t.Fatalf("link file perm = %v, want 0600", perm)
+		}
+	}
+	got, err := LoadSessionLink(path)
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if *got != link {
+		t.Fatalf("roundtrip mismatch: %+v != %+v", *got, link)
+	}
+}
+
+func TestSessionLinkValidate(t *testing.T) {
+	for _, bad := range []SessionLink{
+		{LinkID: "p", RemotePath: "/r"},    // no address
+		{Address: "h:1", RemotePath: "/r"}, // no link id
+		{Address: "h:1", LinkID: "p"},      // no remote path
+	} {
+		if err := bad.Validate(); err == nil {
+			t.Fatalf("Validate(%+v) should error", bad)
+		}
+		if err := bad.Save(filepath.Join(t.TempDir(), "x.json")); err == nil {
+			t.Fatalf("Save of invalid link %+v should error", bad)
+		}
+	}
+}
+
+func TestUploadRepoBundleRejectsNonRepo(t *testing.T) {
+	// A non-git dir is rejected before any dial, so the bogus address is never used.
+	_, err := UploadRepoBundle(RemoteConfig{Address: "127.0.0.1:1", Token: "t"}, t.TempDir(), "p")
+	if err == nil {
+		t.Fatal("a non-git dir should be rejected")
+	}
+}
+
+func TestBridgeBundleUploadRoundTrip(t *testing.T) {
+	srv := newBridgeServer(t, staticLauncher())
+	auth, _ := NewTokenAuthenticator("tok")
+	bundleRoot := t.TempDir()
+	addr, ca := startBridge(t, srv, BridgeOptions{Authenticator: auth, BundleDir: bundleRoot})
+
+	repo := initTestRepo(t, "hello.txt", "hi there")
+	link, err := UploadRepoBundle(RemoteConfig{Address: addr, Token: "tok", CACertFile: ca}, repo, "proj-1")
+	if err != nil {
+		t.Fatalf("UploadRepoBundle: %v", err)
+	}
+	wantPath := filepath.Join(bundleRoot, "proj-1")
+	if link.RemotePath != wantPath {
+		t.Fatalf("remote path = %q, want %q", link.RemotePath, wantPath)
+	}
+	if link.BundleSHA256 == "" {
+		t.Fatal("link should carry a bundle sha256")
+	}
+	// The extracted work tree should contain the committed file.
+	data, err := os.ReadFile(filepath.Join(link.RemotePath, "hello.txt"))
+	if err != nil {
+		t.Fatalf("extracted tree missing file: %v", err)
+	}
+	if string(data) != "hi there" {
+		t.Fatalf("extracted file content = %q", data)
+	}
+
+	// A second upload to the same link id replaces the prior extraction.
+	if _, err := UploadRepoBundle(RemoteConfig{Address: addr, Token: "tok", CACertFile: ca}, repo, "proj-1"); err != nil {
+		t.Fatalf("re-upload: %v", err)
+	}
+}
+
+func TestBridgeBundleDisabledByDefault(t *testing.T) {
+	srv := newBridgeServer(t, staticLauncher())
+	auth, _ := NewTokenAuthenticator("tok")
+	addr, ca := startBridge(t, srv, BridgeOptions{Authenticator: auth, AuthFailDelay: -1}) // no BundleDir
+
+	repo := initTestRepo(t, "f", "x")
+	_, err := UploadRepoBundle(RemoteConfig{Address: addr, Token: "tok", CACertFile: ca}, repo, "p")
+	if err == nil {
+		t.Fatal("bundle upload must be refused when --bundle-dir is unset")
+	}
+}
+
+func TestBridgeBundleRejectsBadToken(t *testing.T) {
+	srv := newBridgeServer(t, staticLauncher())
+	auth, _ := NewTokenAuthenticator("correct")
+	addr, ca := startBridge(t, srv, BridgeOptions{Authenticator: auth, BundleDir: t.TempDir(), AuthFailDelay: -1})
+
+	repo := initTestRepo(t, "f", "x")
+	_, err := UploadRepoBundle(RemoteConfig{Address: addr, Token: "wrong", CACertFile: ca}, repo, "p")
+	if err == nil {
+		t.Fatal("bundle upload with a bad token must be refused")
+	}
+}

internal/daemon/remote/client.go

@@ -0,0 +1,125 @@
+package remote
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"errors"
+	"fmt"
+	"net"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/daemon"
+)
+
+const defaultDialTimeout = 15 * time.Second
+
+// RemoteConfig configures a remote dial.
+type RemoteConfig struct {
+	// Address is host:port of the remote bridge (required).
+	Address string
+	// Token is the bearer token (required).
+	Token string
+	// CACertFile, when set, is the only CA trusted for the server cert (use for a
+	// self-signed bridge). Empty => system roots. InsecureSkipVerify is never used.
+	CACertFile string
+	// ServerName overrides the TLS/SNI verification name; empty => host of Address.
+	ServerName string
+	// Timeout bounds the dial + auth handshake; 0 => default.
+	Timeout time.Duration
+}
+
+// DialRemote establishes a verified TLS connection to a remote bridge,
+// authenticates with the bearer token, and returns a daemon.Client ready for
+// Run/Attach/Status — the same client the local socket uses, so remote and local
+// share one protocol. The server certificate is always verified (never
+// InsecureSkipVerify).
+func DialRemote(cfg RemoteConfig) (*daemon.Client, error) {
+	conn, err := dialAuthenticated(cfg, ModeSession)
+	if err != nil {
+		return nil, err
+	}
+	client, err := daemon.NewClientConn(conn)
+	if err != nil {
+		_ = conn.Close()
+		return nil, err
+	}
+	return client, nil
+}
+
+// dialAuthenticated establishes a verified TLS connection, performs the
+// bearer-token auth handshake for the given mode, and returns the live conn with
+// its deadline cleared (ready for the subsequent daemon handshake or bundle
+// stream). The server certificate is always verified (never InsecureSkipVerify).
+func dialAuthenticated(cfg RemoteConfig, mode string) (net.Conn, error) {
+	address := strings.TrimSpace(cfg.Address)
+	if address == "" {
+		return nil, errors.New("remote: address is required")
+	}
+	token := strings.TrimSpace(cfg.Token)
+	if token == "" {
+		return nil, errors.New("remote: a non-empty token is required")
+	}
+	tlsConfig, err := clientTLSConfig(cfg)
+	if err != nil {
+		return nil, err
+	}
+	timeout := cfg.Timeout
+	if timeout <= 0 {
+		timeout = defaultDialTimeout
+	}
+	// Context-aware TLS dial (tls.DialWithDialer is deprecated and not
+	// cancellation-aware). The context bounds the dial + TLS handshake only; the
+	// returned conn is independent of it for the subsequent auth/stream I/O.
+	dialCtx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+	dialer := &tls.Dialer{NetDialer: &net.Dialer{}, Config: tlsConfig}
+	conn, err := dialer.DialContext(dialCtx, "tcp", address)
+	if err != nil {
+		return nil, fmt.Errorf("remote: dial %s: %w", address, err)
+	}
+	// Bound the auth handshake; the daemon handshake + stream run without a deadline.
+	_ = conn.SetDeadline(time.Now().Add(timeout))
+	if err := writeAuthRequest(conn, authRequest{Token: token, Version: daemon.ProtoVersion, Mode: mode}); err != nil {
+		_ = conn.Close()
+		return nil, fmt.Errorf("remote: send auth: %w", err)
+	}
+	resp, err := readAuthResponse(conn)
+	if err != nil {
+		_ = conn.Close()
+		return nil, fmt.Errorf("remote: auth handshake: %w", err)
+	}
+	if !resp.OK {
+		_ = conn.Close()
+		return nil, fmt.Errorf("%w: %s", ErrUnauthorized, resp.Message)
+	}
+	_ = conn.SetDeadline(time.Time{})
+	return conn, nil
+}
+
+// clientTLSConfig builds a verifying client TLS config. It never disables
+// verification; for a self-signed bridge, set CACertFile to the bridge's cert.
+func clientTLSConfig(cfg RemoteConfig) (*tls.Config, error) {
+	tc := &tls.Config{MinVersion: tls.VersionTLS12}
+	serverName := strings.TrimSpace(cfg.ServerName)
+	if serverName == "" {
+		if host, _, err := net.SplitHostPort(cfg.Address); err == nil {
+			serverName = host
+		}
+	}
+	tc.ServerName = serverName
+	if ca := strings.TrimSpace(cfg.CACertFile); ca != "" {
+		pem, err := os.ReadFile(ca)
+		if err != nil {
+			return nil, fmt.Errorf("remote: read CA cert: %w", err)
+		}
+		pool := x509.NewCertPool()
+		if !pool.AppendCertsFromPEM(pem) {
+			return nil, errors.New("remote: CA cert file contained no certificates")
+		}
+		tc.RootCAs = pool
+	}
+	return tc, nil
+}

internal/daemon/remote/sessionlink.go

@@ -0,0 +1,107 @@
+package remote
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// SessionLink records the association between a local repo and the remote
+// working tree a bundle upload produced. It carries everything needed to reach
+// the linked repo again — the bridge address, TLS verification details, the link
+// id, and the extracted remote path — except the bearer token, which is always
+// supplied separately (never persisted to the link file).
+type SessionLink struct {
+	// Address is host:port of the remote bridge.
+	Address string `json:"address"`
+	// ServerName overrides TLS/SNI verification; empty => host of Address.
+	ServerName string `json:"server_name,omitempty"`
+	// CACertFile is the CA trusted for the bridge cert (for a self-signed bridge).
+	CACertFile string `json:"ca_cert_file,omitempty"`
+	// LinkID is the per-link identifier (a single path component on the remote).
+	LinkID string `json:"link_id"`
+	// RemotePath is the extracted working tree on the remote; use it as --cwd for
+	// a remote run/attach against the linked repo.
+	RemotePath string `json:"remote_path"`
+	// BundleSHA256 is the hex SHA-256 of the uploaded bundle, for verification.
+	BundleSHA256 string `json:"bundle_sha256,omitempty"`
+}
+
+// Validate checks the fields required to use a link.
+func (l SessionLink) Validate() error {
+	if strings.TrimSpace(l.Address) == "" {
+		return errors.New("remote: session link address is required")
+	}
+	if strings.TrimSpace(l.LinkID) == "" {
+		return errors.New("remote: session link id is required")
+	}
+	if strings.TrimSpace(l.RemotePath) == "" {
+		return errors.New("remote: session link remote path is required")
+	}
+	return nil
+}
+
+// Save writes the link to path as pretty JSON with 0600 permissions, atomically
+// (write-temp-then-rename) so a reader never sees a partial file.
+func (l SessionLink) Save(path string) error {
+	if err := l.Validate(); err != nil {
+		return err
+	}
+	data, err := json.MarshalIndent(l, "", "  ")
+	if err != nil {
+		return err
+	}
+	return atomicWriteFile(path, append(data, '\n'), 0o600)
+}
+
+// LoadSessionLink reads and validates a link file written by Save.
+func LoadSessionLink(path string) (*SessionLink, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	var l SessionLink
+	if err := json.Unmarshal(data, &l); err != nil {
+		return nil, fmt.Errorf("remote: decode session link: %w", err)
+	}
+	if err := l.Validate(); err != nil {
+		return nil, err
+	}
+	return &l, nil
+}
+
+// atomicWriteFile writes data to path via a temp file in the same directory,
+// chmod-ed to perm, then renamed into place.
+func atomicWriteFile(path string, data []byte, perm os.FileMode) error {
+	dir := filepath.Dir(path)
+	tmp, err := os.CreateTemp(dir, ".link-*")
+	if err != nil {
+		return err
+	}
+	tmpName := tmp.Name()
+	cleanup := true
+	defer func() {
+		if cleanup {
+			_ = os.Remove(tmpName)
+		}
+	}()
+	if _, err := tmp.Write(data); err != nil {
+		_ = tmp.Close()
+		return err
+	}
+	if err := tmp.Chmod(perm); err != nil {
+		_ = tmp.Close()
+		return err
+	}
+	if err := tmp.Close(); err != nil {
+		return err
+	}
+	if err := os.Rename(tmpName, path); err != nil {
+		return err
+	}
+	cleanup = false
+	return nil
+}

internal/daemon/server.go

@@ -0,0 +1,301 @@
+package daemon
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net"
+	"os"
+	"sync"
+	"time"
+)
+
+// Server is the daemon control plane. Mirrors reference-daemon-code-agent-js/
+// supervisor.js (single-instance lock, status file, lifecycle) + the accept loop
+// that routes framed control requests to the SessionManager/Pool. It listens on
+// an owner-only local Unix socket and NEVER binds a TCP port.
+type Server struct {
+	opts      ServerOptions
+	startedAt time.Time
+
+	listener net.Listener
+	lock     *fileLock
+
+	ctx    context.Context
+	cancel context.CancelFunc
+
+	wg           sync.WaitGroup
+	shutdownOnce sync.Once
+	done         chan struct{}
+}
+
+// ServerOptions configures a Server.
+type ServerOptions struct {
+	Paths   Paths
+	Manager *SessionManager
+	Pool    *Pool
+	Version int
+	Now     func() time.Time
+	Log     func(string)
+	isAlive func(int) bool // test hook for the single-instance lock
+}
+
+// NewServer validates options and builds a Server.
+func NewServer(opts ServerOptions) (*Server, error) {
+	if opts.Manager == nil || opts.Pool == nil {
+		return nil, errors.New("daemon: server requires a Pool and SessionManager")
+	}
+	if opts.Paths.Socket == "" || opts.Paths.Lock == "" || opts.Paths.Status == "" {
+		return nil, errors.New("daemon: server requires socket, lock, and status paths")
+	}
+	if opts.Version <= 0 {
+		opts.Version = ProtoVersion
+	}
+	if opts.Now == nil {
+		opts.Now = time.Now
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	return &Server{
+		opts:   opts,
+		ctx:    ctx,
+		cancel: cancel,
+		done:   make(chan struct{}),
+	}, nil
+}
+
+func (s *Server) logf(format string, args ...any) {
+	if s.opts.Log != nil {
+		s.opts.Log(fmt.Sprintf(format, args...))
+	}
+}
+
+// Serve acquires the single-instance lock, binds the owner-only control socket,
+// writes the status file, and serves connections until Shutdown. It blocks. On
+// return it has released the lock and removed the socket/status files.
+func (s *Server) Serve() error {
+	if err := checkSocketPathLength(s.opts.Paths.Socket); err != nil {
+		return err
+	}
+	if err := secureSocketParent(s.opts.Paths.Socket); err != nil {
+		return err
+	}
+	lock, err := acquireLock(s.opts.Paths.Lock, s.opts.isAlive)
+	if err != nil {
+		return err
+	}
+	s.lock = lock
+	defer s.cleanup()
+
+	// A leftover socket file from an unclean exit would make Listen fail with
+	// "address already in use"; we hold the lock, so any socket here is stale.
+	_ = os.Remove(s.opts.Paths.Socket)
+
+	listener, err := net.Listen("unix", s.opts.Paths.Socket)
+	if err != nil {
+		return fmt.Errorf("daemon: bind control socket: %w", err)
+	}
+	s.listener = listener
+	if err := hardenSocketFile(s.opts.Paths.Socket); err != nil {
+		return fmt.Errorf("daemon: harden control socket: %w", err)
+	}
+	s.startedAt = s.opts.Now()
+	if err := s.writeStatusFile(); err != nil {
+		return err
+	}
+	s.logf("daemon listening on %s (pid %d)", s.opts.Paths.Socket, os.Getpid())
+
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			select {
+			case <-s.done:
+				s.wg.Wait()
+				return nil // clean shutdown
+			default:
+				// Transient accept error during normal operation.
+				s.logf("accept error: %v", err)
+				return fmt.Errorf("daemon: accept: %w", err)
+			}
+		}
+		s.wg.Add(1)
+		go func() {
+			defer s.wg.Done()
+			s.handleConn(conn)
+		}()
+	}
+}
+
+// Shutdown stops accepting connections, cancels in-flight runs, drains the pool,
+// and removes the socket/lock/status files. Safe to call multiple times.
+func (s *Server) Shutdown() {
+	s.shutdownOnce.Do(func() {
+		close(s.done)
+		s.cancel() // stop in-flight pool runs
+		if s.listener != nil {
+			_ = s.listener.Close()
+		}
+		s.opts.Pool.Drain()
+	})
+}
+
+func (s *Server) cleanup() {
+	if s.listener != nil {
+		_ = s.listener.Close()
+	}
+	_ = os.Remove(s.opts.Paths.Socket)
+	_ = os.Remove(s.opts.Paths.Status)
+	if s.lock != nil {
+		_ = s.lock.release()
+	}
+}
+
+func (s *Server) writeStatusFile() error {
+	status := StatusFile{
+		PID:       os.Getpid(),
+		Socket:    s.opts.Paths.Socket,
+		Version:   s.opts.Version,
+		StartedAt: s.startedAt,
+	}
+	data, err := json.MarshalIndent(status, "", "  ")
+	if err != nil {
+		return err
+	}
+	if err := os.WriteFile(s.opts.Paths.Status, data, 0o600); err != nil {
+		return fmt.Errorf("daemon: write status file: %w", err)
+	}
+	return nil
+}
+
+// ServeConn runs the control protocol (handshake + one command) on an
+// already-established connection, reusing the exact local dispatch path. The
+// remote bridge calls it AFTER authenticating a TLS connection, so a remote
+// session is handled identically to a local one (same SessionManager/Pool, same
+// sandbox/risk model) — remote never bypasses the local controls. It closes conn.
+func (s *Server) ServeConn(conn net.Conn) { s.handleConn(conn) }
+
+// handleConn performs the handshake then dispatches a single control command.
+func (s *Server) handleConn(conn net.Conn) {
+	defer conn.Close()
+
+	hello, err := ReadControl(conn)
+	if err != nil {
+		return
+	}
+	if hello.Type != CtrlHello {
+		_ = WriteControl(conn, Ctrl{Type: CtrlError, Message: "expected hello"})
+		return
+	}
+	version, ok := NegotiateVersion(hello.Version)
+	if !ok {
+		_ = WriteControl(conn, Ctrl{Type: CtrlError, Message: "unsupported protocol version"})
+		return
+	}
+	if err := WriteControl(conn, Ctrl{Type: CtrlHelloOK, Version: version}); err != nil {
+		return
+	}
+
+	cmd, err := ReadControl(conn)
+	if err != nil {
+		return
+	}
+	switch cmd.Type {
+	case CtrlRun:
+		s.handleRun(conn, cmd)
+	case CtrlAttach:
+		s.handleAttach(conn, cmd)
+	case CtrlStatus:
+		s.handleStatus(conn)
+	case CtrlShutdown:
+		_ = WriteControl(conn, Ctrl{Type: CtrlAck, Message: "shutting down"})
+		s.Shutdown()
+	default:
+		_ = WriteControl(conn, Ctrl{Type: CtrlError, Message: fmt.Sprintf("unknown command %q", cmd.Type)})
+	}
+}
+
+func (s *Server) handleRun(conn net.Conn, cmd Ctrl) {
+	if cmd.Session == "" {
+		_ = WriteControl(conn, Ctrl{Type: CtrlError, Message: "run requires a session id"})
+		return
+	}
+	args := cmd.Args
+	if cmd.Prompt != "" {
+		args = append(args, "--prompt", cmd.Prompt)
+	}
+	sess, err := s.opts.Manager.Start(s.ctx, WorkerSpec{Session: cmd.Session, Cwd: cmd.Cwd, Args: args})
+	if err != nil {
+		_ = WriteControl(conn, Ctrl{Type: CtrlError, Message: err.Error()})
+		return
+	}
+	_ = WriteControl(conn, Ctrl{Type: CtrlAck, Session: sess.ID()})
+	buffered, live, cancel := sess.Subscribe()
+	defer cancel()
+	s.streamToClient(conn, sess, buffered, live)
+}
+
+func (s *Server) handleAttach(conn net.Conn, cmd Ctrl) {
+	if cmd.Session == "" {
+		_ = WriteControl(conn, Ctrl{Type: CtrlError, Message: "attach requires a session id"})
+		return
+	}
+	buffered, live, cancel, err := s.opts.Manager.Attach(cmd.Session)
+	if err != nil {
+		_ = WriteControl(conn, Ctrl{Type: CtrlError, Message: err.Error()})
+		return
+	}
+	defer cancel()
+	sess, _ := s.opts.Manager.Get(cmd.Session)
+	_ = WriteControl(conn, Ctrl{Type: CtrlAck, Session: cmd.Session})
+	s.streamToClient(conn, sess, buffered, live)
+}
+
+// streamToClient writes the buffered history then live lines as CtrlData frames,
+// finishing with CtrlEnd (or CtrlError if the session failed). A write error
+// (client disconnected) ends the stream without affecting the session.
+func (s *Server) streamToClient(conn net.Conn, sess *Session, buffered []string, live <-chan string) {
+	for _, line := range buffered {
+		if err := WriteControl(conn, Ctrl{Type: CtrlData, Line: line}); err != nil {
+			return
+		}
+	}
+	for {
+		select {
+		case line, ok := <-live:
+			if !ok {
+				s.finishStream(conn, sess)
+				return
+			}
+			if err := WriteControl(conn, Ctrl{Type: CtrlData, Line: line}); err != nil {
+				return
+			}
+		case <-s.done:
+			_ = WriteControl(conn, Ctrl{Type: CtrlEnd, Message: "daemon shutting down"})
+			return
+		}
+	}
+}
+
+func (s *Server) finishStream(conn net.Conn, sess *Session) {
+	if sess != nil {
+		if err := sess.Err(); err != nil {
+			_ = WriteControl(conn, Ctrl{Type: CtrlError, Session: sess.ID(), Message: err.Error()})
+			return
+		}
+	}
+	_ = WriteControl(conn, Ctrl{Type: CtrlEnd})
+}
+
+func (s *Server) handleStatus(conn net.Conn) {
+	report := StatusReport{
+		PID:        os.Getpid(),
+		Version:    s.opts.Version,
+		Socket:     s.opts.Paths.Socket,
+		StartedAt:  s.startedAt,
+		PoolSize:   s.opts.Pool.Size(),
+		Workers:    s.opts.Pool.WorkerStats(),
+		Sessions:   s.opts.Manager.Statuses(),
+		QueueDepth: s.opts.Pool.QueueDepth(),
+	}
+	_ = WriteControl(conn, Ctrl{Type: CtrlStatusResult, Status: &report})
+}

internal/daemon/server_test.go

@@ -0,0 +1,176 @@
+package daemon
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func newTestServer(t *testing.T, launcher Launcher) (*Server, Paths) {
+	t.Helper()
+	dir := t.TempDir()
+	paths := Paths{
+		Socket: filepath.Join(dir, "d.sock"),
+		Lock:   filepath.Join(dir, "d.lock"),
+		Status: filepath.Join(dir, "d.status"),
+	}
+	pool, err := NewPool(PoolOptions{Size: 2, Launcher: launcher, KillTimeout: 200 * time.Millisecond})
+	if err != nil {
+		t.Fatalf("NewPool: %v", err)
+	}
+	mgr, err := NewSessionManager(SessionManagerOptions{Pool: pool})
+	if err != nil {
+		t.Fatalf("NewSessionManager: %v", err)
+	}
+	srv, err := NewServer(ServerOptions{Paths: paths, Manager: mgr, Pool: pool})
+	if err != nil {
+		t.Fatalf("NewServer: %v", err)
+	}
+	return srv, paths
+}
+
+func waitForFile(t *testing.T, path string) {
+	t.Helper()
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		if _, err := os.Stat(path); err == nil {
+			return
+		}
+		time.Sleep(2 * time.Millisecond)
+	}
+	t.Fatalf("file %s did not appear within timeout", path)
+}
+
+func TestServerEndToEnd(t *testing.T) {
+	out := []string{`{"type":"event","seq":1}`, `{"type":"event","seq":2}`}
+	launcher, _ := seqLauncher(&fakeWorker{pid: 1, out: out, exitCode: 0})
+	srv, paths := newTestServer(t, launcher)
+
+	serveErr := make(chan error, 1)
+	go func() { serveErr <- srv.Serve() }()
+	waitForFile(t, paths.Status)
+
+	// --- run a session and collect its stream-json output ---
+	runClient, err := Dial(paths.Socket)
+	if err != nil {
+		t.Fatalf("Dial(run): %v", err)
+	}
+	var got []string
+	if err := runClient.Run("s1", "", "hello", nil, func(line string) { got = append(got, line) }); err != nil {
+		t.Fatalf("Run: %v", err)
+	}
+	runClient.Close()
+	if len(got) != 2 || got[0] != out[0] || got[1] != out[1] {
+		t.Fatalf("streamed lines = %v, want %v", got, out)
+	}
+
+	// --- status reflects the session ---
+	statusClient, err := Dial(paths.Socket)
+	if err != nil {
+		t.Fatalf("Dial(status): %v", err)
+	}
+	report, err := statusClient.Status()
+	statusClient.Close()
+	if err != nil {
+		t.Fatalf("Status: %v", err)
+	}
+	if report.PoolSize != 2 {
+		t.Fatalf("status PoolSize = %d, want 2", report.PoolSize)
+	}
+	foundSession := false
+	for _, s := range report.Sessions {
+		if s.ID == "s1" {
+			foundSession = true
+			if s.State != string(SessionDone) {
+				t.Fatalf("session s1 state = %s, want done", s.State)
+			}
+		}
+	}
+	if !foundSession {
+		t.Fatalf("status missing session s1: %+v", report.Sessions)
+	}
+
+	// --- attach to the finished session sees the buffered history ---
+	attachClient, err := Dial(paths.Socket)
+	if err != nil {
+		t.Fatalf("Dial(attach): %v", err)
+	}
+	var attached []string
+	if err := attachClient.Attach("s1", func(line string) { attached = append(attached, line) }); err != nil {
+		t.Fatalf("Attach: %v", err)
+	}
+	attachClient.Close()
+	if len(attached) != 2 {
+		t.Fatalf("attach lines = %v, want 2 buffered", attached)
+	}
+
+	// --- graceful stop, daemon cleans up ---
+	stopClient, err := Dial(paths.Socket)
+	if err != nil {
+		t.Fatalf("Dial(stop): %v", err)
+	}
+	if err := stopClient.Shutdown(); err != nil {
+		t.Fatalf("Shutdown: %v", err)
+	}
+	stopClient.Close()
+
+	select {
+	case err := <-serveErr:
+		if err != nil {
+			t.Fatalf("Serve returned error: %v", err)
+		}
+	case <-time.After(3 * time.Second):
+		t.Fatal("Serve did not return after shutdown")
+	}
+	// Socket, status, and lock files are removed on exit.
+	for _, p := range []string{paths.Socket, paths.Status, paths.Lock} {
+		if _, err := os.Stat(p); !errors.Is(err, os.ErrNotExist) {
+			t.Fatalf("file %s not cleaned up after shutdown: %v", p, err)
+		}
+	}
+}
+
+func TestServerSecondInstanceFails(t *testing.T) {
+	block := make(chan struct{})
+	defer close(block)
+	launcher, _ := seqLauncher(&fakeWorker{pid: 1, waitCh: block})
+	srv1, paths := newTestServer(t, launcher)
+
+	serveErr := make(chan error, 1)
+	go func() { serveErr <- srv1.Serve() }()
+	waitForFile(t, paths.Status)
+
+	// A second server on the same paths must refuse to start (single instance).
+	pool2, _ := NewPool(PoolOptions{Size: 1, Launcher: launcher})
+	mgr2, _ := NewSessionManager(SessionManagerOptions{Pool: pool2})
+	srv2, _ := NewServer(ServerOptions{Paths: paths, Manager: mgr2, Pool: pool2})
+	if err := srv2.Serve(); !errors.Is(err, ErrAlreadyRunning) {
+		t.Fatalf("second Serve err = %v, want ErrAlreadyRunning", err)
+	}
+
+	srv1.Shutdown()
+	<-serveErr
+}
+
+func TestServerRejectsUnknownCommand(t *testing.T) {
+	block := make(chan struct{})
+	defer close(block)
+	launcher, _ := seqLauncher(&fakeWorker{pid: 1, waitCh: block})
+	srv, paths := newTestServer(t, launcher)
+	go func() { _ = srv.Serve() }()
+	defer srv.Shutdown()
+	waitForFile(t, paths.Status)
+
+	client, err := Dial(paths.Socket)
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	defer client.Close()
+	// Run with an empty session id is rejected with an error frame.
+	err = client.Run("", "", "hi", nil, nil)
+	if err == nil {
+		t.Fatal("run with empty session id must return an error")
+	}
+}

internal/daemon/session.go

@@ -0,0 +1,306 @@
+package daemon
+
+import (
+	"context"
+	"errors"
+	"sort"
+	"sync"
+)
+
+// Session/lease/roster model. Mirrors reference-daemon-code-agent-js/
+// session-manager.js (sessionID -> worker + metrics), lease.js (one active
+// request per worker) and roster.js (the live session registry). Because zero's
+// `exec` worker is one-shot, each session is served by exactly one worker via
+// Pool.Run, so "one active request per worker" holds inherently and the pool's
+// bounded slots provide the queue-when-full behavior.
+
+// SessionState is a session's lifecycle phase.
+type SessionState string
+
+const (
+	// SessionQueued: created, waiting for a free pool slot.
+	SessionQueued SessionState = "queued"
+	// SessionRunning: a worker is leased and producing output.
+	SessionRunning SessionState = "running"
+	// SessionDone: the worker finished cleanly.
+	SessionDone SessionState = "done"
+	// SessionFailed: the worker failed permanently / the run errored.
+	SessionFailed SessionState = "failed"
+)
+
+// ErrSessionExists is returned when starting a session ID already in use.
+var ErrSessionExists = errors.New("daemon: session already exists")
+
+// ErrSessionNotFound is returned by Get/Attach for an unknown session ID.
+var ErrSessionNotFound = errors.New("daemon: session not found")
+
+const defaultSessionBuffer = 1024
+
+// Session is one routed agent run. It buffers recent output (so a late `attach`
+// sees history) and fans live lines out to subscribers. It implements the pool's
+// Sink (Line) and the lease "started" hook (Started).
+type Session struct {
+	id  string
+	cwd string
+
+	mu          sync.Mutex
+	state       SessionState
+	buffer      []string
+	maxBuffer   int
+	lines       int
+	finished    bool
+	err         error
+	exitCode    int
+	subscribers map[int]chan string
+	nextSub     int
+	done        chan struct{}
+}
+
+func newSession(id, cwd string, maxBuffer int) *Session {
+	if maxBuffer <= 0 {
+		maxBuffer = defaultSessionBuffer
+	}
+	return &Session{
+		id:          id,
+		cwd:         cwd,
+		state:       SessionQueued,
+		maxBuffer:   maxBuffer,
+		subscribers: map[int]chan string{},
+		done:        make(chan struct{}),
+	}
+}
+
+// ID returns the session ID.
+func (s *Session) ID() string { return s.id }
+
+// Done is closed when the session finishes (success or failure).
+func (s *Session) Done() <-chan struct{} { return s.done }
+
+// Err returns the terminal error (nil on clean completion); valid after Done.
+func (s *Session) Err() error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.err
+}
+
+// State returns the current lifecycle phase.
+func (s *Session) State() SessionState {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.state
+}
+
+// Started marks the session running once the pool leases a worker (lease hook).
+func (s *Session) Started() {
+	s.mu.Lock()
+	if s.state == SessionQueued {
+		s.state = SessionRunning
+	}
+	s.mu.Unlock()
+}
+
+// Line records and broadcasts one stream-json output line.
+func (s *Session) Line(line string) {
+	s.mu.Lock()
+	s.lines++
+	s.buffer = append(s.buffer, line)
+	if len(s.buffer) > s.maxBuffer {
+		// Drop the oldest line; the ring keeps only the most recent maxBuffer.
+		s.buffer = s.buffer[len(s.buffer)-s.maxBuffer:]
+	}
+	subs := make([]chan string, 0, len(s.subscribers))
+	for _, ch := range s.subscribers {
+		subs = append(subs, ch)
+	}
+	s.mu.Unlock()
+	for _, ch := range subs {
+		// Non-blocking: a slow/stalled subscriber must not stall the worker pump.
+		// Dropped live lines remain available via the buffer for a fresh attach.
+		select {
+		case ch <- line:
+		default:
+		}
+	}
+}
+
+func (s *Session) finish(exitCode int, err error) {
+	s.mu.Lock()
+	s.finished = true
+	s.exitCode = exitCode
+	s.err = err
+	if err != nil {
+		s.state = SessionFailed
+	} else {
+		s.state = SessionDone
+	}
+	subs := s.subscribers
+	s.subscribers = map[int]chan string{}
+	s.mu.Unlock()
+	for _, ch := range subs {
+		close(ch)
+	}
+	close(s.done)
+}
+
+// Subscribe returns the buffered history plus a channel of subsequent live lines
+// and a cancel func. If the session has already finished, the live channel is
+// returned already closed. Mirrors attach.js.
+func (s *Session) Subscribe() (buffered []string, live <-chan string, cancel func()) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	buffered = append([]string(nil), s.buffer...)
+	if s.finished {
+		ch := make(chan string)
+		close(ch)
+		return buffered, ch, func() {}
+	}
+	id := s.nextSub
+	s.nextSub++
+	ch := make(chan string, 256)
+	s.subscribers[id] = ch
+	cancel = func() {
+		s.mu.Lock()
+		if c, ok := s.subscribers[id]; ok {
+			delete(s.subscribers, id)
+			close(c)
+		}
+		s.mu.Unlock()
+	}
+	return buffered, ch, cancel
+}
+
+func (s *Session) status() SessionStatus {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return SessionStatus{ID: s.id, State: string(s.state), Lines: s.lines}
+}
+
+func (s *Session) isFinished() bool {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.finished
+}
+
+// defaultMaxSessions bounds the retained session registry so a long-running
+// daemon does not accumulate finished sessions without limit.
+const defaultMaxSessions = 256
+
+// SessionManager owns the live session registry and routes each session to a
+// pool worker. Mirrors session-manager.js + roster.js. Finished sessions are
+// retained (so a late `attach` sees history) up to MaxSessions, past which the
+// oldest FINISHED ones are evicted; running/queued sessions are never evicted.
+type SessionManager struct {
+	pool        *Pool
+	maxBuffer   int
+	maxSessions int
+
+	mu       sync.Mutex
+	sessions map[string]*Session
+	order    []string // creation order, for FIFO eviction of finished sessions
+}
+
+// SessionManagerOptions configures a SessionManager.
+type SessionManagerOptions struct {
+	Pool      *Pool
+	MaxBuffer int // per-session output ring size; 0 => default
+	// MaxSessions caps the retained session registry; 0 => default. The oldest
+	// FINISHED sessions are evicted once the cap is exceeded.
+	MaxSessions int
+}
+
+// NewSessionManager builds a manager over pool.
+func NewSessionManager(opts SessionManagerOptions) (*SessionManager, error) {
+	if opts.Pool == nil {
+		return nil, errors.New("daemon: session manager requires a Pool")
+	}
+	maxSessions := opts.MaxSessions
+	if maxSessions <= 0 {
+		maxSessions = defaultMaxSessions
+	}
+	return &SessionManager{
+		pool:        opts.Pool,
+		maxBuffer:   opts.MaxBuffer,
+		maxSessions: maxSessions,
+		sessions:    map[string]*Session{},
+	}, nil
+}
+
+// Start creates a session for spec and dispatches it to the pool. It returns the
+// Session immediately (non-blocking); the run proceeds in the background and the
+// session transitions queued -> running -> done/failed. A duplicate ID is
+// rejected with ErrSessionExists.
+func (m *SessionManager) Start(ctx context.Context, spec WorkerSpec) (*Session, error) {
+	m.mu.Lock()
+	if _, exists := m.sessions[spec.Session]; exists {
+		m.mu.Unlock()
+		return nil, ErrSessionExists
+	}
+	sess := newSession(spec.Session, spec.Cwd, m.maxBuffer)
+	m.sessions[spec.Session] = sess
+	m.order = append(m.order, spec.Session)
+	m.pruneLocked()
+	m.mu.Unlock()
+
+	go func() {
+		code, err := m.pool.Run(ctx, spec, sess)
+		sess.finish(code, err)
+	}()
+	return sess, nil
+}
+
+// pruneLocked evicts the oldest FINISHED sessions while the registry exceeds
+// maxSessions, so a long-running daemon does not retain finished sessions without
+// bound. Running/queued sessions are never evicted (a transient burst can exceed
+// the cap until those finish). Caller must hold m.mu.
+func (m *SessionManager) pruneLocked() {
+	if len(m.sessions) <= m.maxSessions {
+		return
+	}
+	kept := m.order[:0]
+	for _, id := range m.order {
+		s, ok := m.sessions[id]
+		if !ok {
+			continue // already removed
+		}
+		if len(m.sessions) > m.maxSessions && s.isFinished() {
+			delete(m.sessions, id)
+			continue
+		}
+		kept = append(kept, id)
+	}
+	m.order = kept
+}
+
+// Get returns a session by ID.
+func (m *SessionManager) Get(id string) (*Session, bool) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	s, ok := m.sessions[id]
+	return s, ok
+}
+
+// Attach returns the buffered history + live stream for an existing session.
+func (m *SessionManager) Attach(id string) (buffered []string, live <-chan string, cancel func(), err error) {
+	s, ok := m.Get(id)
+	if !ok {
+		return nil, nil, nil, ErrSessionNotFound
+	}
+	b, l, c := s.Subscribe()
+	return b, l, c, nil
+}
+
+// Statuses returns a snapshot of all sessions, sorted by ID for stable output.
+func (m *SessionManager) Statuses() []SessionStatus {
+	m.mu.Lock()
+	sessions := make([]*Session, 0, len(m.sessions))
+	for _, s := range m.sessions {
+		sessions = append(sessions, s)
+	}
+	m.mu.Unlock()
+	out := make([]SessionStatus, 0, len(sessions))
+	for _, s := range sessions {
+		out = append(out, s.status())
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].ID < out[j].ID })
+	return out
+}

