fix(tools): reject mixed-root freeform patches

* fix(tools): make apply_patch tolerant and re-expose edit_file

Head-to-head benchmarking against Grok Build on grok-4.6 (3 tasks × 3 runs)
showed Zero solving every task but spending 2.7× the tokens and 2.3× the
time on the multi-file feature task. Every one of the 20 apply_patch calls
in those runs failed, after which the model degraded to whole-file
write_file rewrites and read→write verification loops.

Root causes and fixes:

- The sandbox and the tool both rejected an absolute path that lies inside
  the workspace ("must stay inside the workspace"). Models routinely echo
  the absolute path read_file showed them. Absolute paths now flow through
  the normal workspace-scope validation (inside → allowed, outside → still
  denied); unified-diff headers are rewritten to a/ b/ relative form before
  git apply, and platform symlink prefixes (/var → /private/var) are
  normalised the same way the other file tools do.
- The structured parser demanded a byte-exact "*** Begin Patch" /
  "*** End Patch"; grok-4.6 writes "*** Begin Patch ***". Decorated marker
  spellings are accepted, and a unified range after "@@" ("-12,4 +12,6",
  optionally with a heading) no longer becomes a literal context search.
- Parse errors now carry a one-line format reminder so a failed call is
  recoverable in one retry instead of a format-guessing loop.
- edit_file (exact search/replace with uniqueness guard, CRLF and fuzzy
  fallbacks) is advertised to the model again alongside apply_patch, and
  the apply_patch description shows the structured format.
- Writers (edit_file, write_file, apply_patch) recorded a file's line total
  with lineCount, which is one higher than read_file's count for a file
  ending in a newline. RecordSeenRange resets every observation when the
  total changes, so a partial read_file after a successful edit silently
  discarded whole-file knowledge and the next edit was refused with
  "content that has not been read exactly in this session". All writers
  now record the same total read_file reports (trackedLineTotal).
- read_file's padded "  N | " line prefix was ~19% of every read (about
  1.5k tokens per 800-line file) and was re-sent on every later call. It is
  now the compact "N→" prefix models already know; nothing parsed the old
  form.
- The editing-discipline prompt steers: edit_file for a targeted change,
  apply_patch for multi-hunk/multi-file changes, write_file only for new
  files or full rewrites; a successful edit result is confirmation, so the
  file is not re-read to verify it.

Tests: regression tests for decorated markers, writer/reader line-total
agreement (edit → partial read → edit far away still succeeds), range hunk headers,
absolute in-workspace paths (structured + unified), outside-workspace
rejection, header-line-only relativisation, and tool visibility; the
prompt and tool-budget tests updated to the new contract.

Benchmark (grok-4.6, 3 tasks x 3 runs, harness in demo/bench-zero-vs-grok):
Zero 0.8.0 617 s / 1,527k tokens -> with this change 346 s / 493k tokens;
Grok Build 407 s / 713k. Every run of every configuration solved its task.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* fix(tools): keep CRLF line endings when relativizing patch headers

relativizeUnifiedPatchPaths split on a normalized "\n" and rejoined with
"\n", so any CRLF patch that needed a header rewrite lost its line endings
everywhere; git apply could then fail to match a CRLF file. Split on "\n"
only and carry each line's trailing "\r" through, including on rewritten
headers.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* fix(sandbox): share the structured-patch classifier with apply_patch

Review follow-ups for #956:

- The tool accepted decorated structured markers ("***Begin Patch") that
  the sandbox's applyPatchPaths did not recognise, so for that spelling the
  boundary scanned the patch as a unified diff, extracted no targets and
  validated nothing. The marker classifier now lives in the sandbox package
  (StructuredPatchMarker / IsStructuredPatch) and the tool delegates to it,
  so both sides accept exactly the same set; tests cover inside, traversal
  and outside targets for the no-space spelling at the boundary.
- Document the containment model at the apply site: structured patches are
  applied through an opened os.Root (descriptor-relative, no-follow);
  unified diffs keep the pre-existing git-apply pathname flow, which the
  absolute-path rewrite does not widen (they become the same root-relative
  form relative paths always used).
- OpenAI addendum: the one-file-per-call rule names read_file, edit_file and
  write_file explicitly and allows a single multi-file apply_patch.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* test(sandbox): compare slash-normalised patch paths so the check passes on Windows

structuredPatchHeaderPaths normalises separators to "/", so the absolute
outside-workspace path in the boundary test must be compared in its slash
form; on Windows the backslash original never matched and the Smoke job
failed.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* test(sandbox): validate the parsed patch path at the scope boundary

For each accepted marker spelling, pass the exact path applyPatchRequestPaths
produced to scope.validate: an outside path must be denied and an inside
path accepted, so a separator-handling regression between the parser and the
scope cannot slip past the test.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* fix(tools): apply unified diffs in-process through the workspace root

Review follow-up for #956. Unified diffs were validated by pathname and then
handed to git apply, which reopened the targets by name — a check-to-use
window a symlink swap could exploit — and the absolute-path rewrite added in
this PR normalised `diff --git` headers with strings.Fields, which splits a
git C-quoted path containing whitespace.

Both go away by not shelling out at all: parseUnifiedPatch translates a
unified diff into the same operations a structured patch produces, and both
formats are applied by applyPatchOperations through os.OpenRoot — every
stat, read, create and write is descriptor-relative and refuses to follow a
link out of the root. git is no longer required by apply_patch.

Unified-diff support: modifications, creations (--- /dev/null), deletions
(+++ /dev/null), multiple hunks per file, git "rename from/to" (a move,
hunks optional) and "copy from/to" (a new copy operation whose destination
inherits only the tracker credit the source had), "\ No newline at end of
file" on either side, a/ b/ prefixes, C-quoted paths, CRLF patches, and
git's diff/index/mode lines. Hunks are placed at their "@@ -a,b" range when
the expected lines match there and located by context otherwise (so a
stale range still applies and duplicate blocks are disambiguated by the
range). Binary patches are rejected.

Removed: the git apply flow, relativizeUnifiedPatchPaths,
recheckPatchWriteTargets, missingPatchTargets, completeCreatedPatchTargets
and recordCreatedPatchTargets. validatePatchPaths/changedFilesFromPatch stay
for mutation-target listing.

Tests: the existing unified-diff suite now runs through the in-process
applier unchanged; new coverage for quoted whitespace paths (inside applies,
outside is refused untouched), a workspace path swapped for a symlink that
escapes the root (both formats refused, outside file unmodified), create +
delete + no-newline markers, range hint vs context fallback, rename with a
hunk, and binary/empty rejection.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* fix(tools): harden unified-diff parsing and cover the copy operation

Review follow-ups for #956 (in-process unified applier):

- A hunk that ends before its declared line counts is reported as
  malformed instead of silently absorbing the next file's ---/+++ header
  pair (which then failed later against the wrong file). Both shapes are
  caught: leftover counts at a header or at end of input, and a --- line
  directly followed by +++ inside a hunk. The element after a patch's final
  newline is no longer counted as an empty context line, so a truncated
  hunk cannot look complete.
- "\ No newline at end of file" may only follow a file's final hunk; a
  marker before another hunk is rejected rather than leaking into that
  hunk's result.
- Zero-context insertions (git diff -U0) are documented as
  position-trusting by design, matching git apply without fuzz; hunks with
  context are verified at the range before it is used.

Tests: copy from/to (source kept, destination created with the hunk
applied and tracked with the source's whole-file state; existing
destination refused untouched; copy onto itself refused), over-declared and
truncated hunk counts, and the no-newline marker before vs after the final
hunk.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* fix(tools): require an @@ line before treating ---/+++ inside a hunk as a file boundary

A removed "-- x" line directly followed by an added "++ y" line is valid
hunk content that also matches the ---/+++ header shape; the boundary check
now additionally requires the following line to be a hunk header, and a
regression test keeps such a pair intact. End-of-input strictness for a hunk
cut short is documented as deliberate: applying a truncated hunk would make
a partial change (removals without their replacements).

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* refactor(tools): share one line-count implementation between reader and writer

sourceLineCount and trackedLineTotal computed the same count; keeping two
copies invites exactly the reader/writer drift this PR fixed. The reader now
delegates to trackedLineTotal, which carries the tracker contract.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* fix(tools): verify a unified deletion's expected content before removing the file

A unified diff's "+++ /dev/null" hunks state the content being removed, but
the in-process applier dropped them and deleted unconditionally, so a stale
deletion removed a file whose current content the patch never described.
Unified deletions now keep their hunks, require at least one, and run them
through the same verifier as updates: the hunks must match the current file
and leave nothing behind, otherwise the deletion is refused and the file is
untouched. A structured "*** Delete File" keeps its unconditional meaning.

Hardening from the same review: every non-create change re-reads its source
through the opened root immediately before commit and refuses to proceed if
the bytes differ from what was planned.

Tests: matching deletion, stale deletion (file byte-for-byte unchanged),
partial deletion, header-only deletion, multi-hunk deletion with one stale
hunk (nothing removed) and all-good hunks, structured delete unchanged, and
a source changed between planning and commit for update and delete.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* test(tools): a move with a missing source is refused before publishing

The pre-commit recheck now refuses a move whose source vanished after
planning instead of publishing the destination and then failing; update the
test to the safer contract (error names the recheck, nothing is created).

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* fix(tools): byte-exact unified deletions and git's header-only empty-file forms

Review follow-ups for #956:

- A unified deletion is verified byte for byte: the removed lines (with the
  removed side's "\ No newline at end of file" honoured) must equal the
  current file exactly, with only the file's own line-ending style
  normalised. None of the whitespace tolerance used to locate update hunks
  applies, and a whitespace-only remainder no longer passes; a deletion is
  not recoverable, so it fails closed.
- git describes an empty file's deletion or creation with header lines only
  ("diff --git", "deleted file mode"/"new file mode", "index") and no
  hunks. Both forms are recognised: the deletion is applied only when the
  current file is empty, the creation writes an empty file, and they compose
  with hunk-carrying files in the same patch.
- The pre-commit recheck test also covers the copy operation and asserts no
  destination is created on refusal.

Tests: whitespace/indentation/blank-line/space-only/missing-newline
mismatches all refused with the file unchanged, matching no-newline marker
and CRLF file accepted, header-only deletion of a non-empty file refused,
multi-file patch with header-only delete + create + a normal hunk.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* test(tools): remove the move source after planning via a deterministic hook

The refused-move test now creates source.txt, plans the move, and removes
the file through a test-only pre-commit hook (structuredPatchBeforeCommit)
so it exercises the post-planning disappearance path rather than a source
that was never there. Assertions unchanged: refused before publishing, no
destination created.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* test(tui): read_file fixtures use the compact N→ prefix

Three TUI fixtures still built fake read_file output in the legacy
"  N | text" shape; they pass either way but pinned an outdated contract.
They now mirror what appendReadFileRange emits, and the shape comment and
the expanded-card assertion are updated.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

* fix(tools): name the committed files when a patch is partially applied

Review follow-up for #956. When a later change in a multi-file patch fails
(for example the pre-commit recheck refuses a file that changed after
planning), the error now lists exactly which files were already committed
and states that the rest are unchanged, instead of a generic "partially
applied" warning. The model can then re-read only what actually changed.

Test: a three-file structured patch whose second file is altered after
planning fails with "already committed: first.txt", first.txt holds the
patched content, and the other two files are untouched.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

---------

Co-authored-by: Claude Fable 5 <[email protected]>

.release-please-manifest.json

@@ -1 +1 @@
-{".":"0.7.0"}
+{".":"0.8.0"}

AGENTS.md

@@ -91,6 +91,14 @@ These classes drive multi-round reviews. Fix them before requesting review:
   final-component-only no-follow is insufficient. On multi-step setup, roll back
   only what this run created; never destroy pre-existing resources you did
   not create; never report success when cleanup or unlock failed.
+- **Normalize before matching:** Any transform that REMOVES bytes without
+  leaving a gap is also a reassembler, so it has to run before whatever matches
+  on the result. Redacting by shape and then stripping control bytes lets a
+  credential split by a NUL, an ESC or a C1 byte pass the patterns as two
+  fragments and be rejoined on the way out; comparing a path against a form
+  produced by the same resolver the kernel just used makes a redirect agree with
+  itself. Strip, decode, or canonicalize first, then match. The unsplit value
+  passing is not evidence, so the test needs a split case.
 - **Atomic shared state:** Write a complete temporary file, then atomically
   replace the destination so concurrent readers never see a partial write.
   Exclusive create or a write lock alone is not enough for readers. Serialize
@@ -103,3 +111,42 @@ These classes drive multi-round reviews. Fix them before requesting review:
   shipped. Wire advertised entry points or shrink the claim. Do not bundle
   unrelated fixes. Do not widen security allowlists by name alone; check
   classification and side effects too.
+- **Host tool version floors:** Zero shells out to `git` and other host tools,
+  and the project does not declare a minimum version for any of them. A flag,
+  subcommand, or config key that is not long-established therefore raises that
+  floor silently, and the failure on an older host is an unhelpful usage error
+  rather than a clear message. Before adding one, check when it landed and say
+  so where a caller would look. Record the floor for the exact subcommand you
+  call, not for the flag in general: `--end-of-options` reached Git's shared
+  parser in 2.24, but `git rev-parse` only accepted it from 2.30, and
+  `git checkout` and `git reset` later still. Likewise `--show-current` is
+  `git branch` 2.22, and `branch.autoSetupMerge=inherit` is 2.35. Then either
+  keep a fallback for older versions or gate the call. A test that depends on a
+  newer feature must skip below its floor instead of failing, and say which
+  version it needs.
+- **Prove the test fails without the change:** A regression test earns its
+  place only if it fails on the unfixed code, for the reason it claims. Run it
+  both ways and quote the failure in the PR. The recurring miss is not a
+  missing test but a test that never reaches the behavior it names, because an
+  earlier guard rejects the input first, so it passes with and without the fix.
+  When a test targets a specific layer, call that layer directly rather than
+  relying on a public entry point that may refuse earlier.
+- **Hermetic tests:** Tests must not read or write the developer's real config,
+  cache, or state directories. Redirect every root the code under test
+  resolves, not just config. `os.UserConfigDir` and `os.UserCacheDir` read
+  `XDG_CONFIG_HOME` and `XDG_CACHE_HOME` only on Linux and the BSDs. On macOS
+  they derive from `HOME`, and on Windows from `%AppData%` and `%LocalAppData%`.
+  Setting the XDG variables alone still leaves a macOS run writing to the real
+  home, so set `HOME` as well, or take the directory as a parameter. Apply it to
+  every test that reaches the same storage, not only the one where it was first
+  needed; a test that passes on a clean machine and pollutes a real one is a
+  blocker.
+- **Error codes vary by platform and by flag combination:** A check written
+  against the code one target returns can be silently inert on another while
+  still looking correct. `openat(O_DIRECTORY|O_NOFOLLOW)` on a symlink may
+  report `ENOTDIR` or `ELOOP` depending on the platform, because the kernel can
+  reject the directory mismatch before it ever resolves the link; accept both
+  rather than assuming the one POSIX names. On Windows, `\\?\` and `\\.\`
+  prefixes are not UNC paths, and an `NtCreateFile` information class must match
+  the struct actually passed. Confirm the code each supported target returns
+  instead of reasoning from the man page.

CHANGELOG.md

@@ -6,6 +6,27 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 aims to follow [Semantic Versioning](https://semver.org/spec/v2.0.0.html) once the first release is
 tagged. Until then, source builds report the version `dev`.
 
+## [0.8.0](https://github.com/Gitlawb/zero/compare/v0.7.0...v0.8.0) (2026-08-21)
+
+
+### Features
+
+* **security:** path-jail primitive, credential-store locking, worktree git hardening ([#891](https://github.com/Gitlawb/zero/issues/891)) ([060d38c](https://github.com/Gitlawb/zero/commit/060d38ce716feb7c5b6657b082cd35cb8dda3d75))
+* **update:** recognise Homebrew installs and add mise, go install docs ([#910](https://github.com/Gitlawb/zero/issues/910)) ([01c3498](https://github.com/Gitlawb/zero/commit/01c3498205e69d26e5f929225f9455b276444f39))
+* use Exa as default search provider ([#926](https://github.com/Gitlawb/zero/issues/926)) ([1ec7219](https://github.com/Gitlawb/zero/commit/1ec7219aee7b2840481ab0905f131644e27d2a4e))
+* **zerogit:** auto-create a conventional branch before push/pr on default branch ([#671](https://github.com/Gitlawb/zero/issues/671)) ([d065467](https://github.com/Gitlawb/zero/commit/d065467cd3ec3ed91c5dc60554c36fc4b4d6de4c))
+
+
+### Bug Fixes
+
+* **acp:** three defects a desktop ACP client hits ([#915](https://github.com/Gitlawb/zero/issues/915)) ([a78c6c3](https://github.com/Gitlawb/zero/commit/a78c6c357e1d21146d7cd2e8030a754e06f7f1f5))
+* bump Go to 1.26.6 for stdlib vulnerability fixes ([#903](https://github.com/Gitlawb/zero/issues/903)) ([dc15e82](https://github.com/Gitlawb/zero/commit/dc15e822987d8d7de467c62c375518f435b74d8c))
+* **daemon:** clean up child after startup timeout ([#774](https://github.com/Gitlawb/zero/issues/774)) ([9c29209](https://github.com/Gitlawb/zero/commit/9c292092a26c9092fd873d072b0af1b0d9d39ef0))
+* **dictation:** redact API keys from streaming transcriber errors ([#852](https://github.com/Gitlawb/zero/issues/852)) ([64a783b](https://github.com/Gitlawb/zero/commit/64a783b08caa2c7b21f188033b9ed84a14e00e84))
+* **modelregistry:** expose reasoning effort for DeepSeek V4 models ([#931](https://github.com/Gitlawb/zero/issues/931)) ([90dcfd1](https://github.com/Gitlawb/zero/commit/90dcfd127e8a6d9902ec9f4e72f6d03fef1a0fc6))
+* **providers:** discover ChatGPT capabilities ([#890](https://github.com/Gitlawb/zero/issues/890)) ([2d2450e](https://github.com/Gitlawb/zero/commit/2d2450e9a744349f0d01b1d4e9ba29c24ba5650d))
+* **sandbox:** normalize launcher names before the command-prefix denylist ([#934](https://github.com/Gitlawb/zero/issues/934)) ([6edf9a8](https://github.com/Gitlawb/zero/commit/6edf9a8b78dc030dc44598919db1c7fa9d4f809a))
+
 ## [0.7.0](https://github.com/Gitlawb/zero/compare/v0.6.0...v0.7.0) (2026-08-10)
 
 

README.md

@@ -6,7 +6,7 @@
 
 <p align="center">
   <a href="LICENSE"><img alt="license" src="https://img.shields.io/badge/license-MIT-blue"></a>
-  <img alt="Go 1.26.5+" src="https://img.shields.io/badge/Go-1.26.5+-00ADD8?logo=go&logoColor=white">
+  <img alt="Go 1.26.6+" src="https://img.shields.io/badge/Go-1.26.6+-00ADD8?logo=go&logoColor=white">
   <img alt="25+ providers" src="https://img.shields.io/badge/providers-25+-34E2EA">
   <a href="https://discord.gg/CaQDS6wdFn"><img alt="Discord" src="https://img.shields.io/badge/Discord-join-5865F2?logo=discord&logoColor=white"></a>
   <br>
@@ -76,7 +76,7 @@ irm https://raw.githubusercontent.com/Gitlawb/zero/main/scripts/install.ps1 | ie
 
 ### From source
 
-Source builds require Go 1.26.5+.
+Source builds require Go 1.26.6+.
 
 ```bash
 git clone https://github.com/Gitlawb/zero.git
@@ -371,9 +371,13 @@ go run ./cmd/zero-perf-bench
 
 Experimental: `ZERO_OPENAI_TURN_SESSION=1` enables the optimized OpenAI turn
 session (background connection prewarm + request-prefix telemetry) for headless
-`zero exec` runs against official OpenAI profiles. Off by default; `0`/`false`
-disable. A/B-benchmark it by running the same `zero-perf-bench` suite with the
-variable unset and set.
+`zero exec` runs against official OpenAI profiles. Off by default; `0`, `false`,
+or `off` disable it. A/B-benchmark it by running the same `zero-perf-bench` suite
+with the variable unset and set.
+
+Native ChatGPT Responses sessions are enabled by default. Set
+`ZERO_CHATGPT_TURN_SESSION=0`, `false`, or `off` to restore stateless HTTP/SSE
+transport.
 
 ### Code Quality and Security Checks
 

README_ZH.md

@@ -6,7 +6,7 @@
 
 <p align="center">
   <a href="LICENSE"><img alt="license" src="https://img.shields.io/badge/license-MIT-blue"></a>
-  <img alt="Go 1.26.5+" src="https://img.shields.io/badge/Go-1.26.5+-00ADD8?logo=go&logoColor=white">
+  <img alt="Go 1.26.6+" src="https://img.shields.io/badge/Go-1.26.6+-00ADD8?logo=go&logoColor=white">
   <img alt="25+ providers" src="https://img.shields.io/badge/providers-25+-34E2EA">
   <a href="https://discord.gg/CaQDS6wdFn"><img alt="Discord" src="https://img.shields.io/badge/Discord-join-5865F2?logo=discord&logoColor=white"></a>
   <br>
@@ -57,7 +57,7 @@ irm https://raw.githubusercontent.com/Gitlawb/zero/main/scripts/install.ps1 | ie
 
 ### 从源码构建
 
-源码构建需要 Go 1.26.5+。
+源码构建需要 Go 1.26.6+。
 
 ```bash
 git clone https://github.com/Gitlawb/zero.git

SECURITY.md

@@ -33,4 +33,4 @@ Please include, where possible:
   depend on a user explicitly disabling the sandbox (`--skip-permissions-unsafe`), are generally
   out of scope — but please report anything you are unsure about.
 - Zero sends no telemetry. Network calls go to the model/tool providers you configure (and, for
-  keyless web search, to the documented Firecrawl endpoint — see the README).
+  keyless web search, to Exa's hosted MCP endpoint at `https://mcp.exa.ai/mcp`).

docs/INSTALL.md

@@ -1,14 +1,30 @@
 # Installing Zero
 
-Zero is distributed as:
+Pick whichever fits how you already install things. None of these is the
+blessed one.
 
-- an npm package, `@gitlawb/zero`
-- release archives on GitHub Releases
-- source builds with Go 1.26.5+
+| Method | Command | Self-update |
+| --- | --- | --- |
+| Install script (Linux, macOS) | `curl -fsSL https://raw.githubusercontent.com/Gitlawb/zero/main/scripts/install.sh \| bash` | `zero upgrade` |
+| Install script (Windows) | `irm https://raw.githubusercontent.com/Gitlawb/zero/main/scripts/install.ps1 \| iex` | `zero upgrade` |
+| npm | `npm install -g @gitlawb/zero` | `zero upgrade` (runs npm) |
+| Release archive | download from [Releases](https://github.com/Gitlawb/zero/releases) | `zero upgrade` |
+| mise | `mise use -g ubi:Gitlawb/zero` | `mise upgrade` |
+| `go install` | `go install github.com/Gitlawb/zero/cmd/zero@latest` | rerun the command |
+| Source | `go build -o zero ./cmd/zero` | rebuild |
 
-The install scripts download a platform-specific release archive and require a
-published GitHub Release for the requested version. The npm package is
-self-contained: the platform binary installs from the npm registry.
+`zero upgrade` follows whatever owns the binary, with one exception it cannot
+detect. It delegates to npm for an npm install, refuses outright for a Homebrew
+keg and names `brew upgrade zero`, and replaces the binary in place for
+everything else — including a mise-managed one, which is the exception.
+
+mise is the one case it cannot detect: a mise-managed binary is an ordinary
+standalone install on disk, so `zero upgrade` will replace it and leave mise
+describing a version that is no longer there. Use `mise upgrade` instead.
+
+Release archives are the substrate for most of the above: the install scripts
+and the npm fallback both download a platform archive from a published GitHub
+Release and verify its checksum.
 
 ## npm
 
@@ -111,6 +127,45 @@ Defaults:
 - Version: latest GitHub release
 - Install path: `%LOCALAPPDATA%\zero\bin\zero.exe`
 
+## mise
+
+[mise](https://mise.jdx.dev/) installs Zero straight from the GitHub Release
+archives through its `ubi` backend, so there is nothing extra to publish and no
+registry in the middle:
+
+```bash
+mise use -g ubi:Gitlawb/zero
+```
+
+Pin a version the same way you would any other tool:
+
+```bash
+mise use -g ubi:Gitlawb/[email protected]
+```
+
+Updates come from `mise upgrade`. `zero upgrade` also works, because a
+mise-managed binary is an ordinary standalone install, but then mise's records
+describe a version that is no longer on disk. Prefer `mise upgrade`.
+
+## go install
+
+```bash
+go install github.com/Gitlawb/zero/cmd/zero@latest
+```
+
+This builds from source, so it needs Go 1.26.6+ and it does not go through the
+release archives. Two consequences worth knowing before you pick it:
+
+- On Linux you also need the sandbox helper, which is a separate binary and is
+  not installed by this command. See
+  [Sandbox Helpers For Source Builds](#sandbox-helpers-for-source-builds).
+  Without it, native sandboxing is unavailable.
+- `zero upgrade` treats the result as a standalone install and will replace the
+  binary with a release build rather than rebuilding from source. If you chose
+  `go install` deliberately, rerun it instead.
+
+macOS and Windows need no extra helper.
+
 ## From Source
 
 ```bash
@@ -125,7 +180,7 @@ Build a local binary:
 go build -o zero ./cmd/zero
 ```
 
-Source builds require Go 1.26.5+.
+Source builds require Go 1.26.6+.
 
