address CodeRabbit review on #349

- loop.go: gate stall-retry on a turn-level forwardedAnything flag (wrapped
  callbacks), so a retry never re-streams on top of output already forwarded earlier
  in the turn (e.g. across the reactive-compaction retry). New test covers a
  reasoning-then-stall (collected.Text empty but output forwarded).
- loop.go: route a reissued stream's non-stall error through the SAME recovery as
  the initial stream (image-rejection wrapping / context-limit compaction) via a
  shared recoverStreamError closure, instead of returning it raw.
- exec.go: drop the hardcoded worker/explorer/code-review guidance from the
  unknown-specialist error; rely on the dynamically-rendered available list (a
  custom registry may not have those names).
- streamer.go: kill-signal message lists OOM/timeout/cancellation evenhandedly
  instead of asserting OOM (the branch also covers timeouts/cancellations).
- launcher_specialist.go + exec.go: preserve the child SessionID on a post-start
  failure too, so FailWithSession keeps those failed members drillable.
- model.go: block /turns while a run is active (mid-run change would make the
  inherited ZERO_MAX_TURNS budget inconsistent for later-spawned sub-agents).

internal/agent/compaction.go

@@ -280,6 +280,25 @@ func isContextLimitError(message string) bool {
 	return false
 }
 
+// isStreamTimeoutError reports whether a streamed error is a provider stream
+// idle/stall timeout (providerio surfaces these as "idle timeout after …" /
+// "no output for …" / "stream stalled"). Such a turn produced nothing, so when
+// no content was forwarded yet it can be safely re-issued on a fresh connection
+// (see the stall-retry in the agent loop). Substring + case-insensitive to
+// tolerate the prefixed "provider stream error: …" wrapping.
+func isStreamTimeoutError(message string) bool {
+	lowered := strings.ToLower(strings.TrimSpace(message))
+	if lowered == "" {
+		return false
+	}
+	for _, needle := range []string{"idle timeout after", "no output for", "stream stalled"} {
+		if strings.Contains(lowered, needle) {
+			return true
+		}
+	}
+	return false
+}
+
 // compactionState carries the per-run state the agent loop needs to compact a
 // conversation safely. It is created once per Run and is a no-op whenever
 // options.ContextWindow <= 0.