internal/daemon/session_test.go

@@ -0,0 +1,179 @@
+package daemon
+
+import (
+	"context"
+	"errors"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func drain(t *testing.T, buffered []string, live <-chan string) []string {
+	t.Helper()
+	got := append([]string(nil), buffered...)
+	timeout := time.After(2 * time.Second)
+	for {
+		select {
+		case line, ok := <-live:
+			if !ok {
+				return got
+			}
+			got = append(got, line)
+		case <-timeout:
+			t.Fatal("timed out draining session stream")
+		}
+	}
+}
+
+func TestSessionStartRoutesAndStreams(t *testing.T) {
+	launcher, _ := seqLauncher(&fakeWorker{pid: 1, out: []string{"e1", "e2", "e3"}, exitCode: 0})
+	pool, _ := NewPool(PoolOptions{Size: 2, Launcher: launcher})
+	mgr, err := NewSessionManager(SessionManagerOptions{Pool: pool})
+	if err != nil {
+		t.Fatalf("NewSessionManager: %v", err)
+	}
+	sess, err := mgr.Start(context.Background(), WorkerSpec{Session: "s1"})
+	if err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+	buffered, live, cancel := sess.Subscribe()
+	defer cancel()
+	got := drain(t, buffered, live)
+	if len(got) != 3 || got[0] != "e1" || got[2] != "e3" {
+		t.Fatalf("streamed lines = %v, want [e1 e2 e3]", got)
+	}
+	<-sess.Done()
+	if sess.State() != SessionDone {
+		t.Fatalf("state = %s, want done", sess.State())
+	}
+}
+
+func TestSessionDuplicateIDRejected(t *testing.T) {
+	block := make(chan struct{})
+	defer close(block)
+	launcher, _ := seqLauncher(&fakeWorker{pid: 1, waitCh: block})
+	pool, _ := NewPool(PoolOptions{Size: 2, Launcher: launcher})
+	mgr, _ := NewSessionManager(SessionManagerOptions{Pool: pool})
+	if _, err := mgr.Start(context.Background(), WorkerSpec{Session: "dup"}); err != nil {
+		t.Fatalf("first Start: %v", err)
+	}
+	if _, err := mgr.Start(context.Background(), WorkerSpec{Session: "dup"}); !errors.Is(err, ErrSessionExists) {
+		t.Fatalf("second Start err = %v, want ErrSessionExists", err)
+	}
+}
+
+func TestSessionLeaseQueuesWhenPoolFull(t *testing.T) {
+	block := make(chan struct{})
+	a := &fakeWorker{pid: 1, waitCh: block}
+	b := &fakeWorker{pid: 2, out: []string{"b1"}, exitCode: 0}
+	launcher, calls := seqLauncher(a, b)
+	pool, _ := NewPool(PoolOptions{Size: 1, Launcher: launcher})
+	mgr, _ := NewSessionManager(SessionManagerOptions{Pool: pool})
+
+	sa, _ := mgr.Start(context.Background(), WorkerSpec{Session: "a"})
+	waitFor(t, func() bool { return sa.State() == SessionRunning })
+
+	sb, _ := mgr.Start(context.Background(), WorkerSpec{Session: "b"})
+	// b must stay queued (its worker not yet launched) while a holds the slot.
+	time.Sleep(50 * time.Millisecond)
+	if sb.State() != SessionQueued {
+		t.Fatalf("session b state = %s, want queued while pool full", sb.State())
+	}
+	if n := atomic.LoadInt32(calls); n != 1 {
+		t.Fatalf("launcher calls = %d, want 1 (b not launched yet)", n)
+	}
+
+	close(block) // a finishes, slot frees, b proceeds
+	<-sb.Done()
+	if sb.State() != SessionDone {
+		t.Fatalf("session b state = %s, want done", sb.State())
+	}
+	if n := atomic.LoadInt32(calls); n != 2 {
+		t.Fatalf("launcher calls = %d, want 2 after slot freed", n)
+	}
+}
+
+func TestSessionAttachAfterFinishSeesBuffer(t *testing.T) {
+	launcher, _ := seqLauncher(&fakeWorker{pid: 1, out: []string{"x", "y"}, exitCode: 0})
+	pool, _ := NewPool(PoolOptions{Size: 1, Launcher: launcher})
+	mgr, _ := NewSessionManager(SessionManagerOptions{Pool: pool})
+	sess, _ := mgr.Start(context.Background(), WorkerSpec{Session: "s"})
+	<-sess.Done()
+
+	buffered, live, cancel, err := mgr.Attach("s")
+	if err != nil {
+		t.Fatalf("Attach: %v", err)
+	}
+	defer cancel()
+	got := drain(t, buffered, live)
+	if len(got) != 2 || got[0] != "x" || got[1] != "y" {
+		t.Fatalf("attach buffered = %v, want [x y]", got)
+	}
+	if _, _, _, err := mgr.Attach("missing"); !errors.Is(err, ErrSessionNotFound) {
+		t.Fatalf("Attach(missing) err = %v, want ErrSessionNotFound", err)
+	}
+}
+
+func TestSessionManagerEvictsFinishedOverCap(t *testing.T) {
+	launcher, _ := seqLauncher(
+		&fakeWorker{pid: 1, out: []string{"a"}, exitCode: 0},
+		&fakeWorker{pid: 2, out: []string{"b"}, exitCode: 0},
+		&fakeWorker{pid: 3, out: []string{"c"}, exitCode: 0},
+	)
+	pool, _ := NewPool(PoolOptions{Size: 2, Launcher: launcher})
+	mgr, _ := NewSessionManager(SessionManagerOptions{Pool: pool, MaxSessions: 2})
+
+	for _, id := range []string{"s1", "s2", "s3"} {
+		s, err := mgr.Start(context.Background(), WorkerSpec{Session: id})
+		if err != nil {
+			t.Fatalf("Start(%s): %v", id, err)
+		}
+		<-s.Done() // finish before starting the next so prune can evict it
+	}
+
+	// Past the cap of 2, the oldest FINISHED session (s1) is evicted; the two
+	// newest are retained.
+	if _, ok := mgr.Get("s1"); ok {
+		t.Fatal("oldest finished session must be evicted past the cap")
+	}
+	if _, ok := mgr.Get("s2"); !ok {
+		t.Fatal("s2 must be retained")
+	}
+	if _, ok := mgr.Get("s3"); !ok {
+		t.Fatal("s3 (newest) must be retained")
+	}
+}
+
+func TestSessionManagerKeepsRunningOverCap(t *testing.T) {
+	// All sessions are running (workers block), so none are evicted even past cap.
+	block := make(chan struct{})
+	defer close(block)
+	launcher, _ := seqLauncher(
+		&fakeWorker{pid: 1, waitCh: block},
+		&fakeWorker{pid: 2, waitCh: block},
+	)
+	pool, _ := NewPool(PoolOptions{Size: 2, Launcher: launcher})
+	mgr, _ := NewSessionManager(SessionManagerOptions{Pool: pool, MaxSessions: 1})
+
+	s1, _ := mgr.Start(context.Background(), WorkerSpec{Session: "r1"})
+	s2, _ := mgr.Start(context.Background(), WorkerSpec{Session: "r2"})
+	waitFor(t, func() bool { return s1.State() == SessionRunning && s2.State() == SessionRunning })
+	if _, ok := mgr.Get("r1"); !ok {
+		t.Fatal("a running session must never be evicted, even past the cap")
+	}
+	if _, ok := mgr.Get("r2"); !ok {
+		t.Fatal("a running session must never be evicted, even past the cap")
+	}
+}
+
+func TestSessionStatuses(t *testing.T) {
+	launcher, _ := seqLauncher(&fakeWorker{pid: 1, out: []string{"l"}, exitCode: 0})
+	pool, _ := NewPool(PoolOptions{Size: 1, Launcher: launcher})
+	mgr, _ := NewSessionManager(SessionManagerOptions{Pool: pool})
+	sess, _ := mgr.Start(context.Background(), WorkerSpec{Session: "only"})
+	<-sess.Done()
+	st := mgr.Statuses()
+	if len(st) != 1 || st[0].ID != "only" || st[0].State != string(SessionDone) || st[0].Lines != 1 {
+		t.Fatalf("statuses = %+v, want one done session with 1 line", st)
+	}
+}

internal/daemon/socket.go

@@ -0,0 +1,27 @@
+package daemon
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+// maxUnixSocketPath bounds the socket path to the smallest platform sun_path
+// limit so we surface a clear error instead of a cryptic bind failure. macOS
+// allows 104 bytes incl. the NUL (so 103 chars); Linux allows 108. 103 is the
+// safe cross-platform ceiling.
+const maxUnixSocketPath = 103
+
+// secureSocketParent creates the socket's parent directory owner-only (0700 on
+// POSIX; on Windows the per-user profile directory is already ACL-restricted).
+func secureSocketParent(socketPath string) error {
+	return os.MkdirAll(filepath.Dir(socketPath), 0o700)
+}
+
+// checkSocketPathLength rejects an over-long unix socket path before bind.
+func checkSocketPathLength(socketPath string) error {
+	if len(socketPath) > maxUnixSocketPath {
+		return fmt.Errorf("daemon: socket path too long (%d > %d): %s", len(socketPath), maxUnixSocketPath, socketPath)
+	}
+	return nil
+}

internal/daemon/socket_posix.go

@@ -0,0 +1,12 @@
+//go:build !windows
+
+package daemon
+
+import "os"
+
+// hardenSocketFile restricts the control socket to its owner (0600) so no other
+// local user can connect. Combined with the 0700 parent directory this makes the
+// control plane owner-only, as required by the security model.
+func hardenSocketFile(path string) error {
+	return os.Chmod(path, 0o600)
+}

internal/daemon/socket_windows.go

@@ -0,0 +1,9 @@
+//go:build windows
+
+package daemon
+
+// hardenSocketFile is a no-op on Windows: AF_UNIX socket files do not honor POSIX
+// mode bits, and the daemon places the socket under the per-user profile
+// directory, which is already ACL-restricted to the owner. A dedicated restricted
+// ACL (or a named pipe with an explicit DACL) is a documented follow-up.
+func hardenSocketFile(string) error { return nil }

internal/daemon/status.go

@@ -0,0 +1,43 @@
+package daemon
+
+import "time"
+
+// StatusReport is the daemon/worker/session snapshot returned by `zero daemon
+// status` (CtrlStatusResult). Mirrors reference-daemon-code-agent-js/status.js.
+type StatusReport struct {
+	PID        int             `json:"pid"`
+	Version    int             `json:"version"`
+	Socket     string          `json:"socket"`
+	StartedAt  time.Time       `json:"startedAt"`
+	PoolSize   int             `json:"poolSize"`
+	Workers    []WorkerStatus  `json:"workers"`
+	Sessions   []SessionStatus `json:"sessions"`
+	QueueDepth int             `json:"queueDepth"`
+}
+
+// WorkerStatus is one worker's lifecycle snapshot.
+type WorkerStatus struct {
+	ID                 int    `json:"id"`
+	PID                int    `json:"pid"`
+	State              string `json:"state"`
+	ConsecutiveCrashes int    `json:"consecutiveCrashes"`
+	Restarts           int    `json:"restarts"`
+	Session            string `json:"session,omitempty"`
+}
+
+// SessionStatus is one session's routing/metrics snapshot.
+type SessionStatus struct {
+	ID    string `json:"id"`
+	State string `json:"state"`
+	Lines int    `json:"lines"`
+}
+
+// StatusFile is the on-disk daemon status document (pid, socket, version,
+// started-at), written next to the lock so `status`/`stop` work without a live
+// connection. Mirrors supervisor.js's status file.
+type StatusFile struct {
+	PID       int       `json:"pid"`
+	Socket    string    `json:"socket"`
+	Version   int       `json:"version"`
+	StartedAt time.Time `json:"startedAt"`
+}

internal/doctor/doctor.go

@@ -158,6 +158,9 @@ func providerModelCheck(profile config.ProviderProfile) Check {
 	if emptyProviderProfile(profile) {
 		return check("provider.model", "Provider model", StatusWarn, "Model validity was skipped because provider config is unavailable.", nil)
 	}
+	if strings.TrimSpace(profile.Model) == "" {
+		return check("provider.model", "Provider model", StatusFail, "Provider model is required.", map[string]any{"provider": providerName(profile)})
+	}
 	registry, err := modelregistry.DefaultRegistry()
 	if err != nil {
 		return check("provider.model", "Provider model", StatusFail, "Model registry could not be loaded: "+err.Error(), nil)
@@ -165,7 +168,7 @@ func providerModelCheck(profile config.ProviderProfile) Check {
 	model, err := registry.Require(profile.Model)
 	if err != nil {
 		if profile.ProviderKind == config.ProviderKindOpenAICompatible || profile.ProviderKind == config.ProviderKindAnthropicCompat {
-			return check("provider.model", "Provider model", StatusWarn, fmt.Sprintf("Custom %s model was not found in the Zero registry; runtime will pass it through to the configured provider.", profile.ProviderKind), map[string]any{"model": profile.Model, "provider": providerName(profile)})
+			return check("provider.model", "Provider model", StatusWarn, fmt.Sprintf("Custom %s model was not found in the Zero registry; runtime will pass it through to the configured provider. Run `zero doctor --connectivity` to validate the endpoint and auth.", profile.ProviderKind), map[string]any{"model": profile.Model, "provider": providerName(profile)})
 		}
 		return check("provider.model", "Provider model", StatusFail, "Provider model is invalid: "+err.Error(), map[string]any{"model": profile.Model})
 	}

internal/doctor/doctor_test.go

@@ -86,6 +86,96 @@ func TestRunReportWarnsForUnknownOpenAICompatibleModel(t *testing.T) {
 	}
 }
 
+func TestProviderModelUnknownOpenAICompatibleModelWarnsPassThrough(t *testing.T) {
+	report := Run(Options{
+		Now:     fixedDoctorClock("2026-06-04T15:45:00Z"),
+		Runtime: "go",
+		Provider: config.ProviderProfile{
+			Name:         "openrouter",
+			ProviderKind: config.ProviderKindOpenAICompatible,
+			BaseURL:      "https://openrouter.ai/api/v1",
+			Model:        "vendor/new-dynamic-model",
+		},
+	})
+
+	if !report.OK {
+		t.Fatalf("unknown openai-compatible model should warn, not fail: %#v", report)
+	}
+	check := report.Check("provider.model")
+	if check == nil {
+		t.Fatalf("expected provider.model check: %#v", report.Checks)
+	}
+	if check.Status != StatusWarn {
+		t.Fatalf("provider.model status = %s, want warn: %#v", check.Status, check)
+	}
+	if !strings.Contains(check.Message, "runtime will pass it through") || !strings.Contains(check.Message, "doctor --connectivity") {
+		t.Fatalf("provider.model message should explain pass-through connectivity validation, got %q", check.Message)
+	}
+}
+
+func TestProviderModelMissingModelFails(t *testing.T) {
+	report := Run(Options{
+		Now:     fixedDoctorClock("2026-06-04T15:45:00Z"),
+		Runtime: "go",
+		Provider: config.ProviderProfile{
+			Name:         "ollama-cloud",
+			ProviderKind: config.ProviderKindOpenAICompatible,
+			BaseURL:      "https://ollama.com/v1",
+			Model:        "   ",
+		},
+	})
+
+	if report.OK {
+		t.Fatalf("missing model should fail: %#v", report)
+	}
+	check := report.Check("provider.model")
+	if check == nil || check.Status != StatusFail || !strings.Contains(check.Message, "required") {
+		t.Fatalf("expected missing model failure: %#v", report.Checks)
+	}
+}
+
+func TestProviderModelBuiltInUnknownModelFails(t *testing.T) {
+	report := Run(Options{
+		Now:     fixedDoctorClock("2026-06-04T15:45:00Z"),
+		Runtime: "go",
+		Provider: config.ProviderProfile{
+			Name:         "openai",
+			ProviderKind: config.ProviderKindOpenAI,
+			BaseURL:      config.OpenAIBaseURL,
+			Model:        "vendor/new-dynamic-model",
+		},
+	})
+
+	if report.OK {
+		t.Fatalf("built-in provider unknown model should fail: %#v", report)
+	}
+	check := report.Check("provider.model")
+	if check == nil || check.Status != StatusFail || !strings.Contains(check.Message, "unknown Zero model") {
+		t.Fatalf("expected built-in unknown model failure: %#v", report.Checks)
+	}
+}
+
+func TestProviderModelRegisteredProviderMismatchFails(t *testing.T) {
+	report := Run(Options{
+		Now:     fixedDoctorClock("2026-06-04T15:45:00Z"),
+		Runtime: "go",
+		Provider: config.ProviderProfile{
+			Name:         "openai",
+			ProviderKind: config.ProviderKindOpenAI,
+			BaseURL:      config.OpenAIBaseURL,
+			Model:        "gemini-2.5-pro",
+		},
+	})
+
+	if report.OK {
+		t.Fatalf("registered provider mismatch should fail: %#v", report)
+	}
+	check := report.Check("provider.model")
+	if check == nil || check.Status != StatusFail || !strings.Contains(check.Message, "not available for provider") {
+		t.Fatalf("expected registered provider mismatch failure: %#v", report.Checks)
+	}
+}
+
 func writeDoctorConfig(t *testing.T, body string) string {
 	t.Helper()
 	dir := t.TempDir()

internal/imageinput/pdf_test.go

@@ -10,6 +10,8 @@ import (
 	"testing"
 )
 
+const minimalPDFTextChunkSize = 80
+
 // buildMinimalPDF assembles a tiny, single-page PDF whose content stream draws
 // the given text. It computes a real cross-reference table and trailer so a
 // pure-Go PDF parser (ledongthuc/pdf) accepts it. Generating the fixture in-test
@@ -28,10 +30,11 @@ func buildMinimalPDF(text string) []byte {
 	startObj() // object 2: page tree
 	buf.WriteString("2 0 obj\n<< /Type /Pages /Kids [3 0 R] /Count 1 >>\nendobj\n")
 
+	pageHeight := minimalPDFPageHeight(text)
 	startObj() // object 3: page
-	buf.WriteString("3 0 obj\n<< /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] /Resources << /Font << /F1 5 0 R >> >> /Contents 4 0 R >>\nendobj\n")
+	buf.WriteString("3 0 obj\n<< /Type /Page /Parent 2 0 R /MediaBox [0 0 612 " + strconv.Itoa(pageHeight) + "] /Resources << /Font << /F1 5 0 R >> >> /Contents 4 0 R >>\nendobj\n")
 
-	content := "BT /F1 24 Tf 72 700 Td (" + text + ") Tj ET"
+	content := minimalPDFTextContent(text, pageHeight-92)
 	startObj() // object 4: content stream
 	buf.WriteString("4 0 obj\n<< /Length " + strconv.Itoa(len(content)) + " >>\nstream\n")
 	buf.WriteString(content)
@@ -52,6 +55,56 @@ func buildMinimalPDF(text string) []byte {
 	return buf.Bytes()
 }
 
+func minimalPDFPageHeight(text string) int {
+	lines := (len(text) + minimalPDFTextChunkSize - 1) / minimalPDFTextChunkSize
+	if lines < 1 {
+		lines = 1
+	}
+	height := 184 + lines*10
+	if height < 792 {
+		return 792
+	}
+	return height
+}
+
+func minimalPDFTextContent(text string, startY int) string {
+	var content strings.Builder
+	content.WriteString("BT /F1 8 Tf 10 TL 72 ")
+	content.WriteString(strconv.Itoa(startY))
+	content.WriteString(" Td ")
+	for index := 0; len(text) > 0; index++ {
+		if index > 0 {
+			content.WriteString(" T* ")
+		}
+		chunk := text
+		if len(chunk) > minimalPDFTextChunkSize {
+			cut := minimalPDFTextChunkSize
+			for cut > 0 && !utf8RuneStart(chunk[cut]) {
+				cut--
+			}
+			if cut == 0 {
+				cut = minimalPDFTextChunkSize
+			}
+			chunk = text[:cut]
+		}
+		content.WriteString("(")
+		content.WriteString(escapePDFLiteral(chunk))
+		content.WriteString(") Tj")
+		text = text[len(chunk):]
+	}
+	content.WriteString(" ET")
+	return content.String()
+}
+
+func escapePDFLiteral(text string) string {
+	text = strings.ReplaceAll(text, `\`, `\\`)
+	text = strings.ReplaceAll(text, `(`, `\(`)
+	text = strings.ReplaceAll(text, `)`, `\)`)
+	text = strings.ReplaceAll(text, "\r", `\r`)
+	text = strings.ReplaceAll(text, "\n", `\n`)
+	return text
+}
+
 func TestIsPDF(t *testing.T) {
 	if !isPDF(buildMinimalPDF("hi")) {
 		t.Fatal("isPDF should accept real %PDF- bytes")
@@ -159,7 +212,7 @@ func TestLoadDocumentTruncatesLongText(t *testing.T) {
 	// Many short lines so the *extracted text* (not the file) exceeds the cap.
 	var body strings.Builder
 	line := "The quick brown fox jumps over the lazy dog. "
-	for body.Len() < MaxDocumentTextBytes+4096 {
+	for body.Len() < MaxDocumentTextBytes+65536 {
 		body.WriteString(line)
 	}
 	if err := os.WriteFile(filepath.Join(root, "long.pdf"), buildMinimalPDF(body.String()), 0o644); err != nil {
@@ -173,7 +226,7 @@ func TestLoadDocumentTruncatesLongText(t *testing.T) {
 		t.Fatalf("capped text length %d exceeds cap %d (marker must be counted against the cap)", len(doc.Text), MaxDocumentTextBytes)
 	}
 	if !doc.Truncated {
-		t.Fatal("Truncated should be set when extracted text is capped")
+		t.Fatalf("Truncated should be set when extracted text is capped; extracted len=%d pages=%d", len(doc.Text), doc.Pages)
 	}
 	if !strings.Contains(doc.Text, documentTruncatedMarker) {
 		t.Fatal("truncated text should carry the truncation marker")

internal/keyring/keyring.go

@@ -0,0 +1,225 @@
+// Package keyring provides a small, dependency-free secret store backed by the
+// operating system's native credential tooling: the `security` keychain CLI on
+// macOS and `secret-tool` (libsecret) on Linux. It stores a single secret string
+// per (service, account). Windows and other platforms report unsupported.
+//
+// It shells out to the OS tools rather than taking a third-party dependency. On
+// macOS the secret is passed to `security` as an argument, so it is briefly
+// visible to other processes via the process list; on Linux the secret is passed
+// over stdin and is not exposed in the argument vector. Callers that need to keep
+// a secret out of the process list on macOS should prefer the file backend.
+package keyring
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"os/exec"
+	"runtime"
+	"strings"
+	"time"
+)
+
+// commandTimeout bounds a single keyring tool invocation.
+const commandTimeout = 10 * time.Second
+
+// ErrUnsupported is returned when no OS keyring backend is available for the
+// current platform.
+var ErrUnsupported = errors.New("keyring: no OS keyring backend on this platform")
+
+// runner executes name with args and optional stdin, returning stdout. It is the
+// single seam tests replace to drive the platform command logic without touching
+// a real keychain.
+type runner func(ctx context.Context, name string, stdin []byte, args ...string) ([]byte, error)
+
+// Keyring is an OS-native secret store.
+type Keyring struct {
+	run  runner
+	goos string
+}
+
+// New returns a Keyring for the current platform.
+func New() *Keyring {
+	return &Keyring{run: execRunner, goos: runtime.GOOS}
+}
+
+// Available reports whether this platform has a supported keyring backend. The
+// backing tool (`secret-tool` on Linux) must also be installed; a missing tool
+// surfaces as an error from Get/Set/Delete.
+func (k *Keyring) Available() bool {
+	switch k.goos {
+	case "darwin", "linux":
+		return true
+	default:
+		return false
+	}
+}
+
+// Set stores secret under (service, account), replacing any existing value.
+func (k *Keyring) Set(service, account, secret string) error {
+	if err := validate(service, account); err != nil {
+		return err
+	}
+	switch k.goos {
+	case "darwin":
+		// -U updates the item if it already exists rather than failing.
+		_, err := k.exec(nil, "security", "add-generic-password", "-U", "-s", service, "-a", account, "-w", secret)
+		return wrap("set", err)
+	case "linux":
+		// secret-tool reads the secret from stdin, keeping it out of the argv.
+		_, err := k.exec([]byte(secret), "secret-tool", "store", "--label", "zero", "service", service, "account", account)
+		return wrap("set", err)
+	default:
+		return ErrUnsupported
+	}
+}
+
+// Get returns the secret stored under (service, account). The bool is false when
+// no entry exists (which is not an error).
+func (k *Keyring) Get(service, account string) (string, bool, error) {
+	if err := validate(service, account); err != nil {
+		return "", false, err
+	}
+	switch k.goos {
+	case "darwin":
+		out, err := k.exec(nil, "security", "find-generic-password", "-s", service, "-a", account, "-w")
+		if err != nil {
+			if isNotFound(err, securityNotFoundExit) {
+				return "", false, nil
+			}
+			return "", false, wrap("get", err)
+		}
+		return strings.TrimRight(string(out), "\r\n"), true, nil
+	case "linux":
+		out, err := k.exec(nil, "secret-tool", "lookup", "service", service, "account", account)
+		if err != nil {
+			if isNotFound(err, secretToolNotFoundExit) {
+				return "", false, nil
+			}
+			return "", false, wrap("get", err)
+		}
+		value := strings.TrimRight(string(out), "\r\n")
+		if value == "" {
+			return "", false, nil
+		}
+		return value, true, nil
+	default:
+		return "", false, ErrUnsupported
+	}
+}
+
+// Delete removes the entry under (service, account), reporting whether one
+// existed.
+func (k *Keyring) Delete(service, account string) (bool, error) {
+	if err := validate(service, account); err != nil {
+		return false, err
+	}
+	switch k.goos {
+	case "darwin":
+		_, err := k.exec(nil, "security", "delete-generic-password", "-s", service, "-a", account)
+		if err != nil {
+			if isNotFound(err, securityNotFoundExit) {
+				return false, nil
+			}
+			return false, wrap("delete", err)
+		}
+		return true, nil
+	case "linux":
+		// `secret-tool clear` always exits 0, so probe existence first.
+		_, existed, err := k.Get(service, account)
+		if err != nil {
+			return false, err
+		}
+		if _, err := k.exec(nil, "secret-tool", "clear", "service", service, "account", account); err != nil {
+			return false, wrap("delete", err)
+		}
+		return existed, nil
+	default:
+		return false, ErrUnsupported
+	}
+}
+
+func (k *Keyring) exec(stdin []byte, name string, args ...string) ([]byte, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), commandTimeout)
+	defer cancel()
+	return k.run(ctx, name, stdin, args...)
+}
+
+func execRunner(ctx context.Context, name string, stdin []byte, args ...string) ([]byte, error) {
+	cmd := exec.CommandContext(ctx, name, args...)
+	if len(stdin) > 0 {
+		cmd.Stdin = bytes.NewReader(stdin)
+	}
+	var out, errBuf bytes.Buffer
+	cmd.Stdout = &out
+	cmd.Stderr = &errBuf
+	if err := cmd.Run(); err != nil {
+		return out.Bytes(), &runError{err: err, stderr: strings.TrimSpace(errBuf.String())}
+	}
+	return out.Bytes(), nil
+}
+
+// runError carries a tool failure with its stderr and preserves the underlying
+// error for errors.As (so exit-code / not-found detection still works).
+type runError struct {
+	err    error
+	stderr string
+}
+
+func (e *runError) Error() string {
+	if e.stderr != "" {
+		return e.stderr
+	}
+	return e.err.Error()
+}
+
+func (e *runError) Unwrap() error { return e.err }
+
+// Not-found exit codes for the OS tools: macOS `security` exits 44
+// (errSecItemNotFound) when no matching item exists; `secret-tool` exits 1 when a
+// lookup finds nothing. Any other non-zero exit is a real failure.
+const (
+	securityNotFoundExit   = 44
+	secretToolNotFoundExit = 1
+)
+
+// isNotFound reports whether err is a tool exit whose code is one of the given
+// "no such entry" codes (as opposed to a missing binary or a genuine failure,
+// which must not be masked). It matches on the ExitCode behavior (satisfied by
+// *exec.ExitError) so the logic is testable without spawning a real process.
+func isNotFound(err error, codes ...int) bool {
+	var coder interface{ ExitCode() int }
+	if !errors.As(err, &coder) {
+		return false
+	}
+	code := coder.ExitCode()
+	for _, c := range codes {
+		if code == c {
+			return true
+		}
+	}
+	return false
+}
+
+// wrap adds operation context to a tool error, leaving nil untouched.
+func wrap(op string, err error) error {
+	if err == nil {
+		return nil
+	}
+	var execErr *exec.Error
+	if errors.As(err, &execErr) {
+		return fmt.Errorf("keyring: %s: %q not found (install the OS keyring tool): %w", op, execErr.Name, err)
+	}
+	return fmt.Errorf("keyring: %s: %w", op, err)
+}
+
+func validate(service, account string) error {
+	if strings.TrimSpace(service) == "" {
+		return errors.New("keyring: service is required")
+	}
+	if strings.TrimSpace(account) == "" {
+		return errors.New("keyring: account is required")
+	}
+	return nil
+}

internal/keyring/keyring_test.go

@@ -0,0 +1,216 @@
+package keyring
+
+import (
+	"context"
+	"os/exec"
+	"strings"
+	"testing"
+)
+
+// fakeExit is a not-found exit error: it satisfies the ExitCode() seam used by
+// isNotFound without spawning a real process.
+type fakeExit struct{ code int }
+
+func (e fakeExit) Error() string { return "exit status" }
+func (e fakeExit) ExitCode() int { return e.code }
+
+// fakeKeyring is an in-memory simulation of the OS tools driven through the
+// runner seam. It records the last stdin so tests can assert the secret never
+// travels via argv on Linux.
+type fakeKeyring struct {
+	goos      string
+	data      map[string]string
+	lastStdin string
+	lastArgs  []string
+}
+
+func newFake(goos string) *fakeKeyring {
+	return &fakeKeyring{goos: goos, data: map[string]string{}}
+}
+
+func (f *fakeKeyring) keyring() *Keyring { return &Keyring{run: f.run, goos: f.goos} }
+
+func flagValue(args []string, flag string) string {
+	for i := 0; i < len(args)-1; i++ {
+		if args[i] == flag {
+			return args[i+1]
+		}
+	}
+	return ""
+}
+
+func attrValue(args []string, attr string) string {
+	for i := 0; i < len(args)-1; i++ {
+		if args[i] == attr {
+			return args[i+1]
+		}
+	}
+	return ""
+}
+
+func key(service, account string) string { return service + "\x00" + account }
+
+func (f *fakeKeyring) run(_ context.Context, name string, stdin []byte, args ...string) ([]byte, error) {
+	f.lastStdin = string(stdin)
+	f.lastArgs = append([]string{name}, args...)
+	if len(args) == 0 {
+		return nil, fakeExit{1}
+	}
+	switch f.goos {
+	case "darwin":
+		svc, acct := flagValue(args, "-s"), flagValue(args, "-a")
+		switch args[0] {
+		case "add-generic-password":
+			f.data[key(svc, acct)] = flagValue(args, "-w")
+			return nil, nil
+		case "find-generic-password":
+			if v, ok := f.data[key(svc, acct)]; ok {
+				return []byte(v + "\n"), nil // security prints a trailing newline
+			}
+			return nil, fakeExit{44}
+		case "delete-generic-password":
+			if _, ok := f.data[key(svc, acct)]; ok {
+				delete(f.data, key(svc, acct))
+				return nil, nil
+			}
+			return nil, fakeExit{44}
+		}
+	case "linux":
+		svc, acct := attrValue(args, "service"), attrValue(args, "account")
+		switch args[0] {
+		case "store":
+			f.data[key(svc, acct)] = string(stdin)
+			return nil, nil
+		case "lookup":
+			if v, ok := f.data[key(svc, acct)]; ok {
+				return []byte(v), nil // secret-tool prints no trailing newline
+			}
+			return nil, fakeExit{1}
+		case "clear":
+			delete(f.data, key(svc, acct))
+			return nil, nil
+		}
+	}
+	return nil, fakeExit{1}
+}
+
+func TestKeyringGetSurfacesNonNotFoundError(t *testing.T) {
+	// On macOS only exit 44 (errSecItemNotFound) means "no entry"; any other
+	// non-zero exit is a real failure that must surface, not be masked as absent.
+	k := &Keyring{
+		goos: "darwin",
+		run: func(_ context.Context, _ string, _ []byte, _ ...string) ([]byte, error) {
+			return nil, fakeExit{1}
+		},
+	}
+	if _, ok, err := k.Get("zero", "tokens"); err == nil || ok {
+		t.Fatalf("a non-44 exit must surface as an error, got ok=%v err=%v", ok, err)
+	}
+}
+
+func TestKeyringRoundTripDarwin(t *testing.T) {
+	k := newFake("darwin").keyring()
+	if err := k.Set("zero", "tokens", "blob-AAA"); err != nil {
+		t.Fatalf("Set: %v", err)
+	}
+	got, ok, err := k.Get("zero", "tokens")
+	if err != nil || !ok {
+		t.Fatalf("Get: ok=%v err=%v", ok, err)
+	}
+	if got != "blob-AAA" {
+		t.Fatalf("Get = %q, want blob-AAA", got)
+	}
+	existed, err := k.Delete("zero", "tokens")
+	if err != nil || !existed {
+		t.Fatalf("Delete: existed=%v err=%v", existed, err)
+	}
+	if _, ok, _ := k.Get("zero", "tokens"); ok {
+		t.Fatal("token should be gone after delete")
+	}
+}
+
+func TestKeyringRoundTripLinuxUsesStdin(t *testing.T) {
+	f := newFake("linux")
+	k := f.keyring()
+	if err := k.Set("zero", "tokens", "blob-BBB"); err != nil {
+		t.Fatalf("Set: %v", err)
+	}
+	// The secret must travel via stdin, never the argument vector.
+	if f.lastStdin != "blob-BBB" {
+		t.Fatalf("secret not sent via stdin: stdin=%q", f.lastStdin)
+	}
+	for _, a := range f.lastArgs {
+		if strings.Contains(a, "blob-BBB") {
+			t.Fatalf("secret leaked into argv: %v", f.lastArgs)
+		}
+	}
+	got, ok, err := k.Get("zero", "tokens")
+	if err != nil || !ok || got != "blob-BBB" {
+		t.Fatalf("Get = %q ok=%v err=%v", got, ok, err)
+	}
+	existed, err := k.Delete("zero", "tokens")
+	if err != nil || !existed {
+		t.Fatalf("Delete: existed=%v err=%v", existed, err)
+	}
+}
+
+func TestKeyringGetMissingIsNotError(t *testing.T) {
+	for _, goos := range []string{"darwin", "linux"} {
+		k := newFake(goos).keyring()
+		if _, ok, err := k.Get("zero", "absent"); err != nil || ok {
+			t.Fatalf("[%s] Get(absent) = ok=%v err=%v, want false/nil", goos, ok, err)
+		}
+		if existed, err := k.Delete("zero", "absent"); err != nil || existed {
+			t.Fatalf("[%s] Delete(absent) = existed=%v err=%v, want false/nil", goos, existed, err)
+		}
+	}
+}
+
+func TestKeyringUnsupportedPlatform(t *testing.T) {
+	k := &Keyring{run: newFake("windows").run, goos: "windows"}
+	if k.Available() {
+		t.Fatal("windows should report unavailable")
+	}
+	if err := k.Set("zero", "tokens", "x"); err == nil {
+		t.Fatal("Set on unsupported platform should error")
+	}
+	if _, _, err := k.Get("zero", "tokens"); err == nil {
+		t.Fatal("Get on unsupported platform should error")
+	}
+	if _, err := k.Delete("zero", "tokens"); err == nil {
+		t.Fatal("Delete on unsupported platform should error")
+	}
+}
+
+func TestKeyringValidation(t *testing.T) {
+	k := newFake("darwin").keyring()
+	if err := k.Set("", "a", "s"); err == nil {
+		t.Fatal("empty service should error")
+	}
+	if err := k.Set("svc", "", "s"); err == nil {
+		t.Fatal("empty account should error")
+	}
+}
+
+func TestKeyringMissingBinaryError(t *testing.T) {
+	// A missing tool surfaces as a wrapped, descriptive error (not not-found).
+	k := &Keyring{goos: "linux", run: func(context.Context, string, []byte, ...string) ([]byte, error) {
+		return nil, &exec.Error{Name: "secret-tool", Err: exec.ErrNotFound}
+	}}
+	if err := k.Set("zero", "tokens", "x"); err == nil || !strings.Contains(err.Error(), "secret-tool") {
+		t.Fatalf("missing-binary Set error = %v, want mention of secret-tool", err)
+	}
+	// A missing binary on Get must not be misread as not-found.
+	if _, ok, err := k.Get("zero", "tokens"); err == nil || ok {
+		t.Fatalf("missing-binary Get = ok=%v err=%v, want error", ok, err)
+	}
+}
+
+func TestAvailable(t *testing.T) {
+	if !(newFake("darwin").keyring().Available()) {
+		t.Fatal("darwin should be available")
+	}
+	if !(newFake("linux").keyring().Available()) {
+		t.Fatal("linux should be available")
+	}
+}

internal/mcp/oauth.go

@@ -2,9 +2,6 @@ package mcp
 
 import (
 	"context"
-	"crypto/rand"
-	"crypto/sha256"
-	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -14,20 +11,56 @@ import (
 	"net/url"
 	"strings"
 	"time"
+
+	"github.com/Gitlawb/zero/internal/oauth"
 )
 