 ### Sandbox Helpers For Source Builds
 
@@ -242,3 +297,23 @@ zero upgrade
 ```
 
 See the [update guide](UPDATE.md) for update modes, flags, and platform details.
+
+`zero upgrade` behaves differently depending on how Zero was installed, because
+overwriting a binary a package manager owns leaves that manager describing a
+version that is no longer there:
+
+- **npm**: runs `npm install -g @gitlawb/zero@latest` for you.
+- **Homebrew**: refuses, and tells you to run `brew upgrade zero`. Replacing the
+  keg binary directly would be reverted by the next `brew upgrade` or
+  `brew reinstall`.
+- **everything else**: downloads the verified release archive and replaces the
+  binary in place.
+
+Homebrew is detected by the binary living inside a Cellar keg that carries
+Homebrew's own `INSTALL_RECEIPT.json`. The keg shape alone is not enough: a
+directory tree you built yourself can have exactly that shape, and refusing to
+update an install Homebrew never touched would be a real cost for a made-up
+reason. The receipt is the thing only Homebrew writes.
+
+An ordinary install under `/usr/local/bin` is left alone even on an Intel Mac
+where that is also the Homebrew prefix.

go.mod

@@ -1,10 +1,10 @@
 module github.com/Gitlawb/zero
 
-go 1.26.5
+go 1.26.6
 
 require (
 	charm.land/bubbles/v2 v2.1.1
-	charm.land/bubbletea/v2 v2.0.8
+	charm.land/bubbletea/v2 v2.0.9
 	charm.land/lipgloss/v2 v2.0.5
 	github.com/Microsoft/go-winio v0.6.2
 	github.com/alecthomas/chroma/v2 v2.27.0
@@ -16,7 +16,7 @@ require (
 	github.com/charmbracelet/x/term v0.2.2
 	github.com/coder/websocket v1.8.15
 	github.com/ledongthuc/pdf v0.0.0-20250511090121-5959a4027728
-	golang.org/x/image v0.44.0
+	golang.org/x/image v0.45.0
 	golang.org/x/sys v0.47.0
 	mvdan.cc/sh/v3 v3.13.1
 )

go.sum

@@ -1,7 +1,7 @@
 charm.land/bubbles/v2 v2.1.1 h1:7r55WzBxpo/R3z98hGmY7KKPd3ET6vsf0Fb9sDHOV60=
 charm.land/bubbles/v2 v2.1.1/go.mod h1:GE6M31gaWZVXzGw73OeuTTgy4lX+OtkH0E5ymnNsHxo=
-charm.land/bubbletea/v2 v2.0.8 h1:SxTJMhCAI3lbPmy4SgX5LWZ24AdINr4I6UEqzZvYJuY=
-charm.land/bubbletea/v2 v2.0.8/go.mod h1:2SkdgoTXluXJHOUwAoRlRXF/28vklb1rFl6GcgV1/ss=
+charm.land/bubbletea/v2 v2.0.9 h1:DpJCMWKgzQK8SJv4zbKKFHAI10ymWy/evClPFk0k0f8=
+charm.land/bubbletea/v2 v2.0.9/go.mod h1:2SkdgoTXluXJHOUwAoRlRXF/28vklb1rFl6GcgV1/ss=
 charm.land/lipgloss/v2 v2.0.5 h1:kbNxgeeUOYv5J0YdpxFjfvf3dFvqH8Aci4zB6xqFtrY=
 charm.land/lipgloss/v2 v2.0.5/go.mod h1:9oqhxt4yxIMe6q5A4kHr44DremZk7J9UNh74GlWa5nc=
 github.com/Microsoft/go-winio v0.6.2 h1:F2VQgta7ecxGYO8k3ZZz3RS8fVIXVxONVUPlNERoyfY=
@@ -64,8 +64,8 @@ github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e h1:JVG44RsyaB9T2KIHavM
 github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e/go.mod h1:RbqR21r5mrJuqunuUZ/Dhy/avygyECGrLceyNeo4LiM=
 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/image v0.44.0 h1:+tDekMZED9+LrtB3G5xzRggpVh9CARjZqROla3R3R+I=
-golang.org/x/image v0.44.0/go.mod h1:V8K3KE9KKKE+pLpQDOeN18w9oacNSvy1tDOirTu4xtY=
+golang.org/x/image v0.45.0 h1:FMb1nTbH5H9vF55SriQHgFw5GnNL9Jg6L25BwXKzhB0=
+golang.org/x/image v0.45.0/go.mod h1:n62x/7RqlwXDvGsSU4u6IUTUf6KghUZ9Bt7cG/T9Fx4=
 golang.org/x/sync v0.22.0 h1:SZjpbeLmrCk4xhRSZFNZW5gFUeCeFgjekvI/+gfScek=
 golang.org/x/sync v0.22.0/go.mod h1:9xrNwdLfx4jkKbNva9FpL6vEN7evnE43NNNJQ2LF3+0=
 golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=

internal/acp/agent.go

@@ -296,6 +296,16 @@ func stopReasonFor(result agent.Result, err error) (string, error) {
 		if errors.Is(err, context.Canceled) {
 			return StopCancelled, nil
 		}
+		// A CLIENT THAT CANCELLED A PERMISSION PROMPT DID NOT FAIL. Only
+		// context.Canceled was matched here, so dismissing a permission dialog —
+		// a deliberate action, and for apply_patch the only refusal a client is
+		// offered — came back as JSON-RPC -32603 carrying the internal sentinel
+		// text. Editors and the desktop app both render that as a crashed turn,
+		// so declining a tool looked like ZERO falling over. It is a
+		// cancellation, and StopCancelled is what ACP has for saying so.
+		if errors.Is(err, agent.ErrPermissionApprovalCanceled) {
+			return StopCancelled, nil
+		}
 		return "", err
 	}
 	if result.FinishReason == "length" {
@@ -311,10 +321,14 @@ func stopReasonFor(result agent.Result, err error) (string, error) {
 // session/request_permission request and maps the outcome back. Failure to reach
 // the client fails closed to deny.
 func (a *Agent) requestPermission(ctx context.Context, sessionID string, req agent.PermissionRequest) (agent.PermissionDecision, error) {
+	// Built ONCE and used for both halves. Sending one list and validating the
+	// reply against another is the defect this whole path had; see
+	// decisionFromOutcome.
+	options := buildPermissionOptions(req)
 	params := RequestPermissionParams{
 		SessionID: sessionID,
 		ToolCall:  permissionToolCall(req),
-		Options:   buildPermissionOptions(req),
+		Options:   options,
 	}
 	var result RequestPermissionResult
 	if err := a.conn.Call(ctx, MethodSessionRequestPerm, params, &result); err != nil {
@@ -323,7 +337,7 @@ func (a *Agent) requestPermission(ctx context.Context, sessionID string, req age
 		}
 		return agent.PermissionDecision{Action: agent.PermissionDecisionDeny, Reason: "permission request failed: " + err.Error()}, nil
 	}
-	return decisionFromOutcome(result.Outcome, req.AvailableDecisions), nil
+	return decisionFromOutcome(result.Outcome, options), nil
 }
 
 func (a *Agent) emitPlan(registry *tools.Registry, note *notifier) {

internal/acp/desktopinterop_test.go

@@ -0,0 +1,217 @@
+package acp
+
+// desktopinterop_test.go covers three defects found by driving the real `zero
+// acp` binary from a desktop ACP client. Each is a case where ZERO and a
+// conforming client disagreed about the wire, and none of them failed loudly —
+// they produced a silent denial, a spurious crash, or two buttons the user
+// could not tell apart.
+//
+// A fourth, session/load restoring history without replaying it, is fixed by
+// #914 rather than here: that one also gives the replayed messages stable ids
+// and keeps session/resume replay-free, which this did not.
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+
+	"github.com/Gitlawb/zero/internal/agent"
+)
+
+// ---- an offered option is an acceptable answer ----
+
+// The list the options were BUILT from and the list the answer was CHECKED
+// against were different whenever ZERO did not enumerate: the client was sent
+// Allow and Reject, and its reply was validated against an empty slice, so
+// every button it could possibly show failed closed to deny. The user clicked
+// Allow and ZERO recorded a denial, with nothing on screen to say so.
+func TestAnOfferedOptionIsAccepted(t *testing.T) {
+	// No AvailableDecisions: the fallback path, which is every permission event
+	// that is not a prompt.
+	req := agent.PermissionRequest{ToolName: "bash"}
+
+	options := buildPermissionOptions(req)
+	if len(options) == 0 {
+		t.Fatal("no options were offered")
+	}
+
+	for _, option := range options {
+		decision := decisionFromOutcome(
+			RequestPermissionOutcome{Outcome: OutcomeSelected, OptionID: option.OptionID},
+			buildPermissionOptions(req),
+		)
+		if string(decision.Action) != option.OptionID {
+			t.Fatalf("option %q was answered with %q (%s) — an offered option must be accepted",
+				option.OptionID, decision.Action, decision.Reason)
+		}
+	}
+}
+
+// The narrowing this validation exists for still holds: a client must not be
+// able to return a broader grant than it was shown.
+func TestAnOptionThatWasNotOfferedIsStillRefused(t *testing.T) {
+	req := agent.PermissionRequest{ToolName: "bash"}
+
+	decision := decisionFromOutcome(
+		RequestPermissionOutcome{Outcome: OutcomeSelected, OptionID: string(agent.PermissionDecisionAlwaysAllow)},
+		buildPermissionOptions(req),
+	)
+	if decision.Action != agent.PermissionDecisionDeny {
+		t.Fatalf("an unoffered broader grant was accepted as %q", decision.Action)
+	}
+}
+
+// The resolver is the single source of truth for both sides, which is what
+// makes the two agree by construction rather than by being kept in step.
+func TestOfferedDecisionsMatchWhatWasSent(t *testing.T) {
+	for _, req := range []agent.PermissionRequest{
+		{ToolName: "bash"},
+		{ToolName: "bash", AvailableDecisions: []agent.PermissionDecisionAction{
+			agent.PermissionDecisionAllow,
+			agent.PermissionDecisionAllowForSession,
+			agent.PermissionDecisionDeny,
+		}},
+	} {
+		offered := buildPermissionOptions(req)
+		for _, option := range buildPermissionOptions(req) {
+			if !actionOffered(option.OptionID, offered) {
+				t.Fatalf("option %q was sent but is not in the offered set %v", option.OptionID, offered)
+			}
+		}
+	}
+}
+
+// ---- two options the user can tell apart ----
+
+// request_permissions offers plain allow and strict-review allow together, and
+// both were labelled "Allow". The label is the only thing an ACP client shows,
+// so the panel presented two identical buttons where one silently enabled
+// strict auto-review of what was granted.
+func TestEveryOfferedOptionHasADistinctLabel(t *testing.T) {
+	req := agent.PermissionRequest{
+		ToolName: "request_permissions",
+		AvailableDecisions: []agent.PermissionDecisionAction{
+			agent.PermissionDecisionAllow,
+			agent.PermissionDecisionAllowStrict,
+			agent.PermissionDecisionAllowForSession,
+			agent.PermissionDecisionDeny,
+		},
+	}
+
+	seen := map[string]string{}
+	for _, option := range buildPermissionOptions(req) {
+		if previous, clash := seen[option.Name]; clash {
+			t.Fatalf("options %q and %q share the label %q — a user cannot tell them apart",
+				previous, option.OptionID, option.Name)
+		}
+		seen[option.Name] = option.OptionID
+	}
+}
+
+// The two remain distinct decisions: the label changed, the round trip did not.
+func TestStrictAllowStillRoundTrips(t *testing.T) {
+	req := agent.PermissionRequest{
+		ToolName: "request_permissions",
+		AvailableDecisions: []agent.PermissionDecisionAction{
+			agent.PermissionDecisionAllow,
+			agent.PermissionDecisionAllowStrict,
+		},
+	}
+	decision := decisionFromOutcome(
+		RequestPermissionOutcome{Outcome: OutcomeSelected, OptionID: string(agent.PermissionDecisionAllowStrict)},
+		buildPermissionOptions(req),
+	)
+	if decision.Action != agent.PermissionDecisionAllowStrict {
+		t.Fatalf("strict allow round-tripped as %q", decision.Action)
+	}
+}
+
+// ---- cancelling a permission is a cancellation, not a crash ----
+
+// Only context.Canceled was recognised, so dismissing a permission dialog came
+// back as JSON-RPC -32603 carrying the internal sentinel text. Clients render
+// that as a failed turn, so declining a tool looked like ZERO falling over —
+// and for apply_patch, dismissing is the ONLY refusal a client is offered.
+func TestCancellingAPermissionEndsTheTurnAsCancelled(t *testing.T) {
+	canceled := fmt.Errorf("%w for apply_patch", agent.ErrPermissionApprovalCanceled)
+
+	reason, err := stopReasonFor(agent.Result{}, canceled)
+	if err != nil {
+		t.Fatalf("stopReasonFor returned an error for a cancellation: %v", err)
+	}
+	if reason != StopCancelled {
+		t.Fatalf("stop reason = %q, want %q", reason, StopCancelled)
+	}
+}
+
+// A genuine failure must still be an error. Mapping too much to cancelled would
+// hide real faults behind a clean ending, which is the opposite mistake.
+func TestARealFailureIsStillAnError(t *testing.T) {
+	failure := errors.New("provider exploded")
+
+	if _, err := stopReasonFor(agent.Result{}, failure); !errors.Is(err, failure) {
+		t.Fatalf("stopReasonFor(%v) = %v, want the failure preserved", failure, err)
+	}
+}
+
+// The sentinel is matched through errors.Is, so it survives the wrapping every
+// return site applies — each one adds the tool name.
+func TestPermissionCancellationSurvivesWrapping(t *testing.T) {
+	if !errors.Is(fmt.Errorf("%w for bash", agent.ErrPermissionApprovalCanceled), agent.ErrPermissionApprovalCanceled) {
+		t.Fatal("a wrapped permission cancellation was not recognised")
+	}
+	if errors.Is(errors.New("something else"), agent.ErrPermissionApprovalCanceled) {
+		t.Fatal("an unrelated error was reported as a permission cancellation")
+	}
+}
+
+// A decision that never became an option cannot be selected.
+//
+// PermissionDecisionCancel is the case that exists today: optionKindFor drops
+// it because ACP expresses cancellation through the outcome, yet ZERO
+// enumerates it in AvailableDecisions for shell commands and apply_patch. While
+// the reply was validated against the DECISIONS rather than the sent options, a
+// client could return {"outcome":"selected","optionId":"cancel"} — an id it was
+// never shown — and abort the whole turn.
+//
+// Written over every option-less decision rather than over "cancel", so a
+// future action that optionKindFor declines to render is covered the day it is
+// added rather than the day someone remembers this test.
+func TestADecisionThatIsNotAnOptionCannotBeSelected(t *testing.T) {
+	for _, toolName := range []string{"bash", "apply_patch"} {
+		req := agent.PermissionRequest{
+			ToolName: toolName,
+			AvailableDecisions: []agent.PermissionDecisionAction{
+				agent.PermissionDecisionAllow,
+				agent.PermissionDecisionDeny,
+				agent.PermissionDecisionCancel,
+			},
+		}
+		options := buildPermissionOptions(req)
+
+		for _, action := range req.AvailableDecisions {
+			if actionOffered(string(action), options) {
+				continue // it was sent; selecting it is legitimate
+			}
+			decision := decisionFromOutcome(
+				RequestPermissionOutcome{Outcome: OutcomeSelected, OptionID: string(action)},
+				options,
+			)
+			if decision.Action != agent.PermissionDecisionDeny {
+				t.Fatalf("%s: %q was never sent as an option but was accepted as %q",
+					toolName, action, decision.Action)
+			}
+		}
+	}
+}
+
+// Cancelling is still reachable — through the outcome, which is where ACP puts
+// it. Closing the selected-id route must not close the real one.
+func TestCancellingThroughTheOutcomeStillWorks(t *testing.T) {
+	options := buildPermissionOptions(agent.PermissionRequest{ToolName: "apply_patch"})
+
+	decision := decisionFromOutcome(RequestPermissionOutcome{Outcome: OutcomeCancelled}, options)
+	if decision.Action != agent.PermissionDecisionCancel {
+		t.Fatalf("outcome=cancelled gave %q, want cancel", decision.Action)
+	}
+}

internal/acp/permission.go

@@ -15,14 +15,7 @@ import (
 // PermissionOptions. Only the actions ZERO actually presented (AvailableDecisions)
 // are surfaced; the optionId is the ZERO action string for a clean round-trip.
 func buildPermissionOptions(req agent.PermissionRequest) []PermissionOption {
-	actions := req.AvailableDecisions
-	if len(actions) == 0 {
-		// Sensible default if ZERO didn't enumerate: allow once / reject.
-		actions = []agent.PermissionDecisionAction{
-			agent.PermissionDecisionAllow,
-			agent.PermissionDecisionDeny,
-		}
-	}
+	actions := offeredDecisions(req)
 	options := make([]PermissionOption, 0, len(actions))
 	for _, action := range actions {
 		kind, name := optionKindFor(action, req.PrefixApprovalEscalates)
@@ -38,6 +31,32 @@ func buildPermissionOptions(req agent.PermissionRequest) []PermissionOption {
 	return options
 }
 
+// offeredDecisions resolves what this request actually offers the client.
+//
+// ONE RESOLVER, USED BY BOTH SIDES, and that is the entire point of it existing.
+// The fallback below used to live inside buildPermissionOptions while
+// requestPermission validated the client's answer against the raw
+// req.AvailableDecisions. When ZERO did not enumerate — which is every
+// permission event that is not a prompt, and includes a shell call whose sandbox
+// decision came back deny — the two disagreed completely: the client was sent
+// "Allow" and "Reject", and validation was performed against an EMPTY list, so
+// every option the client could possibly click failed closed to deny with
+// "permission option was not offered".
+//
+// The user clicked Allow and ZERO recorded a denial. Nothing surfaced it,
+// because a denial is a legitimate answer — the tool was simply refused and the
+// turn carried on as though the user had rejected it.
+func offeredDecisions(req agent.PermissionRequest) []agent.PermissionDecisionAction {
+	if len(req.AvailableDecisions) > 0 {
+		return req.AvailableDecisions
+	}
+	// Sensible default if ZERO didn't enumerate: allow once / reject.
+	return []agent.PermissionDecisionAction{
+		agent.PermissionDecisionAllow,
+		agent.PermissionDecisionDeny,
+	}
+}
+
 // optionKindFor maps a ZERO decision action to an ACP PermissionOptionKind and a
 // human label. Returns an empty kind for actions that ACP expresses through the
 // outcome rather than an option (cancel).
@@ -49,8 +68,16 @@ func buildPermissionOptions(req agent.PermissionRequest) []PermissionOption {
 // disclosure cannot be TUI-only.
 func optionKindFor(action agent.PermissionDecisionAction, escalates bool) (kind, name string) {
 	switch action {
-	case agent.PermissionDecisionAllow, agent.PermissionDecisionAllowStrict:
+	case agent.PermissionDecisionAllow:
 		return PermAllowOnce, "Allow"
+	case agent.PermissionDecisionAllowStrict:
+		// SPLIT FROM PLAIN ALLOW because the label is the only thing an ACP
+		// client shows. Both were labelled "Allow", and request_permissions
+		// offers them together — so the panel presented two identical buttons,
+		// and whichever the user picked looked the same while one of them
+		// silently turned on strict auto-review of what was granted. The option
+		// id carries no room for the distinction, so it has to be in the name.
+		return PermAllowOnce, "Allow with strict review"
 	case agent.PermissionDecisionAllowForSession:
 		return PermAllowAlways, "Allow for this session"
 	case agent.PermissionDecisionAllowPrefix:
@@ -70,19 +97,31 @@ func optionKindFor(action agent.PermissionDecisionAction, escalates bool) (kind,
 
 // decisionFromOutcome maps the client's permission outcome back to a ZERO
 // decision. A cancelled outcome cancels the run; a selected option id is the ZERO
-// action verbatim (validated against what was offered); anything unrecognized
-// fails closed to deny.
-func decisionFromOutcome(outcome RequestPermissionOutcome, offered []agent.PermissionDecisionAction) agent.PermissionDecision {
+// action verbatim (validated against what was actually sent); anything
+// unrecognized fails closed to deny.
+//
+// IT TAKES THE OPTIONS THAT WERE SENT, not the decisions the request offered,
+// and the two are not the same list. Some actions never become options —
+// PermissionDecisionCancel is dropped by optionKindFor because ACP expresses
+// cancellation through the outcome instead — yet it IS enumerated in
+// AvailableDecisions for shell commands and apply_patch, the two commonest
+// prompts. Validating against the decisions therefore accepted
+// {"outcome":"selected","optionId":"cancel"}: an identifier no client was ever
+// shown, aborting the whole turn.
+//
+// Passing the sent options makes "what we offered" and "what we accept" the
+// same slice rather than two things kept in step, so anything optionKindFor
+// declines to render is excluded structurally instead of by name.
+func decisionFromOutcome(outcome RequestPermissionOutcome, offered []PermissionOption) agent.PermissionDecision {
 	switch outcome.Outcome {
 	case OutcomeCancelled:
 		return agent.PermissionDecision{Action: agent.PermissionDecisionCancel, Reason: "client cancelled"}
 	case OutcomeSelected:
-		action := agent.PermissionDecisionAction(outcome.OptionID)
 		// Bind to what was actually offered for THIS call: a client must not be able
 		// to return a broader grant (always_allow / allow_for_session) that wasn't
 		// presented. Anything not offered fails closed to deny.
-		if actionOffered(action, offered) {
-			return agent.PermissionDecision{Action: action}
+		if actionOffered(outcome.OptionID, offered) {
+			return agent.PermissionDecision{Action: agent.PermissionDecisionAction(outcome.OptionID)}
 		}
 		return agent.PermissionDecision{Action: agent.PermissionDecisionDeny, Reason: "permission option was not offered"}
 	default:
@@ -90,9 +129,9 @@ func decisionFromOutcome(outcome RequestPermissionOutcome, offered []agent.Permi
 	}
 }
 
-func actionOffered(action agent.PermissionDecisionAction, offered []agent.PermissionDecisionAction) bool {
-	for _, a := range offered {
-		if a == action {
+func actionOffered(optionID string, offered []PermissionOption) bool {
+	for _, option := range offered {
+		if option.OptionID == optionID {
 			return true
 		}
 	}

internal/acp/permission_escalation_test.go

@@ -56,10 +56,11 @@ func TestACPPrefixOptionsStaySilentWithoutEscalation(t *testing.T) {
 // what was offered, so decorating it would fail every prefix approval closed.
 func TestACPDisclosureDoesNotDisturbTheOptionIDRoundTrip(t *testing.T) {
 	request := escalationRequest(true)
-	for _, option := range buildPermissionOptions(request) {
+	options := buildPermissionOptions(request)
+	for _, option := range options {
 		decision := decisionFromOutcome(
 			RequestPermissionOutcome{Outcome: OutcomeSelected, OptionID: option.OptionID},
-			request.AvailableDecisions,
+			options,
 		)
 		if string(decision.Action) != option.OptionID {
 			t.Errorf("option id %q round-tripped to %q (%s)", option.OptionID, decision.Action, decision.Reason)

internal/acp/permission_test.go

@@ -39,11 +39,14 @@ func TestBuildPermissionOptionsDefault(t *testing.T) {
 }
 
 func TestDecisionFromOutcome(t *testing.T) {
-	offered := []agent.PermissionDecisionAction{
-		agent.PermissionDecisionAllow,
-		agent.PermissionDecisionAlwaysAllow,
-		agent.PermissionDecisionDeny,
-	}
+	offered := buildPermissionOptions(agent.PermissionRequest{
+		ToolName: "bash",
+		AvailableDecisions: []agent.PermissionDecisionAction{
+			agent.PermissionDecisionAllow,
+			agent.PermissionDecisionAlwaysAllow,
+			agent.PermissionDecisionDeny,
+		},
+	})
 	if d := decisionFromOutcome(RequestPermissionOutcome{Outcome: OutcomeCancelled}, offered); d.Action != agent.PermissionDecisionCancel {
 		t.Errorf("cancelled -> %q, want cancel", d.Action)
 	}

internal/agent/command_prefix_test.go

@@ -99,6 +99,43 @@ func TestProposedCommandPrefixRejectsUnsafeRequestedPrefix(t *testing.T) {
 	}
 }
 
+// The launcher denylist is only worth anything if it holds on the path a user
+// actually sees. A model naming its own prefix_rule is that path: before
+// launcher names were normalized, "python3.11" was offered as a one-token
+// grant, and hasStringPrefix then matched every later python3.11 invocation.
+func TestProposedCommandPrefixRejectsLauncherSpellingsInRequestedPrefix(t *testing.T) {
+	for _, testCase := range []struct {
+		command string
+		rule    []any
+	}{
+		{"python3.11 script.py", []any{"python3.11"}},
+		{"python.exe script.py", []any{"python.exe"}},
+		{"node.exe app.js", []any{"node.exe"}},
+		{"cmd /c whoami", []any{"cmd"}},
+		{"busybox sh -c id", []any{"busybox"}},
+		{"uv run main.py", []any{"uv", "run"}},
+		{"python3.11 -c import_os", []any{"python3.11", "-c"}},
+	} {
+		got := proposedCommandPrefix("bash", map[string]any{
+			"command":     testCase.command,
+			"prefix_rule": testCase.rule,
+		})
+		if got != nil {
+			t.Errorf("prefix_rule %v for %q was offered as %#v, want rejected", testCase.rule, testCase.command, got)
+		}
+	}
+}
+
+func TestProposedCommandPrefixStillOffersOrdinaryCommands(t *testing.T) {
+	got := proposedCommandPrefix("bash", map[string]any{
+		"command":     "cargo build --release",
+		"prefix_rule": []any{"cargo", "build"},
+	})
+	if len(got) != 2 || got[0] != "cargo" || got[1] != "build" {
+		t.Fatalf("ordinary prefix rule = %#v, want [cargo build]", got)
+	}
+}
+
 func TestProposedCommandPrefixRejectsUnsafeShellForms(t *testing.T) {
 	cases := []string{
 		"cat < in > out",

internal/agent/compaction.go

@@ -144,11 +144,17 @@ func estimateToolDefTokens(tools []zeroruntime.ToolDefinition) int {
 	for _, tool := range tools {
 		total += ApproxTextTokens(tool.Name)
 		total += ApproxTextTokens(tool.Description)
+		total += ApproxTextTokens(string(tool.Type))
 		if len(tool.Parameters) > 0 {
 			if encoded, err := json.Marshal(tool.Parameters); err == nil {
 				total += ApproxTextTokens(string(encoded))
 			}
 		}
+		if tool.Format != nil {
+			total += ApproxTextTokens(tool.Format.Type)
+			total += ApproxTextTokens(tool.Format.Syntax)
+			total += ApproxTextTokens(tool.Format.Definition)
+		}
 		total += 4 // per-tool overhead
 	}
 	return total

internal/agent/compaction_projection.go

@@ -126,8 +126,11 @@ func capCompactionBrief(brief string) (string, bool) {
 
 func compactionToolCallLine(call zeroruntime.ToolCall) string {
 	detail := ""
+	if call.Freeform && call.Name == "apply_patch" {
+		detail = strings.Join(patchPaths(call.Arguments), ", ")
+	}
 	var arguments map[string]any
-	if json.Unmarshal([]byte(strings.TrimSpace(call.Arguments)), &arguments) == nil {
+	if detail == "" && json.Unmarshal([]byte(strings.TrimSpace(call.Arguments)), &arguments) == nil {
 		for _, key := range []string{"file_path", "path", "url", "query", "pattern", "prompt", "description", "question"} {
 			if value, ok := arguments[key].(string); ok && strings.TrimSpace(value) != "" {
 				detail = value

internal/agent/compaction_projection_test.go

@@ -73,6 +73,7 @@ func TestProjectCompactionInputRetainsAskUserExchangeAndSemanticArguments(t *tes
 		{Role: zeroruntime.MessageRoleTool, ToolCallID: "ask", Content: "Which database should remain?: Postgres only; do not touch MySQL."},
 		{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{
 			{ID: "patch", Name: "apply_patch", Arguments: `{"patch":"*** Begin Patch\n*** Update File: internal/db.go\n*** End Patch"}`},
+			{ID: "raw-patch", Name: "apply_patch", Freeform: true, Arguments: "*** Begin Patch\n*** Update File: internal/api.go\n*** Add File: internal/config.go\n*** End Patch\n"},
 			{ID: "fetch", Name: "web_fetch", Arguments: `{"url":"https://example.com/spec"}`},
 			{ID: "task", Name: "task", Arguments: `{"prompt":"Inspect the Windows implementation"}`},
 		}},
@@ -80,7 +81,7 @@ func TestProjectCompactionInputRetainsAskUserExchangeAndSemanticArguments(t *tes
 	}
 
 	content := projectCompactionInput(messages).messages[0].Content
-	for _, want := range []string{"Which database should remain?", "Postgres only; do not touch MySQL", "internal/db.go", "https://example.com/spec", "Inspect the Windows implementation"} {
+	for _, want := range []string{"Which database should remain?", "Postgres only; do not touch MySQL", "internal/db.go", "internal/api.go", "internal/config.go", "https://example.com/spec", "Inspect the Windows implementation"} {
 		if !strings.Contains(content, want) {
 			t.Fatalf("projection missing %q: %q", want, content)
 		}

internal/agent/compaction_test.go

@@ -275,6 +275,27 @@ func TestEstimateToolDefTokensCountsDefinitions(t *testing.T) {
 	if estimateToolDefTokens(one) <= 0 {
 		t.Fatal("a tool definition (name + description + schema) should estimate > 0 tokens")
 	}
+	typed := append([]zeroruntime.ToolDefinition(nil), one...)
+	typed[0].Type = zeroruntime.ToolDefinitionFreeform
+	if estimateToolDefTokens(typed) <= estimateToolDefTokens(one) {
+		t.Fatal("a non-empty tool type must increase the estimated request cost")
+	}
+	for _, test := range []struct {
+		name   string
+		format zeroruntime.ToolDefinitionFormat
+	}{
+		{name: "type", format: zeroruntime.ToolDefinitionFormat{Type: "grammar"}},
+		{name: "syntax", format: zeroruntime.ToolDefinitionFormat{Syntax: "lark"}},
+		{name: "definition", format: zeroruntime.ToolDefinitionFormat{Definition: "start: WORD"}},
+	} {
+		t.Run("format "+test.name, func(t *testing.T) {
+			formatted := append([]zeroruntime.ToolDefinition(nil), one...)
+			formatted[0].Format = &test.format
+			if estimateToolDefTokens(formatted) <= estimateToolDefTokens(one) {
+				t.Fatalf("a non-empty format %s must increase the estimated request cost", test.name)
+			}
+		})
+	}
 	two := append(append([]zeroruntime.ToolDefinition{}, one...), zeroruntime.ToolDefinition{
 		Name:        "write_file",
 		Description: "Write contents to a file in the workspace.",

internal/agent/context_planner.go

@@ -102,6 +102,10 @@ func copyToolDefinitions(toolDefs []zeroruntime.ToolDefinition) []zeroruntime.To
 	for index, definition := range toolDefs {
 		copied[index] = definition
 		copied[index].Parameters = copySchemaMap(definition.Parameters)
+		if definition.Format != nil {
+			format := *definition.Format
+			copied[index].Format = &format
+		}
 	}
 	return copied
 }

internal/agent/context_planner_test.go

@@ -15,6 +15,7 @@ func TestContextPlannerPreservesProviderRequest(t *testing.T) {
 	}
 	toolDefs := []zeroruntime.ToolDefinition{{
 		Name: "read_file", Description: "Read a file",
+		Format: &zeroruntime.ToolDefinitionFormat{Type: "grammar", Syntax: "lark", Definition: "start: PATH"},
 		Parameters: map[string]any{
 			"type":       "object",
 			"required":   []string{"path"},
@@ -53,10 +54,12 @@ func TestContextPlannerPreservesProviderRequest(t *testing.T) {
 	toolDefs[0].Parameters["required"].([]string)[0] = "other"
 	toolDefs[0].Parameters["properties"].(map[string]any)["path"].(map[string]any)["type"] = "integer"
 	toolDefs[0].Parameters["anyOf"].([]any)[0].(map[string]any)["type"] = "array"
+	toolDefs[0].Format.Definition = "changed"
 	if plan.Request.Messages[1].Content != "inspect this" || plan.Request.Messages[1].Images[0].Data[0] != 1 {
 		t.Fatalf("planned messages alias caller state: %#v", plan.Request.Messages[1])
 	}
 	if plan.Request.Tools[0].Name != "read_file" ||
+		plan.Request.Tools[0].Format == nil || plan.Request.Tools[0].Format.Definition != "start: PATH" ||
 		plan.Request.Tools[0].Parameters["required"].([]string)[0] != "path" ||
 		plan.Request.Tools[0].Parameters["properties"].(map[string]any)["path"].(map[string]any)["type"] != "string" ||
 		plan.Request.Tools[0].Parameters["anyOf"].([]any)[0].(map[string]any)["type"] != "object" {

internal/agent/freeform_tool_test.go

@@ -0,0 +1,378 @@
+package agent
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+
+	"github.com/Gitlawb/zero/internal/sandbox"
+	"github.com/Gitlawb/zero/internal/tools"
+	"github.com/Gitlawb/zero/internal/zeroruntime"
+)
+
+type customApplyPatchTool struct {
+	calls int
+}
+
+type fixedPathScope struct {
+	roots []string
+}
+
+func (scope fixedPathScope) Roots() []string {
+	return append([]string(nil), scope.roots...)
+}
+
+func newFixedPathScope(t *testing.T, roots ...string) fixedPathScope {
+	t.Helper()
+	resolved := make([]string, 0, len(roots))
+	for _, root := range roots {
+		absolute, err := filepath.Abs(root)
+		if err != nil {
+			t.Fatalf("Abs(%q): %v", root, err)
+		}
+		if physical, err := filepath.EvalSymlinks(absolute); err == nil {
+			absolute = physical
+		}
+		resolved = append(resolved, absolute)
+	}
+	return fixedPathScope{roots: resolved}
+}
+
+func (*customApplyPatchTool) Name() string        { return "apply_patch" }
+func (*customApplyPatchTool) Description() string { return "custom JSON tool" }
+func (*customApplyPatchTool) Parameters() tools.Schema {
+	return tools.Schema{Type: "object", Properties: map[string]tools.PropertySchema{"value": {Type: "string"}}}
+}
+func (*customApplyPatchTool) Safety() tools.Safety {
+	return tools.Safety{Permission: tools.PermissionAllow, SideEffect: tools.SideEffectRead}
+}
+func (tool *customApplyPatchTool) Run(context.Context, map[string]any) tools.Result {
+	tool.calls++
+	return tools.Result{Status: tools.StatusOK}
+}
+
+func TestFreeformApplyPatchUsesExistingToolExecutionPath(t *testing.T) {
+	root := t.TempDir()
+	registry := tools.NewRegistry()
+	registry.Register(tools.NewScopedApplyPatchTool(root, nil))
+	patch := "*** Begin Patch\n*** Add File: hello.txt\n+hello\n*** End Patch\n"
+
+	result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
+		ID:        "call-1",
+		Name:      "apply_patch",
+		Arguments: patch,
+		Freeform:  true,
+	}, PermissionModeUnsafe, Options{Cwd: root, FileTracker: tools.NewFileTracker()})
+	if err != nil {
+		t.Fatalf("executeToolCall: %v", err)
+	}
+	if result.Status != tools.StatusOK {
+		t.Fatalf("freeform apply_patch status = %s: %s", result.Status, result.Output)
+	}
+	content, err := os.ReadFile(filepath.Join(root, "hello.txt"))
+	if err != nil {
+		t.Fatalf("read patched file: %v", err)
+	}
+	if string(content) != "hello\n" {
+		t.Fatalf("patched content = %q, want hello newline", content)
+	}
+}
+
+func TestFreeformApplyPatchSupportsGrantedExtraRoot(t *testing.T) {
+	root := t.TempDir()
+	extra := t.TempDir()
+	scope, err := sandbox.NewScope(root, []string{extra})
+	if err != nil {
+		t.Fatalf("NewScope: %v", err)
+	}
+	registry := tools.NewRegistry()
+	registry.Register(tools.NewScopedApplyPatchTool(root, scope))
+	target := filepath.Join(extra, "hello.txt")
+	patch := "*** Begin Patch\n*** Add File: " + target + "\n+hello\n*** End Patch\n"
+
+	result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
+		ID: "call-1", Name: "apply_patch", Arguments: patch, Freeform: true,
+	}, PermissionModeUnsafe, Options{Cwd: root, FileTracker: tools.NewFileTracker()})
+	if err != nil {
+		t.Fatalf("executeToolCall: %v", err)
+	}
+	if result.Status != tools.StatusOK {
+		t.Fatalf("freeform extra-root apply_patch status = %s: %s", result.Status, result.Output)
+	}
+	content, err := os.ReadFile(target)
+	if err != nil {
+		t.Fatalf("read extra-root patched file: %v", err)
+	}
+	if string(content) != "hello\n" {
+		t.Fatalf("patched content = %q, want hello newline", content)
+	}
+}
+
+func TestFreeformApplyPatchRejectsMixedWorkspaceAndExtraRoots(t *testing.T) {
+	for _, extraHasMatchingPath := range []bool{false, true} {
+		name := "extra target missing"
+		if extraHasMatchingPath {
+			name = "extra target exists"
+		}
+		t.Run(name, func(t *testing.T) {
+			workspace := t.TempDir()
+			extra := t.TempDir()
+			if err := os.MkdirAll(filepath.Join(workspace, "src"), 0o755); err != nil {
+				t.Fatal(err)
+			}
+			workspaceTarget := filepath.Join(workspace, "src", "a.go")
+			if err := os.WriteFile(workspaceTarget, []byte("old\n"), 0o644); err != nil {
+				t.Fatal(err)
+			}
+			extraTarget := filepath.Join(extra, "src", "a.go")
+			if extraHasMatchingPath {
+				if err := os.MkdirAll(filepath.Dir(extraTarget), 0o755); err != nil {
+					t.Fatal(err)
+				}
+				if err := os.WriteFile(extraTarget, []byte("old\n"), 0o644); err != nil {
+					t.Fatal(err)
+				}
+			}
+			scope, err := sandbox.NewScope(workspace, []string{extra})
+			if err != nil {
+				t.Fatal(err)
+			}
+			registry := tools.NewRegistry()
+			registry.Register(tools.NewScopedApplyPatchTool(workspace, scope))
+			extraCreated := filepath.Join(extra, "b.go")
+			patch := strings.Join([]string{
+				"*** Begin Patch",
+				"*** Update File: src/a.go",
+				"@@",
+				"-old",
+				"+new",
+				"*** Add File: " + extraCreated,
+				"+extra",
+				"*** End Patch",
+			}, "\n")
+
+			result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
+				ID: "call-1", Name: "apply_patch", Arguments: patch, Freeform: true,
+			}, PermissionModeUnsafe, Options{Cwd: workspace, FileTracker: tools.NewFileTracker()})
+			if err != nil {
+				t.Fatalf("executeToolCall: %v", err)
+			}
+			if result.Status != tools.StatusError || !strings.Contains(result.Output, "mixes workspace-relative paths with an extra write root") {
+				t.Fatalf("mixed-root patch result = %s: %s", result.Status, result.Output)
+			}
+			if content, err := os.ReadFile(workspaceTarget); err != nil || string(content) != "old\n" {
+				t.Fatalf("workspace target changed: content=%q err=%v", content, err)
+			}
+			if extraHasMatchingPath {
+				if content, err := os.ReadFile(extraTarget); err != nil || string(content) != "old\n" {
+					t.Fatalf("extra-root target changed: content=%q err=%v", content, err)
+				}
+			}
+			if _, err := os.Stat(extraCreated); !os.IsNotExist(err) {
+				t.Fatalf("mixed-root patch created extra file: %v", err)
+			}
+		})
+	}
+}
+
+func TestFreeformApplyPatchAcceptsOneSemanticRoot(t *testing.T) {
+	for _, test := range []struct {
+		name         string
+		useExtraRoot bool
+	}{
+		{name: "workspace"},
+		{name: "extra root", useExtraRoot: true},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			workspace := t.TempDir()
+			extra := t.TempDir()
+			scope, err := sandbox.NewScope(workspace, []string{extra})
+			if err != nil {
+				t.Fatal(err)
+			}
+			root := workspace
+			if test.useExtraRoot {
+				root = extra
+			}
+			if err := os.MkdirAll(filepath.Join(root, "src"), 0o755); err != nil {
+				t.Fatal(err)
+			}
+			target := filepath.Join(root, "src", "a.go")
+			if err := os.WriteFile(target, []byte("old\n"), 0o644); err != nil {
+				t.Fatal(err)
+			}
+			updatePath := target
+			if !test.useExtraRoot {
+				updatePath = filepath.Join("src", "a.go")
+			}
+			created := filepath.Join(root, "b.go")
+			patch := strings.Join([]string{
+				"*** Begin Patch",
+				"*** Update File: " + updatePath,
+				"@@",
+				"-old",
+				"+new",
+				"*** Add File: " + created,
+				"+created",
+				"*** End Patch",
+			}, "\n")
+			registry := tools.NewRegistry()
+			registry.Register(tools.NewScopedApplyPatchTool(workspace, scope))
+			result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
+				ID: "call-1", Name: "apply_patch", Arguments: patch, Freeform: true,
+			}, PermissionModeUnsafe, Options{Cwd: workspace, FileTracker: tools.NewFileTracker()})
+			if err != nil {
+				t.Fatalf("executeToolCall: %v", err)
+			}
+			if result.Status != tools.StatusOK {
+				t.Fatalf("single-root patch status = %s: %s", result.Status, result.Output)
+			}
+			if content, err := os.ReadFile(target); err != nil || string(content) != "new\n" {
+				t.Fatalf("updated content=%q err=%v", content, err)
+			}
+			if content, err := os.ReadFile(created); err != nil || string(content) != "created\n" {
+				t.Fatalf("created content=%q err=%v", content, err)
+			}
+		})
+	}
+}
+
+func TestFreeformApplyPatchRejectsAbsolutePathOutsideGrantedRoots(t *testing.T) {
+	root := t.TempDir()
+	granted := t.TempDir()
+	outside := t.TempDir()
+	scope := newFixedPathScope(t, root, granted)
+	registry := tools.NewRegistry()
+	registry.Register(tools.NewScopedApplyPatchTool(root, scope))
+	target := filepath.Join(outside, "blocked.txt")
+	patch := "*** Begin Patch\n*** Add File: " + target + "\n+blocked\n*** End Patch\n"
+
+	result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
+		ID: "call-1", Name: "apply_patch", Arguments: patch, Freeform: true,
+	}, PermissionModeUnsafe, Options{Cwd: root})
+	if err != nil {
+		t.Fatalf("executeToolCall: %v", err)
+	}
+	if result.Status != tools.StatusError {
+		t.Fatalf("ungranted absolute patch status = %s, want error: %s", result.Status, result.Output)
+	}
+	if _, err := os.Stat(target); !os.IsNotExist(err) {
+		t.Fatalf("ungranted absolute patch created target: %v", err)
+	}
+}
+
+func TestPreparedFreeformPatchRejectsIntermediateSymlinkSwap(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("creating directory symlinks requires privileges on Windows")
+	}
+	root := t.TempDir()
+	extra := t.TempDir()
+	outside := t.TempDir()
+	intermediate := filepath.Join(extra, "nested")
+	if err := os.Mkdir(intermediate, 0o755); err != nil {
+		t.Fatalf("Mkdir: %v", err)
+	}
+	scope := newFixedPathScope(t, root, extra)
+	tool := tools.NewScopedApplyPatchTool(root, scope)
+	target := filepath.Join(intermediate, "blocked.txt")
+	patch := "*** Begin Patch\n*** Add File: " + target + "\n+blocked\n*** End Patch\n"
+	args, err := tools.PrepareFreeformApplyPatchArguments(tool, patch)
+	if err != nil {
+		t.Fatalf("PrepareFreeformApplyPatchArguments: %v", err)
+	}
+
+	if err := os.Remove(intermediate); err != nil {
+		t.Fatalf("Remove intermediate: %v", err)
+	}
+	if err := os.Symlink(outside, intermediate); err != nil {
+		t.Fatalf("Symlink: %v", err)
+	}
+	result := tool.Run(context.Background(), args)
+	if result.Status != tools.StatusError {
+		t.Fatalf("symlink-swapped patch status = %s, want error: %s", result.Status, result.Output)
+	}
+	if _, err := os.Stat(filepath.Join(outside, "blocked.txt")); !os.IsNotExist(err) {
+		t.Fatalf("symlink-swapped patch wrote outside root: %v", err)
+	}
+}
+
+func TestUnknownFreeformToolFailsClosed(t *testing.T) {
+	result, err := executeToolCall(context.Background(), tools.NewRegistry(), zeroruntime.ToolCall{
+		ID: "call-1", Name: "unknown", Arguments: "raw", Freeform: true,
+	}, PermissionModeUnsafe, Options{})
+	if err != nil {
+		t.Fatalf("executeToolCall: %v", err)
+	}
+	if result.Status != tools.StatusError {
+		t.Fatalf("unknown freeform status = %s, want error", result.Status)
+	}
+}
+
+func TestCustomApplyPatchCannotUseFreeformContract(t *testing.T) {
+	custom := &customApplyPatchTool{}
+	registry := tools.NewRegistry()
+	registry.Register(custom)
+
+	result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
+		ID: "call-1", Name: "apply_patch", Arguments: "raw patch", Freeform: true,
+	}, PermissionModeUnsafe, Options{})
+	if err != nil {
+		t.Fatalf("executeToolCall: %v", err)
+	}
+	if result.Status != tools.StatusError || !strings.Contains(result.Output, "Unsupported freeform tool call") {
+		t.Fatalf("custom freeform apply_patch result = %#v, want unsupported error", result)
+	}
+	if custom.calls != 0 {
+		t.Fatalf("custom apply_patch executed %d times", custom.calls)
+	}
+}
+
+func TestDeniedFreeformApplyPatchDoesNotWrite(t *testing.T) {
+	root := t.TempDir()
+	registry := tools.NewRegistry()
+	registry.Register(tools.NewScopedApplyPatchTool(root, nil))
+	patch := "*** Begin Patch\n*** Add File: denied.txt\n+must not exist\n*** End Patch\n"
+
+	result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
+		ID:        "call-1",
+		Name:      "apply_patch",
+		Arguments: patch,
+		Freeform:  true,
+	}, PermissionModeAsk, Options{
+		Cwd: root,
+		OnPermissionRequest: func(context.Context, PermissionRequest) (PermissionDecision, error) {
+			return PermissionDecision{Action: PermissionDecisionDeny, Reason: "test denial"}, nil
+		},
+	})
+	if err != nil {
+		t.Fatalf("executeToolCall: %v", err)
+	}
+	if result.Status != tools.StatusError {
+		t.Fatalf("denied freeform status = %s, want error", result.Status)
+	}
+	if _, err := os.Stat(filepath.Join(root, "denied.txt")); !os.IsNotExist(err) {
+		t.Fatalf("denied freeform patch changed the workspace: %v", err)
+	}
+}
+
+func TestHistorySafeToolCallsPreservesRawFreeformArguments(t *testing.T) {
+	raw := "*** Begin Patch\n*** Update File: internal/main.go\n@@\n-old\n+new\n*** End Patch\n"
+	safe := historySafeToolCalls([]ToolCall{{
+		ID: "call-1", ProviderCallID: "provider-1", Name: "apply_patch", Arguments: raw, Freeform: true,
+	}})
+	if len(safe) != 1 || safe[0].Arguments != raw || safe[0].ProviderCallID != "provider-1" || !safe[0].Freeform {
+		t.Fatalf("freeform history changed raw call: %#v", safe)
+	}
+}
+
+func TestAbortedToolResultPreservesProviderCallID(t *testing.T) {
+	messages := appendAbortedToolResults(nil, []ToolCall{{
+		ID: "call-1", ProviderCallID: "provider-1", Name: "read_file",
+	}})
+	if len(messages) != 1 || messages[0].ToolCallID != "call-1" || messages[0].ToolCallProviderID != "provider-1" || !messages[0].IsError {
+		t.Fatalf("aborted tool result lost provider identity: %#v", messages)
+	}
+}

internal/agent/guardrails.go

@@ -33,11 +33,11 @@ const (
 	// knows before spending more tool turns.
 	toolOnlyProgressReminderAt = 6
 
-	// planReminderTurn is the turn (1-based) by the end of which a multi-step
-	// task should have called update_plan; if it hasn't, a one-time reminder is
-	// injected. Set to 3 (not 2) so short, legitimate two-step tasks finish
-	// without a spurious planning nag.
-	planReminderTurn = 3
+	// planReminderTurn and planReminderToolThreshold keep bounded implementation
+	// work plan-free while still nudging a genuinely sustained run that has not
+	// established any structured progress. Both thresholds must be met.
+	planReminderTurn          = 7
+	planReminderToolThreshold = 7
 
 	// planToolName is the planning tool the loop watches for by name.
 	planToolName = "update_plan"
@@ -591,13 +591,12 @@ func (state *guardState) planReminder(turn int) string {
 		return planStaleReminder(state.toolCallsSincePlanUpdate)
 	}
 
-	// NOT-CALLED reminder: by the end of planReminderTurn the model should have
-	// called update_plan if it's doing a multi-step task (>=1 other tool call).
-	// One-shot for the whole run.
+	// NOT-CALLED reminder: once both the turn and tool-call thresholds are met,
+	// sustained work should have called update_plan. One-shot for the whole run.
 	if !state.notCalledReminderSent &&
 		!state.planEverCalled &&
 		turn >= planReminderTurn &&
-		state.totalToolCalls >= 1 {
+		state.totalToolCalls >= planReminderToolThreshold {
 		state.notCalledReminderSent = true
 		return planNotCalledReminder()
 	}

internal/agent/guardrails_test.go

@@ -257,19 +257,16 @@ func TestRunDoesNotCountDroppedToolCallTurnsAsEmpty(t *testing.T) {
 }
 
 func TestRunInjectsPlanNotCalledReminderForMultiStepTask(t *testing.T) {
+	const expectedThreshold = 7
+	if planReminderToolThreshold != expectedThreshold {
+		t.Fatalf("plan reminder tool threshold = %d, want %d", planReminderToolThreshold, expectedThreshold)
+	}
 	root := t.TempDir()
 	writeAgentTestFile(t, root+"/notes.txt", "alpha")
 	registry := tools.NewRegistry()
 	registry.Register(tools.NewScopedReadFileTool(root, nil))
 
-	provider := &mockProvider{
-		turns: [][]zeroruntime.StreamEvent{
-			toolTurn("call-1", "read_file", `{"path":"notes.txt"}`), // turn 1: other tool call
-			toolTurn("call-2", "read_file", `{"path":"notes.txt"}`), // turn 2: still no update_plan
-			toolTurn("call-3", "read_file", `{"path":"notes.txt"}`), // turn 3: reminder fires here
-			textTurn("done"),
-		},
-	}
+	provider := &mockProvider{turns: append(repeatedReadTurns(expectedThreshold), textTurn("done"))}
 
 	result, err := Run(context.Background(), "go", provider, Options{
 		Registry: registry,
@@ -287,6 +284,44 @@ func TestRunInjectsPlanNotCalledReminderForMultiStepTask(t *testing.T) {
 	}
 }
 
+func TestRunDoesNotInjectPlanReminderForBoundedToolSequence(t *testing.T) {
+	const expectedThreshold = 7
+	root := t.TempDir()
+	writeAgentTestFile(t, root+"/notes.txt", "alpha")
+	registry := tools.NewRegistry()
+	registry.Register(tools.NewScopedReadFileTool(root, nil))
+
+	provider := &mockProvider{turns: append(repeatedReadTurns(expectedThreshold-1), textTurn("done"))}
+	result, err := Run(context.Background(), "go", provider, Options{Registry: registry, MaxTurns: 12})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if result.FinalAnswer != "done" {
+		t.Fatalf("expected final answer, got %q", result.FinalAnswer)
+	}
+	if count := countUserMessagesContaining(result.Messages, planNotCalledReminderMarker); count != 0 {
+		t.Fatalf("bounded tool sequence must not draw a plan reminder, got %d", count)
+	}
+}
+
+func TestPlanReminderWaitsForTurnThresholdAfterEnoughToolCalls(t *testing.T) {
+	state := guardState{totalToolCalls: 7}
+	if got := state.planReminder(6); got != "" {
+		t.Fatalf("planReminder(6) = %q, want no reminder before turn threshold", got)
+	}
+	if state.notCalledReminderSent {
+		t.Fatal("early turn marked the not-called reminder as sent")
+	}
+}
+
+func repeatedReadTurns(count int) [][]zeroruntime.StreamEvent {
+	turns := make([][]zeroruntime.StreamEvent, 0, count)
+	for range count {
+		turns = append(turns, toolTurn("call", "read_file", `{"path":"notes.txt"}`))
+	}
+	return turns
+}
+
 func TestRunDoesNotInjectPlanReminderForTrivialTask(t *testing.T) {
 	root := t.TempDir()
 	writeAgentTestFile(t, root+"/notes.txt", "alpha")

internal/agent/loop.go

@@ -40,7 +40,15 @@ const (
 	toolResultControlSpecReview = "spec_review_required"
 )
 
-var errPermissionApprovalCanceled = errors.New("permission approval cancelled")
+// ErrPermissionApprovalCanceled ends a run because the caller cancelled a
+// permission prompt, rather than because anything failed.
+//
+// EXPORTED FOR THE SURFACES. A cancel is a normal ending and each surface says
+// so its own way — the TUI unwinds, and ACP has a "cancelled" stop reason for
+// exactly this. While it was unexported ACP could not distinguish it from a
+// fault and reported it as an internal error, so declining a tool looked like
+// the agent crashing.
+var ErrPermissionApprovalCanceled = errors.New("permission approval cancelled")
 
 // isImageRejectionError reports whether err is a provider 400 that rejects
 // image/multimodal content. This is checked BEFORE the compaction-retry path
@@ -133,6 +141,7 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 			}
 			options.Trace.Counter(trace.CounterInputTokens, int64(usage.InputTokens))
 			options.Trace.Counter(trace.CounterCachedInputTokens, int64(usage.CachedInputTokens))
+			options.Trace.Counter(trace.CounterCacheWriteTokens, int64(usage.CacheWriteTokens))
 			options.Trace.Counter(trace.CounterOutputTokens, int64(usage.OutputTokens))
 		}
 	}
@@ -689,11 +698,12 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 				turnRequestedModel = toolResult.RequestedModel
 			}
 			messages = append(messages, zeroruntime.Message{
-				Role:         zeroruntime.MessageRoleTool,
-				Content:      toolResult.ModelOutput(),
-				ToolCallID:   toolResult.ToolCallID,
-				IsError:      toolResult.Status == tools.StatusError,
-				ChangedFiles: append([]string(nil), toolResult.ChangedFiles...),
+				Role:               zeroruntime.MessageRoleTool,
+				Content:            toolResult.ModelOutput(),
+				ToolCallID:         toolResult.ToolCallID,
+				ToolCallProviderID: call.ProviderCallID,
+				IsError:            toolResult.Status == tools.StatusError,
+				ChangedFiles:       append([]string(nil), toolResult.ChangedFiles...),
 			})
 			// Images ride a following USER message rather than the tool result
 			// above. Every provider drops images on a tool-role message —
@@ -1027,6 +1037,9 @@ func historySafeToolCalls(calls []ToolCall) []ToolCall {
 	safe := make([]ToolCall, len(calls))
 	for i, call := range calls {
 		safe[i] = call
+		if call.Freeform {
+			continue
+		}
 		args := strings.TrimSpace(call.Arguments)
 		switch {
 		case args == "":
@@ -1110,8 +1123,28 @@ func decodeToolArguments(arguments string, v any) error {
 }
 
 func executeToolCall(ctx context.Context, registry *tools.Registry, call ToolCall, permissionMode PermissionMode, options Options) (ToolResult, error) {
+	tool, toolFound := registry.Get(call.Name)
 	args := map[string]any{}
-	if call.Arguments != "" {
+	if call.Freeform {
+		if !toolFound || !tools.IsBuiltInApplyPatch(tool) {
+			return ToolResult{
+				ToolCallID: call.ID,
+				Name:       call.Name,
+				Status:     tools.StatusError,
+				Output:     "Error: Unsupported freeform tool call for " + call.Name + ".",
+			}, nil
+		}
+		prepared, err := tools.PrepareFreeformApplyPatchArguments(tool, call.Arguments)
+		if err != nil {
+			return ToolResult{
+				ToolCallID: call.ID,
+				Name:       call.Name,
+				Status:     tools.StatusError,
+				Output:     "Error: Invalid freeform apply_patch input: " + err.Error(),
+			}, nil
+		}
+		args = prepared
+	} else if call.Arguments != "" {
 		if err := decodeToolArguments(call.Arguments, &args); err != nil {
 			return ToolResult{
 				ToolCallID: call.ID,
@@ -1139,7 +1172,6 @@ func executeToolCall(ctx context.Context, registry *tools.Registry, call ToolCal
 			DenialReason: DenialFiltered,
 		}, nil
 	}
-	tool, toolFound := registry.Get(call.Name)
 	if (permissionMode == PermissionModeSpecDraft || permissionMode == PermissionModePlan) && toolFound && !ToolAdvertised(tool, permissionMode) {
 		modeName := string(permissionMode)
 		return ToolResult{
@@ -1364,7 +1396,7 @@ func executeToolCall(ctx context.Context, registry *tools.Registry, call ToolCal
 			}
 		case PermissionDecisionCancel:
 			emitCanceledPermission(options, call, requestEvent, decisionReason)
-			return canceledPermissionResult(call, decisionReason, requestEvent), fmt.Errorf("%w for %s", errPermissionApprovalCanceled, call.Name)
+			return canceledPermissionResult(call, decisionReason, requestEvent), fmt.Errorf("%w for %s", ErrPermissionApprovalCanceled, call.Name)
 		default:
 			emitDeniedPermission(options, call, requestEvent, decisionReason)
 			return deniedPermissionResult(call, decisionReason, requestEvent), nil
@@ -1548,7 +1580,7 @@ func maybeRetryUnsandboxedAfterSandboxRestriction(ctx context.Context, registry
 	case PermissionDecisionCancel:
 		emitCanceledPermission(options, call, requestEvent, reason)
 		canceled := canceledPermissionResult(call, reason, requestEvent)
-		return result, &canceled, true, decision.Action, reason, nil, fmt.Errorf("%w for %s", errPermissionApprovalCanceled, call.Name)
+		return result, &canceled, true, decision.Action, reason, nil, fmt.Errorf("%w for %s", ErrPermissionApprovalCanceled, call.Name)
 	default:
 		emitDeniedPermission(options, call, requestEvent, reason)
 		denied := deniedPermissionResult(call, reason, requestEvent)
@@ -1596,7 +1628,7 @@ func maybeRetryWithNetworkAfterSandboxDenial(ctx context.Context, registry *tool
 	case PermissionDecisionCancel:
 		emitCanceledPermission(options, call, requestEvent, reason)
 		canceled := canceledPermissionResult(call, reason, requestEvent)
-		return result, &canceled, true, decision.Action, reason, fmt.Errorf("%w for %s", errPermissionApprovalCanceled, call.Name)
+		return result, &canceled, true, decision.Action, reason, fmt.Errorf("%w for %s", ErrPermissionApprovalCanceled, call.Name)
 	default:
 		emitDeniedPermission(options, call, requestEvent, reason)
 		denied := deniedPermissionResult(call, reason, requestEvent)
@@ -3087,13 +3119,15 @@ func partitionToolsCached(registry *tools.Registry, permissionMode PermissionMod
 	// Deferral may activate only when tool_search is actually runnable; otherwise
 	// the loop would hide deferred tools behind a loader the dispatch gate rejects
 	// — an inescapable dead-end. "Runnable" mirrors executeToolCall's gate:
-	// registered, not in DisabledTools, and advertised in the current permission
-	// mode (e.g. not spec-draft, where tool_search is not advertised). The
+	// registered, model-visible, not in DisabledTools, and advertised in the
+	// current permission mode (e.g. not spec-draft, where tool_search is not
+	// advertised). The
 	// EnabledTools allowlist is intentionally NOT checked here — tool_search is