internal/agent/decode_args_test.go

@@ -0,0 +1,99 @@
+package agent
+
+import "testing"
+
+// decodeToolArguments must (a) decode a normal single-object payload unchanged,
+// (b) tolerate a weak model packing multiple concatenated top-level JSON objects
+// into one arguments string by decoding the FIRST object and ignoring the rest
+// (the minimax-m3 "invalid character '{' after top-level value" failure), and
+// (c) still reject a genuinely malformed/truncated first object.
+func TestDecodeToolArguments(t *testing.T) {
+	t.Run("single object decodes normally", func(t *testing.T) {
+		var a map[string]any
+		if err := decodeToolArguments(`{"path":"x"}`, &a); err != nil {
+			t.Fatalf("err = %v, want nil", err)
+		}
+		if a["path"] != "x" {
+			t.Fatalf("decoded %v, want path=x", a)
+		}
+	})
+
+	t.Run("concatenated objects decode the first, ignore trailing", func(t *testing.T) {
+		var b map[string]any
+		if err := decodeToolArguments(`{"path":"first"}{"path":"second"}`, &b); err != nil {
+			t.Fatalf("multi-object should decode the first, got err = %v", err)
+		}
+		if b["path"] != "first" {
+			t.Fatalf("decoded %v, want the first object (path=first)", b)
+		}
+	})
+
+	t.Run("distinct tools' args concatenated (real minimax case): first object used", func(t *testing.T) {
+		var c map[string]any
+		if err := decodeToolArguments(`{"plan":[1,2]}{"cmd":"go version"}`, &c); err != nil {
+			t.Fatalf("err = %v, want nil", err)
+		}
+		if _, ok := c["plan"]; !ok || c["cmd"] != nil {
+			t.Fatalf("decoded %v, want only the first object's keys", c)
+		}
+	})
+
+	t.Run("truncated first object still errors", func(t *testing.T) {
+		var d map[string]any
+		if err := decodeToolArguments(`{"path":`, &d); err == nil {
+			t.Fatal("truncated JSON must still error")
+		}
+	})
+
+	t.Run("non-JSON trailing garbage still errors (not masked)", func(t *testing.T) {
+		var g map[string]any
+		if err := decodeToolArguments(`{"x":1}xyz`, &g); err == nil {
+			t.Fatal("a valid first object followed by non-JSON garbage must still error")
+		}
+	})
+
+	t.Run("recoverableToolArguments: only whole-JSON trailing is tolerated", func(t *testing.T) {
+		cases := []struct {
+			in    string
+			ok    bool
+			first string
+		}{
+			{`{"a":1}`, true, `{"a":1}`},
+			{`{"a":1}{"b":2}`, true, `{"a":1}`},
+			{`{"a":1}  {"b":2}  `, true, `{"a":1}`},
+			{`{"a":1}xyz`, false, ""},
+			{`{"a":`, false, ""},
+			{`   `, false, ""},
+		}
+		for _, c := range cases {
+			first, ok := recoverableToolArguments(c.in)
+			if ok != c.ok || (ok && first != c.first) {
+				t.Fatalf("recoverableToolArguments(%q) = (%q,%v), want (%q,%v)", c.in, first, ok, c.first, c.ok)
+			}
+		}
+	})
+
+	t.Run("historySafeToolCalls recovers the first object, not {}", func(t *testing.T) {
+		out := historySafeToolCalls([]ToolCall{
+			{ID: "c1", Name: "read_file", Arguments: `{"path":"README.md"}{"path":"AGENTS.md"}`}, // concatenated -> first
+			{ID: "c2", Name: "read_file", Arguments: `{"path":"x"}xyz`},                          // garbage -> {}
+			{ID: "c3", Name: "read_file", Arguments: `{"path":"ok"}`},                            // valid -> unchanged
+		})
+		if out[0].Arguments != `{"path":"README.md"}` {
+			t.Fatalf("concatenated args should record the first object, got %q", out[0].Arguments)
+		}
+		if out[1].Arguments != "{}" {
+			t.Fatalf("garbage-trailing args should record {}, got %q", out[1].Arguments)
+		}
+		if out[2].Arguments != `{"path":"ok"}` {
+			t.Fatalf("valid args should be unchanged, got %q", out[2].Arguments)
+		}
+	})
+
+	t.Run("whitespace-only errors (caller guards empty)", func(t *testing.T) {
+		var e map[string]any
+		if err := decodeToolArguments("   ", &e); err == nil {
+			t.Fatal("whitespace-only must error")
+		}
+	})
+}

internal/agent/loop.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"sort"
 	"strings"
 	"sync"
@@ -20,6 +21,12 @@ import (
 const maxTurnsAnswer = "Agent reached maximum number of turns without a final answer."
 const maxTurnsFinalAnswerPrompt = "You have reached the tool-turn limit. Do not call tools. Give a concise final answer now: summarize what you completed, what you found, and any remaining blockers."
 
+// maxStreamStallRetries bounds how many times a turn that timed out (idle/stall)
+// WITH NO OUTPUT yet is re-issued on a fresh connection before giving up. Only
+// the no-output case is retried (a partial turn would duplicate), so this is a
+// safe recovery for a stalled/dead pooled connection.
+const maxStreamStallRetries = 2
+
 const (
 	toolResultMetaControl       = "control"
 	toolResultControlSpecReview = "spec_review_required"
@@ -203,55 +210,72 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 			}
 		}
 