 // ServerAuthOAuth is the value of an MCP server's auth field that selects the
 // OAuth 2.0 + PKCE authorization-code flow.
 const ServerAuthOAuth = "oauth"
 
-const (
-	wellKnownAuthServerPath = "/.well-known/oauth-authorization-server"
-	defaultLoginTimeout     = 3 * time.Minute
-	// pkceVerifierBytes yields a 43-character base64url verifier, the minimum
-	// length permitted by the PKCE spec while remaining high-entropy.
-	pkceVerifierBytes = 32
-	stateBytes        = 32
-)
+const defaultLoginTimeout = 3 * time.Minute
+
+// MCP OAuth delegates its transport/identity-agnostic engine to internal/oauth
+// (PKCE, RFC 8414 discovery, authorize-URL build, token exchange/refresh) so the
+// two share one implementation. MCP keeps its own LoginOptions/Login
+// orchestration, OAuthConfig/StoredToken types, loopback handling, CLI, and
+// on-disk token format — all behavior-preserving. The shared engine also adds an
+// https-only token-endpoint guard (loopback exempt), a hardening MCP inherits.
+
+// pkceToParams converts the shared PKCE pair to MCP's local type.
+func pkceToParams(p oauth.PKCE) pkceParams {
+	return pkceParams{Verifier: p.Verifier, Challenge: p.Challenge, Method: p.Method}
+}
+
+// pkceToOAuth converts MCP's local PKCE type back to the shared type.
+func pkceToOAuth(p pkceParams) oauth.PKCE {
+	return oauth.PKCE{Verifier: p.Verifier, Challenge: p.Challenge, Method: p.Method}
+}
+
+// configFor builds the shared oauth.Config from MCP's OAuthConfig + resolved
+// endpoints for a flow.
+func configFor(cfg OAuthConfig, metadata authServerMetadata) oauth.Config {
+	return oauth.Config{
+		ClientID:              cfg.ClientID,
+		ClientSecret:          cfg.ClientSecret,
+		Scopes:                cfg.Scopes,
+		AuthorizationEndpoint: metadata.AuthorizationEndpoint,
+		TokenEndpoint:         metadata.TokenEndpoint,
+	}
+}
+
+// tokenToStored converts a shared oauth.Token to MCP's StoredToken (MCP does not
+// use the Account field).
+func tokenToStored(t oauth.Token) StoredToken {
+	return StoredToken{
+		AccessToken:  t.AccessToken,
+		RefreshToken: t.RefreshToken,
+		TokenType:    t.TokenType,
+		Scopes:       t.Scopes,
+		ExpiresAt:    t.ExpiresAt,
+	}
+}
 
 // OAuthConfig describes how to authenticate to a remote MCP server using OAuth.
 // Endpoints may be discovered from the server's metadata document; explicit
@@ -84,34 +117,20 @@ type authorizationFlow struct {
 	now        func() time.Time
 }
 
-// discoverAuthorizationServer fetches the OAuth 2.0 authorization server
-// metadata document published at the well-known path under the given base URL.
+// discoverAuthorizationServer fetches the RFC 8414 authorization server metadata
+// at the well-known path under baseURL, via the shared engine.
 func discoverAuthorizationServer(ctx context.Context, client *http.Client, baseURL string) (authServerMetadata, error) {
-	if client == nil {
-		client = http.DefaultClient
-	}
-	metadataURL, err := joinWellKnown(baseURL)
+	meta, err := oauth.DiscoverAuthorizationServer(ctx, client, baseURL)
 	if err != nil {
 		return authServerMetadata{}, err
 	}
-	request, err := http.NewRequestWithContext(ctx, http.MethodGet, metadataURL, nil)
-	if err != nil {
-		return authServerMetadata{}, err
-	}
-	request.Header.Set("Accept", "application/json")
-	response, err := client.Do(request)
-	if err != nil {
-		return authServerMetadata{}, fmt.Errorf("fetch authorization server metadata: %w", err)
-	}
-	defer response.Body.Close()
-	if response.StatusCode < http.StatusOK || response.StatusCode >= http.StatusMultipleChoices {
-		return authServerMetadata{}, fmt.Errorf("authorization server metadata returned HTTP %d", response.StatusCode)
-	}
-	var metadata authServerMetadata
-	if err := json.NewDecoder(io.LimitReader(response.Body, 1<<20)).Decode(&metadata); err != nil {
-		return authServerMetadata{}, fmt.Errorf("decode authorization server metadata: %w", err)
-	}
-	return metadata, nil
+	return authServerMetadata{
+		Issuer:                meta.Issuer,
+		AuthorizationEndpoint: meta.AuthorizationEndpoint,
+		TokenEndpoint:         meta.TokenEndpoint,
+		RegistrationEndpoint:  meta.RegistrationEndpoint,
+		ScopesSupported:       meta.ScopesSupported,
+	}, nil
 }
 
 // resolveAuthorizationServer discovers metadata and applies explicit config
@@ -149,44 +168,23 @@ func resolveAuthorizationServer(ctx context.Context, client *http.Client, baseUR
 	return metadata, nil
 }
 
-// newPKCE generates a high-entropy code verifier and its S256 challenge.
+// newPKCE generates a high-entropy code verifier and its S256 challenge via the
+// shared engine.
 func newPKCE() (pkceParams, error) {
-	verifierRaw := make([]byte, pkceVerifierBytes)
-	if _, err := rand.Read(verifierRaw); err != nil {
-		return pkceParams{}, fmt.Errorf("generate PKCE verifier: %w", err)
+	p, err := oauth.NewPKCE()
+	if err != nil {
+		return pkceParams{}, err
 	}
-	verifier := base64.RawURLEncoding.EncodeToString(verifierRaw)
-	sum := sha256.Sum256([]byte(verifier))
-	challenge := base64.RawURLEncoding.EncodeToString(sum[:])
-	return pkceParams{Verifier: verifier, Challenge: challenge, Method: "S256"}, nil
+	return pkceToParams(p), nil
 }
 
 func newState() (string, error) {
-	raw := make([]byte, stateBytes)
-	if _, err := rand.Read(raw); err != nil {
-		return "", fmt.Errorf("generate state: %w", err)
-	}
-	return base64.RawURLEncoding.EncodeToString(raw), nil
+	return oauth.NewState()
 }
 
-// authorizationURL builds the authorization request URL.
+// authorizationURL builds the authorization request URL via the shared engine.
 func (flow *authorizationFlow) authorizationURL(redirectURI string) (string, error) {
-	parsed, err := url.Parse(flow.metadata.AuthorizationEndpoint)
-	if err != nil {
-		return "", fmt.Errorf("parse authorization endpoint: %w", err)
-	}
-	query := parsed.Query()
-	query.Set("response_type", "code")
-	query.Set("client_id", flow.config.ClientID)
-	query.Set("redirect_uri", redirectURI)
-	query.Set("state", flow.state)
-	query.Set("code_challenge", flow.pkce.Challenge)
-	query.Set("code_challenge_method", flow.pkce.Method)
-	if len(flow.config.Scopes) > 0 {
-		query.Set("scope", strings.Join(flow.config.Scopes, " "))
-	}
-	parsed.RawQuery = query.Encode()
-	return parsed.String(), nil
+	return oauth.BuildAuthorizationURL(configFor(flow.config, flow.metadata), pkceToOAuth(flow.pkce), flow.state, redirectURI, nil)
 }
 
 // parseCallback validates the redirect query and returns the authorization
@@ -209,117 +207,30 @@ func (flow *authorizationFlow) parseCallback(values url.Values) (string, error)
 	return code, nil
 }
 
-// exchangeCode swaps an authorization code + PKCE verifier for tokens.
+// exchangeCode swaps an authorization code + PKCE verifier for tokens via the
+// shared engine.
 func (flow *authorizationFlow) exchangeCode(ctx context.Context, code string, redirectURI string) (StoredToken, error) {
-	form := url.Values{}
-	form.Set("grant_type", "authorization_code")
-	form.Set("code", code)
-	form.Set("redirect_uri", redirectURI)
-	form.Set("client_id", flow.config.ClientID)
-	form.Set("code_verifier", flow.pkce.Verifier)
-	if secret := strings.TrimSpace(flow.config.ClientSecret); secret != "" {
-		form.Set("client_secret", secret)
+	token, err := oauth.ExchangeCode(ctx, flow.httpClient, configFor(flow.config, flow.metadata), code, flow.pkce.Verifier, redirectURI, flow.now)
+	if err != nil {
+		return StoredToken{}, err
 	}
-	return postTokenRequest(ctx, flow.httpClient, flow.metadata.TokenEndpoint, form, StoredToken{Scopes: flow.config.Scopes}, flow.now)
+	return tokenToStored(token), nil
 }
 
-// refreshAccessToken exchanges a refresh token for a fresh access token. A
-// response that omits a new refresh token preserves the previous one.
+// refreshAccessToken exchanges a refresh token for a fresh access token via the
+// shared engine. A response that omits a new refresh token preserves the
+// previous one.
 func refreshAccessToken(ctx context.Context, client *http.Client, cfg OAuthConfig, current StoredToken, now func() time.Time) (StoredToken, error) {
-	refresh := strings.TrimSpace(current.RefreshToken)
-	if refresh == "" {
-		return StoredToken{}, errors.New("no refresh token available")
-	}
-	tokenEndpoint := strings.TrimSpace(cfg.TokenEndpoint)
-	if tokenEndpoint == "" {
-		return StoredToken{}, errors.New("no token endpoint configured for refresh")
-	}
-	form := url.Values{}
-	form.Set("grant_type", "refresh_token")
-	form.Set("refresh_token", refresh)
-	form.Set("client_id", cfg.ClientID)
-	if secret := strings.TrimSpace(cfg.ClientSecret); secret != "" {
-		form.Set("client_secret", secret)
-	}
-	if len(cfg.Scopes) > 0 {
-		form.Set("scope", strings.Join(cfg.Scopes, " "))
-	}
-	refreshed, err := postTokenRequest(ctx, client, tokenEndpoint, form, StoredToken{Scopes: current.Scopes, RefreshToken: refresh}, now)
+	token, err := oauth.Refresh(ctx, client, oauth.Config{
+		ClientID:      cfg.ClientID,
+		ClientSecret:  cfg.ClientSecret,
+		Scopes:        cfg.Scopes,
+		TokenEndpoint: cfg.TokenEndpoint,
+	}, oauth.Token{AccessToken: current.AccessToken, RefreshToken: current.RefreshToken, TokenType: current.TokenType, Scopes: current.Scopes, ExpiresAt: current.ExpiresAt}, now)
 	if err != nil {
 		return StoredToken{}, err
 	}
-	return refreshed, nil
-}
-
-// tokenResponse is the JSON returned by the token endpoint.
-type tokenResponse struct {
-	AccessToken      string `json:"access_token"`
-	RefreshToken     string `json:"refresh_token"`
-	TokenType        string `json:"token_type"`
-	ExpiresIn        int64  `json:"expires_in"`
-	Scope            string `json:"scope"`
-	Error            string `json:"error"`
-	ErrorDescription string `json:"error_description"`
-}
-
-// postTokenRequest performs a token endpoint POST and maps the response onto a
-// StoredToken. The base token supplies values to preserve (e.g. an existing
-// refresh token or scope set) when the response omits them.
-func postTokenRequest(ctx context.Context, client *http.Client, tokenEndpoint string, form url.Values, base StoredToken, now func() time.Time) (StoredToken, error) {
-	if client == nil {
-		client = http.DefaultClient
-	}
-	if now == nil {
-		now = time.Now
-	}
-	request, err := http.NewRequestWithContext(ctx, http.MethodPost, tokenEndpoint, strings.NewReader(form.Encode()))
-	if err != nil {
-		return StoredToken{}, err
-	}
-	request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
-	request.Header.Set("Accept", "application/json")
-
-	response, err := client.Do(request)
-	if err != nil {
-		return StoredToken{}, fmt.Errorf("token request failed: %w", err)
-	}
-	defer response.Body.Close()
-
-	body, _ := io.ReadAll(io.LimitReader(response.Body, 1<<20))
-	var parsed tokenResponse
-	if len(body) > 0 {
-		// A malformed body on an error status is reported as a status error below.
-		_ = json.Unmarshal(body, &parsed)
-	}
-
-	if response.StatusCode < http.StatusOK || response.StatusCode >= http.StatusMultipleChoices {
-		if parsed.Error != "" {
-			if parsed.ErrorDescription != "" {
-				return StoredToken{}, fmt.Errorf("token endpoint error %q: %s", parsed.Error, parsed.ErrorDescription)
-			}
-			return StoredToken{}, fmt.Errorf("token endpoint error %q", parsed.Error)
-		}
-		return StoredToken{}, fmt.Errorf("token endpoint returned HTTP %d", response.StatusCode)
-	}
-	if strings.TrimSpace(parsed.AccessToken) == "" {
-		return StoredToken{}, errors.New("token endpoint returned no access token")
-	}
-
-	token := base
-	token.AccessToken = parsed.AccessToken
-	if strings.TrimSpace(parsed.RefreshToken) != "" {
-		token.RefreshToken = parsed.RefreshToken
-	}
-	if strings.TrimSpace(parsed.TokenType) != "" {
-		token.TokenType = parsed.TokenType
-	}
-	if parsed.ExpiresIn > 0 {
-		token.ExpiresAt = now().Add(time.Duration(parsed.ExpiresIn) * time.Second).UTC()
-	}
-	if scope := strings.TrimSpace(parsed.Scope); scope != "" {
-		token.Scopes = strings.Fields(scope)
-	}
-	return token, nil
+	return tokenToStored(token), nil
 }
 
 // registerClient performs dynamic client registration against the registration
@@ -505,22 +416,3 @@ func Login(ctx context.Context, options LoginOptions) (StoredToken, error) {
 		return StoredToken{}, fmt.Errorf("timed out waiting for OAuth authorization callback: %w", loginCtx.Err())
 	}
 }
-
-func joinWellKnown(baseURL string) (string, error) {
-	parsed, err := url.Parse(strings.TrimSpace(baseURL))
-	if err != nil || parsed.Host == "" {
-		return "", fmt.Errorf("invalid base URL for metadata discovery: %q", baseURL)
-	}
-	// RFC 8414: the well-known segment is inserted between the host and any issuer
-	// path component, so a path-based issuer (https://host/tenant-a) is probed at
-	// https://host/.well-known/oauth-authorization-server/tenant-a — not at the
-	// host root (which would break tenant-scoped discovery).
-	issuerPath := strings.Trim(parsed.Path, "/")
-	parsed.Path = wellKnownAuthServerPath
-	if issuerPath != "" {
-		parsed.Path = strings.TrimRight(wellKnownAuthServerPath, "/") + "/" + issuerPath
-	}
-	parsed.RawQuery = ""
-	parsed.Fragment = ""
-	return parsed.String(), nil
-}

internal/mcp/oauth_store.go

@@ -6,17 +6,15 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
-	"sort"
 	"strings"
-	"sync"
 	"time"
+
+	"github.com/Gitlawb/zero/internal/oauth"
 )
 
-const (
-	tokenStoreSchemaVersion = 1
-	tokenStoreLockTimeout   = 5 * time.Second
-	tokenStoreLockRetry     = 10 * time.Millisecond
-)
+// tokenStoreSchemaVersion is the schema of the legacy mcp-oauth-tokens.json file,
+// retained so migration can recognize a file it understands.
+const tokenStoreSchemaVersion = 1
 
 // StoredToken holds the credentials issued by an OAuth 2.0 authorization server
 // for a single MCP server. The token fields are sensitive: they are tagged so
@@ -42,29 +40,37 @@ type TokenStatus struct {
 	Expired         bool      `json:"expired"`
 }
 
-// TokenStoreOptions configures where OAuth tokens are persisted. When FilePath
-// is empty the path is resolved under the user config dir, mirroring how MCP
-// permissions are stored.
+// TokenStoreOptions configures the unified token store backing MCP OAuth tokens.
+// FilePath overrides the store path (default: the shared oauth store path).
+// LegacyPath overrides the pre-unification file migrated on construction; when
+// empty it defaults to the conventional mcp-oauth-tokens.json only for the
+// default (FilePath-unset) store, so an explicit FilePath never triggers an
+// unexpected migration from the real user config.
 type TokenStoreOptions struct {
-	FilePath string
-	Env      map[string]string
-	Now      func() time.Time
+	FilePath   string
+	LegacyPath string
+	Env        map[string]string
+	Now        func() time.Time
 }
 
-// TokenStore persists OAuth tokens per MCP server in a 0600 JSON file.
+// TokenStore persists MCP OAuth tokens in the unified oauth store
+// (internal/oauth) under the "mcp:" namespace, sharing one file with provider
+// logins. On construction it transparently and non-destructively migrates a
+// legacy mcp-oauth-tokens.json into the unified store.
 type TokenStore struct {
-	filePath string
-	now      func() time.Time
-	mu       sync.Mutex
+	store *oauth.Store
 }
 
+// tokenFile is the legacy on-disk format, retained only to read a
+// pre-unification mcp-oauth-tokens.json during migration.
 type tokenFile struct {
 	SchemaVersion int                    `json:"schemaVersion"`
 	Tokens        map[string]StoredToken `json:"tokens"`
 }
 
-// ResolveTokenStorePath determines the on-disk location for OAuth tokens,
-// honoring an explicit override, XDG_CONFIG_HOME, then the user home dir.
+// ResolveTokenStorePath determines the on-disk location of the LEGACY OAuth token
+// file, honoring an explicit override, XDG_CONFIG_HOME, then the user home dir.
+// It is used to locate a pre-unification file for migration.
 func ResolveTokenStorePath(env map[string]string) (string, error) {
 	override := strings.TrimSpace(envValue(env, "ZERO_MCP_OAUTH_TOKENS_PATH"))
 	if override != "" {
@@ -95,215 +101,168 @@ func ResolveTokenStorePath(env map[string]string) (string, error) {
 	return filepath.Join(configHome, "zero", "mcp-oauth-tokens.json"), nil
 }
 
-// NewTokenStore builds a file-backed token store.
+// NewTokenStore builds the unified-store-backed token store and runs a one-time
+// migration from a legacy file when applicable.
 func NewTokenStore(options TokenStoreOptions) (*TokenStore, error) {
-	filePath := options.FilePath
-	var err error
-	if strings.TrimSpace(filePath) == "" {
-		filePath, err = ResolveTokenStorePath(options.Env)
-		if err != nil {
-			return nil, err
-		}
-	}
-	if !filepath.IsAbs(filePath) {
-		filePath, err = filepath.Abs(filePath)
-		if err != nil {
-			return nil, err
-		}
-	}
 	now := options.Now
 	if now == nil {
 		now = time.Now
 	}
-	return &TokenStore{filePath: filepath.Clean(filePath), now: now}, nil
+	unified, err := oauth.NewStore(oauth.StoreOptions{
+		FilePath: options.FilePath,
+		Env:      options.Env,
+		Now:      now,
+	})
+	if err != nil {
+		return nil, err
+	}
+	store := &TokenStore{store: unified}
+
+	legacyPath := strings.TrimSpace(options.LegacyPath)
+	if legacyPath == "" && strings.TrimSpace(options.FilePath) == "" {
+		// Default (production) construction: migrate from the conventional path.
+		legacyPath, err = ResolveTokenStorePath(options.Env)
+		if err != nil {
+			return nil, err
+		}
+	}
+	if legacyPath != "" {
+		if err := store.migrateLegacy(legacyPath); err != nil {
+			return nil, err
+		}
+	}
+	return store, nil
 }
 
-// FilePath returns the resolved token store path.
+// FilePath returns the resolved unified store path.
 func (store *TokenStore) FilePath() string {
-	return store.filePath
+	return store.store.FilePath()
 }
 
 // Save persists the token for a server, replacing any existing entry.
 func (store *TokenStore) Save(serverName string, token StoredToken) error {
-	if err := ValidateServerName(serverName); err != nil {
-		return err
-	}
-	store.mu.Lock()
-	defer store.mu.Unlock()
-	unlock, err := store.lockStateFile()
+	key, err := mcpKey(serverName)
 	if err != nil {
 		return err
 	}
-	defer unlock()
-
-	state, err := store.readState()
-	if err != nil {
-		return err
-	}
-	state.Tokens[serverName] = token
-	return store.writeState(state)
+	return store.store.Save(key, storedToOAuth(token))
 }
 
 // Load returns the stored token for a server. The second return value is false
 // when no token has been stored for the server.
 func (store *TokenStore) Load(serverName string) (StoredToken, bool, error) {
-	if err := ValidateServerName(serverName); err != nil {
-		return StoredToken{}, false, err
-	}
-	store.mu.Lock()
-	defer store.mu.Unlock()
-
-	state, err := store.readState()
+	key, err := mcpKey(serverName)
 	if err != nil {
 		return StoredToken{}, false, err
 	}
-	token, ok := state.Tokens[serverName]
-	return token, ok, nil
+	token, ok, err := store.store.Load(key)
+	if err != nil || !ok {
+		return StoredToken{}, ok, err
+	}
+	return tokenToStored(token), true, nil
 }
 
 // Delete removes the stored token for a server. It reports whether an entry was
 // present before deletion.
 func (store *TokenStore) Delete(serverName string) (bool, error) {
-	if err := ValidateServerName(serverName); err != nil {
-		return false, err
-	}
-	store.mu.Lock()
-	defer store.mu.Unlock()
-	unlock, err := store.lockStateFile()
+	key, err := mcpKey(serverName)
 	if err != nil {
 		return false, err
 	}
-	defer unlock()
-
-	state, err := store.readState()
-	if err != nil {
-		return false, err
-	}
-	if _, ok := state.Tokens[serverName]; !ok {
-		return false, nil
-	}
-	delete(state.Tokens, serverName)
-	if err := store.writeState(state); err != nil {
-		return false, err
-	}
-	return true, nil
+	return store.store.Delete(key)
 }
 
-// Status returns a redaction-safe summary of every stored token, sorted by
+// Status returns a redaction-safe summary of every stored MCP token, sorted by
 // server name. It never includes the token material.
 func (store *TokenStore) Status() ([]TokenStatus, error) {
-	store.mu.Lock()
-	defer store.mu.Unlock()
-
-	state, err := store.readState()
+	statuses, err := store.store.Status(oauth.KeyPrefixMCP)
 	if err != nil {
 		return nil, err
 	}
-	names := make([]string, 0, len(state.Tokens))
-	for name := range state.Tokens {
-		names = append(names, name)
+	out := make([]TokenStatus, 0, len(statuses))
+	for _, s := range statuses {
+		out = append(out, TokenStatus{
+			ServerName:      strings.TrimPrefix(s.Key, oauth.KeyPrefixMCP),
+			HasToken:        s.HasToken,
+			HasRefreshToken: s.HasRefreshToken,
+			TokenType:       s.TokenType,
+			Scopes:          s.Scopes,
+			ExpiresAt:       s.ExpiresAt,
+			Expired:         s.Expired,
+		})
 	}
-	sort.Strings(names)
-
-	now := store.now()
-	statuses := make([]TokenStatus, 0, len(names))
-	for _, name := range names {
-		token := state.Tokens[name]
-		status := TokenStatus{
-			ServerName:      name,
-			HasToken:        strings.TrimSpace(token.AccessToken) != "",
-			HasRefreshToken: strings.TrimSpace(token.RefreshToken) != "",
-			TokenType:       token.TokenType,
-			Scopes:          token.Scopes,
-			ExpiresAt:       token.ExpiresAt,
-		}
-		if !token.ExpiresAt.IsZero() && !token.ExpiresAt.After(now) {
-			status.Expired = true
-		}
-		statuses = append(statuses, status)
-	}
-	return statuses, nil
+	return out, nil
 }
 
-func (store *TokenStore) readState() (tokenFile, error) {
-	data, err := os.ReadFile(store.filePath)
+// migrateLegacy imports tokens from a legacy mcp-oauth-tokens.json into the
+// unified store (under "mcp:" keys), then renames the legacy file to a
+// ".migrated" backup. It is non-destructive and idempotent: a newer unified
+// entry is never overwritten, a missing/unreadable/foreign-schema legacy file is
+// left untouched, and the rename ensures it is imported at most once.
+func (store *TokenStore) migrateLegacy(legacyPath string) error {
+	legacyPath = filepath.Clean(legacyPath)
+	// FilePath() is an absolute path; resolve a relative LegacyPath so the
+	// same-file guard can't be bypassed by a relative spelling of the same file.
+	if !filepath.IsAbs(legacyPath) {
+		abs, err := filepath.Abs(legacyPath)
+		if err != nil {
+			return err
+		}
+		legacyPath = filepath.Clean(abs)
+	}
+	if legacyPath == store.store.FilePath() {
+		return nil // legacy and unified resolve to the same file; nothing to migrate
+	}
+	data, err := os.ReadFile(legacyPath)
 	if err != nil {
 		if errors.Is(err, os.ErrNotExist) {
-			return emptyTokenFile(), nil
+			return nil
 		}
-		return tokenFile{}, err
-	}
-	var state tokenFile
-	if err := json.Unmarshal(data, &state); err != nil {
-		return tokenFile{}, fmt.Errorf("invalid MCP OAuth token file at %s: %w", store.filePath, err)
-	}
-	if state.SchemaVersion != tokenStoreSchemaVersion {
-		return tokenFile{}, fmt.Errorf("invalid MCP OAuth token file at %s: unsupported schemaVersion", store.filePath)
-	}
-	if state.Tokens == nil {
-		state.Tokens = map[string]StoredToken{}
-	}
-	for serverName := range state.Tokens {
-		if err := ValidateServerName(serverName); err != nil {
-			return tokenFile{}, fmt.Errorf("invalid MCP OAuth token file at %s: %w", store.filePath, err)
-		}
-	}
-	return state, nil
-}
-
-func (store *TokenStore) writeState(state tokenFile) error {
-	if err := os.MkdirAll(filepath.Dir(store.filePath), 0o700); err != nil {
 		return err
 	}
-	data, err := json.MarshalIndent(state, "", "  ")
-	if err != nil {
-		return err
+	var legacy tokenFile
+	if err := json.Unmarshal(data, &legacy); err != nil {
+		return nil // unreadable legacy file: leave it in place, don't block startup
 	}
-	tempPath := fmt.Sprintf("%s.tmp-%d-%d", store.filePath, os.Getpid(), store.now().UnixNano())
-	if err := os.WriteFile(tempPath, append(data, '\n'), 0o600); err != nil {
-		return err
+	if legacy.SchemaVersion != tokenStoreSchemaVersion {
+		return nil // unknown legacy schema: leave it untouched
 	}
-	if err := os.Rename(tempPath, store.filePath); err != nil {
-		_ = os.Remove(tempPath)
-		return err
-	}
-	return nil
-}
-
-func (store *TokenStore) lockStateFile() (func(), error) {
-	lockPath := store.filePath + ".lockfile"
-	if err := os.MkdirAll(filepath.Dir(store.filePath), 0o700); err != nil {
-		return nil, err
-	}
-	file, err := os.OpenFile(lockPath, os.O_CREATE|os.O_RDWR, 0o600)
-	if err != nil {
-		return nil, err
-	}
-	deadline := time.Now().Add(tokenStoreLockTimeout)
-	for {
-		locked, err := tryLockPermissionFile(file)
+	for serverName, token := range legacy.Tokens {
+		key, err := mcpKey(serverName)
 		if err != nil {
-			_ = file.Close()
-			return nil, err
+			continue // a name that cannot form a valid unified key is skipped
 		}
-		if locked {
-			return func() {
-				_ = unlockPermissionFile(file)
-				_ = file.Close()
-			}, nil
+		if _, ok, loadErr := store.store.Load(key); loadErr == nil && ok {
+			continue // a unified entry already exists; never overwrite
 		}
-		if time.Now().After(deadline) {
-			_ = file.Close()
-			return nil, fmt.Errorf("timed out waiting for MCP OAuth token lock at %s", lockPath)
+		if err := store.store.Save(key, storedToOAuth(token)); err != nil {
+			return err
 		}
-		time.Sleep(tokenStoreLockRetry)
 	}
+	return os.Rename(legacyPath, legacyPath+".migrated")
 }
 
-func emptyTokenFile() tokenFile {
-	return tokenFile{
-		SchemaVersion: tokenStoreSchemaVersion,
-		Tokens:        map[string]StoredToken{},
+// mcpKey builds and validates the unified store key for an MCP server token.
+func mcpKey(serverName string) (string, error) {
+	if err := ValidateServerName(serverName); err != nil {
+		return "", err
+	}
+	key := oauth.KeyPrefixMCP + strings.TrimSpace(serverName)
+	if err := oauth.ValidateKey(key); err != nil {
+		return "", err
+	}
+	return key, nil
+}
+
+// storedToOAuth converts an MCP StoredToken to the shared oauth.Token (the
+// inverse of tokenToStored). MCP never sets the oauth Account field.
+func storedToOAuth(s StoredToken) oauth.Token {
+	return oauth.Token{
+		AccessToken:  s.AccessToken,
+		RefreshToken: s.RefreshToken,
+		TokenType:    s.TokenType,
+		Scopes:       s.Scopes,
+		ExpiresAt:    s.ExpiresAt,
 	}
 }
 

internal/mcp/oauth_store_test.go

@@ -158,6 +158,101 @@ func TestTokenStoreStatusReportsPresenceWithoutToken(t *testing.T) {
 	}
 }
 