 	// exempt from the allowlist at dispatch, so an allowlist that omits it must
 	// not disable deferral.
 	loader, loaderFound := registry.Get(tools.ToolSearchToolName)
 	loaderUsable := loaderFound &&
+		tools.ModelVisible(loader) &&
 		!containsToolName(options.DisabledTools, tools.ToolSearchToolName) &&
 		ToolAdvertised(loader, permissionMode)
 
@@ -3200,15 +3234,21 @@ func cachedRuntimeToolDefinition(defCache map[string]zeroruntime.ToolDefinition,
 // runtimeToolDefinition renders a tool's advertised definition (name, description,
 // JSON-schema parameters) as sent to the provider.
 func runtimeToolDefinition(tool tools.Tool) zeroruntime.ToolDefinition {
-	return zeroruntime.ToolDefinition{
+	definition := zeroruntime.ToolDefinition{
 		Name:        tool.Name(),
 		Description: tool.Description(),
 		Parameters:  schemaToRuntimeMap(tool.Parameters()),
 	}
+	if tools.IsBuiltInApplyPatch(tool) {
+		definition.Type = zeroruntime.ToolDefinitionFreeform
+	}
+	return definition
 }
 
 func ToolVisible(tool tools.Tool, permissionMode PermissionMode, enabledTools []string, disabledTools []string) bool {
-	return ToolAllowedByFilters(tool.Name(), enabledTools, disabledTools) && ToolAdvertised(tool, permissionMode)
+	return tools.ModelVisible(tool) &&
+		ToolAllowedByFilters(tool.Name(), enabledTools, disabledTools) &&
+		ToolAdvertised(tool, permissionMode)
 }
 
 func ToolAllowedByFilters(name string, enabledTools []string, disabledTools []string) bool {
@@ -3357,10 +3397,11 @@ func loadedToolsFromResult(meta map[string]string) []string {
 func appendAbortedToolResults(messages []Message, remaining []ToolCall) []Message {
 	for _, call := range remaining {
 		messages = append(messages, zeroruntime.Message{
-			Role:       zeroruntime.MessageRoleTool,
-			Content:    abortedToolResultNotice,
-			ToolCallID: call.ID,
-			IsError:    true,
+			Role:               zeroruntime.MessageRoleTool,
+			Content:            abortedToolResultNotice,
+			ToolCallID:         call.ID,
+			ToolCallProviderID: call.ProviderCallID,
+			IsError:            true,
 		})
 	}
 	return messages

internal/agent/loop_test.go

@@ -1853,7 +1853,7 @@ func TestRunAbortsWhenPermissionRequestCanceled(t *testing.T) {
 		},
 	})
 
-	if !errors.Is(err, errPermissionApprovalCanceled) {
+	if !errors.Is(err, ErrPermissionApprovalCanceled) {
 		t.Fatalf("expected permission approval cancel error, got %v", err)
 	}
 	if result.FinalAnswer != "" {
@@ -4096,7 +4096,7 @@ func TestRunDoesNotFlagCleanToolOutput(t *testing.T) {
 // caller's callback AND stamps token counters, and the run completes.
 func TestRunTracingWrapperStampsUsage(t *testing.T) {
 	provider := &mockProvider{turns: [][]zeroruntime.StreamEvent{{
-		{Type: zeroruntime.StreamEventUsage, Usage: zeroruntime.Usage{InputTokens: 100, CachedInputTokens: 20, OutputTokens: 40}},
+		{Type: zeroruntime.StreamEventUsage, Usage: zeroruntime.Usage{PromptTokens: 100, CachedInputTokens: 20, CacheWriteTokens: 10, CompletionTokens: 40}},
 		{Type: zeroruntime.StreamEventText, Content: "done"},
 		{Type: zeroruntime.StreamEventDone},
 	}}}
@@ -4135,6 +4135,9 @@ func TestRunTracingWrapperStampsUsage(t *testing.T) {
 	if got := tr.Counter(trace.CounterCachedInputTokens); got != 20 {
 		t.Fatalf("cached input token counter = %d, want 20", got)
 	}
+	if got := tr.Counter(trace.CounterCacheWriteTokens); got != 10 {
+		t.Fatalf("cache-write token counter = %d, want 10", got)
+	}
 	if got := tr.Counter(trace.CounterOutputTokens); got != 40 {
 		t.Fatalf("output token counter = %d, want 40", got)
 	}
@@ -4340,3 +4343,95 @@ func TestPlanModeHonorsBeforeToolVeto(t *testing.T) {
 		t.Fatalf("expected tool result to mention the beforeTool veto, got %q", combined)
 	}
 }
+
+// A cancelled permission on either sandbox-retry path must abort the run with a
+// recognisable cancellation, and must not run the escalated retry.
+//
+// BOTH PATHS, because both wrap ErrPermissionApprovalCanceled and each is
+// reached by a different kind of denial: one by an unrestricted platform denial
+// asking for approval, the other by an external-network denial. Surfaces map
+// this sentinel onto their own idea of a cancel — ACP returns stopReason
+// "cancelled" for it — so a path that produced a bare error instead would show
+// the user a crash where they had simply declined.
+func TestCancellingASandboxRetryAbortsWithoutRetrying(t *testing.T) {
+	denial := func(capability execution.CapabilityKind, scope string) tools.Result {
+		return tools.Result{
+			Status: tools.StatusError,
+			ExecutionOutcome: &execution.Outcome{
+				State: execution.StateDenied,
+				Kind:  execution.OutcomeEnforcementDenied,
+				Denial: &execution.Denial{
+					Capability:  execution.Capability{Kind: capability, Scope: scope},
+					Source:      execution.DenialSourcePlatformSandbox,
+					Reason:      "denied by the sandbox",
+					Recoverable: true,
+					NextAction:  execution.DenialNextActionRequestApproval,
+				},
+			},
+		}
+	}
+
+	for _, testCase := range []struct {
+		name   string
+		result tools.Result
+		run    func(context.Context, *tools.Registry, ToolCall, tools.Tool, map[string]any, tools.Result, Options) error
+	}{
+		{
+			name:   "unsandboxed retry",
+			result: denial(execution.CapabilityUnrestricted, "host"),
+			run: func(ctx context.Context, registry *tools.Registry, call ToolCall, tool tools.Tool, args map[string]any, result tools.Result, options Options) error {
+				_, _, _, _, _, _, abortErr := maybeRetryUnsandboxedAfterSandboxRestriction(
+					ctx, registry, call, tool, args, result, PermissionModeAsk, options, nil)
+				return abortErr
+			},
+		},
+		{
+			name:   "network retry",
+			result: denial(execution.CapabilityExternalNetwork, ""),
+			run: func(ctx context.Context, registry *tools.Registry, call ToolCall, tool tools.Tool, args map[string]any, result tools.Result, options Options) error {
+				_, _, _, _, _, abortErr := maybeRetryWithNetworkAfterSandboxDenial(
+					ctx, registry, call, tool, args, result, PermissionModeAsk, options, nil)
+				return abortErr
+			},
+		},
+	} {
+		t.Run(testCase.name, func(t *testing.T) {
+			retryTool := &sandboxNamespaceLimitedRetryTool{}
+			registry := tools.NewRegistry()
+			registry.Register(retryTool)
+
+			asked := 0
+			options := Options{
+				Registry:       registry,
+				PermissionMode: PermissionModeAsk,
+				Autonomy:       "medium",
+				Sandbox: sandbox.NewEngine(sandbox.EngineOptions{
+					WorkspaceRoot: t.TempDir(),
+					Policy:        sandbox.DefaultPolicy(),
+				}),
+				OnPermissionRequest: func(context.Context, PermissionRequest) (PermissionDecision, error) {
+					asked++
+					return PermissionDecision{Action: PermissionDecisionCancel, Reason: "client cancelled"}, nil
+				},
+			}
+
+			call := ToolCall{ID: "call-1", Name: "bash", Arguments: `{"command":"curl example.com"}`}
+			args := map[string]any{"command": "curl example.com"}
+
+			abortErr := testCase.run(context.Background(), registry, call, retryTool, args, testCase.result, options)
+
+			if asked != 1 {
+				t.Fatalf("permission was requested %d times, want exactly 1", asked)
+			}
+			if !errors.Is(abortErr, ErrPermissionApprovalCanceled) {
+				t.Fatalf("abort error = %v, want it to match ErrPermissionApprovalCanceled", abortErr)
+			}
+			// The escalated retry is the thing the permission was gating. A
+			// cancelled prompt that still ran it would have run the command the
+			// user just declined.
+			if len(retryTool.calls) != 0 {
+				t.Fatalf("the escalated retry ran %d times after a cancel: %+v", len(retryTool.calls), retryTool.calls)
+			}
+		})
+	}
+}

internal/agent/partition_cache_test.go

@@ -31,6 +31,19 @@ func (t countingSchemaTool) Run(_ context.Context, _ map[string]any) tools.Resul
 	return tools.Result{Status: tools.StatusOK}
 }
 
+func TestRuntimeToolDefinitionMarksOnlyBuiltInApplyPatchFreeform(t *testing.T) {
+	builtIn := runtimeToolDefinition(tools.NewScopedApplyPatchTool(t.TempDir(), nil))
+	if builtIn.Type != zeroruntime.ToolDefinitionFreeform {
+		t.Fatalf("built-in apply_patch type = %q, want freeform", builtIn.Type)
+	}
+
+	calls := 0
+	custom := runtimeToolDefinition(countingSchemaTool{name: "apply_patch", calls: &calls})
+	if custom.Type != "" {
+		t.Fatalf("custom apply_patch type = %q, want legacy function shape", custom.Type)
+	}
+}
+
 // The cache renders a tool's schema once and reuses it across calls, and its
 // output is identical to the uncached path.
 func TestPartitionToolsCacheRendersOnceAndMatchesUncached(t *testing.T) {

internal/agent/prompt_budget_test.go

@@ -67,3 +67,21 @@ func TestEagerToolSchemaTokenBudget(t *testing.T) {
 		t.Fatalf("eager tool schemas are %d tokens, over the %d ceiling — trim a schema, drop a core tool, or raise the ceiling deliberately (deferring will NOT help: this test disables deferral)", got, maxEagerToolSchemaTokens)
 	}
 }
+
+func TestAgentAdvertisesBothEditTools(t *testing.T) {
+	registry := tools.NewRegistry()
+	for _, tool := range tools.CoreToolsScoped(t.TempDir(), nil) {
+		registry.Register(tool)
+	}
+	exposed, _ := partitionTools(registry, PermissionModeAsk, Options{}, map[string]bool{})
+	names := make(map[string]bool, len(exposed))
+	for _, definition := range exposed {
+		names[definition.Name] = true
+	}
+	if !names["apply_patch"] {
+		t.Fatal("agent must retain apply_patch for multi-hunk changes")
+	}
+	if !names["edit_file"] {
+		t.Fatal("agent must receive edit_file for targeted exact replacements")
+	}
+}

internal/agent/prompt_fingerprint.go

@@ -58,12 +58,18 @@ func toolSubstrings(exposed []zeroruntime.ToolDefinition) (toolsSubstr, schemaSu
 	for _, def := range exposed {
 		writeLengthPrefixed(&toolsSB, def.Name)
 		writeLengthPrefixed(&toolsSB, def.Description)
+		writeLengthPrefixed(&toolsSB, string(def.Type))
 		// Parameters is rendered to a canonical JSON string per tool. The
 		// schema-render cache in internal/agent (used by partitionToolsCached)
 		// guarantees the same render is byte-identical across turns for the
 		// same tool, so this substring is a stable hash input.
 		writeLengthPrefixed(&schemaSB, def.Name)
 		writeLengthPrefixed(&schemaSB, canonicalSchemaString(def.Parameters))
+		if def.Format != nil {
+			writeLengthPrefixed(&schemaSB, def.Format.Type)
+			writeLengthPrefixed(&schemaSB, def.Format.Syntax)
+			writeLengthPrefixed(&schemaSB, def.Format.Definition)
+		}
 	}
 	return toolsSB.String(), schemaSB.String()
 }

internal/agent/prompt_fingerprint_test.go

@@ -73,6 +73,38 @@ func TestComputePrefixFingerprintSchemaChangeChangesSchemaHash(t *testing.T) {
 	}
 }
 
+func TestComputePrefixFingerprintIncludesToolTypeAndFormat(t *testing.T) {
+	opts := Options{Cwd: t.TempDir(), SystemPrompt: "core"}
+	base := zeroruntime.ToolDefinition{Name: "apply_patch", Description: "Patch files"}
+	baseFingerprint := ComputePrefixFingerprint(opts, []zeroruntime.ToolDefinition{base})
+
+	typed := base
+	typed.Type = zeroruntime.ToolDefinitionFreeform
+	if got := ComputePrefixFingerprint(opts, []zeroruntime.ToolDefinition{typed}); got.ToolsHash == baseFingerprint.ToolsHash {
+		t.Fatal("ToolsHash must change when tool Type changes")
+	}
+
+	formatCases := []struct {
+		name   string
+		format zeroruntime.ToolDefinitionFormat
+	}{
+		{name: "type", format: zeroruntime.ToolDefinitionFormat{Type: "grammar"}},
+		{name: "syntax", format: zeroruntime.ToolDefinitionFormat{Syntax: "lark"}},
+		{name: "definition", format: zeroruntime.ToolDefinitionFormat{Definition: "start: PATCH"}},
+		{name: "empty", format: zeroruntime.ToolDefinitionFormat{}},
+	}
+	for _, test := range formatCases {
+		t.Run(test.name, func(t *testing.T) {
+			withFormat := base
+			withFormat.Format = &test.format
+			got := ComputePrefixFingerprint(opts, []zeroruntime.ToolDefinition{withFormat})
+			if got.SchemaHash == baseFingerprint.SchemaHash {
+				t.Fatalf("SchemaHash must change for %s format input", test.name)
+			}
+		})
+	}
+}
+
 // TestComputePrefixFingerprintSystemPromptChangeChangesBaseHash asserts the
 // most common drift path: a system-prompt edit (e.g. an agent.md update, a
 // model addendum change) must move the base-instructions hash, which moves

internal/agent/system_prompt.md

@@ -30,13 +30,10 @@ work.
    read-before-edit discipline: inspect the target file and nearby callers,
    tests, or config before you modify behavior. Never edit a file you have not
    read.
-2. **Plan.** Use update_plan for implementation or investigation that has at
-   least three meaningful dependent steps, then keep it current at milestones.
-   Mark completed work and the next in-progress step together when practical;
-   do not spend separate turns updating it after every file or command. Keep at
-   most one item in_progress. Skip plans for simple lookups, explanations, code
-   navigation, and other short tasks. Never create a plan after the work is
-   already complete merely to describe what you did.
+2. **Plan.** Use update_plan for multi-component, sequencing-uncertain, or long
+   work. Skip it for bounded changes in one component. Update only when the
+   overall phase changes, keep at most one item in_progress, and never create a
+   plan after the work is complete.
 3. **Implement.** Make focused changes that match the surrounding code's style,
    naming, and conventions. Prefer the smallest change that fully solves the
    problem. Avoid broad refactors, unrelated rewrites, dependency churn, and
@@ -52,37 +49,48 @@ work.
 
 - Choose the narrowest tool that safely accomplishes the step. Prefer native
   file tools - read_file, read_minified_file, list_directory, glob, grep,
-  write_file, edit_file, apply_patch - over shelling out to
+  edit_file, apply_patch, write_file - over shelling out to
   cat/sed/awk/python for file operations.
   They are safer, reviewable, and produce clean diffs.
-- Prefer read_minified_file when initially exploring source code; it preserves
-  code while removing comments and redundant whitespace. Use read_file when
-  exact text, comments, or line numbers are needed.
+- Use read_minified_file only to explore large or unfamiliar source. Use
+  read_file for small or likely edit targets and exact text, comments, or line
+  numbers. Do not read both unless a new need for exact content appears.
 - Keep edits focused and reviewable. A single patch may update several related
   files when they form one coherent change; do not hide unrelated edits in a
   bulk shell or script rewrite.
-- For edits to existing files, prefer edit_file or apply_patch with minimal,
-  targeted diffs. Match the existing indentation, imports, and idioms. Match the
-  file's comment density: do not add explanatory comments unless the user asks or
-  the code is already comment-dense.
+- For edits to existing files, use edit_file for a targeted change (old_string
+  must match the file exactly and be unique, so include a few surrounding
+  lines) and apply_patch when one coherent change spans several hunks or
+  files. Use write_file only to create a file or when most of it changes; do
+  not rewrite a whole file to change a few lines. Match the existing
+  indentation, imports, and idioms. Match the file's comment density: do not
+  add explanatory comments unless the user asks or the code is already
+  comment-dense.
+- A successful edit result already confirms the change; do not re-read a file
+  just to verify an edit that succeeded. If an edit fails, read the error, fix
+  the old_string or hunk, and retry the same tool rather than switching to a
+  full rewrite.
 - Solve the problem as posed, not a more general version of it. Add no
   speculative abstraction, configurability, or handling for cases that cannot
   occur, and nothing the user did not ask for. A small diff can still be
-  over-built; if a 200-line solution could be 50, rewrite it.
+  over-built; if a 200-line solution could be 50, rewrite it. Once the required
+  behavior passes validation, stop instead of adding optional cleanup.
 - Preserve behavior you were not asked to change. Do not delete or rewrite code
   you did not author unless the task requires it; if you must, say so.
 
 ## Testing gate (mandatory)
 
-- After any change to code, verify after edits by running the project's
-  validators before you summarize or commit: tests, type-checks, linters, and/or
-  the build, as appropriate. Scope them to the change while iterating; reserve
-  full-suite runs for milestones.
-- If you are unsure which validators apply, search the repo (Makefile, package
-  manifests, CI config) to find them.
+- After code changes, run the project's documented appropriate validators.
+  Scope iteration checks, combine compatible commands when diagnostics stay
+  useful, and run the final set once after the last edit. Rerun only after a
+  change or failure.
+- If unsure which entry points apply, inspect the Makefile, manifests, or CI;
+  do not invent a parallel flow.
 - Never claim a task is done, and never commit, while validators are failing. If
   they fail, fix the cause and rerun; do not paper over it. If you could not run
   a validator, say so explicitly rather than implying success.
+- A successful native patch confirms the edit. Reread only when the next change
+  needs exact content or the result was ambiguous.
 
 ## Tool use
 
@@ -104,7 +112,7 @@ work.
   you need to clean up a running foreground command yourself, use write_stdin.
 - write_stdin's session_id is only ever an id returned by a still-running
   exec_command; never guess or probe ids. If you have no such session, start one
-  with exec_command, or use write_file/edit_file/apply_patch for file changes.
+  with exec_command, or use edit_file/apply_patch/write_file for file changes.
 - write_stdin with empty input polls an existing exec_command session, and
   `\u0003` interrupts it. Sending other stdin bytes may require approval because
   it can drive the running process beyond the original command. Non-tty sessions
@@ -140,6 +148,7 @@ work.
 - Default to concise, skimmable output. Lead with the answer or the result.
 - Use GitHub-flavored Markdown: headings to structure longer replies, fenced
   code blocks for code, and `inline code` for file paths, commands, symbols, and
-  short snippets. Reference code as `file:line` so it is clickable.
+  short snippets. Reference code with file paths and include line numbers when
+  already known; do not look them up solely for the final summary.
 - Report outcomes faithfully: if tests failed, show it; if a step was skipped,
   say so; when something is done and verified, state it plainly without hedging.

internal/agent/system_prompt_models.go

@@ -60,8 +60,11 @@ const openAIPromptAddendum = `<model_guidance>
   longer answers, fenced code blocks for code, and ` + "`inline code`" + ` for paths,
   commands, and symbols.
 - Strongly prefer the native file tools (read_file, list_directory, grep, glob,
-  write_file, edit_file, apply_patch) over shelling out to cat/sed/awk/python for
-  file work. Make one tool call per file; do not batch file writes into a script.
+  edit_file, apply_patch, write_file) over shelling out to cat/sed/awk/python for
+  file work. Use them directly; never run apply_patch through exec_command.
+  read_file, edit_file and write_file take one file per call, while one coherent
+  apply_patch may span several files. Keep independent native calls in the same
+  turn, and do not batch file writes into a script.
 - Persist until the task is fully handled this turn: gather context, implement,
   run the validators, and report — do not stop at a partial result.
 </model_guidance>`

internal/agent/system_prompt_models_test.go

@@ -29,6 +29,9 @@ func TestBuildSystemPromptAppendsModelAddendum(t *testing.T) {
 	if got := buildSystemPrompt(Options{Model: "gpt-5"}); !strings.Contains(got, openAIPromptAddendum) {
 		t.Fatalf("expected the OpenAI addendum in the gpt-5 prompt")
 	}
+	if got := strings.Join(strings.Fields(strings.ToLower(buildSystemPrompt(Options{Model: "gpt-5"}))), " "); !strings.Contains(got, "never run apply_patch through exec_command") {
+		t.Fatalf("OpenAI prompt must route edits through the native patch tool:\n%s", got)
+	}
 	// Claude is aligned with the core prompt and gets no family addendum now that
 	// comment discipline is universal; it must not pick up another family's block.
 	claude := buildSystemPrompt(Options{Model: "claude-opus-4-6"})

internal/agent/system_prompt_test.go

@@ -29,14 +29,17 @@ func TestMain(m *testing.M) {
 }
 
 func TestCoreSystemPromptIncludesCodingQualityRules(t *testing.T) {
-	prompt := strings.ToLower(buildSystemPrompt(Options{}))
+	prompt := strings.Join(strings.Fields(strings.ToLower(buildSystemPrompt(Options{}))), " ")
+	if strings.Contains(prompt, "clickable file paths") {
+		t.Fatalf("system prompt must not claim inline-code file paths are clickable: %s", prompt)
+	}
 
 	for _, want := range []string{
 		"read-before-edit",
 		"inspect the target file",
 		"plan then act",
 		"choose the narrowest tool",
-		"prefer edit_file or apply_patch",
+		"for edits to existing files, use edit_file",
 		"verify after edits",
 		"honor the active permission mode",
 		"avoid broad refactors",
@@ -44,6 +47,13 @@ func TestCoreSystemPromptIncludesCodingQualityRules(t *testing.T) {
 		"do not recognize",
 		"scaled to the work",
 		"comment density",
+		"skip it for bounded changes in one component",
+		"do not read both unless a new need for exact content appears",
+		"combine compatible commands when diagnostics stay useful",
+		"do not invent a parallel flow",
+		"a successful native patch confirms the edit",
+		"once the required behavior passes validation, stop",
+		"do not look them up solely for the final summary",
 	} {
 		if !strings.Contains(prompt, want) {
 			t.Fatalf("expected core system prompt to include %q, got:\n%s", want, buildSystemPrompt(Options{}))

internal/agenteval/trace.go

@@ -29,10 +29,6 @@ func ParseTraceEventKeys(stdout string) []string {
 	return keys
 }
 
-func TraceEventKeys(stdout string) []string {
-	return ParseTraceEventKeys(stdout)
-}
-
 func MissingTraceEvents(required []string, stdout string) []string {
 	seen := map[string]bool{}
 	for _, key := range ParseTraceEventKeys(stdout) {

internal/background/manager.go

@@ -453,7 +453,12 @@ func (manager *Manager) normalizeLoadedTask(fileTaskID string, task Task) (Task,
 	}
 	outputFile, err := manager.outputFile(task.ID, task.OutputFile)
 	if err != nil {
-		return Task{}, false, err
+		var migrated bool
+		outputFile, migrated = manager.migrateLegacyOutputFile(task.ID, task.OutputFile)
+		if !migrated {
+			return Task{}, false, err
+		}
+		changed = true
 	}
 	if outputFile != task.OutputFile {
 		changed = true
@@ -562,6 +567,32 @@ func (manager *Manager) outputFile(taskID string, requested string) (string, err
 	return path, nil
 }
 
+// migrateLegacyOutputFile recovers task metadata written under a previous home
+// or XDG data root. It accepts only the canonical per-task output
+// name in the historic zero/background layout, and only when the corresponding
+// regular file already exists inside the active manager root.
+func (manager *Manager) migrateLegacyOutputFile(taskID string, requested string) (string, bool) {
+	requested = strings.TrimSpace(requested)
+	if !filepath.IsAbs(requested) {
+		return "", false
+	}
+	requested = filepath.Clean(requested)
+	expectedName := taskID + ".ndjson"
+	if filepath.Base(requested) != expectedName {
+		return "", false
+	}
+	legacyRoot := filepath.Dir(requested)
+	if filepath.Base(legacyRoot) != "background" || filepath.Base(filepath.Dir(legacyRoot)) != "zero" {
+		return "", false
+	}
+	canonical := filepath.Join(manager.rootDir, expectedName)
+	info, err := os.Lstat(canonical)
+	if err != nil || !info.Mode().IsRegular() {
+		return "", false
+	}
+	return canonical, true
+}
+
 func validTaskID(taskID string) bool {
 	return taskIDPattern.MatchString(strings.TrimSpace(taskID))
 }

internal/background/manager_test.go

@@ -1,6 +1,7 @@
 package background
 
 import (
+	"encoding/json"
 	"errors"
 	"os"
 	"path/filepath"
@@ -191,6 +192,88 @@ func TestManagerSkipsInvalidPersistedMetadata(t *testing.T) {
 	}
 }
 
+func TestManagerMigratesLegacyOutputPathWhenCanonicalOutputExists(t *testing.T) {
+	root := t.TempDir()
+	const taskID = "legacy_task"
+	canonicalOutput := filepath.Join(root, taskID+".ndjson")
+	if err := os.WriteFile(canonicalOutput, []byte("legacy output\n"), 0o600); err != nil {
+		t.Fatalf("write canonical output: %v", err)
+	}
+	legacyOutput := filepath.Join(t.TempDir(), "zero", "background", taskID+".ndjson")
+	metadata, err := json.Marshal(Task{
+		ID:         taskID,
+		Type:       "specialist",
+		Status:     StatusCompleted,
+		OutputFile: legacyOutput,
+		StartedAt:  time.Date(2026, 8, 1, 10, 0, 0, 0, time.UTC),
+	})
+	if err != nil {
+		t.Fatalf("marshal legacy metadata: %v", err)
+	}
+	if err := os.WriteFile(filepath.Join(root, taskID+".json"), append(metadata, '\n'), 0o600); err != nil {
+		t.Fatalf("write legacy metadata: %v", err)
+	}
+
+	manager, err := NewManager(root)
+	if err != nil {
+		t.Fatalf("NewManager returned error: %v", err)
+	}
+	task, ok := manager.Get(taskID)
+	if !ok {
+		t.Fatal("manager did not load migrated task")
+	}
+	if task.OutputFile != canonicalOutput {
+		t.Fatalf("migrated output file = %q, want %q", task.OutputFile, canonicalOutput)
+	}
+	if warnings := manager.LoadWarnings(); len(warnings) != 0 {
+		t.Fatalf("migration produced load warnings: %#v", warnings)
+	}
+
+	persisted, err := os.ReadFile(filepath.Join(root, taskID+".json"))
+	if err != nil {
+		t.Fatalf("read migrated metadata: %v", err)
+	}
+	var saved Task
+	if err := json.Unmarshal(persisted, &saved); err != nil {
+		t.Fatalf("decode migrated metadata: %v", err)
+	}
+	if saved.OutputFile != canonicalOutput {
+		t.Fatalf("persisted output file = %q, want %q", saved.OutputFile, canonicalOutput)
+	}
+}
+
+func TestManagerRejectsUnrelatedAbsoluteOutputPathDuringMigration(t *testing.T) {
+	root := t.TempDir()
+	const taskID = "legacy_task"
+	if err := os.WriteFile(filepath.Join(root, taskID+".ndjson"), []byte("output\n"), 0o600); err != nil {
+		t.Fatalf("write canonical output: %v", err)
+	}
+	metadata, err := json.Marshal(Task{
+		ID:         taskID,
+		Type:       "specialist",
+		Status:     StatusCompleted,
+		OutputFile: filepath.Join(t.TempDir(), taskID+".ndjson"),
+		StartedAt:  time.Date(2026, 8, 1, 10, 0, 0, 0, time.UTC),
+	})
+	if err != nil {
+		t.Fatalf("marshal metadata: %v", err)
+	}
+	if err := os.WriteFile(filepath.Join(root, taskID+".json"), append(metadata, '\n'), 0o600); err != nil {
+		t.Fatalf("write metadata: %v", err)
+	}
+
+	manager, err := NewManager(root)
+	if err != nil {
+		t.Fatalf("NewManager returned error: %v", err)
+	}
+	if _, ok := manager.Get(taskID); ok {
+		t.Fatal("manager loaded task with an unrelated absolute output path")
+	}
+	if warnings := strings.Join(manager.LoadWarnings(), "\n"); !strings.Contains(warnings, "output file must be inside") {
+		t.Fatalf("load warnings = %q, want containment rejection", warnings)
+	}
+}
+
 func TestManagerMarksReloadedRunningTaskNonKillable(t *testing.T) {
 	root := t.TempDir()
 	manager, err := NewManager(root)

internal/background/process_posix.go

@@ -39,3 +39,21 @@ func ConfigureChildProcessGroup(cmd *exec.Cmd) {
 func terminateProcess(pid int) error {
 	return execution.TerminateProcessTree(pid, terminationGracePeriod, terminationPollInterval)
 }
+
+// terminateOwnedProcess terminates cmd's process group directly when its launch
+// configuration proves it was made a group leader. This avoids fragile Getpgid
+// rediscovery after an owned leader exits. Ordinary commands fall back to the
+// safe PID/tree path rather than assuming their PID is also a process-group ID.
+//
+// The Setpgid && Pgid == 0 guard only recognizes ConfigureChildProcessGroup's
+// own convention. A command made its own session leader via Setsid (as opposed
+// to Setpgid) is also its own process-group leader in practice, but takes the
+// slower rediscovery path here since Setsid isn't checked. Harmless today
+// because TerminateCommand has exactly one caller in this codebase; worth
+// covering explicitly if Setsid-configured commands start using this path too.
+func terminateOwnedProcess(cmd *exec.Cmd) (bool, error) {
+	if cmd.SysProcAttr != nil && cmd.SysProcAttr.Setpgid && cmd.SysProcAttr.Pgid == 0 {
+		return false, execution.TerminateProcessGroup(cmd.Process.Pid, terminationGracePeriod, terminationPollInterval)
+	}
+	return false, terminateProcess(cmd.Process.Pid)
+}

internal/background/process_posix_test.go

@@ -147,11 +147,12 @@ func TestTerminateProcessKillsForkedChildren(t *testing.T) {
 		t.Fatalf("terminateProcess: %v", err)
 	}
 
-	// The forked child must be gone too (poll until reaped by init).
+	// The forked child must no longer be running. An orphaned zombie is already
+	// dead but may remain visible briefly until the platform's init reaps it.
 	deadline := time.Now().Add(2 * time.Second)
-	// Only ESRCH proves the child is gone; any other error (e.g. EPERM) would
-	// wrongly pass the test, so treat it as still-present and keep polling.
-	for !errors.Is(syscall.Kill(childPID, syscall.Signal(0)), syscall.ESRCH) {
+	// processStopped treats only ESRCH or an observed zombie state as stopped;
+	// other errors (for example EPERM) remain live and keep polling.
+	for !processStopped(childPID) {
 		if time.Now().After(deadline) {
 			_ = syscall.Kill(childPID, syscall.SIGKILL)
 			t.Fatalf("forked child %d survived terminateProcess — group kill failed", childPID)
@@ -159,3 +160,73 @@ func TestTerminateProcessKillsForkedChildren(t *testing.T) {
 		time.Sleep(20 * time.Millisecond)
 	}
 }
+
+func TestTerminateCommandStopsUnconfiguredCommand(t *testing.T) {
+	cmd := exec.Command("sleep", "30")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	t.Cleanup(func() {
+		if cmd.ProcessState == nil {
+			_ = cmd.Process.Kill()
+		}
+	})
+
+	if err := TerminateCommand(cmd); err != nil {
+		t.Fatalf("TerminateCommand: %v", err)
+	}
+	if cmd.ProcessState == nil {
+		t.Fatal("unconfigured command was not reaped")
+	}
+}
+
+func TestTerminateCommandKillsChildAfterLeaderExits(t *testing.T) {
+	grace, poll := terminationGracePeriod, terminationPollInterval
+	terminationGracePeriod, terminationPollInterval = 2*time.Second, 20*time.Millisecond
+	t.Cleanup(func() { terminationGracePeriod, terminationPollInterval = grace, poll })
+
+	// The leader exits immediately after launching the child. TerminateCommand
+	// must capture and signal the process group before Wait reaps the leader and
+	// makes its group identity unavailable.
+	cmd := exec.Command("sh", "-c", "sleep 300 & echo $!; exit 0")
+	ConfigureChildProcessGroup(cmd)
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		t.Fatalf("stdout pipe: %v", err)
+	}
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	line, err := bufio.NewReader(stdout).ReadString('\n')
+	if err != nil {
+		t.Fatalf("read forked child pid: %v", err)
+	}
+	childPID, err := strconv.Atoi(strings.TrimSpace(line))
+	if err != nil {
+		t.Fatalf("parse forked child pid %q: %v", line, err)
+	}
+
+	if err := TerminateCommand(cmd); err != nil {
+		t.Fatalf("TerminateCommand: %v", err)
+	}
+
+	deadline := time.Now().Add(2 * time.Second)
+	for !processStopped(childPID) {
+		if time.Now().After(deadline) {
+			_ = syscall.Kill(childPID, syscall.SIGKILL)
+			t.Fatalf("forked child %d survived TerminateCommand", childPID)
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+}
+
+func processStopped(pid int) bool {
+	if errors.Is(syscall.Kill(pid, syscall.Signal(0)), syscall.ESRCH) {
+		return true
+	}
+	state, err := exec.Command("ps", "-o", "stat=", "-p", strconv.Itoa(pid)).Output()
+	if err != nil {
+		return errors.Is(syscall.Kill(pid, syscall.Signal(0)), syscall.ESRCH)
+	}
+	return strings.HasPrefix(strings.TrimSpace(string(state)), "Z")
+}

internal/background/process_windows.go

@@ -3,11 +3,20 @@
 package background
 
 import (
+	"fmt"
 	"os/exec"
 
 	"github.com/Gitlawb/zero/internal/execution"
+	"golang.org/x/sys/windows"
 )
 
+// stillActiveExitCode is the documented GetExitCodeProcess value for a process
+// that has not terminated. x/sys/windows does not expose Windows' STILL_ACTIVE
+// constant.
+const stillActiveExitCode uint32 = 259
+
+var terminateProcessForTest = terminateProcess
+
 // ConfigureChildProcessGroup is a no-op on Windows: process-tree termination is
 // delegated to execution.TerminateProcessTree, so no launch-time process-group
 // setup is required (the POSIX build sets Setpgid here instead).
@@ -16,3 +25,28 @@ func ConfigureChildProcessGroup(cmd *exec.Cmd) { execution.ConfigureProcessGroup
 func terminateProcess(pid int) error {
 	return execution.TerminateProcessTree(pid, 0, 0)
 }
+
+// terminateOwnedProcess asks taskkill /T to terminate the tree rooted at cmd,
+// with KillProcessTree's direct Process.Kill fallback if taskkill fails. taskkill
+// can discover descendants only while the root PID still exists; unlike a POSIX
+// process group, a Windows tree has no independently addressable identity after
+// its root exits.
+func terminateOwnedProcess(cmd *exec.Cmd) (bool, error) {
+	var (
+		alreadyExited bool
+		terminateErr  error
+	)
+	err := cmd.Process.WithHandle(func(handle uintptr) {
+		var exitCode uint32
+		if windows.GetExitCodeProcess(windows.Handle(handle), &exitCode) == nil {
+			alreadyExited = exitCode != stillActiveExitCode
+		}
+		// Keep the exact process identity pinned while the PID-based taskkill
+		// operation runs, preventing the PID from being recycled underneath it.
+		terminateErr = terminateProcessForTest(cmd.Process.Pid)
+	})
+	if err != nil {
+		return false, fmt.Errorf("pin process %d for termination: %w", cmd.Process.Pid, err)
+	}
+	return alreadyExited, terminateErr
+}

internal/background/process_windows_test.go

@@ -0,0 +1,106 @@
+//go:build windows
+
+package background
+
+import (
+	"bufio"
+	"errors"
+	"os/exec"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestTerminateCommandReturnsTreeFailureAfterRootFallbackReaps(t *testing.T) {
+	cmd := exec.Command("powershell.exe", "-NoProfile", "-NonInteractive", "-Command", "Start-Sleep -Seconds 300")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	treeErr := errors.New("taskkill /T failed")
+	originalTerminateProcess := terminateProcessForTest
+	terminateProcessForTest = func(pid int) error {
+		if err := cmd.Process.Kill(); err != nil {
+			return errors.Join(treeErr, err)
+		}
+		return treeErr
+	}
+	t.Cleanup(func() { terminateProcessForTest = originalTerminateProcess })
+
+	err := TerminateCommand(cmd)
+	if !errors.Is(err, treeErr) {
+		t.Fatalf("TerminateCommand error = %v, want tree failure", err)
+	}
+	if cmd.ProcessState == nil {
+		t.Fatal("root process was not reaped")
+	}
+}
+
+func TestTerminateCommandReapsExitedLeader(t *testing.T) {
+	cmd := exec.Command("cmd.exe", "/c", "exit", "0")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	// Let the child exit without calling Wait so cleanup exercises the Windows
+	// taskkill/TerminateProcess race while it still owns the process handle.
+	time.Sleep(500 * time.Millisecond)
+
+	// jatmn's #774 finding: taskkill /T racing an already-exited PID (and the
+	// Process.Kill fallback) both fail here, but the reap below still succeeds —
+	// the process-handle exit-code check proves the leader was already gone, so
+	// TerminateCommand must not surface the expected kill-attempt error.
+	if err := TerminateCommand(cmd); err != nil {
+		t.Fatalf("TerminateCommand: %v, want nil (leader was already gone and got reaped)", err)
+	}
+	if cmd.ProcessState == nil {
+		t.Fatal("exited process was not reaped")
+	}
+}
+
+func TestTerminateCommandDeadLeaderCannotIdentifyDescendantTree(t *testing.T) {
+	cmd := exec.Command("powershell.exe", "-NoProfile", "-NonInteractive", "-Command",
+		`$p = Start-Process powershell.exe -ArgumentList '-NoProfile','-Command','Start-Sleep -Seconds 300' -PassThru; $p.Id`)
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		t.Fatalf("stdout pipe: %v", err)
+	}
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	line, err := bufio.NewReader(stdout).ReadString('\n')
+	if err != nil {
+		t.Fatalf("read descendant pid: %v", err)
+	}
+	descendantPID, err := strconv.Atoi(strings.TrimSpace(line))
+	if err != nil {
+		t.Fatalf("parse descendant pid %q: %v", line, err)
+	}
+	t.Cleanup(func() {
+		_ = exec.Command("taskkill.exe", "/F", "/PID", strconv.Itoa(descendantPID)).Run()
+	})
+
+	// Wait until the leader is observably exited but deliberately leave it
+	// unreaped, matching the POSIX regression's ordering.
+	deadline := time.Now().Add(5 * time.Second)
+	for processExistsOnWindows(cmd.Process.Pid) {
+		if time.Now().After(deadline) {
+			t.Fatal("leader did not exit")
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+	if err := TerminateCommand(cmd); err != nil {
+		t.Fatalf("TerminateCommand: %v", err)
+	}
+
+	// Windows has no persistent group ID analogous to POSIX: once the leader is
+	// gone, taskkill /T cannot rediscover this descendant. Assert that platform
+	// distinction rather than claiming TerminateCommand can provide it here.
+	if !processExistsOnWindows(descendantPID) {
+		t.Fatal("descendant unexpectedly stopped after its root exited")
+	}
+}
+
+func processExistsOnWindows(pid int) bool {
+	return exec.Command("powershell.exe", "-NoProfile", "-NonInteractive", "-Command",
+		"Get-Process -Id "+strconv.Itoa(pid)+" -ErrorAction Stop | Out-Null").Run() == nil
+}

internal/background/terminate.go

@@ -1,5 +1,14 @@
 package background
 
+import (
+	"errors"
+	"fmt"
+	"os/exec"
+	"time"
+)
+
+const commandReapTimeout = 3 * time.Second
+
 // TerminateProcess stops a background process by PID — on Windows its process
 // tree; on POSIX its whole process group when the PID leads its own group (the
 // invariant ConfigureChildProcessGroup establishes for processes started through
@@ -12,3 +21,69 @@ package background
 func TerminateProcess(pid int) error {
 	return terminateProcess(pid)
 }
+
+// TerminateCommand stops a started command and reaps its leader. The caller must
+// have exclusive ownership of cmd: it must not have previously called Wait or
+// Process.Release, and no goroutine may call either concurrently. On POSIX it
+// stops the whole group when the command was configured as its leader; ordinary
+// commands safely fall back to PID/tree discovery. On Windows, success for a
+// leader that was already dead confirms only that the leader was reaped;
+// descendants may survive because Windows cannot rediscover a tree from a dead
+// root. `zero daemon start` needs this operation when readiness times out: it
+// launched the child, so it must both stop the tree and collect the leader.
+//
+// The order matters: the tree is signalled first, because Wait releases the
+// leader's PID and a later group lookup could then resolve to nothing (or, worse,
+// to a recycled PID). Termination stays in the shared execution lifecycle
+// primitives rather than introducing a second platform-specific killer.
+//
+// If the bounded reap times out, the Wait call already started by this function
+// continues in its goroutine. From that point onward the caller must not access
+// cmd at all, including ProcessState, because that would race with Wait.
+func TerminateCommand(cmd *exec.Cmd) error {
+	if cmd == nil || cmd.Process == nil {
+		return errors.New("terminate command: process was never started")
+	}
+	leaderAlreadyExited, terminateErr := terminateOwnedProcess(cmd)
+	reapErr := waitForTerminatedCommandWithin(cmd, commandReapTimeout)
+	if reapErr != nil {
+		if terminateErr != nil {
+			return fmt.Errorf("%v (reap failed: %w)", terminateErr, reapErr)
+		}
+		return reapErr
+	}
+	if terminateErr != nil && !leaderAlreadyExited {
+		return terminateErr
+	}
+	// Only discard a termination error when the platform demonstrated before
+	// attempting termination that the leader had already exited. A successful
+	// reap alone says nothing about whether a live descendant tree was stopped.
+	return nil
+}
+
+// classifyWaitError treats a non-zero exit status as success: a process being
+// terminated is expected to report one (or a signal), so the only interesting
+// failure is Wait itself not working.
+func classifyWaitError(waitErr error) error {
+	var exitErr *exec.ExitError
+	if waitErr != nil && !errors.As(waitErr, &exitErr) {
+		return fmt.Errorf("reap process: %w", waitErr)
+	}
+	return nil
+}
+
+// waitForTerminatedCommandWithin bounds the reap so a child that somehow survives
+// termination cannot hang the caller — the daemon-start cleanup path runs while a
+// user waits at the CLI. On timeout its Wait goroutine is intentionally left to
+// finish: exec.Cmd permits only one Wait call, and abandoning it without a reaper
+// would leak the child once it eventually exits.
+func waitForTerminatedCommandWithin(cmd *exec.Cmd, timeout time.Duration) error {
+	waitDone := make(chan error, 1)
+	go func() { waitDone <- cmd.Wait() }()
+	select {
+	case waitErr := <-waitDone:
+		return classifyWaitError(waitErr)
+	case <-time.After(timeout):
+		return fmt.Errorf("process %d did not reap after termination", cmd.Process.Pid)
+	}
+}

internal/cli/app.go

@@ -64,38 +64,53 @@ type appDeps struct {
 	// getenv reads a process environment variable (production: os.Getenv, set in
 	// defaultAppDeps — deliberately NOT filled by fillAppDeps, so tests are hermetic
 	// against ambient vars like ZERO_PROVIDER unless they inject it). nil ⇒ empty.
-	getenv                 func(string) string
-	probeProviderHealth    func(context.Context, providerhealth.Options) providerhealth.Result
-	discoverProviderModels func(context.Context, config.ProviderProfile) ([]providermodeldiscovery.Model, error)
-	detectLocalRuntimes    func(context.Context, provideronboarding.LocalDetectOptions) []provideronboarding.DetectedLocalRuntime
-	openRouterLogin        func(context.Context, provideroauth.OpenRouterOptions) (string, error)
-	newSessionStore        func() *sessions.Store
-	loadPlugins            func(plugins.LoadOptions) (plugins.LoadResult, error)
-	loadHooks              func(hooks.LoadOptions) (hooks.LoadResult, error)
-	skillsDir              func() string
-	pluginsDir             func() string
-	toolsDir               func() string
-	newMCPStore            func() (*mcp.PermissionStore, error)
-	newMCPTokenStore       func() (*mcp.TokenStore, error)
-	newSandboxStore        func() (*sandbox.GrantStore, error)
-	selectSandboxBackend   func(sandbox.BackendOptions) sandbox.Backend
-	runSandboxSetupHelper  func(path string, args []string, stdout io.Writer, stderr io.Writer) error
-	registerMCPTools       func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error)
-	prepareWorktree        func(context.Context, worktrees.Options) (worktrees.Result, error)
-	releaseWorktree        func(context.Context, worktrees.Options, string) error
-	detectVerifyPlan       func(string) (verify.Plan, error)
-	runVerify              func(context.Context, verify.Plan, verify.RunOptions) verify.Report
-	runSelfVerify          func(context.Context, verify.Plan, selfverify.Options) selfverify.Report
-	runAgentEval           func(context.Context, agentEvalOptions) (agentEvalReport, error)
-	inspectChanges         func(context.Context, zerogit.InspectOptions) (zerogit.ChangeSummary, error)
-	commitChanges          func(context.Context, zerogit.CommitOptions) (zerogit.CommitResult, error)
-	pushChanges            func(context.Context, zerogit.PushOptions) (zerogit.PushResult, error)
-	createPR               func(context.Context, zerogit.PROptions) (zerogit.PRResult, error)
-	runTUI                 func(context.Context, tui.Options) int
-	runEditor              func(string) error
-	checkUpdate            func(context.Context, update.Options) (update.Result, error)
-	applyUpdate            func(context.Context, update.Options) (update.ApplyResult, error)
-	now                    func() time.Time
+	getenv                       func(string) string
+	probeProviderHealth          func(context.Context, providerhealth.Options) providerhealth.Result
+	discoverProviderModels       func(context.Context, config.ProviderProfile) ([]providermodeldiscovery.Model, error)
+	detectLocalRuntimes          func(context.Context, provideronboarding.LocalDetectOptions) []provideronboarding.DetectedLocalRuntime
+	openRouterLogin              func(context.Context, provideroauth.OpenRouterOptions) (string, error)
+	newSessionStore              func() *sessions.Store
+	loadPlugins                  func(plugins.LoadOptions) (plugins.LoadResult, error)
+	loadHooks                    func(hooks.LoadOptions) (hooks.LoadResult, error)
+	skillsDir                    func() string
+	pluginsDir                   func() string
+	toolsDir                     func() string
+	newMCPStore                  func() (*mcp.PermissionStore, error)
+	newMCPTokenStore             func() (*mcp.TokenStore, error)
+	newSandboxStore              func() (*sandbox.GrantStore, error)
+	selectSandboxBackend         func(sandbox.BackendOptions) sandbox.Backend
+	runSandboxSetupHelper        func(path string, args []string, stdout io.Writer, stderr io.Writer) error
+	registerMCPTools             func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error)
+	prepareWorktree              func(context.Context, worktrees.Options) (worktrees.Result, error)
+	releaseWorktree              func(context.Context, worktrees.Options, string) error
+	detectVerifyPlan             func(string) (verify.Plan, error)
+	runVerify                    func(context.Context, verify.Plan, verify.RunOptions) verify.Report
+	runSelfVerify                func(context.Context, verify.Plan, selfverify.Options) selfverify.Report
+	runAgentEval                 func(context.Context, agentEvalOptions) (agentEvalReport, error)
+	inspectChanges               func(context.Context, zerogit.InspectOptions) (zerogit.ChangeSummary, error)
+	commitChanges                func(context.Context, zerogit.CommitOptions) (zerogit.CommitResult, error)
+	pushChanges                  func(context.Context, zerogit.PushOptions) (zerogit.PushResult, error)
+	createPR                     func(context.Context, zerogit.PROptions) (zerogit.PRResult, error)
+	createBranch                 func(context.Context, zerogit.BranchOptions) (zerogit.BranchResult, error)
+	isDefaultBranch              func(context.Context, zerogit.DefaultBranchOptions) (bool, string, string, error)
+	currentGitUser               func(context.Context, string) string
+	headCommitSubject            func(context.Context, string) string
+	commitsAhead                 func(context.Context, string, string, string) (int, error)
+	isUnbornRemote               func(context.Context, string, string) (bool, error)
+	refreshTrackingRef           func(context.Context, string, string, string) error
+	branchUpstreamRemote         func(context.Context, string, string) string
+	branchUpstreamRemoteAndMerge func(context.Context, string, string) (string, string)
+	resolveRemoteBranchTip       func(context.Context, string, string, string) (string, error)
+	remoteHasBranch              func(context.Context, string, string, string) (bool, error)
+	currentGitBranch             func(context.Context, string) string
+	currentBranchTip             func(context.Context, string) string
+	deleteBranch                 func(context.Context, string, string, string) error
+	resetBranchRef               func(context.Context, string, string, string, string) error
+	runTUI                       func(context.Context, tui.Options) int
+	runEditor                    func(string) error
+	checkUpdate                  func(context.Context, update.Options) (update.Result, error)
+	applyUpdate                  func(context.Context, update.Options) (update.ApplyResult, error)
+	now                          func() time.Time
 }
 
 type mcpToolRuntime interface {
@@ -198,11 +213,52 @@ func defaultAppDeps() appDeps {
 		commitChanges:    zerogit.Commit,
 		pushChanges:      zerogit.Push,
 		createPR:         zerogit.CreatePR,
-		runTUI:           tui.Run,
-		runEditor:        openEditor,
-		checkUpdate:      update.Check,
-		applyUpdate:      update.Apply,
-		now:              time.Now,
+		createBranch:     zerogit.CreateBranch,
+		isDefaultBranch:  zerogit.IsDefaultBranch,
+		currentGitUser: func(ctx context.Context, cwd string) string {
+			return zerogit.CurrentGitUser(ctx, cwd, nil)
+		},
+		headCommitSubject: func(ctx context.Context, cwd string) string {
+			return zerogit.HeadCommitSubject(ctx, cwd, nil)
+		},
+		commitsAhead: func(ctx context.Context, cwd, remote, branch string) (int, error) {
+			return zerogit.CommitsAhead(ctx, cwd, remote, branch, nil)
+		},
+		isUnbornRemote: func(ctx context.Context, cwd, remote string) (bool, error) {
+			return zerogit.IsUnbornRemote(ctx, cwd, remote, nil)
+		},
+		refreshTrackingRef: func(ctx context.Context, cwd, remote, branch string) error {
+			return zerogit.RefreshTrackingRef(ctx, cwd, remote, branch, nil)
+		},
+		branchUpstreamRemote: func(ctx context.Context, cwd, branch string) string {
+			return zerogit.UpstreamRemote(ctx, cwd, branch, nil)
+		},
+		branchUpstreamRemoteAndMerge: func(ctx context.Context, cwd, branch string) (string, string) {
+			return zerogit.UpstreamRemoteAndMergeBranch(ctx, cwd, branch, nil)
+		},
+		resolveRemoteBranchTip: func(ctx context.Context, cwd, remote, branch string) (string, error) {
+			return zerogit.ResolveRemoteBranchTip(ctx, cwd, remote, branch, nil)
+		},
+		remoteHasBranch: func(ctx context.Context, cwd, remote, branch string) (bool, error) {
+			return zerogit.RemoteHasBranch(ctx, cwd, remote, branch, nil)
+		},
+		currentGitBranch: func(ctx context.Context, cwd string) string {
+			return zerogit.CurrentBranch(ctx, cwd, nil)
+		},
+		currentBranchTip: func(ctx context.Context, cwd string) string {
+			return zerogit.CurrentBranchTip(ctx, cwd, nil)
+		},
+		deleteBranch: func(ctx context.Context, cwd, fallbackBranch, branchToDelete string) error {
+			return zerogit.DeleteBranch(ctx, cwd, fallbackBranch, branchToDelete, nil)
+		},
+		resetBranchRef: func(ctx context.Context, cwd, branch, newTip, expectedOld string) error {
+			return zerogit.ResetBranchRef(ctx, cwd, branch, newTip, nil, expectedOld)
+		},
+		runTUI:      tui.Run,
+		runEditor:   openEditor,
+		checkUpdate: update.Check,
+		applyUpdate: update.Apply,
+		now:         time.Now,
 	}
 }
 
@@ -562,6 +618,45 @@ func fillAppDeps(deps appDeps) appDeps {
 	if deps.createPR == nil {
 		deps.createPR = defaults.createPR
 	}
+	if deps.createBranch == nil {
+		deps.createBranch = defaults.createBranch
+	}
+	if deps.isDefaultBranch == nil {
+		deps.isDefaultBranch = defaults.isDefaultBranch
+	}
+	if deps.currentGitUser == nil {
+		deps.currentGitUser = defaults.currentGitUser
+	}
+	if deps.headCommitSubject == nil {
+		deps.headCommitSubject = defaults.headCommitSubject
+	}
+	if deps.commitsAhead == nil {
+		deps.commitsAhead = defaults.commitsAhead
+	}
+	if deps.isUnbornRemote == nil {
+		deps.isUnbornRemote = defaults.isUnbornRemote
+	}
+	if deps.refreshTrackingRef == nil {
+		deps.refreshTrackingRef = defaults.refreshTrackingRef
+	}
+	if deps.branchUpstreamRemote == nil {
+		deps.branchUpstreamRemote = defaults.branchUpstreamRemote
+	}
+	if deps.branchUpstreamRemoteAndMerge == nil {
+		deps.branchUpstreamRemoteAndMerge = defaults.branchUpstreamRemoteAndMerge
+	}
+	if deps.remoteHasBranch == nil {
+		deps.remoteHasBranch = defaults.remoteHasBranch
+	}
+	if deps.currentGitBranch == nil {
+		deps.currentGitBranch = defaults.currentGitBranch
+	}
+	if deps.currentBranchTip == nil {
+		deps.currentBranchTip = defaults.currentBranchTip
+	}
+	// resolveRemoteBranchTip, deleteBranch, and resetBranchRef stay nil when
+	// unset so unit tests that mock createBranch without a real git tree do not
+	// hit real git restore/delete commands.
 	if deps.runTUI == nil {
 		deps.runTUI = defaults.runTUI
 	}
@@ -744,24 +839,26 @@ func runInteractiveTUIWithSetup(stderr io.Writer, deps appDeps, permissionMode a
 		mcpTokenStore = nil
 		err = nil
 	}
+	criticalMCPConfig, optionalMCPConfig := splitMCPStartupConfig(mcpConfig)
 	mcpRuntime := mcpToolRuntime(noopMCPRuntime{})
-	if len(mcpConfig.Servers) > 0 {
-		mcpRuntime, err = deps.registerMCPTools(context.Background(), registry, mcpConfig, mcp.RegisterOptions{
+	if len(criticalMCPConfig.Servers) > 0 {
+		runtime, registerErr := deps.registerMCPTools(context.Background(), registry, criticalMCPConfig, mcp.RegisterOptions{
 			PermissionStore: mcpPermissionStore,
 			Autonomy:        mcp.AutonomyLow,
 			Execution:       executionRunner,
 			WorkspaceRoot:   workspaceRoot,
 		})
-	}
-	if err != nil {
-		closeMCPRuntime(stderr, mcpRuntime)
-		return writeAppError(stderr, err.Error(), 1)
+		if registerErr != nil {
+			closeMCPRuntime(stderr, runtime)
+			return writeAppError(stderr, redaction.ErrorMessage(registerErr, redaction.Options{}), 1)
+		}
+		mcpRuntime = runtime
 	}
 	defer closeMCPRuntime(stderr, mcpRuntime)
 	// A server that could not be reached or validated is skipped, not fatal (one
 	// bad MCP server must not abort startup) — surface each so a missing tool set is
 	// explained rather than silently absent. A built-in default the user never
-	// configured (e.g. keyless Firecrawl with no credentials) is the exception: it
+	// configured (e.g. keyless Exa with no credentials) is the exception: it
 	// was never asked for, so its failure is not worth a startup warning — only
 	// servers the user actually configured warn on failure (issue #552).
 	for _, skipped := range mcpRuntime.Skipped() {
@@ -814,11 +911,35 @@ func runInteractiveTUIWithSetup(stderr io.Writer, deps appDeps, permissionMode a
 	}
 	// Activate deferred MCP-tool loading for the interactive run only when the
 	// VISIBLE deferred-eligible count meets the resolved threshold, matching exec.
-	// The registry is complete (core + specialist + MCP + plugins) here, so the
-	// count is accurate; below threshold this is a no-op and the surface is
-	// unchanged. The interactive surface applies no operator tool filters, so
-	// enabled/disabled are nil — matching the AgentOptions below.
+	// This first pass covers every prompt-critical tool. Optional built-in MCP
+	// defaults re-run the same gate after publishing their atomic batch, so a