-		collected := zeroruntime.CollectStreamWithOptions(ctx, stream, zeroruntime.CollectOptions{
-			OnText:          options.OnText,
-			OnReasoning:     options.OnReasoning,
-			OnUsage:         options.OnUsage,
-			OnToolCallStart: options.OnToolCallStart,
-			OnToolCallDelta: options.OnToolCallDelta,
-		})
-		if collected.Error != "" {
-			collectedErr := errors.New(collected.Error)
-			if isImageRejectionError(collectedErr) {
-				result.Messages = copyMessages(messages)
-				return result, fmt.Errorf("model %s rejected the image: %s. The model may not support image input — try switching to a vision-capable model (claude, gpt-4o, gemini)", options.Model, collected.Error)
+		// Wrapped callbacks flag ANY output forwarded this turn, so a stall retry
+		// never re-streams on top of output the user already saw — even across the
+		// reactive-compaction retry below, which overwrites `collected`.
+		forwardedAnything := false
+		mark := func() { forwardedAnything = true }
+		// OnUsage is telemetry, not visible output, so it does NOT mark
+		// forwardedAnything: a provider that emits an early usage event (e.g. prompt
+		// tokens) then stalls with no content must still be safely retried. The gate
+		// only guards against re-streaming output the user actually SAW.
+		forwardingOpts := zeroruntime.CollectOptions{OnUsage: options.OnUsage}
+		if options.OnText != nil {
+			forwardingOpts.OnText = func(s string) { mark(); options.OnText(s) }
+		}
+		if options.OnReasoning != nil {
+			forwardingOpts.OnReasoning = func(s string) { mark(); options.OnReasoning(s) }
+		}
+		if options.OnToolCallStart != nil {
+			forwardingOpts.OnToolCallStart = func(id, name string) { mark(); options.OnToolCallStart(id, name) }
+		}
+		if options.OnToolCallDelta != nil {
+			forwardingOpts.OnToolCallDelta = func(id, fragment string) { mark(); options.OnToolCallDelta(id, fragment) }
+		}
+		// recoverStreamError applies the same non-stall recovery the initial stream
+		// gets to ANY collected error — including one from a reissued (stall-retry)
+		// stream: an image rejection gets the friendly wrapping, and a context limit
+		// gets one compaction + reactive reissue (omitting visible callbacks, since
+		// any pre-error output was already forwarded). It returns the possibly-updated
+		// collected and a non-nil stop error when the run must end now.
+		recoverStreamError := func(collected zeroruntime.CollectedStream) (zeroruntime.CollectedStream, error) {
+			if isImageRejectionError(errors.New(collected.Error)) {
+				return collected, fmt.Errorf("model %s rejected the image: %s. The model may not support image input — try switching to a vision-capable model (claude, gpt-4o, gemini)", options.Model, collected.Error)
 			}
-			// REACTIVE compaction: the streamed error may also be a context
-			// limit (some providers surface it mid-stream). Compact and retry
-			// the same turn once before giving up.
+			// REACTIVE compaction: the streamed error may also be a context limit
+			// (some providers surface it mid-stream). Compact and retry once.
 			if compacted, retried, retryErr := compactor.recover(ctx, provider, messages, request.Tools, collected.Error); retried {
 				messages = compacted
 				if retryErr != nil {
-					result.Messages = copyMessages(messages)
-					return result, retryErr
+					return collected, retryErr
 				}
-				// Reuse the SAME active-mode partition (exposed) from this
-				// turn rather than the bare toolDefinitions: exposed depends on
-				// registry+loaded (not the messages), so they stay valid after compaction.
-				// Routing through an empty-loaded partition here would re-hide every
-				// already-loaded deferred tool.
+				// Reuse the SAME active-mode partition (exposed) from this turn rather