+func TestTokenStoreMigratesLegacyFile(t *testing.T) {
+	dir := t.TempDir()
+	legacy := filepath.Join(dir, "mcp-oauth-tokens.json")
+	unified := filepath.Join(dir, "oauth-tokens.json")
+	legacyData := `{"schemaVersion":1,"tokens":{"demo":{"access_token":"a","refresh_token":"r","token_type":"Bearer"}}}`
+	if err := os.WriteFile(legacy, []byte(legacyData), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	store, err := NewTokenStore(TokenStoreOptions{FilePath: unified, LegacyPath: legacy})
+	if err != nil {
+		t.Fatalf("NewTokenStore: %v", err)
+	}
+
+	tok, ok, err := store.Load("demo")
+	if err != nil || !ok {
+		t.Fatalf("migrated token not loadable: ok=%v err=%v", ok, err)
+	}
+	if tok.AccessToken != "a" || tok.RefreshToken != "r" {
+		t.Fatalf("migrated token = %#v", tok)
+	}
+
+	// The unified file keys the token under the mcp: namespace.
+	raw, err := os.ReadFile(unified)
+	if err != nil {
+		t.Fatalf("read unified: %v", err)
+	}
+	if !contains(string(raw), "mcp:demo") {
+		t.Fatalf("unified file should key under mcp: namespace:\n%s", raw)
+	}
+
+	// The legacy file is renamed to a .migrated backup (non-destructive, one-time).
+	if _, err := os.Stat(legacy); !os.IsNotExist(err) {
+		t.Fatalf("legacy file should be renamed away; stat err = %v", err)
+	}
+	if _, err := os.Stat(legacy + ".migrated"); err != nil {
+		t.Fatalf("legacy backup missing: %v", err)
+	}
+
+	// Idempotent: a second construction (legacy now absent) keeps the token.
+	store2, err := NewTokenStore(TokenStoreOptions{FilePath: unified, LegacyPath: legacy})
+	if err != nil {
+		t.Fatalf("NewTokenStore#2: %v", err)
+	}
+	if _, ok, _ := store2.Load("demo"); !ok {
+		t.Fatal("token lost after second construction")
+	}
+}
+
+func TestTokenStoreMigrationPreservesNewerUnified(t *testing.T) {
+	dir := t.TempDir()
+	legacy := filepath.Join(dir, "mcp-oauth-tokens.json")
+	unified := filepath.Join(dir, "oauth-tokens.json")
+	if err := os.WriteFile(legacy, []byte(`{"schemaVersion":1,"tokens":{"demo":{"access_token":"OLD"}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	// Pre-seed the unified store with a newer token (no migration: FilePath set, no LegacyPath).
+	pre, err := NewTokenStore(TokenStoreOptions{FilePath: unified})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := pre.Save("demo", StoredToken{AccessToken: "NEW"}); err != nil {
+		t.Fatal(err)
+	}
+	// Migrating must not overwrite the newer unified entry.
+	store, err := NewTokenStore(TokenStoreOptions{FilePath: unified, LegacyPath: legacy})
+	if err != nil {
+		t.Fatal(err)
+	}
+	tok, _, _ := store.Load("demo")
+	if tok.AccessToken != "NEW" {
+		t.Fatalf("migration overwrote a newer token: %q", tok.AccessToken)
+	}
+}
+
+func TestTokenStoreNamespacedFromProvider(t *testing.T) {
+	// An MCP token and a provider login of the same name coexist in one file.
+	dir := t.TempDir()
+	unified := filepath.Join(dir, "oauth-tokens.json")
+	mcpStore, err := NewTokenStore(TokenStoreOptions{FilePath: unified})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := mcpStore.Save("shared", StoredToken{AccessToken: "mcp-token"}); err != nil {
+		t.Fatal(err)
+	}
+	statuses, err := mcpStore.Status()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(statuses) != 1 || statuses[0].ServerName != "shared" {
+		t.Fatalf("status = %#v, want one entry for 'shared'", statuses)
+	}
+}
+
 func TestResolveTokenStorePathUsesXDG(t *testing.T) {
 	// Use a real temp dir so the base is absolute on every OS (a literal
 	// "/tmp/..." isn't absolute on Windows, where ResolveTokenStorePath would

internal/notify/webhook_wire.go

@@ -0,0 +1,40 @@
+package notify
+
+import "strings"
+
+// Webhook delivery is configured entirely from the environment. A webhook URL
+// typically embeds a secret token, so sourcing it from the environment keeps it
+// out of any on-disk config file. The sink is strictly opt-in: with
+// EnvWebhookURL unset the wiring helper attaches nothing and the notifier
+// behaves exactly as before.
+const (
+	// EnvWebhookURL holds the destination webhook/Slack URL. Empty disables it.
+	EnvWebhookURL = "ZERO_NOTIFY_WEBHOOK_URL"
+	// EnvWebhookSummary is an optional one-line run summary attached to every
+	// payload (for example "nightly audit run").
+	EnvWebhookSummary = "ZERO_NOTIFY_WEBHOOK_SUMMARY"
+)
+
+// MaybeAddWebhookSink attaches a webhook sink to n when a webhook URL is present
+// in the environment, and is otherwise a no-op. env resolves an environment
+// variable (pass os.Getenv); logf records one redacted line per failed delivery
+// (pass nil to stay silent — for example a TUI that owns the screen). It is safe
+// to call unconditionally: configuration alone decides whether the sink exists.
+//
+// The attached sink is still subject to the notifier's Mode/focus policy, so a
+// webhook only delivers when notifications are enabled (for example
+// `--notify both`), matching the rest of the notification surface.
+func MaybeAddWebhookSink(n *Notifier, env func(string) string, logf func(format string, args ...any)) {
+	if n == nil || env == nil {
+		return
+	}
+	url := strings.TrimSpace(env(EnvWebhookURL))
+	if url == "" {
+		return
+	}
+	n.AddSink(NewWebhookSink(WebhookConfig{
+		URL:     url,
+		Summary: strings.TrimSpace(env(EnvWebhookSummary)),
+		Logf:    logf,
+	}))
+}

internal/notify/webhook_wire_test.go

@@ -0,0 +1,71 @@
+package notify
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"sync/atomic"
+	"testing"
+)
+
+// envFunc builds a deterministic env resolver from a map for the wiring tests.
+func envFunc(values map[string]string) func(string) string {
+	return func(key string) string { return values[key] }
+}
+
+func TestMaybeAddWebhookSinkAttachesAndDelivers(t *testing.T) {
+	var hits int32
+	var gotSummary string
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		atomic.AddInt32(&hits, 1)
+		var payload webhookPayload
+		_ = json.NewDecoder(io.LimitReader(r.Body, 1<<16)).Decode(&payload)
+		gotSummary = payload.Summary
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer server.Close()
+
+	n := New(&bytes.Buffer{}, Config{Mode: ModeBell, FocusMode: FocusAlways})
+	MaybeAddWebhookSink(n, envFunc(map[string]string{
+		EnvWebhookURL:     server.URL,
+		EnvWebhookSummary: "nightly audit",
+	}), nil)
+
+	if got := len(n.sinks); got != 1 {
+		t.Fatalf("expected 1 sink attached, got %d", got)
+	}
+
+	n.Notify(Completion, "Zero: ready")
+	if got := atomic.LoadInt32(&hits); got != 1 {
+		t.Fatalf("webhook hit %d times, want 1", got)
+	}
+	if gotSummary != "nightly audit" {
+		t.Fatalf("summary = %q, want %q", gotSummary, "nightly audit")
+	}
+}
+
+func TestMaybeAddWebhookSinkNoopWhenURLBlank(t *testing.T) {
+	n := New(&bytes.Buffer{}, Config{Mode: ModeBell, FocusMode: FocusAlways})
+
+	// Unset.
+	MaybeAddWebhookSink(n, envFunc(nil), nil)
+	// Set but blank / whitespace only.
+	MaybeAddWebhookSink(n, envFunc(map[string]string{EnvWebhookURL: "   "}), nil)
+
+	if got := len(n.sinks); got != 0 {
+		t.Fatalf("expected no sink attached, got %d", got)
+	}
+}
+
+func TestMaybeAddWebhookSinkNilGuards(t *testing.T) {
+	// Must not panic on a nil notifier or nil env resolver.
+	MaybeAddWebhookSink(nil, envFunc(map[string]string{EnvWebhookURL: "https://example.test"}), nil)
+
+	n := New(&bytes.Buffer{}, Config{Mode: ModeBell, FocusMode: FocusAlways})
+	MaybeAddWebhookSink(n, nil, nil)
+	if got := len(n.sinks); got != 0 {
+		t.Fatalf("nil env must attach nothing, got %d sinks", got)
+	}
+}

internal/oauth/device.go

@@ -0,0 +1,213 @@
+package oauth
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+const deviceGrantType = "urn:ietf:params:oauth:grant-type:device_code"
+
+// defaultDeviceCodeLifetime bounds a device authorization that omits expires_in,
+// so the expiry gate in PollDeviceToken is always active (fail closed).
+const defaultDeviceCodeLifetime = 10 * time.Minute
+
+// DeviceAuth is the result of an RFC 8628 device-authorization request.
+type DeviceAuth struct {
+	DeviceCode              string
+	UserCode                string
+	VerificationURI         string
+	VerificationURIComplete string
+	Interval                time.Duration
+	ExpiresAt               time.Time
+}
+
+type deviceAuthResponse struct {
+	DeviceCode              string `json:"device_code"`
+	UserCode                string `json:"user_code"`
+	VerificationURI         string `json:"verification_uri"`
+	VerificationURIComplete string `json:"verification_uri_complete"`
+	ExpiresIn               int64  `json:"expires_in"`
+	Interval                int64  `json:"interval"`
+	Error                   string `json:"error"`
+	ErrorDescription        string `json:"error_description"`
+}
+
+// RequestDeviceCode performs the RFC 8628 device-authorization request. This is
+// the headless/SSH login path (no browser, no loopback).
+func RequestDeviceCode(ctx context.Context, client *http.Client, cfg Config, now func() time.Time) (DeviceAuth, error) {
+	endpoint := trimmed(cfg.DeviceAuthorizationEndpoint)
+	if endpoint == "" {
+		return DeviceAuth{}, errors.New("oauth: provider has no device authorization endpoint")
+	}
+	if err := validateTokenEndpoint(endpoint); err != nil {
+		return DeviceAuth{}, err
+	}
+	if client == nil {
+		client = http.DefaultClient
+	}
+	if now == nil {
+		now = time.Now
+	}
+	form := url.Values{}
+	form.Set("client_id", cfg.ClientID)
+	if secret := trimmed(cfg.ClientSecret); secret != "" {
+		// Confidential clients must authenticate on the device endpoint too,
+		// consistent with the token poll (pollDeviceOnce).
+		form.Set("client_secret", secret)
+	}
+	if len(cfg.Scopes) > 0 {
+		form.Set("scope", strings.Join(cfg.Scopes, " "))
+	}
+	request, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, strings.NewReader(form.Encode()))
+	if err != nil {
+		return DeviceAuth{}, err
+	}
+	request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	request.Header.Set("Accept", "application/json")
+	response, err := client.Do(request)
+	if err != nil {
+		return DeviceAuth{}, fmt.Errorf("oauth: device authorization request failed: %w", err)
+	}
+	defer response.Body.Close()
+	body, _ := io.ReadAll(io.LimitReader(response.Body, tokenResponseLimit))
+	var parsed deviceAuthResponse
+	if len(body) > 0 {
+		_ = json.Unmarshal(body, &parsed)
+	}
+	if response.StatusCode < http.StatusOK || response.StatusCode >= http.StatusMultipleChoices {
+		if parsed.Error != "" {
+			return DeviceAuth{}, fmt.Errorf("oauth: device authorization error %q", parsed.Error)
+		}
+		return DeviceAuth{}, fmt.Errorf("oauth: device authorization returned HTTP %d", response.StatusCode)
+	}
+	if trimmed(parsed.DeviceCode) == "" || trimmed(parsed.UserCode) == "" {
+		return DeviceAuth{}, errors.New("oauth: device authorization response missing device_code/user_code")
+	}
+	interval := time.Duration(parsed.Interval) * time.Second
+	if interval <= 0 {
+		interval = 5 * time.Second // RFC 8628 default
+	}
+	auth := DeviceAuth{
+		DeviceCode:              parsed.DeviceCode,
+		UserCode:                parsed.UserCode,
+		VerificationURI:         parsed.VerificationURI,
+		VerificationURIComplete: parsed.VerificationURIComplete,
+		Interval:                interval,
+	}
+	lifetime := time.Duration(parsed.ExpiresIn) * time.Second
+	if lifetime <= 0 {
+		// Fail closed: a response without expires_in must still get a bounded
+		// lifetime so the poll loop's expiry gate stays active.
+		lifetime = defaultDeviceCodeLifetime
+	}
+	auth.ExpiresAt = now().Add(lifetime)
+	return auth, nil
+}
+
+// PollDeviceToken polls the token endpoint for the device grant until the user
+// approves, the device code expires, ctx is done, or a terminal error occurs. It
+// honors authorization_pending (keep waiting), slow_down (increase the
+// interval), and expired_token.
+func PollDeviceToken(ctx context.Context, client *http.Client, cfg Config, auth DeviceAuth, now func() time.Time) (Token, error) {
+	if now == nil {
+		now = time.Now
+	}
+	interval := auth.Interval
+	if interval <= 0 {
+		interval = 5 * time.Second
+	}
+	for {
+		if !auth.ExpiresAt.IsZero() && !auth.ExpiresAt.After(now()) {
+			return Token{}, errors.New("oauth: device code expired before authorization")
+		}
+		select {
+		case <-ctx.Done():
+			return Token{}, fmt.Errorf("oauth: device authorization canceled: %w", ctx.Err())
+		case <-time.After(interval):
+		}
+		// Re-check expiry after sleeping: slow_down (or a long interval) can push
+		// the next poll past ExpiresAt, and we must not poll after the deadline.
+		if !auth.ExpiresAt.IsZero() && !auth.ExpiresAt.After(now()) {
+			return Token{}, errors.New("oauth: device code expired before authorization")
+		}
+		token, err := pollDeviceOnce(ctx, client, cfg, auth.DeviceCode, now)
+		switch {
+		case err == nil:
+			return token, nil
+		case errors.Is(err, ErrAuthorizationPending):
+			// keep waiting at the current interval
+		case errors.Is(err, ErrSlowDown):
+			interval += 5 * time.Second // RFC 8628: add 5s on slow_down
+		default:
+			return Token{}, err
+		}
+	}
+}
+
+// pollDeviceOnce makes a single device-token poll, translating the RFC 8628
+// error codes into ErrAuthorizationPending / ErrSlowDown / terminal errors.
+func pollDeviceOnce(ctx context.Context, client *http.Client, cfg Config, deviceCode string, now func() time.Time) (Token, error) {
+	if err := validateTokenEndpoint(cfg.TokenEndpoint); err != nil {
+		return Token{}, err
+	}
+	if client == nil {
+		client = http.DefaultClient
+	}
+	form := url.Values{}
+	form.Set("grant_type", deviceGrantType)
+	form.Set("device_code", deviceCode)
+	form.Set("client_id", cfg.ClientID)
+	if secret := trimmed(cfg.ClientSecret); secret != "" {
+		form.Set("client_secret", secret)
+	}
+	request, err := http.NewRequestWithContext(ctx, http.MethodPost, trimmed(cfg.TokenEndpoint), strings.NewReader(form.Encode()))
+	if err != nil {
+		return Token{}, err
+	}
+	request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	request.Header.Set("Accept", "application/json")
+	response, err := client.Do(request)
+	if err != nil {
+		return Token{}, fmt.Errorf("oauth: device token poll failed: %w", err)
+	}
+	defer response.Body.Close()
+	body, _ := io.ReadAll(io.LimitReader(response.Body, tokenResponseLimit))
+	var parsed tokenResponse
+	if len(body) > 0 {
+		_ = json.Unmarshal(body, &parsed)
+	}
+	if response.StatusCode >= http.StatusOK && response.StatusCode < http.StatusMultipleChoices && trimmed(parsed.AccessToken) != "" {
+		token := Token{Scopes: cfg.Scopes}
+		token.AccessToken = parsed.AccessToken
+		token.RefreshToken = parsed.RefreshToken
+		token.TokenType = parsed.TokenType
+		if parsed.ExpiresIn > 0 {
+			token.ExpiresAt = now().Add(time.Duration(parsed.ExpiresIn) * time.Second).UTC()
+		}
+		if scope := trimmed(parsed.Scope); scope != "" {
+			token.Scopes = strings.Fields(scope)
+		}
+		return token, nil
+	}
+	switch parsed.Error {
+	case "authorization_pending":
+		return Token{}, ErrAuthorizationPending
+	case "slow_down":
+		return Token{}, ErrSlowDown
+	case "expired_token":
+		return Token{}, errors.New("oauth: device code expired before authorization")
+	case "access_denied":
+		return Token{}, errors.New("oauth: authorization denied by the user")
+	case "":
+		return Token{}, fmt.Errorf("oauth: device token poll returned HTTP %d", response.StatusCode)
+	default:
+		return Token{}, fmt.Errorf("oauth: device token error %q", parsed.Error)
+	}
+}

internal/oauth/device_test.go

@@ -0,0 +1,143 @@
+package oauth
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestRequestDeviceCodeSendsClientSecret(t *testing.T) {
+	var gotSecret string
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_ = r.ParseForm()
+		gotSecret = r.Form.Get("client_secret")
+		_, _ = w.Write([]byte(`{"device_code":"dc","user_code":"U","verification_uri":"https://x","expires_in":600,"interval":5}`))
+	}))
+	defer server.Close()
+	// A confidential client must authenticate on the device endpoint too.
+	_, err := RequestDeviceCode(context.Background(), server.Client(), Config{ClientID: "c", ClientSecret: "shh", DeviceAuthorizationEndpoint: server.URL}, nil)
+	if err != nil {
+		t.Fatalf("RequestDeviceCode: %v", err)
+	}
+	if gotSecret != "shh" {
+		t.Fatalf("client_secret = %q, want shh", gotSecret)
+	}
+}
+
+func TestRequestDeviceCode(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write([]byte(`{"device_code":"dc","user_code":"WXYZ-1234","verification_uri":"https://x/dev","verification_uri_complete":"https://x/dev?c=WXYZ","expires_in":600,"interval":3}`))
+	}))
+	defer server.Close()
+	cfg := Config{ClientID: "c", DeviceAuthorizationEndpoint: server.URL, Scopes: []string{"a"}}
+	auth, err := RequestDeviceCode(context.Background(), server.Client(), cfg, nil)
+	if err != nil {
+		t.Fatalf("RequestDeviceCode: %v", err)
+	}
+	if auth.DeviceCode != "dc" || auth.UserCode != "WXYZ-1234" {
+		t.Fatalf("device auth = %+v", auth)
+	}
+	if auth.Interval != 3*time.Second {
+		t.Fatalf("interval = %v, want 3s", auth.Interval)
+	}
+	if auth.VerificationURIComplete == "" {
+		t.Fatal("missing verification_uri_complete")
+	}
+}
+
+func TestRequestDeviceCodeDefaultsInterval(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write([]byte(`{"device_code":"dc","user_code":"U","verification_uri":"https://x"}`))
+	}))
+	defer server.Close()
+	auth, err := RequestDeviceCode(context.Background(), server.Client(), Config{ClientID: "c", DeviceAuthorizationEndpoint: server.URL}, nil)
+	if err != nil {
+		t.Fatalf("RequestDeviceCode: %v", err)
+	}
+	if auth.Interval != 5*time.Second {
+		t.Fatalf("default interval = %v, want 5s", auth.Interval)
+	}
+	// A response without expires_in must still get a bounded expiry (fail closed),
+	// so the poll loop's expiry gate stays active.
+	if auth.ExpiresAt.IsZero() {
+		t.Fatal("missing expires_in must default to a bounded ExpiresAt, got zero")
+	}
+}
+
+func TestPollDeviceTokenHonorsPendingThenSucceeds(t *testing.T) {
+	var calls atomic.Int32
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		n := calls.Add(1)
+		if n < 3 {
+			w.WriteHeader(http.StatusBadRequest)
+			_, _ = w.Write([]byte(`{"error":"authorization_pending"}`))
+			return
+		}
+		_, _ = w.Write([]byte(`{"access_token":"at","token_type":"Bearer","expires_in":3600}`))
+	}))
+	defer server.Close()
+	cfg := Config{ClientID: "c", TokenEndpoint: server.URL}
+	// Small interval + future expiry so the loop is fast.
+	auth := DeviceAuth{DeviceCode: "dc", Interval: 5 * time.Millisecond, ExpiresAt: time.Now().Add(5 * time.Second)}
+	tok, err := PollDeviceToken(context.Background(), server.Client(), cfg, auth, nil)
+	if err != nil {
+		t.Fatalf("PollDeviceToken: %v", err)
+	}
+	if tok.AccessToken != "at" {
+		t.Fatalf("token = %+v", tok)
+	}
+	if calls.Load() != 3 {
+		t.Fatalf("polled %d times, want 3 (2 pending + 1 success)", calls.Load())
+	}
+}
+
+func TestPollDeviceTokenSlowDown(t *testing.T) {
+	var calls atomic.Int32
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		if calls.Add(1) == 1 {
+			w.WriteHeader(http.StatusBadRequest)
+			_, _ = w.Write([]byte(`{"error":"slow_down"}`))
+			return
+		}
+		_, _ = w.Write([]byte(`{"access_token":"at"}`))
+	}))
+	defer server.Close()
+	cfg := Config{ClientID: "c", TokenEndpoint: server.URL}
+	// Expiry well beyond the slow_down back-off (+5s) so the success path never
+	// depends on polling after the device code has expired.
+	auth := DeviceAuth{DeviceCode: "dc", Interval: 5 * time.Millisecond, ExpiresAt: time.Now().Add(30 * time.Second)}
+	tok, err := PollDeviceToken(context.Background(), server.Client(), cfg, auth, nil)
+	if err != nil {
+		t.Fatalf("PollDeviceToken (slow_down): %v", err)
+	}
+	if tok.AccessToken != "at" {
+		t.Fatalf("token = %+v", tok)
+	}
+}
+
+func TestPollDeviceTokenExpired(t *testing.T) {
+	cfg := Config{ClientID: "c", TokenEndpoint: "https://unused/token"}
+	auth := DeviceAuth{DeviceCode: "dc", Interval: time.Millisecond, ExpiresAt: time.Now().Add(-time.Second)}
+	_, err := PollDeviceToken(context.Background(), http.DefaultClient, cfg, auth, nil)
+	if err == nil {
+		t.Fatal("expected expired error")
+	}
+}
+
+func TestPollDeviceTokenAccessDenied(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusBadRequest)
+		_, _ = w.Write([]byte(`{"error":"access_denied"}`))
+	}))
+	defer server.Close()
+	cfg := Config{ClientID: "c", TokenEndpoint: server.URL}
+	auth := DeviceAuth{DeviceCode: "dc", Interval: 5 * time.Millisecond, ExpiresAt: time.Now().Add(5 * time.Second)}
+	_, err := PollDeviceToken(context.Background(), server.Client(), cfg, auth, nil)
+	if err == nil || !strings.Contains(err.Error(), "denied") {
+		t.Fatalf("err = %v, want access denied", err)
+	}
+}

internal/oauth/discovery.go

@@ -0,0 +1,79 @@
+package oauth
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+const wellKnownAuthServerPath = "/.well-known/oauth-authorization-server"
+
+// ServerMetadata is the subset of an RFC 8414 authorization-server metadata
+// document the engine consumes.
+type ServerMetadata struct {
+	Issuer                      string   `json:"issuer"`
+	AuthorizationEndpoint       string   `json:"authorization_endpoint"`
+	TokenEndpoint               string   `json:"token_endpoint"`
+	DeviceAuthorizationEndpoint string   `json:"device_authorization_endpoint"`
+	RegistrationEndpoint        string   `json:"registration_endpoint"`
+	ScopesSupported             []string `json:"scopes_supported"`
+}
+
+// DiscoverAuthorizationServer fetches the RFC 8414 metadata document at the
+// well-known path under baseURL.
+func DiscoverAuthorizationServer(ctx context.Context, client *http.Client, baseURL string) (ServerMetadata, error) {
+	metadataURL, err := joinWellKnown(baseURL)
+	if err != nil {
+		return ServerMetadata{}, err
+	}
+	return fetchMetadata(ctx, client, metadataURL)
+}
+
+// fetchMetadata GETs and decodes an authorization-server metadata document at an
+// already-resolved URL (no well-known recomputation), so callers can also use it
+// for the OIDC openid-configuration path.
+func fetchMetadata(ctx context.Context, client *http.Client, metadataURL string) (ServerMetadata, error) {
+	if client == nil {
+		client = http.DefaultClient
+	}
+	request, err := http.NewRequestWithContext(ctx, http.MethodGet, metadataURL, nil)
+	if err != nil {
+		return ServerMetadata{}, err
+	}
+	request.Header.Set("Accept", "application/json")
+	response, err := client.Do(request)
+	if err != nil {
+		return ServerMetadata{}, fmt.Errorf("oauth: fetch authorization server metadata: %w", err)
+	}
+	defer response.Body.Close()
+	if response.StatusCode < http.StatusOK || response.StatusCode >= http.StatusMultipleChoices {
+		return ServerMetadata{}, fmt.Errorf("oauth: authorization server metadata returned HTTP %d", response.StatusCode)
+	}
+	var metadata ServerMetadata
+	if err := json.NewDecoder(io.LimitReader(response.Body, tokenResponseLimit)).Decode(&metadata); err != nil {
+		return ServerMetadata{}, fmt.Errorf("oauth: decode authorization server metadata: %w", err)
+	}
+	return metadata, nil
+}
+
+// joinWellKnown builds the RFC 8414 metadata URL, inserting the well-known
+// segment between host and any issuer path component (so a path-based issuer is
+// probed tenant-scoped, not at the host root).
+func joinWellKnown(baseURL string) (string, error) {
+	parsed, err := url.Parse(trimmed(baseURL))
+	if err != nil || parsed.Host == "" {
+		return "", fmt.Errorf("oauth: invalid base URL for metadata discovery: %q", baseURL)
+	}
+	issuerPath := strings.Trim(parsed.Path, "/")
+	parsed.Path = wellKnownAuthServerPath
+	if issuerPath != "" {
+		parsed.Path = strings.TrimRight(wellKnownAuthServerPath, "/") + "/" + issuerPath
+	}
+	parsed.RawQuery = ""
+	parsed.Fragment = ""
+	return parsed.String(), nil
+}

internal/oauth/encrypt.go

@@ -0,0 +1,147 @@
+package oauth
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+// secretBytes is the AES-256 key length kept in the per-user secret file.
+const secretBytes = 32
+
+// aesGCMCrypter encrypts the token file at rest with AES-256-GCM under a
+// per-user random secret persisted (0600) beside the token file. The on-disk
+// blob is nonce || ciphertext; GCM provides confidentiality AND tamper
+// detection, so a corrupted/forged file fails closed on open. This is the
+// opt-in "encrypted-file" storage backend; the default backend writes the
+// 0600 plaintext JSON unchanged.
+type aesGCMCrypter struct {
+	secretPath string
+}
+
+func newAESGCMCrypter(secretPath string) *aesGCMCrypter {
+	return &aesGCMCrypter{secretPath: secretPath}
+}
+
+// aead loads (or, when create is set, generates) the secret and returns the GCM
+// AEAD. open passes create=false so a missing secret is a hard error rather than
+// silently minting a new key that could never decrypt the existing file.
+func (c *aesGCMCrypter) aead(create bool) (cipher.AEAD, error) {
+	secret, err := loadOrCreateSecret(c.secretPath, create)
+	if err != nil {
+		return nil, err
+	}
+	block, err := aes.NewCipher(secret)
+	if err != nil {
+		return nil, fmt.Errorf("oauth: build cipher: %w", err)
+	}
+	return cipher.NewGCM(block)
+}
+
+// seal encrypts plaintext, prefixing a fresh random nonce. It creates the secret
+// on first use.
+func (c *aesGCMCrypter) seal(plaintext []byte) ([]byte, error) {
+	gcm, err := c.aead(true)
+	if err != nil {
+		return nil, err
+	}
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return nil, fmt.Errorf("oauth: generate nonce: %w", err)
+	}
+	return gcm.Seal(nonce, nonce, plaintext, nil), nil
+}
+
+// open decrypts a nonce||ciphertext blob, failing closed on a missing secret,
+// a short blob, or a failed authentication tag (tampering / wrong key).
+func (c *aesGCMCrypter) open(blob []byte) ([]byte, error) {
+	gcm, err := c.aead(false)
+	if err != nil {
+		return nil, err
+	}
+	if len(blob) < gcm.NonceSize() {
+		return nil, errors.New("oauth: encrypted token file is too short")
+	}
+	nonce, ciphertext := blob[:gcm.NonceSize()], blob[gcm.NonceSize():]
+	plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return nil, fmt.Errorf("oauth: decrypt token file (wrong secret or tampered): %w", err)
+	}
+	return plaintext, nil
+}
+
+// loadOrCreateSecret reads the 32-byte secret at path. When create is set and
+// the file is absent, it generates a random secret and creates the file
+// exclusively (0600). A wrong-sized existing secret fails closed (corruption).
+func loadOrCreateSecret(path string, create bool) ([]byte, error) {
+	if data, err := readSecretFile(path); err == nil {
+		return data, nil
+	} else if !errors.Is(err, os.ErrNotExist) {
+		return nil, err
+	}
+	if !create {
+		return nil, fmt.Errorf("oauth: token secret %s is missing; cannot decrypt the token file", path)
+	}
+	secret := make([]byte, secretBytes)
+	if _, err := io.ReadFull(rand.Reader, secret); err != nil {
+		return nil, fmt.Errorf("oauth: generate token secret: %w", err)
+	}
+	if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
+		return nil, err
+	}
+	// Create exclusively: an os.Rename publish would clobber on POSIX, so two
+	// concurrent first-run processes could each generate a secret and the loser
+	// would silently orphan the tokens it encrypts. O_EXCL lets exactly one
+	// process win; everyone else adopts the winner's on-disk secret.
+	f, err := os.OpenFile(path, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
+	if err != nil {
+		if errors.Is(err, os.ErrExist) {
+			// The winner may not have finished writing yet, so a read here can see a
+			// short/absent file. Retry briefly so concurrent first-run invocations
+			// converge on the winner's secret instead of failing transiently.
+			var lastErr error
+			for attempt := 0; attempt < 50; attempt++ {
+				secret, rerr := readSecretFile(path)
+				if rerr == nil {
+					return secret, nil
+				}
+				lastErr = rerr
+				time.Sleep(2 * time.Millisecond)
+			}
+			return nil, lastErr
+		}
+		return nil, fmt.Errorf("oauth: create token secret: %w", err)
+	}
+	if _, werr := f.Write(secret); werr != nil {
+		_ = f.Close()
+		_ = os.Remove(path)
+		return nil, fmt.Errorf("oauth: write token secret: %w", werr)
+	}
+	if cerr := f.Close(); cerr != nil {
+		_ = os.Remove(path)
+		return nil, fmt.Errorf("oauth: write token secret: %w", cerr)
+	}
+	return secret, nil
+}
+
+// readSecretFile reads and validates the secret at path, returning a wrapped
+// os.ErrNotExist when it is absent so callers can branch on creation.
+func readSecretFile(path string) ([]byte, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, err
+		}
+		return nil, fmt.Errorf("oauth: read token secret: %w", err)
+	}
+	if len(data) != secretBytes {
+		return nil, fmt.Errorf("oauth: token secret at %s has unexpected size %d", path, len(data))
+	}
+	return data, nil
+}

internal/oauth/encrypt_test.go

@@ -0,0 +1,204 @@
+package oauth
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+)
+
+func TestLoadOrCreateSecretConcurrentConverges(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "tok.json.secret")
+	const n = 16
+	secrets := make([][]byte, n)
+	errs := make([]error, n)
+	var wg sync.WaitGroup
+	for i := 0; i < n; i++ {
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+			secrets[i], errs[i] = loadOrCreateSecret(path, true)
+		}(i)
+	}
+	wg.Wait()
+	// Exactly one creator wins; every racer must converge on the same on-disk
+	// secret rather than orphaning its own (the O_EXCL + bounded-retry path).
+	for i := 0; i < n; i++ {
+		if errs[i] != nil {
+			t.Fatalf("goroutine %d: %v", i, errs[i])
+		}
+		if !bytes.Equal(secrets[i], secrets[0]) {
+			t.Fatalf("goroutine %d got a divergent secret; concurrent create did not converge", i)
+		}
+	}
+}
+
+func TestAESGCMCrypterRoundTripAndTamper(t *testing.T) {
+	secretPath := filepath.Join(t.TempDir(), "tok.json.secret")
+	c := newAESGCMCrypter(secretPath)
+	plaintext := []byte(`{"schemaVersion":1,"tokens":{}}`)
+	blob, err := c.seal(plaintext)
+	if err != nil {
+		t.Fatalf("seal: %v", err)
+	}
+	if bytes.Contains(blob, plaintext) {
+		t.Fatal("sealed blob must not contain the plaintext")
+	}
+	got, err := c.open(blob)
+	if err != nil {
+		t.Fatalf("open: %v", err)
+	}
+	if !bytes.Equal(got, plaintext) {
+		t.Fatalf("round-trip mismatch: %q", got)
+	}
+	// Tamper: flipping any byte breaks the GCM tag.
+	tampered := append([]byte(nil), blob...)
+	tampered[len(tampered)-1] ^= 0xff
+	if _, err := c.open(tampered); err == nil {
+		t.Fatal("open must reject a tampered blob (GCM auth)")
+	}
+}
+
+func TestLoadOrCreateSecret(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "tok.json.secret")
+	// Missing + create=false => fail closed (can't decrypt without the secret).
+	if _, err := loadOrCreateSecret(path, false); err == nil {
+		t.Fatal("missing secret with create=false must error")
+	}
+	secret, err := loadOrCreateSecret(path, true)
+	if err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	if len(secret) != secretBytes {
+		t.Fatalf("secret length = %d, want %d", len(secret), secretBytes)
+	}
+	// Stable across reads.
+	again, err := loadOrCreateSecret(path, false)
+	if err != nil || !bytes.Equal(again, secret) {
+		t.Fatalf("secret not stable: %v", err)
+	}
+	if runtime.GOOS != "windows" {
+		info, err := os.Stat(path)
+		if err != nil {
+			t.Fatalf("stat secret: %v", err)
+		}
+		if perm := info.Mode().Perm(); perm != 0o600 {
+			t.Fatalf("secret file mode = %o, want 600", perm)
+		}
+	}
+	// Wrong-sized secret fails closed.
+	if err := os.WriteFile(path, []byte("short"), 0o600); err != nil {
+		t.Fatalf("corrupt secret: %v", err)
+	}
+	if _, err := loadOrCreateSecret(path, true); err == nil {
+		t.Fatal("wrong-sized secret must error")
+	}
+}
+
+func newEncryptedStore(t *testing.T) (*Store, string) {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "oauth-tokens.json")
+	s, err := NewStore(StoreOptions{FilePath: path, Encrypted: true})
+	if err != nil {
+		t.Fatalf("NewStore(encrypted): %v", err)
+	}
+	return s, path
+}
+
+// The unified Storage="encrypted-file" selector must encrypt at rest, the same as
+// the legacy Encrypted:true alias (the file/keyring/encrypted-file merge).
+func TestNewStoreEncryptedFileStorageSelector(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "oauth-tokens.json")
+	s, err := NewStore(StoreOptions{FilePath: path, Storage: "encrypted-file"})
+	if err != nil {
+		t.Fatalf("NewStore(encrypted-file): %v", err)
+	}
+	if err := s.Save(ProviderKey("demo"), Token{AccessToken: "super-secret-access"}); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("read: %v", err)
+	}
+	if strings.Contains(string(raw), "super-secret-access") || strings.Contains(string(raw), "schemaVersion") {
+		t.Fatalf("Storage=encrypted-file did not encrypt at rest:\n%s", raw)
+	}
+	got, ok, err := s.Load(ProviderKey("demo"))
+	if err != nil || !ok || got.AccessToken != "super-secret-access" {
+		t.Fatalf("Load = %+v ok=%v err=%v", got, ok, err)
+	}
+}
+
+func TestEncryptedStoreRoundTripAndCiphertextOnDisk(t *testing.T) {
+	s, path := newEncryptedStore(t)
+	tok := Token{AccessToken: "super-secret-access", RefreshToken: "super-secret-refresh", Account: "me@x"}
+	if err := s.Save(ProviderKey("demo"), tok); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	// On-disk file must be ciphertext: not valid JSON, no plaintext token.
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("read file: %v", err)
+	}
+	if strings.Contains(string(raw), "super-secret-access") || strings.Contains(string(raw), "schemaVersion") {
+		t.Fatalf("token file is not encrypted at rest:\n%s", raw)
+	}
+	// The secret file exists beside it.
+	if _, err := os.Stat(path + ".secret"); err != nil {
+		t.Fatalf("secret file missing: %v", err)
+	}
+	// A fresh Store (same path) decrypts and reads it back.
+	s2, err := NewStore(StoreOptions{FilePath: path, Encrypted: true})
+	if err != nil {
+		t.Fatalf("NewStore 2: %v", err)
+	}
+	got, ok, err := s2.Load(ProviderKey("demo"))
+	if err != nil || !ok || got.AccessToken != "super-secret-access" || got.Account != "me@x" {
+		t.Fatalf("Load = %+v ok=%v err=%v", got, ok, err)
+	}
+	// Delete + Status work through the encrypted backend too.
+	statuses, err := s2.Status(KeyPrefixProvider)
+	if err != nil || len(statuses) != 1 {
+		t.Fatalf("Status = %+v err=%v", statuses, err)
+	}
+	if removed, err := s2.Delete(ProviderKey("demo")); err != nil || !removed {
+		t.Fatalf("Delete = %v %v", removed, err)
+	}
+}
+
+func TestEncryptedStoreTamperFailsClosed(t *testing.T) {
+	s, path := newEncryptedStore(t)
+	if err := s.Save(ProviderKey("demo"), Token{AccessToken: "a"}); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("read file: %v", err)
+	}
+	if len(raw) == 0 {
+		t.Fatal("encrypted token file is empty")
+	}
+	raw[len(raw)-1] ^= 0xff
+	if err := os.WriteFile(path, raw, 0o600); err != nil {
+		t.Fatalf("rewrite: %v", err)
+	}
+	if _, _, err := s.Load(ProviderKey("demo")); err == nil {
+		t.Fatal("a tampered encrypted store must fail closed")
+	}
+}
+
+func TestEncryptedStoreMissingSecretFailsClosed(t *testing.T) {
+	s, path := newEncryptedStore(t)
+	if err := s.Save(ProviderKey("demo"), Token{AccessToken: "a"}); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	if err := os.Remove(path + ".secret"); err != nil {
+		t.Fatalf("remove secret: %v", err)
+	}
+	if _, _, err := s.Load(ProviderKey("demo")); err == nil {
+		t.Fatal("missing secret must fail closed, not return empty")
+	}
+}