+	// later catalog generation cannot miss its loader. The interactive surface
+	// applies no operator tool filters, so enabled/disabled are nil — matching the
+	// AgentOptions below.
 	registerToolSearchIfEligible(registry, resolved.Tools.DeferThreshold, permissionMode, nil, nil)
+	var optionalMCPRuntime *optionalMCPStartup
+	var awaitToolReadiness func(context.Context)
+	if len(optionalMCPConfig.Servers) > 0 {
+		optionalMCPRuntime = startOptionalMCP(
+			context.Background(),
+			registry,
+			optionalMCPConfig,
+			mcp.RegisterOptions{
+				PermissionStore: mcpPermissionStore,
+				Autonomy:        mcp.AutonomyLow,
+				Execution:       executionRunner,
+				WorkspaceRoot:   workspaceRoot,
+			},
+			deps.registerMCPTools,
+			func() {
+				registerToolSearchIfEligible(registry, resolved.Tools.DeferThreshold, permissionMode, nil, nil)
+			},
+		)
+		defer closeMCPRuntime(stderr, optionalMCPRuntime)
+		awaitToolReadiness = func(ctx context.Context) {
+			optionalMCPRuntime.Await(ctx, optionalMCPPromptGrace)
+		}
+	}
 	lastKnownMCPConfig := mcpConfig
 	fileTracker := tools.NewFileTracker()
 	var scratchBaseline scratchFileBaseline
@@ -855,8 +976,17 @@ func runInteractiveTUIWithSetup(stderr io.Writer, deps appDeps, permissionMode a
 		RecapsEnabled:        resolved.Preferences.RecapsEnabled(),
 		Provider:             provider,
 		NewProvider:          deps.newProvider,
-		ProbeProviderHealth:  deps.probeProviderHealth,
-		UserAgent:            userAgent(),
+		NewTurnSessionProvider: func(profile config.ProviderProfile, provider zeroruntime.Provider) zeroruntime.TurnSessionProvider {
+			if provider == nil {
+				return nil
+			}
+			if optimized, ok := providers.OptimizedTurnSessions(profile, provider, providers.Options{}); ok {
+				return optimized
+			}
+			return providers.DefaultTurnSessions(profile, provider, providers.Options{})
+		},
+		ProbeProviderHealth: deps.probeProviderHealth,
+		UserAgent:           userAgent(),
 		PrepareRunCompletionWarning: func() {
 			scratchBaseline = scratchFileSnapshot(workspaceRoot)
 		},
@@ -864,6 +994,7 @@ func runInteractiveTUIWithSetup(stderr io.Writer, deps appDeps, permissionMode a
 			return scratchFileWarning(workspaceRoot, scratchBaseline)
 		},
 		Registry:           registry,
+		AwaitToolReadiness: awaitToolReadiness,
 		SessionStore:       sessionStore,
 		PeerService:        peerService,
 		SandboxStore:       sandboxStore,

internal/cli/app_test.go

@@ -17,6 +17,7 @@ import (
 	"github.com/Gitlawb/zero/internal/agent"
 	"github.com/Gitlawb/zero/internal/config"
 	"github.com/Gitlawb/zero/internal/mcp"
+	"github.com/Gitlawb/zero/internal/redaction"
 	"github.com/Gitlawb/zero/internal/tools"
 	"github.com/Gitlawb/zero/internal/tui"
 	"github.com/Gitlawb/zero/internal/update"
@@ -211,12 +212,12 @@ func TestTUIStartupSuppressesWarningForUnconfiguredDefaultServer(t *testing.T) {
 		},
 		resolveMCPConfig: func(workspaceRoot string, excludeProject bool) (config.MCPConfig, error) {
 			return config.MCPConfig{Servers: map[string]config.MCPServerConfig{
-				"firecrawl": config.DefaultMCPServers()["firecrawl"],
+				"exa": config.DefaultMCPServers()["exa"],
 			}}, nil
 		},
 		registerMCPTools: func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error) {
 			return fakeMCPRuntimeWithSkips{skipped: []mcp.SkippedServer{
-				{Name: "firecrawl", Err: errors.New("returned HTTP 401"), UnconfiguredDefault: true},
+				{Name: "exa", Err: errors.New("returned HTTP 401"), UnconfiguredDefault: true},
 			}}, nil
 		},
 		runTUI: func(ctx context.Context, options tui.Options) int {
@@ -227,7 +228,7 @@ func TestTUIStartupSuppressesWarningForUnconfiguredDefaultServer(t *testing.T) {
 	if exitCode != 0 {
 		t.Fatalf("exitCode = %d stderr=%s", exitCode, stderr.String())
 	}
-	if strings.Contains(stderr.String(), "firecrawl") {
+	if strings.Contains(stderr.String(), "exa") {
 		t.Fatalf("stderr = %q, want no warning for an unconfigured default server", stderr.String())
 	}
 }
@@ -486,6 +487,74 @@ func TestRunNoArgsLaunchesTUIWithMCPState(t *testing.T) {
 	}
 }
 
+func TestRunNoArgsPaintsBeforeOptionalDefaultMCPIsReady(t *testing.T) {
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+	cwd := t.TempDir()
+	userConfigPath := filepath.Join(t.TempDir(), "zero", "config.json")
+	permissionStore, err := mcp.NewPermissionStore(mcp.StoreOptions{FilePath: filepath.Join(t.TempDir(), "mcp-permissions.json")})
+	if err != nil {
+		t.Fatalf("NewPermissionStore() error = %v", err)
+	}
+	tokenStore, err := mcp.NewTokenStore(mcp.TokenStoreOptions{FilePath: filepath.Join(t.TempDir(), "mcp-oauth.json")})
+	if err != nil {
+		t.Fatalf("NewTokenStore() error = %v", err)
+	}
+	started := make(chan struct{})
+	release := make(chan struct{})
+	configResult := make(chan error, 1)
+
+	exitCode := runWithDeps([]string{}, &stdout, &stderr, appDeps{
+		getwd:          func() (string, error) { return cwd, nil },
+		userConfigPath: func() (string, error) { return userConfigPath, nil },
+		resolveConfig: func(string, config.Overrides) (config.ResolvedConfig, error) {
+			return config.ResolvedConfig{MaxTurns: 8}, nil
+		},
+		resolveMCPConfig: func(string, bool) (config.MCPConfig, error) {
+			return config.MCPConfig{Servers: config.DefaultMCPServers()}, nil
+		},
+		newMCPStore:      func() (*mcp.PermissionStore, error) { return permissionStore, nil },
+		newMCPTokenStore: func() (*mcp.TokenStore, error) { return tokenStore, nil },
+		registerMCPTools: func(_ context.Context, registry *tools.Registry, cfg config.MCPConfig, _ mcp.RegisterOptions) (mcpToolRuntime, error) {
+			var configErr error
+			if _, ok := cfg.Servers["exa"]; !ok || len(cfg.Servers) != 1 {
+				configErr = fmt.Errorf("optional MCP config = %#v, want only exa", cfg.Servers)
+			}
+			configResult <- configErr
+			close(started)
+			<-release
+			registry.Register(cliFakeMCPRegistryTool{})
+			return noopMCPRuntime{}, nil
+		},
+		runTUI: func(ctx context.Context, options tui.Options) int {
+			select {
+			case <-started:
+			case <-time.After(time.Second):
+				t.Fatal("optional MCP initialization did not start")
+			}
+			if options.AwaitToolReadiness == nil {
+				t.Fatal("TUI did not receive optional tool readiness barrier")
+			}
+			if _, ok := options.Registry.Get("mcp_docs_lookup"); ok {
+				t.Fatal("optional MCP tool was published before registration completed")
+			}
+			close(release)
+			options.AwaitToolReadiness(ctx)
+			if _, ok := options.Registry.Get("mcp_docs_lookup"); !ok {
+				t.Fatal("optional MCP tool was not visible after readiness completed")
+			}
+			return 0
+		},
+	})
+
+	if exitCode != 0 {
+		t.Fatalf("exitCode = %d stderr=%s", exitCode, stderr.String())
+	}
+	if configErr := <-configResult; configErr != nil {
+		t.Fatal(configErr)
+	}
+}
+
 func TestTUIMCPCommandUsesLastGoodConfigOnRefreshError(t *testing.T) {
 	var stdout bytes.Buffer
 	var stderr bytes.Buffer
@@ -565,6 +634,7 @@ func TestRunNoArgsClosesPartialMCPRuntimeWhenRegistrationFails(t *testing.T) {
 		t.Fatalf("NewTokenStore() error = %v", err)
 	}
 	runtimeClosed := false
+	secret := "sk-proj-" + strings.Repeat("a", 23) + "0"
 
 	exitCode := runWithDeps([]string{}, &stdout, &stderr, appDeps{
 		getwd: func() (string, error) {
@@ -591,7 +661,7 @@ func TestRunNoArgsClosesPartialMCPRuntimeWhenRegistrationFails(t *testing.T) {
 			return closeFunc(func() error {
 				runtimeClosed = true
 				return nil
-			}), errors.New("register mcp tools failed")
+			}), fmt.Errorf("register mcp tools failed: %s", secret)
 		},
 		runTUI: func(ctx context.Context, options tui.Options) int {
 			t.Fatal("TUI should not launch after MCP registration fails")
@@ -605,6 +675,12 @@ func TestRunNoArgsClosesPartialMCPRuntimeWhenRegistrationFails(t *testing.T) {
 	if !strings.Contains(stderr.String(), "register mcp tools failed") {
 		t.Fatalf("stderr missing registration error: %s", stderr.String())
 	}
+	if strings.Contains(stderr.String(), secret) {
+		t.Fatalf("stderr leaked MCP registration secret: %s", stderr.String())
+	}
+	if !strings.Contains(stderr.String(), redaction.RedactedSecret) {
+		t.Fatalf("stderr missing redaction marker: %s", stderr.String())
+	}
 	if !runtimeClosed {
 		t.Fatal("partial MCP runtime was not closed after registration error")
 	}

internal/cli/daemon.go

@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -160,20 +161,61 @@ func runDaemonStartDetached(paths daemon.Paths, stdout io.Writer, stderr io.Writ
 	cmd.Stdout = logFile
 	cmd.Stderr = logFile
 	background.ConfigureChildProcessGroup(cmd) // own process group: outlives this shell
-	if err := cmd.Start(); err != nil {
+	if err := startAndAwaitDaemonProcess(cmd, func() bool { return daemonReachable(paths) }, 5*time.Second, 25*time.Millisecond); err != nil {
+		if errors.Is(err, errDaemonStartTimeout) {
+			return writeAppError(stderr, err.Error()+"; see "+logPath, exitCrash)
+		}
 		return writeAppError(stderr, err.Error(), exitCrash)
 	}
-	_ = cmd.Process.Release()
+	fmt.Fprintf(stdout, "zero daemon started (socket %s)\n", paths.Socket)
+	return exitSuccess
+}
 
-	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)
+var errDaemonStartTimeout = errors.New("daemon did not come up within timeout")
+
+func startAndAwaitDaemonProcess(cmd *exec.Cmd, reachable func() bool, timeout time.Duration, pollInterval time.Duration) error {
+	if err := cmd.Start(); err != nil {
+		return err
 	}
-	return writeAppError(stderr, "daemon did not come up within timeout; see "+logPath, exitCrash)
+	if waitForDaemonReadiness(reachable, timeout, pollInterval) {
+		if err := cmd.Process.Release(); err != nil {
+			cleanupErr := terminateAndReapDaemonProcess(cmd)
+			if cleanupErr != nil {
+				return fmt.Errorf("release daemon process: %w (cleanup failed: %v)", err, cleanupErr)
+			}
+			return fmt.Errorf("release daemon process: %w", err)
+		}
+		return nil
+	}
+	if err := terminateAndReapDaemonProcess(cmd); err != nil {
+		return fmt.Errorf("%w; cleanup failed: %v", errDaemonStartTimeout, err)
+	}
+	return errDaemonStartTimeout
+}
+
+func waitForDaemonReadiness(reachable func() bool, timeout time.Duration, pollInterval time.Duration) bool {
+	deadline := time.Now().Add(timeout)
+	for {
+		if reachable() {
+			return true
+		}
+		remaining := time.Until(deadline)
+		if remaining <= 0 {
+			break
+		}
+		time.Sleep(min(pollInterval, remaining))
+	}
+	// The loop's last reachable() call already ran immediately before this one
+	// (right after the final Sleep, with the same deadline check separating
+	// them), so this adds no extra waiting time and is not a grace window for a
+	// slow-starting daemon — it only re-checks the same instant in case
+	// reachable() itself is non-deterministic. To tolerate a genuinely slow
+	// start, raise the timeout passed to startAndAwaitDaemonProcess instead.
+	return reachable()
+}
+
+func terminateAndReapDaemonProcess(cmd *exec.Cmd) error {
+	return background.TerminateCommand(cmd)
 }
 
 func runDaemonStop(args []string, stdout io.Writer, stderr io.Writer) int {

internal/cli/daemon_test.go

@@ -2,8 +2,15 @@ package cli
 
 import (
 	"bytes"
+	"errors"
+	"os"
+	"os/exec"
+	"path/filepath"
 	"strings"
 	"testing"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/background"
 )
 
 // isolateDaemonPaths points DefaultPaths at a temp dir so the test never touches
@@ -121,3 +128,84 @@ func TestDaemonSubcommandsRejectExtraArgs(t *testing.T) {
 		}
 	}
 }
+
+func TestWaitForDaemonReadinessChecksTimeoutBoundary(t *testing.T) {
+	checks := 0
+	ready := waitForDaemonReadiness(func() bool {
+		checks++
+		return checks == 2
+	}, 0, time.Millisecond)
+	if !ready {
+		t.Fatal("daemon that became reachable at the timeout boundary was not detected")
+	}
+	if checks != 2 {
+		t.Fatalf("reachability checks = %d, want initial and final checks", checks)
+	}
+}
+
+func TestTerminateAndReapDaemonProcess(t *testing.T) {
+	cmd := daemonDetachedChildCommand("hang")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start helper process: %v", err)
+	}
+
+	if err := terminateAndReapDaemonProcess(cmd); err != nil {
+		t.Fatalf("terminate and reap helper process: %v", err)
+	}
+	if cmd.ProcessState == nil {
+		t.Fatalf("helper process was not reaped: state=%v", cmd.ProcessState)
+	}
+	if cmd.ProcessState.Success() {
+		t.Fatalf("helper process unexpectedly exited successfully: %v", cmd.ProcessState)
+	}
+}
+
+func TestStartAndAwaitDaemonProcessTimeoutTerminatesAndReaps(t *testing.T) {
+	cmd := daemonDetachedChildCommand("hang")
+	if err := startAndAwaitDaemonProcess(cmd, func() bool { return false }, 0, time.Millisecond); !errors.Is(err, errDaemonStartTimeout) {
+		t.Fatalf("start and await error = %v, want timeout", err)
+	}
+	if cmd.ProcessState == nil {
+		t.Fatal("timed-out helper process was not reaped")
+	}
+}
+
+func TestStartAndAwaitDaemonProcessReleasesReadyChild(t *testing.T) {
+	marker := filepath.Join(t.TempDir(), "child-finished")
+	cmd := daemonDetachedChildCommand("mark", "ZERO_TEST_DAEMON_CHILD_MARKER="+marker)
+	if err := startAndAwaitDaemonProcess(cmd, func() bool { return true }, time.Second, time.Millisecond); err != nil {
+		t.Fatalf("start and await ready helper: %v", err)
+	}
+
+	deadline := time.Now().Add(5 * time.Second)
+	for time.Now().Before(deadline) {
+		if _, err := os.Stat(marker); err == nil {
+			return
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	t.Fatal("released helper process did not remain alive to write its marker")
+}
+
+func daemonDetachedChildCommand(mode string, extraEnv ...string) *exec.Cmd {
+	cmd := exec.Command(os.Args[0], "-test.run=TestDaemonDetachedChildProcess")
+	cmd.Env = append(os.Environ(), "ZERO_TEST_DAEMON_DETACHED_CHILD="+mode)
+	cmd.Env = append(cmd.Env, extraEnv...)
+	background.ConfigureChildProcessGroup(cmd)
+	return cmd
+}
+
+func TestDaemonDetachedChildProcess(t *testing.T) {
+	switch os.Getenv("ZERO_TEST_DAEMON_DETACHED_CHILD") {
+	case "":
+		return
+	case "mark":
+		if err := os.WriteFile(os.Getenv("ZERO_TEST_DAEMON_CHILD_MARKER"), []byte("ready"), 0o600); err != nil {
+			os.Exit(2)
+		}
+		os.Exit(0)
+	}
+	for {
+		time.Sleep(time.Hour)
+	}
+}

internal/cli/exec.go

@@ -939,6 +939,9 @@ func registerToolSearchIfEligible(registry *tools.Registry, deferThreshold int,
 	if deferThreshold <= 0 {
 		return
 	}
+	if _, registered := registry.Get(tools.ToolSearchToolName); registered {
+		return
+	}
 	if deferredEligibleCount(registry, permissionMode, enabledTools, disabledTools) < deferThreshold {
 		return
 	}

internal/cli/exec_writer.go

@@ -267,23 +267,29 @@ func streamJSONPermissionEventType(event agent.PermissionEvent) streamjson.Event
 func (writer *execEventWriter) usage(usage agent.Usage) {
 	if writer.format == execOutputJSON {
 		writer.writeJSON(map[string]any{
-			"type":              "usage",
-			"prompt_tokens":     usage.PromptTokens,
-			"completion_tokens": usage.CompletionTokens,
-			"total_tokens":      usage.TotalTokens(),
+			"type":                "usage",
+			"prompt_tokens":       usage.PromptTokens,
+			"completion_tokens":   usage.CompletionTokens,
+			"cached_input_tokens": usage.CachedInputTokens,
+			"cache_write_tokens":  usage.CacheWriteTokens,
+			"total_tokens":        usage.TotalTokens(),
 		})
 		return
 	}
 	if writer.format == execOutputStreamJSON {
 		promptTokens := usage.EffectiveInputTokens()
 		completionTokens := usage.EffectiveOutputTokens()
+		cachedInputTokens := usage.CachedInputTokens
+		cacheWriteTokens := usage.CacheWriteTokens
 		totalTokens := usage.TotalTokens()
 		writer.writeStreamJSON(streamjson.Event{
-			Type:             streamjson.EventUsage,
-			RunID:            writer.runID,
-			PromptTokens:     &promptTokens,
-			CompletionTokens: &completionTokens,
-			TotalTokens:      &totalTokens,
+			Type:              streamjson.EventUsage,
+			RunID:             writer.runID,
+			PromptTokens:      &promptTokens,
+			CompletionTokens:  &completionTokens,
+			CachedInputTokens: &cachedInputTokens,
+			CacheWriteTokens:  &cacheWriteTokens,
+			TotalTokens:       &totalTokens,
 		})
 	}
 }

internal/cli/exec_writer_test.go

@@ -52,3 +52,39 @@ func TestExecWriterPropagatesToolResultTruncation(t *testing.T) {
 		})
 	}
 }
+
+func TestExecWriterPropagatesCacheUsage(t *testing.T) {
+	for _, format := range []execOutputFormat{execOutputJSON, execOutputStreamJSON} {
+		t.Run(string(format), func(t *testing.T) {
+			var stdout bytes.Buffer
+			writer := execEventWriter{
+				stdout:       &stdout,
+				format:       format,
+				runID:        "run_usage",
+				streamedText: &strings.Builder{},
+			}
+			writer.usage(agent.Usage{
+				InputTokens:       100,
+				OutputTokens:      20,
+				PromptTokens:      100,
+				CompletionTokens:  20,
+				CachedInputTokens: 60,
+				CacheWriteTokens:  10,
+			})
+			if writer.err != nil {
+				t.Fatalf("usage: %v", writer.err)
+			}
+			var payload map[string]any
+			if err := json.Unmarshal(bytes.TrimSpace(stdout.Bytes()), &payload); err != nil {
+				t.Fatalf("decode output %q: %v", stdout.String(), err)
+			}
+			cachedKey, writeKey := "cached_input_tokens", "cache_write_tokens"
+			if format == execOutputStreamJSON {
+				cachedKey, writeKey = "cachedInputTokens", "cacheWriteTokens"
+			}
+			if payload[cachedKey] != float64(60) || payload[writeKey] != float64(10) {
+				t.Fatalf("cache usage missing from payload: %#v", payload)
+			}
+		})
+	}
+}

internal/cli/mcp_default_test.go

@@ -9,15 +9,15 @@ import (
 	"github.com/Gitlawb/zero/internal/config"
 )
 
-// `zero mcp disable firecrawl` must work even though firecrawl is a built-in
+// `zero mcp disable exa` must work even though exa is a built-in
 // default that is not written to the user's config file until overridden.
-func TestRunMCPDisableSeededFirecrawlDefault(t *testing.T) {
+func TestRunMCPDisableSeededExaDefault(t *testing.T) {
 	configPath := filepath.Join(t.TempDir(), "zero", "config.json")
-	// A config with no firecrawl entry — the default lives in code, not the file.
+	// A config with no Exa entry — the default lives in code, not the file.
 	writeMCPCommandRawConfig(t, configPath, `{"activeProvider":"fast"}`)
 
 	var out, errBuf bytes.Buffer
-	code := runWithDeps([]string{"mcp", "disable", "firecrawl", "--json"}, &out, &errBuf, appDeps{
+	code := runWithDeps([]string{"mcp", "disable", "exa", "--json"}, &out, &errBuf, appDeps{
 		userConfigPath: func() (string, error) { return configPath, nil },
 	})
 	if code != exitSuccess {
@@ -31,8 +31,8 @@ func TestRunMCPDisableSeededFirecrawlDefault(t *testing.T) {
 	if err := json.Unmarshal(out.Bytes(), &payload); err != nil {
 		t.Fatalf("decode disable JSON: %v\n%s", err, out.String())
 	}
-	if payload.ServerName != "firecrawl" || !payload.Disabled || !payload.Changed {
-		t.Fatalf("disable payload = %#v, want firecrawl disabled+changed", payload)
+	if payload.ServerName != "exa" || !payload.Disabled || !payload.Changed {
+		t.Fatalf("disable payload = %#v, want exa disabled+changed", payload)
 	}
 
 	// End-to-end: resolving that config now turns the default off.
@@ -40,7 +40,7 @@ func TestRunMCPDisableSeededFirecrawlDefault(t *testing.T) {
 	if err != nil {
 		t.Fatalf("ResolveMCP: %v", err)
 	}
-	if !cfg.Servers["firecrawl"].Disabled {
-		t.Fatal("expected `mcp disable firecrawl` to turn the seeded default off in the resolved config")
+	if !cfg.Servers["exa"].Disabled {
+		t.Fatal("expected `mcp disable exa` to turn the seeded default off in the resolved config")
 	}
 }

internal/cli/mcp_startup.go

@@ -0,0 +1,147 @@
+package cli
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/config"
+	"github.com/Gitlawb/zero/internal/mcp"
+	"github.com/Gitlawb/zero/internal/tools"
+)
+
+const (
+	optionalMCPPromptGrace = time.Second
+	optionalMCPCloseGrace  = 250 * time.Millisecond
+)
+
+// splitMCPStartupConfig keeps explicitly configured servers on the
+// prompt-critical path. Only unchanged built-in defaults may initialize after
+// first paint; their failure was already intentionally silent.
+func splitMCPStartupConfig(cfg config.MCPConfig) (critical config.MCPConfig, optional config.MCPConfig) {
+	critical.Servers = map[string]config.MCPServerConfig{}
+	optional.Servers = map[string]config.MCPServerConfig{}
+	for name, server := range cfg.Servers {
+		if server.Disabled {
+			continue
+		}
+		if config.IsUnconfiguredDefault(name, server) {
+			optional.Servers[name] = server
+			continue
+		}
+		critical.Servers[name] = server
+	}
+	return critical, optional
+}
+
+type optionalMCPStartup struct {
+	cancel context.CancelFunc
+	done   chan struct{}
+
+	mu      sync.Mutex
+	runtime mcpToolRuntime
+
+	closeOnce        sync.Once
+	runtimeCloseOnce sync.Once
+	closeErr         error
+}
+
+func startOptionalMCP(
+	parent context.Context,
+	registry *tools.Registry,
+	cfg config.MCPConfig,
+	options mcp.RegisterOptions,
+	register func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error),
+	onReady func(),
+) *optionalMCPStartup {
+	ctx, cancel := context.WithCancel(parent)
+	startup := &optionalMCPStartup{cancel: cancel, done: make(chan struct{})}
+	go func() {
+		runtime, err := register(ctx, registry, cfg, options)
+		if err == nil && onReady != nil {
+			onReady()
+		}
+		startup.mu.Lock()
+		startup.runtime = runtime
+		startup.mu.Unlock()
+		close(startup.done)
+	}()
+	return startup
+}
+
+// Await gives optional tools one bounded opportunity to join the next turn's
+// immutable registry snapshot. A timeout leaves this turn on the existing core
+// tool set; a later turn observes the completed generation.
+func (startup *optionalMCPStartup) Await(ctx context.Context, timeout time.Duration) bool {
+	if startup == nil {
+		return true
+	}
+	select {
+	case <-startup.done:
+		return true
+	default:
+	}
+	if timeout <= 0 {
+		select {
+		case <-startup.done:
+			return true
+		case <-ctx.Done():
+			return false
+		}
+	}
+	timer := time.NewTimer(timeout)
+	defer timer.Stop()
+	select {
+	case <-startup.done:
+		return true
+	case <-timer.C:
+		return false
+	case <-ctx.Done():
+		return false
+	}
+}
+
+func (startup *optionalMCPStartup) Close() error {
+	if startup == nil {
+		return nil
+	}
+	startup.closeOnce.Do(func() {
+		startup.cancel()
+		reaped := make(chan struct{})
+		go func() {
+			defer close(reaped)
+			<-startup.done
+			startup.closeRuntime()
+		}()
+		timer := time.NewTimer(optionalMCPCloseGrace)
+		defer timer.Stop()
+		select {
+		case <-reaped:
+		case <-timer.C:
+		}
+	})
+	startup.mu.Lock()
+	defer startup.mu.Unlock()
+	return startup.closeErr
+}
+
+func (startup *optionalMCPStartup) closeRuntime() {
+	startup.runtimeCloseOnce.Do(func() {
+		startup.mu.Lock()
+		runtime := startup.runtime
+		startup.mu.Unlock()
+		if runtime == nil {
+			return
+		}
+		err := runtime.Close()
+		startup.mu.Lock()
+		if err != nil && startup.closeErr == nil {
+			startup.closeErr = err
+		}
+		startup.mu.Unlock()
+	})
+}
+
+func (startup *optionalMCPStartup) Skipped() []mcp.SkippedServer {
+	return nil
+}

internal/cli/mcp_startup_test.go

@@ -0,0 +1,187 @@
+package cli
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/Gitlawb/zero/internal/config"
+	"github.com/Gitlawb/zero/internal/mcp"
+	"github.com/Gitlawb/zero/internal/tools"
+)
+
+type closeTrackingMCPRuntime struct {
+	closed chan struct{}
+	err    error
+}
+
+func (runtime *closeTrackingMCPRuntime) Close() error {
+	close(runtime.closed)
+	return runtime.err
+}
+
+func (*closeTrackingMCPRuntime) Skipped() []mcp.SkippedServer { return nil }
+
+func TestSplitMCPStartupConfigDefersOnlyUnconfiguredDefaults(t *testing.T) {
+	defaults := config.DefaultMCPServers()
+	cfg := config.MCPConfig{Servers: map[string]config.MCPServerConfig{
+		"exa":      defaults["exa"],
+		"docs":     {Type: "http", URL: "https://docs.example.test/mcp"},
+		"disabled": {Type: "http", URL: "https://disabled.example.test/mcp", Disabled: true},
+	}}
+
+	critical, optional := splitMCPStartupConfig(cfg)
+	if _, ok := critical.Servers["docs"]; !ok || len(critical.Servers) != 1 {
+		t.Fatalf("critical servers = %#v, want only docs", critical.Servers)
+	}
+	if _, ok := optional.Servers["exa"]; !ok || len(optional.Servers) != 1 {
+		t.Fatalf("optional servers = %#v, want only exa", optional.Servers)
+	}
+}
+
+func TestOptionalMCPAwaitTimesOutThenObservesPublishedTools(t *testing.T) {
+	registry := tools.NewRegistry()
+	release := make(chan struct{})
+	started := make(chan struct{})
+	startup := startOptionalMCP(
+		context.Background(),
+		registry,
+		config.MCPConfig{Servers: config.DefaultMCPServers()},
+		mcp.RegisterOptions{},
+		func(ctx context.Context, registry *tools.Registry, _ config.MCPConfig, _ mcp.RegisterOptions) (mcpToolRuntime, error) {
+			close(started)
+			select {
+			case <-release:
+				registry.RegisterBatch([]tools.Tool{tools.NewScopedReadFileTool(t.TempDir(), nil)})
+				return noopMCPRuntime{}, nil
+			case <-ctx.Done():
+				return noopMCPRuntime{}, ctx.Err()
+			}
+		},
+		nil,
+	)
+	defer func() { _ = startup.Close() }()
+	<-started
+
+	if startup.Await(t.Context(), time.Millisecond) {
+		t.Fatal("optional startup unexpectedly completed before release")
+	}
+	if got := len(registry.All()); got != 0 {
+		t.Fatalf("registry published tools before readiness: %d", got)
+	}
+	close(release)
+	if !startup.Await(t.Context(), time.Second) {
+		t.Fatal("optional startup did not complete after release")
+	}
+	if _, ok := registry.Get("read_file"); !ok {
+		t.Fatal("completed optional startup did not publish its tool batch")
+	}
+}
+
+func TestOptionalMCPFailedRegistrationSkipsReadinessCallback(t *testing.T) {
+	readyCalls := 0
+	startup := startOptionalMCP(
+		context.Background(),
+		tools.NewRegistry(),
+		config.MCPConfig{Servers: config.DefaultMCPServers()},
+		mcp.RegisterOptions{},
+		func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error) {
+			return noopMCPRuntime{}, errors.New("connect failed")
+		},
+		func() { readyCalls++ },
+	)
+	defer func() { _ = startup.Close() }()
+
+	if !startup.Await(t.Context(), time.Second) {
+		t.Fatal("failed optional startup did not settle")
+	}
+	if readyCalls != 0 {
+		t.Fatalf("readiness callback ran after failed registration: %d", readyCalls)
+	}
+}
+
+func TestOptionalMCPCloseCancelsBlockedStartup(t *testing.T) {
+	started := make(chan struct{})
+	startup := startOptionalMCP(
+		context.Background(),
+		tools.NewRegistry(),
+		config.MCPConfig{Servers: config.DefaultMCPServers()},
+		mcp.RegisterOptions{},
+		func(ctx context.Context, _ *tools.Registry, _ config.MCPConfig, _ mcp.RegisterOptions) (mcpToolRuntime, error) {
+			close(started)
+			<-ctx.Done()
+			return noopMCPRuntime{}, nil
+		},
+		nil,
+	)
+	<-started
+	if err := startup.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+}
+
+func TestOptionalMCPCloseReturnsRuntimeErrorWithinGrace(t *testing.T) {
+	closeErr := errors.New("close failed")
+	runtime := &closeTrackingMCPRuntime{closed: make(chan struct{}), err: closeErr}
+	startup := startOptionalMCP(
+		context.Background(),
+		tools.NewRegistry(),
+		config.MCPConfig{Servers: config.DefaultMCPServers()},
+		mcp.RegisterOptions{},
+		func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error) {
+			return runtime, nil
+		},
+		nil,
+	)
+	if !startup.Await(t.Context(), time.Second) {
+		t.Fatal("optional startup did not settle")
+	}
+	if err := startup.Close(); !errors.Is(err, closeErr) {
+		t.Fatalf("Close() error = %v, want %v", err, closeErr)
+	}
+}
+
+func TestOptionalMCPCloseBoundsRegistrationThatIgnoresCancellation(t *testing.T) {
+	started := make(chan struct{})
+	release := make(chan struct{})
+	released := false
+	defer func() {
+		if !released {
+			close(release)
+		}
+	}()
+	runtime := &closeTrackingMCPRuntime{closed: make(chan struct{})}
+	startup := startOptionalMCP(
+		context.Background(),
+		tools.NewRegistry(),
+		config.MCPConfig{Servers: config.DefaultMCPServers()},
+		mcp.RegisterOptions{},
+		func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error) {
+			close(started)
+			<-release
+			return runtime, nil
+		},
+		nil,
+	)
+	<-started
+
+	closeResult := make(chan error, 1)
+	go func() { closeResult <- startup.Close() }()
+	select {
+	case err := <-closeResult:
+		if err != nil {
+			t.Fatalf("Close() error = %v", err)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("Close blocked on registration after cancellation")
+	}
+
+	close(release)
+	released = true
+	select {
+	case <-runtime.closed:
+	case <-time.After(time.Second):
+		t.Fatal("late optional MCP runtime was not closed")
+	}
+}

internal/cli/workflows.go

@@ -2,9 +2,12 @@ package cli
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
+	"path"
 	"path/filepath"
+	"regexp"
 	"strconv"
 	"strings"
 	"time"
@@ -602,18 +605,20 @@ func parseChangesArgs(args []string, command string) (changesCommandOptions, boo
 			return options, false, execUsageError{fmt.Sprintf("unexpected changes argument %q", arg)}
 		}
 	}
-	if command != "commit" && options.message != "" {
+	if command != "commit" && options.hasMessage {
 		return options, false, execUsageError{"--message is only valid with `zero changes commit`"}
 	}
-	if command != "commit" && (options.hasMessage || options.dryRun || options.auto) {
-		return options, false, execUsageError{"--message, --dry-run, and --auto are only valid with `zero changes commit`"}
-	}
 	if command == "commit" && options.hasMessage && options.auto {
 		return options, false, execUsageError{"cannot specify both --message and --auto"}
 	}
 	if command != "commit" && command != "push" && options.dryRun {
 		return options, false, execUsageError{"--dry-run is only valid with commit or push"}
 	}
+	// --auto on push/pr is the explicit opt-in for LLM branch naming (see
+	// ensureFeatureBranch); on commit it opts into the LLM commit message.
+	if command != "commit" && command != "push" && command != "pr" && options.auto {
+		return options, false, execUsageError{"--auto is only valid with commit, push, or pr"}
+	}
 	if command != "inspect" && options.baseRef != "" {
 		return options, false, execUsageError{"--base is only valid with `zero changes inspect`"}
 	}
@@ -934,8 +939,7 @@ Flags:
       --fill              Automatically populate PR title and body from commits
       --draft             Create PR as a draft
       --yes               Confirm pushing to a default/protected branch
-  -a, --auto              Auto-generate commit message using LLM (use --dry-run to preview)
-      --dry-run           Preview commit metadata without mutating git state
+  -a, --auto              Use the LLM: commit generates the message, push/pr name the auto-created branch (sends the diff to the provider)
       --json              Print JSON output
   -h, --help              Show this help
 `)
@@ -958,11 +962,31 @@ func runChangesPush(args []string, stdout io.Writer, stderr io.Writer, deps appD
 		return writeExecUsageError(stderr, err.Error())
 	}
 
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	defer cancel()
+
+	branch, remote, created, err := ensureFeatureBranch(ctx, stdout, workspaceRoot, options.remote, featureBranchOptions{
+		JSONMode:           options.json,
+		AllowDefaultBranch: options.yes,
+		DryRun:             options.dryRun,
+		AutoNaming:         options.auto,
+		MaxDiffBytes:       options.maxDiffBytes,
+	}, deps)
+	if err != nil {
+		return writeExecUsageError(stderr, err.Error())
+	}
+
+	// context.Background() is deliberate: the 2-minute ctx above is the
+	// feature-branch preflight (inspection, remote probes, branch creation).
+	// The push itself must not be cancelled mid-transfer just because the
+	// preflight budget elapsed; a large push can legitimately take longer.
 	result, err := deps.pushChanges(context.Background(), zerogit.PushOptions{
 		Cwd:                    workspaceRoot,
-		Remote:                 options.remote,
+		Remote:                 firstNonEmptyString(options.remote, remote),
+		Branch:                 branch,
 		Force:                  options.force,
 		DryRun:                 options.dryRun,
+		RequireNewRemoteBranch: created,
 		AllowPushDefaultBranch: options.yes,
 	})
 	if err != nil {
@@ -1010,15 +1034,62 @@ func runChangesPR(args []string, stdout io.Writer, stderr io.Writer, deps appDep
 		return writeExecUsageError(stderr, err.Error())
 	}
 
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	defer cancel()
+
+	branch, remote, created, err := ensureFeatureBranch(ctx, stdout, workspaceRoot, options.remote, featureBranchOptions{
+		JSONMode:           options.json,
+		AllowDefaultBranch: options.yes,
+		DryRun:             false,
+		AutoNaming:         options.auto,
+		MaxDiffBytes:       options.maxDiffBytes,
+	}, deps)
+	if err != nil {
+		return writeExecUsageError(stderr, err.Error())
+	}
+
+	// Resolve the target remote for the unborn-remote check. Explicit --remote wins,
+	// followed by the remote resolved by ensureFeatureBranch. When --yes is set,
+	// fall back to the branch upstream or "origin".
+	targetRemote := strings.TrimSpace(options.remote)
+	if targetRemote == "" {
+		targetRemote = remote
+	}
+	if targetRemote == "" {
+		currentBranch := ""
+		if deps.currentGitBranch != nil {
+			currentBranch = deps.currentGitBranch(context.Background(), workspaceRoot)
+		}
+		if deps.branchUpstreamRemote != nil && currentBranch != "" {
+			targetRemote = deps.branchUpstreamRemote(context.Background(), workspaceRoot, currentBranch)
+		}
+		if targetRemote == "" {
+			targetRemote = "origin"
+		}
+	}
+
+	// Probe errors are intentionally ignored so the flow can continue; if the
+	// probe fails, the subsequent push or PR operation provides fail-closed behavior.
+	if deps.isUnbornRemote != nil {
+		if unborn, unbornErr := deps.isUnbornRemote(context.Background(), workspaceRoot, targetRemote); unbornErr == nil && unborn {
+			return writeExecUsageError(stderr, fmt.Sprintf("cannot create pull request on unborn remote %s: push the initial default branch first", targetRemote))
+		}
+	}
+
 	if !options.json {
 		if _, err := fmt.Fprintln(stdout, "Pushing current branch to set upstream..."); err != nil {
 			return exitCrash
 		}
 	}
+	// context.Background() is deliberate here too: runChangesPR reuses the
+	// 2-minute ctx for preflight (branch creation and remote probes), but the
+	// push must not be cancelled mid-transfer if that budget elapsed.
 	pushResult, err := deps.pushChanges(context.Background(), zerogit.PushOptions{
 		Cwd:                    workspaceRoot,
-		Remote:                 options.remote,
+		Remote:                 firstNonEmptyString(options.remote, remote),
+		Branch:                 branch,
 		Force:                  options.force,
+		RequireNewRemoteBranch: created,
 		AllowPushDefaultBranch: options.yes,
 	})
 	if err != nil {
@@ -1100,3 +1171,462 @@ func generateAutoCommitMessage(ctx context.Context, provider zeroruntime.Provide
 	}
 	return msg, nil
 }
+
+type featureBranchOptions struct {
+	JSONMode           bool
+	AllowDefaultBranch bool
+	DryRun             bool
+	AutoNaming         bool
+	MaxDiffBytes       int
+}
+
+// branchPushPlan holds the resolved parameters for a push or PR workflow
+// before any branches are created or refs mutated. Separating plan resolution
+// from mutation allows tests to assert the resolution matrix directly without
+// touching a git repository.
+type branchPushPlan struct {
+	ShouldBranch           bool
+	CurrentBranch          string
+	PushRemote             string
+	RequireNewRemoteBranch bool
+	TrackingRemote         string
+	TrackingBranch         string
+	RestoreTip             string
+	PublishabilityBase     string
+	Summary                zerogit.ChangeSummary
+	Slug                   string
+}
+
+// resolveBranchPushPlan resolves the branch, remotes, restore tip, and naming
+// slug for changes push / pr workflows. It performs all checks (clean working
+// tree, unborn remote detection, ahead count, restore tip resolution) but
+// executes no mutation (no branch creation, ref resets, or deletions).
+func resolveBranchPushPlan(ctx context.Context, stdout io.Writer, workspaceRoot string, requestedRemote string, opts featureBranchOptions, deps appDeps) (branchPushPlan, error) {
+	if opts.AllowDefaultBranch || opts.DryRun {
+		return branchPushPlan{
+			ShouldBranch:           false,
+			PushRemote:             strings.TrimSpace(requestedRemote),
+			RequireNewRemoteBranch: false,
+		}, nil
+	}
+
+	if deps.isDefaultBranch == nil {
+		return branchPushPlan{}, fmt.Errorf("isDefaultBranch dependency missing")
+	}
+	isDefault, currentBranch, remote, err := deps.isDefaultBranch(ctx, zerogit.DefaultBranchOptions{Cwd: workspaceRoot, Remote: requestedRemote})
+	if err != nil {
+		return branchPushPlan{}, err
+	}
+	if !isDefault {
+		// Whether this push needs the nonexistence lease is decided by one
+		// live check against the destination remote, not by inference from
+		// local git state (upstream config, a generated-branch marker):
+		// every local signal that stood in for that check turned out to be
+		// wrong in some ordering (inherited config from checkout -b, a
+		// config write that failed after a successful push, a push aimed at
+		// a different remote than the one local config describes). A branch
+		// missing on the remote gets the nonexistence lease, protecting a
+		// concurrent creator of the same name; a branch already there gets a
+		// plain push, and git's own fast-forward check is the safety net —
+		// if the remote history isn't ours, the push fails with a clear
+		// non-fast-forward error instead of an attempted silent recovery.
+		if deps.remoteHasBranch == nil {
+			return branchPushPlan{
+				ShouldBranch:           false,
+				CurrentBranch:          currentBranch,
+				PushRemote:             remote,
+				RequireNewRemoteBranch: true,
+			}, nil
+		}
+		targetRemote := firstNonEmptyString(requestedRemote, remote)
+		exists, existsErr := deps.remoteHasBranch(ctx, workspaceRoot, targetRemote, currentBranch)
+		if existsErr != nil {
+			return branchPushPlan{}, fmt.Errorf("cannot check whether %s already exists on remote %s: %w", currentBranch, targetRemote, existsErr)
+		}
+		return branchPushPlan{
+			ShouldBranch:           false,
+			CurrentBranch:          currentBranch,
+			PushRemote:             remote,
+			RequireNewRemoteBranch: !exists,
+		}, nil
+	}
+
+	// CreateBranch and Push publish commits only. A dirty working tree would
+	// leave uncommitted edits behind under a branch/PR that does not include
+	// them, so refuse until the tree is clean (commit or stash first).
+	workingTree, err := deps.inspectChanges(ctx, zerogit.InspectOptions{Cwd: workspaceRoot})
+	if err != nil {
+		return branchPushPlan{}, fmt.Errorf("failed to inspect working tree: %w", err)
+	}
+	if !workingTree.Clean {
+		return branchPushPlan{}, fmt.Errorf("working tree has uncommitted changes; commit or stash them before pushing from the default branch")
+	}
+
+	// Capture the source default branch's own upstream before refreshing or
+	// leaving it. --remote selects the push destination; restore must not
+	// rewrite local main to upstream/main when main still tracks origin/main
+	// (fork setups), and refreshing must update the exact tracking ref that
+	// will supply both the ahead count and the restore target.
+	trackingRemote := remote
+	trackingBranch := currentBranch
+	if deps.branchUpstreamRemoteAndMerge != nil {
+		if r, m := deps.branchUpstreamRemoteAndMerge(ctx, workspaceRoot, currentBranch); r != "" && m != "" {
+			trackingRemote = r
+			trackingBranch = m
+		}
+	}
+
+	// Refresh the local remote-tracking ref before trusting it: IsDefaultBranch
+	// already contacted the remote for its symref check, but the tracking ref
+	// commitsAhead reads from is only a local cache (written at clone or the
+	// last fetch) and can sit behind the remote's live tip. Left stale, a real
+	// publishable range could look like zero commits ahead, and the diff
+	// derived below (which reuses this same ref as its base) would be stale
+	// too. A failure here (offline, or a genuinely unborn remote with no such
+	// ref to fetch yet) is folded into the same fail-closed path as an
+	// unresolvable ahead count below.
+	var fetchErr error
+	if deps.refreshTrackingRef != nil {
+		fetchErr = deps.refreshTrackingRef(ctx, workspaceRoot, trackingRemote, trackingBranch)
+	}
+
+	// The ahead check gates on the source upstream (trackingRemote), but the
+	// feature branch is pushed to `pushRemote`, which can be a different
+	// destination (--remote on a fork). Refuse to auto-branch onto an unborn
+	// destination: without an initial default branch the new feature branch
+	// becomes the destination's first ref and its HEAD is left pointing at it.
+	// This is checked once, here, against the push destination, before resolving
+	// commit tips or creating any branches.
+	pushRemote := firstNonEmptyString(requestedRemote, remote)
+	if deps.isUnbornRemote != nil {
+		if unbornDest, unbornDestErr := deps.isUnbornRemote(ctx, workspaceRoot, pushRemote); unbornDestErr == nil && unbornDest {
+			return branchPushPlan{}, fmt.Errorf("remote %s has no branches yet; push the initial default branch first with --yes (`zero changes push --yes`), then use auto-branching for subsequent work", pushRemote)
+		}
+	}
+
+	// Branching off the default branch only makes sense when HEAD carries a
+	// commit that is not already on the remote default branch. A clean,
+	// up-to-date default branch would otherwise publish a feature branch at the
+	// exact default tip. If the ahead count cannot be determined (for example
+	// the remote-tracking ref was never fetched), fail rather than guess. When
+	// the remote is confirmed unborn, refuse auto-branching entirely: the
+	// initial default branch must be established first (changes push --yes)
+	// so the remote has a real HEAD before any feature branch is published.
+	ahead, aheadErr := deps.commitsAhead(ctx, workspaceRoot, trackingRemote, trackingBranch)
+	if fetchErr != nil || aheadErr != nil {
+		var unbornRemote bool
+		var unbornErr error
+		if deps.isUnbornRemote != nil {
+			unbornRemote, unbornErr = deps.isUnbornRemote(ctx, workspaceRoot, trackingRemote)
+		}
+		if unbornErr == nil && unbornRemote {
+			return branchPushPlan{}, fmt.Errorf("remote %s has no branches yet; push the initial default branch first with --yes (`zero changes push --yes`), then use auto-branching for subsequent work", trackingRemote)
+		}
+		cause := aheadErr
+		if cause == nil {
+			cause = fetchErr
+		}
+		return branchPushPlan{}, fmt.Errorf("cannot determine whether HEAD is ahead of %s/%s: %w; fetch the remote tracking branch first", trackingRemote, trackingBranch, cause)
+	}
+	if ahead == 0 {
+		return branchPushPlan{}, fmt.Errorf("no changes to publish: HEAD is not ahead of %s/%s; commit your work before pushing", trackingRemote, trackingBranch)
+	}
+
+	// Resolve the restore tip to a concrete commit before creating any branch.
+	// It must never be a bare local branch name: resolving "main" yields the
+	// very commit the feature branch is about to own, so restore becomes a
+	// silent no-op and the publishable commits stay on the default branch. A
+	// named remote resolves through its just-refreshed remote-tracking ref; a
+	// direct URL or path asks the remote itself. Fail closed rather than
+	// substitute a local branch name.
+	restoreTip := ""
+	if deps.resolveRemoteBranchTip != nil {
+		tip, tipErr := deps.resolveRemoteBranchTip(ctx, workspaceRoot, trackingRemote, trackingBranch)
+		if tipErr != nil {
+			return branchPushPlan{}, fmt.Errorf("cannot resolve restore tip for %s/%s: %w", trackingRemote, trackingBranch, tipErr)
+		}
+		restoreTip = tip
+	}
+	if restoreTip == "" {
+		restoreTip = trackingRemote + "/" + trackingBranch
+	}
+
+	// Name the branch (and, with --auto, send the provider) from what HEAD is
+	// actually ahead of the resolved remote branch by, using the same ref
+	// commitsAhead just checked. A working-tree snapshot can describe edits a
+	// commit-only push will never include.
+	baseRef := restoreTip
+	summary, err := deps.inspectChanges(ctx, zerogit.InspectOptions{Cwd: workspaceRoot, BaseRef: baseRef, MaxDiffBytes: opts.MaxDiffBytes})
+	if err != nil {
+		return branchPushPlan{}, fmt.Errorf("failed to inspect changes: %w", err)
+	}
+
+	slug := fallbackBranchSlug(summary)
+	if len(summary.Files) == 0 {
+		// An empty commit (or one whose only content the diff omits) leaves
+		// nothing to derive a slug from; name the branch from the commit
+		// subject instead.
+		if subject := deps.headCommitSubject(ctx, workspaceRoot); subject != "" {
+			slug = zerogit.SlugifyBranchComponent(subject)
+		}
+	}
+	if opts.AutoNaming && strings.TrimSpace(summary.Diff) != "" {
+		llmSlug := ""
+		if resolved, cfgErr := deps.resolveConfig(workspaceRoot, config.Overrides{}); cfgErr == nil && config.HasProviderProfile(resolved.Provider) {
+			if provider, provErr := deps.newProvider(resolved.Provider); provErr == nil {
+				if !opts.JSONMode {
+					fmt.Fprintln(stdout, "Generating branch name using LLM...")
+				}
+				genCtx, cancel := context.WithTimeout(ctx, 60*time.Second)
+				generated, genErr := generateAutoBranchSlug(genCtx, provider, resolved.Provider.Model, redactChangeSummary(summary))
+				cancel()
+				if genErr == nil && generated != "" {
+					llmSlug = generated
+				}
+			}
+		}
+		if llmSlug != "" {
+			slug = llmSlug
+		} else if !opts.JSONMode {
+			// Cover resolveConfig failures, missing provider profiles,
+			// newProvider errors, generation errors, and empty results so the
+			// user is not left guessing after "Generating..." or silence.
+			fmt.Fprintln(stdout, "LLM branch naming unavailable; using deterministic name.")
+		}
+	}
+
+	return branchPushPlan{
+		ShouldBranch:           true,
+		CurrentBranch:          currentBranch,
+		PushRemote:             pushRemote,
+		RequireNewRemoteBranch: true,
+		TrackingRemote:         trackingRemote,
+		TrackingBranch:         trackingBranch,
+		RestoreTip:             restoreTip,
+		PublishabilityBase:     baseRef,
+		Summary:                summary,
+		Slug:                   slug,
+	}, nil
+}
+
+// ensureFeatureBranch is the branch-naming step `zero changes push`/`pr` run
+// before pushing: pushing straight to the default branch is refused deeper in
+// zerogit.Push, so rather than surface that as a dead end, create and switch
+// to a conventionally named "<user>/<slug>" branch first. It returns the
+// branch push/pr should target, or "" to mean "current HEAD branch, unchanged"
+// (zerogit.Push already treats an empty Branch that way), plus the remote the
+// preflight resolved (requestedRemote, then the original branch's configured
+// upstream, then "origin"), plus whether Push should require that branch not
+// already exist on that remote. Callers must pass the remote to Push: a
+// freshly created branch has no tracking configuration, so Push's own
+// fallback would silently retarget "origin" even when the work came from a
+// branch tracking a different remote. Callers must also pass that third value
+// through as Push's RequireNewRemoteBranch: CreateBranch's own
+// remote-collision probe runs before this returns, and closing that race
+// requires Push's push itself to assert the destination is still new. That
+// requirement also carries across a retry: if the current branch is already
+// non-default (this call didn't create it) but has not been successfully
+// published to the exact target remote under the same branch name, keep the
+// nonexistence lease. branch.<name>.remote alone is not enough: with
+// branch.autoSetupMerge=inherit, checkout -b copies remote=origin from the
+// source branch before any push. After a successful create, the original
+// default branch ref is moved back to its own upstream tip (not necessarily
+// the push destination) so the feature branch exclusively owns the
+// publishable commits; a failed restore rolls the feature branch back.
+// allowDefaultBranch (the --yes flag) and dryRun both opt out via the ""
+// branch / false return, leaving Push's own guard/preview behavior on the
+// default branch unaffected.
+//
+// autoNaming gates the LLM naming path (--auto): these commands were
+// git-only, and sending the change diff to a configured provider on every
+// default-branch push would silently export source code nobody asked to
+// share. Without the opt-in the name comes from deterministic local
+// information only. maxDiffBytes caps the committed-range diff Inspect
+// returns, so a user who passed --diff-bytes to bound the proprietary source
+// sent for LLM naming has that cap honored here just as the commit path does.
+// The working tree must be clean and HEAD must be ahead of the resolved
+// remote branch; both are verified before any branch is created. The
+// inspectChanges, commitsAhead, headCommitSubject, currentGitUser, and
+// createBranch dependencies are required on the default-branch path and are
+// called without nil guards; fillAppDeps populates all of them. The
+// refreshTrackingRef, resolveRemoteBranchTip, isUnbornRemote, resetBranchRef,
+// and deleteBranch dependencies are optional and are skipped when nil.
+func ensureFeatureBranch(ctx context.Context, stdout io.Writer, workspaceRoot string, requestedRemote string, opts featureBranchOptions, deps appDeps) (string, string, bool, error) {
+	plan, err := resolveBranchPushPlan(ctx, stdout, workspaceRoot, requestedRemote, opts, deps)
+	if err != nil {
+		return "", "", false, err
+	}
+	if !plan.ShouldBranch {
+		return plan.CurrentBranch, plan.PushRemote, plan.RequireNewRemoteBranch, nil
+	}
+
+	expectedRestoreTip := ""
+	if deps.currentBranchTip != nil {
+		expectedRestoreTip = deps.currentBranchTip(ctx, workspaceRoot)
+	}
+
+	name := zerogit.BuildBranchName(deps.currentGitUser(ctx, workspaceRoot), plan.Slug)
+	result, err := deps.createBranch(ctx, zerogit.BranchOptions{Cwd: workspaceRoot, Name: name, Remote: plan.PushRemote})
+	if err != nil {
+		return "", "", false, fmt.Errorf("failed to create branch: %w", err)
+	}
+	// The normal flow commits on the default branch first, then creates the
+	// feature branch at the same HEAD. Without moving the original default
+	// ref back, local main keeps the pre-squash commits and diverges from
+	// its upstream after a squash-merge (and a later pull/push can re-publish
+	// them). Once the feature branch owns those commits, restore the default
+	// branch to the source branch's own upstream tip captured above.
+	// Failure-safe: if the restore fails, delete the feature branch and
+	// check the default branch back out so the tree is not left half-moved.
+	if deps.resetBranchRef != nil {
+		if err := deps.resetBranchRef(ctx, workspaceRoot, plan.CurrentBranch, plan.RestoreTip, expectedRestoreTip); err != nil {
+			// A compare-and-swap conflict means the default branch moved
+			// while we were branching, so restoreTip is no longer the tip we
+			// meant to restore. The rollback below deletes the branch that
+			// now exclusively owns the user's commits, which would destroy
+			// work to recover from a race we can simply report. Keep the
+			// branch and let the user reconcile the default branch.
+			if errors.Is(err, zerogit.ErrCompareAndSwapConflict) {
+				return "", "", false, fmt.Errorf("failed to restore default branch %s to %s after auto-branching: %w; generated branch %s was preserved because the default branch changed concurrently", plan.CurrentBranch, plan.RestoreTip, err, result.Branch)
+			}
+			var rollbackErr error
+			if deps.deleteBranch != nil {
+				rollbackErr = deps.deleteBranch(ctx, workspaceRoot, plan.CurrentBranch, result.Branch)
+			}
+			if rollbackErr != nil {
+				return "", "", false, fmt.Errorf("failed to restore default branch %s to %s after auto-branching: %w; rollback of %s also failed: %v", plan.CurrentBranch, plan.RestoreTip, err, result.Branch, rollbackErr)
+			}
+			return "", "", false, fmt.Errorf("failed to restore default branch %s to %s after auto-branching: %w", plan.CurrentBranch, plan.RestoreTip, err)
+		}
+	}
+	if !opts.JSONMode {
+		fmt.Fprintf(stdout, "Created branch %s (was on %s)\n", result.Branch, plan.CurrentBranch)
+	}
+	return result.Branch, plan.PushRemote, true, nil
+}
+
+// fallbackBranchSlug derives a deterministic branch-name slug from a change
+// summary without calling an LLM, so ensureFeatureBranch still works when no
+// provider is configured.
+func fallbackBranchSlug(summary zerogit.ChangeSummary) string {
+	switch len(summary.Files) {
+	case 0:
+		return "changes"
+	case 1:
+		// Git paths are always slash-separated regardless of platform, so
+		// path.Base (not filepath.Base) extracts the filename portably.
+		return zerogit.SlugifyBranchComponent(path.Base(summary.Files[0].Path))
+	default:
+		return fmt.Sprintf("update-%d-files", len(summary.Files))
+	}
+}
+
+// generateAutoBranchSlug asks the model for a short kebab-case slug
+// describing the diff, mirroring generateAutoCommitMessage's prompt shape.
+func generateAutoBranchSlug(ctx context.Context, provider zeroruntime.Provider, model string, summary zerogit.ChangeSummary) (string, error) {
+	var promptBuilder strings.Builder
+	promptBuilder.WriteString("Analyze the following git diff and generate a short git branch name slug for it.\n")
+	promptBuilder.WriteString("The slug must be 2 to 5 lowercase words separated by hyphens (kebab-case), using only letters, digits, and hyphens, with no prefix like \"feature/\" or \"fix/\" and no surrounding quotes.\n")
+	promptBuilder.WriteString("Output ONLY the raw slug text, nothing else.\n\n")
+	promptBuilder.WriteString("Git Diff:\n")
+	promptBuilder.WriteString(summary.Diff)
+
+	request := zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{
+			{Role: zeroruntime.MessageRoleUser, Content: promptBuilder.String()},
+		},
+	}
+	stream, err := provider.StreamCompletion(ctx, request)
+	if err != nil {
+		return "", err
+	}
+	collected := zeroruntime.CollectStream(ctx, stream)
+	if collected.Error != "" {
+		return "", fmt.Errorf("%s", collected.Error)
+	}
+
+	slug := zerogit.SlugifyBranchComponent(extractBranchSlug(collected.Text))
+	if slug == "" {
+		return "", fmt.Errorf("provider returned empty branch slug")
+	}
+	return slug, nil
+}
+
+// slugLineRe matches a line that already reads as a kebab-case slug (letters,
+// digits, and internal single hyphens only). extractBranchSlug prefers such a
+// line so a preamble sentence is never mistaken for the slug.
+var slugLineRe = regexp.MustCompile(`^[a-zA-Z0-9]+(-[a-zA-Z0-9]+)*$`)
+