+				// than the bare toolDefinitions: exposed depends on registry+loaded (not
+				// the messages), so it stays valid after compaction.
 				retryRequest := zeroruntime.CompletionRequest{
 					Messages:        copyMessages(messages),
 					Tools:           exposed,
 					ReasoningEffort: options.ReasoningEffort,
 				}
-				// Pre-content reconnect of a mid-stream disconnect: route the connect
-				// through the reconnect helper too (AUDIT-L1).
 				retryStream, retryStreamErr := streamWithReconnect(ctx, provider, retryRequest, reconnectNoticeFor(options))
 				if retryStreamErr != nil {
-					result.Messages = copyMessages(messages)
-					return result, retryStreamErr
+					return collected, retryStreamErr
 				}
-				// Omit OnText on the reactive retry: when the original error
-				// surfaced MID-stream, partial text was already forwarded to the
-				// user. Re-streaming the retried response on top of it would
-				// duplicate output. OnUsage IS kept so token telemetry/budgeting
-				// still counts the successful retry. The retried text is captured
-				// in collected.Text and becomes the turn's assistant message.
 				collected = zeroruntime.CollectStreamWithOptions(ctx, retryStream, zeroruntime.CollectOptions{
 					OnUsage: options.OnUsage,
 				})
 			}
+			return collected, nil
+		}
+
+		collected := zeroruntime.CollectStreamWithOptions(ctx, stream, forwardingOpts)
+		if collected.Error != "" {
+			updated, stop := recoverStreamError(collected)
+			collected = updated
+			if stop != nil {
+				result.Messages = copyMessages(messages)
+				return result, stop
+			}
 		}
 		// Check ctx first: on cancellation helpers.go sets collected.Error to
 		// ctx.Err().Error(), so returning errors.New(collected.Error) would lose
@@ -260,9 +284,45 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 			result.Messages = copyMessages(messages)
 			return result, ctx.Err()
 		}
+		// A stream idle/stall timeout with NO output forwarded yet this turn can be
+		// safely re-issued on a fresh connection — nothing was shown, so there's no
+		// duplication (this recovers the macOS stale-pooled-connection hang when it
+		// slips past the transport's response-header timeout). A turn that already
+		// streamed partial text/tool-calls is NOT retried (it would duplicate) and
+		// falls through to the error return below. Capped + exponential backoff.
+		for attempt := 1; attempt <= maxStreamStallRetries &&
+			isStreamTimeoutError(collected.Error) && !forwardedAnything &&
+			collected.Text == "" && len(collected.ToolCalls) == 0; attempt++ {
+			if err := sleepWithContext(ctx, backoffFor(attempt)); err != nil {
+				result.Messages = copyMessages(messages)
+				return result, err
+			}
+			retryRequest := zeroruntime.CompletionRequest{
+				Messages:        copyMessages(messages),
+				Tools:           exposed,
+				ReasoningEffort: options.ReasoningEffort,
+			}
+			retryStream, retryErr := streamWithReconnect(ctx, provider, retryRequest, reconnectNoticeFor(options))
+			if retryErr != nil {
+				result.Messages = copyMessages(messages)
+				return result, retryErr
+			}
+			collected = zeroruntime.CollectStreamWithOptions(ctx, retryStream, forwardingOpts)
+		}
 		if collected.Error != "" {
-			result.Messages = copyMessages(messages)
-			return result, errors.New(collected.Error)
+			// Route a reissued stream's non-stall error through the SAME recovery as
+			// the initial stream (image-rejection wrapping / context-limit compaction)
+			// rather than returning it raw.
+			updated, stop := recoverStreamError(collected)
+			collected = updated
+			if stop != nil {
+				result.Messages = copyMessages(messages)
+				return result, stop
+			}
+			if collected.Error != "" {
+				result.Messages = copyMessages(messages)
+				return result, errors.New(collected.Error)
+			}
 		}
 