internal/oauth/flow.go

@@ -0,0 +1,212 @@
+package oauth
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+const tokenResponseLimit = 1 << 20 // 1 MiB cap on token-endpoint bodies
+
+// tokenResponse is the JSON returned by a token endpoint.
+type tokenResponse struct {
+	AccessToken      string `json:"access_token"`
+	RefreshToken     string `json:"refresh_token"`
+	TokenType        string `json:"token_type"`
+	ExpiresIn        int64  `json:"expires_in"`
+	Scope            string `json:"scope"`
+	Error            string `json:"error"`
+	ErrorDescription string `json:"error_description"`
+}
+
+// BuildAuthorizationURL constructs the authorization request URL for an
+// authorization-code + PKCE flow. PKCE S256 is always included; a non-S256
+// method is refused (ErrPKCEDowngrade). extraParams (and cfg.ExtraAuthParams)
+// are appended last.
+func BuildAuthorizationURL(cfg Config, pkce PKCE, state, redirectURI string, extraParams map[string]string) (string, error) {
+	if pkce.Method != MethodS256 {
+		return "", ErrPKCEDowngrade
+	}
+	endpoint := trimmed(cfg.AuthorizationEndpoint)
+	if endpoint == "" {
+		return "", errors.New("oauth: no authorization endpoint configured")
+	}
+	parsed, err := url.Parse(endpoint)
+	if err != nil {
+		return "", fmt.Errorf("oauth: parse authorization endpoint: %w", err)
+	}
+	query := parsed.Query()
+	query.Set("response_type", "code")
+	query.Set("client_id", cfg.ClientID)
+	query.Set("redirect_uri", redirectURI)
+	query.Set("state", state)
+	query.Set("code_challenge", pkce.Challenge)
+	query.Set("code_challenge_method", pkce.Method)
+	if len(cfg.Scopes) > 0 {
+		query.Set("scope", strings.Join(cfg.Scopes, " "))
+	}
+	// Extra params must never override the reserved OAuth/PKCE fields above
+	// (e.g. forcing code_challenge_method=plain or rewriting state/redirect_uri),
+	// which would break the flow's security guarantees.
+	for k, v := range cfg.ExtraAuthParams {
+		if isReservedAuthParam(k) {
+			continue
+		}
+		query.Set(k, v)
+	}
+	for k, v := range extraParams {
+		if isReservedAuthParam(k) {
+			continue
+		}
+		query.Set(k, v)
+	}
+	parsed.RawQuery = query.Encode()
+	return parsed.String(), nil
+}
+
+// isReservedAuthParam reports whether a query key is one the engine controls and
+// must not be overridable by caller-supplied extra params.
+func isReservedAuthParam(key string) bool {
+	switch key {
+	case "response_type", "client_id", "redirect_uri", "state", "code_challenge", "code_challenge_method":
+		return true
+	default:
+		return false
+	}
+}
+
+// validateTokenEndpoint refuses to send a credential to a token endpoint that is
+// not https, unless it is a loopback host (mirrors oauth2-client.js
+// validateTokenEndpointURL). This prevents leaking codes/tokens over cleartext.
+func validateTokenEndpoint(endpoint string) error {
+	parsed, err := url.Parse(trimmed(endpoint))
+	if err != nil || parsed.Host == "" {
+		return fmt.Errorf("oauth: invalid token endpoint %q", endpoint)
+	}
+	if parsed.Scheme == "https" {
+		return nil
+	}
+	if parsed.Scheme == "http" && isLoopbackHost(parsed.Hostname()) {
+		return nil
+	}
+	return fmt.Errorf("%w: %s", ErrInsecureTokenEndpoint, parsed.Scheme+"://"+parsed.Host)
+}
+
+func isLoopbackHost(host string) bool {
+	if host == "localhost" {
+		return true
+	}
+	if ip := net.ParseIP(host); ip != nil {
+		return ip.IsLoopback()
+	}
+	return false
+}
+
+// ExchangeCode swaps an authorization code + PKCE verifier for tokens.
+func ExchangeCode(ctx context.Context, client *http.Client, cfg Config, code, verifier, redirectURI string, now func() time.Time) (Token, error) {
+	form := url.Values{}
+	form.Set("grant_type", "authorization_code")
+	form.Set("code", code)
+	form.Set("redirect_uri", redirectURI)
+	form.Set("client_id", cfg.ClientID)
+	form.Set("code_verifier", verifier)
+	if secret := trimmed(cfg.ClientSecret); secret != "" {
+		form.Set("client_secret", secret)
+	}
+	return PostToken(ctx, client, cfg.TokenEndpoint, form, Token{Scopes: cfg.Scopes}, now)
+}
+
+// Refresh exchanges a refresh token for a fresh access token. A response that
+// omits a new refresh token preserves the current one.
+func Refresh(ctx context.Context, client *http.Client, cfg Config, current Token, now func() time.Time) (Token, error) {
+	refresh := trimmed(current.RefreshToken)
+	if refresh == "" {
+		return Token{}, ErrNoRefreshToken
+	}
+	if trimmed(cfg.TokenEndpoint) == "" {
+		return Token{}, errors.New("oauth: no token endpoint configured for refresh")
+	}
+	form := url.Values{}
+	form.Set("grant_type", "refresh_token")
+	form.Set("refresh_token", refresh)
+	form.Set("client_id", cfg.ClientID)
+	if secret := trimmed(cfg.ClientSecret); secret != "" {
+		form.Set("client_secret", secret)
+	}
+	if len(cfg.Scopes) > 0 {
+		form.Set("scope", strings.Join(cfg.Scopes, " "))
+	}
+	base := Token{Scopes: current.Scopes, RefreshToken: refresh, Account: current.Account}
+	return PostToken(ctx, client, cfg.TokenEndpoint, form, base, now)
+}
+
+// PostToken performs a token-endpoint POST and maps the response onto a Token.
+// The https guard is applied first. The base token supplies values to preserve
+// (e.g. an existing refresh token or scopes) when the response omits them.
+// Error messages carry only the server's error/error_description — never the raw
+// body — so token material in an unexpected payload is not leaked.
+func PostToken(ctx context.Context, client *http.Client, tokenEndpoint string, form url.Values, base Token, now func() time.Time) (Token, error) {
+	if err := validateTokenEndpoint(tokenEndpoint); err != nil {
+		return Token{}, err
+	}
+	if client == nil {
+		client = http.DefaultClient
+	}
+	if now == nil {
+		now = time.Now
+	}
+	request, err := http.NewRequestWithContext(ctx, http.MethodPost, trimmed(tokenEndpoint), strings.NewReader(form.Encode()))
+	if err != nil {
+		return Token{}, err
+	}
+	request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	request.Header.Set("Accept", "application/json")
+
+	response, err := client.Do(request)
+	if err != nil {
+		return Token{}, fmt.Errorf("oauth: token request failed: %w", err)
+	}
+	defer response.Body.Close()
+
+	body, _ := io.ReadAll(io.LimitReader(response.Body, tokenResponseLimit))
+	var parsed tokenResponse
+	if len(body) > 0 {
+		_ = json.Unmarshal(body, &parsed)
+	}
+
+	if response.StatusCode < http.StatusOK || response.StatusCode >= http.StatusMultipleChoices {
+		if parsed.Error != "" {
+			if parsed.ErrorDescription != "" {
+				return Token{}, fmt.Errorf("oauth: token endpoint error %q: %s", parsed.Error, parsed.ErrorDescription)
+			}
+			return Token{}, fmt.Errorf("oauth: token endpoint error %q", parsed.Error)
+		}
+		return Token{}, fmt.Errorf("oauth: token endpoint returned HTTP %d", response.StatusCode)
+	}
+	if trimmed(parsed.AccessToken) == "" {
+		return Token{}, errors.New("oauth: token endpoint returned no access token")
+	}
+
+	token := base
+	token.AccessToken = parsed.AccessToken
+	if trimmed(parsed.RefreshToken) != "" {
+		token.RefreshToken = parsed.RefreshToken
+	}
+	if trimmed(parsed.TokenType) != "" {
+		token.TokenType = parsed.TokenType
+	}
+	if parsed.ExpiresIn > 0 {
+		token.ExpiresAt = now().Add(time.Duration(parsed.ExpiresIn) * time.Second).UTC()
+	}
+	if scope := trimmed(parsed.Scope); scope != "" {
+		token.Scopes = strings.Fields(scope)
+	}
+	return token, nil
+}

internal/oauth/flow_test.go

@@ -0,0 +1,212 @@
+package oauth
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/base64"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestNewPKCE(t *testing.T) {
+	p, err := NewPKCE()
+	if err != nil {
+		t.Fatalf("NewPKCE: %v", err)
+	}
+	if p.Method != MethodS256 {
+		t.Fatalf("method = %q, want S256", p.Method)
+	}
+	if len(p.Verifier) != 43 { // base64url(32 bytes) = 43 chars
+		t.Fatalf("verifier length = %d, want 43", len(p.Verifier))
+	}
+	sum := sha256.Sum256([]byte(p.Verifier))
+	want := base64.RawURLEncoding.EncodeToString(sum[:])
+	if p.Challenge != want {
+		t.Fatalf("challenge = %q, want base64url(sha256(verifier))", p.Challenge)
+	}
+}
+
+func TestNewStateUnique(t *testing.T) {
+	seen := map[string]bool{}
+	for i := 0; i < 100; i++ {
+		s, err := NewState()
+		if err != nil {
+			t.Fatalf("NewState: %v", err)
+		}
+		if s == "" || seen[s] {
+			t.Fatalf("state not unique/non-empty: %q", s)
+		}
+		seen[s] = true
+	}
+}
+
+func TestBuildAuthorizationURL(t *testing.T) {
+	cfg := Config{
+		ClientID:              "client-123",
+		Scopes:                []string{"read", "write"},
+		AuthorizationEndpoint: "https://auth.example.com/authorize",
+		ExtraAuthParams:       map[string]string{"login_hint": "[email protected]"},
+	}
+	pkce := PKCE{Verifier: "v", Challenge: "chal", Method: MethodS256}
+	raw, err := BuildAuthorizationURL(cfg, pkce, "state-xyz", "http://127.0.0.1:9/callback", map[string]string{"prompt": "login"})
+	if err != nil {
+		t.Fatalf("BuildAuthorizationURL: %v", err)
+	}
+	u, _ := url.Parse(raw)
+	q := u.Query()
+	checks := map[string]string{
+		"response_type":         "code",
+		"client_id":             "client-123",
+		"redirect_uri":          "http://127.0.0.1:9/callback",
+		"state":                 "state-xyz",
+		"code_challenge":        "chal",
+		"code_challenge_method": "S256",
+		"scope":                 "read write",
+		"login_hint":            "[email protected]",
+		"prompt":                "login",
+	}
+	for k, want := range checks {
+		if got := q.Get(k); got != want {
+			t.Errorf("query %q = %q, want %q", k, got, want)
+		}
+	}
+}
+
+func TestBuildAuthorizationURLIgnoresReservedExtras(t *testing.T) {
+	cfg := Config{
+		ClientID:              "c",
+		AuthorizationEndpoint: "https://auth.example.com/authorize",
+		// A hostile config tries to weaken the flow via extra params.
+		ExtraAuthParams: map[string]string{"state": "attacker", "code_challenge_method": "plain", "login_hint": "keep-me"},
+	}
+	pkce := PKCE{Challenge: "chal", Method: MethodS256}
+	raw, err := BuildAuthorizationURL(cfg, pkce, "real-state", "http://127.0.0.1:9/cb", map[string]string{"redirect_uri": "http://evil/cb"})
+	if err != nil {
+		t.Fatalf("BuildAuthorizationURL: %v", err)
+	}
+	parsed, _ := url.Parse(raw)
+	q := parsed.Query()
+	if q.Get("state") != "real-state" {
+		t.Fatalf("state overridden: %q", q.Get("state"))
+	}
+	if q.Get("code_challenge_method") != "S256" {
+		t.Fatalf("PKCE method downgraded: %q", q.Get("code_challenge_method"))
+	}
+	if q.Get("redirect_uri") != "http://127.0.0.1:9/cb" {
+		t.Fatalf("redirect_uri overridden: %q", q.Get("redirect_uri"))
+	}
+	if q.Get("login_hint") != "keep-me" {
+		t.Fatalf("non-reserved extra param should still apply: %q", q.Get("login_hint"))
+	}
+}
+
+func TestBuildAuthorizationURLRejectsPlain(t *testing.T) {
+	_, err := BuildAuthorizationURL(Config{AuthorizationEndpoint: "https://a/x"}, PKCE{Method: "plain"}, "s", "r", nil)
+	if !errors.Is(err, ErrPKCEDowngrade) {
+		t.Fatalf("err = %v, want ErrPKCEDowngrade", err)
+	}
+}
+
+func TestValidateTokenEndpoint(t *testing.T) {
+	cases := map[string]bool{
+		"https://auth.example.com/token": true,
+		"http://127.0.0.1:1455/token":    true, // loopback exempt
+		"http://localhost:1455/token":    true,
+		"http://[::1]:1455/token":        true,
+		"http://auth.example.com/token":  false, // non-https, non-loopback
+		"ftp://auth.example.com/token":   false,
+	}
+	for endpoint, ok := range cases {
+		err := validateTokenEndpoint(endpoint)
+		if ok && err != nil {
+			t.Errorf("validateTokenEndpoint(%q) = %v, want nil", endpoint, err)
+		}
+		if !ok && err == nil {
+			t.Errorf("validateTokenEndpoint(%q) = nil, want error", endpoint)
+		}
+	}
+}
+
+func TestExchangeCodeSuccess(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_ = r.ParseForm()
+		if r.FormValue("grant_type") != "authorization_code" || r.FormValue("code_verifier") != "verifier" {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"access_token":"at","refresh_token":"rt","token_type":"Bearer","expires_in":3600,"scope":"read write"}`))
+	}))
+	defer server.Close()
+
+	now := time.Date(2020, 1, 1, 0, 0, 0, 0, time.UTC)
+	cfg := Config{ClientID: "c", TokenEndpoint: server.URL}
+	tok, err := ExchangeCode(context.Background(), server.Client(), cfg, "code", "verifier", "http://127.0.0.1/cb", func() time.Time { return now })
+	if err != nil {
+		t.Fatalf("ExchangeCode: %v", err)
+	}
+	if tok.AccessToken != "at" || tok.RefreshToken != "rt" || tok.TokenType != "Bearer" {
+		t.Fatalf("token = %+v", tok)
+	}
+	if !tok.ExpiresAt.Equal(now.Add(time.Hour)) {
+		t.Fatalf("expiresAt = %v, want now+1h", tok.ExpiresAt)
+	}
+	if strings.Join(tok.Scopes, " ") != "read write" {
+		t.Fatalf("scopes = %v", tok.Scopes)
+	}
+}
+
+func TestExchangeCodeErrorRedactsBody(t *testing.T) {
+	// The error body contains a stray access_token-looking field; it must NOT
+	// surface in the returned error (only error/error_description do).
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusBadRequest)
+		_, _ = w.Write([]byte(`{"error":"invalid_grant","error_description":"bad code","access_token":"SECRET-LEAK"}`))
+	}))
+	defer server.Close()
+	cfg := Config{ClientID: "c", TokenEndpoint: server.URL}
+	_, err := ExchangeCode(context.Background(), server.Client(), cfg, "code", "v", "http://127.0.0.1/cb", nil)
+	if err == nil {
+		t.Fatal("expected error")
+	}
+	if !strings.Contains(err.Error(), "invalid_grant") || !strings.Contains(err.Error(), "bad code") {
+		t.Fatalf("error should carry error/description, got %q", err.Error())
+	}
+	if strings.Contains(err.Error(), "SECRET-LEAK") {
+		t.Fatalf("error leaked raw body token material: %q", err.Error())
+	}
+}
+
+func TestPostTokenRefusesInsecureEndpoint(t *testing.T) {
+	_, err := PostToken(context.Background(), http.DefaultClient, "http://auth.example.com/token", url.Values{}, Token{}, nil)
+	if !errors.Is(err, ErrInsecureTokenEndpoint) {
+		t.Fatalf("err = %v, want ErrInsecureTokenEndpoint", err)
+	}
+}
+
+func TestRefreshNoToken(t *testing.T) {
+	_, err := Refresh(context.Background(), http.DefaultClient, Config{TokenEndpoint: "https://a/token"}, Token{}, nil)
+	if !errors.Is(err, ErrNoRefreshToken) {
+		t.Fatalf("err = %v, want ErrNoRefreshToken", err)
+	}
+}
+
+func TestRefreshPreservesRefreshTokenWhenOmitted(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write([]byte(`{"access_token":"new-at","expires_in":3600}`)) // no refresh_token in response
+	}))
+	defer server.Close()
+	cfg := Config{ClientID: "c", TokenEndpoint: server.URL}
+	tok, err := Refresh(context.Background(), server.Client(), cfg, Token{RefreshToken: "keep-me"}, nil)
+	if err != nil {
+		t.Fatalf("Refresh: %v", err)
+	}
+	if tok.AccessToken != "new-at" || tok.RefreshToken != "keep-me" {
+		t.Fatalf("refresh should preserve old refresh token: %+v", tok)
+	}
+}

internal/oauth/lock.go

@@ -0,0 +1,74 @@
+package oauth
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync/atomic"
+	"time"
+)
+
+const (
+	fileLockTimeout    = 5 * time.Second
+	fileLockStaleAfter = 30 * time.Second
+)
+
+var lockSeq atomic.Uint64
+
+// acquireFileLock takes a cross-process exclusive lock by creating lockPath with
+// O_EXCL. It retries with a short backoff until a timeout, breaking a lock whose
+// file is older than fileLockStaleAfter (so a crashed holder cannot deadlock the
+// store). Release is ownership-aware: it removes the lock only if it still holds
+// our token, so a stale-broken holder cannot delete a newer holder's lock.
+func acquireFileLock(lockPath string, now func() time.Time) (func(), error) {
+	if now == nil {
+		now = time.Now
+	}
+	if err := os.MkdirAll(filepath.Dir(lockPath), 0o700); err != nil {
+		return nil, err
+	}
+	token := fmt.Sprintf("%d-%d-%d", os.Getpid(), now().UnixNano(), lockSeq.Add(1))
+	deadline := now().Add(fileLockTimeout)
+	for {
+		f, err := os.OpenFile(lockPath, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
+		if err == nil {
+			// A partial/failed write would leave a lock file without our token, so
+			// the releaser below could never delete it — stranding the lock for
+			// other processes. Fail closed: remove the file and surface the error.
+			if _, werr := f.WriteString(token); werr != nil {
+				_ = f.Close()
+				_ = os.Remove(lockPath)
+				return nil, fmt.Errorf("oauth: write token lock: %w", werr)
+			}
+			if cerr := f.Close(); cerr != nil {
+				_ = os.Remove(lockPath)
+				return nil, fmt.Errorf("oauth: close token lock: %w", cerr)
+			}
+			var released bool
+			return func() {
+				if released {
+					return
+				}
+				released = true
+				if data, rerr := os.ReadFile(lockPath); rerr == nil && string(data) == token {
+					_ = os.Remove(lockPath)
+				}
+			}, nil
+		}
+		if !errors.Is(err, os.ErrExist) {
+			return nil, fmt.Errorf("oauth: acquire token lock: %w", err)
+		}
+		if info, statErr := os.Stat(lockPath); statErr == nil && time.Since(info.ModTime()) > fileLockStaleAfter {
+			stale, _ := os.ReadFile(lockPath)
+			if data, rerr := os.ReadFile(lockPath); rerr == nil && string(data) == string(stale) {
+				_ = os.Remove(lockPath)
+			}
+			continue
+		}
+		if now().After(deadline) {
+			return nil, fmt.Errorf("oauth: timed out acquiring token lock %s", filepath.Base(lockPath))
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+}

internal/oauth/loopback.go

@@ -0,0 +1,112 @@
+package oauth
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+// LoopbackListener is a single-use loopback HTTP server that captures an OAuth
+// redirect (?code=&state=) on 127.0.0.1 only: bind an OS-assigned loopback port,
+// verify the CSRF state, hand back the code, then close.
+type LoopbackListener struct {
+	listener net.Listener
+	state    string
+	result   chan callbackResult
+	server   *http.Server
+}
+
+type callbackResult struct {
+	code string
+	err  error
+}
+
+// NewLoopbackListener binds 127.0.0.1:0 (loopback only, OS-assigned port) and
+// begins serving. state is the CSRF value the callback must echo back. Call
+// RedirectURI to build the redirect_uri, then Wait for the code. Always Close.
+func NewLoopbackListener(state string) (*LoopbackListener, error) {
+	// Refuse an empty state: the callback check compares the query's state to this
+	// value, so an empty state would match a callback carrying no state at all,
+	// defeating CSRF protection (fail closed).
+	if strings.TrimSpace(state) == "" {
+		return nil, errors.New("oauth: loopback listener requires a non-empty CSRF state")
+	}
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		return nil, fmt.Errorf("oauth: start loopback redirect listener: %w", err)
+	}
+	l := &LoopbackListener{
+		listener: ln,
+		state:    state,
+		result:   make(chan callbackResult, 1),
+	}
+	l.server = &http.Server{Handler: http.HandlerFunc(l.handle)}
+	go func() { _ = l.server.Serve(ln) }()
+	return l, nil
+}
+
+// RedirectURI returns the http://127.0.0.1:<port>/callback redirect URI.
+func (l *LoopbackListener) RedirectURI() string {
+	return fmt.Sprintf("http://%s/callback", l.listener.Addr().String())
+}
+
+func (l *LoopbackListener) handle(w http.ResponseWriter, r *http.Request) {
+	if r.URL.Path != "/callback" {
+		http.NotFound(w, r)
+		return
+	}
+	code, err := parseCallback(r.URL.Query(), l.state)
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		_, _ = io.WriteString(w, "Authorization failed. You may close this window.")
+	} else {
+		_, _ = io.WriteString(w, "Authorization complete. You may close this window.")
+	}
+	select {
+	case l.result <- callbackResult{code: code, err: err}:
+	default:
+	}
+}
+
+// Wait blocks until the callback arrives or ctx is done, returning the
+// authorization code.
+func (l *LoopbackListener) Wait(ctx context.Context) (string, error) {
+	select {
+	case res := <-l.result:
+		return res.code, res.err
+	case <-ctx.Done():
+		return "", fmt.Errorf("oauth: timed out waiting for authorization callback: %w", ctx.Err())
+	}
+}
+
+// Close shuts the listener down (bounded), idempotent.
+func (l *LoopbackListener) Close() {
+	shutdownCtx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+	_ = l.server.Shutdown(shutdownCtx)
+}
+
+// parseCallback validates the redirect query and returns the authorization code,
+// rejecting a mismatched state (CSRF) and surfacing provider errors.
+func parseCallback(values url.Values, wantState string) (string, error) {
+	if got := values.Get("state"); got != wantState {
+		return "", ErrStateMismatch
+	}
+	if providerErr := strings.TrimSpace(values.Get("error")); providerErr != "" {
+		if desc := strings.TrimSpace(values.Get("error_description")); desc != "" {
+			return "", fmt.Errorf("oauth: authorization server returned error %q: %s", providerErr, desc)
+		}
+		return "", fmt.Errorf("oauth: authorization server returned error %q", providerErr)
+	}
+	code := strings.TrimSpace(values.Get("code"))
+	if code == "" {
+		return "", errors.New("oauth: callback missing authorization code")
+	}
+	return code, nil
+}

internal/oauth/loopback_test.go

@@ -0,0 +1,86 @@
+package oauth
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestLoopbackCapturesCode(t *testing.T) {
+	l, err := NewLoopbackListener("the-state")
+	if err != nil {
+		t.Fatalf("NewLoopbackListener: %v", err)
+	}
+	defer l.Close()
+	if !strings.HasPrefix(l.RedirectURI(), "http://127.0.0.1:") {
+		t.Fatalf("redirect URI not loopback: %q", l.RedirectURI())
+	}
+	go func() {
+		_, _ = http.Get(l.RedirectURI() + "?code=auth-code&state=the-state")
+	}()
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	code, err := l.Wait(ctx)
+	if err != nil {
+		t.Fatalf("Wait: %v", err)
+	}
+	if code != "auth-code" {
+		t.Fatalf("code = %q, want auth-code", code)
+	}
+}
+
+func TestNewLoopbackListenerRejectsEmptyState(t *testing.T) {
+	if _, err := NewLoopbackListener("   "); err == nil {
+		t.Fatal("an empty CSRF state must be rejected (fail closed)")
+	}
+}
+
+func TestLoopbackRejectsStateMismatch(t *testing.T) {
+	l, err := NewLoopbackListener("expected-state")
+	if err != nil {
+		t.Fatalf("NewLoopbackListener: %v", err)
+	}
+	defer l.Close()
+	go func() {
+		_, _ = http.Get(l.RedirectURI() + "?code=x&state=WRONG")
+	}()
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	_, err = l.Wait(ctx)
+	if !errors.Is(err, ErrStateMismatch) {
+		t.Fatalf("Wait err = %v, want ErrStateMismatch", err)
+	}
+}
+
+func TestLoopbackTimesOut(t *testing.T) {
+	l, err := NewLoopbackListener("s")
+	if err != nil {
+		t.Fatalf("NewLoopbackListener: %v", err)
+	}
+	defer l.Close()
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Millisecond)
+	defer cancel()
+	if _, err := l.Wait(ctx); err == nil {
+		t.Fatal("Wait should time out cleanly")
+	}
+}
+
+func TestLoopbackProviderError(t *testing.T) {
+	l, err := NewLoopbackListener("s")
+	if err != nil {
+		t.Fatalf("NewLoopbackListener: %v", err)
+	}
+	defer l.Close()
+	go func() {
+		_, _ = http.Get(l.RedirectURI() + "?error=access_denied&error_description=nope&state=s")
+	}()
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	_, err = l.Wait(ctx)
+	if err == nil || !strings.Contains(err.Error(), "access_denied") {
+		t.Fatalf("Wait err = %v, want provider error", err)
+	}
+}

internal/oauth/manager.go

@@ -0,0 +1,380 @@
+package oauth
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+)
+
+// ErrNoToken reports that no token is stored for a key. Callers (e.g. a request
+// path that prefers OAuth but can fall back to an API key) match it with
+// errors.Is to distinguish "not logged in" from a real refresh failure.
+var ErrNoToken = errors.New("oauth: no stored token")
+
+// defaultRefreshBuffer refreshes a token this long before its hard expiry.
+const defaultRefreshBuffer = 60 * time.Second
+
+const oidcWellKnownPath = "/.well-known/openid-configuration"
+
+// Manager ties the token store, provider registry, and HTTP client together to
+// run logins and serve fresh access tokens. It is the high-level entrypoint the
+// CLI and request paths use.
+type Manager struct {
+	store    *Store
+	registry *Registry
+	client   *http.Client
+	env      map[string]string
+	now      func() time.Time
+	buffer   time.Duration
+	out      io.Writer
+	// openBrowser is invoked with the authorization URL for loopback logins.
+	// Tests inject a function that drives the loopback redirect.
+	openBrowser func(authURL string) error
+}
+
+// ManagerOptions configures a Manager.
+type ManagerOptions struct {
+	Store         *Store
+	Registry      *Registry
+	HTTPClient    *http.Client
+	Env           map[string]string
+	Now           func() time.Time
+	RefreshBuffer time.Duration
+	Out           io.Writer
+	OpenBrowser   func(authURL string) error
+}
+
+// NewManager builds a Manager, filling defaults.
+func NewManager(opts ManagerOptions) (*Manager, error) {
+	if opts.Store == nil {
+		return nil, fmt.Errorf("oauth: manager requires a store")
+	}
+	registry := opts.Registry
+	if registry == nil {
+		registry = NewRegistry()
+	}
+	client := opts.HTTPClient
+	if client == nil {
+		client = http.DefaultClient
+	}
+	now := opts.Now
+	if now == nil {
+		now = time.Now
+	}
+	buffer := opts.RefreshBuffer
+	if buffer <= 0 {
+		buffer = defaultRefreshBuffer
+	}
+	out := opts.Out
+	if out == nil {
+		out = io.Discard
+	}
+	open := opts.OpenBrowser
+	if open == nil {
+		open = func(string) error { return nil }
+	}
+	return &Manager{
+		store: opts.Store, registry: registry, client: client,
+		env: opts.Env, now: now, buffer: buffer, out: out, openBrowser: open,
+	}, nil
+}
+
+// LoginOptions configures a single provider login.
+type LoginOptions struct {
+	Provider    string
+	Device      bool          // force device-code flow
+	ExtraScopes []string      // appended to the provider's scopes
+	Timeout     time.Duration // bounds the whole interactive login
+}
+
+// Login runs the provider login (loopback by default, device-code when
+// requested or when the provider only supports device), stores the token under
+// "provider:<name>", and returns a redaction-safe status.
+func (m *Manager) Login(ctx context.Context, opts LoginOptions) (Status, error) {
+	cfg, flow, err := m.registry.ResolveConfig(opts.Provider, m.env)
+	if err != nil {
+		return Status{}, err
+	}
+	if len(opts.ExtraScopes) > 0 {
+		cfg.Scopes = append(append([]string{}, cfg.Scopes...), opts.ExtraScopes...)
+	}
+	timeout := opts.Timeout
+	if timeout <= 0 {
+		timeout = 5 * time.Minute
+	}
+	loginCtx, cancel := context.WithTimeout(ctx, timeout)
+	defer cancel()
+
+	cfg, err = m.resolveEndpoints(loginCtx, cfg)
+	if err != nil {
+		return Status{}, err
+	}
+
+	useDevice := opts.Device || flow == FlowDevice
+	var token Token
+	if useDevice {
+		token, err = m.loginDevice(loginCtx, cfg)
+	} else {
+		token, err = m.loginLoopback(loginCtx, cfg)
+	}
+	if err != nil {
+		return Status{}, err
+	}
+
+	key := ProviderKey(opts.Provider)
+	if err := m.store.Save(key, token); err != nil {
+		return Status{}, err
+	}
+	return m.statusFor(key)
+}
+
+// PrepareDeviceLogin resolves the provider config and requests an RFC 8628
+// device code, returning the user-facing DeviceAuth (verification URI + user
+// code) and the resolved config. It is split from the token poll
+// (CompleteDeviceLogin) so a UI can display the code to the user while waiting
+// for authorization. The CLI's monolithic Login(Device:true) is unaffected.
+func (m *Manager) PrepareDeviceLogin(ctx context.Context, opts LoginOptions) (DeviceAuth, Config, error) {
+	cfg, _, err := m.registry.ResolveConfig(opts.Provider, m.env)
+	if err != nil {
+		return DeviceAuth{}, Config{}, err
+	}
+	if len(opts.ExtraScopes) > 0 {
+		cfg.Scopes = append(append([]string{}, cfg.Scopes...), opts.ExtraScopes...)
+	}
+	// Self-bound the network prepare (endpoint discovery + device-code request) the
+	// same way Login does, so a caller that hands in an unbounded context still gets
+	// the timeout guarantee instead of a hang.
+	timeout := opts.Timeout
+	if timeout <= 0 {
+		timeout = 5 * time.Minute
+	}
+	prepCtx, cancel := context.WithTimeout(ctx, timeout)
+	defer cancel()
+	cfg, err = m.resolveEndpoints(prepCtx, cfg)
+	if err != nil {
+		return DeviceAuth{}, Config{}, err
+	}
+	auth, err := RequestDeviceCode(prepCtx, m.client, cfg, m.now)
+	if err != nil {
+		return DeviceAuth{}, Config{}, err
+	}
+	return auth, cfg, nil
+}
+
+// CompleteDeviceLogin polls for the token authorized via PrepareDeviceLogin and
+// stores it under "provider:<name>", returning a redaction-safe status. Pass the
+// cfg and auth returned by PrepareDeviceLogin.
+func (m *Manager) CompleteDeviceLogin(ctx context.Context, provider string, cfg Config, auth DeviceAuth) (Status, error) {
+	// Bound the poll by the device code's own expiry so an unbounded caller context
+	// cannot leave an in-flight request hanging past the code's lifetime. PollDeviceToken
+	// re-checks ExpiresAt between polls; the deadline also caps each individual request.
+	if !auth.ExpiresAt.IsZero() {
+		var cancel context.CancelFunc
+		ctx, cancel = context.WithDeadline(ctx, auth.ExpiresAt)
+		defer cancel()
+	}
+	token, err := PollDeviceToken(ctx, m.client, cfg, auth, m.now)
+	if err != nil {
+		return Status{}, err
+	}
+	key := ProviderKey(provider)
+	if err := m.store.Save(key, token); err != nil {
+		return Status{}, err
+	}
+	return m.statusFor(key)
+}
+
+// resolveEndpoints fills missing authorize/token/device endpoints from issuer
+// discovery (RFC 8414 then OIDC), leaving any explicitly-pinned endpoint intact.
+func (m *Manager) resolveEndpoints(ctx context.Context, cfg Config) (Config, error) {
+	if trimmed(cfg.IssuerURL) == "" {
+		return cfg, nil
+	}
+	if cfg.AuthorizationEndpoint != "" && cfg.TokenEndpoint != "" && cfg.DeviceAuthorizationEndpoint != "" {
+		return cfg, nil
+	}
+	// Discovery is best-effort: a failure is non-fatal because pinned endpoints
+	// may already be sufficient for the chosen flow. Only merge on success (and
+	// never return from the error branch, which would trip the nilerr linter).
+	if meta, err := m.discover(ctx, cfg.IssuerURL); err == nil {
+		if cfg.AuthorizationEndpoint == "" {
+			cfg.AuthorizationEndpoint = meta.AuthorizationEndpoint
+		}
+		if cfg.TokenEndpoint == "" {
+			cfg.TokenEndpoint = meta.TokenEndpoint
+		}
+		if cfg.DeviceAuthorizationEndpoint == "" {
+			cfg.DeviceAuthorizationEndpoint = meta.DeviceAuthorizationEndpoint
+		}
+	}
+	return cfg, nil
+}
+
+// discover tries the OAuth (RFC 8414) well-known path, then the OIDC
+// openid-configuration path (some issuers publish only the latter).
+func (m *Manager) discover(ctx context.Context, issuer string) (ServerMetadata, error) {
+	meta, err := DiscoverAuthorizationServer(ctx, m.client, issuer)
+	if err == nil && (meta.AuthorizationEndpoint != "" || meta.TokenEndpoint != "") {
+		return meta, nil
+	}
+	oidcURL := strings.TrimRight(strings.TrimSpace(issuer), "/") + oidcWellKnownPath
+	return fetchMetadata(ctx, m.client, oidcURL)
+}
+
+func (m *Manager) loginLoopback(ctx context.Context, cfg Config) (Token, error) {
+	if trimmed(cfg.AuthorizationEndpoint) == "" {
+		return Token{}, fmt.Errorf("oauth: no authorization endpoint (set the authorize URL or a discoverable issuer)")
+	}
+	state, err := NewState()
+	if err != nil {
+		return Token{}, err
+	}
+	pkce, err := NewPKCE()
+	if err != nil {
+		return Token{}, err
+	}
+	listener, err := NewLoopbackListener(state)
+	if err != nil {
+		return Token{}, err
+	}
+	defer listener.Close()
+	redirectURI := listener.RedirectURI()
+	authURL, err := BuildAuthorizationURL(cfg, pkce, state, redirectURI, nil)
+	if err != nil {
+		return Token{}, err
+	}
+	fmt.Fprintf(m.out, "Open this URL to authorize:\n  %s\n", authURL)
+	if err := m.openBrowser(authURL); err != nil {
+		return Token{}, fmt.Errorf("oauth: open authorization URL: %w", err)
+	}
+	code, err := listener.Wait(ctx)
+	if err != nil {
+		return Token{}, err
+	}
+	return ExchangeCode(ctx, m.client, cfg, code, pkce.Verifier, redirectURI, m.now)
+}
+
+func (m *Manager) loginDevice(ctx context.Context, cfg Config) (Token, error) {
+	auth, err := RequestDeviceCode(ctx, m.client, cfg, m.now)
+	if err != nil {
+		return Token{}, err
+	}
+	target := auth.VerificationURIComplete
+	if target == "" {
+		target = auth.VerificationURI
+	}
+	// user_code is meant to be displayed to the user; it is not a secret.
+	fmt.Fprintf(m.out, "To authorize, visit:\n  %s\nand enter code: %s\n", target, auth.UserCode)
+	return PollDeviceToken(ctx, m.client, cfg, auth, m.now)
+}
+
+// GetFresh returns a valid access token for key, refreshing on-demand if the
+// stored token is expired or within the refresh buffer. Mirrors
+// checkAndRefreshOAuthTokenIfNeeded.
+func (m *Manager) GetFresh(ctx context.Context, key string) (string, error) {
+	token, err := m.loadToken(key)
+	if err != nil {
+		return "", err
+	}
+	// A still-valid token is returned without resolving the provider config, so a
+	// readable login never depends on config that is only needed to refresh (e.g.
+	// an opt-in preset client_id). Only an actual refresh resolves endpoints.
+	if !token.NeedsRefresh(m.now(), m.buffer) {
+		return token.AccessToken, nil
+	}
+	cfg, err := m.resolveConfigForKey(ctx, key)
+	if err != nil {
+		return "", err
+	}
+	return m.refreshAndSave(ctx, key, cfg, token)
+}
+
+// Handle401 forces a refresh after an upstream 401, returning the new access
+// token. Mirrors handleOAuth401Error.
+func (m *Manager) Handle401(ctx context.Context, key string) (string, error) {
+	token, err := m.loadToken(key)
+	if err != nil {
+		return "", err
+	}
+	cfg, err := m.resolveConfigForKey(ctx, key)
+	if err != nil {
+		return "", err
+	}
+	return m.refreshAndSave(ctx, key, cfg, token)
+}
+
+func (m *Manager) refreshAndSave(ctx context.Context, key string, cfg Config, current Token) (string, error) {
+	refreshed, err := Refresh(ctx, m.client, cfg, current, m.now)
+	if err != nil {
+		return "", err
+	}
+	if err := m.store.Save(key, refreshed); err != nil {
+		return "", err
+	}
+	return refreshed.AccessToken, nil
+}
+
+// loadToken loads a stored token for key without resolving any provider config,
+// so reading a still-valid login never depends on refresh-only configuration.
+func (m *Manager) loadToken(key string) (Token, error) {
+	if err := ValidateKey(key); err != nil {
+		return Token{}, err
+	}
+	token, ok, err := m.store.Load(key)
+	if err != nil {
+		return Token{}, err
+	}
+	if !ok {
+		return Token{}, fmt.Errorf("%w for %q", ErrNoToken, key)
+	}
+	return token, nil
+}
+
+// resolveConfigForKey resolves the provider OAuth config for a provider-token key.
+// It is only needed to refresh a token (the endpoints + client identity), not to
+// read one.
+func (m *Manager) resolveConfigForKey(ctx context.Context, key string) (Config, error) {
+	name := strings.TrimPrefix(key, KeyPrefixProvider)
+	if name == key {
+		return Config{}, fmt.Errorf("oauth: refresh is only supported for provider tokens (got %q)", key)
+	}
+	cfg, _, err := m.registry.ResolveConfig(name, m.env)
+	if err != nil {
+		return Config{}, err
+	}
+	// Fill any missing token/authorize/device endpoints from issuer discovery so a
+	// provider configured with only ZERO_OAUTH_<NAME>_ISSUER_URL can still refresh
+	// (refreshAndSave requires the token endpoint).
+	cfg, err = m.resolveEndpoints(ctx, cfg)
+	if err != nil {
+		return Config{}, err
+	}
+	return cfg, nil
+}
+
+// Logout removes a provider's stored token, reporting whether one was present.
+func (m *Manager) Logout(name string) (bool, error) {
+	return m.store.Delete(ProviderKey(name))
+}
+
+// StatusAll returns the status of every provider login.
+func (m *Manager) StatusAll() ([]Status, error) {
+	return m.store.Status(KeyPrefixProvider)
+}
+
+func (m *Manager) statusFor(key string) (Status, error) {
+	statuses, err := m.store.Status(KeyPrefixProvider)
+	if err != nil {
+		return Status{}, err
+	}
+	for _, st := range statuses {
+		if st.Key == key {
+			return st, nil
+		}
+	}
+	return Status{Key: key}, nil
+}