+func isPreambleText(s string) bool {
+	lower := strings.ToLower(strings.TrimSpace(s))
+	if strings.HasSuffix(lower, ":") || strings.HasSuffix(lower, ".") || strings.HasSuffix(lower, "!") || strings.HasSuffix(lower, "?") {
+		return true
+	}
+	preambles := []string{
+		"here is", "here's", "below is", "below are", "sure", "certainly",
+		"i suggest", "suggested branch", "branch name", "recommended branch",
+		"how about", "you could use",
+	}
+	for _, p := range preambles {
+		if strings.HasPrefix(lower, p) {
+			return true
+		}
+	}
+	return false
+}
+
+// extractBranchSlug pulls the intended slug out of a model response that didn't
+// follow the "output only the raw slug" instruction exactly. It drops Markdown
+// code-fence lines, then prefers a line that already looks like a kebab-case
+// slug: that skips a leading preamble such as "Here is a suggested branch
+// name:" in favor of the "add-login-page" line that follows it. One-word
+// acknowledgements that happen to match the slug regex ("Sure", "Certainly")
+// are filtered as preamble before the early return, so "Sure\nadd login page"
+// yields the real suggestion. Inline labeled forms ("Branch name: add-login-page")
+// still work: the preamble check runs on the extracted value after the label
+// is stripped. If no line is strictly kebab-cased, it prefers a plausible
+// non-preamble line so plain multi-word replies still slugify correctly.
+func extractBranchSlug(text string) string {
+	var firstLine string
+
+	for _, line := range strings.Split(text, "\n") {
+		line = strings.TrimSpace(line)
+		if strings.HasPrefix(line, "```") {
+			continue
+		}
+		line = strings.TrimSpace(strings.Trim(line, `"'`))
+		if line == "" {
+			continue
+		}
+
+		candidate := line
+		if idx := strings.Index(line, ":"); idx != -1 {
+			after := strings.TrimSpace(strings.Trim(line[idx+1:], `"'`))
+			if after != "" {
+				candidate = after
+			}
+		}
+		// Models often terminate a suggestion with sentence punctuation;
+		// strip it so "add login page." is recovered as the slug rather than
+		// rejected as preamble (isPreambleText treats a trailing '.' as a
+		// full sentence). True preamble lines still match the prefix list.
+		candidate = strings.TrimSpace(strings.TrimRight(candidate, ".!?"))
+		if candidate == "" {
+			continue
+		}
+
+		// Preamble classification runs before accepting a slug-shaped line so
+		// "Sure" does not win over a later "add-login-page". The check is on
+		// candidate (post label-strip) so "Branch name: add-login-page" still
+		// returns the extracted slug.
+		if slugLineRe.MatchString(candidate) && !isPreambleText(candidate) {
+			return candidate
+		}
+
+		if firstLine == "" && !isPreambleText(candidate) {
+			firstLine = candidate
+		}
+	}
+
+	return firstLine
+}

internal/config/command_test.go

@@ -105,7 +105,17 @@ func TestLoadProviderCommandTimeout(t *testing.T) {
 //
 // This is a hang-breaker, not a tuned margin. Nothing in a healthy run waits on
 // it, since both tests return about one WaitDelay after the fixture exits.
-const providerCommandTestBudget = 60 * time.Second
+const (
+	providerCommandTestBudget        = 90 * time.Second
+	providerCommandReadyWaitAttempts = 45
+)
+
+func TestProviderCommandBudgetLeavesCleanupMargin(t *testing.T) {
+	readyWaitCeiling := time.Duration(providerCommandReadyWaitAttempts) * time.Second
+	if providerCommandTestBudget < 2*readyWaitCeiling {
+		t.Fatalf("provider command test budget %s leaves less than one readiness window for cleanup after %s", providerCommandTestBudget, readyWaitCeiling)
+	}
+}
 
 // backgroundChildLifetime must exceed providerCommandTestBudget so that a child
 // dying of old age is unobservable: any run where runProviderCommand has not
@@ -341,15 +351,15 @@ func writeCommand(t *testing.T, script commandScript) string {
 			// assertion fail is far more diagnosable than blocking until the
 			// timeout fires and reporting an unrelated error. Each iteration is
 			// about a second, since `ping -n 2` sleeps between its two echoes,
-			// so the ceiling is roughly 15s: far longer than any cold PowerShell
-			// start seen on a runner, and far shorter than
-			// providerCommandTestBudget, so giving up surfaces a legible
+			// so the ceiling is roughly 45s: enough for a heavily loaded Windows
+			// runner while leaving the other half of providerCommandTestBudget for
+			// process exit, PID-file verification, and cleanup. Giving up surfaces a legible
 			// PID-file failure rather than a timeout that hides the real cause.
 			lines = append(lines,
 				":zeroWaitReady",
 				"if exist \""+readyFile+"\" goto zeroReady",
 				"set /a ZERO_READY_TRIES+=1",
-				"if %ZERO_READY_TRIES% GEQ 15 goto zeroReady",
+				"if %ZERO_READY_TRIES% GEQ "+itoa(providerCommandReadyWaitAttempts)+" goto zeroReady",
 				"ping -n 2 127.0.0.1 >nul",
 				"goto zeroWaitReady",
 				":zeroReady",

internal/config/mcp_defaults.go

@@ -5,22 +5,20 @@ import (
 	"strings"
 )
 
-// DefaultMCPServers returns the MCP servers Zero ships ENABLED by default so web
-// search and scraping work out of the box with no setup and no API key. They are
-// seeded before user/project config is merged (see ResolveMCP), so a user can
-// override any field — for example point firecrawl at a self-hosted instance, or
-// add an API-key header to lift the free-tier limit — or disable it entirely with
+// DefaultMCPServers returns the MCP servers Zero ships ENABLED by default so
+// web search and page fetching work out of the box with no setup and no API
+// key. They are seeded before user/project config is merged (see ResolveMCP),
+// so a user can override any field — for example add an API-key header to lift
+// Exa's anonymous rate limit — or disable it entirely with
 // `zero mcp disable <name>` (which writes `"disabled": true`).
 //
-// Keyless Firecrawl routes requests through firecrawl.dev (1,000 free credits per
-// month, no account). Self-host Firecrawl (AGPL-3.0) for unlimited and private
-// use. Zero only calls it over the network, so Firecrawl's license never reaches
-// into Zero's own code.
+// Exa's hosted MCP server works anonymously with rate limits. Users can add an
+// Exa API key for higher limits.
 func DefaultMCPServers() map[string]MCPServerConfig {
 	return map[string]MCPServerConfig{
-		"firecrawl": {
+		"exa": {
 			Type: "http",
-			URL:  "https://mcp.firecrawl.dev/v2/mcp",
+			URL:  "https://mcp.exa.ai/mcp",
 		},
 	}
 }
@@ -35,13 +33,13 @@ func IsDefaultMCPServer(name string) bool {
 
 // IsUnconfiguredDefault reports whether server is one of Zero's built-in
 // defaults that the user never wrote an entry for in their config — i.e. it is
-// running with whatever Zero ships (e.g. keyless Firecrawl, no credentials).
+// running with whatever Zero ships (e.g. keyless Exa, no credentials).
 //
 // Both conditions below must hold:
 //   - !server.configured: the user's JSON never declared an object for this
 //     server key at all (set by MCPServerConfig.UnmarshalJSON only when it
 //     actually ran for this key). Any explicit action — including a
-//     disable/enable toggle like `zero mcp enable firecrawl` that leaves the
+//     disable/enable toggle like `zero mcp enable exa` that leaves the
 //     resolved value unchanged — sets configured, so it always counts as
 //     user-configured, even though the value comparison below could not tell
 //     the difference on its own.
@@ -58,3 +56,90 @@ func IsUnconfiguredDefault(name string, server MCPServerConfig) bool {
 	def, ok := DefaultMCPServers()[strings.TrimSpace(name)]
 	return ok && !server.configured && reflect.DeepEqual(def, server)
 }
+
+// retiredDefaultMCPServer describes a built-in default Zero no longer ships.
+type retiredDefaultMCPServer struct {
+	// successor is the default that replaced it.
+	successor string
+	// shipped is the value Zero used to seed for this name. A user entry
+	// written while the default was still shipped may name only an override
+	// (a header, say) and rely on these fields for the rest, so they have to
+	// outlive the default itself.
+	shipped MCPServerConfig
+}
+
+// retiredDefaultMCPServers maps a retired built-in default to what replaced it
+// and to the value Zero used to ship for it.
+var retiredDefaultMCPServers = map[string]retiredDefaultMCPServer{
+	"firecrawl": {
+		successor: "exa",
+		shipped: MCPServerConfig{
+			Type: "http",
+			URL:  "https://mcp.firecrawl.dev/v2/mcp",
+		},
+	},
+}
+
+// migrateRetiredDefaultMCPServers keeps an upgrade across a default-provider
+// swap from changing what the user's config means. It handles the two ways a
+// rename can break a config written against the old default:
+//
+//   - A user who ran `zero mcp disable <old default>` made an explicit choice
+//     not to open that outbound connection. Without carrying that decision to
+//     the successor, the upgrade re-opens it under the new name — and because
+//     the replacement looks like an untouched default, even the startup
+//     warning stays quiet (see IsUnconfiguredDefault and issue #552).
+//   - A user who customized the old default could name only the field they
+//     were changing, because the seeded default supplied the transport. Once
+//     the default stops being seeded that entry resolves to a server with no
+//     type, url, or command, which fails NormalizeConfig and takes the whole
+//     startup down rather than just that one server.
+//
+// It runs immediately after the user layer merges (see ResolveMCP), which
+// scopes it to user-level decisions — the only scope whose disable is sticky.
+// The carried-over disable applies only when the user never declared the
+// successor themselves: an explicit `exa` entry wins whether it enables or
+// disables. Because the disable is recorded as a user-level decision, the
+// lower-trust project layer cannot lift it, while `zero mcp enable exa` still
+// can (the CLI override scope merges with canReenable=true).
+func migrateRetiredDefaultMCPServers(cfg *MCPConfig) {
+	for name, retired := range retiredDefaultMCPServers {
+		entry, ok := cfg.Servers[name]
+		if !ok {
+			continue
+		}
+		if inheritsRetiredTransport(entry) {
+			// Re-seed what Zero used to ship underneath the user's fields, so a
+			// partial entry still resolves to the complete server it named when
+			// it was written. Their own values still win — this only fills the
+			// gap the retired default used to cover.
+			entry = mergeMCPServer(retired.shipped, entry, true)
+			cfg.Servers[name] = entry
+		}
+		if !entry.disabledSet || !entry.Disabled {
+			continue
+		}
+		replacement, ok := cfg.Servers[retired.successor]
+		if !ok || replacement.configured {
+			continue
+		}
+		replacement.Disabled = true
+		replacement.disabledSet = true
+		cfg.Servers[retired.successor] = replacement
+	}
+}
+
+// inheritsRetiredTransport reports whether entry named no transport of its own
+// — no type, url, command, or args — and so relied entirely on the retired
+// default to supply one.
+//
+// Anything else is a complete definition the user owns (a self-hosted url, a
+// stdio command) and must be left alone: grafting the retired default's http
+// type onto an entry that names a command produces a server that is rejected
+// outright, turning a working config into a startup failure.
+func inheritsRetiredTransport(entry MCPServerConfig) bool {
+	return strings.TrimSpace(entry.Type) == "" &&
+		strings.TrimSpace(entry.URL) == "" &&
+		strings.TrimSpace(entry.Command) == "" &&
+		len(entry.Args) == 0
+}

internal/config/mcp_defaults_test.go

@@ -7,10 +7,10 @@ import (
 )
 
 func TestIsDefaultMCPServer(t *testing.T) {
-	if !IsDefaultMCPServer("firecrawl") {
-		t.Fatal("firecrawl should be a built-in default")
+	if !IsDefaultMCPServer("exa") {
+		t.Fatal("exa should be a built-in default")
 	}
-	if IsDefaultMCPServer("  firecrawl  ") == false {
+	if IsDefaultMCPServer("  exa  ") == false {
 		t.Fatal("IsDefaultMCPServer should trim whitespace")
 	}
 	if IsDefaultMCPServer("not-a-default") {
@@ -18,45 +18,45 @@ func TestIsDefaultMCPServer(t *testing.T) {
 	}
 }
 
-func TestResolveMCPSeedsEnabledFirecrawlDefault(t *testing.T) {
+func TestResolveMCPSeedsEnabledExaDefault(t *testing.T) {
 	cfg, err := ResolveMCP(ResolveOptions{})
 	if err != nil {
 		t.Fatalf("ResolveMCP: %v", err)
 	}
-	firecrawl, ok := cfg.Servers["firecrawl"]
+	exa, ok := cfg.Servers["exa"]
 	if !ok {
-		t.Fatal("expected the firecrawl default to be seeded with no user config")
+		t.Fatal("expected the exa default to be seeded with no user config")
 	}
-	if firecrawl.Type != "http" || firecrawl.URL != "https://mcp.firecrawl.dev/v2/mcp" {
-		t.Fatalf("unexpected firecrawl default: %#v", firecrawl)
+	if exa.Type != "http" || exa.URL != "https://mcp.exa.ai/mcp" {
+		t.Fatalf("unexpected exa default: %#v", exa)
 	}
-	if firecrawl.Disabled {
-		t.Fatal("the firecrawl default must be enabled out of the box")
+	if exa.Disabled {
+		t.Fatal("the exa default must be enabled out of the box")
 	}
 }
 
 func TestResolveMCPUserCanDisableDefault(t *testing.T) {
 	path := filepath.Join(t.TempDir(), "config.json")
-	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"disabled":true}}}}`), 0o600); err != nil {
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"exa":{"disabled":true}}}}`), 0o600); err != nil {
 		t.Fatal(err)
 	}
 	cfg, err := ResolveMCP(ResolveOptions{UserConfigPath: path})
 	if err != nil {
 		t.Fatalf("ResolveMCP: %v", err)
 	}
-	if !cfg.Servers["firecrawl"].Disabled {
+	if !cfg.Servers["exa"].Disabled {
 		t.Fatal("a user must be able to disable the default by writing over it")
 	}
 }
 
 func TestIsUnconfiguredDefault(t *testing.T) {
-	if !IsUnconfiguredDefault("firecrawl", DefaultMCPServers()["firecrawl"]) {
-		t.Fatal("an untouched firecrawl default should be reported as unconfigured")
+	if !IsUnconfiguredDefault("exa", DefaultMCPServers()["exa"]) {
+		t.Fatal("an untouched exa default should be reported as unconfigured")
 	}
-	if IsUnconfiguredDefault("firecrawl", MCPServerConfig{Type: "http", URL: "http://localhost:3002/mcp"}) {
+	if IsUnconfiguredDefault("exa", MCPServerConfig{Type: "http", URL: "https://example.com/mcp"}) {
 		t.Fatal("a server overriding the default URL is no longer unconfigured")
 	}
-	if IsUnconfiguredDefault("firecrawl", MCPServerConfig{Type: "http", URL: "https://mcp.firecrawl.dev/v2/mcp", Auth: "bearer"}) {
+	if IsUnconfiguredDefault("exa", MCPServerConfig{Type: "http", URL: "https://mcp.exa.ai/mcp", Auth: "bearer"}) {
 		t.Fatal("a server with credentials added is no longer unconfigured")
 	}
 	if IsUnconfiguredDefault("not-a-default", MCPServerConfig{}) {
@@ -65,57 +65,173 @@ func TestIsUnconfiguredDefault(t *testing.T) {
 }
 
 func TestResolveMCPExplicitReenableIsNotUnconfiguredDefault(t *testing.T) {
-	// `zero mcp enable firecrawl` after a prior disable writes {"disabled":false}
+	// `zero mcp enable exa` after a prior disable writes {"disabled":false}
 	// explicitly. The resolved value is identical to the untouched default (both
 	// enabled, no credentials), but the user DID take an explicit action here, so
 	// IsUnconfiguredDefault must not treat it as untouched (issue #563 review).
 	path := filepath.Join(t.TempDir(), "config.json")
-	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"disabled":false}}}}`), 0o600); err != nil {
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"exa":{"disabled":false}}}}`), 0o600); err != nil {
 		t.Fatal(err)
 	}
 	cfg, err := ResolveMCP(ResolveOptions{UserConfigPath: path})
 	if err != nil {
 		t.Fatalf("ResolveMCP: %v", err)
 	}
-	firecrawl := cfg.Servers["firecrawl"]
-	if firecrawl.Disabled {
-		t.Fatalf("explicit re-enable should leave the server enabled: %#v", firecrawl)
+	exa := cfg.Servers["exa"]
+	if exa.Disabled {
+		t.Fatalf("explicit re-enable should leave the server enabled: %#v", exa)
 	}
-	if IsUnconfiguredDefault("firecrawl", firecrawl) {
+	if IsUnconfiguredDefault("exa", exa) {
 		t.Fatal("an explicit enable/disable toggle must count as user-configured, even though the resolved value matches the default")
 	}
 }
 
 func TestResolveMCPExplicitRedeclareOfDefaultValuesIsNotUnconfiguredDefault(t *testing.T) {
-	// A user who copies firecrawl's exact default type/url into their config
+	// A user who copies Exa's exact default type/url into their config
 	// (e.g. from an example file, planning to add credentials later) produces a
-	// resolved value byte-identical to DefaultMCPServers()["firecrawl"] — the
+	// resolved value byte-identical to DefaultMCPServers()["exa"] — the
 	// same trap TestResolveMCPExplicitReenableIsNotUnconfiguredDefault covers for
 	// the disabled toggle. IsUnconfiguredDefault must still treat this as
 	// user-configured because the user's JSON declared an entry for it, even
 	// though a plain resolved-value comparison could not tell the difference.
 	path := filepath.Join(t.TempDir(), "config.json")
-	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"type":"http","url":"https://mcp.firecrawl.dev/v2/mcp"}}}}`), 0o600); err != nil {
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"exa":{"type":"http","url":"https://mcp.exa.ai/mcp"}}}}`), 0o600); err != nil {
 		t.Fatal(err)
 	}
 	cfg, err := ResolveMCP(ResolveOptions{UserConfigPath: path})
 	if err != nil {
 		t.Fatalf("ResolveMCP: %v", err)
 	}
-	firecrawl := cfg.Servers["firecrawl"]
-	want := DefaultMCPServers()["firecrawl"]
-	if firecrawl.Type != want.Type || firecrawl.URL != want.URL || firecrawl.Disabled != want.Disabled {
-		t.Fatalf("expected the resolved value to match the default's fields exactly: %#v", firecrawl)
+	exa := cfg.Servers["exa"]
+	want := DefaultMCPServers()["exa"]
+	if exa.Type != want.Type || exa.URL != want.URL || exa.Disabled != want.Disabled {
+		t.Fatalf("expected the resolved value to match the default's fields exactly: %#v", exa)
 	}
-	if IsUnconfiguredDefault("firecrawl", firecrawl) {
+	if IsUnconfiguredDefault("exa", exa) {
 		t.Fatal("redeclaring the default's exact values is still an explicit user configuration, not an untouched default")
 	}
 }
 
 func TestResolveMCPUserCanOverrideDefaultURLKeepingOtherFields(t *testing.T) {
 	path := filepath.Join(t.TempDir(), "config.json")
-	// Point firecrawl at a self-hosted instance; the default's Type must survive.
-	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"url":"http://localhost:3002/mcp"}}}}`), 0o600); err != nil {
+	// Point Exa at a proxy; the default's Type must survive.
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"exa":{"url":"https://example.com/mcp"}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := ResolveMCP(ResolveOptions{UserConfigPath: path})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	exa := cfg.Servers["exa"]
+	if exa.URL != "https://example.com/mcp" {
+		t.Fatalf("user override of the default URL did not apply: %#v", exa)
+	}
+	if exa.Type != "http" {
+		t.Fatalf("override should keep the default's other fields (type), got %#v", exa)
+	}
+}
+
+func TestResolveMCPCarriesLegacyDefaultDisableToSuccessor(t *testing.T) {
+	// Upgrade path: the user disabled the firecrawl default Zero used to ship.
+	// Swapping the default to exa must not re-open an outbound connection they
+	// explicitly switched off.
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"disabled":true}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := ResolveMCP(ResolveOptions{UserConfigPath: path})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	if !cfg.Servers["exa"].Disabled {
+		t.Fatalf("a prior disable of the retired default must carry to its replacement: %#v", cfg.Servers["exa"])
+	}
+}
+
+func TestResolveMCPExplicitSuccessorBeatsLegacyDefaultDisable(t *testing.T) {
+	// The user disabled the old default but has since explicitly configured exa.
+	// Their newer, explicit choice wins — the migration must not override it.
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"disabled":true},"exa":{"disabled":false}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := ResolveMCP(ResolveOptions{UserConfigPath: path})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	exa := cfg.Servers["exa"]
+	if exa.Disabled {
+		t.Fatalf("an explicit exa entry must survive the legacy-disable migration: %#v", exa)
+	}
+	if IsUnconfiguredDefault("exa", exa) {
+		t.Fatal("an explicitly configured exa is not an untouched default")
+	}
+}
+
+func TestResolveMCPLegacyDefaultLeftEnabledDoesNotDisableSuccessor(t *testing.T) {
+	// A user who configured firecrawl without disabling it (e.g. added a header)
+	// never opted out of the default search server, so exa stays enabled.
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"headers":{"Authorization":"Bearer k"}}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := ResolveMCP(ResolveOptions{UserConfigPath: path})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	if cfg.Servers["exa"].Disabled {
+		t.Fatal("only an explicit disable of the retired default should carry over")
+	}
+}
+
+func TestResolveMCPLegacyDefaultDisableIsLiftableByOverride(t *testing.T) {
+	// The carried-over disable is a user-level decision, not a permanent one:
+	// `zero mcp enable exa` merges through the CLI override scope, which is the
+	// one layer allowed to re-enable.
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"disabled":true}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	enabled := MCPServerConfig{Disabled: false, disabledSet: true}
+	cfg, err := ResolveMCP(ResolveOptions{
+		UserConfigPath: path,
+		Overrides:      Overrides{MCP: MCPConfig{Servers: map[string]MCPServerConfig{"exa": enabled}}},
+	})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	if cfg.Servers["exa"].Disabled {
+		t.Fatalf("an explicit enable must lift the carried-over disable: %#v", cfg.Servers["exa"])
+	}
+}
+
+func TestResolveMCPLegacyDisableSurvivesProjectReenable(t *testing.T) {
+	// The project layer is lower-trust and must not lift the carried-over
+	// user-level disable — the same guard a direct `zero mcp disable exa` gets.
+	dir := t.TempDir()
+	userPath := filepath.Join(dir, "config.json")
+	if err := os.WriteFile(userPath, []byte(`{"mcp":{"servers":{"firecrawl":{"disabled":true}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	projectPath := filepath.Join(dir, "project.json")
+	if err := os.WriteFile(projectPath, []byte(`{"mcp":{"servers":{"exa":{"disabled":false}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := ResolveMCP(ResolveOptions{UserConfigPath: userPath, ProjectConfigPath: projectPath})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	if !cfg.Servers["exa"].Disabled {
+		t.Fatal("project config must not re-enable a server the user disabled")
+	}
+}
+
+func TestResolveMCPKeepsRetiredDefaultTransportForPartialEntry(t *testing.T) {
+	// A user who added an API key to the firecrawl default wrote only the header
+	// — the seeded default supplied the http type and URL. Retiring the default
+	// must not strip those out from under them and leave an unusable server.
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"headers":{"Authorization":"Bearer k"}}}}}`), 0o600); err != nil {
 		t.Fatal(err)
 	}
 	cfg, err := ResolveMCP(ResolveOptions{UserConfigPath: path})
@@ -123,10 +239,55 @@ func TestResolveMCPUserCanOverrideDefaultURLKeepingOtherFields(t *testing.T) {
 		t.Fatalf("ResolveMCP: %v", err)
 	}
 	firecrawl := cfg.Servers["firecrawl"]
-	if firecrawl.URL != "http://localhost:3002/mcp" {
-		t.Fatalf("user override of the default URL did not apply: %#v", firecrawl)
+	if firecrawl.Type != "http" || firecrawl.URL != "https://mcp.firecrawl.dev/v2/mcp" {
+		t.Fatalf("a partial entry must keep the retired default's transport: %#v", firecrawl)
 	}
-	if firecrawl.Type != "http" {
-		t.Fatalf("override should keep the default's other fields (type), got %#v", firecrawl)
+	if firecrawl.Headers["Authorization"] != "Bearer k" {
+		t.Fatalf("the user's own field must still win: %#v", firecrawl)
+	}
+}
+
+func TestResolveMCPDoesNotGraftRetiredDefaultOntoOwnTransport(t *testing.T) {
+	// A self-hosted firecrawl over stdio is a complete definition the user owns.
+	// Re-seeding the retired http default under it would produce an http server
+	// carrying a command, which NormalizeConfig rejects outright.
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"command":"firecrawl-mcp"}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := ResolveMCP(ResolveOptions{UserConfigPath: path})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	firecrawl := cfg.Servers["firecrawl"]
+	if firecrawl.Type != "" || firecrawl.URL != "" {
+		t.Fatalf("an entry naming its own transport must be left alone: %#v", firecrawl)
+	}
+	if firecrawl.Command != "firecrawl-mcp" {
+		t.Fatalf("the user's command must survive: %#v", firecrawl)
+	}
+}
+
+func TestResolveMCPDisabledRetiredEntryStaysReEnableable(t *testing.T) {
+	// The disable carries to exa, and the retired entry itself keeps a usable
+	// transport so a later `zero mcp enable firecrawl` does not resolve to a
+	// server with no type, url, or command.
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"disabled":true}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := ResolveMCP(ResolveOptions{UserConfigPath: path})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	firecrawl := cfg.Servers["firecrawl"]
+	if !firecrawl.Disabled {
+		t.Fatalf("the retired entry must stay disabled: %#v", firecrawl)
+	}
+	if firecrawl.Type != "http" || firecrawl.URL != "https://mcp.firecrawl.dev/v2/mcp" {
+		t.Fatalf("a disabled retired entry should still carry a usable transport: %#v", firecrawl)
+	}
+	if !cfg.Servers["exa"].Disabled {
+		t.Fatal("the disable must still carry to the successor")
 	}
 }

internal/config/resolve_mcp_exclude_project_test.go

@@ -34,7 +34,7 @@ func TestResolveMCPExcludeProjectDropsProjectServers(t *testing.T) {
 		if _, ok := cfg.Servers["user-srv"]; !ok {
 			t.Fatal("the user server must always be present")
 		}
-		if _, ok := cfg.Servers["firecrawl"]; !ok {
+		if _, ok := cfg.Servers["exa"]; !ok {
 			t.Fatal("the built-in default must always be present")
 		}
 	})
@@ -54,7 +54,7 @@ func TestResolveMCPExcludeProjectDropsProjectServers(t *testing.T) {
 		if _, ok := cfg.Servers["user-srv"]; !ok {
 			t.Fatal("the user server must survive when the project layer is dropped")
 		}
-		if _, ok := cfg.Servers["firecrawl"]; !ok {
+		if _, ok := cfg.Servers["exa"]; !ok {
 			t.Fatal("the built-in default must survive when the project layer is dropped")
 		}
 	})

internal/config/resolver.go

@@ -180,7 +180,7 @@ func Resolve(options ResolveOptions) (ResolvedConfig, error) {
 }
 
 func ResolveMCP(options ResolveOptions) (MCPConfig, error) {
-	// Seed Zero's built-in default MCP servers (e.g. keyless Firecrawl for free,
+	// Seed Zero's built-in default MCP servers (e.g. keyless Exa for free,
 	// no-setup web search/scrape) BEFORE merging user/project config, so the user
 	// can override any field or disable a default by writing over it.
 	cfg := FileConfig{MCP: MCPConfig{Servers: DefaultMCPServers()}}
@@ -194,6 +194,10 @@ func ResolveMCP(options ResolveOptions) (MCPConfig, error) {
 		// server the user disabled (a user-level disable is sticky, but the user
 		// scope itself may lift it).
 		mergeMCPConfig(&cfg.MCP, fileConfig.MCP, true)
+		// Reconcile config written against a default Zero has since retired,
+		// here while the user layer is the only one merged — so a carried-over
+		// disable counts as a user-level decision the project layer cannot lift.
+		migrateRetiredDefaultMCPServers(&cfg.MCP)
 	}
 	// Drop the project layer when the workspace is untrusted, so a cloned repo's
 	// ./.zero/config.json cannot register (and spawn) MCP servers. Fail-closed:

internal/config/types.go

@@ -151,7 +151,8 @@ type KeyBindingsConfig struct {
 	ToggleMouse KeyBindingDef `json:"toggleMouse,omitempty"`
 	// CycleReasoning cycles through reasoning effort levels (default: ctrl+t).
 	CycleReasoning KeyBindingDef `json:"cycleReasoning,omitempty"`
-	// TogglePlan toggles the plan panel expansion (default: ctrl+p).
+	// TogglePlan is retained for configuration compatibility. Plan updates render
+	// in the transcript and no longer have a persistent panel to toggle.
 	TogglePlan KeyBindingDef `json:"togglePlan,omitempty"`
 	// ToggleSidebar toggles the right context sidebar (default: ctrl+b).
 	ToggleSidebar KeyBindingDef `json:"toggleSidebar,omitempty"`
@@ -464,7 +465,7 @@ type MCPServerConfig struct {
 	// fields it set or what values they hold. A built-in default seeded by
 	// DefaultMCPServers() is never unmarshaled from JSON, so it starts false;
 	// any explicit entry in the user/project file — even one that happens to
-	// repeat a default's exact field values (e.g. re-declaring firecrawl's
+	// repeat a default's exact field values (e.g. re-declaring Exa's
 	// default URL) — sets it true. IsUnconfiguredDefault checks this alongside
 	// a resolved-value comparison, so redeclaring default values verbatim still
 	// counts as user-configured.

internal/credstore/concurrency_test.go

@@ -0,0 +1,246 @@
+package credstore
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"sync"
+	"testing"
+)
+
+func fileStore(t *testing.T, dir string) *Store {
+	t.Helper()
+	store, err := New(Options{Dir: dir, Storage: "file"})
+	if err != nil {
+		t.Fatalf("New: %v", err)
+	}
+	return store
+}
+
+// THE REPRODUCTION, kept as the regression. Before the lock this reliably kept
+// 1 of 100: every writer read the same map, added its own provider, and the
+// last rename published a file missing all the others.
+func TestConcurrentSetKeepsEveryKey(t *testing.T) {
+	dir := t.TempDir()
+	store := fileStore(t, dir)
+
+	const n = 100
+	var wg sync.WaitGroup
+	errs := make(chan error, n)
+	for i := 0; i < n; i++ {
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+			if err := store.Set(fmt.Sprintf("p%03d", i), fmt.Sprintf("k%03d", i)); err != nil {
+				errs <- err
+			}
+		}(i)
+	}
+	wg.Wait()
+	close(errs)
+	for err := range errs {
+		t.Fatalf("Set: %v", err)
+	}
+
+	got, err := store.Providers()
+	if err != nil {
+		t.Fatalf("Providers: %v", err)
+	}
+	if len(got) != n {
+		t.Fatalf("kept %d of %d concurrent writes", len(got), n)
+	}
+	// ...and every value is the one its own writer wrote, not a neighbour's.
+	for i := 0; i < n; i++ {
+		key, ok, err := store.Get(fmt.Sprintf("p%03d", i))
+		if err != nil {
+			t.Fatalf("Get: %v", err)
+		}
+		if !ok || key != fmt.Sprintf("k%03d", i) {
+			t.Fatalf("p%03d = %q (present=%v); a writer's own value must survive", i, key, ok)
+		}
+	}
+}
+
+// DELETE RACES SET, and an unlocked delete loses the other writer's key.
+//
+// A first version of this only checked that keys nobody deleted survived — and
+// every reader sees those, so it passed with the lock removed from Delete. The
+// case that actually breaks is a Delete whose stale read predates a concurrent
+// Set: it writes back a map that never contained the new key, and the Set is
+// gone. So the assertion is on the SETS surviving, not on the bystanders.
+func TestADeleteCannotClobberAConcurrentSet(t *testing.T) {
+	dir := t.TempDir()
+	store := fileStore(t, dir)
+
+	// Throwaway keys for the deleters to remove, written first so a delete
+	// always has something to do.
+	const churn = 40
+	for i := 0; i < churn; i++ {
+		if err := store.Set(fmt.Sprintf("churn%02d", i), "v"); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	const adds = 60
+	var wg sync.WaitGroup
+	for i := 0; i < adds; i++ {
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+			_ = store.Set(fmt.Sprintf("added%02d", i), "v")
+		}(i)
+	}
+	for i := 0; i < churn; i++ {
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+			_, _ = store.Delete(fmt.Sprintf("churn%02d", i))
+		}(i)
+	}
+	wg.Wait()
+
+	got, err := store.Providers()
+	if err != nil {
+		t.Fatal(err)
+	}
+	survivors := map[string]bool{}
+	for _, name := range got {
+		survivors[name] = true
+	}
+	missing := []string{}
+	for i := 0; i < adds; i++ {
+		name := fmt.Sprintf("added%02d", i)
+		if !survivors[name] {
+			missing = append(missing, name)
+		}
+	}
+	if len(missing) > 0 {
+		t.Fatalf("%d of %d concurrent Set calls were clobbered by a racing Delete: %v",
+			len(missing), adds, missing)
+	}
+	// ...and every churn key really was removed, so the deletes were not
+	// no-ops that would make the check above vacuous.
+	for i := 0; i < churn; i++ {
+		if survivors[fmt.Sprintf("churn%02d", i)] {
+			t.Fatalf("churn%02d survived; the deletes did nothing and this test proves nothing", i)
+		}
+	}
+}
+
+// ACROSS PROCESSES, which is the case that matters: a plan running with
+// max_workers > 1 spawns child PROCESSES, and an in-process mutex would not
+// have helped any of them. The race detector cannot see this one either — it is
+// two OS processes — so it is driven for real.
+func TestConcurrentSetAcrossProcesses(t *testing.T) {
+	if testing.Short() {
+		t.Skip("spawns processes")
+	}
+	helper := os.Getenv("ZERO_CREDSTORE_HELPER_DIR")
+	if helper != "" {
+		// Child mode: write our slice of the keys and exit.
+		store, err := New(Options{Dir: helper, Storage: "file"})
+		if err != nil {
+			os.Exit(3)
+		}
+		prefix := os.Getenv("ZERO_CREDSTORE_HELPER_PREFIX")
+		for i := 0; i < 25; i++ {
+			if err := store.Set(fmt.Sprintf("%s%02d", prefix, i), "v"); err != nil {
+				os.Exit(4)
+			}
+		}
+		os.Exit(0)
+	}
+
+	dir := t.TempDir()
+	const children = 4
+	var wg sync.WaitGroup
+	failures := make(chan string, children)
+	for c := 0; c < children; c++ {
+		wg.Add(1)
+		go func(c int) {
+			defer wg.Done()
+			cmd := exec.Command(os.Args[0], "-test.run=TestConcurrentSetAcrossProcesses", "-test.v")
+			cmd.Env = append(os.Environ(),
+				"ZERO_CREDSTORE_HELPER_DIR="+dir,
+				fmt.Sprintf("ZERO_CREDSTORE_HELPER_PREFIX=c%d_", c),
+			)
+			if out, err := cmd.CombinedOutput(); err != nil {
+				failures <- fmt.Sprintf("child %d: %v\n%s", c, err, out)
+			}
+		}(c)
+	}
+	wg.Wait()
+	close(failures)
+	for failure := range failures {
+		t.Fatal(failure)
+	}
+
+	store := fileStore(t, dir)
+	got, err := store.Providers()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != children*25 {
+		t.Fatalf("kept %d of %d keys written by %d concurrent processes", len(got), children*25, children)
+	}
+}
+
+// The lock lives BESIDE the data file, never on it. write publishes by rename,
+// so a lock taken on the data file would be attached to an inode the next
+// writer has already replaced — every writer would appear to hold it.
+func TestTheLockIsNotTheDataFile(t *testing.T) {
+	dir := t.TempDir()
+	store := fileStore(t, dir)
+	if store.lockPath() == store.file {
+		t.Fatal("the lock is the data file; rename would carry it away")
+	}
+	if !strings.HasPrefix(filepath.Base(store.lockPath()), filepath.Base(store.file)) {
+		t.Fatalf("lock %q is not beside the data file %q", store.lockPath(), store.file)
+	}
+	if err := store.Set("p", "k"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(store.lockPath()); err != nil {
+		t.Fatalf("the lock file was not created: %v", err)
+	}
+	// ...and it survives a write, since the rename replaces only the data file.
+	if err := store.Set("q", "k"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(store.lockPath()); err != nil {
+		t.Fatalf("the lock file did not survive a write: %v", err)
+	}
+}
+
+// The lock is a security boundary, so the path where it CANNOT be taken needs
+// coverage too: an operation that could not lock must report that, never proceed
+// unserialized and never report success. Replacing the credential directory with
+// a regular file makes the lock's MkdirAll fail on every platform.
+func TestOperationsFailWhenTheLockCannotBeAcquired(t *testing.T) {
+	base := t.TempDir()
+	dir := filepath.Join(base, "creds")
+	store := fileStore(t, dir)
+	// Where the store expects its directory, put a regular file.
+	if err := os.WriteFile(dir, []byte("not a directory"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := store.Set("openai", "sk-test"); err == nil {
+		t.Error("Set reported success although the lock could not be acquired")
+	}
+	if _, err := store.Delete("openai"); err == nil {
+		t.Error("Delete reported success although the lock could not be acquired")
+	}
+	if _, _, err := store.Get("openai"); err == nil {
+		t.Error("Get reported success although the lock could not be acquired")
+	}
+	if _, err := store.Providers(); err == nil {
+		t.Error("Providers reported success although the lock could not be acquired")
+	}
+	// And nothing may have been written through the failed path.
+	if raw, err := os.ReadFile(dir); err != nil || string(raw) != "not a directory" {
+		t.Errorf("the blocking file was modified: %q (err %v)", raw, err)
+	}
+}

internal/credstore/credstore.go

@@ -9,6 +9,7 @@ package credstore
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -125,14 +126,27 @@ func (s *Store) Backend() string { return s.backend }
 func (s *Store) Encrypted() bool { return s.backend == "keyring" || s.backend == "encrypted-file" }
 
 // Set stores (or overwrites) the API key for provider.
-func (s *Store) Set(provider, key string) error {
+func (s *Store) Set(provider, key string) (err error) {
 	provider = normalizeProvider(provider)
 	if provider == "" {
 		return fmt.Errorf("credstore: provider is required")
 	}
 	if s.backend == "keyring" {
+		// The OS keyring serializes its own writes; the file lock guards the
+		// file backends only.
 		return s.kr.Set(keyringService, keyringPrefix+provider, key)
 	}
+	// READ AND WRITE UNDER ONE LOCK. Separately locking each half would still
+	// lose keys: two writers would each read the same map, each add their own
+	// provider, and the second rename would publish a file missing the first.
+	// Measured before this existed: 1 of 100 concurrent Set calls survived.
+	release, err := s.acquireFileLock(true)
+	if err != nil {
+		return err
+	}
+	// Joined, not chosen between: a release failure annotates the result instead
+	// of masking the write error that actually explains what went wrong.
+	defer func() { err = errors.Join(err, release()) }()
 	data, err := s.read()
 	if err != nil {
 		return err
@@ -142,7 +156,7 @@ func (s *Store) Set(provider, key string) error {
 }
 
 // Get returns the API key for provider and whether one is stored.
-func (s *Store) Get(provider string) (string, bool, error) {
+func (s *Store) Get(provider string) (value string, found bool, err error) {
 	provider = normalizeProvider(provider)
 	if provider == "" {
 		return "", false, nil
@@ -150,6 +164,15 @@ func (s *Store) Get(provider string) (string, bool, error) {
 	if s.backend == "keyring" {
 		return s.kr.Get(keyringService, keyringPrefix+provider)
 	}
+	// A shared lock, so a read serializes against a writer's publish. On unix
+	// the rename is atomic and this only prevents reading an empty file mid-swap;
+	// on Windows an unsynchronized reader holding the file open would block the
+	// writer's rename outright, so readers must coordinate through the same lock.
+	release, err := s.acquireFileLock(false)
+	if err != nil {
+		return "", false, err
+	}
+	defer func() { err = errors.Join(err, release()) }()
 	data, err := s.read()
 	if err != nil {
 		return "", false, err
@@ -159,7 +182,7 @@ func (s *Store) Get(provider string) (string, bool, error) {
 }
 
 // Delete removes the API key for provider, reporting whether one existed.
-func (s *Store) Delete(provider string) (bool, error) {
+func (s *Store) Delete(provider string) (existed bool, err error) {
 	provider = normalizeProvider(provider)
 	if provider == "" {
 		return false, nil
@@ -167,6 +190,13 @@ func (s *Store) Delete(provider string) (bool, error) {
 	if s.backend == "keyring" {
 		return s.kr.Delete(keyringService, keyringPrefix+provider)
 	}
+	// The same lock as Set: a delete is a read-modify-write too, and one racing
+	// a set would otherwise resurrect or erase an unrelated provider.
+	release, err := s.acquireFileLock(true)
+	if err != nil {
+		return false, err
+	}
+	defer func() { err = errors.Join(err, release()) }()
 	data, err := s.read()
 	if err != nil {
 		return false, err
@@ -179,17 +209,22 @@ func (s *Store) Delete(provider string) (bool, error) {
 }
 
 // Providers lists providers with a stored key (sorted), for display/audit.
-func (s *Store) Providers() ([]string, error) {
+func (s *Store) Providers() (names []string, err error) {
 	if s.backend == "keyring" {
 		// The OS keyring has no enumerate-by-prefix in our minimal surface; callers
 		// that need a list pass known provider names to Get. Return empty here.
 		return nil, nil
 	}
+	release, err := s.acquireFileLock(false)
+	if err != nil {
+		return nil, err
+	}
+	defer func() { err = errors.Join(err, release()) }()
 	data, err := s.read()
 	if err != nil {
 		return nil, err
 	}
-	names := make([]string, 0, len(data))
+	names = make([]string, 0, len(data))
 	for name := range data {
 		names = append(names, name)
 	}
@@ -264,6 +299,15 @@ func (s *Store) write(data map[string]string) error {
 	return nil
 }
 
+// lockPath is the advisory lock guarding a read-modify-write of the credential
+// file. Beside the data file, never the data file itself — write publishes by
+// rename and would carry the lock away with the old inode.
+func (s *Store) lockPath() string { return s.file + ".lock" }
+
+// filepathDir is filepath.Dir, named locally so the two platform lock files can
+// share it without either importing path/filepath for one call.
+func filepathDir(path string) string { return filepath.Dir(path) }
+
 func normalizeProvider(provider string) string {
 	return strings.ToLower(strings.TrimSpace(provider))
 }

internal/credstore/filelock_unix.go

@@ -0,0 +1,55 @@
+//go:build !windows
+
+package credstore
+
+import (
+	"errors"
+	"fmt"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+// acquireFileLock takes an exclusive advisory lock (flock) so a read-modify-write
+// of the credential file is serialized against every other one — across
+// processes AND across goroutines, since flock is held per open file
+// description and two opens in one process contend exactly as two processes do.
+//
+// THE LOCK FILE IS SEPARATE FROM THE DATA FILE, and that is not tidiness. write
+// publishes by os.Rename, which replaces the inode; a lock taken on the data
+// file would be attached to an inode that the next writer has already replaced,
+// so every writer would appear to hold it. The lock lives on a file nothing
+// renames.
+func (s *Store) acquireFileLock(exclusive bool) (func() error, error) {
+	path := s.lockPath()
+	if err := os.MkdirAll(filepathDir(path), 0o700); err != nil {
+		return nil, fmt.Errorf("credstore: lock dir: %w", err)
+	}
+	file, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0o600)
+	if err != nil {
+		return nil, fmt.Errorf("credstore: open lock: %w", err)
+	}
+	// Writers take LOCK_EX; readers take LOCK_SH so they run concurrently with
+	// each other but still serialize against a writer's publish (see Get).
+	how := unix.LOCK_SH
+	if exclusive {
+		how = unix.LOCK_EX
+	}
+	if err := unix.Flock(int(file.Fd()), how); err != nil {
+		_ = file.Close()
+		return nil, fmt.Errorf("credstore: lock: %w", err)
+	}
+	return func() error {
+		// Close alone drops the flock, so the explicit unlock is belt-and-braces —
+		// but its failure is reported rather than swallowed, because a cleanup that
+		// did not complete must not be indistinguishable from one that did. The
+		// callers join this into their result, so it annotates a successful write
+		// instead of masking it.
+		unlockErr := unix.Flock(int(file.Fd()), unix.LOCK_UN)
+		closeErr := file.Close()
+		if err := errors.Join(unlockErr, closeErr); err != nil {
+			return fmt.Errorf("credstore: release lock: %w", err)
+		}
+		return nil
+	}, nil
+}

internal/credstore/filelock_windows.go

@@ -0,0 +1,55 @@
+//go:build windows
+
+package credstore
+
+import (
+	"errors"
+	"fmt"
+	"os"
+
+	"golang.org/x/sys/windows"
+)
+
+// acquireFileLock takes an exclusive OS lock (LockFileEx) so a read-modify-write
+// of the credential file is serialized, matching the flock behaviour on unix.
+//
+// The lock file is SEPARATE from the data file for the same reason: write
+// publishes by rename, and a lock on the renamed file would be attached to
+// something the next writer has already replaced.
+func (s *Store) acquireFileLock(exclusive bool) (func() error, error) {
+	path := s.lockPath()
+	if err := os.MkdirAll(filepathDir(path), 0o700); err != nil {
+		return nil, fmt.Errorf("credstore: lock dir: %w", err)
+	}
+	file, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0o600)
+	if err != nil {
+		return nil, fmt.Errorf("credstore: open lock: %w", err)
+	}
+	handle := windows.Handle(file.Fd())
+	overlapped := new(windows.Overlapped)
+	// A fixed 1-byte region, blocking (no LOCKFILE_FAIL_IMMEDIATELY) so a
+	// waiter queues rather than failing the operation. Writers pass
+	// LOCKFILE_EXCLUSIVE_LOCK; readers omit it (a shared lock) so they still
+	// serialize against a writer's publish — which matters more on Windows,
+	// where an unsynchronized reader holding the file open blocks the rename.
+	flags := uint32(0)
+	if exclusive {
+		flags = windows.LOCKFILE_EXCLUSIVE_LOCK
+	}
+	if err := windows.LockFileEx(handle, flags, 0, 1, 0, overlapped); err != nil {
+		_ = file.Close()
+		return nil, fmt.Errorf("credstore: lock: %w", err)
+	}
+	return func() error {
+		// Reported rather than swallowed, for the same reason as the unix side: a
+		// cleanup that did not complete must not look identical to one that did.
+		// It matters more here — on Windows the handle staying open is what blocks
+		// the next writer's rename, so a failed release has a visible consequence.
+		unlockErr := windows.UnlockFileEx(handle, 0, 1, 0, overlapped)
+		closeErr := file.Close()
+		if err := errors.Join(unlockErr, closeErr); err != nil {
+			return fmt.Errorf("credstore: release lock: %w", err)
+		}
+		return nil
+	}, nil
+}

internal/dictation/transcriber_deepgram.go

@@ -9,6 +9,7 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/Gitlawb/zero/internal/providers/providerio"
 	"github.com/coder/websocket"
 )
 
@@ -60,7 +61,15 @@ func (d *deepgramTranscriber) StreamTranscribe(ctx context.Context, chunks <-cha
 		HTTPHeader: http.Header{"Authorization": {"Token " + d.cfg.APIKey}},
 	})
 	if err != nil {
-		return "", fmt.Errorf("connecting to Deepgram: %w", err)
+		// Preserve the context.Canceled sentinel (it carries no key) so an
+		// Esc-abort during dial still matches the UI's errors.Is check. Key
+		// on ctx.Err() itself rather than unwrapping err: a cancellation can
+		// surface as a plain transport error (e.g. "closed network
+		// connection") rather than context.Canceled directly.
+		if ctx.Err() != nil {
+			return "", ctx.Err()
+		}
+		return "", fmt.Errorf("connecting to Deepgram: %s", providerio.Redact(err.Error(), d.cfg.APIKey))
 	}
 	defer conn.CloseNow()
 
@@ -68,15 +77,26 @@ func (d *deepgramTranscriber) StreamTranscribe(ctx context.Context, chunks <-cha
 	// so no conversion (unlike sherpa-onnx, which wants float32).
 	writeErrCh := make(chan error, 1)
 	go func() {
-		for chunk := range chunks {
-			if err := conn.Write(ctx, websocket.MessageBinary, chunk); err != nil {
-				writeErrCh <- err
+		// Select on ctx.Done() while waiting for the next chunk so a cancelled
+		// session does not leave this goroutine blocked on an open idle channel.
+		for {
+			select {
+			case <-ctx.Done():
+				writeErrCh <- ctx.Err()
 				return
+			case chunk, ok := <-chunks:
+				if !ok {
+					// CloseStream flushes any buffered audio and returns final
+					// results before Deepgram closes the socket.
+					writeErrCh <- conn.Write(ctx, websocket.MessageText, []byte(`{"type":"CloseStream"}`))
+					return
+				}
+				if err := conn.Write(ctx, websocket.MessageBinary, chunk); err != nil {
+					writeErrCh <- err
+					return
+				}
 			}
 		}
-		// CloseStream flushes any buffered audio and returns final results before
-		// Deepgram closes the socket.
-		writeErrCh <- conn.Write(ctx, websocket.MessageText, []byte(`{"type":"CloseStream"}`))
 	}()
 
 	// Deepgram results are per-utterance segments, not cumulative: accumulate the
@@ -100,7 +120,18 @@ func (d *deepgramTranscriber) StreamTranscribe(ctx context.Context, chunks <-cha
 				}
 			default:
 			}
-			return compose(), fmt.Errorf("Deepgram stream error: %w", err) //nolint:staticcheck // Preserve established user-facing error text.
+			// A user abort cancels the streaming context; the UI matches it
+			// with errors.Is(err, context.Canceled), so return the sentinel
+			// itself (it carries no key) instead of a flat redacted string.
+			// Key on ctx.Err() rather than unwrapping err: the writeErrCh
+			// swap above can replace err with a plain transport error (e.g.
+			// "closed network connection") that doesn't itself unwrap to
+			// context.Canceled even though the cancellation is what caused it.
+			if ctx.Err() != nil {
+				return compose(), ctx.Err()
+			}
+			//nolint:staticcheck // Preserve established user-facing error text.
+			return compose(), fmt.Errorf("Deepgram stream error: %s", providerio.Redact(err.Error(), d.cfg.APIKey))
 		}
 		if typ != websocket.MessageText {
 			continue

internal/dictation/transcriber_deepgram_test.go

@@ -0,0 +1,278 @@
+package dictation
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+
+	"github.com/coder/websocket"
+)
+
+// Non-cancellation dial failure: handshake returns 101 with an Upgrade header
+// equal to the API key so the dial error embeds the key and redaction must strip it.
+func TestDeepgramDialFailureRedactsKey(t *testing.T) {
+	const key = "sk-test-dial-key-abcdef"
+	baseURL := dialFailServerWithUpgrade(t, key)
+
+	tr, err := NewDeepgramTranscriber(DeepgramConfig{APIKey: key, BaseURL: baseURL})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	chunks := make(chan []byte)
+	close(chunks)
+	_, ferr := tr.StreamTranscribe(context.Background(), chunks, nil)
+	if ferr == nil {
+		t.Fatal("expected dial failure")
+	}
+	if errors.Is(ferr, context.Canceled) {
+		t.Fatalf("dial failure should not be context.Canceled: %v", ferr)
+	}
+	if strings.Contains(ferr.Error(), key) {
+		t.Errorf("API key leaked from dial failure: %v", ferr)
+	}
+	if !strings.Contains(ferr.Error(), "connecting to Deepgram") {
+		t.Errorf("expected dial-path error prefix, got: %v", ferr)
+	}
+}
+
+// dialFailServerWithUpgrade returns a ws URL whose handshake responds 101 with
+// Upgrade set to upgradeValue (not "websocket"), so websocket.Dial fails with
+// that value in the error string. Hijacks and closes immediately to avoid the
+// library's 3s body-drain timeout on failed dials.
+func dialFailServerWithUpgrade(t *testing.T, upgradeValue string) string {
+	t.Helper()
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		hj, ok := w.(http.Hijacker)
+		if !ok {
+			http.Error(w, "hijack not supported", http.StatusInternalServerError)
+			return
+		}
+		conn, bufrw, err := hj.Hijack()
+		if err != nil {
+			return
+		}
+		defer conn.Close()
+		_, _ = bufrw.WriteString("HTTP/1.1 101 Switching Protocols\r\n")
+		_, _ = bufrw.WriteString("Connection: Upgrade\r\n")
+		_, _ = bufrw.WriteString("Upgrade: " + upgradeValue + "\r\n\r\n")
+		_ = bufrw.Flush()
+	}))
+	t.Cleanup(srv.Close)
+	return "ws" + strings.TrimPrefix(srv.URL, "http")
+}
+
+func TestDeepgramStreamTranscribeErrorRedaction(t *testing.T) {
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		// Drain the client's audio frames, then wait for CloseStream so the
+		// client has flushed its writes before we reject the connection. Closing
+		// immediately (before CloseStream) risks the client failing on a write
+		// error and never observing this API-key-bearing close reason.
+		for {
+			typ, data, err := c.Read(ctx)
+			if err != nil {
+				return
+			}
+			if typ == websocket.MessageText && strings.Contains(string(data), "CloseStream") {
+				break
+			}
+		}
+		c.Close(websocket.StatusPolicyViolation, "invalid key sk-test-key")
+	})
+
+	tr, err := NewDeepgramTranscriber(DeepgramConfig{APIKey: "sk-test-key", BaseURL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	chunks := make(chan []byte, 1)
+	chunks <- make([]byte, 320)
+	close(chunks)
+	_, ferr := tr.StreamTranscribe(context.Background(), chunks, func(string, bool) {})
+	if ferr == nil {
+		t.Fatal("expected error")
+	}
+	if strings.Contains(ferr.Error(), "sk-test-key") {
+		t.Errorf("API key leaked: %v", ferr)
+	}
+}
+
+func TestDeepgramStreamTranscribeCancelKeepsSentinel(t *testing.T) {
+	firstFrame := make(chan struct{})
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		// Hold the connection open, never answering, so the client blocks in
+		// Read until its context is cancelled (the Esc-abort path).
+		var once sync.Once
+		for {
+			if _, _, err := c.Read(ctx); err != nil {
+				return
+			}
+			once.Do(func() { close(firstFrame) })
+		}
+	})
+
+	tr, err := NewDeepgramTranscriber(DeepgramConfig{APIKey: "sk-test-key", BaseURL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	chunks := make(chan []byte, 1)
+	defer close(chunks)
+	chunks <- make([]byte, 320)
+	// The channel stays open: the session is live when the user aborts.
+	errCh := make(chan error, 1)
+	go func() {
+		_, ferr := tr.StreamTranscribe(ctx, chunks, nil)
+		errCh <- ferr
+	}()
+
+	select {
+	case <-firstFrame:
+		cancel()
+		ferr := <-errCh
+		if !errors.Is(ferr, context.Canceled) {
+			t.Fatalf("cancelled stream error lost the context.Canceled sentinel: %v", ferr)
+		}
+	case ferr := <-errCh:
+		t.Fatalf("StreamTranscribe failed early instead of blocking: %v", ferr)
+	}
+}
+
+// Esc can cancel while the WebSocket dial is still pending. The dial error is
+// redacted with %s, so we must return ctx.Err() rather than a flat string.
+func TestDeepgramStreamTranscribeDialCancelKeepsSentinel(t *testing.T) {
+	tr, err := NewDeepgramTranscriber(DeepgramConfig{
+		APIKey:  "sk-test-key",
+		BaseURL: "ws://127.0.0.1:1", // never reached; ctx is already cancelled
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	chunks := make(chan []byte)
+	defer close(chunks)
+
+	_, ferr := tr.StreamTranscribe(ctx, chunks, nil)
+	if !errors.Is(ferr, context.Canceled) {
+		t.Fatalf("dial-cancel lost the context.Canceled sentinel: %v", ferr)
+	}
+}
+
+// Esc right after accept can race the first write or the first Read; both
+// setup/write redaction sites must still yield context.Canceled.