 		// Carry the turn's terminal stop reason so a final answer cut off at the
@@ -615,8 +675,20 @@ func historySafeToolCalls(calls []ToolCall) []ToolCall {
 	for i, call := range calls {
 		safe[i] = call
 		args := strings.TrimSpace(call.Arguments)
-		if args == "" || !json.Valid([]byte(args)) {
+		switch {
+		case args == "":
 			safe[i].Arguments = "{}"
+		case json.Valid([]byte(args)):
+			// already a single valid JSON value — keep as-is
+		default:
+			// Recover the first object for the concatenated case so the replayed
+			// transcript matches what executeToolCall actually ran; otherwise (real
+			// corruption) fall back to an empty object.
+			if first, ok := recoverableToolArguments(args); ok {
+				safe[i].Arguments = first
+			} else {
+				safe[i].Arguments = "{}"
+			}
 		}
 	}
 	return safe
@@ -641,10 +713,53 @@ func toolSchemaJSON(registry *tools.Registry, name string) string {
 // is a non-nil ABORT error only when the call demands the whole run stop (a
 // canceled/timed-out ask_user prompt) rather than continuing — every ordinary
 // success or tool error returns a nil abort error.
+// recoverableToolArguments inspects a tool call's raw JSON arguments. It returns
+// the raw text of the FIRST JSON value when the payload is one value optionally
+// followed by additional WHOLE JSON values (the weak-model concatenated case, e.g.
+// `{A}{B}`). ok is false when the payload is genuinely malformed: a bad/truncated
+// first value, OR trailing NON-JSON garbage after a valid first value (e.g.
+// `{"x":1}xyz`) — that case must still error, not be silently accepted. Sharing
+// this between dispatch and replay-history keeps them consistent: only a cleanly
+// recoverable first object is ever used.
+func recoverableToolArguments(arguments string) (first string, ok bool) {
+	dec := json.NewDecoder(strings.NewReader(arguments))
+	var head json.RawMessage
+	if err := dec.Decode(&head); err != nil {
+		return "", false
+	}
+	// The remainder must be only whole JSON values (or nothing); any decode error
+	// other than EOF means trailing garbage — reject so corruption still surfaces.
+	for {
+		var rest json.RawMessage
+		if err := dec.Decode(&rest); err != nil {
+			if errors.Is(err, io.EOF) {
+				return strings.TrimSpace(string(head)), true
+			}
+			return "", false
+		}
+	}
+}
+
+// decodeToolArguments decodes a tool call's JSON arguments into v. It tolerates a
+// weaker model that packs MULTIPLE concatenated top-level JSON objects into one
+// arguments string (`{A}{B}`) — the cause of "invalid character '{' after top-level
+// value" failures with small models like minimax-m3 — by decoding the FIRST object
+// and ignoring the trailing WHOLE JSON values, so the primary intended call runs.
+// A genuinely malformed payload (bad/truncated first object, or non-JSON trailing
+// garbage) still returns the real parse error; a standard single-object payload
+// decodes exactly as before.
+func decodeToolArguments(arguments string, v any) error {
+	if first, ok := recoverableToolArguments(arguments); ok {
+		return json.Unmarshal([]byte(first), v)
+	}
+	// Not cleanly recoverable — surface the genuine parse error.
+	return json.Unmarshal([]byte(arguments), v)
+}
+
 func executeToolCall(ctx context.Context, registry *tools.Registry, call ToolCall, permissionMode PermissionMode, options Options) (ToolResult, error) {
 	args := map[string]any{}
 	if call.Arguments != "" {
-		if err := json.Unmarshal([]byte(call.Arguments), &args); err != nil {
+		if err := decodeToolArguments(call.Arguments, &args); err != nil {
 			return ToolResult{
 				ToolCallID: call.ID,
 				Name:       call.Name,