internal/oauth/manager_test.go

@@ -0,0 +1,252 @@
+package oauth
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"path/filepath"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+// fakeProvider is an httptest server that plays a token + device endpoint.
+type fakeProvider struct {
+	server    *httptest.Server
+	tokenHits atomic.Int32
+}
+
+func newFakeProvider(t *testing.T, tokenJSON string) *fakeProvider {
+	t.Helper()
+	fp := &fakeProvider{}
+	mux := http.NewServeMux()
+	mux.HandleFunc("/token", func(w http.ResponseWriter, _ *http.Request) {
+		fp.tokenHits.Add(1)
+		_, _ = io.WriteString(w, tokenJSON)
+	})
+	mux.HandleFunc("/device", func(w http.ResponseWriter, _ *http.Request) {
+		// Approve immediately on poll; short interval so the test is fast.
+		_, _ = io.WriteString(w, `{"device_code":"dc","user_code":"U-1","verification_uri":"https://example/dev","expires_in":600,"interval":1}`)
+	})
+	fp.server = httptest.NewServer(mux)
+	t.Cleanup(fp.server.Close)
+	return fp
+}
+
+func managerFor(t *testing.T, env map[string]string, openBrowser func(string) error) *Manager {
+	t.Helper()
+	store, err := NewStore(StoreOptions{FilePath: filepath.Join(t.TempDir(), "tok.json")})
+	if err != nil {
+		t.Fatalf("NewStore: %v", err)
+	}
+	m, err := NewManager(ManagerOptions{
+		Store:       store,
+		Env:         env,
+		OpenBrowser: openBrowser,
+	})
+	if err != nil {
+		t.Fatalf("NewManager: %v", err)
+	}
+	return m
+}
+
+func TestManagerLoginLoopback(t *testing.T) {
+	fp := newFakeProvider(t, `{"access_token":"at","refresh_token":"rt","token_type":"Bearer","expires_in":3600}`)
+	env := map[string]string{
+		"ZERO_OAUTH_DEMO_CLIENT_ID":     "client",
+		"ZERO_OAUTH_DEMO_AUTHORIZE_URL": "https://auth.example.com/authorize",
+		"ZERO_OAUTH_DEMO_TOKEN_URL":     fp.server.URL + "/token",
+	}
+	// The fake browser drives the loopback redirect with the captured state.
+	openBrowser := func(authURL string) error {
+		u, err := url.Parse(authURL)
+		if err != nil {
+			return err
+		}
+		redirect := u.Query().Get("redirect_uri")
+		state := u.Query().Get("state")
+		_, err = http.Get(redirect + "?code=the-code&state=" + url.QueryEscape(state))
+		return err
+	}
+	m := managerFor(t, env, openBrowser)
+
+	status, err := m.Login(context.Background(), LoginOptions{Provider: "demo"})
+	if err != nil {
+		t.Fatalf("Login: %v", err)
+	}
+	if !status.HasToken || status.Key != ProviderKey("demo") {
+		t.Fatalf("status = %+v", status)
+	}
+	// The token is persisted and GetFresh returns it without a needless refresh.
+	access, err := m.GetFresh(context.Background(), ProviderKey("demo"))
+	if err != nil {
+		t.Fatalf("GetFresh: %v", err)
+	}
+	if access != "at" {
+		t.Fatalf("access = %q, want at", access)
+	}
+}
+
+func TestManagerLoginDevice(t *testing.T) {
+	fp := newFakeProvider(t, `{"access_token":"dev-at","token_type":"Bearer","expires_in":3600}`)
+	env := map[string]string{
+		"ZERO_OAUTH_DEMODEV_CLIENT_ID":  "client",
+		"ZERO_OAUTH_DEMODEV_TOKEN_URL":  fp.server.URL + "/token",
+		"ZERO_OAUTH_DEMODEV_DEVICE_URL": fp.server.URL + "/device",
+	}
+	m := managerFor(t, env, nil)
+	status, err := m.Login(context.Background(), LoginOptions{Provider: "demodev", Device: true})
+	if err != nil {
+		t.Fatalf("device Login: %v", err)
+	}
+	if !status.HasToken {
+		t.Fatalf("device status = %+v", status)
+	}
+}
+
+func TestManagerPrepareAndCompleteDeviceLogin(t *testing.T) {
+	fp := newFakeProvider(t, `{"access_token":"two-phase-at","token_type":"Bearer","expires_in":3600}`)
+	env := map[string]string{
+		"ZERO_OAUTH_DEMO2_CLIENT_ID":  "client",
+		"ZERO_OAUTH_DEMO2_TOKEN_URL":  fp.server.URL + "/token",
+		"ZERO_OAUTH_DEMO2_DEVICE_URL": fp.server.URL + "/device",
+	}
+	m := managerFor(t, env, nil)
+
+	// Phase 1: request the device code (what the UI displays to the user).
+	auth, cfg, err := m.PrepareDeviceLogin(context.Background(), LoginOptions{Provider: "demo2"})
+	if err != nil {
+		t.Fatalf("PrepareDeviceLogin: %v", err)
+	}
+	if auth.UserCode != "U-1" || auth.VerificationURI == "" {
+		t.Fatalf("device auth missing user code/uri: %+v", auth)
+	}
+
+	// Phase 2: poll for the token and persist it.
+	status, err := m.CompleteDeviceLogin(context.Background(), "demo2", cfg, auth)
+	if err != nil {
+		t.Fatalf("CompleteDeviceLogin: %v", err)
+	}
+	if !status.HasToken || status.Key != ProviderKey("demo2") {
+		t.Fatalf("status = %+v", status)
+	}
+	access, err := m.GetFresh(context.Background(), ProviderKey("demo2"))
+	if err != nil {
+		t.Fatalf("GetFresh: %v", err)
+	}
+	if access != "two-phase-at" {
+		t.Fatalf("access = %q, want two-phase-at", access)
+	}
+}
+
+// A provider configured with only an issuer URL (no TOKEN_URL) must still be
+// refreshable: GetFresh resolves the token endpoint via discovery before
+// refreshing. Guards resolveConfigForKey calling resolveEndpoints.
+func TestManagerGetFreshDiscoversIssuerEndpoints(t *testing.T) {
+	var tokenHits int32
+	mux := http.NewServeMux()
+	server := httptest.NewServer(mux)
+	defer server.Close()
+	mux.HandleFunc("/.well-known/oauth-authorization-server", func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = io.WriteString(w, `{"issuer":"`+server.URL+`","token_endpoint":"`+server.URL+`/token","authorization_endpoint":"`+server.URL+`/authorize"}`)
+	})
+	mux.HandleFunc("/token", func(w http.ResponseWriter, _ *http.Request) {
+		atomic.AddInt32(&tokenHits, 1)
+		_, _ = io.WriteString(w, `{"access_token":"refreshed-at","token_type":"Bearer","expires_in":3600}`)
+	})
+	env := map[string]string{
+		"ZERO_OAUTH_ISSUERONLY_CLIENT_ID":  "client",
+		"ZERO_OAUTH_ISSUERONLY_ISSUER_URL": server.URL, // no TOKEN_URL → discovered
+	}
+	m := managerFor(t, env, nil)
+	if err := m.store.Save(ProviderKey("issueronly"), Token{AccessToken: "stale", RefreshToken: "rt", ExpiresAt: time.Now().Add(-time.Hour)}); err != nil {
+		t.Fatalf("seed: %v", err)
+	}
+	got, err := m.GetFresh(context.Background(), ProviderKey("issueronly"))
+	if err != nil {
+		t.Fatalf("GetFresh (issuer-only) must discover the token endpoint and refresh: %v", err)
+	}
+	if got != "refreshed-at" {
+		t.Fatalf("access = %q, want refreshed-at", got)
+	}
+	if atomic.LoadInt32(&tokenHits) == 0 {
+		t.Fatal("token endpoint never hit — discovery/refresh did not run")
+	}
+}
+
+func TestManagerGetFreshRefreshesExpired(t *testing.T) {
+	fp := newFakeProvider(t, `{"access_token":"fresh-at","expires_in":3600}`)
+	env := map[string]string{
+		"ZERO_OAUTH_DEMO_CLIENT_ID": "client",
+		"ZERO_OAUTH_DEMO_TOKEN_URL": fp.server.URL + "/token",
+	}
+	m := managerFor(t, env, nil)
+	// Seed an expired token with a refresh token.
+	if err := m.store.Save(ProviderKey("demo"), Token{AccessToken: "stale", RefreshToken: "rt", ExpiresAt: time.Now().Add(-time.Hour)}); err != nil {
+		t.Fatalf("seed: %v", err)
+	}
+	access, err := m.GetFresh(context.Background(), ProviderKey("demo"))
+	if err != nil {
+		t.Fatalf("GetFresh: %v", err)
+	}
+	if access != "fresh-at" {
+		t.Fatalf("access = %q, want fresh-at (refreshed)", access)
+	}
+	if fp.tokenHits.Load() != 1 {
+		t.Fatalf("token endpoint hit %d times, want 1 refresh", fp.tokenHits.Load())
+	}
+	// The refreshed token is persisted.
+	stored, _, _ := m.store.Load(ProviderKey("demo"))
+	if stored.AccessToken != "fresh-at" {
+		t.Fatalf("stored token not updated: %+v", stored)
+	}
+}
+
+func TestManagerGetFreshSkipsValidToken(t *testing.T) {
+	fp := newFakeProvider(t, `{"access_token":"should-not-be-used"}`)
+	env := map[string]string{
+		"ZERO_OAUTH_DEMO_CLIENT_ID": "client",
+		"ZERO_OAUTH_DEMO_TOKEN_URL": fp.server.URL + "/token",
+	}
+	m := managerFor(t, env, nil)
+	_ = m.store.Save(ProviderKey("demo"), Token{AccessToken: "valid", RefreshToken: "rt", ExpiresAt: time.Now().Add(time.Hour)})
+	access, err := m.GetFresh(context.Background(), ProviderKey("demo"))
+	if err != nil {
+		t.Fatalf("GetFresh: %v", err)
+	}
+	if access != "valid" || fp.tokenHits.Load() != 0 {
+		t.Fatalf("a valid token must not be refreshed (access=%q hits=%d)", access, fp.tokenHits.Load())
+	}
+}
+
+func TestManagerHandle401ForcesRefresh(t *testing.T) {
+	fp := newFakeProvider(t, `{"access_token":"after-401"}`)
+	env := map[string]string{
+		"ZERO_OAUTH_DEMO_CLIENT_ID": "client",
+		"ZERO_OAUTH_DEMO_TOKEN_URL": fp.server.URL + "/token",
+	}
+	m := managerFor(t, env, nil)
+	// Token is still valid by clock, but Handle401 forces a refresh anyway.
+	_ = m.store.Save(ProviderKey("demo"), Token{AccessToken: "valid", RefreshToken: "rt", ExpiresAt: time.Now().Add(time.Hour)})
+	access, err := m.Handle401(context.Background(), ProviderKey("demo"))
+	if err != nil {
+		t.Fatalf("Handle401: %v", err)
+	}
+	if access != "after-401" || fp.tokenHits.Load() != 1 {
+		t.Fatalf("Handle401 must force a refresh (access=%q hits=%d)", access, fp.tokenHits.Load())
+	}
+}
+
+func TestManagerLogout(t *testing.T) {
+	m := managerFor(t, map[string]string{"ZERO_OAUTH_DEMO_CLIENT_ID": "c"}, nil)
+	_ = m.store.Save(ProviderKey("demo"), Token{AccessToken: "a"})
+	removed, err := m.Logout("demo")
+	if err != nil || !removed {
+		t.Fatalf("Logout = %v %v", removed, err)
+	}
+	if removed2, _ := m.Logout("demo"); removed2 {
+		t.Fatal("second logout should report nothing removed")
+	}
+}

internal/oauth/oauth.go

@@ -0,0 +1,97 @@
+// Package oauth is zero's reusable OAuth 2.0 engine. It generalizes the
+// authorization-code + PKCE flow that internal/mcp already uses for MCP servers
+// into a transport/identity-agnostic core, and adds the pieces provider login
+// needs: a device-authorization (RFC 8628) grant, a provider registry, a
+// namespaced + refreshing token store, and a proactive refresh scheduler.
+//
+// Security invariants (enforced throughout, never relaxed):
+//   - PKCE S256 is mandatory on every authorization-code flow; "plain" is refused.
+//   - A per-flow CSRF state is generated and verified on the callback.
+//   - The loopback callback server binds 127.0.0.1 only, on an OS-assigned port,
+//     serves a single request, then closes.
+//   - The token endpoint must be https (loopback exempt) before any credential is
+//     sent — see validateTokenEndpoint.
+//   - Tokens, codes, and verifiers are never logged; error bodies are redacted.
+//   - Token files are 0600, base-confined, and file-locked.
+//
+// This package holds NO vendor secrets: provider client IDs and endpoints come
+// from config/env by default, so no third-party OAuth client identity is used
+// unless the operator opts in. A small set of built-in presets (e.g. xAI's public
+// client) exists for convenience but is OFF by default and only consulted when
+// ZERO_OAUTH_ALLOW_PRESETS is set; env always overrides a preset.
+package oauth
+
+import (
+	"errors"
+	"strings"
+	"time"
+)
+
+// Token holds the credentials issued by an authorization server. The token
+// fields are sensitive: callers must never log them, and the store persists them
+// 0600. It mirrors the on-disk shape internal/mcp uses so the two stay
+// format-compatible.
+type Token struct {
+	AccessToken  string    `json:"access_token"`
+	RefreshToken string    `json:"refresh_token,omitempty"`
+	TokenType    string    `json:"token_type,omitempty"`
+	Scopes       []string  `json:"scopes,omitempty"`
+	ExpiresAt    time.Time `json:"expires_at,omitempty"`
+	// Account is an optional non-secret identifier (email / account id) shown in
+	// status output; never a credential.
+	Account string `json:"account,omitempty"`
+}
+
+// Expired reports whether the token has an expiry that is at or before now.
+// A zero ExpiresAt means "no known expiry" and is treated as not expired.
+func (t Token) Expired(now time.Time) bool {
+	return !t.ExpiresAt.IsZero() && !t.ExpiresAt.After(now)
+}
+
+// NeedsRefresh reports whether the token is expired or falls within buffer of
+// expiry (so a proactive/on-demand refresh should run). A token with no expiry
+// never needs a refresh on a timer.
+func (t Token) NeedsRefresh(now time.Time, buffer time.Duration) bool {
+	if t.ExpiresAt.IsZero() {
+		return false
+	}
+	return !t.ExpiresAt.After(now.Add(buffer))
+}
+
+// Config describes how to talk to one authorization server for a flow.
+// Endpoints may be discovered (RFC 8414) and overridden here.
+type Config struct {
+	ClientID     string
+	ClientSecret string
+	Scopes       []string
+
+	AuthorizationEndpoint       string
+	TokenEndpoint               string
+	DeviceAuthorizationEndpoint string
+	RegistrationEndpoint        string
+	// IssuerURL is the base for metadata discovery when endpoints are not set.
+	IssuerURL string
+
+	// ExtraAuthParams are appended to the authorization URL (e.g. login_hint).
+	ExtraAuthParams map[string]string
+}
+
+// Errors returned by the engine. Callers can match these with errors.Is.
+var (
+	// ErrPKCEDowngrade is returned if a flow is asked to use anything but S256.
+	ErrPKCEDowngrade = errors.New("oauth: PKCE S256 is mandatory; plain is refused")
+	// ErrStateMismatch is returned when the callback state does not match (CSRF).
+	ErrStateMismatch = errors.New("oauth: callback state mismatch; possible CSRF, login aborted")
+	// ErrInsecureTokenEndpoint is returned when a credential would be sent over a
+	// non-https, non-loopback endpoint.
+	ErrInsecureTokenEndpoint = errors.New("oauth: refusing to send credential to a non-https token endpoint")
+	// ErrNoRefreshToken is returned when a refresh is attempted without one.
+	ErrNoRefreshToken = errors.New("oauth: no refresh token available")
+	// ErrAuthorizationPending is the RFC 8628 "keep polling" signal.
+	ErrAuthorizationPending = errors.New("oauth: authorization pending")
+	// ErrSlowDown is the RFC 8628 "increase the poll interval" signal.
+	ErrSlowDown = errors.New("oauth: slow down")
+)
+
+// trimmed is a tiny helper used across the package.
+func trimmed(s string) string { return strings.TrimSpace(s) }

internal/oauth/pkce.go

@@ -0,0 +1,49 @@
+package oauth
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"fmt"
+)
+
+const (
+	// pkceVerifierBytes yields a 43-character base64url verifier — the minimum
+	// length the PKCE spec permits while remaining high-entropy.
+	pkceVerifierBytes = 32
+	stateBytes        = 32
+	// MethodS256 is the only code-challenge method this engine accepts.
+	MethodS256 = "S256"
+)
+
+// PKCE is a verifier/challenge pair for an authorization-code flow. The method
+// is always S256 (the engine refuses "plain").
+type PKCE struct {
+	Verifier  string
+	Challenge string
+	Method    string
+}
+
+// NewPKCE generates a high-entropy code verifier and its S256 challenge. It
+// matches internal/mcp's newPKCE byte-for-byte (RawURLEncoding of 32 random
+// bytes; challenge = base64url(SHA-256(verifier))) so the two engines are
+// interchangeable.
+func NewPKCE() (PKCE, error) {
+	raw := make([]byte, pkceVerifierBytes)
+	if _, err := rand.Read(raw); err != nil {
+		return PKCE{}, fmt.Errorf("oauth: generate PKCE verifier: %w", err)
+	}
+	verifier := base64.RawURLEncoding.EncodeToString(raw)
+	sum := sha256.Sum256([]byte(verifier))
+	challenge := base64.RawURLEncoding.EncodeToString(sum[:])
+	return PKCE{Verifier: verifier, Challenge: challenge, Method: MethodS256}, nil
+}
+
+// NewState generates a high-entropy CSRF state value.
+func NewState() (string, error) {
+	raw := make([]byte, stateBytes)
+	if _, err := rand.Read(raw); err != nil {
+		return "", fmt.Errorf("oauth: generate state: %w", err)
+	}
+	return base64.RawURLEncoding.EncodeToString(raw), nil
+}

internal/oauth/presets.go

@@ -0,0 +1,74 @@
+package oauth
+
+import "strings"
+
+// providerPreset is a baked-in default OAuth configuration for a well-known
+// provider. Every field is overridable per provider via ZERO_OAUTH_<NAME>_*
+// env vars (env wins). Only providers whose OAuth flow is verified to yield a
+// credential usable for model calls are listed here.
+type providerPreset struct {
+	ClientID                    string
+	ClientSecret                string
+	AuthorizationEndpoint       string
+	TokenEndpoint               string
+	DeviceAuthorizationEndpoint string
+	IssuerURL                   string
+	Scopes                      []string
+	Flow                        Flow
+}
+
+// builtinOAuthPresets maps a provider name to its default OAuth config.
+//
+// These presets are OFF by default and only consulted when the operator opts in
+// with ZERO_OAUTH_ALLOW_PRESETS (see presetsAllowed). A preset carries a
+// third-party OAuth client identity, and the engine keeps such identities out of
+// the default credential path (see the package doc) — opting in is an explicit
+// acknowledgement that the binary's preset client_id will be used when no
+// ZERO_OAUTH_<NAME>_* override is set.
+//
+// xAI (Grok): the client_id is a PUBLIC client (no secret) used by several Grok
+// CLIs; its access token is accepted directly as a bearer on api.x.ai/v1 (an
+// OpenAI-compatible endpoint), so no header/identity spoofing is involved.
+// CAVEATS: it is NOT formally documented by xAI as a public developer API and may
+// change without notice (override via ZERO_OAUTH_XAI_*), and using it requires a
+// SuperGrok / X Premium+ subscription. Pay-as-you-go users should use a console
+// API key instead.
+var builtinOAuthPresets = map[string]providerPreset{
+	"xai": {
+		ClientID:                    "b1a00492-073a-47ea-816f-4c329264a828",
+		AuthorizationEndpoint:       "https://auth.x.ai/oauth2/authorize",
+		TokenEndpoint:               "https://auth.x.ai/oauth2/token",
+		DeviceAuthorizationEndpoint: "https://auth.x.ai/oauth2/device/code",
+		IssuerURL:                   "https://auth.x.ai",
+		Scopes:                      []string{"openid", "profile", "email", "offline_access", "grok-cli:access", "api:access"},
+		Flow:                        FlowLoopback,
+	},
+}
+
+// lookupOAuthPreset returns the baked-in preset for a provider name (if any).
+func lookupOAuthPreset(name string) (providerPreset, bool) {
+	preset, ok := builtinOAuthPresets[strings.ToLower(strings.TrimSpace(name))]
+	return preset, ok
+}
+
+// presetsAllowed reports whether baked-in OAuth presets may supply defaults. They
+// are OFF unless the operator opts in with ZERO_OAUTH_ALLOW_PRESETS set to a
+// truthy value, keeping any third-party OAuth client identity out of the default
+// credential path (a preset client_id is only ever used after explicit opt-in).
+func presetsAllowed(env map[string]string) bool {
+	switch strings.ToLower(strings.TrimSpace(envValue(env, "ZERO_OAUTH_ALLOW_PRESETS"))) {
+	case "1", "true", "yes", "on":
+		return true
+	}
+	return false
+}
+
+// scopesOrPreset returns the env scopes (space-separated) when set, else the
+// preset's scopes.
+func scopesOrPreset(envScopes string, preset []string) []string {
+	if fields := strings.Fields(envScopes); len(fields) > 0 {
+		return fields
+	}
+	// Copy so a caller appending to cfg.Scopes can't mutate the shared preset slice.
+	return append([]string(nil), preset...)
+}

internal/oauth/presets_test.go

@@ -0,0 +1,95 @@
+package oauth
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestScopesOrPresetReturnsACopy(t *testing.T) {
+	preset := []string{"openid", "profile"}
+	got := scopesOrPreset("", preset)
+	if len(got) != 2 || got[0] != "openid" {
+		t.Fatalf("got %v, want the preset scopes", got)
+	}
+	// Mutating the result must not bleed into the shared preset slice.
+	got[0] = "MUTATED"
+	if preset[0] != "openid" {
+		t.Fatalf("scopesOrPreset aliased the shared preset slice: %v", preset)
+	}
+}
+
+func TestResolveConfigUsesXAIPreset(t *testing.T) {
+	r := NewRegistry()
+	// Presets are opt-in; with ZERO_OAUTH_ALLOW_PRESETS set and no other env vars
+	// the preset supplies everything.
+	cfg, flow, err := r.ResolveConfig("xai", map[string]string{"ZERO_OAUTH_ALLOW_PRESETS": "1"})
+	if err != nil {
+		t.Fatalf("ResolveConfig(xai): %v", err)
+	}
+	if cfg.ClientID != "b1a00492-073a-47ea-816f-4c329264a828" {
+		t.Fatalf("client_id = %q", cfg.ClientID)
+	}
+	if cfg.AuthorizationEndpoint != "https://auth.x.ai/oauth2/authorize" {
+		t.Fatalf("authorize = %q", cfg.AuthorizationEndpoint)
+	}
+	if cfg.TokenEndpoint != "https://auth.x.ai/oauth2/token" {
+		t.Fatalf("token = %q", cfg.TokenEndpoint)
+	}
+	if cfg.DeviceAuthorizationEndpoint != "https://auth.x.ai/oauth2/device/code" {
+		t.Fatalf("device = %q", cfg.DeviceAuthorizationEndpoint)
+	}
+	if flow != FlowLoopback {
+		t.Fatalf("flow = %q, want loopback", flow)
+	}
+	if len(cfg.Scopes) == 0 {
+		t.Fatal("preset scopes should be populated")
+	}
+}
+
+func TestResolveConfigEnvOverridesPreset(t *testing.T) {
+	r := NewRegistry()
+	env := map[string]string{
+		"ZERO_OAUTH_ALLOW_PRESETS": "1",
+		"ZERO_OAUTH_XAI_CLIENT_ID": "custom-id",
+		"ZERO_OAUTH_XAI_SCOPES":    "alpha beta",
+		"ZERO_OAUTH_XAI_FLOW":      "device",
+	}
+	cfg, flow, err := r.ResolveConfig("xai", env)
+	if err != nil {
+		t.Fatalf("ResolveConfig(xai, env): %v", err)
+	}
+	if cfg.ClientID != "custom-id" {
+		t.Fatalf("env should override client_id, got %q", cfg.ClientID)
+	}
+	if len(cfg.Scopes) != 2 || cfg.Scopes[0] != "alpha" {
+		t.Fatalf("env should override scopes, got %v", cfg.Scopes)
+	}
+	if flow != FlowDevice {
+		t.Fatalf("env should override flow, got %q", flow)
+	}
+	// A field not overridden still comes from the preset.
+	if cfg.TokenEndpoint != "https://auth.x.ai/oauth2/token" {
+		t.Fatalf("non-overridden token endpoint = %q", cfg.TokenEndpoint)
+	}
+}
+
+func TestResolveConfigNoPresetStillRequiresEnv(t *testing.T) {
+	r := NewRegistry()
+	if _, _, err := r.ResolveConfig("acme-no-preset", map[string]string{}); err == nil {
+		t.Fatal("a provider with neither preset nor env config should error")
+	}
+}
+
+// Without the opt-in flag the xAI preset must stay inert: no third-party client
+// identity is baked into the default credential path, and the error points the
+// user at the opt-in.
+func TestResolveConfigPresetInertWithoutOptIn(t *testing.T) {
+	r := NewRegistry()
+	_, _, err := r.ResolveConfig("xai", map[string]string{})
+	if err == nil {
+		t.Fatal("xai must not resolve from the preset unless ZERO_OAUTH_ALLOW_PRESETS is set")
+	}
+	if !strings.Contains(err.Error(), "ZERO_OAUTH_ALLOW_PRESETS") {
+		t.Fatalf("error should point at the opt-in, got: %v", err)
+	}
+}