+func TestDeepgramStreamTranscribeStartupCancelKeepsSentinel(t *testing.T) {
+	accepted := make(chan struct{})
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		close(accepted)
+		for {
+			if _, _, err := c.Read(ctx); err != nil {
+				return
+			}
+		}
+	})
+
+	tr, err := NewDeepgramTranscriber(DeepgramConfig{APIKey: "sk-test-key", BaseURL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	chunks := make(chan []byte, 1)
+	defer close(chunks)
+	// No frames yet: the writer blocks on chunks or the reader blocks on Read.
+	errCh := make(chan error, 1)
+	go func() {
+		_, ferr := tr.StreamTranscribe(ctx, chunks, nil)
+		errCh <- ferr
+	}()
+
+	select {
+	case <-accepted:
+		cancel()
+		ferr := <-errCh
+		if !errors.Is(ferr, context.Canceled) {
+			t.Fatalf("startup-cancel lost the context.Canceled sentinel: %v", ferr)
+		}
+	case ferr := <-errCh:
+		t.Fatalf("StreamTranscribe failed before accept: %v", ferr)
+	}
+}
+
+// TestDeepgramStreamErrorRedactsHeaderShapedKey exercises the same stream-error
+// redaction path as TestDeepgramStreamTranscribeErrorRedaction, with a close
+// reason that embeds the key next to an X-Api-Key-shaped header label.
+func TestDeepgramStreamErrorRedactsHeaderShapedKey(t *testing.T) {
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		for {
+			typ, data, err := c.Read(ctx)
+			if err != nil {
+				return
+			}
+			if typ == websocket.MessageText && strings.Contains(string(data), "CloseStream") {
+				break
+			}
+		}
+		c.Close(websocket.StatusPolicyViolation, "X-Api-Key: sk-custom-secret-key-1234567890 failed")
+	})
+
+	tr, err := NewDeepgramTranscriber(DeepgramConfig{APIKey: "sk-custom-secret-key-1234567890", BaseURL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	chunks := make(chan []byte, 1)
+	chunks <- make([]byte, 320)
+	close(chunks)
+	_, ferr := tr.StreamTranscribe(context.Background(), chunks, func(string, bool) {})
+	if ferr == nil {
+		t.Fatal("expected error")
+	}
+	if strings.Contains(ferr.Error(), "sk-custom-secret-key-1234567890") {
+		t.Errorf("Custom header API key leaked: %v", ferr)
+	}
+}
+
+func TestDeepgramSinglePassRedaction(t *testing.T) {
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		for {
+			typ, data, err := c.Read(ctx)
+			if err != nil {
+				return
+			}
+			if typ == websocket.MessageText && strings.Contains(string(data), "CloseStream") {
+				break
+			}
+		}
+		c.Close(websocket.StatusPolicyViolation, "error with sk-key1234567890abcdef1234")
+	})
+
+	tr, err := NewDeepgramTranscriber(DeepgramConfig{APIKey: "sk-key1234567890abcdef1234", BaseURL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	chunks := make(chan []byte, 1)
+	chunks <- make([]byte, 320)
+	close(chunks)
+	_, ferr := tr.StreamTranscribe(context.Background(), chunks, func(string, bool) {})
+	if ferr == nil {
+		t.Fatal("expected error")
+	}
+	got := ferr.Error()
+	if strings.Contains(got, "sk-key1234567890abcdef1234") {
+		t.Fatalf("API key leaked into stream error: %q", got)
+	}
+	// One key occurrence must produce exactly one redaction marker (no double wrap).
+	if strings.Count(got, "[REDACTED]") != 1 {
+		t.Fatalf("redaction markers in %q: want exactly 1 [REDACTED]", got)
+	}
+}

internal/dictation/transcriber_openai_realtime.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 	"strings"
 
+	"github.com/Gitlawb/zero/internal/providers/providerio"
 	"github.com/coder/websocket"
 )
 
@@ -22,6 +23,10 @@ type OpenAIRealtimeConfig struct {
 	Model  string // default "gpt-4o-transcribe"
 	// BaseURL overrides the wss endpoint (tests point it at a fake server).
 	BaseURL string
+	// writeErrInjector, when set, is consulted before each JSON websocket write.
+	// Used by same-package tests to force controllable write failures that embed
+	// secrets; production callers leave it nil.
+	writeErrInjector func() error
 }
 
 type openAIRealtimeTranscriber struct {
@@ -59,7 +64,15 @@ func (o *openAIRealtimeTranscriber) StreamTranscribe(ctx context.Context, chunks
 		},
 	})
 	if err != nil {
-		return "", fmt.Errorf("connecting to OpenAI Realtime: %w", err)
+		// Preserve the context.Canceled sentinel (it carries no key) so an
+		// Esc-abort during dial still matches the UI's errors.Is check. Key
+		// on ctx.Err() itself rather than unwrapping err: a cancellation can
+		// surface as a plain transport error (e.g. "closed network
+		// connection") rather than context.Canceled directly.
+		if ctx.Err() != nil {
+			return "", ctx.Err()
+		}
+		return "", fmt.Errorf("connecting to OpenAI Realtime: %s", providerio.Redact(err.Error(), o.cfg.APIKey))
 	}
 	defer conn.CloseNow()
 
@@ -73,24 +86,53 @@ func (o *openAIRealtimeTranscriber) StreamTranscribe(ctx context.Context, chunks
 			},
 		},
 	}
-	if err := writeJSON(ctx, conn, sessionUpdate); err != nil {
-		return "", fmt.Errorf("configuring OpenAI Realtime session: %w", err)
+	if err := o.writeJSON(ctx, conn, sessionUpdate); err != nil {
+		// Same cancellation short-circuit as the dial above: an Esc-abort
+		// while the session update is in flight must stay context.Canceled.
+		if ctx.Err() != nil {
+			return "", ctx.Err()
+		}
+		return "", fmt.Errorf("configuring OpenAI Realtime session: %s", providerio.Redact(err.Error(), o.cfg.APIKey))
 	}
 
 	writeErrCh := make(chan error, 1)
 	go func() {
-		for chunk := range chunks {
-			appendMsg := map[string]any{
-				"type":  "input_audio_buffer.append",
-				"audio": base64.StdEncoding.EncodeToString(chunk),
-			}
-			if err := writeJSON(ctx, conn, appendMsg); err != nil {
-				writeErrCh <- err
+		// Select on ctx.Done() while waiting for the next chunk so a cancelled
+		// session does not leave this goroutine blocked on an open idle channel.
+		for {
+			select {
+			case <-ctx.Done():
+				writeErrCh <- ctx.Err()
 				return
+			case chunk, ok := <-chunks:
+				if !ok {
+					// Commit the buffered audio to force final transcription.
+					if err := o.writeJSON(ctx, conn, map[string]any{"type": "input_audio_buffer.commit"}); err != nil {
+						writeErrCh <- err
+						// Unblock the reader: without a close, conn.Read stays
+						// parked on a silent peer and the error is never drained
+						// from writeErrCh. CloseNow aborts instead of waiting on
+						// the close handshake, which a silent peer never answers.
+						conn.CloseNow()
+						return
+					}
+					writeErrCh <- nil
+					return
+				}
+				appendMsg := map[string]any{
+					"type":  "input_audio_buffer.append",
+					"audio": base64.StdEncoding.EncodeToString(chunk),
+				}
+				if err := o.writeJSON(ctx, conn, appendMsg); err != nil {
+					writeErrCh <- err
+					// Same unblocking close as the commit path: a server that
+					// goes silent after session setup would otherwise leave the
+					// reader blocked in conn.Read with the error undrained.
+					conn.CloseNow()
+					return
+				}
 			}
 		}
-		// Commit the buffered audio to force final transcription of the utterance.
-		writeErrCh <- writeJSON(ctx, conn, map[string]any{"type": "input_audio_buffer.commit"})
 	}()
 
 	// OpenAI deltas are incremental (append), unlike Deepgram/sherpa's cumulative
@@ -113,7 +155,17 @@ func (o *openAIRealtimeTranscriber) StreamTranscribe(ctx context.Context, chunks
 				}
 			default:
 			}
-			return compose(), fmt.Errorf("OpenAI Realtime stream error: %w", err)
+			// A user abort cancels the streaming context; the UI matches it
+			// with errors.Is(err, context.Canceled), so return the sentinel
+			// itself (it carries no key) instead of a flat redacted string.
+			// Key on ctx.Err() rather than unwrapping err: the writeErrCh
+			// swap above can replace err with a plain transport error (e.g.
+			// "closed network connection") that doesn't itself unwrap to
+			// context.Canceled even though the cancellation is what caused it.
+			if ctx.Err() != nil {
+				return compose(), ctx.Err()
+			}
+			return compose(), fmt.Errorf("OpenAI Realtime stream error: %s", providerio.Redact(err.Error(), o.cfg.APIKey))
 		}
 		if typ != websocket.MessageText {
 			continue
@@ -125,6 +177,12 @@ func (o *openAIRealtimeTranscriber) StreamTranscribe(ctx context.Context, chunks
 			if onPartial != nil {
 				onPartial(compose(), false)
 			}
+			// onPartial may deliver the partial that makes the TUI cancel
+			// (Esc). Observe that before the next Read, which can already
+			// have a racing OpenAI error frame buffered.
+			if ctx.Err() != nil {
+				return compose(), ctx.Err()
+			}
 		case realtimeCompleted:
 			// A completed item replaces the in-progress delta buffer with the
 			// server's authoritative transcript for that segment.
@@ -138,6 +196,9 @@ func (o *openAIRealtimeTranscriber) StreamTranscribe(ctx context.Context, chunks
 			if onPartial != nil {
 				onPartial(compose(), true)
 			}
+			if ctx.Err() != nil {
+				return compose(), ctx.Err()
+			}
 			// Once we've committed the buffer (user stopped) and the server has
 			// returned a completed transcription, the utterance is done.
 			if committed {
@@ -147,7 +208,15 @@ func (o *openAIRealtimeTranscriber) StreamTranscribe(ctx context.Context, chunks
 		case realtimeCommitted:
 			committed = true
 		case realtimeError:
-			return compose(), fmt.Errorf("OpenAI Realtime error: %s", evt.text)
+			// Esc can race an incoming error event: conn.Read may already have
+			// the OpenAI error in hand by the time cancellation lands. Key on
+			// ctx.Err() first, same as every other return point in this loop,
+			// so a cancel that wins the race still surfaces as context.Canceled
+			// instead of a spurious redacted failure alongside it.
+			if ctx.Err() != nil {
+				return compose(), ctx.Err()
+			}
+			return compose(), fmt.Errorf("OpenAI Realtime error: %s", providerio.Redact(evt.text, o.cfg.APIKey))
 		}
 		// The writer signals commit completion out of band; observe it so a
 		// stop with no further audio still flips `committed`.
@@ -155,6 +224,10 @@ func (o *openAIRealtimeTranscriber) StreamTranscribe(ctx context.Context, chunks
 		case werr := <-writeErrCh:
 			if werr == nil {
 				committed = true
+			} else if ctx.Err() != nil {
+				return compose(), ctx.Err()
+			} else {
+				return compose(), fmt.Errorf("OpenAI Realtime stream error: %s", providerio.Redact(werr.Error(), o.cfg.APIKey))
 			}
 		default:
 		}
@@ -201,6 +274,15 @@ func parseRealtimeEvent(data []byte) realtimeEvent {
 	return realtimeEvent{kind: realtimeOther}
 }
 
+func (o *openAIRealtimeTranscriber) writeJSON(ctx context.Context, conn *websocket.Conn, v any) error {
+	if o.cfg.writeErrInjector != nil {
+		if err := o.cfg.writeErrInjector(); err != nil {
+			return err
+		}
+	}
+	return writeJSON(ctx, conn, v)
+}
+
 func writeJSON(ctx context.Context, conn *websocket.Conn, v any) error {
 	data, err := json.Marshal(v)
 	if err != nil {

internal/dictation/transcriber_openai_realtime_test.go

@@ -0,0 +1,437 @@
+package dictation
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/coder/websocket"
+)
+
+// Non-cancellation dial failure: handshake returns 101 with an Upgrade header
+// equal to the API key so the dial error embeds the key and redaction must strip it.
+func TestOpenAIRealtimeDialFailureRedactsKey(t *testing.T) {
+	const key = "sk-test-dial-key-abcdef"
+	baseURL := dialFailServerWithUpgrade(t, key)
+
+	tr, err := NewOpenAIRealtimeTranscriber(OpenAIRealtimeConfig{APIKey: key, BaseURL: baseURL})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	chunks := make(chan []byte)
+	close(chunks)
+	_, ferr := tr.StreamTranscribe(context.Background(), chunks, nil)
+	if ferr == nil {
+		t.Fatal("expected dial failure")
+	}
+	if errors.Is(ferr, context.Canceled) {
+		t.Fatalf("dial failure should not be context.Canceled: %v", ferr)
+	}
+	if strings.Contains(ferr.Error(), key) {
+		t.Errorf("API key leaked from dial failure: %v", ferr)
+	}
+	if !strings.Contains(ferr.Error(), "connecting to OpenAI Realtime") {
+		t.Errorf("expected dial-path error prefix, got: %v", ferr)
+	}
+}
+
+// Session-configuration write fails after dial: inject a write error that embeds
+// the API key (peer close cannot reach this path reliably — the session write
+// always lands in the kernel buffer first) and assert redaction.
+func TestOpenAIRealtimeSessionConfigFailureRedactsKey(t *testing.T) {
+	const key = "sk-test-session-key-abcdef"
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		// Hold open; the client fails on the injected session write before reading.
+		<-ctx.Done()
+	})
+
+	tr, err := NewOpenAIRealtimeTranscriber(OpenAIRealtimeConfig{
+		APIKey:  key,
+		BaseURL: url,
+		writeErrInjector: func() error {
+			return errors.New("invalid API key " + key)
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	chunks := make(chan []byte)
+	close(chunks)
+	_, ferr := tr.StreamTranscribe(context.Background(), chunks, nil)
+	if ferr == nil {
+		t.Fatal("expected session-config failure")
+	}
+	if errors.Is(ferr, context.Canceled) {
+		t.Fatalf("session-config failure should not be context.Canceled: %v", ferr)
+	}
+	if strings.Contains(ferr.Error(), key) {
+		t.Errorf("API key leaked from session-config failure: %v", ferr)
+	}
+	if !strings.Contains(ferr.Error(), "configuring OpenAI Realtime session") {
+		t.Errorf("expected session-config error prefix, got: %v", ferr)
+	}
+}
+
+// Asynchronous writer failure: session update succeeds, then the audio writer
+// injects a key-bearing write error. The server keeps the connection open and
+// emits a delta so the reader loop observes writeErrCh (not a peer close).
+func TestOpenAIRealtimeWriterFailureRedactsKey(t *testing.T) {
+	const key = "sk-test-writer-key-abcdef"
+	sessionDone := make(chan struct{})
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		if _, _, err := c.Read(ctx); err != nil {
+			return
+		}
+		close(sessionDone)
+		// Keep reading and emit a delta so the client processes an event and
+		// drains writeErrCh while the connection is still open.
+		_ = c.Write(ctx, websocket.MessageText, []byte(
+			`{"type":"conversation.item.input_audio_transcription.delta","delta":"hi"}`,
+		))
+		for {
+			if _, _, err := c.Read(ctx); err != nil {
+				return
+			}
+		}
+	})
+
+	var writes atomic.Int32
+	tr, err := NewOpenAIRealtimeTranscriber(OpenAIRealtimeConfig{
+		APIKey:  key,
+		BaseURL: url,
+		writeErrInjector: func() error {
+			// First write is session.update; fail subsequent audio/commit writes.
+			if writes.Add(1) == 1 {
+				return nil
+			}
+			return errors.New("invalid API key " + key)
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	chunks := make(chan []byte, 1)
+	chunks <- make([]byte, 480)
+	// Leave open after the first frame so the writer hits the injected error
+	// on that append rather than a clean commit.
+
+	done := make(chan error, 1)
+	go func() {
+		_, ferr := tr.StreamTranscribe(context.Background(), chunks, func(string, bool) {})
+		done <- ferr
+	}()
+
+	var ferr error
+	select {
+	case ferr = <-done:
+	case <-time.After(5 * time.Second):
+		close(chunks)
+		t.Fatal("StreamTranscribe did not complete after writer failure")
+	}
+	close(chunks)
+
+	if ferr == nil {
+		t.Fatal("expected writer failure")
+	}
+	if errors.Is(ferr, context.Canceled) {
+		t.Fatalf("writer failure should not be context.Canceled: %v", ferr)
+	}
+	if strings.Contains(ferr.Error(), key) {
+		t.Errorf("API key leaked from writer failure: %v", ferr)
+	}
+	if !strings.Contains(ferr.Error(), "OpenAI Realtime stream error") {
+		t.Errorf("expected stream/writer error prefix, got: %v", ferr)
+	}
+	select {
+	case <-sessionDone:
+	default:
+		// Session may race the injected audio write; prefix assertion above is enough.
+	}
+}
+
+// Writer failure with a silent server: the peer never sends a frame after
+// session setup, so the reader is parked in conn.Read. The writer must close
+// the connection on failure or the writeErrCh error is never observed and
+// StreamTranscribe blocks forever.
+func TestOpenAIRealtimeWriterFailureUnblocksSilentServer(t *testing.T) {
+	const key = "sk-test-silent-writer-key-abcdef"
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		// Hold the connection open without ever writing a frame.
+		<-ctx.Done()
+	})
+
+	var writes atomic.Int32
+	tr, err := NewOpenAIRealtimeTranscriber(OpenAIRealtimeConfig{
+		APIKey:  key,
+		BaseURL: url,
+		writeErrInjector: func() error {
+			// First write is session.update; fail the subsequent append write.
+			if writes.Add(1) == 1 {
+				return nil
+			}
+			return errors.New("invalid API key " + key)
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	chunks := make(chan []byte, 1)
+	chunks <- make([]byte, 480)
+	// Leave the channel open: the writer must fail on the append, not the commit.
+	done := make(chan error, 1)
+	go func() {
+		_, ferr := tr.StreamTranscribe(ctx, chunks, func(string, bool) {})
+		done <- ferr
+	}()
+
+	select {
+	case ferr := <-done:
+		if ferr == nil {
+			t.Fatal("expected writer failure")
+		}
+		if errors.Is(ferr, context.Canceled) {
+			t.Fatalf("writer failure should not be context.Canceled: %v", ferr)
+		}
+		if strings.Contains(ferr.Error(), key) {
+			t.Errorf("API key leaked from writer failure: %v", ferr)
+		}
+		if !strings.Contains(ferr.Error(), "OpenAI Realtime stream error") {
+			t.Errorf("expected stream/writer error prefix, got: %v", ferr)
+		}
+	case <-time.After(5 * time.Second):
+		close(chunks)
+		t.Fatal("StreamTranscribe did not unblock after writer failure with a silent server")
+	}
+}
+
+func TestOpenAIRealtimeStreamTranscribeErrorRedaction(t *testing.T) {
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		defer c.Close(websocket.StatusNormalClosure, "")
+		for {
+			typ, _, err := c.Read(ctx)
+			if err != nil {
+				return
+			}
+			if typ != websocket.MessageText {
+				continue
+			}
+			_ = c.Write(ctx, websocket.MessageText, []byte(`{"type":"error","error":{"message":"invalid API key sk-test-key"}}`))
+		}
+	})
+
+	tr, err := NewOpenAIRealtimeTranscriber(OpenAIRealtimeConfig{APIKey: "sk-test-key", BaseURL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	chunks := make(chan []byte, 1)
+	chunks <- make([]byte, 480)
+	close(chunks)
+	_, ferr := tr.StreamTranscribe(context.Background(), chunks, func(string, bool) {})
+	if ferr == nil {
+		t.Fatal("expected error")
+	}
+	if strings.Contains(ferr.Error(), "sk-test-key") {
+		t.Errorf("API key leaked: %v", ferr)
+	}
+}
+
+func TestOpenAIRealtimeStreamTranscribeCancelKeepsSentinel(t *testing.T) {
+	firstFrame := make(chan struct{})
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		// Hold the connection open, never answering, so the client blocks in
+		// Read until its context is cancelled (the Esc-abort path).
+		var once sync.Once
+		for {
+			if _, _, err := c.Read(ctx); err != nil {
+				return
+			}
+			once.Do(func() { close(firstFrame) })
+		}
+	})
+
+	tr, err := NewOpenAIRealtimeTranscriber(OpenAIRealtimeConfig{APIKey: "sk-test-key", BaseURL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	chunks := make(chan []byte, 1)
+	defer close(chunks)
+	chunks <- make([]byte, 480)
+	// The channel stays open: the session is live when the user aborts.
+	errCh := make(chan error, 1)
+	go func() {
+		_, ferr := tr.StreamTranscribe(ctx, chunks, nil)
+		errCh <- ferr
+	}()
+
+	select {
+	case <-firstFrame:
+		cancel()
+		ferr := <-errCh
+		if !errors.Is(ferr, context.Canceled) {
+			t.Fatalf("cancelled stream error lost the context.Canceled sentinel: %v", ferr)
+		}
+	case ferr := <-errCh:
+		t.Fatalf("StreamTranscribe failed early instead of blocking: %v", ferr)
+	}
+}
+
+// Esc can cancel while the WebSocket dial is still pending. The dial error is
+// redacted with %s, so we must return ctx.Err() rather than a flat string.
+func TestOpenAIRealtimeStreamTranscribeDialCancelKeepsSentinel(t *testing.T) {
+	tr, err := NewOpenAIRealtimeTranscriber(OpenAIRealtimeConfig{
+		APIKey:  "sk-test-key",
+		BaseURL: "ws://127.0.0.1:1", // never reached; ctx is already cancelled
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	chunks := make(chan []byte)
+	defer close(chunks)
+
+	_, ferr := tr.StreamTranscribe(ctx, chunks, nil)
+	if !errors.Is(ferr, context.Canceled) {
+		t.Fatalf("dial-cancel lost the context.Canceled sentinel: %v", ferr)
+	}
+}
+
+// Esc right after accept can hit the session-update write or the first Read;
+// both redaction sites must still yield context.Canceled.
+func TestOpenAIRealtimeStreamTranscribeStartupCancelKeepsSentinel(t *testing.T) {
+	accepted := make(chan struct{})
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		close(accepted)
+		// Do not read: leave the client in session-update write or first Read.
+		<-ctx.Done()
+	})
+
+	tr, err := NewOpenAIRealtimeTranscriber(OpenAIRealtimeConfig{APIKey: "sk-test-key", BaseURL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	chunks := make(chan []byte, 1)
+	defer close(chunks)
+	errCh := make(chan error, 1)
+	go func() {
+		_, ferr := tr.StreamTranscribe(ctx, chunks, nil)
+		errCh <- ferr
+	}()
+
+	select {
+	case <-accepted:
+		cancel()
+		ferr := <-errCh
+		if !errors.Is(ferr, context.Canceled) {
+			t.Fatalf("startup-cancel lost the context.Canceled sentinel: %v", ferr)
+		}
+	case ferr := <-errCh:
+		t.Fatalf("StreamTranscribe failed before accept: %v", ferr)
+	}
+}
+
+// Cancel while the writer is blocked on more chunks. Whichever path observes
+// the cancellation first (the blocked conn.Read or the writeErrCh drain) must
+// return context.Canceled rather than a redacted flat string.
+func TestOpenAIRealtimeStreamTranscribeWriteCancelKeepsSentinel(t *testing.T) {
+	sessionReceived := make(chan struct{})
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		if _, _, err := c.Read(ctx); err != nil {
+			return
+		}
+		close(sessionReceived)
+		for {
+			if _, _, err := c.Read(ctx); err != nil {
+				return
+			}
+		}
+	})
+
+	tr, err := NewOpenAIRealtimeTranscriber(OpenAIRealtimeConfig{APIKey: "sk-test-key", BaseURL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	chunks := make(chan []byte, 1)
+	chunks <- make([]byte, 480)
+	defer close(chunks)
+
+	errCh := make(chan error, 1)
+	go func() {
+		_, ferr := tr.StreamTranscribe(ctx, chunks, nil)
+		errCh <- ferr
+	}()
+
+	select {
+	case <-sessionReceived:
+		cancel()
+		ferr := <-errCh
+		if !errors.Is(ferr, context.Canceled) {
+			t.Fatalf("write-path cancel lost the context.Canceled sentinel: %v", ferr)
+		}
+	case ferr := <-errCh:
+		t.Fatalf("StreamTranscribe failed early instead of blocking: %v", ferr)
+	}
+}
+
+// Esc can race an incoming OpenAI error event. conn.Read may already have
+// the error frame in hand by the time the cancellation lands. The server
+// fires a delta immediately followed by the error, back to back. Cancel from
+// inside the delta callback (same path the TUI uses when a partial triggers
+// Esc handling) so the cancel is observed before the next event is processed.
+// The returned error must still be context.Canceled, not the redacted OpenAI
+// error.
+func TestOpenAIRealtimeStreamTranscribeErrorRaceKeepsSentinel(t *testing.T) {
+	url := wsTestServer(t, func(ctx context.Context, c *websocket.Conn) {
+		if _, _, err := c.Read(ctx); err != nil {
+			return
+		}
+		_ = c.Write(ctx, websocket.MessageText, []byte(
+			`{"type":"conversation.item.input_audio_transcription.delta","delta":"hi"}`,
+		))
+		_ = c.Write(ctx, websocket.MessageText, []byte(
+			`{"type":"error","error":{"message":"invalid API key sk-test-key"}}`,
+		))
+		<-ctx.Done()
+	})
+
+	tr, err := NewOpenAIRealtimeTranscriber(OpenAIRealtimeConfig{APIKey: "sk-test-key", BaseURL: url})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	chunks := make(chan []byte, 1)
+	defer close(chunks)
+	chunks <- make([]byte, 480)
+	var once sync.Once
+	_, ferr := tr.StreamTranscribe(ctx, chunks, func(string, bool) {
+		// Cancel synchronously from the partial callback, before the
+		// stream loop continues to the already-buffered error frame.
+		once.Do(cancel)
+	})
+	if !errors.Is(ferr, context.Canceled) {
+		t.Fatalf("StreamTranscribe error = %v, want context.Canceled (cancel must win over a racing OpenAI error event)", ferr)
+	}
+}

internal/execution/contracts.go

@@ -9,7 +9,16 @@ import (
 	"strings"
 )
 
-const PolicyVersion = 1
+// PolicyVersion is the version of the approval policy that recorded grants were
+// evaluated under. Bump it whenever a change narrows what may be approved: the
+// grant store then backs the file up, keeps deny grants, invalidates prior
+// approvals, and tells the user once, instead of silently honoring approvals
+// that the current rules would have refused.
+//
+// v2 tightened command-prefix validation so a launcher spelled with a version
+// or an executable extension ("python3.11", "python.exe") can no longer be
+// approved as an ordinary command.
+const PolicyVersion = 2
 
 type Origin string
 

internal/execution/process_unix.go

@@ -6,6 +6,8 @@ import (
 	"errors"
 	"fmt"
 	"os/exec"
+	"strconv"
+	"strings"
 	"syscall"
 	"time"
 )
@@ -38,12 +40,45 @@ func KillProcessTree(pid int) error {
 // TerminateProcessTree requests graceful termination, then force-kills the
 // process tree after grace. Callers retain their distinct persistence models;
 // this function owns only the OS lifecycle primitive.
+//
+// The signal target is REDISCOVERED here via processSignalTarget(pid), which
+// asks the OS for pid's current group. A caller that already knows pid was
+// configured as its own group leader at launch (e.g. via ConfigureProcessGroup)
+// should use TerminateProcessGroup instead — see its doc comment for why this
+// rediscovery is fragile once the leader may have already exited.
 func TerminateProcessTree(pid int, grace, poll time.Duration) error {
 	target, err := processSignalTarget(pid)
 	if err != nil {
 		return err
 	}
-	alive := func() bool { return syscall.Kill(target, syscall.Signal(0)) == nil }
+	return terminateTarget(pid, target, grace, poll)
+}
+
+// TerminateProcessGroup is like TerminateProcessTree, but for a caller that
+// already knows pid is (or was, at launch) its own process-group leader — e.g.
+// a command started after ConfigureProcessGroup(cmd), which sets Setpgid so
+// cmd.Process.Pid always leads its own group at the moment it is signalled.
+//
+// TerminateProcessTree instead rediscovers the group via syscall.Getpgid(pid)
+// at call time. On Darwin, that lookup can return ESRCH once an unreaped group
+// leader has already exited, even though live descendants remain in the group
+// it configured — TerminateProcessTree would then silently fall back to
+// signalling only the (already dead) leader PID and leave those descendants
+// running. Skipping rediscovery in favor of the launch-time invariant avoids
+// that: the negative PID is used directly, regardless of whether the leader is
+// still alive to be looked up.
+func TerminateProcessGroup(pid int, grace, poll time.Duration) error {
+	if pid <= 1 {
+		return fmt.Errorf("refusing to signal invalid pid %d", pid)
+	}
+	return terminateTarget(pid, -pid, grace, poll)
+}
+
+// terminateTarget signals target (an individual PID or, negative, a process
+// group) with SIGTERM then, after grace, SIGKILL. reportPid identifies the
+// original process in error messages regardless of which form target takes.
+func terminateTarget(reportPid, target int, grace, poll time.Duration) error {
+	alive := func() bool { return signalTargetRunning(target) }
 	if err := syscall.Kill(target, syscall.SIGTERM); err != nil {
 		if errors.Is(err, syscall.ESRCH) {
 			return nil
@@ -77,11 +112,91 @@ func TerminateProcessTree(pid int, grace, poll time.Duration) error {
 		time.Sleep(poll)
 	}
 	if alive() {
-		return fmt.Errorf("process %d did not exit after SIGKILL", pid)
+		return fmt.Errorf("process %d did not exit after SIGKILL", reportPid)
 	}
 	return nil
 }
 
+// signalTargetRunning reports whether the signal target still has a process that
+// is actually RUNNING, as opposed to one waiting to be reaped.
+//
+// kill(2) with signal 0 succeeds for a zombie: the PID still exists until its
+// parent collects it. That matters because the target here is usually a process
+// GROUP, and a terminated leader's child is briefly a zombie before init/launchd
+// reaps it. Treating that window as "still alive" made termination sit through
+// both grace periods, SIGKILL an already-dead group, and then report
+// "did not exit after SIGKILL" for a tree that had in fact stopped — turning a
+// successful cleanup into a spurious failure (and a flaky one, since it depends on
+// reap timing).
+//
+// Zombie detection goes through ps, which is available on every Unix we target and
+// avoids a /proc dependency Darwin does not have. It is only consulted when the
+// cheap kill check says something is still there, so the common path costs nothing
+// extra. If ps cannot be run or its output cannot be parsed, the conservative
+// pre-existing answer (the kill result) stands.
+func signalTargetRunning(target int) bool {
+	if syscall.Kill(target, syscall.Signal(0)) != nil {
+		return false
+	}
+	// A negative target is a process GROUP: check whether any member is
+	// non-zombie. A positive target is an individual PID that is NOT its own
+	// group leader (processSignalTarget's fallback) — its actual PGID differs
+	// from its own PID, so matching rows by PGID here would look for a group
+	// that doesn't exist and always report "unknown" (conservatively alive).
+	// Check its own PID's state instead.
+	var running, ok bool
+	if target < 0 {
+		running, ok = processGroupHasRunningMember(-target)
+	} else {
+		running, ok = processIsRunning(target)
+	}
+	if !ok {
+		return true
+	}
+	return running
+}
+
+// processGroupHasRunningMember reports whether any member of pgid is in a state
+// other than zombie. ok is false when the group's states could not be determined.
+func processGroupHasRunningMember(pgid int) (running bool, ok bool) {
+	return processTableStateMatches(func(_, rowPgid int) bool { return rowPgid == pgid })
+}
+
+// processIsRunning reports whether pid itself is in a state other than zombie.
+// ok is false when pid's state could not be determined.
+func processIsRunning(pid int) (running bool, ok bool) {
+	return processTableStateMatches(func(rowPid, _ int) bool { return rowPid == pid })
+}
+
+// processTableStateMatches scans the process table once, via ps, and reports
+// whether any row satisfying match is non-zombie, and whether at least one
+// matching row was found at all (ok). No rows found means either the process
+// (or group) genuinely doesn't exist (a race with exit) or ps's output was
+// unparseable/restricted; either way, the caller should not claim knowledge.
+func processTableStateMatches(match func(pid, pgid int) bool) (running bool, ok bool) {
+	output, err := exec.Command("ps", "-A", "-o", "pid=,pgid=,stat=").Output()
+	if err != nil {
+		return false, false
+	}
+	found := false
+	for line := range strings.SplitSeq(string(output), "\n") {
+		fields := strings.Fields(line)
+		if len(fields) < 3 {
+			continue
+		}
+		rowPid, errPid := strconv.Atoi(fields[0])
+		rowPgid, errPgid := strconv.Atoi(fields[1])
+		if errPid != nil || errPgid != nil || !match(rowPid, rowPgid) {
+			continue
+		}
+		found = true
+		if !strings.HasPrefix(fields[2], "Z") {
+			return true, true
+		}
+	}
+	return false, found
+}
+
 func processSignalTarget(pid int) (int, error) {
 	if pid <= 1 {
 		return 0, fmt.Errorf("refusing to signal invalid pid %d", pid)
@@ -91,10 +206,14 @@ func processSignalTarget(pid int) (int, error) {
 		if pgid == pid {
 			target = -pid
 		}
-	} else if errors.Is(err, syscall.ESRCH) {
-		// Preserve the individual target; the signal call below treats ESRCH as
-		// already gone, which is a successful lifecycle outcome.
-		return pid, nil
+	} else {
+		if errors.Is(err, syscall.ESRCH) {
+			// Preserve the individual target; the signal call below treats ESRCH as
+			// already gone, which is a successful lifecycle outcome.
+			return pid, nil
+		}
+		// Conservatively retain the individual PID after other lookup failures;
+		// guessing and signalling a process group could affect unrelated processes.
 	}
 	return target, nil
 }

internal/execution/process_unix_test.go

@@ -0,0 +1,133 @@
+//go:build !windows
+
+package execution
+
+import (
+	"os/exec"
+	"strconv"
+	"syscall"
+	"testing"
+	"time"
+)
+
+// TestTerminateProcessTreeTreatsZombieGroupAsExited is the regression test for
+// counting unreaped processes as alive: kill(2) with signal 0 succeeds for a
+// zombie, so a group whose only remaining member is waiting to be reaped used to
+// sit through both grace periods, take a pointless SIGKILL, and then be reported
+// as "did not exit after SIGKILL" — a spurious cleanup failure whose timing
+// depended on when the reaper ran.
+func TestTerminateProcessTreeTreatsZombieGroupAsExited(t *testing.T) {
+	cmd := exec.Command("sh", "-c", "exit 0")
+	ConfigureProcessGroup(cmd)
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	pid := cmd.Process.Pid
+	// Deliberately do NOT Wait: the child stays a zombie in its own group, which
+	// is exactly the state a terminated tree passes through.
+	t.Cleanup(func() { _ = cmd.Wait() })
+
+	deadline := time.Now().Add(5 * time.Second)
+	for {
+		if zombie, ok := processIsZombie(pid); ok && zombie {
+			break
+		}
+		if time.Now().After(deadline) {
+			t.Skip("child did not reach the zombie state; ps output is unavailable in this environment")
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	if syscall.Kill(-pid, syscall.Signal(0)) != nil {
+		t.Skip("the zombie group is no longer signalable; cannot exercise the case")
+	}
+
+	if signalTargetRunning(-pid) {
+		t.Fatal("a group holding only a zombie must not count as running")
+	}
+	if err := TerminateProcessTree(pid, 50*time.Millisecond, 10*time.Millisecond); err != nil {
+		t.Fatalf("TerminateProcessTree on an already-exited tree: %v", err)
+	}
+}
+
+// TestTerminateProcessTreeStopsRunningGroup is the positive control: a group with
+// a live member must still be seen as running and then actually stopped, so the
+// zombie tolerance above cannot degrade into ignoring real processes.
+func TestTerminateProcessTreeStopsRunningGroup(t *testing.T) {
+	cmd := exec.Command("sh", "-c", "sleep 30")
+	ConfigureProcessGroup(cmd)
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	pid := cmd.Process.Pid
+	defer func() { _ = cmd.Wait() }()
+
+	if !signalTargetRunning(-pid) {
+		t.Fatal("a group with a live member must count as running")
+	}
+	if err := TerminateProcessTree(pid, time.Second, 10*time.Millisecond); err != nil {
+		t.Fatalf("TerminateProcessTree: %v", err)
+	}
+	if running, ok := processGroupHasRunningMember(pid); ok && running {
+		t.Fatal("the group still has a running member after termination")
+	}
+}
+
+// TestSignalTargetRunningTreatsZombieIndividualPIDAsExited is the regression
+// test for jatmn's second #774 finding: signalTargetRunning's zombie check
+// matched the individual-PID fallback target (a process that is NOT its own
+// group leader — processSignalTarget's positive-PID case) against process-table
+// rows by PGID. That target's actual PGID differs from its own PID by
+// definition (that's exactly why processSignalTarget fell back to the
+// individual PID instead of a negative group target), so no row ever matched,
+// "unknown" resulted every time, and signalTargetRunning conservatively (and
+// incorrectly) treated a zombie individual-PID target as still running.
+func TestSignalTargetRunningTreatsZombieIndividualPIDAsExited(t *testing.T) {
+	cmd := exec.Command("sh", "-c", "exit 0")
+	// Deliberately do NOT call ConfigureProcessGroup: the child inherits this
+	// test process's group, so it is not its own leader and processSignalTarget
+	// falls back to the individual (positive) PID.
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	pid := cmd.Process.Pid
+	t.Cleanup(func() { _ = cmd.Wait() })
+
+	deadline := time.Now().Add(5 * time.Second)
+	for {
+		if zombie, ok := processIsZombie(pid); ok && zombie {
+			break
+		}
+		if time.Now().After(deadline) {
+			t.Skip("child did not reach the zombie state; ps output is unavailable in this environment")
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+
+	target, err := processSignalTarget(pid)
+	if err != nil {
+		t.Fatalf("processSignalTarget: %v", err)
+	}
+	if target != pid {
+		t.Skip("child unexpectedly became its own group leader; cannot exercise the individual-PID fallback")
+	}
+	if signalTargetRunning(target) {
+		t.Fatal("a zombie individual-PID target must not count as running")
+	}
+}
+
+// processIsZombie reports a process's zombie state via ps. ok is false when the
+// state could not be read.
+func processIsZombie(pid int) (zombie bool, ok bool) {
+	output, err := exec.Command("ps", "-o", "stat=", "-p", strconv.Itoa(pid)).Output()
+	if err != nil {
+		return false, false
+	}
+	state := string(output)
+	for len(state) > 0 && (state[0] == ' ' || state[0] == '\n' || state[0] == '\t') {
+		state = state[1:]
+	}
+	if state == "" {
+		return false, false
+	}
+	return state[0] == 'Z', true
+}

internal/execution/process_windows.go

@@ -3,6 +3,8 @@
 package execution
 
 import (
+	"errors"
+	"fmt"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -12,10 +14,34 @@ import (
 
 func ConfigureProcessGroup(cmd *exec.Cmd) {}
 
+// KillProcessTree asks taskkill /T to kill pid and descendants it can still
+// discover from that live root. If taskkill fails, it falls back to killing pid
+// alone but still returns the tree error because descendants may have survived.
+// Neither path can recover descendants after the root has exited.
 func KillProcessTree(pid int) error {
-	if err := exec.Command(taskkillPath(), "/T", "/F", "/PID", strconv.Itoa(pid)).Run(); err == nil {
+	return killProcessTree(pid, runTaskkill, killRootProcess)
+}
+
+func killProcessTree(pid int, killTree, killRoot func(int) error) error {
+	treeErr := killTree(pid)
+	if treeErr == nil {
 		return nil
 	}
+	rootErr := killRoot(pid)
+	if rootErr != nil {
+		return errors.Join(
+			fmt.Errorf("kill process tree rooted at %d: %w", pid, treeErr),
+			fmt.Errorf("kill root process %d: %w", pid, rootErr),
+		)
+	}
+	return fmt.Errorf("kill process tree rooted at %d (root process killed directly): %w", pid, treeErr)
+}
+
+func runTaskkill(pid int) error {
+	return exec.Command(taskkillPath(), "/T", "/F", "/PID", strconv.Itoa(pid)).Run()
+}
+
+func killRootProcess(pid int) error {
 	process, err := os.FindProcess(pid)
 	if err != nil {
 		return err

internal/execution/process_windows_test.go

@@ -0,0 +1,29 @@
+//go:build windows
+
+package execution
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+func TestKillProcessTreeRetainsTreeErrorWhenRootFallbackSucceeds(t *testing.T) {
+	treeErr := errors.New("taskkill failed")
+	err := killProcessTree(42, func(int) error { return treeErr }, func(int) error { return nil })
+	if !errors.Is(err, treeErr) {
+		t.Fatalf("killProcessTree error = %v, want tree error", err)
+	}
+	if !strings.Contains(err.Error(), "root process killed directly") {
+		t.Fatalf("killProcessTree error = %q, want fallback context", err)
+	}
+}
+
+func TestKillProcessTreeJoinsTreeAndRootErrors(t *testing.T) {
+	treeErr := errors.New("taskkill failed")
+	rootErr := errors.New("root kill failed")
+	err := killProcessTree(42, func(int) error { return treeErr }, func(int) error { return rootErr })
+	if !errors.Is(err, treeErr) || !errors.Is(err, rootErr) {
+		t.Fatalf("killProcessTree error = %v, want both failures", err)
+	}
+}

internal/mcp/config.go

@@ -35,7 +35,7 @@ type Server struct {
 	// credential lookup uses it to avoid reusing legacy user tokens by name.
 	ProjectConfigured bool
 	// UnconfiguredDefault is true when this server is one of Zero's built-in
-	// defaults (e.g. keyless Firecrawl) that the user never touched in their
+	// defaults (e.g. keyless Exa) that the user never touched in their
 	// config — no credentials, no overrides. Callers use it to avoid warning
 	// loudly when a server nobody configured fails to connect.
 	UnconfiguredDefault bool

internal/mcp/config_test.go

@@ -1,6 +1,8 @@
 package mcp
 
 import (
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -90,7 +92,7 @@ func TestNormalizeConfigValidatesTransportBoundaries(t *testing.T) {
 
 func TestNormalizeConfigFlagsUnconfiguredDefault(t *testing.T) {
 	cfg := config.MCPConfig{Servers: map[string]config.MCPServerConfig{
-		"firecrawl": config.DefaultMCPServers()["firecrawl"],
+		"exa": config.DefaultMCPServers()["exa"],
 		"web": {
 			Type: "http",
 			URL:  "https://example.com/mcp",
@@ -107,8 +109,8 @@ func TestNormalizeConfigFlagsUnconfiguredDefault(t *testing.T) {
 		byName[server.Name] = server
 	}
 
-	if !byName["firecrawl"].UnconfiguredDefault {
-		t.Fatal("an untouched firecrawl default should be flagged UnconfiguredDefault")
+	if !byName["exa"].UnconfiguredDefault {
+		t.Fatal("an untouched exa default should be flagged UnconfiguredDefault")
 	}
 	if byName["web"].UnconfiguredDefault {
 		t.Fatal("a server the user configured must not be flagged UnconfiguredDefault")
@@ -240,3 +242,116 @@ func TestCopyStringMapTrimsKeysAndPreservesValues(t *testing.T) {
 		t.Fatalf("copied[TOKEN] = %q, want value preserved verbatim", copied["TOKEN"])
 	}
 }
+
+// Startup behavior for the firecrawl -> exa default migration: a user who
+// disabled the retired default must end up with no Exa server to connect to,
+// not merely a disabled entry in the resolved config.
+func TestNormalizeConfigSkipsExaAfterLegacyFirecrawlDisable(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"disabled":true}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := config.ResolveMCP(config.ResolveOptions{UserConfigPath: path})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	servers, err := NormalizeConfig(cfg)
+	if err != nil {
+		t.Fatalf("NormalizeConfig: %v", err)
+	}
+	for _, server := range servers {
+		if server.Name == "exa" {
+			t.Fatalf("exa must not be started after the user disabled the default it replaced: %#v", server)
+		}
+	}
+}
+
+// The same path with no legacy disable still starts Exa, so the migration
+// cannot quietly switch off the default for everyone else.
+func TestNormalizeConfigStartsExaWithoutLegacyDisable(t *testing.T) {
+	cfg, err := config.ResolveMCP(config.ResolveOptions{})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	servers, err := NormalizeConfig(cfg)
+	if err != nil {
+		t.Fatalf("NormalizeConfig: %v", err)
+	}
+	for _, server := range servers {
+		if server.Name == "exa" {
+			if !server.UnconfiguredDefault {
+				t.Fatalf("an untouched exa default should be flagged unconfigured: %#v", server)
+			}
+			return
+		}
+	}
+	t.Fatal("expected the exa default to be started out of the box")
+}
+
+// The failure path CodeRabbit flagged: a firecrawl entry that named only a
+// header relied on the retired default for its transport. Resolving it must
+// still produce a complete server — an incomplete one fails NormalizeConfig,
+// which takes down every other server's startup with it, not just this one.
+func TestNormalizeConfigResolvesPartialRetiredDefaultEntry(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"headers":{"Authorization":"Bearer k"}}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := config.ResolveMCP(config.ResolveOptions{UserConfigPath: path})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	servers, err := NormalizeConfig(cfg)
+	if err != nil {
+		t.Fatalf("a header-only legacy entry must not break startup: %v", err)
+	}
+	var firecrawl *Server
+	var sawExa bool
+	for i := range servers {
+		switch servers[i].Name {
+		case "firecrawl":
+			firecrawl = &servers[i]
+		case "exa":
+			sawExa = true
+		}
+	}
+	if firecrawl == nil {
+		t.Fatalf("expected the customized firecrawl server to survive: %#v", servers)
+	}
+	if firecrawl.Type != ServerTypeHTTP || firecrawl.URL != "https://mcp.firecrawl.dev/v2/mcp" {
+		t.Fatalf("firecrawl lost the transport its entry relied on: %#v", *firecrawl)
+	}
+	if firecrawl.Headers["Authorization"] != "Bearer k" {
+		t.Fatalf("firecrawl lost the user's header: %#v", *firecrawl)
+	}
+	if !sawExa {
+		t.Fatal("the new exa default should still start alongside it")
+	}
+}
+
+// The mirror case: an entry that names its own stdio transport must not have
+// the retired http default grafted onto it, which would be rejected outright.
+func TestNormalizeConfigLeavesRetiredEntryWithOwnTransportAlone(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(`{"mcp":{"servers":{"firecrawl":{"command":"firecrawl-mcp"}}}}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := config.ResolveMCP(config.ResolveOptions{UserConfigPath: path})
+	if err != nil {
+		t.Fatalf("ResolveMCP: %v", err)
+	}
+	servers, err := NormalizeConfig(cfg)
+	if err != nil {
+		t.Fatalf("a self-hosted stdio entry must keep working: %v", err)
+	}
+	for _, server := range servers {
+		if server.Name != "firecrawl" {
+			continue
+		}
+		if server.Type != ServerTypeStdio || server.Command != "firecrawl-mcp" {
+			t.Fatalf("the user's own stdio transport was corrupted: %#v", server)
+		}
+		return
+	}
+	t.Fatalf("expected the self-hosted firecrawl server to survive: %#v", servers)
+}

internal/mcp/registry.go

@@ -176,9 +176,11 @@ func RegisterTools(ctx context.Context, registry *tools.Registry, cfg config.MCP
 			staged = append(staged, tool)
 		}
 	}
-	for _, tool := range staged {
-		registry.Register(tool)
+	registered := make([]tools.Tool, 0, len(staged))
+	for index := range staged {
+		registered = append(registered, staged[index])
 	}
+	registry.RegisterBatch(registered)
 	return runtime, nil
 }
 

internal/mcp/registry_test.go

@@ -70,6 +70,62 @@ func TestRegisterToolsAddsPromptGatedMCPTools(t *testing.T) {
 	}
 }
 
+func TestRegisterToolsPublishesServerToolsInOneGeneration(t *testing.T) {
+	registry := tools.NewRegistry()
+	before := registry.Snapshot().Generation
+	client := &fakeToolClient{listed: []RemoteTool{
+		{Name: "lookup", Description: "Lookup documentation"},
+		{Name: "search", Description: "Search documentation"},
+	}}
+	runtime, err := RegisterTools(context.Background(), registry, config.MCPConfig{Servers: map[string]config.MCPServerConfig{
+		"docs": {Type: "stdio", Command: "docs-mcp"},
+	}}, RegisterOptions{ClientFactory: func(context.Context, Server) (ToolClient, error) {
+		return client, nil
+	}})
+	if err != nil {
+		t.Fatalf("RegisterTools() error = %v", err)
+	}
+	defer runtime.Close()
+
+	after := registry.Snapshot()
+	if after.Generation != before+1 {
+		t.Fatalf("registry generation = %d, want %d", after.Generation, before+1)
+	}
+	for _, name := range []string{"mcp_docs_lookup", "mcp_docs_search"} {
+		if _, ok := registry.Get(name); !ok {
+			t.Fatalf("expected %s to be published in the batch", name)
+		}
+	}
+}
+
+func TestRegisterToolsPublishesNoneWhenServerToolValidationFails(t *testing.T) {
+	registry := tools.NewRegistry()
+	before := registry.Snapshot().Generation
+	client := &fakeToolClient{listed: []RemoteTool{
+		{Name: "lookup", Description: "Lookup documentation"},
+		{Name: "", Description: "Invalid nameless tool"},
+	}}
+	runtime, err := RegisterTools(context.Background(), registry, config.MCPConfig{Servers: map[string]config.MCPServerConfig{
+		"docs": {Type: "stdio", Command: "docs-mcp"},
+	}}, RegisterOptions{ClientFactory: func(context.Context, Server) (ToolClient, error) {
+		return client, nil
+	}})
+	if err != nil {
+		t.Fatalf("RegisterTools() error = %v", err)
+	}
+	defer runtime.Close()
+
+	if got := registry.Snapshot().Generation; got != before {
+		t.Fatalf("registry generation = %d, want unchanged %d", got, before)
+	}
+	if _, ok := registry.Get("mcp_docs_lookup"); ok {
+		t.Fatal("valid prefix of rejected server batch was published")
+	}
+	if skipped := runtime.Skipped(); len(skipped) != 1 || skipped[0].Name != "docs" || skipped[0].Err == nil {
+		t.Fatalf("Skipped() = %#v, want one validation failure for docs", skipped)
+	}
+}
+
 func TestRegisterToolsMarksPersistentlyApprovedToolsAllow(t *testing.T) {
 	store, err := NewPermissionStore(StoreOptions{
 		FilePath: filepath.Join(t.TempDir(), "permissions.json"),
@@ -153,16 +209,16 @@ func TestRegisterToolsSkipsUnreachableServerAndKeepsOthers(t *testing.T) {
 }
 
 func TestRegisterToolsFlagsUnconfiguredDefaultOnSkip(t *testing.T) {
-	// firecrawl is seeded by config.DefaultMCPServers with no credentials; when a
-	// user never configures it, a connect failure (e.g. the real HTTP 401 from
-	// issue #552) must be recorded as UnconfiguredDefault so callers can avoid
+	// Exa is seeded by config.DefaultMCPServers with no credentials; when a
+	// user never configures it, a connect failure must be recorded as
+	// UnconfiguredDefault so callers can avoid
 	// warning about a server the user never asked for. "custom" is configured by
 	// the user and must NOT be flagged even though it also fails to connect.
 	registry := tools.NewRegistry()
 
 	runtime, err := RegisterTools(context.Background(), registry, config.MCPConfig{Servers: map[string]config.MCPServerConfig{
-		"firecrawl": config.DefaultMCPServers()["firecrawl"],
-		"custom":    {Type: "stdio", Command: "custom-mcp"},
+		"exa":    config.DefaultMCPServers()["exa"],
+		"custom": {Type: "stdio", Command: "custom-mcp"},
 	}}, RegisterOptions{
 		ClientFactory: func(_ context.Context, server Server) (ToolClient, error) {
 			return nil, errors.New(server.Name + " connect failed")
@@ -177,12 +233,12 @@ func TestRegisterToolsFlagsUnconfiguredDefaultOnSkip(t *testing.T) {
 	for _, skipped := range runtime.Skipped() {
 		byName[skipped.Name] = skipped
 	}
-	firecrawl, ok := byName["firecrawl"]
+	exa, ok := byName["exa"]
 	if !ok {
-		t.Fatalf("Skipped() = %#v, want an entry for firecrawl", runtime.Skipped())
+		t.Fatalf("Skipped() = %#v, want an entry for exa", runtime.Skipped())
 	}
-	if !firecrawl.UnconfiguredDefault {
-		t.Fatalf("Skipped()[firecrawl] = %#v, want UnconfiguredDefault", firecrawl)
+	if !exa.UnconfiguredDefault {
+		t.Fatalf("Skipped()[exa] = %#v, want UnconfiguredDefault", exa)
 	}
 	custom, ok := byName["custom"]
 	if !ok {

internal/modelregistry/catalog.go

@@ -231,6 +231,12 @@ func reasoningEffortsForModelName(name string) []ReasoningEffort {
 		// the gateway's translation concern — unknown fields are ignored, so the
 		// worst case is a silent no-op rather than a 400.
 		return []ReasoningEffort{ReasoningEffortLow, ReasoningEffortMedium, ReasoningEffortHigh}
+	case strings.Contains(n, "deepseek"):
+		// DeepSeek V4 (deepseek-v4-flash / deepseek-v4-pro) exposes thinking-mode
+		// effort control through the OpenAI-compatible reasoning_effort parameter.
+		// The API accepts low/high/max and maps medium/xhigh onto high, so only
+		// the three distinct tiers are advertised.
+		return []ReasoningEffort{ReasoningEffortLow, ReasoningEffortHigh, ReasoningEffortMax}
 	default:
 		return nil
 	}

internal/modelregistry/effort_fallback_test.go

@@ -20,6 +20,10 @@ func TestReasoningEffortsFallbackForGPT5AndOSeries(t *testing.T) {
 		{"hy3", []ReasoningEffort{ReasoningEffortLow, ReasoningEffortMedium, ReasoningEffortHigh}},
 		{"hunyuan-t1", []ReasoningEffort{ReasoningEffortLow, ReasoningEffortMedium, ReasoningEffortHigh}},
 		{"openai/o3-mini", []ReasoningEffort{ReasoningEffortLow, ReasoningEffortMedium, ReasoningEffortHigh}}, // github-style vendor/ id
+		{"deepseek-v4-flash", []ReasoningEffort{ReasoningEffortLow, ReasoningEffortHigh, ReasoningEffortMax}},
+		{"deepseek-v4-pro", []ReasoningEffort{ReasoningEffortLow, ReasoningEffortHigh, ReasoningEffortMax}},
+		{"deepseek-reasoner", []ReasoningEffort{ReasoningEffortLow, ReasoningEffortHigh, ReasoningEffortMax}},
+		{"deepseek-chat", []ReasoningEffort{ReasoningEffortLow, ReasoningEffortHigh, ReasoningEffortMax}},
 		{"gpt-4.1", nil}, // non-reasoning, registered: stays empty
 		{"gpt-4o-mini", nil},
 		{"ollama/llama3.1", nil},

internal/pathjail/pathjail.go

@@ -0,0 +1,177 @@
+// Package pathjail confines file operations to a directory tree.
+//
+// It exists because the obvious guard does not work. Checking a path with
+// Lstat and then handing the same string to MkdirAll, CreateTemp, Rename or
+// Remove is two independent resolutions with a gap between them, and every
+// operation after the check re-resolves the ANCESTORS as well. A store that
+// verified only its own directory and file was therefore writable outside its
+// tree whenever any component above them was a link: the check passed, and the
+// syscall that followed went somewhere else.
+//
+// On Windows the same guard failed for a second, independent reason. A junction
+// is a reparse point but NOT a symlink, so os.Lstat reports it as ModeIrregular
+// with ModeSymlink clear, and a guard testing only ModeSymlink returns "not a
+// link" when pointed straight at one. Junctions also need no privilege to
+// create, unlike Windows symlinks, so this is reachable by exactly the
+// unprivileged user a workspace guard is meant to contain.
+//
+// The fix for both is to stop naming things by path. Open a handle on the root
+// once and address everything below it relative to that handle, so the kernel
+// resolves each component against an object that cannot be swapped underneath.
+// os.Root is that handle: it refuses any component that would escape, including
+// a Windows reparse point, and it is the same idea the sandbox uses for ACL
+// materialization.
+package pathjail
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// ErrEscapes reports a target that is not inside the root it was confined to.
+// Returned before anything is opened, so a caller cannot act on the path first.
+var ErrEscapes = errors.New("path escapes its root")
+
+// ErrReparse reports a link or reparse point where a real file or directory was
+// required.
+var ErrReparse = errors.New("refusing to write through a link")
+
+// Open confines dir to root and returns a handle on root plus dir expressed
+// relative to it. The caller closes the handle.
+//
+// root is resolved normally, because it is the boundary the caller chose and
+// trusts (a workspace the operator opened, say, which may legitimately sit under
+// a link). Everything BELOW it is resolved against the returned handle and
+// cannot escape.
+func Open(root, dir string) (*os.Root, string, error) {
+	// Only a genuinely EMPTY value is treated as missing; every other spelling is
+	// used verbatim. Testing TrimSpace(...) == "" instead would retarget the very
+	// paths this guards: " " is a legal directory name on unix, so trimming would