internal/oauth/providers.go

@@ -0,0 +1,117 @@
+package oauth
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+// Flow selects how a provider delivers the authorization result.
+type Flow string
+
+const (
+	// FlowLoopback uses a 127.0.0.1 callback server (browser required).
+	FlowLoopback Flow = "loopback"
+	// FlowDevice uses the RFC 8628 device-code flow (headless/SSH).
+	FlowDevice Flow = "device"
+)
+
+// providerNamePattern bounds a provider name to a safe identifier that is also a
+// valid store-key segment.
+var providerNamePattern = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._-]{0,63}$`)
+
+// ValidateProviderName reports whether name is a safe provider identifier.
+func ValidateProviderName(name string) error {
+	if !providerNamePattern.MatchString(name) {
+		return fmt.Errorf("oauth: invalid provider name %q", name)
+	}
+	return nil
+}
+
+// Registry resolves a provider's Config from env/config. By default every provider
+// is defined entirely by the operator via ZERO_OAUTH_<NAME>_* variables, so no
+// third-party OAuth client identity is used. A small set of built-in presets
+// exists for convenience but stays inert unless the operator opts in with
+// ZERO_OAUTH_ALLOW_PRESETS (see presetsAllowed); env always overrides a preset.
+type Registry struct{}
+
+// NewRegistry returns the (stateless) env-driven registry.
+func NewRegistry() *Registry { return &Registry{} }
+
+// envKey builds the ZERO_OAUTH_<NAME>_<suffix> variable name for a provider.
+func envKey(name, suffix string) string {
+	up := strings.ToUpper(name)
+	up = strings.NewReplacer("-", "_", ".", "_").Replace(up)
+	return "ZERO_OAUTH_" + up + "_" + suffix
+}
+
+// ResolveConfig builds the oauth.Config and default Flow for a provider from its
+// env/config:
+//
+//	ZERO_OAUTH_<NAME>_CLIENT_ID       (required)
+//	ZERO_OAUTH_<NAME>_CLIENT_SECRET   (optional)
+//	ZERO_OAUTH_<NAME>_AUTHORIZE_URL   (loopback flow; or discovered via issuer)
+//	ZERO_OAUTH_<NAME>_TOKEN_URL       (or discovered via issuer)
+//	ZERO_OAUTH_<NAME>_DEVICE_URL      (device flow; or discovered via issuer)
+//	ZERO_OAUTH_<NAME>_ISSUER_URL      (RFC 8414 / OIDC discovery base)
+//	ZERO_OAUTH_<NAME>_SCOPES          (space-separated)
+//	ZERO_OAUTH_<NAME>_FLOW            ("loopback" [default] | "device")
+//
+// Pinned credential-bearing endpoints must be https (loopback exempt).
+func (r *Registry) ResolveConfig(name string, env map[string]string) (Config, Flow, error) {
+	if err := ValidateProviderName(name); err != nil {
+		return Config{}, "", err
+	}
+	// A baked-in preset (if any) supplies defaults, but ONLY when the operator opts
+	// in with ZERO_OAUTH_ALLOW_PRESETS — otherwise no third-party client identity is
+	// used and every field must come from a ZERO_OAUTH_<NAME>_* env var (env wins).
+	var preset providerPreset
+	if presetsAllowed(env) {
+		preset, _ = lookupOAuthPreset(name)
+	}
+	cfg := Config{
+		ClientID:                    firstNonEmpty(strings.TrimSpace(envValue(env, envKey(name, "CLIENT_ID"))), preset.ClientID),
+		ClientSecret:                firstNonEmpty(strings.TrimSpace(envValue(env, envKey(name, "CLIENT_SECRET"))), preset.ClientSecret),
+		AuthorizationEndpoint:       firstNonEmpty(strings.TrimSpace(envValue(env, envKey(name, "AUTHORIZE_URL"))), preset.AuthorizationEndpoint),
+		TokenEndpoint:               firstNonEmpty(strings.TrimSpace(envValue(env, envKey(name, "TOKEN_URL"))), preset.TokenEndpoint),
+		DeviceAuthorizationEndpoint: firstNonEmpty(strings.TrimSpace(envValue(env, envKey(name, "DEVICE_URL"))), preset.DeviceAuthorizationEndpoint),
+		IssuerURL:                   firstNonEmpty(strings.TrimSpace(envValue(env, envKey(name, "ISSUER_URL"))), preset.IssuerURL),
+		Scopes:                      scopesOrPreset(envValue(env, envKey(name, "SCOPES")), preset.Scopes),
+	}
+	if cfg.ClientID == "" {
+		hint := ""
+		if _, ok := lookupOAuthPreset(name); ok {
+			hint = " (or set ZERO_OAUTH_ALLOW_PRESETS=1 to use the built-in preset)"
+		}
+		return Config{}, "", fmt.Errorf("oauth: provider %q is not configured; set %s (and its endpoints or an issuer)%s", name, envKey(name, "CLIENT_ID"), hint)
+	}
+	var flow Flow
+	switch strings.ToLower(strings.TrimSpace(envValue(env, envKey(name, "FLOW")))) {
+	case "":
+		flow = preset.Flow
+		if flow == "" {
+			flow = FlowLoopback
+		}
+	case string(FlowLoopback):
+		flow = FlowLoopback
+	case string(FlowDevice):
+		flow = FlowDevice
+	default:
+		return Config{}, "", fmt.Errorf("oauth: provider %q has invalid %s (want loopback or device)", name, envKey(name, "FLOW"))
+	}
+	// A token endpoint (for exchange/refresh) must be reachable directly or via
+	// discovery. The per-flow authorize/device endpoints are checked at login
+	// time (after discovery), so a refresh-only config needs only a token URL.
+	if cfg.IssuerURL == "" && cfg.TokenEndpoint == "" {
+		return Config{}, "", fmt.Errorf("oauth: provider %q needs %s or %s", name, envKey(name, "TOKEN_URL"), envKey(name, "ISSUER_URL"))
+	}
+	for _, ep := range []string{cfg.TokenEndpoint, cfg.AuthorizationEndpoint, cfg.DeviceAuthorizationEndpoint, cfg.IssuerURL} {
+		if ep == "" {
+			continue
+		}
+		if err := validateTokenEndpoint(ep); err != nil {
+			return Config{}, "", err
+		}
+	}
+	return cfg, flow, nil
+}

internal/oauth/providers_test.go

@@ -0,0 +1,97 @@
+package oauth
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestResolveConfigFromEnv(t *testing.T) {
+	r := NewRegistry()
+	env := map[string]string{
+		"ZERO_OAUTH_DEMO_CLIENT_ID":     "my-client",
+		"ZERO_OAUTH_DEMO_CLIENT_SECRET": "shh",
+		"ZERO_OAUTH_DEMO_SCOPES":        "read write",
+		"ZERO_OAUTH_DEMO_AUTHORIZE_URL": "https://auth.example.com/authorize",
+		"ZERO_OAUTH_DEMO_TOKEN_URL":     "https://auth.example.com/token",
+	}
+	cfg, flow, err := r.ResolveConfig("demo", env)
+	if err != nil {
+		t.Fatalf("ResolveConfig: %v", err)
+	}
+	if cfg.ClientID != "my-client" || cfg.ClientSecret != "shh" {
+		t.Fatalf("client creds not applied: %+v", cfg)
+	}
+	if len(cfg.Scopes) != 2 || cfg.Scopes[0] != "read" {
+		t.Fatalf("scopes = %v", cfg.Scopes)
+	}
+	if cfg.TokenEndpoint != "https://auth.example.com/token" {
+		t.Fatalf("token endpoint = %q", cfg.TokenEndpoint)
+	}
+	if flow != FlowLoopback {
+		t.Fatalf("flow = %q, want loopback default", flow)
+	}
+}
+
+func TestResolveConfigDeviceFlow(t *testing.T) {
+	r := NewRegistry()
+	env := map[string]string{
+		"ZERO_OAUTH_DEMO_CLIENT_ID":  "c",
+		"ZERO_OAUTH_DEMO_TOKEN_URL":  "https://auth.example.com/token",
+		"ZERO_OAUTH_DEMO_DEVICE_URL": "https://auth.example.com/device",
+		"ZERO_OAUTH_DEMO_FLOW":       "device",
+	}
+	_, flow, err := r.ResolveConfig("demo", env)
+	if err != nil {
+		t.Fatalf("ResolveConfig: %v", err)
+	}
+	if flow != FlowDevice {
+		t.Fatalf("flow = %q, want device", flow)
+	}
+}
+
+func TestResolveConfigRequiresClientID(t *testing.T) {
+	r := NewRegistry()
+	if _, _, err := r.ResolveConfig("demo", map[string]string{}); err == nil {
+		t.Fatal("missing client id must error")
+	}
+}
+
+func TestResolveConfigRequiresEndpointsOrIssuer(t *testing.T) {
+	r := NewRegistry()
+	// client id but no token endpoint and no issuer => error.
+	_, _, err := r.ResolveConfig("demo", map[string]string{"ZERO_OAUTH_DEMO_CLIENT_ID": "c"})
+	if err == nil {
+		t.Fatal("missing endpoints/issuer must error")
+	}
+}
+
+func TestResolveConfigRejectsInsecureEndpoint(t *testing.T) {
+	r := NewRegistry()
+	env := map[string]string{
+		"ZERO_OAUTH_DEMO_CLIENT_ID":     "c",
+		"ZERO_OAUTH_DEMO_AUTHORIZE_URL": "https://auth.example.com/authorize",
+		"ZERO_OAUTH_DEMO_TOKEN_URL":     "http://insecure.example/token", // non-https, non-loopback
+	}
+	_, _, err := r.ResolveConfig("demo", env)
+	if !errors.Is(err, ErrInsecureTokenEndpoint) {
+		t.Fatalf("err = %v, want ErrInsecureTokenEndpoint", err)
+	}
+}
+
+func TestResolveConfigInvalidName(t *testing.T) {
+	r := NewRegistry()
+	for _, bad := range []string{"", "has space", "../escape", "a/b"} {
+		if _, _, err := r.ResolveConfig(bad, nil); err == nil {
+			t.Errorf("ResolveConfig(%q) should reject invalid name", bad)
+		}
+	}
+}
+
+func TestEnvKey(t *testing.T) {
+	if got := envKey("my-svc", "CLIENT_ID"); got != "ZERO_OAUTH_MY_SVC_CLIENT_ID" {
+		t.Fatalf("envKey = %q", got)
+	}
+	if got := envKey("two.part", "SCOPES"); got != "ZERO_OAUTH_TWO_PART_SCOPES" {
+		t.Fatalf("envKey = %q", got)
+	}
+}

internal/oauth/scheduler.go

@@ -0,0 +1,125 @@
+package oauth
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+// maxSchedulerLoadErrors bounds consecutive token-load failures before the
+// scheduler gives up, so a transient error retries but a permanent one (e.g. a
+// deleted token) does not loop forever.
+const maxSchedulerLoadErrors = 5
+
+// RefreshScheduler proactively refreshes a stored provider token shortly before
+// it expires. It is an OPTIMIZATION over the on-demand GetFresh path, never the
+// source of truth: a failed scheduled refresh is non-fatal and simply retried at
+// the next expiry. It is a no-op for a token with no refresh token or no expiry.
+type RefreshScheduler struct {
+	mu      sync.Mutex
+	cancel  context.CancelFunc
+	done    chan struct{}
+	started bool
+}
+
+// NewRefreshScheduler returns an idle scheduler.
+func NewRefreshScheduler() *RefreshScheduler {
+	return &RefreshScheduler{}
+}
+
+// Start begins proactively refreshing key via the manager until the context is
+// canceled or Stop is called. It returns immediately; refresh happens in a
+// goroutine. Calling Start twice is a no-op after the first.
+func (s *RefreshScheduler) Start(ctx context.Context, m *Manager, key string) {
+	s.mu.Lock()
+	if s.started {
+		s.mu.Unlock()
+		return
+	}
+	runCtx, cancel := context.WithCancel(ctx)
+	s.cancel = cancel
+	s.done = make(chan struct{})
+	s.started = true
+	done := s.done
+	s.mu.Unlock()
+
+	go s.loop(runCtx, m, key, done)
+}
+
+func (s *RefreshScheduler) loop(ctx context.Context, m *Manager, key string, done chan struct{}) {
+	defer close(done)
+	loadErrors := 0
+	for {
+		token, err := m.loadToken(key)
+		if err != nil {
+			// A load error may be transient (a concurrent store write, a brief I/O
+			// hiccup): back off and retry rather than permanently stopping proactive
+			// refresh. Give up only after repeated consecutive failures.
+			loadErrors++
+			if loadErrors >= maxSchedulerLoadErrors {
+				return
+			}
+			select {
+			case <-ctx.Done():
+				return
+			case <-time.After(m.buffer):
+			}
+			continue
+		}
+		loadErrors = 0
+		// No refresh token or no expiry => nothing to schedule on a timer.
+		if token.RefreshToken == "" || token.ExpiresAt.IsZero() {
+			return
+		}
+		delay := s.delayUntilRefresh(token.ExpiresAt, m.buffer, m.now())
+		select {
+		case <-ctx.Done():
+			return
+		case <-time.After(delay):
+		}
+		// Best-effort refresh; failure is non-fatal — reload and reschedule (the
+		// on-demand GetFresh remains the safety net for callers).
+		if _, err := m.GetFresh(ctx, key); err != nil {
+			// Wait a bounded backoff before retrying so a persistently failing
+			// refresh does not hot-loop.
+			select {
+			case <-ctx.Done():
+				return
+			case <-time.After(m.buffer):
+			}
+		}
+	}
+}
+
+// delayUntilRefresh computes how long to wait before refreshing: aim for buffer
+// before expiry, clamped to >= 0, plus a small deterministic jitter so many
+// sessions do not refresh in lockstep.
+func (s *RefreshScheduler) delayUntilRefresh(expiresAt time.Time, buffer time.Duration, now time.Time) time.Duration {
+	target := expiresAt.Add(-buffer)
+	delay := target.Sub(now)
+	if delay < 0 {
+		delay = 0
+	}
+	// Jitter up to ~10% of the buffer, derived from the expiry nanos (no RNG dep).
+	if buffer > 0 {
+		jitter := time.Duration(expiresAt.UnixNano()%int64(buffer/10+1)) % (buffer/10 + 1)
+		delay += jitter
+	}
+	return delay
+}
+
+// Stop cancels the scheduler and waits for its goroutine to exit. Safe to call
+// more than once and on a never-started scheduler.
+func (s *RefreshScheduler) Stop() {
+	s.mu.Lock()
+	cancel := s.cancel
+	done := s.done
+	s.cancel = nil
+	s.mu.Unlock()
+	if cancel != nil {
+		cancel()
+	}
+	if done != nil {
+		<-done
+	}
+}

internal/oauth/scheduler_test.go

@@ -0,0 +1,72 @@
+package oauth
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"path/filepath"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestRefreshSchedulerNoRefreshTokenIsNoop(t *testing.T) {
+	m := managerFor(t, map[string]string{"ZERO_OAUTH_DEMO_CLIENT_ID": "c"}, nil)
+	// Token without a refresh token => scheduler must exit promptly (no-op).
+	if err := m.store.Save(ProviderKey("demo"), Token{AccessToken: "a", ExpiresAt: time.Now().Add(time.Hour)}); err != nil {
+		t.Fatalf("seed Save: %v", err)
+	}
+	s := NewRefreshScheduler()
+	s.Start(context.Background(), m, ProviderKey("demo"))
+	// Stop waits for the goroutine; if it didn't exit on its own this still returns
+	// because Stop cancels — but the loop should already be done.
+	s.Stop()
+}
+
+func TestRefreshSchedulerRefreshesBeforeExpiry(t *testing.T) {
+	var hits atomic.Int32
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		hits.Add(1)
+		_, _ = io.WriteString(w, `{"access_token":"refreshed","expires_in":3600}`)
+	}))
+	defer server.Close()
+
+	store, err := NewStore(StoreOptions{FilePath: filepath.Join(t.TempDir(), "tok.json")})
+	if err != nil {
+		t.Fatalf("NewStore: %v", err)
+	}
+	m, err := NewManager(ManagerOptions{
+		Store: store,
+		Env: map[string]string{
+			"ZERO_OAUTH_DEMO_CLIENT_ID": "c",
+			"ZERO_OAUTH_DEMO_TOKEN_URL": server.URL,
+		},
+		RefreshBuffer: 10 * time.Millisecond,
+	})
+	if err != nil {
+		t.Fatalf("NewManager: %v", err)
+	}
+	// Expiry just past the buffer so the scheduled delay is ~0 and a refresh fires
+	// almost immediately.
+	if err := store.Save(ProviderKey("demo"), Token{AccessToken: "old", RefreshToken: "rt", ExpiresAt: time.Now().Add(15 * time.Millisecond)}); err != nil {
+		t.Fatalf("seed Save: %v", err)
+	}
+
+	s := NewRefreshScheduler()
+	s.Start(context.Background(), m, ProviderKey("demo"))
+	defer s.Stop()
+
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		stored, _, err := store.Load(ProviderKey("demo"))
+		if err != nil {
+			t.Fatalf("Load: %v", err)
+		}
+		if stored.AccessToken == "refreshed" {
+			return // success
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+	t.Fatalf("scheduler did not refresh before expiry (token endpoint hits=%d)", hits.Load())
+}

internal/oauth/store.go

@@ -0,0 +1,505 @@
+package oauth
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/keyring"
+)
+
+const (
+	storeSchemaVersion = 1
+	// KeyPrefixProvider namespaces provider-login tokens; MCP server tokens live
+	// under KeyPrefixMCP in the same format (so a future MCP migration is a key
+	// rename, not a format change).
+	KeyPrefixProvider = "provider:"
+	KeyPrefixMCP      = "mcp:"
+)
+
+// keyPattern bounds a token key to a safe, single-segment namespaced identifier
+// so a key can never traverse or collide with store internals.
+var keyPattern = regexp.MustCompile(`^(provider|mcp):[A-Za-z0-9][A-Za-z0-9._-]{0,127}$`)
+
+// ValidateKey reports whether key is a well-formed namespaced token key.
+func ValidateKey(key string) error {
+	if !keyPattern.MatchString(key) {
+		return fmt.Errorf("oauth: invalid token key %q (want \"provider:<name>\" or \"mcp:<name>\")", key)
+	}
+	return nil
+}
+
+// ProviderKey builds the store key for a provider login.
+func ProviderKey(name string) string { return KeyPrefixProvider + name }
+
+// Status is a redaction-safe summary of a stored token (no secret material).
+type Status struct {
+	Key             string    `json:"key"`
+	HasToken        bool      `json:"hasToken"`
+	HasRefreshToken bool      `json:"hasRefreshToken"`
+	TokenType       string    `json:"tokenType,omitempty"`
+	Account         string    `json:"account,omitempty"`
+	Scopes          []string  `json:"scopes,omitempty"`
+	ExpiresAt       time.Time `json:"expiresAt,omitempty"`
+	Expired         bool      `json:"expired"`
+}
+
+// StoreOptions configures where provider OAuth tokens are persisted.
+type StoreOptions struct {
+	FilePath string
+	Env      map[string]string
+	Now      func() time.Time
+	// Storage selects the backend: "" / "file" => a 0600 JSON file (default);
+	// "encrypted-file" => an AES-256-GCM encrypted file; "keyring" => the OS
+	// keyring. When empty it falls back to ZERO_OAUTH_STORAGE.
+	Storage string
+	// Encrypted is a legacy alias for Storage=="encrypted-file" (AES-256-GCM at
+	// rest). Ignored when Storage is set.
+	Encrypted bool
+	// Keyring is the client used when Storage=="keyring"; nil => keyring.New().
+	// Injected by tests to avoid touching a real keychain.
+	Keyring KeyringClient
+}
+
+// KeyringClient is the minimal OS-keyring surface the store needs. *keyring.Keyring
+// satisfies it; tests inject a fake.
+type KeyringClient interface {
+	Get(service, account string) (string, bool, error)
+	Set(service, account, secret string) error
+	Delete(service, account string) (bool, error)
+}
+
+// Keyring storage stores the whole token blob under one fixed entry.
+const (
+	keyringService = "zero"
+	keyringAccount = "oauth-tokens"
+)
+
+// Store persists OAuth tokens (provider + MCP namespaces) as one JSON blob,
+// written atomically through a pluggable backend (a 0600 file guarded by a
+// cross-process lock, or the OS keyring). When crypter is non-nil the file blob
+// is AES-256-GCM ciphertext at rest.
+type Store struct {
+	blob    blobStore
+	crypter *aesGCMCrypter // nil => plaintext blob
+	now     func() time.Time
+	mu      sync.Mutex
+}
+
+type storeFile struct {
+	SchemaVersion int              `json:"schemaVersion"`
+	Tokens        map[string]Token `json:"tokens"`
+}
+
+// ResolveStorePath determines the on-disk location for provider OAuth tokens,
+// honoring ZERO_OAUTH_TOKENS_PATH, then XDG_CONFIG_HOME, then the home dir.
+func ResolveStorePath(env map[string]string) (string, error) {
+	if override := strings.TrimSpace(envValue(env, "ZERO_OAUTH_TOKENS_PATH")); override != "" {
+		if filepath.IsAbs(override) {
+			return filepath.Clean(override), nil
+		}
+		return filepath.Abs(override)
+	}
+	configHome := strings.TrimSpace(envValue(env, "XDG_CONFIG_HOME"))
+	if configHome == "" {
+		home := strings.TrimSpace(firstNonEmpty(envValue(env, "HOME"), envValue(env, "USERPROFILE")))
+		if home == "" {
+			var err error
+			home, err = os.UserHomeDir()
+			if err != nil {
+				return "", fmt.Errorf("oauth: resolve user home: %w", err)
+			}
+		}
+		configHome = filepath.Join(home, ".config")
+	} else if !filepath.IsAbs(configHome) {
+		resolved, err := filepath.Abs(configHome)
+		if err != nil {
+			return "", err
+		}
+		configHome = resolved
+	}
+	return filepath.Join(configHome, "zero", "oauth-tokens.json"), nil
+}
+
+// NewStore builds a token store with the configured backend (file by default,
+// or the OS keyring when Storage/ZERO_OAUTH_STORAGE selects it).
+func NewStore(options StoreOptions) (*Store, error) {
+	now := options.Now
+	if now == nil {
+		now = time.Now
+	}
+	storage := strings.TrimSpace(options.Storage)
+	if storage == "" {
+		storage = strings.TrimSpace(envValue(options.Env, "ZERO_OAUTH_STORAGE"))
+	}
+	if storage == "" && options.Encrypted {
+		storage = "encrypted-file" // legacy alias
+	}
+	switch storage {
+	case "", "file":
+		path, err := resolveStoreFilePath(options)
+		if err != nil {
+			return nil, err
+		}
+		return &Store{blob: fileBlob{path: path}, now: now}, nil
+	case "encrypted-file":
+		path, err := resolveStoreFilePath(options)
+		if err != nil {
+			return nil, err
+		}
+		// The file blob holds AES-256-GCM ciphertext; the per-user secret lives in
+		// a sibling ".secret" file (see encrypt.go).
+		return &Store{blob: fileBlob{path: path}, crypter: newAESGCMCrypter(path + ".secret"), now: now}, nil
+	case "keyring":
+		kr := options.Keyring
+		if kr == nil {
+			osKeyring := keyring.New()
+			if !osKeyring.Available() {
+				return nil, fmt.Errorf("oauth: keyring storage requested but not available on %s; use file storage", runtime.GOOS)
+			}
+			kr = osKeyring
+		}
+		// Serialize the keyring's read-modify-write across processes with a lock
+		// file beside where the file backend would live. Best-effort: if no config
+		// location resolves, fall back to in-process serialization only.
+		lockPath := ""
+		if storePath, perr := ResolveStorePath(options.Env); perr == nil {
+			lockPath = filepath.Join(filepath.Dir(storePath), "oauth-keyring.lockfile")
+		}
+		return &Store{blob: keyringBlob{kr: kr, service: keyringService, account: keyringAccount, lockPath: lockPath}, now: now}, nil
+	default:
+		return nil, fmt.Errorf("oauth: unknown storage %q (want \"file\", \"encrypted-file\", or \"keyring\")", storage)
+	}
+}
+
+// resolveStoreFilePath resolves the absolute file path for the file backend.
+func resolveStoreFilePath(options StoreOptions) (string, error) {
+	filePath := options.FilePath
+	var err error
+	if strings.TrimSpace(filePath) == "" {
+		filePath, err = ResolveStorePath(options.Env)
+		if err != nil {
+			return "", err
+		}
+	}
+	if !filepath.IsAbs(filePath) {
+		filePath, err = filepath.Abs(filePath)
+		if err != nil {
+			return "", err
+		}
+	}
+	return filepath.Clean(filePath), nil
+}
+
+// FilePath returns the resolved token store location (a path for the file
+// backend, or a "keyring:..." identifier for the keyring backend).
+func (s *Store) FilePath() string { return s.blob.location() }
+
+// Save persists a token under key, replacing any existing entry.
+func (s *Store) Save(key string, token Token) error {
+	if err := ValidateKey(key); err != nil {
+		return err
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.blob.withLock(s.now, func() error {
+		state, err := s.readState()
+		if err != nil {
+			return err
+		}
+		state.Tokens[key] = token
+		return s.writeState(state)
+	})
+}
+
+// Load returns the token for key; the bool is false when none is stored.
+func (s *Store) Load(key string) (Token, bool, error) {
+	if err := ValidateKey(key); err != nil {
+		return Token{}, false, err
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	state, err := s.readState()
+	if err != nil {
+		return Token{}, false, err
+	}
+	token, ok := state.Tokens[key]
+	return token, ok, nil
+}
+
+// Delete removes the token for key, reporting whether one was present.
+func (s *Store) Delete(key string) (bool, error) {
+	if err := ValidateKey(key); err != nil {
+		return false, err
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	var removed bool
+	err := s.blob.withLock(s.now, func() error {
+		state, err := s.readState()
+		if err != nil {
+			return err
+		}
+		if _, ok := state.Tokens[key]; !ok {
+			return nil
+		}
+		delete(state.Tokens, key)
+		removed = true
+		return s.writeState(state)
+	})
+	return removed, err
+}
+
+// Status returns redaction-safe summaries of every stored token, sorted by key.
+// An optional prefix filters to one namespace (e.g. KeyPrefixProvider).
+func (s *Store) Status(prefix string) ([]Status, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	state, err := s.readState()
+	if err != nil {
+		return nil, err
+	}
+	keys := make([]string, 0, len(state.Tokens))
+	for k := range state.Tokens {
+		if prefix == "" || strings.HasPrefix(k, prefix) {
+			keys = append(keys, k)
+		}
+	}
+	sort.Strings(keys)
+	now := s.now()
+	out := make([]Status, 0, len(keys))
+	for _, k := range keys {
+		token := state.Tokens[k]
+		out = append(out, Status{
+			Key:             k,
+			HasToken:        strings.TrimSpace(token.AccessToken) != "",
+			HasRefreshToken: strings.TrimSpace(token.RefreshToken) != "",
+			TokenType:       token.TokenType,
+			Account:         token.Account,
+			Scopes:          token.Scopes,
+			ExpiresAt:       token.ExpiresAt,
+			Expired:         token.Expired(now),
+		})
+	}
+	return out, nil
+}
+
+func (s *Store) readState() (storeFile, error) {
+	data, ok, err := s.blob.read()
+	if err != nil {
+		return storeFile{}, err
+	}
+	if !ok {
+		return emptyStoreFile(), nil
+	}
+	if s.crypter != nil {
+		// Encrypted backend: the blob is AES-256-GCM ciphertext, not JSON.
+		data, err = s.crypter.open(data)
+		if err != nil {
+			return storeFile{}, fmt.Errorf("oauth: decrypt token store at %s: %w", s.blob.location(), err)
+		}
+	}
+	var state storeFile
+	if err := json.Unmarshal(data, &state); err != nil {
+		return storeFile{}, fmt.Errorf("oauth: invalid token store at %s: %w", s.blob.location(), err)
+	}
+	if state.SchemaVersion != storeSchemaVersion {
+		return storeFile{}, fmt.Errorf("oauth: invalid token store at %s: unsupported schemaVersion", s.blob.location())
+	}
+	if state.Tokens == nil {
+		state.Tokens = map[string]Token{}
+	}
+	for key := range state.Tokens {
+		if err := ValidateKey(key); err != nil {
+			return storeFile{}, fmt.Errorf("oauth: invalid token store at %s: %w", s.blob.location(), err)
+		}
+	}
+	return state, nil
+}
+
+func (s *Store) writeState(state storeFile) error {
+	data, err := json.MarshalIndent(state, "", "  ")
+	if err != nil {
+		return err
+	}
+	// Plaintext keeps the trailing newline for a tidy file; the encrypted backend
+	// writes opaque ciphertext instead.
+	payload := append(data, '\n')
+	if s.crypter != nil {
+		payload, err = s.crypter.seal(data)
+		if err != nil {
+			return err
+		}
+	}
+	return s.blob.write(payload)
+}
+
+func emptyStoreFile() storeFile {
+	return storeFile{SchemaVersion: storeSchemaVersion, Tokens: map[string]Token{}}
+}
+
+// blobStore abstracts the persistence of the whole token blob behind the Store,
+// so the same store logic backs either a 0600 file or the OS keyring.
+type blobStore interface {
+	// read returns the stored blob; ok is false when nothing is stored yet.
+	read() (data []byte, ok bool, err error)
+	// write replaces the stored blob.
+	write(data []byte) error
+	// withLock runs fn under whatever cross-process exclusion the backend offers
+	// (a lock file for the file backend; none for the keyring, which is the
+	// authoritative store and is serialized within the process by Store.mu).
+	withLock(now func() time.Time, fn func() error) error
+	// location is a human-readable identifier for diagnostics/errors.
+	location() string
+}
+
+// fileBlob persists the blob as a 0600 JSON file, written atomically and guarded
+// by a cross-process lock file. Behavior matches the original file store.
+type fileBlob struct{ path string }
+
+func (b fileBlob) read() ([]byte, bool, error) {
+	data, err := os.ReadFile(b.path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, false, nil
+		}
+		return nil, false, err
+	}
+	return data, true, nil
+}
+
+func (b fileBlob) write(data []byte) error {
+	if err := os.MkdirAll(filepath.Dir(b.path), 0o700); err != nil {
+		return err
+	}
+	tempPath := fmt.Sprintf("%s.tmp-%d-%d", b.path, os.Getpid(), time.Now().UnixNano())
+	if err := os.WriteFile(tempPath, data, 0o600); err != nil {
+		return err
+	}
+	if err := os.Rename(tempPath, b.path); err != nil {
+		_ = os.Remove(tempPath)
+		return err
+	}
+	return nil
+}
+
+func (b fileBlob) withLock(now func() time.Time, fn func() error) error {
+	unlock, err := acquireFileLock(b.path+".lockfile", now)
+	if err != nil {
+		return err
+	}
+	defer unlock()
+	return fn()
+}
+
+func (b fileBlob) location() string { return b.path }
+
+// keyringBlob persists the blob in the OS keyring as a single base64 entry
+// (base64 keeps the multi-line JSON a single, control-character-free value).
+type keyringBlob struct {
+	kr      KeyringClient
+	service string
+	account string
+	// lockPath, when set, is a cross-process lock file serializing the keyring's
+	// read-modify-write so concurrent processes don't clobber each other's tokens.
+	lockPath string
+}
+
+func (b keyringBlob) read() ([]byte, bool, error) {
+	enc, ok, err := b.kr.Get(b.service, b.account)
+	if err != nil || !ok {
+		return nil, ok, err
+	}
+	data, err := base64.StdEncoding.DecodeString(strings.TrimSpace(enc))
+	if err != nil {
+		return nil, false, fmt.Errorf("oauth: decode keyring token blob: %w", err)
+	}
+	return data, true, nil
+}
+
+func (b keyringBlob) write(data []byte) error {
+	return b.kr.Set(b.service, b.account, base64.StdEncoding.EncodeToString(data))
+}
+
+// withLock serializes the keyring's read-modify-write. Store.mu covers the
+// in-process case; lockPath (when set) adds cross-process exclusion so two
+// processes can't both read the blob, modify, and write — dropping a token.
+func (b keyringBlob) withLock(now func() time.Time, fn func() error) error {
+	if b.lockPath == "" {
+		return fn()
+	}
+	unlock, err := acquireFileLock(b.lockPath, now)
+	if err != nil {
+		return err
+	}
+	defer unlock()
+	return fn()
+}
+
+func (b keyringBlob) location() string { return "keyring:" + b.service + "/" + b.account }
+
+// FormatStatuses renders a human-readable status table without leaking token
+// material.
+func FormatStatuses(statuses []Status) string {
+	if len(statuses) == 0 {
+		return "No OAuth provider logins are stored."
+	}
+	var b strings.Builder
+	for i, st := range statuses {
+		if i > 0 {
+			b.WriteByte('\n')
+		}
+		name := strings.TrimPrefix(st.Key, KeyPrefixProvider)
+		b.WriteString(name)
+		b.WriteString(": ")
+		if !st.HasToken {
+			b.WriteString("no token")
+			continue
+		}
+		b.WriteString("logged in")
+		if st.Account != "" {
+			b.WriteString(" as " + st.Account)
+		}
+		if st.HasRefreshToken {
+			b.WriteString(" (refreshable)")
+		}
+		if !st.ExpiresAt.IsZero() {
+			if st.Expired {
+				b.WriteString(", expired at ")
+			} else {
+				b.WriteString(", expires ")
+			}
+			b.WriteString(st.ExpiresAt.UTC().Format(time.RFC3339))
+		}
+	}
+	return b.String()
+}
+
+// envValue reads a variable. A non-nil env map is authoritative (hermetic): a
+// missing key returns "" rather than falling back to the process environment, so
+// a caller/test that passes a controlled map can never pick up ambient
+// ZERO_OAUTH_* / HOME / XDG_CONFIG_HOME values. Only a nil map uses os.Getenv.
+func envValue(env map[string]string, key string) string {
+	if env != nil {
+		return env[key]
+	}
+	return os.Getenv(key)
+}
+
+func firstNonEmpty(values ...string) string {
+	for _, v := range values {
+		if strings.TrimSpace(v) != "" {
+			return v
+		}
+	}
+	return ""
+}

internal/oauth/store_keyring_test.go

@@ -0,0 +1,113 @@
+package oauth
+
+import (
+	"strings"
+	"testing"
+)
+
+// fakeKR is an in-memory KeyringClient for exercising the keyring backend
+// without touching a real OS keychain.
+type fakeKR struct{ data map[string]string }
+
+func newFakeKR() *fakeKR { return &fakeKR{data: map[string]string{}} }
+
+func (f *fakeKR) Get(service, account string) (string, bool, error) {
+	v, ok := f.data[service+"/"+account]
+	return v, ok, nil
+}
+func (f *fakeKR) Set(service, account, secret string) error {
+	f.data[service+"/"+account] = secret
+	return nil
+}
+func (f *fakeKR) Delete(service, account string) (bool, error) {
+	key := service + "/" + account
+	_, ok := f.data[key]
+	delete(f.data, key)
+	return ok, nil
+}
+
+func TestStoreKeyringBackendRoundTrip(t *testing.T) {
+	// Keep the cross-process keyring lock file inside a temp config dir.
+	t.Setenv("XDG_CONFIG_HOME", t.TempDir())
+	kr := newFakeKR()
+	s, err := NewStore(StoreOptions{Storage: "keyring", Keyring: kr})
+	if err != nil {
+		t.Fatalf("NewStore(keyring): %v", err)
+	}
+	if !strings.HasPrefix(s.FilePath(), "keyring:") {
+		t.Fatalf("FilePath = %q, want keyring identifier", s.FilePath())
+	}
+
+	if err := s.Save(ProviderKey("demo"), Token{AccessToken: "a", RefreshToken: "r"}); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	got, ok, err := s.Load(ProviderKey("demo"))
+	if err != nil || !ok {
+		t.Fatalf("Load: ok=%v err=%v", ok, err)
+	}
+	if got.AccessToken != "a" || got.RefreshToken != "r" {
+		t.Fatalf("Load = %#v", got)
+	}
+
+	// The blob is stored base64-encoded, so the raw JSON field names never appear.
+	raw := kr.data[keyringService+"/"+keyringAccount]
+	if raw == "" {
+		t.Fatal("nothing stored in keyring")
+	}
+	if strings.Contains(raw, "access_token") {
+		t.Fatalf("keyring blob is not encoded: %s", raw)
+	}
+
+	removed, err := s.Delete(ProviderKey("demo"))
+	if err != nil || !removed {
+		t.Fatalf("Delete: removed=%v err=%v", removed, err)
+	}
+	if _, ok, _ := s.Load(ProviderKey("demo")); ok {
+		t.Fatal("token still present after delete")
+	}
+}
+
+func TestNewStoreStorageSelection(t *testing.T) {
+	// Unknown storage is rejected (fail closed).
+	if _, err := NewStore(StoreOptions{Storage: "bogus"}); err == nil {
+		t.Fatal("unknown storage should error")
+	}
+	// ZERO_OAUTH_STORAGE selects the keyring (with an injected client).
+	s, err := NewStore(StoreOptions{
+		Env:     map[string]string{"ZERO_OAUTH_STORAGE": "keyring"},
+		Keyring: newFakeKR(),
+	})
+	if err != nil {
+		t.Fatalf("NewStore(env keyring): %v", err)
+	}
+	if !strings.HasPrefix(s.FilePath(), "keyring:") {
+		t.Fatalf("env did not select keyring backend: %q", s.FilePath())
+	}
+	// Default is the file backend.
+	fileStore, err := NewStore(StoreOptions{FilePath: t.TempDir() + "/oauth-tokens.json"})
+	if err != nil {
+		t.Fatalf("NewStore(file): %v", err)
+	}
+	if strings.HasPrefix(fileStore.FilePath(), "keyring:") {
+		t.Fatalf("default backend should be file, got %q", fileStore.FilePath())
+	}
+}
+
+func TestStoreKeyringStatus(t *testing.T) {
+	t.Setenv("XDG_CONFIG_HOME", t.TempDir())
+	kr := newFakeKR()
+	s, err := NewStore(StoreOptions{Storage: "keyring", Keyring: kr})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.Save(ProviderKey("demo"), Token{AccessToken: "a"}); err != nil {
+		t.Fatal(err)
+	}
+	statuses, err := s.Status(KeyPrefixProvider)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(statuses) != 1 || statuses[0].Key != ProviderKey("demo") || !statuses[0].HasToken {
+		t.Fatalf("status = %#v", statuses)
+	}
+}