+	// reject it as "no root" or silently swap dir for root, which is the same
+	// retargeting bug as trimming "root " down to "root".
+	if root == "" {
+		return nil, "", fmt.Errorf("%w: no root to confine %q to", ErrEscapes, dir)
+	}
+	if dir == "" {
+		dir = root
+	}
+	// Rel before Open, so an escaping target is refused without opening
+	// anything. filepath.Rel is lexical, which is the right test here: it says
+	// what the caller ASKED for, and the handle enforces what actually happens.
+	relative, err := filepath.Rel(root, dir)
+	if err != nil {
+		return nil, "", fmt.Errorf("%w: %q against %q: %v", ErrEscapes, dir, root, err)
+	}
+	if relative == ".." || strings.HasPrefix(relative, ".."+string(filepath.Separator)) {
+		return nil, "", fmt.Errorf("%w: %q is outside %q", ErrEscapes, dir, root)
+	}
+	// The root is created if it is missing, by ordinary pathname, because it is
+	// the boundary the caller declared rather than anything being confined. The
+	// stores this replaced called MkdirAll on the whole tree, so this creates
+	// strictly less by pathname than before, and everything BELOW root is opened
+	// relative to the handle.
+	if err := os.MkdirAll(root, 0o700); err != nil {
+		return nil, "", fmt.Errorf("create %s: %w", root, err)
+	}
+	handle, err := os.OpenRoot(root)
+	if err != nil {
+		return nil, "", fmt.Errorf("open %s: %w", root, err)
+	}
+	return handle, relative, nil
+}
+
+// RefuseReparse fails when relative names a link or reparse point.
+//
+// Absent is fine: a name that does not exist yet is what a create is for.
+//
+// This is belt to os.Root's braces. The handle already refuses to traverse a
+// reparse point, so this exists to give the FINAL component a clear error
+// instead of an "escapes from parent" one, and to keep the refusal explicit at
+// the point a reader looks for it.
+//
+// ModeIrregular is tested alongside ModeSymlink deliberately: that is what a
+// Windows junction reports, and a guard checking only ModeSymlink lets one
+// straight through.
+func RefuseReparse(handle *os.Root, relative string) error {
+	// A trailing separator makes os.Root.Lstat resolve the terminal component on
+	// Windows (doInRootAlwaysResolveTerminalSlash), so a junction named with a
+	// trailing slash would be stat'd as its target and wave through as "not a
+	// link". Strip it so the final component itself is the thing inspected.
+	//
+	// os.IsPathSeparator rather than a literal `/\` set, because backslash is a
+	// separator only on Windows: on unix it is an ordinary filename character, and
+	// trimming it would inspect "linked" when asked about a symlink genuinely
+	// named `linked\` — reporting "not a link" for one that is.
+	if trimmed := trimTrailingSeparators(relative); trimmed != "" {
+		relative = trimmed
+	}
+	info, err := handle.Lstat(relative)
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			return nil
+		}
+		return fmt.Errorf("inspect %s: %w", relative, err)
+	}
+	if info.Mode()&(os.ModeSymlink|os.ModeIrregular) != 0 {
+		return fmt.Errorf("%w: %s", ErrReparse, relative)
+	}
+	return nil
+}
+
+// trimTrailingSeparators drops the path separators at the end of a name, using
+// the ACTIVE platform's definition of one: `/` and `\` on Windows, `/` only on
+// unix, where a backslash is a legal character in a filename.
+func trimTrailingSeparators(path string) string {
+	end := len(path)
+	for end > 0 && os.IsPathSeparator(path[end-1]) {
+		end--
+	}
+	return path[:end]
+}
+
+// randomBytes fills b with cryptographic randomness. A variable rather than a
+// direct crypto/rand call so a test can force the name collision that exercises
+// the O_EXCL retry below — the branch that matters, and one a real random source
+// will not reach on demand.
+var randomBytes = rand.Read
+
+// CreateTemp makes an O_EXCL temp file named prefix.<random>suffix inside dir,
+// relative to handle, and returns it with its relative path.
+//
+// O_EXCL rather than a fixed name: a link planted at a predictable temp path
+// between the check and the create is the same race this package exists to
+// close, and O_EXCL makes the kernel refuse it rather than us.
+func CreateTemp(handle *os.Root, dir, prefix, suffix string) (*os.File, string, error) {
+	// prefix and suffix are NAME fragments, not path fragments. A separator or a
+	// "."/".." in either would relocate the file out of dir — a prefix of
+	// "../escaped", or a suffix of ".tmp/../evil" that also erases the random
+	// component and with it the O_EXCL unpredictability the file relies on.
+	// Reject them up front so the file lands where dir promises.
+	for _, fragment := range []string{prefix, suffix} {
+		if strings.ContainsAny(fragment, `/\`) || fragment == "." || fragment == ".." {
+			return nil, "", fmt.Errorf("%w: temporary name fragment %q must be a single path component", ErrEscapes, fragment)
+		}
+	}
+	for attempt := 0; attempt < 10; attempt++ {
+		noise := make([]byte, 8)
+		if _, err := randomBytes(noise); err != nil {
+			return nil, "", fmt.Errorf("generate a temporary name: %w", err)
+		}
+		relative := filepath.Join(dir, prefix+"."+hex.EncodeToString(noise)+suffix)
+		file, err := handle.OpenFile(relative, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0o600)
+		if err == nil {
+			return file, relative, nil
+		}
+		if errors.Is(err, fs.ErrExist) {
+			continue
+		}
+		return nil, "", err
+	}
+	return nil, "", errors.New("could not create a temporary file with an unused name")
+}

internal/pathjail/pathjail_test.go

@@ -0,0 +1,360 @@
+package pathjail
+
+import (
+	"encoding/hex"
+	"errors"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"testing"
+)
+
+// linkDir points link at target, using whatever kind of link this platform lets
+// an unprivileged process create.
+//
+// On Windows that is a JUNCTION, not a symlink, and the difference is the whole
+// reason this package exists twice over. A symlink needs
+// SeCreateSymbolicLinkPrivilege, which an ordinary account does not hold, so a
+// test written with os.Symlink silently skips on Windows and proves nothing
+// there. A junction needs no privilege at all, so it is both the reachable
+// attack and the only one that can be tested.
+func linkDir(t *testing.T, target, link string) {
+	t.Helper()
+	if runtime.GOOS == "windows" {
+		if out, err := exec.Command("cmd", "/c", "mklink", "/J", link, target).CombinedOutput(); err != nil {
+			t.Skipf("cannot create a junction: %v %s", err, out)
+		}
+		return
+	}
+	if err := os.Symlink(target, link); err != nil {
+		t.Skipf("cannot create a symlink: %v", err)
+	}
+}
+
+// The reported defect: a link in an ANCESTOR of the target, not at the target
+// itself. Every guard that checked only the final directory and file passed
+// this, because the components it checked were genuinely not links; the ones
+// the syscall then traversed were.
+func TestAnAncestorLinkCannotRedirectAWrite(t *testing.T) {
+	base := t.TempDir()
+	outside := filepath.Join(base, "outside")
+	workspace := filepath.Join(base, "workspace")
+	for _, dir := range []string{outside, workspace} {
+		if err := os.MkdirAll(dir, 0o700); err != nil {
+			t.Fatal(err)
+		}
+	}
+	linkDir(t, outside, filepath.Join(workspace, ".zero"))
+
+	handle, relative, err := Open(workspace, filepath.Join(workspace, ".zero", "store"))
+	if err != nil {
+		t.Fatalf("Open should confine, not refuse outright: %v", err)
+	}
+	defer handle.Close()
+
+	if err := handle.MkdirAll(relative, 0o700); err == nil {
+		t.Fatal("created a directory through a linked ancestor, so a write can still leave the workspace")
+	}
+	if _, err := os.Stat(filepath.Join(outside, "store")); !os.IsNotExist(err) {
+		t.Errorf("something was created outside the workspace, stat error = %v", err)
+	}
+}
+
+// RefuseReparse has to catch a junction, which is the case os.ModeSymlink alone
+// misses. Asserted through the exported helper rather than by reading the mode,
+// so the test fails if the predicate is ever narrowed back.
+func TestRefuseReparseCatchesAJunctionNotJustASymlink(t *testing.T) {
+	base := t.TempDir()
+	target := filepath.Join(base, "target")
+	inside := filepath.Join(base, "inside")
+	for _, dir := range []string{target, inside} {
+		if err := os.MkdirAll(dir, 0o700); err != nil {
+			t.Fatal(err)
+		}
+	}
+	linkDir(t, target, filepath.Join(inside, "linked"))
+
+	handle, relative, err := Open(inside, inside)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer handle.Close()
+
+	err = RefuseReparse(handle, filepath.Join(relative, "linked"))
+	if !errors.Is(err, ErrReparse) {
+		t.Fatalf("RefuseReparse(link) = %v, want ErrReparse; on Windows a junction reports ModeIrregular, so a ModeSymlink-only check returns nil here", err)
+	}
+}
+
+// A name that does not exist yet is what a create is for, so it must not be
+// refused. Without this the guard above would be satisfied by refusing
+// everything.
+func TestRefuseReparseAllowsAnAbsentName(t *testing.T) {
+	base := t.TempDir()
+	handle, relative, err := Open(base, base)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer handle.Close()
+	if err := RefuseReparse(handle, filepath.Join(relative, "not-there.md")); err != nil {
+		t.Errorf("an absent name was refused: %v", err)
+	}
+	if err := RefuseReparse(handle, relative); err != nil {
+		t.Errorf("an ordinary directory was refused: %v", err)
+	}
+}
+
+// Open refuses a target outside its root before opening anything, so a caller
+// cannot act on the path first.
+func TestOpenRefusesATargetOutsideTheRoot(t *testing.T) {
+	base := t.TempDir()
+	inside := filepath.Join(base, "inside")
+	if err := os.MkdirAll(inside, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	for _, target := range []string{
+		filepath.Join(base, "sibling"),
+		filepath.Join(inside, "..", "..", "escape"),
+	} {
+		if _, _, err := Open(inside, target); !errors.Is(err, ErrEscapes) {
+			t.Errorf("Open(%q, %q) = %v, want ErrEscapes", inside, target, err)
+		}
+	}
+	if _, _, err := Open("", filepath.Join(base, "anything")); !errors.Is(err, ErrEscapes) {
+		t.Error("an empty root was accepted; a boundary is not optional")
+	}
+}
+
+// CreateTemp must use O_EXCL and an unpredictable name, so a link planted at a
+// guessable temp path is refused by the kernel rather than followed.
+func TestCreateTempIsExclusiveAndUnpredictable(t *testing.T) {
+	base := t.TempDir()
+	handle, relative, err := Open(base, base)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer handle.Close()
+
+	seen := map[string]bool{}
+	for i := 0; i < 8; i++ {
+		file, name, err := CreateTemp(handle, relative, "note", ".tmp")
+		if err != nil {
+			t.Fatal(err)
+		}
+		file.Close()
+		if seen[name] {
+			t.Fatalf("CreateTemp reused the name %q, so two concurrent writes would stomp each other", name)
+		}
+		seen[name] = true
+		if filepath.Ext(name) != ".tmp" {
+			t.Errorf("temp name %q lost its suffix, so a listing may pick it up as real content", name)
+		}
+	}
+}
+
+// A legitimate directory whose name carries a space must be confined as spelled.
+// Trimming it would open a different filesystem object.
+//
+// A LEADING space, deliberately: Win32 normalizes a component's trailing spaces
+// and dots away, so "root " and "root" are one object there and a trailing-space
+// case cannot express the bug on Windows. A leading space survives on every
+// platform, so this runs everywhere rather than being gated to unix.
+// The path is RELATIVE, under t.Chdir, so the leading space sits at the start of
+// the whole string. An absolute filepath.Join(base, " root") would put the space
+// in the middle, where TrimSpace cannot reach it — the test would then pass
+// against the very guard it exists to catch, on every platform.
+func TestOpenPreservesSpaceInPaths(t *testing.T) {
+	base := t.TempDir()
+	t.Chdir(base)
+	const spaced = " root" // the leading space is part of the name
+
+	handle, relative, err := Open(spaced, spaced)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer handle.Close()
+
+	// Write through the handle, then confirm the bytes landed under the spelling
+	// the caller asked for — the property that actually matters, and one
+	// handle.Name() alone would not prove.
+	file, _, err := CreateTemp(handle, relative, "probe", ".tmp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	name := file.Name()
+	if err := file.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(filepath.Join(base, spaced, filepath.Base(name))); err != nil {
+		t.Errorf("a file created through the handle is not under %q: %v — the leading space was trimmed away", spaced, err)
+	}
+	if _, err := os.Stat(filepath.Join(base, "root")); err == nil {
+		t.Error(`a trimmed "root" was created instead of the requested " root"`)
+	}
+}
+
+// A whitespace-only name is a legal directory on unix, so it must be confined as
+// given rather than treated as "no root" or silently swapped for the root.
+func TestOpenAcceptsAWhitespaceOnlyComponent(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Win32 normalizes a whitespace-only component away; the name is not expressible there")
+	}
+	// The path must be whitespace-only IN FULL for this to bite, so it has to be
+	// relative: an absolute path ending in " " still has a non-empty TrimSpace and
+	// would sail past the old guard, making the test prove nothing.
+	t.Chdir(t.TempDir())
+	handle, _, err := Open(" ", " ")
+	if err != nil {
+		t.Fatalf("a whitespace-only path was rejected as missing: %v", err)
+	}
+	defer handle.Close()
+	if _, err := os.Stat(" "); err != nil {
+		t.Errorf("the whitespace-only directory was not created as spelled: %v", err)
+	}
+}
+
+// prefix and suffix are name fragments. A separator or traversal in either must
+// be refused, or the file lands outside dir and (for a suffix erasing the random
+// component) loses the O_EXCL unpredictability it depends on.
+func TestCreateTempRejectsPathFragmentsThatEscapeTheDir(t *testing.T) {
+	base := t.TempDir()
+	inside := filepath.Join(base, "inside")
+	if err := os.MkdirAll(inside, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	// root is base, dir is the subdirectory: a "../escaped" fragment lands in
+	// base — still inside the os.Root, so os.Root does NOT catch it — but outside
+	// the dir CreateTemp promised. This is the case the reviewers reproduced.
+	handle, relative, err := Open(base, inside)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer handle.Close()
+	cases := []struct{ prefix, suffix string }{
+		{"../escaped", ".tmp"},
+		{`..\sibling`, ".tmp"},
+		{"note", ".tmp/../evil"},
+		{"note", ".."},
+		{"..", ".tmp"},
+	}
+	for _, c := range cases {
+		if _, _, err := CreateTemp(handle, relative, c.prefix, c.suffix); !errors.Is(err, ErrEscapes) {
+			t.Errorf("CreateTemp(prefix=%q, suffix=%q) = %v, want ErrEscapes", c.prefix, c.suffix, err)
+		}
+	}
+	// Nothing may have leaked into base above the promised dir.
+	entries, _ := os.ReadDir(base)
+	for _, entry := range entries {
+		if entry.Name() != "inside" {
+			t.Errorf("a temp fragment escaped into the parent: %q", entry.Name())
+		}
+	}
+}
+
+// A junction named with a trailing separator must still be refused. On Windows
+// os.Root.Lstat resolves the terminal component when the name ends in a
+// separator, so without trimming it the link is stat'd as its target and waved
+// through.
+func TestRefuseReparseCatchesALinkNamedWithATrailingSeparator(t *testing.T) {
+	base := t.TempDir()
+	target := filepath.Join(base, "target")
+	inside := filepath.Join(base, "inside")
+	for _, dir := range []string{target, inside} {
+		if err := os.MkdirAll(dir, 0o700); err != nil {
+			t.Fatal(err)
+		}
+	}
+	linkDir(t, target, filepath.Join(inside, "linked"))
+	handle, relative, err := Open(inside, inside)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer handle.Close()
+	name := filepath.Join(relative, "linked") + string(filepath.Separator)
+	if err := RefuseReparse(handle, name); !errors.Is(err, ErrReparse) {
+		t.Fatalf("RefuseReparse(%q) = %v, want ErrReparse", name, err)
+	}
+}
+
+// The O_EXCL retry is the branch that protects an existing file, and a real
+// random source will not collide on demand — so force it. The first two draws
+// return the same bytes: the name is pre-created, CreateTemp must refuse to
+// reuse it, leave its contents alone, and come back with a different name.
+func TestCreateTempRetriesWithoutClobberingAnExistingName(t *testing.T) {
+	base := t.TempDir()
+	handle, relative, err := Open(base, base)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer handle.Close()
+
+	draws := [][]byte{
+		{1, 1, 1, 1, 1, 1, 1, 1}, // collides with the pre-created file
+		{1, 1, 1, 1, 1, 1, 1, 1}, // and again, so the retry must keep trying
+		{2, 2, 2, 2, 2, 2, 2, 2}, // finally a free name
+	}
+	previous := randomBytes
+	t.Cleanup(func() { randomBytes = previous })
+	call := 0
+	randomBytes = func(b []byte) (int, error) {
+		copy(b, draws[min(call, len(draws)-1)])
+		call++
+		return len(b), nil
+	}
+
+	taken := filepath.Join(base, "note."+hex.EncodeToString(draws[0])+".tmp")
+	if err := os.WriteFile(taken, []byte("do not clobber me"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	file, name, err := CreateTemp(handle, relative, "note", ".tmp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer file.Close()
+
+	if filepath.Base(name) == filepath.Base(taken) {
+		t.Fatalf("CreateTemp returned the name that was already taken (%q), so O_EXCL did not protect it", name)
+	}
+	kept, err := os.ReadFile(taken)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(kept) != "do not clobber me" {
+		t.Errorf("the pre-existing file was overwritten: %q", kept)
+	}
+	if call < 2 {
+		t.Errorf("the random source was drawn %d time(s); the collision path never ran", call)
+	}
+}
+
+// On unix a backslash is an ordinary filename character, not a separator, so a
+// link genuinely named `linked\` must still be refused. Trimming backslashes
+// unconditionally would inspect "linked" instead and report "not a link" for one
+// that is.
+func TestRefuseReparseKeepsABackslashInAUnixName(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip(`backslash is a separator on Windows, so this name is not expressible there`)
+	}
+	base := t.TempDir()
+	target := filepath.Join(base, "target")
+	inside := filepath.Join(base, "inside")
+	for _, dir := range []string{target, inside} {
+		if err := os.MkdirAll(dir, 0o700); err != nil {
+			t.Fatal(err)
+		}
+	}
+	linkDir(t, target, filepath.Join(inside, `linked\`))
+
+	handle, relative, err := Open(inside, inside)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer handle.Close()
+
+	name := filepath.Join(relative, `linked\`)
+	if err := RefuseReparse(handle, name); !errors.Is(err, ErrReparse) {
+		t.Fatalf("RefuseReparse(%q) = %v, want ErrReparse — the backslash is part of the name here, not a separator", name, err)
+	}
+}

internal/peermsg/private_dir_windows.go

@@ -104,7 +104,7 @@ func windowsTokenOwner(token windows.Token) (*windows.SID, error) {
 	}
 	owner := (*windowsTokenOwnerInfo)(unsafe.Pointer(&buffer[0])).owner
 	if owner == nil {
-		return nil, errors.New("Windows access token has no default owner")
+		return nil, errors.New("windows access token has no default owner")
 	}
 	return owner.Copy()
 }

internal/perfbench/turn_bench.go

@@ -191,6 +191,7 @@ type TurnBenchResult struct {
 type TurnBenchTotals struct {
 	InputTokens       int64 `json:"inputTokens"`
 	CachedInputTokens int64 `json:"cachedInputTokens"`
+	CacheWriteTokens  int64 `json:"cacheWriteTokens"`
 	OutputTokens      int64 `json:"outputTokens"`
 	ModelRequests     int64 `json:"modelRequests"`
 	ToolCalls         int64 `json:"toolCalls"`
@@ -479,6 +480,7 @@ func topLatencySources(perSpan map[string]SpanStats, top int) []LatencySource {
 func aggregateTotals(totals *TurnBenchTotals, tr *trace.TurnTrace) {
 	totals.InputTokens += tr.Counter(trace.CounterInputTokens)
 	totals.CachedInputTokens += tr.Counter(trace.CounterCachedInputTokens)
+	totals.CacheWriteTokens += tr.Counter(trace.CounterCacheWriteTokens)
 	totals.OutputTokens += tr.Counter(trace.CounterOutputTokens)
 	totals.ModelRequests += tr.Counter(trace.CounterModelRequests)
 	totals.ToolCalls += tr.Counter(trace.CounterToolCalls)
@@ -531,8 +533,9 @@ func FormatTurnBenchSummary(result TurnBenchResult) string {
 			lines = append(lines, fmt.Sprintf("  %-18s %10s  %5.1f%%", src.Span, FormatMetric(src.TotalMs, "ms"), src.Share*100))
 		}
 	}
-	lines = append(lines, fmt.Sprintf("totals: in=%d (cached %d) out=%d | requests=%d tools=%d retries=%d reconnects=%d compactions=%d",
-		result.Totals.InputTokens, result.Totals.CachedInputTokens, result.Totals.OutputTokens,
+	lines = append(lines, fmt.Sprintf("totals: in=%d (cache-read %d, cache-write %d, uncached %d) out=%d | requests=%d tools=%d retries=%d reconnects=%d compactions=%d",
+		result.Totals.InputTokens, result.Totals.CachedInputTokens, result.Totals.CacheWriteTokens,
+		uncachedInputTokens(result.Totals), result.Totals.OutputTokens,
 		result.Totals.ModelRequests, result.Totals.ToolCalls, result.Totals.Retries,
 		result.Totals.Reconnects, result.Totals.Compactions))
 	for _, class := range sortedClasses(result.PerClass) {
@@ -545,6 +548,23 @@ func FormatTurnBenchSummary(result TurnBenchResult) string {
 	return strings.Join(lines, "\n")
 }
 
+func uncachedInputTokens(totals TurnBenchTotals) int64 {
+	remaining := totals.InputTokens
+	if remaining <= 0 {
+		return 0
+	}
+	for _, cached := range []int64{totals.CachedInputTokens, totals.CacheWriteTokens} {
+		if cached <= 0 {
+			continue
+		}
+		if cached >= remaining {
+			return 0
+		}
+		remaining -= cached
+	}
+	return remaining
+}
+
 // classTier returns the oracle tier label a class was classified into, so the
 // per-class roll-up states explicitly which oracle (if any) its "passed" count
 // is measured against.

internal/perfbench/turn_bench_test.go

@@ -74,6 +74,7 @@ func TestRunTurnBenchAggregation(t *testing.T) {
 		"t3": cannedTrace(150, 20, 1500),
 		"t4": cannedTrace(300, 10, 1000),
 	}
+	canned["t1"].Counters = append(canned["t1"].Counters, trace.Counter{Name: trace.CounterCacheWriteTokens, Value: 125})
 	cfg := TurnBenchConfig{
 		Model:      "fake-model",
 		Iterations: 1,
@@ -155,6 +156,9 @@ func TestRunTurnBenchAggregation(t *testing.T) {
 	if result.Totals.InputTokens != 5500 {
 		t.Fatalf("inputTokens = %d, want 5500", result.Totals.InputTokens)
 	}
+	if result.Totals.CacheWriteTokens != 125 {
+		t.Fatalf("cacheWriteTokens = %d, want 125", result.Totals.CacheWriteTokens)
+	}
 	if result.Totals.OutputTokens != 2750 {
 		t.Fatalf("outputTokens = %d, want 2750", result.Totals.OutputTokens)
 	}
@@ -334,6 +338,35 @@ func TestFormatTurnBenchSummaryNamesTopSources(t *testing.T) {
 	}
 }
 
+func TestUncachedInputTokensClampsInconsistentTotals(t *testing.T) {
+	tests := []struct {
+		name   string
+		totals TurnBenchTotals
+		want   int64
+	}{
+		{name: "normal", totals: TurnBenchTotals{InputTokens: 100, CachedInputTokens: 30, CacheWriteTokens: 20}, want: 50},
+		{name: "cached exceeds input", totals: TurnBenchTotals{InputTokens: 100, CachedInputTokens: 120}, want: 0},
+		{name: "write exceeds remainder", totals: TurnBenchTotals{InputTokens: 100, CachedInputTokens: 20, CacheWriteTokens: 90}, want: 0},
+		{name: "overflowing inconsistent counters", totals: TurnBenchTotals{CachedInputTokens: 1<<63 - 1, CacheWriteTokens: 1<<63 - 1}, want: 0},
+		{name: "overflowing counters with input", totals: TurnBenchTotals{InputTokens: 100, CachedInputTokens: 1<<63 - 1, CacheWriteTokens: 1<<63 - 1}, want: 0},
+		{name: "negative cache counters ignored", totals: TurnBenchTotals{InputTokens: 100, CachedInputTokens: -20, CacheWriteTokens: -10}, want: 100},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if got := uncachedInputTokens(test.totals); got != test.want {
+				t.Fatalf("uncachedInputTokens(%+v) = %d, want %d", test.totals, got, test.want)
+			}
+		})
+	}
+	summary := FormatTurnBenchSummary(TurnBenchResult{Totals: TurnBenchTotals{
+		CachedInputTokens: 1<<63 - 1,
+		CacheWriteTokens:  1<<63 - 1,
+	}})
+	if !strings.Contains(summary, "uncached 0") {
+		t.Fatalf("summary did not clamp inconsistent cache totals:\n%s", summary)
+	}
+}
+
 func TestLoadBaselineManifest(t *testing.T) {
 	path := filepath.Join("manifests", "baseline.json")
 	set, err := LoadTaskSet(path)

internal/providermodelcatalog/remote.go

@@ -184,6 +184,10 @@ func parseOpenAIStyleModelList(body []byte) ([]remoteModel, error) {
 
 func ModelsDevProviderID(provider providercatalog.Descriptor) string {
 	switch strings.TrimSpace(provider.ID) {
+	case "chatgpt":
+		// ChatGPT authenticates against the Codex backend, while its public
+		// model metadata is published under the OpenAI provider on models.dev.
+		return "openai"
 	case "dashscope":
 		return "alibaba"
 	case "github":

internal/providermodelcatalog/remote_test.go

@@ -241,6 +241,7 @@ func TestPublicLiveCatalog(t *testing.T) {
 
 func TestModelsDevProviderIDMapsZeroAliases(t *testing.T) {
 	tests := map[string]string{
+		"chatgpt":      "openai",
 		"github":       "github-models",
 		"moonshot":     "moonshotai",
 		"nvidia-nim":   "nvidia",

internal/providermodeldiscovery/discovery.go

@@ -539,7 +539,8 @@ func mergeLiveModels(provider providercatalog.Descriptor, liveModels []Model, ca
 	hasCatalog := len(byID) > 0
 	// Aggregators publish the live list as the source of truth. Keep live-only
 	// ids even when a remote catalog also loaded, instead of intersecting.
-	preferLive := providermodelcatalog.PublicLiveCatalog(provider.ID) ||
+	preferLive := provider.Local ||
+		providermodelcatalog.PublicLiveCatalog(provider.ID) ||
 		providercatalog.NormalizeID(provider.ID) == "chatgpt"
 	result := make([]Model, 0, len(liveModels))
 	for _, live := range liveModels {

internal/providermodeldiscovery/discovery_test.go

@@ -139,6 +139,68 @@ func TestMergeChatGPTModelsKeepsLiveOnlyEntries(t *testing.T) {
 	}
 }
 
+func TestDiscoverCatalogChatGPTMergesOpenAIModelsDevMetadata(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/api.json":
+			_, _ = w.Write([]byte(`{
+				"openai": {"models": {
+					"gpt-5.6-sol": {
+						"id": "gpt-5.6-sol",
+						"name": "GPT-5.6 Sol",
+						"description": "Frontier coding model",
+						"tool_call": true,
+						"reasoning": true,
+						"reasoning_efforts": ["low", "high", "max"],
+						"limit": {"context": 1050000},
+						"modalities": {"input": ["text", "image", "pdf"], "output": ["text"]}
+					}
+				}}
+			}`))
+		case "/backend-api/codex/models":
+			_, _ = w.Write([]byte(`{"data":[{"id":"gpt-5.6-sol"}]}`))
+		default:
+			t.Errorf("unexpected request path %q", r.URL.Path)
+			http.NotFound(w, r)
+			return
+		}
+	}))
+	defer server.Close()
+
+	provider, ok := providercatalog.Get("chatgpt")
+	if !ok {
+		t.Fatal("ChatGPT provider missing from catalog")
+	}
+	models, err := DiscoverCatalog(context.Background(), provider, config.ProviderProfile{
+		Name:         "chatgpt",
+		CatalogID:    "chatgpt",
+		ProviderKind: config.ProviderKindOpenAICompatible,
+		BaseURL:      server.URL + "/backend-api/codex",
+	}, Options{
+		HTTPClient:   server.Client(),
+		ModelsDevURL: server.URL + "/api.json",
+		OAuthResolver: func(context.Context, bool) (string, string, bool, error) {
+			return "Authorization", "Bearer test", true, nil
+		},
+	})
+	if err != nil {
+		t.Fatalf("DiscoverCatalog returned error: %v", err)
+	}
+	if len(models) != 1 {
+		t.Fatalf("models = %#v, want one ChatGPT live model", models)
+	}
+	model := models[0]
+	if model.ID != "gpt-5.6-sol" || model.ContextWindow != 1050000 || !model.ToolCall || !model.Reasoning {
+		t.Fatalf("merged ChatGPT model = %#v, want models.dev metadata", model)
+	}
+	if got := strings.Join(model.InputModalities, ","); got != "text,image,pdf" {
+		t.Fatalf("input modalities = %q, want text,image,pdf", got)
+	}
+	if got := strings.Join(model.ReasoningEfforts, ","); got != "low,high,max" {
+		t.Fatalf("reasoning efforts = %q, want low,high,max", got)
+	}
+}
+
 func TestMergeLiveModelsUsesLiveDefaultsAndReasoningCapability(t *testing.T) {
 	models := mergeLiveModels(
 		providercatalog.Descriptor{ID: "chatgpt"},
@@ -164,6 +226,29 @@ func TestMergeLiveModelsUsesLiveDefaultsAndReasoningCapability(t *testing.T) {
 	}
 }
 
+func TestMergeLocalModelsKeepsLiveOnlyEntries(t *testing.T) {
+	models := mergeLiveModels(
+		providercatalog.Descriptor{ID: "lmstudio", Local: true},
+		[]Model{
+			{ID: "qwen3-coder-30b", ContextWindow: 32768},
+			{ID: "text-embedding-local"},
+			{ID: "qwen2.5-coder-32b-instruct", Description: "live description"},
+		},
+		[]Model{{ID: "qwen2.5-coder-32b-instruct", Description: "catalog description", ToolCall: true}},
+	)
+
+	if got, want := strings.Join(modelIDs(models), ","), "qwen3-coder-30b,qwen2.5-coder-32b-instruct"; got != want {
+		t.Fatalf("models = %q, want %q", got, want)
+	}
+	for _, model := range models {
+		if model.ID == "qwen2.5-coder-32b-instruct" {
+			if model.Description != "catalog description" || !model.ToolCall {
+				t.Fatalf("merged catalog metadata = %#v", model)
+			}
+		}
+	}
+}
+
 func TestDiscoverCatalogOpenGatewayUsesLiveListWithoutKey(t *testing.T) {
 	// Catalog and live endpoints return distinct payloads so the merge must keep
 	// live-only ids that are absent from the remote catalog response.

internal/providers/openai/codex_responses.go

@@ -62,6 +62,7 @@ const (
 	responsesEventReasoningDelta    = "response.reasoning_summary_text.delta"
 	responsesEventOutputTextDone    = "response.output_text.done"
 	responsesEventFunctionArgsDelta = "response.function_call_arguments.delta"
+	responsesEventCustomInputDelta  = "response.custom_tool_call_input.delta"
 	responsesEventContentPartDone   = "response.content_part.done"
 	responsesEventOutputItemDone    = "response.output_item.done"
 	responsesEventCompleted         = "response.completed"
@@ -70,17 +71,37 @@ const (
 	responsesEventIncomplete        = "response.incomplete"
 )
 
+const applyPatchLarkGrammar = `start: begin_patch hunk+ end_patch
+begin_patch: "*** Begin Patch" LF
+end_patch: "*** End Patch" LF?
+hunk: add_hunk | delete_hunk | update_hunk
+add_hunk: "*** Add File: " filename LF add_line+
+delete_hunk: "*** Delete File: " filename LF
+update_hunk: "*** Update File: " filename LF change_move? change?
+filename: /(.+)/
+add_line: "+" /(.*)/ LF -> line
+change_move: "*** Move to: " filename LF
+change: (change_context | change_line)+ eof_line?
+change_context: ("@@" | "@@ " /(.+)/) LF
+change_line: ("+" | "-" | " ") /(.*)/ LF
+eof_line: "*** End of File" LF
+%import common.LF`
+
 // responsesRequest is the wire shape POSTed to {baseURL}/responses.
 type responsesRequest struct {
-	Model           string              `json:"model"`
-	Instructions    string              `json:"instructions"`
-	Input           []inputItem         `json:"input"`
-	Stream          bool                `json:"stream"`
-	Store           bool                `json:"store"`
-	MaxOutputTokens int                 `json:"max_output_tokens,omitempty"`
-	Tools           []responsesTool     `json:"tools,omitempty"`
-	Reasoning       *responsesReasoning `json:"reasoning,omitempty"`
-	ServiceTier     string              `json:"service_tier,omitempty"`
+	Type               string              `json:"type,omitempty"`
+	Model              string              `json:"model"`
+	Instructions       string              `json:"instructions"`
+	PreviousResponseID string              `json:"previous_response_id,omitempty"`
+	Input              []inputItem         `json:"input"`
+	Stream             bool                `json:"stream"`
+	Store              bool                `json:"store"`
+	ParallelToolCalls  bool                `json:"parallel_tool_calls"`
+	MaxOutputTokens    int                 `json:"max_output_tokens,omitempty"`
+	Tools              []responsesTool     `json:"tools,omitempty"`
+	Reasoning          *responsesReasoning `json:"reasoning,omitempty"`
+	ServiceTier        string              `json:"service_tier,omitempty"`
+	PromptCacheKey     string              `json:"prompt_cache_key,omitempty"`
 }
 
 // responsesReasoning carries the reasoning controls for the Responses API. The
@@ -105,6 +126,7 @@ type inputItem struct {
 	CallID    string `json:"call_id,omitempty"`
 	Name      string `json:"name,omitempty"`
 	Arguments string `json:"arguments,omitempty"`
+	Input     string `json:"input,omitempty"`
 	// function_call_output fields
 	Output any `json:"output,omitempty"`
 }
@@ -118,10 +140,11 @@ type contentItem struct {
 }
 
 type responsesTool struct {
-	Type        string         `json:"type"`
-	Name        string         `json:"name"`
-	Description string         `json:"description,omitempty"`
-	Parameters  map[string]any `json:"parameters,omitempty"`
+	Type        string                            `json:"type"`
+	Name        string                            `json:"name"`
+	Description string                            `json:"description,omitempty"`
+	Parameters  map[string]any                    `json:"parameters,omitempty"`
+	Format      *zeroruntime.ToolDefinitionFormat `json:"format,omitempty"`
 }
 
 // responsesEvent is the decoded form of one Responses SSE data payload.
@@ -132,6 +155,7 @@ type responsesEvent struct {
 	Delta string `json:"delta,omitempty"`
 	// item payloads (response.output_item.added / done)
 	ItemID string `json:"item_id,omitempty"`
+	CallID string `json:"call_id,omitempty"`
 	// OutputIndex is a *int so a real 0 (the first output) is distinguishable from
 	// "absent" — a plain int defaulting to 0 dropped a no-item_id call's args (M1).
 	OutputIndex *int         `json:"output_index,omitempty"`
@@ -150,6 +174,7 @@ type itemPayload struct {
 	CallID    string `json:"call_id,omitempty"`
 	Name      string `json:"name,omitempty"`
 	Arguments string `json:"arguments,omitempty"`
+	Input     string `json:"input,omitempty"`
 	Status    string `json:"status,omitempty"`
 }
 
@@ -173,7 +198,8 @@ type outputDetails struct {
 }
 
 type inputDetails struct {
-	CachedTokens int `json:"cached_tokens"`
+	CachedTokens     int `json:"cached_tokens"`
+	CacheWriteTokens int `json:"cache_write_tokens"`
 }
 
 type errorPayload struct {
@@ -187,8 +213,10 @@ type errorPayload struct {
 // response.output_item.done.
 type toolCallBuilder struct {
 	ID        string
+	CallID    string
 	Name      string
 	Arguments strings.Builder
+	Freeform  bool
 	started   bool
 	ended     bool
 }
@@ -197,15 +225,57 @@ type toolCallBuilder struct {
 // event has been emitted. It is the Responses-API equivalent of the
 // chat-completions toolState in provider.go.
 type responsesState struct {
-	toolCalls map[string]*toolCallBuilder
-	usage     *usagePayload
-	done      bool
+	toolCalls  map[string]*toolCallBuilder
+	toolOrder  []string
+	text       strings.Builder
+	responseID string
+	usage      *usagePayload
+	emitted    bool
+	done       bool
 }
 
 func newResponsesState() *responsesState {
 	return &responsesState{toolCalls: map[string]*toolCallBuilder{}}
 }
 
+func (state *responsesState) outputInputItems() []inputItem {
+	items := make([]inputItem, 0, len(state.toolOrder)+1)
+	if state.text.Len() > 0 {
+		items = append(items, inputItem{
+			Type:    "message",
+			Role:    "assistant",
+			Content: []contentItem{{Type: "output_text", Text: state.text.String()}},
+		})
+	}
+	for _, key := range state.toolOrder {
+		builder := state.toolCalls[key]
+		if builder == nil || builder.ID == "" || builder.Name == "" {
+			continue
+		}
+		callID := builder.CallID
+		if callID == "" {
+			callID = builder.ID
+		}
+		itemType := "function_call"
+		if builder.Freeform {
+			itemType = "custom_tool_call"
+		}
+		item := inputItem{
+			Type:   itemType,
+			ID:     builder.ID,
+			CallID: callID,
+			Name:   builder.Name,
+		}
+		if builder.Freeform {
+			item.Input = builder.Arguments.String()
+		} else {
+			item.Arguments = builder.Arguments.String()
+		}
+		items = append(items, item)
+	}
+	return items
+}
+
 // buildResponsesRequest converts a runtime CompletionRequest into the
 // Responses API wire format. System messages fold into a top-level
 // `instructions` field; everything else (user/assistant turns, tool
@@ -215,11 +285,14 @@ func (p *CodexProvider) buildResponsesRequest(request zeroruntime.CompletionRequ
 		return nil, errors.New("codex provider: model is required")
 	}
 	req := &responsesRequest{
-		Model:           p.inner.model,
-		Stream:          true,
-		MaxOutputTokens: p.inner.maxTokens,
+		Model:             p.inner.model,
+		Stream:            true,
+		ParallelToolCalls: true,
+		MaxOutputTokens:   p.inner.maxTokens,
+		PromptCacheKey:    request.PromptCacheKey,
 	}
 	instructions := []string{}
+	customCallIDs := map[string]string{}
 	for _, msg := range request.Messages {
 		switch msg.Role {
 		case zeroruntime.MessageRoleSystem:
@@ -234,13 +307,31 @@ func (p *CodexProvider) buildResponsesRequest(request zeroruntime.CompletionRequ
 				return nil, err
 			}
 			req.Input = append(req.Input, items...)
+			for _, call := range msg.ToolCalls {
+				if call.Freeform && call.ID != "" {
+					callID := call.ProviderCallID
+					if callID == "" {
+						callID = call.ID
+					}
+					customCallIDs[call.ID] = callID
+				}
+			}
 		case zeroruntime.MessageRoleTool:
 			if msg.ToolCallID == "" {
 				return nil, fmt.Errorf("codex provider: tool message missing tool call id")
 			}
+			outputType := "function_call_output"
+			callID := msg.ToolCallProviderID
+			if callID == "" {
+				callID = msg.ToolCallID
+			}
+			if customID, custom := customCallIDs[msg.ToolCallID]; custom {
+				outputType = "custom_tool_call_output"
+				callID = customID
+			}
 			req.Input = append(req.Input, inputItem{
-				Type:   "function_call_output",
-				CallID: msg.ToolCallID,
+				Type:   outputType,
+				CallID: callID,
 				Output: msg.Content,
 			})
 		default:
@@ -249,12 +340,25 @@ func (p *CodexProvider) buildResponsesRequest(request zeroruntime.CompletionRequ
 	}
 	req.Instructions = strings.Join(instructions, "\n\n")
 	for _, tool := range request.Tools {
-		req.Tools = append(req.Tools, responsesTool{
-			Type:        "function",
-			Name:        tool.Name,
-			Description: tool.Description,
-			Parameters:  tool.Parameters,
-		})
+		definition := tool
+		if definition.Name == "apply_patch" && definition.Type == zeroruntime.ToolDefinitionFreeform {
+			definition.Description = "The apply_patch tool edits files from a raw structured patch. Use absolute file paths in patch headers to target a granted extra write root. Do not wrap the patch in JSON."
+			definition.Format = &zeroruntime.ToolDefinitionFormat{Type: "grammar", Syntax: "lark", Definition: applyPatchLarkGrammar}
+		}
+		wireTool := responsesTool{
+			Type:        string(definition.Type),
+			Name:        definition.Name,
+			Description: definition.Description,
+			Parameters:  definition.Parameters,
+			Format:      definition.Format,
+		}
+		if wireTool.Type == "" {
+			wireTool.Type = string(zeroruntime.ToolDefinitionFunction)
+		}
+		if wireTool.Type == string(zeroruntime.ToolDefinitionFreeform) {
+			wireTool.Parameters = nil
+		}
+		req.Tools = append(req.Tools, wireTool)
 	}
 	// Codex / o-series reasoning models take the effort tier nested under
 	// `reasoning` on the Responses API (the chat-completions `reasoning_effort`
@@ -312,13 +416,26 @@ func (p *CodexProvider) assistantInputItems(msg zeroruntime.Message) ([]inputIte
 		if tc.Name == "" {
 			return nil, errors.New("codex provider: assistant tool call missing name")
 		}
-		items = append(items, inputItem{
-			Type:      "function_call",
-			ID:        tc.ID,
-			CallID:    tc.ID,
-			Name:      tc.Name,
-			Arguments: tc.Arguments,
-		})
+		callID := tc.ProviderCallID
+		if callID == "" {
+			callID = tc.ID
+		}
+		itemType := "function_call"
+		if tc.Freeform {
+			itemType = "custom_tool_call"
+		}
+		item := inputItem{
+			Type:   itemType,
+			ID:     tc.ID,
+			CallID: callID,
+			Name:   tc.Name,
+		}
+		if tc.Freeform {
+			item.Input = tc.Arguments
+		} else {
+			item.Arguments = tc.Arguments
+		}
+		items = append(items, item)
 	}
 	return items, nil
 }
@@ -479,6 +596,18 @@ func (p *CodexProvider) emitResponsesEvent(
 		state.done = true
 		return false
 	}
+	return p.emitParsedResponsesEvent(ctx, &event, state, events)
+}
+
+// emitParsedResponsesEvent converts one already-decoded Responses event into
+// zero or more runtime events. WebSocket sessions use this path to avoid
+// decoding each frame twice; the SSE path retains emitResponsesEvent above.
+func (p *CodexProvider) emitParsedResponsesEvent(
+	ctx context.Context,
+	event *responsesEvent,
+	state *responsesState,
+	events chan<- zeroruntime.StreamEvent,
+) bool {
 	if event.Type == "" {
 		// A payload that parses as JSON but carries no `type` field is a
 		// malformed Responses event — the type is the discriminator that
@@ -500,12 +629,17 @@ func (p *CodexProvider) emitResponsesEvent(
 		// the runtime. response.incomplete is folded into a length finish at
 		// scan-end (state.done stays false so the wrapper emits the
 		// StreamEventDone with FinishReasonLength).
+		if event.Response != nil && event.Response.ID != "" {
+			state.responseID = event.Response.ID
+		}
 		return true
 	case responsesEventOutputItemAdded:
-		p.handleOutputItemAdded(ctx, &event, state, events)
+		p.handleOutputItemAdded(ctx, event, state, events)
 		return true
 	case responsesEventOutputTextDelta:
 		if event.Delta != "" {
+			state.emitted = true
+			state.text.WriteString(event.Delta)
 			providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
 				Type:    zeroruntime.StreamEventText,
 				Content: event.Delta,
@@ -517,6 +651,7 @@ func (p *CodexProvider) emitResponsesEvent(
 		// phase shows progress (and keeps the activity clock fresh) instead of
 		// looking like a hang. Requested via reasoning.summary="auto".
 		if event.Delta != "" {
+			state.emitted = true
 			providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
 				Type:    zeroruntime.StreamEventReasoning,
 				Content: event.Delta,
@@ -524,13 +659,16 @@ func (p *CodexProvider) emitResponsesEvent(
 		}
 		return true
 	case responsesEventFunctionArgsDelta:
-		p.handleFunctionArgsDelta(ctx, &event, state, events)
+		p.handleToolInputDelta(ctx, event, state, events, false)
+		return true
+	case responsesEventCustomInputDelta:
+		p.handleToolInputDelta(ctx, event, state, events, true)
 		return true
 	case responsesEventOutputItemDone:
-		p.handleOutputItemDone(ctx, &event, state, events)
+		p.handleOutputItemDone(ctx, event, state, events)
 		return true
 	case responsesEventCompleted, responsesEventFailed:
-		return p.handleTerminalResponse(ctx, &event, state, events)
+		return p.handleTerminalResponse(ctx, event, state, events)
 	case responsesEventError:
 		message := event.Message
 		if event.Code != "" {
@@ -570,22 +708,38 @@ func (p *CodexProvider) handleOutputItemAdded(
 		return
 	}
 	switch event.Item.Type {
-	case "function_call":
+	case "function_call", "custom_tool_call":
 		key := p.toolCallKey(event)
 		if key == "" {
 			return
 		}
-		builder := &toolCallBuilder{
-			ID:   key,
-			Name: event.Item.Name,
+		builder, exists := state.toolCalls[key]
+		if !exists {
+			builder = &toolCallBuilder{ID: key, Freeform: event.Item.Type == "custom_tool_call"}
+			state.toolCalls[key] = builder
+			state.toolOrder = append(state.toolOrder, key)
+		}
+		if event.Item.CallID != "" {
+			builder.CallID = event.Item.CallID
+		}
+		if event.Item.Name != "" {
+			builder.Name = event.Item.Name
+		}
+		builder.Freeform = builder.Freeform || event.Item.Type == "custom_tool_call"
+		if builder.Freeform && event.Item.Input != "" && builder.Arguments.Len() == 0 {
+			builder.Arguments.WriteString(event.Item.Input)
+		}
+		state.emitted = true
+		if !builder.started {
+			providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
+				Type:               zeroruntime.StreamEventToolCallStart,
+				ToolCallID:         key,
+				ToolCallProviderID: builder.CallID,
+				ToolName:           builder.Name,
+				ToolCallFreeform:   builder.Freeform,
+			})
+			builder.started = true
 		}
-		state.toolCalls[key] = builder
-		providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
-			Type:       zeroruntime.StreamEventToolCallStart,
-			ToolCallID: key,
-			ToolName:   event.Item.Name,
-		})
-		builder.started = true
 	}
 }
 
@@ -593,11 +747,12 @@ func (p *CodexProvider) handleOutputItemAdded(
 // to the in-flight builder and emits StreamEventToolCallDelta. The
 // Codex backend uses either `item_id` or `output_index` to attribute
 // the delta; we honor both.
-func (p *CodexProvider) handleFunctionArgsDelta(
+func (p *CodexProvider) handleToolInputDelta(
 	ctx context.Context,
 	event *responsesEvent,
 	state *responsesState,
 	events chan<- zeroruntime.StreamEvent,
+	freeform bool,
 ) {
 	key := p.toolCallKey(event)
 	if key == "" {
@@ -610,10 +765,16 @@ func (p *CodexProvider) handleFunctionArgsDelta(
 		// an intermediate proxy). Treat the delta as the start of a new
 		// tool call with no known name yet — the eventual
 		// response.output_item.done carries the final name.
-		builder = &toolCallBuilder{ID: key}
+		builder = &toolCallBuilder{ID: key, Freeform: freeform}
 		state.toolCalls[key] = builder
+		state.toolOrder = append(state.toolOrder, key)
+	}
+	builder.Freeform = builder.Freeform || freeform
+	if event.CallID != "" && builder.CallID == "" {
+		builder.CallID = event.CallID
 	}
 	builder.Arguments.WriteString(event.Delta)
+	state.emitted = true
 	providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
 		Type:              zeroruntime.StreamEventToolCallDelta,
 		ToolCallID:        key,
@@ -632,7 +793,7 @@ func (p *CodexProvider) handleOutputItemDone(
 	state *responsesState,
 	events chan<- zeroruntime.StreamEvent,
 ) {
-	if event.Item == nil || event.Item.Type != "function_call" {
+	if event.Item == nil || (event.Item.Type != "function_call" && event.Item.Type != "custom_tool_call") {
 		return
 	}
 	key := p.toolCallKey(event)
@@ -641,20 +802,31 @@ func (p *CodexProvider) handleOutputItemDone(
 	}
 	builder, ok := state.toolCalls[key]
 	if !ok {
-		builder = &toolCallBuilder{ID: key}
+		builder = &toolCallBuilder{ID: key, Freeform: event.Item.Type == "custom_tool_call"}
 		state.toolCalls[key] = builder
+		state.toolOrder = append(state.toolOrder, key)
 	}
 	if event.Item.Name != "" {
 		builder.Name = event.Item.Name
 	}
-	if event.Item.Arguments != "" && builder.Arguments.Len() == 0 {
-		builder.Arguments.WriteString(event.Item.Arguments)
+	if event.Item.CallID != "" {
+		builder.CallID = event.Item.CallID
+	}
+	builder.Freeform = builder.Freeform || event.Item.Type == "custom_tool_call"
+	finalInput := event.Item.Arguments
+	if builder.Freeform {
+		finalInput = event.Item.Input
+	}
+	if finalInput != "" && builder.Arguments.Len() == 0 {
+		builder.Arguments.WriteString(finalInput)
 	}
 	if !builder.started {
 		providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
-			Type:       zeroruntime.StreamEventToolCallStart,
-			ToolCallID: key,
-			ToolName:   builder.Name,
+			Type:               zeroruntime.StreamEventToolCallStart,
+			ToolCallID:         key,
+			ToolCallProviderID: builder.CallID,
+			ToolName:           builder.Name,
+			ToolCallFreeform:   builder.Freeform,
 		})
 		builder.started = true
 	}
@@ -664,6 +836,7 @@ func (p *CodexProvider) handleOutputItemDone(
 		ToolName:   builder.Name,
 	})
 	builder.ended = true
+	state.emitted = true
 }
 
 // handleTerminalResponse emits the final usage + done event for a
@@ -693,6 +866,7 @@ func (p *CodexProvider) handleTerminalResponse(
 		return false
 	}
 	state.usage = event.Response.Usage
+	state.responseID = event.Response.ID
 	if event.Response.Usage != nil {
 		usage := zeroruntime.Usage{
 			InputTokens:  event.Response.Usage.InputTokens,
@@ -700,6 +874,7 @@ func (p *CodexProvider) handleTerminalResponse(
 		}
 		if event.Response.Usage.InputTokensDetails != nil {
 			usage.CachedInputTokens = event.Response.Usage.InputTokensDetails.CachedTokens
+			usage.CacheWriteTokens = event.Response.Usage.InputTokensDetails.CacheWriteTokens
 		}
 		if event.Response.Usage.OutputTokensDetails != nil {
 			usage.ReasoningTokens = event.Response.Usage.OutputTokensDetails.ReasoningTokens
@@ -735,7 +910,7 @@ func (p *CodexProvider) handleTerminalResponse(
 		state.done = true
 		return false
 	}
-	providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{Type: zeroruntime.StreamEventDone})
+	providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{Type: zeroruntime.StreamEventDone, ResponseID: event.Response.ID})
 	state.done = true
 	return false
 }
@@ -754,6 +929,9 @@ func (p *CodexProvider) toolCallKey(event *responsesEvent) string {
 	if event.Item != nil && event.Item.CallID != "" {
 		return event.Item.CallID
 	}
+	if event.CallID != "" {
+		return event.CallID
+	}
 	if event.OutputIndex != nil {
 		// output_index is present (a *int distinguishes a real 0 — the first output
 		// in the response — from "absent"), so key on it even when 0 instead of

internal/providers/openai/codex_session.go

@@ -0,0 +1,421 @@
+package openai
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/url"
+	"reflect"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/coder/websocket"
+
+	"github.com/Gitlawb/zero/internal/providers/providerio"
+	"github.com/Gitlawb/zero/internal/trace"
+	"github.com/Gitlawb/zero/internal/zeroruntime"
+)
+
+const (
+	responsesWebSocketBetaHeader = "OpenAI-Beta"
+	responsesWebSocketBetaValue  = "responses_websockets=2026-02-06"
+	responsesWebSocketRequest    = "response.create"
+	previousResponseNotFoundCode = "previous_response_not_found"
+	webSocketConnectionLimitCode = "websocket_connection_limit_reached"
+	responsesWebSocketReadLimit  = 16 << 20
+)
+
+var errCodexTurnSessionBusy = errors.New("codex turn session already has an active stream")
+
+// NewCodexTurnSessionProvider enables one Responses WebSocket connection for
+// each agent run. The session falls back to the existing HTTP/SSE provider when
+// the endpoint cannot upgrade or loses its response chain.
+func NewCodexTurnSessionProvider(provider *CodexProvider, caps zeroruntime.ProviderCapabilities) zeroruntime.TurnSessionProvider {
+	return &codexTurnSessionProvider{provider: provider, caps: caps}
+}
+
+type codexTurnSessionProvider struct {
+	provider *CodexProvider
+	caps     zeroruntime.ProviderCapabilities
+}
+
+func (provider *codexTurnSessionProvider) OpenTurnSession(ctx context.Context) (zeroruntime.TurnSession, error) {
+	if provider == nil || provider.provider == nil || provider.provider.inner == nil {
+		return nil, errors.New("codex turn session requires a provider")
+	}
+	sessionCtx, cancel := context.WithCancel(ctx)
+	return &codexTurnSession{
+		ctx:         sessionCtx,
+		cancel:      cancel,
+		provider:    provider.provider,
+		prewarmDone: make(chan struct{}),
+	}, nil
+}
+
+func (provider *codexTurnSessionProvider) Capabilities() zeroruntime.ProviderCapabilities {
+	return provider.caps
+}
+
+type codexTurnSession struct {
+	ctx      context.Context
+	cancel   context.CancelFunc
+	provider *CodexProvider
+
+	mu             sync.Mutex
+	connection     *websocket.Conn
+	webSocketOff   bool
+	lastRequest    *responsesRequest
+	lastResponseID string
+	lastOutput     []inputItem
+	streamActive   bool
+
+	prewarmOnce sync.Once
+	prewarmDone chan struct{}
+	closeOnce   sync.Once
+}
+
+// Prewarm starts the WebSocket handshake without blocking prompt assembly. The
+// first Stream waits for this bounded attempt; failure simply selects HTTP/SSE.
+func (session *codexTurnSession) Prewarm(ctx context.Context) error {
+	session.prewarmOnce.Do(func() {
+		go func() {
+			defer close(session.prewarmDone)
+			prewarmCtx, cancel := context.WithTimeout(session.ctx, prewarmTimeout)
+			defer cancel()
+			recorder := trace.FromContext(ctx)
+			span := recorder.Span(trace.SpanProviderPrewarm)
+			defer span.End()
+			recorder.Counter(trace.CounterPrewarmAttempts, 1)
+			connection, err := session.provider.dialResponsesWebSocket(prewarmCtx)
+			session.mu.Lock()
+			defer session.mu.Unlock()
+			if err != nil {
+				session.webSocketOff = true
+				return
+			}
+			session.connection = connection
+		}()
+	})
+	return nil
+}
+
+func (session *codexTurnSession) Stream(ctx context.Context, request zeroruntime.CompletionRequest) (<-chan zeroruntime.StreamEvent, error) {
+	_ = session.Prewarm(ctx)
+	select {
+	case <-session.prewarmDone:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+
+	fullRequest, err := session.provider.buildResponsesRequest(request)
+	if err != nil {
+		return nil, err
+	}
+
+	session.mu.Lock()
+	if session.streamActive {
+		session.mu.Unlock()
+		return nil, errCodexTurnSessionBusy
+	}
+	if session.webSocketOff || session.connection == nil {
+		session.mu.Unlock()
+		trace.FromContext(ctx).Counter(trace.CounterResponsesHTTPFallback, 1)
+		return session.provider.StreamCompletion(ctx, request)
+	}
+	session.streamActive = true
+	connection := session.connection
+	wireRequest := *fullRequest
+	wireRequest.Type = responsesWebSocketRequest
+	if delta, ok := responseInputDelta(session.lastRequest, session.lastOutput, fullRequest); ok && session.lastResponseID != "" {
+		wireRequest.PreviousResponseID = session.lastResponseID
+		wireRequest.Input = delta
+		trace.FromContext(ctx).Counter(trace.CounterResponseChainReused, 1)
+	} else if session.lastRequest != nil {
+		trace.FromContext(ctx).Counter(trace.CounterResponseChainReset, 1)
+		session.lastRequest = nil
+		session.lastResponseID = ""
+		session.lastOutput = nil
+	}
+	session.mu.Unlock()
+
+	body, err := json.Marshal(wireRequest)
+	if err != nil {
+		session.releaseStream()
+		return nil, fmt.Errorf("encode codex websocket request: %w", err)
+	}
+	events := make(chan zeroruntime.StreamEvent, 16)
+	go func() {
+		defer close(events)
+		defer session.releaseStream()
+		session.streamWebSocket(ctx, connection, body, fullRequest, request, events)
+	}()
+	return events, nil
+}
+
+func (session *codexTurnSession) releaseStream() {
+	session.mu.Lock()
+	session.streamActive = false
+	session.mu.Unlock()
+}
+
+func (session *codexTurnSession) Compact(context.Context, zeroruntime.CompletionRequest) ([]zeroruntime.Message, error) {
+	return nil, zeroruntime.ErrCompactionUnsupported
+}
+
+func (session *codexTurnSession) Close() error {
+	session.closeOnce.Do(func() {
+		session.cancel()