internal/oauth/store_test.go

@@ -0,0 +1,128 @@
+package oauth
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+	"time"
+)
+
+func newTestStore(t *testing.T) (*Store, string) {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "oauth-tokens.json")
+	s, err := NewStore(StoreOptions{FilePath: path})
+	if err != nil {
+		t.Fatalf("NewStore: %v", err)
+	}
+	return s, path
+}
+
+func TestStoreSaveLoadDelete(t *testing.T) {
+	s, _ := newTestStore(t)
+	tok := Token{AccessToken: "at", RefreshToken: "rt", Account: "me@x"}
+	if err := s.Save(ProviderKey("demo"), tok); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	if err := s.Save(KeyPrefixMCP+"server1", Token{AccessToken: "mcp-at"}); err != nil {
+		t.Fatalf("Save mcp: %v", err)
+	}
+	got, ok, err := s.Load(ProviderKey("demo"))
+	if err != nil || !ok || got.AccessToken != "at" || got.Account != "me@x" {
+		t.Fatalf("Load = %+v ok=%v err=%v", got, ok, err)
+	}
+	removed, err := s.Delete(ProviderKey("demo"))
+	if err != nil || !removed {
+		t.Fatalf("Delete = %v %v", removed, err)
+	}
+	if _, ok, _ := s.Load(ProviderKey("demo")); ok {
+		t.Fatal("token should be gone after delete")
+	}
+	// The mcp-namespaced token is untouched.
+	if _, ok, _ := s.Load(KeyPrefixMCP + "server1"); !ok {
+		t.Fatal("mcp token should survive provider delete")
+	}
+}
+
+func TestStoreRejectsInvalidKeys(t *testing.T) {
+	s, _ := newTestStore(t)
+	for _, bad := range []string{"demo", "provider:", "provider:../escape", "mcp:bad/key", "other:x", ""} {
+		if err := s.Save(bad, Token{AccessToken: "x"}); err == nil {
+			t.Errorf("Save(%q) should be rejected", bad)
+		}
+	}
+	for _, ok := range []string{"provider:demo", "mcp:server-1", "provider:two-svc"} {
+		if err := ValidateKey(ok); err != nil {
+			t.Errorf("ValidateKey(%q) = %v, want nil", ok, err)
+		}
+	}
+}
+
+func TestStoreStatusFiltersByPrefix(t *testing.T) {
+	s, _ := newTestStore(t)
+	_ = s.Save(ProviderKey("demo"), Token{AccessToken: "a", RefreshToken: "r", ExpiresAt: time.Now().Add(time.Hour)})
+	_ = s.Save(KeyPrefixMCP+"srv", Token{AccessToken: "m"})
+	statuses, err := s.Status(KeyPrefixProvider)
+	if err != nil {
+		t.Fatalf("Status: %v", err)
+	}
+	if len(statuses) != 1 || statuses[0].Key != ProviderKey("demo") {
+		t.Fatalf("provider status = %+v", statuses)
+	}
+	if !statuses[0].HasRefreshToken {
+		t.Fatal("status should report a refresh token")
+	}
+}
+
+func TestStoreFileMode0600(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("unix file modes")
+	}
+	s, path := newTestStore(t)
+	if err := s.Save(ProviderKey("x"), Token{AccessToken: "a"}); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+	info, err := os.Stat(path)
+	if err != nil {
+		t.Fatalf("stat: %v", err)
+	}
+	if perm := info.Mode().Perm(); perm != 0o600 {
+		t.Fatalf("token file mode = %o, want 600", perm)
+	}
+}
+
+func TestStoreMalformedFailsClosed(t *testing.T) {
+	s, path := newTestStore(t)
+	if err := os.WriteFile(path, []byte("{not json"), 0o600); err != nil {
+		t.Fatalf("corrupt: %v", err)
+	}
+	if _, _, err := s.Load(ProviderKey("x")); err == nil {
+		t.Fatal("malformed store must fail closed")
+	}
+}
+
+func TestEnvValueHermetic(t *testing.T) {
+	t.Setenv("ZERO_OAUTH_DEMO_CLIENT_ID", "ambient")
+	// A non-nil map omitting the key must NOT leak the ambient process value.
+	if got := envValue(map[string]string{}, "ZERO_OAUTH_DEMO_CLIENT_ID"); got != "" {
+		t.Fatalf("non-nil env map must be hermetic, got %q", got)
+	}
+	// A nil map reads the process environment.
+	if got := envValue(nil, "ZERO_OAUTH_DEMO_CLIENT_ID"); got != "ambient" {
+		t.Fatalf("nil env map should read os env, got %q", got)
+	}
+}
+
+func TestResolveStorePathHonorsOverride(t *testing.T) {
+	// Use an OS-appropriate absolute path: a unix-style "/tmp/..." literal is not
+	// absolute on Windows (no drive), so it would be resolved against the current
+	// drive and a verbatim comparison would fail there.
+	override := filepath.Join(t.TempDir(), "custom", "tok.json")
+	path, err := ResolveStorePath(map[string]string{"ZERO_OAUTH_TOKENS_PATH": override})
+	if err != nil {
+		t.Fatalf("ResolveStorePath: %v", err)
+	}
+	if path != override {
+		t.Fatalf("path = %q, want %q", path, override)
+	}
+}

internal/providercatalog/catalog.go

@@ -47,6 +47,17 @@ type Descriptor struct {
 	Local               bool
 	SupportedAPIFormats []APIFormat
 	Aliases             []string
+
+	// OAuth reports that this provider offers an in-app OAuth login that yields a
+	// credential usable for model calls (browser PKCE and/or device code). Only
+	// set for providers where this actually works (not subscription-via-proxy).
+	OAuth bool
+	// OAuthMintsKey reports that the OAuth flow returns/mints a normal API key
+	// (e.g. OpenRouter) rather than a bearer token used directly.
+	OAuthMintsKey bool
+	// OAuthDeviceFlow reports that RFC 8628 device-code login is supported (for
+	// headless / SSH use) in addition to the browser flow.
+	OAuthDeviceFlow bool
 }
 
 func RuntimeSupported(descriptor Descriptor) bool {
@@ -77,7 +88,7 @@ var descriptors = []Descriptor{
 	openAICompat("ollama-cloud", "Ollama Cloud", "https://ollama.com/v1", "qwen3-coder:480b", []string{"OLLAMA_API_KEY"}, "ollama.com", "ollama cloud"),
 	localOpenAI("ollama", "Ollama Local", "http://localhost:11434/v1", "llama3.1", "ollama local"),
 	localOpenAI("lmstudio", "LM Studio", "http://localhost:1234/v1", "local-model", "lm-studio", "lm studio"),
-	openAICompat("openrouter", "OpenRouter", "https://openrouter.ai/api/v1", "openai/gpt-4.1", []string{"OPENROUTER_API_KEY"}),
+	oauthProvider(openAICompat("openrouter", "OpenRouter", "https://openrouter.ai/api/v1", "openai/gpt-4.1", []string{"OPENROUTER_API_KEY"}), true, false),
 	openAICompat("groq", "Groq", "https://api.groq.com/openai/v1", "llama-3.3-70b-versatile", []string{"GROQ_API_KEY"}),
 	openAICompat("deepseek", "DeepSeek", "https://api.deepseek.com/v1", "deepseek-chat", []string{"DEEPSEEK_API_KEY"}),
 	openAICompat("together", "Together AI", "https://api.together.xyz/v1", "meta-llama/Llama-3.3-70B-Instruct-Turbo", []string{"TOGETHER_API_KEY"}),
@@ -89,13 +100,20 @@ var descriptors = []Descriptor{
 	openAICompat("github", "GitHub Models", "https://models.inference.ai.azure.com", "openai/gpt-4.1", []string{"GITHUB_TOKEN"}, "github-models"),
 	transportDescriptor("bedrock", "Amazon Bedrock", TransportBedrock, "https://bedrock-runtime.${AWS_REGION}.amazonaws.com", "anthropic.claude-3-5-sonnet-20241022-v2:0", []string{"AWS_ACCESS_KEY_ID", "AWS_PROFILE"}, []APIFormat{APIFormatBedrockConverse}, true),
 	transportDescriptor("vertex", "Vertex AI", TransportVertex, "https://aiplatform.googleapis.com", "gemini-2.5-pro", []string{"GOOGLE_APPLICATION_CREDENTIALS"}, []APIFormat{APIFormatVertexGenerateContent}, true),
-	openAICompat("xai", "xAI", "https://api.x.ai/v1", "grok-4", []string{"XAI_API_KEY"}),
+	oauthProvider(openAICompat("xai", "xAI", "https://api.x.ai/v1", "grok-4", []string{"XAI_API_KEY"}), false, true),
 	openAICompat("venice", "Venice AI", "https://api.venice.ai/api/v1", "qwen-2.5-qwq-32b", []string{"VENICE_API_KEY"}),
 	openAICompat("xiaomi-mimo", "Xiaomi MiMo", "https://api.mimo.xiaomi.com/openai/v1", "mimo-vl", []string{"MIMO_API_KEY", "XIAOMI_API_KEY"}, "xiaomi mimo"),
 	openAICompat("bankr", "Bankr", "https://api.bankr.bot/v1", "bankr-large", []string{"BANKR_API_KEY"}),
 	openAICompat("zai", "Z.ai", "https://open.bigmodel.cn/api/paas/v4", "glm-4.5", []string{"ZAI_API_KEY", "ZHIPU_API_KEY"}),
 	openAICompat("gitlawb-opengateway", "GitLawb OpenGateway", "https://gateway.gitlawb.com/v1", "gpt-4.1", []string{"GITLAWB_OPENGATEWAY_API_KEY"}, "gitlawb opengateway"),
 	openAICompat("atomic-chat", "Atomic Chat", "https://api.atomic.chat/v1", "gpt-4.1", []string{"ATOMIC_CHAT_API_KEY"}),
+	// ChatGPT subscription via a local OAuth proxy. A ChatGPT (Plus/Pro) OAuth
+	// token only works against ChatGPT's own backend (which is Cloudflare-gated to
+	// the official client), so zero does not call it directly; instead point this
+	// at a local proxy that holds the OAuth session and exposes an OpenAI-compatible
+	// endpoint. Local (no API key — the proxy authenticates); override the base URL
+	// for your proxy's port. See docs/oauth-subscriptions.md.
+	localOpenAI("chatgpt-proxy", "ChatGPT (local OAuth proxy)", "http://localhost:10531/v1", "gpt-5", "chatgpt"),
 	openAICompat("custom-openai-compatible", "Custom OpenAI-compatible", "https://example.invalid/v1", "custom-model", []string{"OPENAI_API_KEY"}, "custom openai compatible"),
 	anthropicCompat("custom-anthropic-compatible", "Custom Anthropic-compatible", "https://example.invalid/anthropic", "custom-model", []string{"ANTHROPIC_API_KEY"}, "custom anthropic compatible"),
 }
@@ -229,6 +247,28 @@ func google(id string, name string, baseURL string, model string, env []string,
 	}
 }
 
+// oauthProvider marks a descriptor as OAuth-capable. mintsKey => the flow returns
+// an API key (OpenRouter); deviceFlow => RFC 8628 device code is also supported.
+func oauthProvider(descriptor Descriptor, mintsKey bool, deviceFlow bool) Descriptor {
+	descriptor.OAuth = true
+	descriptor.OAuthMintsKey = mintsKey
+	descriptor.OAuthDeviceFlow = deviceFlow
+	return descriptor
+}
+
+// OAuthProviders returns the catalog descriptors that support an in-app OAuth
+// login, in catalog order. It is the single source of truth for the wizard's
+// dedicated "Sign in with OAuth" provider list.
+func OAuthProviders() []Descriptor {
+	out := []Descriptor{}
+	for _, descriptor := range descriptors {
+		if descriptor.OAuth {
+			out = append(out, cloneDescriptor(descriptor))
+		}
+	}
+	return out
+}
+
 func localOpenAI(id string, name string, baseURL string, model string, aliases ...string) Descriptor {
 	descriptor := openAICompat(id, name, baseURL, model, nil, aliases...)
 	descriptor.RequiresAuth = false

internal/providercatalog/catalog_test.go

@@ -33,6 +33,7 @@ var expectedCatalogIDs = []string{
 	"zai",
 	"gitlawb-opengateway",
 	"atomic-chat",
+	"chatgpt-proxy",
 	"custom-openai-compatible",
 	"custom-anthropic-compatible",
 }
@@ -220,7 +221,7 @@ func TestListByTransportPreservesCatalogOrder(t *testing.T) {
 		TransportBedrock:         {"bedrock"},
 		TransportVertex:          {"vertex"},
 		TransportAnthropicCompat: {"minimax", "custom-anthropic-compatible"},
-		TransportOpenAICompat:    {"ollama-cloud", "ollama", "lmstudio", "openrouter", "groq", "deepseek", "together", "dashscope", "moonshot", "nvidia-nim", "mistral", "github", "xai", "venice", "xiaomi-mimo", "bankr", "zai", "gitlawb-opengateway", "atomic-chat", "custom-openai-compatible"},
+		TransportOpenAICompat:    {"ollama-cloud", "ollama", "lmstudio", "openrouter", "groq", "deepseek", "together", "dashscope", "moonshot", "nvidia-nim", "mistral", "github", "xai", "venice", "xiaomi-mimo", "bankr", "zai", "gitlawb-opengateway", "atomic-chat", "chatgpt-proxy", "custom-openai-compatible"},
 	}
 
 	for transport, wantIDs := range cases {
@@ -277,6 +278,19 @@ func TestReturnedDescriptorsAreCopies(t *testing.T) {
 	}
 }
 
+func TestOAuthProviderClassification(t *testing.T) {
+	oauthIDs := descriptorIDs(OAuthProviders())
+	if want := []string{"openrouter", "xai"}; !reflect.DeepEqual(oauthIDs, want) {
+		t.Fatalf("OAuthProviders() = %#v, want %#v", oauthIDs, want)
+	}
+	if d, _ := Get("openrouter"); !d.OAuthMintsKey {
+		t.Fatal("openrouter should mint a key")
+	}
+	if d, _ := Get("xai"); !d.OAuthDeviceFlow {
+		t.Fatal("xai should advertise device-code flow")
+	}
+}
+
 func descriptorIDs(descriptors []Descriptor) []string {
 	ids := make([]string, 0, len(descriptors))
 	for _, descriptor := range descriptors {

internal/providercatalog/oauth_test.go

@@ -0,0 +1,60 @@
+package providercatalog
+
+import "testing"
+
+func TestOAuthProviders(t *testing.T) {
+	providers := OAuthProviders()
+	if len(providers) != 2 {
+		t.Fatalf("OAuthProviders() = %d, want 2 (openrouter, xai)", len(providers))
+	}
+	byID := map[string]Descriptor{}
+	for _, d := range providers {
+		if !d.OAuth {
+			t.Fatalf("OAuthProviders() returned a non-OAuth descriptor %q", d.ID)
+		}
+		byID[d.ID] = d
+	}
+	or, ok := byID["openrouter"]
+	if !ok || !or.OAuthMintsKey || or.OAuthDeviceFlow {
+		t.Fatalf("openrouter oauth flags wrong: %+v", or)
+	}
+	xai, ok := byID["xai"]
+	if !ok || xai.OAuthMintsKey || !xai.OAuthDeviceFlow {
+		t.Fatalf("xai oauth flags wrong: %+v", xai)
+	}
+}
+
+func TestOAuthProvidersReturnsIndependentClones(t *testing.T) {
+	first := OAuthProviders()
+	mutated := 0
+	for i := range first {
+		for j := range first[i].AuthEnvVars {
+			first[i].AuthEnvVars[j] = "MUTATED"
+			mutated++
+		}
+	}
+	if mutated == 0 {
+		t.Fatal("expected at least one OAuth descriptor with AuthEnvVars to mutate")
+	}
+	// A fresh call must not observe the in-place mutation: like the other catalog
+	// accessors, OAuthProviders must hand back clones, not shared backing slices.
+	for _, d := range OAuthProviders() {
+		for _, env := range d.AuthEnvVars {
+			if env == "MUTATED" {
+				t.Fatalf("OAuthProviders() leaked a shared AuthEnvVars slice for %q", d.ID)
+			}
+		}
+	}
+}
+
+func TestNonOAuthProvidersNotFlagged(t *testing.T) {
+	for _, d := range All() {
+		switch d.ID {
+		case "openrouter", "xai":
+			continue
+		}
+		if d.OAuth {
+			t.Fatalf("provider %q should not be flagged OAuth-capable", d.ID)
+		}
+	}
+}

internal/provideroauth/openrouter.go

@@ -0,0 +1,172 @@
+// Package provideroauth implements provider-specific OAuth login flows that don't
+// fit the generic env-driven engine in internal/oauth — notably OpenRouter's
+// bespoke PKCE flow, which mints a normal API key rather than returning an OAuth
+// bearer token. These flows are launched from the setup wizard / CLI so a user
+// can "log in with the browser" instead of pasting a key.
+package provideroauth
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/oauth"
+)
+
+const (
+	openRouterDefaultBaseURL  = "https://openrouter.ai"
+	openRouterAuthPath        = "/auth"
+	openRouterKeyExchangePath = "/api/v1/auth/keys"
+	openRouterMaxBody         = 1 << 20
+)
+
+// OpenRouterOptions configures the OpenRouter login flow.
+type OpenRouterOptions struct {
+	// BaseURL overrides https://openrouter.ai (for tests).
+	BaseURL string
+	// HTTPClient performs the key exchange; nil => a client with a sane timeout.
+	HTTPClient *http.Client
+	// OpenBrowser is invoked with the authorize URL. When nil the URL is only
+	// printed (to Out) for the user to open manually.
+	OpenBrowser func(authURL string) error
+	// Out receives the "open this URL" line; nil => the URL is not printed.
+	Out io.Writer
+	// Timeout bounds the whole interactive login; 0 => 5 minutes.
+	Timeout time.Duration
+}
+
+// OpenRouterLogin runs OpenRouter's loopback PKCE flow and returns a freshly
+// minted OpenRouter API key. The flow needs no client_id: a local callback
+// captures the authorization code, which is exchanged (with the PKCE verifier)
+// at /api/v1/auth/keys for a key. PKCE (S256) binds the code to this client, so
+// no separate CSRF state is required. The returned key is a normal credential
+// the caller stores as the provider's API key.
+func OpenRouterLogin(ctx context.Context, opts OpenRouterOptions) (string, error) {
+	base := strings.TrimRight(strings.TrimSpace(opts.BaseURL), "/")
+	if base == "" {
+		base = openRouterDefaultBaseURL
+	}
+	client := opts.HTTPClient
+	if client == nil {
+		client = &http.Client{Timeout: 60 * time.Second}
+	}
+	timeout := opts.Timeout
+	if timeout <= 0 {
+		timeout = 5 * time.Minute
+	}
+	ctx, cancel := context.WithTimeout(ctx, timeout)
+	defer cancel()
+
+	pkce, err := oauth.NewPKCE()
+	if err != nil {
+		return "", err
+	}
+
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		return "", fmt.Errorf("provideroauth: start loopback listener: %w", err)
+	}
+	defer func() { _ = listener.Close() }()
+	callbackURL := fmt.Sprintf("http://%s/callback", listener.Addr().String())
+
+	codeCh := make(chan string, 1)
+	errCh := make(chan error, 1)
+	server := &http.Server{Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/callback" {
+			http.NotFound(w, r)
+			return
+		}
+		if code := strings.TrimSpace(r.URL.Query().Get("code")); code != "" {
+			_, _ = io.WriteString(w, "OpenRouter authorization complete. You may close this window.")
+			select {
+			case codeCh <- code:
+			default:
+			}
+			return
+		}
+		w.WriteHeader(http.StatusBadRequest)
+		_, _ = io.WriteString(w, "Authorization failed. You may close this window.")
+		select {
+		case errCh <- errors.New("provideroauth: callback missing authorization code"):
+		default:
+		}
+	})}
+	go func() { _ = server.Serve(listener) }()
+	defer func() {
+		shutdownCtx, cancelShutdown := context.WithTimeout(context.Background(), time.Second)
+		defer cancelShutdown()
+		_ = server.Shutdown(shutdownCtx)
+	}()
+
+	authURL := base + openRouterAuthPath + "?" + url.Values{
+		"callback_url":          {callbackURL},
+		"code_challenge":        {pkce.Challenge},
+		"code_challenge_method": {oauth.MethodS256},
+	}.Encode()
+	if opts.Out != nil {
+		fmt.Fprintf(opts.Out, "Open this URL to authorize OpenRouter:\n  %s\n", authURL)
+	}
+	if opts.OpenBrowser != nil {
+		if err := opts.OpenBrowser(authURL); err != nil {
+			return "", fmt.Errorf("provideroauth: open authorization URL: %w", err)
+		}
+	}
+
+	var code string
+	select {
+	case code = <-codeCh:
+	case err := <-errCh:
+		return "", err
+	case <-ctx.Done():
+		return "", fmt.Errorf("provideroauth: timed out waiting for OpenRouter authorization: %w", ctx.Err())
+	}
+
+	return openRouterExchange(ctx, client, base, code, pkce.Verifier)
+}
+
+// openRouterExchange swaps the authorization code + PKCE verifier for an API key.
+func openRouterExchange(ctx context.Context, client *http.Client, base, code, verifier string) (string, error) {
+	payload, err := json.Marshal(map[string]string{
+		"code":                  code,
+		"code_verifier":         verifier,
+		"code_challenge_method": oauth.MethodS256,
+	})
+	if err != nil {
+		return "", err
+	}
+	request, err := http.NewRequestWithContext(ctx, http.MethodPost, base+openRouterKeyExchangePath, bytes.NewReader(payload))
+	if err != nil {
+		return "", err
+	}
+	request.Header.Set("Content-Type", "application/json")
+	request.Header.Set("Accept", "application/json")
+
+	response, err := client.Do(request)
+	if err != nil {
+		return "", fmt.Errorf("provideroauth: openrouter key exchange: %w", err)
+	}
+	defer func() { _ = response.Body.Close() }()
+	body, _ := io.ReadAll(io.LimitReader(response.Body, openRouterMaxBody))
+	if response.StatusCode < http.StatusOK || response.StatusCode >= http.StatusMultipleChoices {
+		return "", fmt.Errorf("provideroauth: openrouter key exchange returned HTTP %d", response.StatusCode)
+	}
+	var parsed struct {
+		Key string `json:"key"`
+	}
+	if err := json.Unmarshal(body, &parsed); err != nil {
+		return "", fmt.Errorf("provideroauth: decode openrouter key response: %w", err)
+	}
+	key := strings.TrimSpace(parsed.Key)
+	if key == "" {
+		return "", errors.New("provideroauth: openrouter returned an empty key")
+	}
+	return key, nil
+}

internal/provideroauth/openrouter_test.go

@@ -0,0 +1,131 @@
+package provideroauth
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+)
+
+// simulateBrowser returns an OpenBrowser func that authorizes by GETting the
+// callback_url with the given code (or no code), mimicking OpenRouter's redirect.
+// It also asserts the PKCE params are present on the authorize URL.
+func simulateBrowser(t *testing.T, code string) func(string) error {
+	t.Helper()
+	return func(authURL string) error {
+		u, err := url.Parse(authURL)
+		if err != nil {
+			return err
+		}
+		q := u.Query()
+		if q.Get("code_challenge") == "" || q.Get("code_challenge_method") != "S256" {
+			t.Fatalf("authorize URL missing PKCE: %s", authURL)
+		}
+		cb := q.Get("callback_url")
+		if cb == "" {
+			t.Fatalf("authorize URL missing callback_url: %s", authURL)
+		}
+		target := cb
+		if code != "" {
+			target = cb + "?code=" + url.QueryEscape(code)
+		}
+		resp, err := http.Get(target) //nolint:noctx // test loopback
+		if err != nil {
+			return err
+		}
+		_ = resp.Body.Close()
+		return nil
+	}
+}
+
+func TestOpenRouterLoginMintsKey(t *testing.T) {
+	var gotCode, gotVerifier, gotMethod string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/api/v1/auth/keys" || r.Method != http.MethodPost {
+			w.WriteHeader(http.StatusNotFound)
+			return
+		}
+		var body map[string]string
+		_ = json.NewDecoder(io.LimitReader(r.Body, 1<<16)).Decode(&body)
+		gotCode, gotVerifier, gotMethod = body["code"], body["code_verifier"], body["code_challenge_method"]
+		w.Header().Set("Content-Type", "application/json")
+		_ = json.NewEncoder(w).Encode(map[string]string{"key": "sk-or-mock-123"})
+	}))
+	defer srv.Close()
+
+	key, err := OpenRouterLogin(context.Background(), OpenRouterOptions{
+		BaseURL:     srv.URL,
+		HTTPClient:  srv.Client(),
+		OpenBrowser: simulateBrowser(t, "TESTCODE"),
+	})
+	if err != nil {
+		t.Fatalf("OpenRouterLogin: %v", err)
+	}
+	if key != "sk-or-mock-123" {
+		t.Fatalf("key = %q, want sk-or-mock-123", key)
+	}
+	if gotCode != "TESTCODE" || gotVerifier == "" || gotMethod != "S256" {
+		t.Fatalf("exchange body: code=%q verifier=%q method=%q", gotCode, gotVerifier, gotMethod)
+	}
+}
+
+func TestOpenRouterLoginMissingCodeErrors(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNotFound)
+	}))
+	defer srv.Close()
+	_, err := OpenRouterLogin(context.Background(), OpenRouterOptions{
+		BaseURL:     srv.URL,
+		HTTPClient:  srv.Client(),
+		OpenBrowser: simulateBrowser(t, ""), // callback with no code
+	})
+	if err == nil {
+		t.Fatal("a callback without a code should error")
+	}
+}
+
+func TestOpenRouterLoginExchangeFailureErrors(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusForbidden) // exchange rejected
+	}))
+	defer srv.Close()
+	_, err := OpenRouterLogin(context.Background(), OpenRouterOptions{
+		BaseURL:     srv.URL,
+		HTTPClient:  srv.Client(),
+		OpenBrowser: simulateBrowser(t, "C"),
+	})
+	if err == nil {
+		t.Fatal("a non-2xx exchange should error")
+	}
+}
+
+func TestOpenRouterLoginEmptyKeyErrors(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = io.WriteString(w, `{"key":""}`)
+	}))
+	defer srv.Close()
+	_, err := OpenRouterLogin(context.Background(), OpenRouterOptions{
+		BaseURL:     srv.URL,
+		HTTPClient:  srv.Client(),
+		OpenBrowser: simulateBrowser(t, "C"),
+	})
+	if err == nil || !strings.Contains(err.Error(), "empty key") {
+		t.Fatalf("empty key should error, got %v", err)
+	}
+}
+
+func TestOpenRouterLoginBrowserErrorPropagates(t *testing.T) {
+	_, err := OpenRouterLogin(context.Background(), OpenRouterOptions{
+		BaseURL:     "http://127.0.0.1:1",
+		OpenBrowser: func(string) error { return errors.New("no browser") },
+	})
+	if err == nil {
+		t.Fatal("a browser-open failure should propagate")
+	}
+}

internal/providers/anthropic/provider.go

@@ -87,6 +87,10 @@ type Options struct {
 	CustomHeaders   map[string]string
 	HTTPClient      *http.Client
 	UserAgent       string
+	// OAuthResolver, when set, supplies an OAuth bearer credential per request and
+	// is preferred over APIKey; a nil resolver (or one that yields ok=false) uses
+	// the API key. See providerio.SendWithAuthRetry.
+	OAuthResolver providerio.TokenResolver
 	// StreamIdleTimeout aborts the stream if no data arrives for this long.
 	// Zero uses defaultStreamIdleTimeout.
 	StreamIdleTimeout time.Duration
@@ -104,6 +108,7 @@ type Provider struct {
 	authScheme        string
 	authHeaderValue   string
 	customHeaders     map[string]string
+	oauthResolver     providerio.TokenResolver
 	httpClient        *http.Client
 	userAgent         string
 	streamIdleTimeout time.Duration
@@ -142,6 +147,7 @@ func New(options Options) (*Provider, error) {
 		authScheme:        strings.TrimSpace(options.AuthScheme),
 		authHeaderValue:   strings.TrimSpace(options.AuthHeaderValue),
 		customHeaders:     providerio.CopyHeaders(options.CustomHeaders),
+		oauthResolver:     options.OAuthResolver,
 		httpClient:        providerio.HTTPClient(options.HTTPClient),
 		userAgent:         options.UserAgent,
 		streamIdleTimeout: idleTimeout,
@@ -176,24 +182,26 @@ func (provider *Provider) stream(ctx context.Context, body []byte, events chan<-
 	streamCtx, cancelStream := context.WithCancel(ctx)
 	defer cancelStream()
 
-	response, err := providerio.SendWithRetry(streamCtx, provider.httpClient, http.MethodPost, provider.baseURL+"/v1/messages", body, func(request *http.Request) {
-		request.Header.Set("Content-Type", "application/json")
-		request.Header.Set("anthropic-version", provider.version)
-		if provider.beta != "" {
-			request.Header.Set("anthropic-beta", provider.beta)
-		}
-		if provider.userAgent != "" {
-			request.Header.Set("User-Agent", provider.userAgent)
-		}
-		providerio.ApplyAuthHeaders(request, providerio.AuthHeaders{
+	response, err := providerio.SendWithAuthRetry(streamCtx, provider.httpClient, http.MethodPost, provider.baseURL+"/v1/messages", body,
+		providerio.AuthHeaders{
 			APIKey:            provider.apiKey,
 			DefaultAuthHeader: "x-api-key",
 			AuthHeader:        provider.authHeader,
 			AuthScheme:        provider.authScheme,
 			AuthHeaderValue:   provider.authHeaderValue,
 			CustomHeaders:     provider.customHeaders,
-		})
-	}, 0)
+		},
+		provider.oauthResolver,
+		func(request *http.Request) {
+			request.Header.Set("Content-Type", "application/json")
+			request.Header.Set("anthropic-version", provider.version)
+			if provider.beta != "" {
+				request.Header.Set("anthropic-beta", provider.beta)
+			}
+			if provider.userAgent != "" {
+				request.Header.Set("User-Agent", provider.userAgent)
+			}
+		}, 0)
 	if err != nil {
 		providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{Type: zeroruntime.StreamEventError, Error: provider.redact("provider stream error: " + err.Error())})
 		return

internal/providers/factory.go

@@ -10,6 +10,7 @@ import (
 	"github.com/Gitlawb/zero/internal/providers/anthropic"
 	"github.com/Gitlawb/zero/internal/providers/gemini"
 	"github.com/Gitlawb/zero/internal/providers/openai"
+	"github.com/Gitlawb/zero/internal/providers/providerio"
 	"github.com/Gitlawb/zero/internal/zeroruntime"
 )
 
@@ -18,6 +19,10 @@ type Options struct {
 	UserAgent     string
 	HTTPClient    *http.Client
 	ModelRegistry *modelregistry.Registry
+	// OAuthResolver, when set, lets the provider authenticate model calls with an
+	// OAuth bearer token (preferred over the API key). nil => API-key auth only.
+	// Applied to the OpenAI and Anthropic providers.
+	OAuthResolver providerio.TokenResolver
 }
 
 // New creates a runtime provider for a resolved provider profile.
@@ -37,9 +42,11 @@ func New(profile config.ProviderProfile, options Options) (zeroruntime.Provider,
 			AuthScheme:      profile.AuthScheme,
 			AuthHeaderValue: profile.AuthHeaderValue,
 			CustomHeaders:   profile.CustomHeaders,
+			OAuthResolver:   options.OAuthResolver,
 			MaxTokens:       resolved.maxOutputTokens,
 			HTTPClient:      options.HTTPClient,
 			UserAgent:       options.UserAgent,
+			ParseThinkTags:  parseThinkTagsForProfile(profile, resolved),
 		})
 	case config.ProviderKindAnthropic, config.ProviderKindAnthropicCompat:
 		return anthropic.New(anthropic.Options{
@@ -50,6 +57,7 @@ func New(profile config.ProviderProfile, options Options) (zeroruntime.Provider,
 			AuthScheme:      profile.AuthScheme,
 			AuthHeaderValue: profile.AuthHeaderValue,
 			CustomHeaders:   profile.CustomHeaders,
+			OAuthResolver:   options.OAuthResolver,
 			MaxTokens:       resolved.maxOutputTokens,
 			HTTPClient:      options.HTTPClient,
 			UserAgent:       options.UserAgent,
@@ -72,6 +80,40 @@ func New(profile config.ProviderProfile, options Options) (zeroruntime.Provider,
 	}
 }
 
+func parseThinkTagsForProfile(profile config.ProviderProfile, resolved resolvedProfile) bool {
+	if profile.ParseThinkTags != nil {
+		return *profile.ParseThinkTags
+	}
+	if resolved.providerKind != config.ProviderKindOpenAICompatible {
+		return false
+	}
+	return modelMayEmitThinkTags(resolved.apiModel)
+}
+
+func modelMayEmitThinkTags(model string) bool {
+	model = strings.ToLower(strings.TrimSpace(model))
+	for _, marker := range []string{
+		"deepseek-r1",
+		"deepseek-reasoner",
+		"gpt-oss",
+		"glm-z1",
+		"kimi-k2-thinking",
+		"magistral",
+		"minimax-m3",
+		"nemotron",
+		"qwen3",
+		"qwq",
+		"reasoner",
+		"reasoning",
+		"thinking",
+	} {
+		if strings.Contains(model, marker) {
+			return true
+		}
+	}
+	return false
+}
+
 type resolvedProfile struct {
 	providerKind    config.ProviderKind
 	apiModel        string

internal/providers/factory_test.go

@@ -108,6 +108,33 @@ func TestNewSupportsOpenAIProviderKind(t *testing.T) {
 	}
 }
 
+func TestParseThinkTagsForProfileUsesConservativeDefaultsAndOverride(t *testing.T) {
+	openAICompatible := resolvedProfile{providerKind: config.ProviderKindOpenAICompatible, apiModel: "qwen3-coder:480b"}
+	if !parseThinkTagsForProfile(config.ProviderProfile{}, openAICompatible) {
+		t.Fatal("qwen3 OpenAI-compatible model should parse inline think tags by default")
+	}
+
+	generic := resolvedProfile{providerKind: config.ProviderKindOpenAICompatible, apiModel: "factory-model"}
+	if parseThinkTagsForProfile(config.ProviderProfile{}, generic) {
+		t.Fatal("generic OpenAI-compatible model should preserve literal think tags by default")
+	}
+
+	official := resolvedProfile{providerKind: config.ProviderKindOpenAI, apiModel: "gpt-4.1"}
+	if parseThinkTagsForProfile(config.ProviderProfile{}, official) {
+		t.Fatal("official OpenAI model should preserve literal think tags by default")
+	}
+
+	enabled := true
+	if !parseThinkTagsForProfile(config.ProviderProfile{ParseThinkTags: &enabled}, generic) {
+		t.Fatal("explicit parseThinkTags=true should enable inline think parsing")
+	}
+
+	disabled := false
+	if parseThinkTagsForProfile(config.ProviderProfile{ParseThinkTags: &disabled}, openAICompatible) {
+		t.Fatal("explicit parseThinkTags=false should disable inline think parsing")
+	}
+}
+
 func TestNewResolvesKnownModelToAPIModelAndProvider(t *testing.T) {
 	transport := &captureTransport{
 		responseBody: "data: {\"type\":\"message_stop\"}\n\n",