+		session.prewarmOnce.Do(func() { close(session.prewarmDone) })
+		select {
+		case <-session.prewarmDone:
+		case <-time.After(prewarmTimeout):
+		}
+		session.mu.Lock()
+		connection := session.connection
+		session.connection = nil
+		session.webSocketOff = true
+		session.mu.Unlock()
+		if connection != nil {
+			_ = connection.CloseNow()
+		}
+	})
+	return nil
+}
+
+func responseInputDelta(previous *responsesRequest, output []inputItem, current *responsesRequest) ([]inputItem, bool) {
+	if previous == nil || current == nil || !responsesRequestPropertiesEqual(previous, current) {
+		return nil, false
+	}
+	prefix := make([]inputItem, 0, len(previous.Input)+len(output))
+	prefix = append(prefix, previous.Input...)
+	prefix = append(prefix, output...)
+	if len(current.Input) <= len(prefix) || !reflect.DeepEqual(current.Input[:len(prefix)], prefix) {
+		return nil, false
+	}
+	return append([]inputItem(nil), current.Input[len(prefix):]...), true
+}
+
+func responsesRequestPropertiesEqual(left, right *responsesRequest) bool {
+	return left.Model == right.Model &&
+		left.Instructions == right.Instructions &&
+		left.Stream == right.Stream &&
+		left.Store == right.Store &&
+		left.ParallelToolCalls == right.ParallelToolCalls &&
+		left.MaxOutputTokens == right.MaxOutputTokens &&
+		reflect.DeepEqual(left.Tools, right.Tools) &&
+		reflect.DeepEqual(left.Reasoning, right.Reasoning) &&
+		left.ServiceTier == right.ServiceTier &&
+		left.PromptCacheKey == right.PromptCacheKey
+}
+
+func (session *codexTurnSession) streamWebSocket(
+	ctx context.Context,
+	connection *websocket.Conn,
+	body []byte,
+	fullRequest *responsesRequest,
+	runtimeRequest zeroruntime.CompletionRequest,
+	events chan<- zeroruntime.StreamEvent,
+) {
+	if err := connection.Write(ctx, websocket.MessageText, body); err != nil {
+		session.disableWebSocket(connection)
+		session.forwardHTTP(ctx, runtimeRequest, events)
+		return
+	}
+
+	state := newResponsesState()
+	for {
+		readCtx := ctx
+		cancel := func() {}
+		idleTimeout := session.provider.inner.streamIdleTimeout
+		if idleTimeout > 0 {
+			readCtx, cancel = context.WithTimeout(ctx, idleTimeout)
+		}
+		messageType, data, err := connection.Read(readCtx)
+		readTimedOut := errors.Is(readCtx.Err(), context.DeadlineExceeded) && ctx.Err() == nil
+		cancel()
+		if err != nil {
+			session.disableWebSocket(connection)
+			if ctx.Err() != nil {
+				return
+			}
+			if !state.emitted {
+				session.forwardHTTP(ctx, runtimeRequest, events)
+				return
+			}
+			errorMessage := err.Error()
+			if readTimedOut {
+				errorMessage = providerio.StreamTimeoutMessage(providerio.ErrStreamIdle, idleTimeout)
+			}
+			providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
+				Type:  zeroruntime.StreamEventError,
+				Error: session.provider.redact("provider stream error: " + errorMessage),
+			})
+			return
+		}
+		if messageType != websocket.MessageText {
+			continue
+		}
+
+		var responseEvent responsesEvent
+		decodeErr := json.Unmarshal(data, &responseEvent)
+		if decodeErr == nil {
+			if (responseEvent.Code == previousResponseNotFoundCode || responseEvent.Code == webSocketConnectionLimitCode) &&
+				!state.emitted {
+				session.disableWebSocket(connection)
+				session.forwardHTTP(ctx, runtimeRequest, events)
+				return
+			}
+			if responseEvent.Type == responsesEventIncomplete {
+				session.resetResponseChain(connection)
+				providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
+					Type:         zeroruntime.StreamEventDone,
+					FinishReason: zeroruntime.FinishReasonLength,
+				})
+				return
+			}
+		}
+
+		keepReading := false
+		if decodeErr == nil {
+			keepReading = session.provider.emitParsedResponsesEvent(ctx, &responseEvent, state, events)
+		} else {
+			keepReading = session.provider.emitResponsesEvent(ctx, string(data), state, events)
+		}
+		if keepReading {
+			continue
+		}
+		if responseEvent.Type == responsesEventCompleted && responseEvent.Response != nil &&
+			responseEvent.Response.Error == nil && responseEvent.Response.Status != "failed" && state.responseID != "" {
+			session.mu.Lock()
+			if session.connection == connection && !session.webSocketOff {
+				requestCopy := *fullRequest
+				requestCopy.Input = append([]inputItem(nil), fullRequest.Input...)
+				session.lastRequest = &requestCopy
+				session.lastResponseID = state.responseID
+				session.lastOutput = state.outputInputItems()
+			}
+			session.mu.Unlock()
+		}
+		return
+	}
+}
+
+func (session *codexTurnSession) resetResponseChain(connection *websocket.Conn) {
+	session.mu.Lock()
+	defer session.mu.Unlock()
+	if session.connection != connection {
+		return
+	}
+	session.lastRequest = nil
+	session.lastResponseID = ""
+	session.lastOutput = nil
+}
+
+func (session *codexTurnSession) forwardHTTP(ctx context.Context, request zeroruntime.CompletionRequest, events chan<- zeroruntime.StreamEvent) {
+	trace.FromContext(ctx).Counter(trace.CounterResponsesHTTPFallback, 1)
+	stream, err := session.provider.StreamCompletion(ctx, request)
+	if err != nil {
+		providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
+			Type:  zeroruntime.StreamEventError,
+			Error: session.provider.redact(err.Error()),
+		})
+		return
+	}
+	for event := range stream {
+		providerio.SendEvent(ctx, events, event)
+	}
+}
+
+func (session *codexTurnSession) disableWebSocket(connection *websocket.Conn) {
+	session.mu.Lock()
+	if session.connection == connection {
+		session.connection = nil
+		session.webSocketOff = true
+		session.lastRequest = nil
+		session.lastResponseID = ""
+		session.lastOutput = nil
+	}
+	session.mu.Unlock()
+	_ = connection.CloseNow()
+}
+
+func (provider *CodexProvider) dialResponsesWebSocket(ctx context.Context) (*websocket.Conn, error) {
+	endpoint, err := responsesWebSocketURL(provider.inner.endpoint)
+	if err != nil {
+		return nil, err
+	}
+	for authTry := 0; authTry < 2; authTry++ {
+		headers, err := provider.responsesWebSocketHeaders(ctx, authTry == 1)
+		if err != nil {
+			return nil, err
+		}
+		connection, response, err := websocket.Dial(ctx, endpoint, &websocket.DialOptions{
+			HTTPClient:      provider.inner.httpClient,
+			HTTPHeader:      headers,
+			CompressionMode: websocket.CompressionNoContextTakeover,
+		})
+		if err == nil {
+			connection.SetReadLimit(responsesWebSocketReadLimit)
+			return connection, nil
+		}
+		if response == nil || response.StatusCode != http.StatusUnauthorized || provider.inner.oauthResolver == nil || authTry == 1 {
+			return nil, err
+		}
+	}
+	return nil, errors.New("codex websocket authentication failed")
+}
+
+func (provider *CodexProvider) responsesWebSocketHeaders(ctx context.Context, forceRefresh bool) (http.Header, error) {
+	request, err := http.NewRequestWithContext(ctx, http.MethodGet, provider.inner.endpoint, nil)
+	if err != nil {
+		return nil, err
+	}
+	base := providerio.AuthHeaders{
+		APIKey:            provider.inner.apiKey,
+		DefaultAuthHeader: "Authorization",
+		DefaultAuthScheme: "Bearer",
+		AuthHeader:        provider.inner.authHeader,
+		AuthScheme:        provider.inner.authScheme,
+		AuthHeaderValue:   provider.inner.authHeaderValue,
+		CustomHeaders:     provider.inner.customHeaders,
+	}
+	if resolver := provider.inner.oauthResolver; resolver != nil {
+		header, value, ok, err := resolver(ctx, forceRefresh)
+		if err != nil {
+			return nil, err
+		}
+		if ok {
+			providerio.ApplyAuthHeaders(request, providerio.AuthHeaders{CustomHeaders: provider.inner.customHeaders})
+			if strings.TrimSpace(header) == "" {
+				header = "Authorization"
+			}
+			request.Header.Set(header, value)
+		} else {
+			providerio.ApplyAuthHeaders(request, base)
+		}
+	} else {
+		providerio.ApplyAuthHeaders(request, base)
+	}
+	provider.injectCodexHeaders(request)
+	request.Header.Set(responsesWebSocketBetaHeader, responsesWebSocketBetaValue)
+	return request.Header.Clone(), nil
+}
+
+func responsesWebSocketURL(endpoint string) (string, error) {
+	parsed, err := url.Parse(strings.TrimSpace(endpoint))
+	if err != nil {
+		return "", err
+	}
+	switch parsed.Scheme {
+	case "http":
+		parsed.Scheme = "ws"
+	case "https":
+		parsed.Scheme = "wss"
+	default:
+		return "", fmt.Errorf("unsupported Responses websocket URL scheme %q", parsed.Scheme)
+	}
+	return parsed.String(), nil
+}

internal/providers/openai/codex_session_test.go

@@ -0,0 +1,590 @@
+package openai
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/coder/websocket"
+
+	"github.com/Gitlawb/zero/internal/trace"
+	"github.com/Gitlawb/zero/internal/zeroruntime"
+)
+
+func TestCodexTurnSessionChainsOnlyAppendOnlyRequests(t *testing.T) {
+	var mu sync.Mutex
+	requests := []map[string]any{}
+	betaHeader := ""
+	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
+		if !strings.EqualFold(request.Header.Get("Upgrade"), "websocket") {
+			http.Error(writer, "websocket required", http.StatusUpgradeRequired)
+			return
+		}
+		mu.Lock()
+		betaHeader = request.Header.Get(responsesWebSocketBetaHeader)
+		mu.Unlock()
+		connection, err := websocket.Accept(writer, request, nil)
+		if err != nil {
+			return
+		}
+		defer connection.CloseNow()
+		for index := 0; index < 3; index++ {
+			_, body, err := connection.Read(request.Context())
+			if err != nil {
+				return
+			}
+			var payload map[string]any
+			if err := json.Unmarshal(body, &payload); err != nil {
+				return
+			}
+			mu.Lock()
+			requests = append(requests, payload)
+			mu.Unlock()
+			switch index {
+			case 0:
+				writeWebSocketEvents(request.Context(), connection,
+					`{"type":"response.created","response":{"id":"resp-1","status":"in_progress"}}`,
+					`{"type":"response.output_item.added","item_id":"call-1","item":{"type":"function_call","id":"call-1","call_id":"call-1","name":"read_file"}}`,
+					`{"type":"response.function_call_arguments.delta","item_id":"call-1","delta":"{}"}`,
+					`{"type":"response.output_item.done","item_id":"call-1","item":{"type":"function_call","id":"call-1","call_id":"call-1","name":"read_file","arguments":"{}"}}`,
+					`{"type":"response.completed","response":{"id":"resp-1","status":"completed"}}`,
+				)
+			case 1:
+				writeWebSocketEvents(request.Context(), connection,
+					`{"type":"response.output_text.delta","delta":"done"}`,
+					`{"type":"response.completed","response":{"id":"resp-2","status":"completed"}}`,
+				)
+			case 2:
+				writeWebSocketEvents(request.Context(), connection,
+					`{"type":"response.completed","response":{"id":"resp-3","status":"completed"}}`,
+				)
+			}
+		}
+	}))
+	defer server.Close()
+
+	provider := newCodexSessionTestProvider(t, server)
+	// A disabled stream watchdog must use the parent context rather than creating
+	// an immediately-expired read deadline.
+	provider.inner.streamIdleTimeout = 0
+	session := openCodexSession(t, provider)
+	defer session.Close()
+	recorder := trace.NewRecorder("session-1", "run-1", "test")
+	recorder.Start()
+	streamContext := trace.WithContext(t.Context(), recorder)
+
+	base := zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{
+			{Role: zeroruntime.MessageRoleSystem, Content: "Use tools carefully."},
+			{Role: zeroruntime.MessageRoleUser, Content: "Read the file."},
+		},
+		Tools:          []zeroruntime.ToolDefinition{{Name: "read_file", Parameters: map[string]any{"type": "object"}}},
+		PromptCacheKey: "session-1",
+	}
+	first := collectCodexSessionEvents(t, session, base)
+	if !hasToolCallEnd(first, "call-1") {
+		t.Fatalf("first stream did not produce the tool call: %#v", first)
+	}
+
+	second := base
+	second.Messages = append(append([]zeroruntime.Message(nil), base.Messages...),
+		zeroruntime.Message{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{{ID: "call-1", Name: "read_file", Arguments: "{}"}}},
+		zeroruntime.Message{Role: zeroruntime.MessageRoleTool, ToolCallID: "call-1", Content: "contents"},
+	)
+	secondEvents := collectCodexSessionEventsContext(t, streamContext, session, second)
+	if got := joinedText(secondEvents); got != "done" {
+		t.Fatalf("second stream text = %q, want done", got)
+	}
+
+	third := second
+	third.ReasoningEffort = "high"
+	third.Messages = append(append([]zeroruntime.Message(nil), second.Messages...),
+		zeroruntime.Message{Role: zeroruntime.MessageRoleAssistant, Content: "done"},
+		zeroruntime.Message{Role: zeroruntime.MessageRoleUser, Content: "Continue."},
+	)
+	collectCodexSessionEventsContext(t, streamContext, session, third)
+	finishedTrace := recorder.Finish()
+	if got := finishedTrace.Counter(trace.CounterResponseChainReused); got != 1 {
+		t.Fatalf("response-chain reuse count = %d, want 1", got)
+	}
+	if got := finishedTrace.Counter(trace.CounterResponseChainReset); got != 1 {
+		t.Fatalf("response-chain reset count = %d, want 1", got)
+	}
+
+	mu.Lock()
+	defer mu.Unlock()
+	if len(requests) != 3 {
+		t.Fatalf("websocket requests = %d, want 3", len(requests))
+	}
+	if betaHeader != responsesWebSocketBetaValue {
+		t.Fatalf("OpenAI-Beta = %q, want %q", betaHeader, responsesWebSocketBetaValue)
+	}
+	if requests[0]["type"] != responsesWebSocketRequest || requests[0]["previous_response_id"] != nil {
+		t.Fatalf("first request chaining fields = %#v", requests[0])
+	}
+	if requests[0]["parallel_tool_calls"] != true || requests[0]["prompt_cache_key"] != "session-1" {
+		t.Fatalf("first request stable fields = %#v", requests[0])
+	}
+	if requests[1]["previous_response_id"] != "resp-1" {
+		t.Fatalf("second previous_response_id = %#v", requests[1]["previous_response_id"])
+	}
+	secondInput, _ := requests[1]["input"].([]any)
+	if len(secondInput) != 1 || secondInput[0].(map[string]any)["type"] != "function_call_output" {
+		t.Fatalf("second incremental input = %#v", requests[1]["input"])
+	}
+	if requests[2]["previous_response_id"] != nil {
+		t.Fatalf("incompatible request reused response chain: %#v", requests[2])
+	}
+	thirdInput, _ := requests[2]["input"].([]any)
+	if len(thirdInput) <= 1 {
+		t.Fatalf("incompatible request did not send full input: %#v", thirdInput)
+	}
+}
+
+func TestCodexTurnSessionFallsBackWhenPreviousResponseIsMissing(t *testing.T) {
+	var mu sync.Mutex
+	webSocketRequests := 0
+	httpRequests := 0
+	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
+		if strings.EqualFold(request.Header.Get("Upgrade"), "websocket") {
+			connection, err := websocket.Accept(writer, request, nil)
+			if err != nil {
+				return
+			}
+			defer connection.CloseNow()
+			for index := 0; index < 2; index++ {
+				if _, _, err := connection.Read(request.Context()); err != nil {
+					return
+				}
+				mu.Lock()
+				webSocketRequests++
+				mu.Unlock()
+				if index == 0 {
+					writeWebSocketEvents(request.Context(), connection,
+						`{"type":"response.output_item.added","item_id":"call-1","item":{"type":"function_call","id":"call-1","call_id":"call-1","name":"read_file"}}`,
+						`{"type":"response.output_item.done","item_id":"call-1","item":{"type":"function_call","id":"call-1","call_id":"call-1","name":"read_file","arguments":"{}"}}`,
+						`{"type":"response.completed","response":{"id":"resp-1","status":"completed"}}`,
+					)
+					continue
+				}
+				writeWebSocketEvents(request.Context(), connection,
+					`{"type":"response.error","code":"previous_response_not_found","message":"missing"}`,
+				)
+			}
+			return
+		}
+
+		mu.Lock()
+		httpRequests++
+		mu.Unlock()
+		writer.Header().Set("Content-Type", "text/event-stream")
+		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.output_text.delta\",\"delta\":\"fallback\"}\n\n")
+		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.completed\",\"response\":{\"id\":\"resp-http\",\"status\":\"completed\"}}\n\n")
+	}))
+	defer server.Close()
+
+	provider := newCodexSessionTestProvider(t, server)
+	session := openCodexSession(t, provider)
+	defer session.Close()
+	base := zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Read it."}},
+		Tools:    []zeroruntime.ToolDefinition{{Name: "read_file", Parameters: map[string]any{"type": "object"}}},
+	}
+	collectCodexSessionEvents(t, session, base)
+	second := base
+	second.Messages = append(append([]zeroruntime.Message(nil), base.Messages...),
+		zeroruntime.Message{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{{ID: "call-1", Name: "read_file", Arguments: "{}"}}},
+		zeroruntime.Message{Role: zeroruntime.MessageRoleTool, ToolCallID: "call-1", Content: "contents"},
+	)
+	events := collectCodexSessionEvents(t, session, second)
+	if got := joinedText(events); got != "fallback" {
+		t.Fatalf("fallback stream text = %q, want fallback; events=%#v", got, events)
+	}
+	for _, event := range events {
+		if event.Type == zeroruntime.StreamEventError {
+			t.Fatalf("response-chain recovery leaked an error: %#v", event)
+		}
+	}
+	mu.Lock()
+	defer mu.Unlock()
+	if webSocketRequests != 2 || httpRequests != 1 {
+		t.Fatalf("requests = websocket:%d http:%d, want 2/1", webSocketRequests, httpRequests)
+	}
+}
+
+func TestCodexTurnSessionFallsBackWhenSocketClosesBeforeOutput(t *testing.T) {
+	var mu sync.Mutex
+	httpRequests := 0
+	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
+		if strings.EqualFold(request.Header.Get("Upgrade"), "websocket") {
+			connection, err := websocket.Accept(writer, request, nil)
+			if err != nil {
+				return
+			}
+			if _, _, err := connection.Read(request.Context()); err == nil {
+				_ = connection.CloseNow()
+			}
+			return
+		}
+		mu.Lock()
+		httpRequests++
+		mu.Unlock()
+		writer.Header().Set("Content-Type", "text/event-stream")
+		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.output_text.delta\",\"delta\":\"recovered\"}\n\n")
+		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.completed\",\"response\":{\"id\":\"resp-http\",\"status\":\"completed\"}}\n\n")
+	}))
+	defer server.Close()
+
+	provider := newCodexSessionTestProvider(t, server)
+	session := openCodexSession(t, provider)
+	defer session.Close()
+	recorder := trace.NewRecorder("session-fallback", "run-fallback", "test")
+	recorder.Start()
+	events := collectCodexSessionEventsContext(t, trace.WithContext(t.Context(), recorder), session, zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Hello"}},
+	})
+	if got := joinedText(events); got != "recovered" {
+		t.Fatalf("fallback text = %q, want recovered", got)
+	}
+	mu.Lock()
+	defer mu.Unlock()
+	if httpRequests != 1 {
+		t.Fatalf("HTTP fallback requests = %d, want 1", httpRequests)
+	}
+	if got := recorder.Finish().Counter(trace.CounterResponsesHTTPFallback); got != 1 {
+		t.Fatalf("responses HTTP fallback counter = %d, want 1", got)
+	}
+}
+
+func TestCodexTurnSessionKeepsWebSocketAfterIncompleteResponse(t *testing.T) {
+	var mu sync.Mutex
+	webSocketRequests := 0
+	httpRequests := 0
+	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
+		if strings.EqualFold(request.Header.Get("Upgrade"), "websocket") {
+			connection, err := websocket.Accept(writer, request, nil)
+			if err != nil {
+				return
+			}
+			defer connection.CloseNow()
+			for index := 0; index < 2; index++ {
+				if _, _, err := connection.Read(request.Context()); err != nil {
+					return
+				}
+				mu.Lock()
+				webSocketRequests++
+				mu.Unlock()
+				if index == 0 {
+					writeWebSocketEvents(request.Context(), connection,
+						`{"type":"response.incomplete","response":{"id":"resp-1","status":"incomplete"}}`,
+					)
+					continue
+				}
+				writeWebSocketEvents(request.Context(), connection,
+					`{"type":"response.output_text.delta","delta":"websocket"}`,
+					`{"type":"response.completed","response":{"id":"resp-2","status":"completed"}}`,
+				)
+			}
+			return
+		}
+
+		mu.Lock()
+		httpRequests++
+		mu.Unlock()
+		writer.Header().Set("Content-Type", "text/event-stream")
+		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.output_text.delta\",\"delta\":\"fallback\"}\n\n")
+		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.completed\",\"response\":{\"id\":\"resp-http\",\"status\":\"completed\"}}\n\n")
+	}))
+	defer server.Close()
+
+	provider := newCodexSessionTestProvider(t, server)
+	session := openCodexSession(t, provider)
+	defer session.Close()
+	request := zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Continue."}},
+	}
+	first := collectCodexSessionEvents(t, session, request)
+	if len(first) != 1 || first[0].Type != zeroruntime.StreamEventDone || first[0].FinishReason != zeroruntime.FinishReasonLength {
+		t.Fatalf("incomplete response events = %#v, want length completion", first)
+	}
+	second := collectCodexSessionEvents(t, session, request)
+	if got := joinedText(second); got != "websocket" {
+		t.Fatalf("second turn text = %q, want websocket; events=%#v", got, second)
+	}
+	mu.Lock()
+	defer mu.Unlock()
+	if webSocketRequests != 2 || httpRequests != 0 {
+		t.Fatalf("requests = websocket:%d http:%d, want 2/0", webSocketRequests, httpRequests)
+	}
+}
+
+func TestCodexTurnSessionDoesNotReplayAfterVisibleOutput(t *testing.T) {
+	var mu sync.Mutex
+	httpRequests := 0
+	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
+		if strings.EqualFold(request.Header.Get("Upgrade"), "websocket") {
+			connection, err := websocket.Accept(writer, request, nil)
+			if err != nil {
+				return
+			}
+			if _, _, err := connection.Read(request.Context()); err == nil {
+				writeWebSocketEvents(request.Context(), connection,
+					`{"type":"response.output_text.delta","delta":"visible"}`,
+				)
+			}
+			_ = connection.Close(websocket.StatusInternalError, "interrupted")
+			return
+		}
+		mu.Lock()
+		httpRequests++
+		mu.Unlock()
+	}))
+	defer server.Close()
+
+	provider := newCodexSessionTestProvider(t, server)
+	session := openCodexSession(t, provider)
+	defer session.Close()
+	stream, err := session.Stream(t.Context(), zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Hello"}},
+	})
+	if err != nil {
+		t.Fatalf("Stream: %v", err)
+	}
+	sawText, sawError := false, false
+	for event := range stream {
+		sawText = sawText || event.Type == zeroruntime.StreamEventText
+		sawError = sawError || event.Type == zeroruntime.StreamEventError
+	}
+	if !sawText || !sawError {
+		t.Fatalf("visible interrupted stream = text:%v error:%v", sawText, sawError)
+	}
+	mu.Lock()
+	defer mu.Unlock()
+	if httpRequests != 0 {
+		t.Fatalf("visible interrupted stream was replayed over HTTP %d time(s)", httpRequests)
+	}
+}
+
+func TestCodexTurnSessionReportsWebSocketIdleTimeout(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
+		connection, err := websocket.Accept(writer, request, nil)
+		if err != nil {
+			return
+		}
+		defer connection.CloseNow()
+		if _, _, err := connection.Read(request.Context()); err != nil {
+			return
+		}
+		writeWebSocketEvents(request.Context(), connection,
+			`{"type":"response.output_text.delta","delta":"visible"}`,
+		)
+		<-request.Context().Done()
+	}))
+	defer server.Close()
+
+	provider := newCodexSessionTestProvider(t, server)
+	provider.inner.streamIdleTimeout = 200 * time.Millisecond
+	session := openCodexSession(t, provider)
+	defer session.Close()
+	stream, err := session.Stream(t.Context(), zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Hello"}},
+	})
+	if err != nil {
+		t.Fatalf("Stream: %v", err)
+	}
+
+	var streamError string
+	for event := range stream {
+		if event.Type == zeroruntime.StreamEventError {
+			streamError = event.Error
+			break
+		}
+	}
+	if !strings.Contains(streamError, "idle timeout after 200ms") {
+		t.Fatalf("stream error = %q, want idle-timeout detail", streamError)
+	}
+}
+
+func TestCodexTurnSessionRejectsOverlappingStreams(t *testing.T) {
+	started := make(chan struct{})
+	release := make(chan struct{})
+	var releaseOnce sync.Once
+	releaseStream := func() { releaseOnce.Do(func() { close(release) }) }
+	t.Cleanup(releaseStream)
+	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
+		connection, err := websocket.Accept(writer, request, nil)
+		if err != nil {
+			return
+		}
+		defer connection.CloseNow()
+		if _, _, err := connection.Read(request.Context()); err != nil {
+			return
+		}
+		close(started)
+		<-release
+		writeWebSocketEvents(request.Context(), connection,
+			`{"type":"response.completed","response":{"id":"resp-1","status":"completed"}}`,
+		)
+	}))
+	defer server.Close()
+
+	provider := newCodexSessionTestProvider(t, server)
+	session := openCodexSession(t, provider)
+	defer session.Close()
+	request := zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Hello"}},
+	}
+	first, err := session.Stream(t.Context(), request)
+	if err != nil {
+		t.Fatalf("first Stream: %v", err)
+	}
+	select {
+	case <-started:
+	case <-time.After(time.Second):
+		t.Fatal("first WebSocket stream did not start")
+	}
+	if _, err := session.Stream(t.Context(), request); !errors.Is(err, errCodexTurnSessionBusy) {
+		t.Fatalf("overlapping Stream error = %v, want %v", err, errCodexTurnSessionBusy)
+	}
+	releaseStream()
+	for range first {
+	}
+}
+
+func TestCodexTurnSessionHTTPFallbackRedactsSetupError(t *testing.T) {
+	const secret = "sk-secret-fallback"
+	provider, err := NewCodexProvider(CodexOptions{Options: Options{
+		APIKey:  secret,
+		BaseURL: "https://chatgpt.example/backend-api/codex",
+		Model:   "gpt-test",
+	}})
+	if err != nil {
+		t.Fatalf("NewCodexProvider: %v", err)
+	}
+	session := &codexTurnSession{provider: provider}
+	events := make(chan zeroruntime.StreamEvent, 1)
+	session.forwardHTTP(t.Context(), zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRole(secret), Content: "invalid"}},
+	}, events)
+
+	select {
+	case event := <-events:
+		if event.Type != zeroruntime.StreamEventError {
+			t.Fatalf("fallback event type = %s, want error", event.Type)
+		}
+		if strings.Contains(event.Error, secret) {
+			t.Fatalf("fallback error leaked credential: %q", event.Error)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("fallback did not emit setup error")
+	}
+}
+
+func TestCodexTurnSessionCloseDoesNotStartPrewarm(t *testing.T) {
+	provider, err := NewCodexProvider(CodexOptions{Options: Options{
+		APIKey:  "test-token",
+		BaseURL: "https://chatgpt.example/backend-api/codex",
+		Model:   "gpt-test",
+	}})
+	if err != nil {
+		t.Fatalf("NewCodexProvider: %v", err)
+	}
+	session, err := NewCodexTurnSessionProvider(provider, zeroruntime.ProviderCapabilities{}).OpenTurnSession(t.Context())
+	if err != nil {
+		t.Fatalf("OpenTurnSession: %v", err)
+	}
+	done := make(chan error, 1)
+	go func() { done <- session.Close() }()
+	select {
+	case err := <-done:
+		if err != nil {
+			t.Fatalf("Close() error = %v", err)
+		}
+	case <-time.After(200 * time.Millisecond):
+		t.Fatal("Close blocked without a prewarm attempt")
+	}
+}
+
+func newCodexSessionTestProvider(t *testing.T, server *httptest.Server) *CodexProvider {
+	t.Helper()
+	provider, err := NewCodexProvider(CodexOptions{
+		Options: Options{
+			APIKey:     "test-token",
+			BaseURL:    server.URL,
+			Model:      "gpt-test",
+			HTTPClient: server.Client(),
+		},
+		AccountID: "account-test",
+	})
+	if err != nil {
+		t.Fatalf("NewCodexProvider: %v", err)
+	}
+	return provider
+}
+
+func openCodexSession(t *testing.T, provider *CodexProvider) zeroruntime.TurnSession {
+	t.Helper()
+	session, err := NewCodexTurnSessionProvider(provider, zeroruntime.ProviderCapabilities{}).OpenTurnSession(t.Context())
+	if err != nil {
+		t.Fatalf("OpenTurnSession: %v", err)
+	}
+	if err := session.Prewarm(t.Context()); err != nil {
+		t.Fatalf("Prewarm: %v", err)
+	}
+	return session
+}
+
+func collectCodexSessionEvents(t *testing.T, session zeroruntime.TurnSession, request zeroruntime.CompletionRequest) []zeroruntime.StreamEvent {
+	t.Helper()
+	return collectCodexSessionEventsContext(t, t.Context(), session, request)
+}
+
+func collectCodexSessionEventsContext(t *testing.T, ctx context.Context, session zeroruntime.TurnSession, request zeroruntime.CompletionRequest) []zeroruntime.StreamEvent {
+	t.Helper()
+	stream, err := session.Stream(ctx, request)
+	if err != nil {
+		t.Fatalf("Stream: %v", err)
+	}
+	events := []zeroruntime.StreamEvent{}
+	for event := range stream {
+		events = append(events, event)
+		if event.Type == zeroruntime.StreamEventError {
+			t.Fatalf("stream error: %s", event.Error)
+		}
+	}
+	return events
+}
+
+func writeWebSocketEvents(ctx context.Context, connection *websocket.Conn, events ...string) {
+	for _, event := range events {
+		if err := connection.Write(ctx, websocket.MessageText, []byte(event)); err != nil {
+			return
+		}
+	}
+}
+
+func hasToolCallEnd(events []zeroruntime.StreamEvent, id string) bool {
+	for _, event := range events {
+		if event.Type == zeroruntime.StreamEventToolCallEnd && event.ToolCallID == id {
+			return true
+		}
+	}
+	return false
+}
+
+func joinedText(events []zeroruntime.StreamEvent) string {
+	var builder strings.Builder
+	for _, event := range events {
+		if event.Type == zeroruntime.StreamEventText {
+			builder.WriteString(event.Content)
+		}
+	}
+	return builder.String()
+}

internal/providers/openai/codex_terminal_test.go

@@ -2,6 +2,8 @@ package openai
 
 import (
 	"context"
+	"reflect"
+	"strings"
 	"testing"
 
 	"github.com/Gitlawb/zero/internal/zeroruntime"
@@ -25,6 +27,126 @@ func TestToolCallKeyOutputIndexZero(t *testing.T) {
 	}
 }
 
+func TestResponsesStatePreservesDistinctCallID(t *testing.T) {
+	provider := &CodexProvider{}
+	state := newResponsesState()
+	events := make(chan zeroruntime.StreamEvent, 4)
+	provider.handleOutputItemAdded(context.Background(), &responsesEvent{
+		ItemID: "item-1",
+		Item: &itemPayload{
+			Type:   "function_call",
+			ID:     "item-1",
+			CallID: "call-1",
+			Name:   "read_file",
+		},
+	}, state, events)
+	items := state.outputInputItems()
+	if len(items) != 1 || items[0].ID != "item-1" || items[0].CallID != "call-1" {
+		t.Fatalf("captured function call = %#v, want item id item-1 and call id call-1", items)
+	}
+}
+
+func TestCodexCustomApplyPatchStreamProducesFreeformCall(t *testing.T) {
+	provider := &CodexProvider{}
+	state := newResponsesState()
+	events := make(chan zeroruntime.StreamEvent, 16)
+	patch := "*** Begin Patch\n*** Add File: hello.txt\n+hello\n*** End Patch\n"
+	for _, payload := range []string{
+		`{"type":"response.output_item.added","item_id":"item-1","item":{"type":"custom_tool_call","call_id":"call-1","name":"apply_patch"}}`,
+		`{"type":"response.custom_tool_call_input.delta","item_id":"item-1","call_id":"call-1","delta":"*** Begin Patch\n*** Add File: hello.txt\n"}`,
+		`{"type":"response.custom_tool_call_input.delta","item_id":"item-1","call_id":"call-1","delta":"+hello\n*** End Patch\n"}`,
+		`{"type":"response.output_item.done","item_id":"item-1","item":{"type":"custom_tool_call","call_id":"call-1","name":"apply_patch","input":"*** Begin Patch\n*** Add File: hello.txt\n+hello\n*** End Patch\n"}}`,
+		`{"type":"response.completed","response":{"id":"resp-1","status":"completed"}}`,
+	} {
+		if keepReading := provider.emitResponsesEvent(context.Background(), payload, state, events); !keepReading && !state.done {
+			t.Fatalf("stream stopped before terminal event for %s", payload)
+		}
+	}
+	close(events)
+	collected := zeroruntime.CollectStream(context.Background(), events)
+	if len(collected.ToolCalls) != 1 {
+		t.Fatalf("tool calls = %#v, want one", collected.ToolCalls)
+	}
+	call := collected.ToolCalls[0]
+	if call.ID != "item-1" || call.ProviderCallID != "call-1" || call.Name != "apply_patch" || !call.Freeform || call.Arguments != patch {
+		t.Fatalf("custom apply_patch call = %#v", call)
+	}
+}
+
+func TestCodexApplyPatchUsesFreeformWireContract(t *testing.T) {
+	provider, err := NewCodexProvider(CodexOptions{Options: Options{
+		APIKey:  "test-token",
+		BaseURL: "https://chatgpt.example/backend-api/codex",
+		Model:   "gpt-test",
+	}})
+	if err != nil {
+		t.Fatalf("NewCodexProvider: %v", err)
+	}
+	patch := "*** Begin Patch\n*** Add File: hello.txt\n+hello\n*** End Patch\n"
+	request, err := provider.buildResponsesRequest(zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{
+			{Role: zeroruntime.MessageRoleUser, Content: "Add the file."},
+			{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{{
+				ID: "item-1", ProviderCallID: "call-1", Name: "apply_patch", Arguments: patch, Freeform: true,
+			}}},
+			{Role: zeroruntime.MessageRoleTool, ToolCallID: "item-1", ToolCallProviderID: "call-1", Content: "Done!"},
+		},
+		Tools: []zeroruntime.ToolDefinition{{
+			Name: "apply_patch", Description: "Apply a patch.", Type: zeroruntime.ToolDefinitionFreeform,
+		}},
+	})
+	if err != nil {
+		t.Fatalf("buildResponsesRequest: %v", err)
+	}
+	if len(request.Tools) != 1 || request.Tools[0].Type != string(zeroruntime.ToolDefinitionFreeform) ||
+		request.Tools[0].Format == nil || request.Tools[0].Format.Syntax != "lark" || request.Tools[0].Parameters != nil {
+		t.Fatalf("apply_patch tool wire shape = %#v", request.Tools)
+	}
+	if !strings.Contains(request.Tools[0].Format.Definition, "*** Begin Patch") {
+		t.Fatalf("apply_patch grammar = %q", request.Tools[0].Format.Definition)
+	}
+	if !strings.Contains(request.Tools[0].Description, "absolute file paths") || !strings.Contains(request.Tools[0].Description, "granted extra write root") {
+		t.Fatalf("apply_patch description does not explain extra-root paths: %q", request.Tools[0].Description)
+	}
+	if len(request.Input) != 3 || request.Input[1].Type != "custom_tool_call" || request.Input[1].ID != "item-1" ||
+		request.Input[1].CallID != "call-1" || request.Input[1].Input != patch ||
+		request.Input[2].Type != "custom_tool_call_output" || request.Input[2].CallID != "call-1" {
+		t.Fatalf("custom apply_patch replay input = %#v", request.Input)
+	}
+}
+
+func TestCodexPreservesCustomApplyPatchFunction(t *testing.T) {
+	provider, err := NewCodexProvider(CodexOptions{Options: Options{
+		APIKey:  "test-token",
+		BaseURL: "https://chatgpt.example/backend-api/codex",
+		Model:   "gpt-test",
+	}})
+	if err != nil {
+		t.Fatalf("NewCodexProvider: %v", err)
+	}
+	parameters := map[string]any{
+		"type":       "object",
+		"properties": map[string]any{"value": map[string]any{"type": "string"}},
+	}
+	request, err := provider.buildResponsesRequest(zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Call the custom tool."}},
+		Tools: []zeroruntime.ToolDefinition{{
+			Name: "apply_patch", Description: "Custom integration tool.", Parameters: parameters,
+		}},
+	})
+	if err != nil {
+		t.Fatalf("buildResponsesRequest: %v", err)
+	}
+	if len(request.Tools) != 1 {
+		t.Fatalf("tools = %#v, want one", request.Tools)
+	}
+	tool := request.Tools[0]
+	if tool.Type != string(zeroruntime.ToolDefinitionFunction) || tool.Format != nil ||
+		tool.Description != "Custom integration tool." || !reflect.DeepEqual(tool.Parameters, parameters) {
+		t.Fatalf("custom apply_patch function was rewritten: %#v", tool)
+	}
+}
+
 func TestHandleTerminalResponseNilPayload(t *testing.T) {
 	p := &CodexProvider{}
 
@@ -90,11 +212,14 @@ func TestHandleTerminalResponseFailedPayloadWithoutError(t *testing.T) {
 	// A response.completed with a payload and no error remains a clean done.
 	ok := make(chan zeroruntime.StreamEvent, 8)
 	p.handleTerminalResponse(context.Background(),
-		&responsesEvent{Type: responsesEventCompleted, Response: &responsePayload{Status: "completed"}}, &responsesState{}, ok)
+		&responsesEvent{Type: responsesEventCompleted, Response: &responsePayload{ID: "resp-1", Status: "completed"}}, &responsesState{}, ok)
 	close(ok)
 	for ev := range ok {
 		if ev.Type == zeroruntime.StreamEventError {
 			t.Error("response.completed with a non-error payload must NOT emit an error")
 		}
+		if ev.Type == zeroruntime.StreamEventDone && ev.ResponseID != "resp-1" {
+			t.Errorf("done response id = %q, want resp-1", ev.ResponseID)
+		}
 	}
 }

internal/providers/openai/codex_test.go

@@ -771,7 +771,7 @@ func TestCodexProviderParsesResponsesTextDeltas(t *testing.T) {
 		`{"type":"response.output_text.delta","delta":"hello "}`,
 		`{"type":"response.output_text.delta","delta":"world"}`,
 		`{"type":"response.output_text.delta","delta":"!"}`,
-		`{"type":"response.completed","response":{"id":"resp-1","status":"completed","usage":{"input_tokens":7,"output_tokens":3,"output_tokens_details":{"reasoning_tokens":1},"input_tokens_details":{"cached_tokens":2}}}}`,
+		`{"type":"response.completed","response":{"id":"resp-1","status":"completed","usage":{"input_tokens":7,"output_tokens":3,"output_tokens_details":{"reasoning_tokens":1},"input_tokens_details":{"cached_tokens":2,"cache_write_tokens":1}}}}`,
 	)
 	defer srv.Close()
 
@@ -809,8 +809,8 @@ func TestCodexProviderParsesResponsesTextDeltas(t *testing.T) {
 	if usage == nil {
 		t.Fatal("expected a usage event, got none")
 	}
-	if usage.InputTokens != 7 || usage.OutputTokens != 3 || usage.CachedInputTokens != 2 || usage.ReasoningTokens != 1 {
-		t.Fatalf("usage = %+v, want input=7 output=3 cached=2 reasoning=1", *usage)
+	if usage.InputTokens != 7 || usage.OutputTokens != 3 || usage.CachedInputTokens != 2 || usage.CacheWriteTokens != 1 || usage.ReasoningTokens != 1 {
+		t.Fatalf("usage = %+v, want input=7 output=3 cached=2 cache-write=1 reasoning=1", *usage)
 	}
 	if !gotDone {
 		t.Fatal("expected a done event, got none")

internal/providers/openai/provider.go

@@ -357,6 +357,7 @@ func (provider *Provider) emitChunk(
 				PromptTokens:      chunk.Usage.PromptTokens,
 				CompletionTokens:  chunk.Usage.CompletionTokens,
 				CachedInputTokens: chunk.Usage.PromptTokensDetails.CachedTokens,
+				CacheWriteTokens:  chunk.Usage.PromptTokensDetails.CacheWriteTokens,
 				ReasoningTokens:   chunk.Usage.CompletionTokensDetails.ReasoningTokens,
 			},
 		})
@@ -486,7 +487,7 @@ func (provider *Provider) openAIRequest(request zeroruntime.CompletionRequest) c
 				Function: toolFunction{
 					Name:        tool.Name,
 					Description: tool.Description,
-					Parameters:  tool.Parameters,
+					Parameters:  normalizeToolParameters(tool.Parameters),
 				},
 			})
 		}
@@ -494,6 +495,21 @@ func (provider *Provider) openAIRequest(request zeroruntime.CompletionRequest) c
 	return mapped
 }
 
+// normalizeToolParameters keeps schemas accepted by strict OpenAI-compatible
+// servers such as LM Studio. No-argument tools still need an object-valued
+// parameters.properties field instead of an omitted field.
+func normalizeToolParameters(parameters map[string]any) map[string]any {
+	normalized := make(map[string]any, len(parameters)+1)
+	for key, value := range parameters {
+		normalized[key] = value
+	}
+	properties, ok := normalized["properties"].(map[string]any)
+	if !ok || properties == nil {
+		normalized["properties"] = map[string]any{}
+	}
+	return normalized
+}
+
 // promptCacheKeyDisabled reports whether the ZERO_DISABLE_PROMPT_CACHE_KEY
 // kill switch is set to a truthy value. "0" and "false" (any case) are
 // no-ops, matching how ZERO_FORMAT_ON_WRITE parses boolean flags, so an

internal/providers/openai/provider_test.go

@@ -3,6 +3,7 @@ package openai
 import (
 	"context"
 	"encoding/json"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"reflect"
@@ -105,6 +106,72 @@ func TestStreamCompletionPostsChatCompletionRequest(t *testing.T) {
 	if tool["type"] != "function" {
 		t.Fatalf("unexpected tool wrapper: %#v", tool)
 	}
+	functionDefinition := tool["function"].(map[string]any)
+	parameters := functionDefinition["parameters"].(map[string]any)
+	properties, ok := parameters["properties"].(map[string]any)
+	if !ok || len(properties) != 0 {
+		t.Fatalf("parameters.properties = %#v, want empty object", parameters["properties"])
+	}
+}
+
+// TestStreamCompletionSerializesTypedNilPropertiesAsEmptyObject locks in the
+// normalizeToolParameters fix: a tool whose parameters carry a typed-nil
+// properties map must serialize "properties":{} on the wire, never
+// "properties":null, because strict OpenAI-compatible servers (LM Studio)
+// reject the null form.
+func TestStreamCompletionSerializesTypedNilPropertiesAsEmptyObject(t *testing.T) {
+	var gotBody map[string]any
+	var gotRaw []byte
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		raw, err := io.ReadAll(r.Body)
+		if err != nil {
+			t.Fatalf("read request body: %v", err)
+		}
+		gotRaw = raw
+		if err := json.Unmarshal(raw, &gotBody); err != nil {
+			t.Fatalf("decode request body: %v", err)
+		}
+		writeSSE(w, `{"choices":[]}`)
+		writeSSE(w, `[DONE]`)
+	}))
+	defer server.Close()
+
+	provider, err := New(Options{
+		APIKey:  "sk-secret",
+		BaseURL: server.URL + "/",
+		Model:   "gpt-test",
+	})
+	if err != nil {
+		t.Fatalf("New returned error: %v", err)
+	}
+
+	stream, err := provider.StreamCompletion(context.Background(), zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "hi"}},
+		Tools: []zeroruntime.ToolDefinition{{
+			Name:        "no_args",
+			Description: "Takes no arguments",
+			Parameters:  map[string]any{"type": "object", "properties": map[string]any(nil)},
+		}},
+	})
+	if err != nil {
+		t.Fatalf("StreamCompletion returned error: %v", err)
+	}
+	drain(stream)
+
+	if !strings.Contains(string(gotRaw), `"properties":{}`) {
+		t.Fatalf("request body must serialize properties as an empty object, got: %s", gotRaw)
+	}
+	if strings.Contains(string(gotRaw), `"properties":null`) {
+		t.Fatalf("request body must not serialize properties as null, got: %s", gotRaw)
+	}
+	tools := gotBody["tools"].([]any)
+	tool := tools[0].(map[string]any)
+	functionDefinition := tool["function"].(map[string]any)
+	parameters := functionDefinition["parameters"].(map[string]any)
+	properties, ok := parameters["properties"].(map[string]any)
+	if !ok || len(properties) != 0 {
+		t.Fatalf("parameters.properties = %#v, want empty object", parameters["properties"])
+	}
 }
 
 func TestNewRequiresModelButNotAPIKey(t *testing.T) {
@@ -193,14 +260,14 @@ func TestStreamCompletionAppliesCustomAuthAndHeaders(t *testing.T) {
 func TestStreamCompletionEmitsTextUsageAndDone(t *testing.T) {
 	provider := newTestProvider(t, func(w http.ResponseWriter, r *http.Request) {
 		writeSSE(w, `{"choices":[{"delta":{"content":"hello "}}]}`)
-		writeSSE(w, `{"choices":[{"delta":{"content":"zero"}}],"usage":{"prompt_tokens":12,"completion_tokens":5,"prompt_tokens_details":{"cached_tokens":3}}}`)
+		writeSSE(w, `{"choices":[{"delta":{"content":"zero"}}],"usage":{"prompt_tokens":12,"completion_tokens":5,"prompt_tokens_details":{"cached_tokens":3,"cache_write_tokens":2}}}`)
 		writeSSE(w, `[DONE]`)
 	})
 
 	events := collectProviderEvents(t, provider)
 	assertEvent(t, events[0], zeroruntime.StreamEventText, "hello ")
 	assertEvent(t, events[1], zeroruntime.StreamEventText, "zero")
-	if events[2].Type != zeroruntime.StreamEventUsage || events[2].Usage.PromptTokens != 12 || events[2].Usage.CompletionTokens != 5 || events[2].Usage.CachedInputTokens != 3 {
+	if events[2].Type != zeroruntime.StreamEventUsage || events[2].Usage.PromptTokens != 12 || events[2].Usage.CompletionTokens != 5 || events[2].Usage.CachedInputTokens != 3 || events[2].Usage.CacheWriteTokens != 2 {
 		t.Fatalf("unexpected usage event: %#v", events[2])
 	}
 	if events[3].Type != zeroruntime.StreamEventDone {
@@ -1479,3 +1546,66 @@ func TestOpenAIRequestPreservesCacheablePrefixAcrossTurns(t *testing.T) {
 		t.Fatalf("wire prompt cache key must remain stable: first=%#v second=%#v", first["prompt_cache_key"], second["prompt_cache_key"])
 	}
 }
+
+// TestStreamCompletionSerializesNonMapPropertiesAsEmptyObject locks in the
+// normalizeToolParameters type-assert branch: when a tool's parameters carry a
+// `properties` field whose value is a non-map (e.g., an empty slice), it must
+// be normalized to "properties":{} on the wire, never "properties":[] or
+// "properties":null.
+func TestStreamCompletionSerializesNonMapPropertiesAsEmptyObject(t *testing.T) {
+	var gotBody map[string]any
+	var gotRaw []byte
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		raw, err := io.ReadAll(r.Body)
+		if err != nil {
+			t.Fatalf("read request body: %v", err)
+		}
+		gotRaw = raw
+		if err := json.Unmarshal(raw, &gotBody); err != nil {
+			t.Fatalf("decode request body: %v", err)
+		}
+		writeSSE(w, `{"choices":[]}`)
+		writeSSE(w, `[DONE]`)
+	}))
+	defer server.Close()
+
+	provider, err := New(Options{
+		APIKey:  "sk-secret",
+		BaseURL: server.URL + "/",
+		Model:   "gpt-test",
+	})
+	if err != nil {
+		t.Fatalf("New returned error: %v", err)
+	}
+
+	stream, err := provider.StreamCompletion(context.Background(), zeroruntime.CompletionRequest{
+		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "hi"}},
+		Tools: []zeroruntime.ToolDefinition{{
+			Name:        "no_args",
+			Description: "Takes no arguments",
+			Parameters:  map[string]any{"type": "object", "properties": []any{}},
+		}},
+	})
+	if err != nil {
+		t.Fatalf("StreamCompletion returned error: %v", err)
+	}
+	drain(stream)
+
+	if !strings.Contains(string(gotRaw), `"properties":{}`) {
+		t.Fatalf("request body must serialize properties as an empty object, got: %s", gotRaw)
+	}
+	if strings.Contains(string(gotRaw), `"properties":null`) {
+		t.Fatalf("request body must not serialize properties as null, got: %s", gotRaw)
+	}
+	if strings.Contains(string(gotRaw), `"properties":[]`) {
+		t.Fatalf("request body must not serialize properties as an empty array, got: %s", gotRaw)
+	}
+	tools := gotBody["tools"].([]any)
+	tool := tools[0].(map[string]any)
+	functionDefinition := tool["function"].(map[string]any)
+	parameters := functionDefinition["parameters"].(map[string]any)
+	properties, ok := parameters["properties"].(map[string]any)
+	if !ok || len(properties) != 0 {
+		t.Fatalf("parameters.properties = %#v, want empty object", parameters["properties"])
+	}
+}

internal/providers/openai/session.go

@@ -195,7 +195,12 @@ func (s *turnSession) computeFingerprint(request zeroruntime.CompletionRequest)
 func wireToolsDigest(tools []zeroruntime.ToolDefinition) string {
 	rendered := make([]string, 0, len(tools))
 	for _, tool := range tools {
-		schema, err := json.Marshal(tool.Parameters)
+		wireShape := struct {
+			Type       zeroruntime.ToolDefinitionType    `json:"type,omitempty"`
+			Parameters map[string]any                    `json:"parameters,omitempty"`
+			Format     *zeroruntime.ToolDefinitionFormat `json:"format,omitempty"`
+		}{Type: tool.Type, Parameters: tool.Parameters, Format: tool.Format}
+		schema, err := json.Marshal(wireShape)
 		if err != nil {
 			rendered = append(rendered, tool.Name+"\n"+tool.Description+"\n__non_json:"+tool.Name)
 			continue

internal/providers/openai/types.go

@@ -109,7 +109,8 @@ type usage struct {
 }
 
 type promptTokenDetails struct {
-	CachedTokens int `json:"cached_tokens"`
+	CachedTokens     int `json:"cached_tokens"`
+	CacheWriteTokens int `json:"cache_write_tokens"`
 }
 
 type completionTokenDetails struct {

internal/providers/providerio/export_test.go

@@ -1,14 +0,0 @@
-// Test seams: helpers only test code uses, kept out of the production binary.
-package providerio
-
-import (
-	"bufio"
-	"io"
-)
-
-// ScanSSEData parses Server-Sent Event data fields from a streaming response.
-func ScanSSEData(reader io.Reader, handle func(data string) bool) error {
-	scanner := bufio.NewScanner(reader)
-	scanner.Buffer(make([]byte, 0, 4096), maxSSELineBytes)
-	return scanSSEPayloads(scanner, handle, nil)
-}

internal/providers/turn_session.go

@@ -15,9 +15,27 @@ import (
 // value (e.g. "1") to enable — the same boolean idiom as ZERO_FORMAT_ON_WRITE.
 const openaiTurnSessionEnv = "ZERO_OPENAI_TURN_SESSION"
 
+// ChatGPT Responses sessions are enabled by default for their native provider.
+// Setting this to 0/false/off restores the stateless HTTP/SSE transport.
+const chatGPTTurnSessionEnv = "ZERO_CHATGPT_TURN_SESSION"
+
 func openaiTurnSessionEnabled() bool {
 	value := strings.TrimSpace(os.Getenv(openaiTurnSessionEnv))
-	return value != "" && value != "0" && !strings.EqualFold(value, "false")
+	return value != "" && !explicitEnvFalse(value)
+}
+
+func chatGPTTurnSessionEnabled() bool {
+	value := strings.TrimSpace(os.Getenv(chatGPTTurnSessionEnv))
+	return value == "" || !explicitEnvFalse(value)
+}
+
+func explicitEnvFalse(value string) bool {
+	switch strings.ToLower(strings.TrimSpace(value)) {
+	case "0", "false", "off":
+		return true
+	default:
+		return false
+	}
 }
 
 // OptimizedTurnSessions returns the gated optimized TurnSessionProvider for an
@@ -25,20 +43,33 @@ func openaiTurnSessionEnabled() bool {
 // is ineligible. Callers leave agent Options.TurnSessionProvider nil on false,
 // so the loop's default wrap keeps today's behavior byte-identical.
 //
-// Eligibility is deliberately narrow: the resolved provider kind must be
-// official OpenAI (NOT openai-compatible gateways — the constructor merges the
-// two, so this branches on the resolved kind explicitly), not the ChatGPT
-// Codex catalog, and the provider value must be the concrete *openai.Provider
-// (a fake, a Codex provider, or nil falls back to the default path safely).
-// No base-URL check on top of the kind: prewarm and fingerprint telemetry are
-// harmless against any host, and kind==openai mirrors the existing
-// official-OpenAI precedent used for prompt_cache_key.
+// Eligibility is deliberately narrow: native ChatGPT Responses uses its
+// concrete Codex provider and defaults on with a kill switch; official OpenAI
+// chat-completions keeps its existing opt-in prewarm session. Compatible
+// gateways and foreign provider values always retain the default adapter.
 func OptimizedTurnSessions(profile config.ProviderProfile, provider zeroruntime.Provider, options Options) (zeroruntime.TurnSessionProvider, bool) {
-	if !openaiTurnSessionEnabled() {
+	resolved, err := resolveProfile(profile, options)
+	if err != nil {
 		return nil, false
 	}
-	resolved, err := resolveProfile(profile, options)
-	if err != nil || resolved.providerKind != config.ProviderKindOpenAI || isCodexCatalog(profile, resolved) {
+	if isCodexCatalog(profile, resolved) {
+		if !chatGPTTurnSessionEnabled() {
+			return nil, false
+		}
+		concrete, ok := provider.(*openai.CodexProvider)
+		if !ok {
+			return nil, false
+		}
+		caps, err := resolveCapabilities(profile, options)
+		if err != nil {
+			return nil, false
+		}
+		return openai.NewCodexTurnSessionProvider(concrete, caps), true
+	}
+	if resolved.providerKind != config.ProviderKindOpenAI {
+		return nil, false
+	}
+	if !openaiTurnSessionEnabled() {
 		return nil, false
 	}
 	concrete, ok := provider.(*openai.Provider)

internal/providers/turn_session_gate_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/Gitlawb/zero/internal/config"
+	"github.com/Gitlawb/zero/internal/providers/openai"
 	"github.com/Gitlawb/zero/internal/zeroruntime"
 )
 
@@ -45,7 +46,7 @@ func TestOptimizedTurnSessionsDefaultOff(t *testing.T) {
 func TestOptimizedTurnSessionsFalseyValues(t *testing.T) {
 	profile := openaiEligibleProfile()
 	provider := buildGateProvider(t, profile)
-	for _, value := range []string{"0", "false", "FALSE", "False", " ", ""} {
+	for _, value := range []string{"0", "false", "FALSE", "False", "off", "OFF", " ", ""} {
 		t.Setenv(openaiTurnSessionEnv, value)
 		if _, ok := OptimizedTurnSessions(profile, provider, Options{}); ok {
 			t.Fatalf("gate enabled for falsey value %q", value)
@@ -59,6 +60,21 @@ func TestOptimizedTurnSessionsFalseyValues(t *testing.T) {
 	}
 }
 
+func TestChatGPTTurnSessionGateValues(t *testing.T) {
+	for _, value := range []string{"0", "false", "FALSE", "off", "OFF"} {
+		t.Setenv(chatGPTTurnSessionEnv, value)
+		if chatGPTTurnSessionEnabled() {
+			t.Fatalf("ChatGPT gate enabled for falsey value %q", value)
+		}
+	}
+	for _, value := range []string{"", " ", "1", "true", "on"} {
+		t.Setenv(chatGPTTurnSessionEnv, value)
+		if !chatGPTTurnSessionEnabled() {
+			t.Fatalf("ChatGPT gate disabled for default/truthy value %q", value)
+		}
+	}
+}
+
 func TestOptimizedTurnSessionsOpenAIEligible(t *testing.T) {
 	t.Setenv(openaiTurnSessionEnv, "1")
 	profile := openaiEligibleProfile()
@@ -88,13 +104,64 @@ func TestOptimizedTurnSessionsRejectsCompatible(t *testing.T) {
 }
 
 func TestOptimizedTurnSessionsRejectsCodexCatalog(t *testing.T) {
-	t.Setenv(openaiTurnSessionEnv, "1")
+	t.Setenv(chatGPTTurnSessionEnv, "0")
+	profile := openaiEligibleProfile()
+	profile.Name = "chatgpt"
+	profile.CatalogID = "chatgpt"
+	if _, ok := OptimizedTurnSessions(profile, buildChatGPTGateProvider(t, profile), Options{}); ok {
+		t.Fatal("the ChatGPT Codex catalog must honor the turn-session kill switch")
+	}
+}
+
+func TestOptimizedTurnSessionsEnablesChatGPTResponsesByDefault(t *testing.T) {
+	t.Setenv(chatGPTTurnSessionEnv, "")
+	profile := openaiEligibleProfile()
+	profile.Name = "chatgpt"
+	profile.CatalogID = "chatgpt"
+	provider := buildChatGPTGateProvider(t, profile)
+
+	turnSessions, ok := OptimizedTurnSessions(profile, provider, Options{})
+	if !ok || turnSessions == nil {
+		t.Fatal("ChatGPT Responses provider did not receive its default turn session")
+	}
+	if got := turnSessions.Capabilities().Model; got != profile.Model {
+		t.Fatalf("Capabilities().Model = %q, want %q", got, profile.Model)
+	}
+}
+
+func TestOptimizedTurnSessionsRecognizesCompatibleLabeledChatGPTProfile(t *testing.T) {
+	t.Setenv(chatGPTTurnSessionEnv, "")
+	profile := openaiEligibleProfile()
+	profile.Name = "chatgpt"
+	profile.CatalogID = "chatgpt"
+	profile.ProviderKind = config.ProviderKindOpenAICompatible
+	if turnSessions, ok := OptimizedTurnSessions(profile, buildChatGPTGateProvider(t, profile), Options{}); !ok || turnSessions == nil {
+		t.Fatal("ChatGPT catalog profile must use its native session regardless of the stored compatibility label")
+	}
+}
+
+func buildChatGPTGateProvider(t *testing.T, profile config.ProviderProfile) *openai.CodexProvider {
+	t.Helper()
+	provider, err := openai.NewCodexProvider(openai.CodexOptions{
+		Options: openai.Options{
+			APIKey:  "test-token",
+			BaseURL: "https://chatgpt.example/backend-api/codex",
+			Model:   profile.Model,
+		},
+		AccountID: "account-test",
+	})
+	if err != nil {
+		t.Fatalf("NewCodexProvider: %v", err)
+	}
+	return provider
+}
+
+func TestOptimizedTurnSessionsRejectsNonCodexProviderForChatGPT(t *testing.T) {
+	t.Setenv(chatGPTTurnSessionEnv, "1")
 	profile := openaiEligibleProfile()
 	profile.CatalogID = "chatgpt"
-	// Build the provider from the base profile: the point under test is the
-	// catalog check, not Codex construction (which needs OAuth wiring).
 	if _, ok := OptimizedTurnSessions(profile, buildGateProvider(t, openaiEligibleProfile()), Options{}); ok {
-		t.Fatal("the ChatGPT Codex catalog must not get the optimized session")
+		t.Fatal("a ChatGPT catalog profile with a non-Codex provider must use the default session")
 	}
 }