internal/agent/loop_test.go

@@ -1053,7 +1053,10 @@ func TestRunSanitizesMalformedToolCallArgumentsBeforeRetry(t *testing.T) {
 		turns: [][]zeroruntime.StreamEvent{
 			{
 				{Type: zeroruntime.StreamEventToolCallStart, ToolCallID: "call-1", ToolName: "read_file"},
-				{Type: zeroruntime.StreamEventToolCallDelta, ToolCallID: "call-1", ArgumentsFragment: `{"path":"README.md"}{"path":"AGENTS.md"}`},
+				// Genuinely malformed (truncated) args: still error -> sanitize -> retry.
+				// (Concatenated multi-object args are now tolerated; see
+				// TestRunRecoversFirstObjectFromConcatenatedToolArgs.)
+				{Type: zeroruntime.StreamEventToolCallDelta, ToolCallID: "call-1", ArgumentsFragment: `{"path":"README.md"`},
 				{Type: zeroruntime.StreamEventToolCallEnd, ToolCallID: "call-1"},
 				{Type: zeroruntime.StreamEventDone},
 			},
@@ -1103,6 +1106,53 @@ func TestRunSanitizesMalformedToolCallArgumentsBeforeRetry(t *testing.T) {
 	}
 }
 
+// A weak model (e.g. minimax-m3) that packs MULTIPLE concatenated JSON objects into
+// one tool-call slot must RECOVER the first object and run the call, not fail with
+// "invalid character '{' after top-level value". The trailing object(s) are dropped
+// (the model re-issues them on a later turn if still needed).
+func TestRunRecoversFirstObjectFromConcatenatedToolArgs(t *testing.T) {
+	root := t.TempDir()
+	if err := os.WriteFile(filepath.Join(root, "README.md"), []byte("hello readme"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	registry := tools.NewRegistry()
+	registry.Register(tools.NewReadFileTool(root))
+	provider := &mockProvider{
+		turns: [][]zeroruntime.StreamEvent{
+			{
+				{Type: zeroruntime.StreamEventToolCallStart, ToolCallID: "call-1", ToolName: "read_file"},
+				{Type: zeroruntime.StreamEventToolCallDelta, ToolCallID: "call-1", ArgumentsFragment: `{"path":"README.md"}{"path":"AGENTS.md"}`},
+				{Type: zeroruntime.StreamEventToolCallEnd, ToolCallID: "call-1"},
+				{Type: zeroruntime.StreamEventDone},
+			},
+			{
+				{Type: zeroruntime.StreamEventText, Content: "done"},
+				{Type: zeroruntime.StreamEventDone},
+			},
+		},
+	}
+
+	result, err := Run(context.Background(), "read", provider, Options{Registry: registry, MaxTurns: 2})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if result.FinalAnswer != "done" {
+		t.Fatalf("final answer = %q, want done", result.FinalAnswer)
+	}
+	var toolResult string
+	for _, message := range provider.requests[1].Messages {
+		if message.Role == zeroruntime.MessageRoleTool {
+			toolResult = message.Content
+		}
+	}
+	if strings.Contains(toolResult, "Failed to parse arguments") {
+		t.Fatalf("concatenated args should recover the first object, not fail to parse: %q", toolResult)
+	}
+	if !strings.Contains(toolResult, "hello readme") {
+		t.Fatalf("expected README.md contents (the first object's path), got %q", toolResult)
+	}
+}
+
 func TestRunDefersSelfCorrectFeedbackUntilAfterToolBatch(t *testing.T) {
 	// A single assistant turn with two tool calls where the first mutates and
 	// self-correct fails must keep both tool_results contiguous, with the feedback

internal/agent/stall_retry_test.go

@@ -0,0 +1,122 @@
+package agent
+
+import (
+	"context"
+	"sync/atomic"
+	"testing"
+
+	"github.com/Gitlawb/zero/internal/tools"
+	"github.com/Gitlawb/zero/internal/zeroruntime"
+)
+
+// stallProvider connects successfully (HTTP 200) but the stream emits a stall/idle
+// timeout error for the first stallBefore calls, then succeeds with "done". When
+// partialText is set it emits that text BEFORE the stall, simulating a stall after
+// partial output (which must NOT be retried — re-issuing would duplicate it).
+type stallProvider struct {
+	calls         int32
+	stallBefore   int32
+	partialText   string
+	reasoningText string
+}
+
+func (p *stallProvider) StreamCompletion(_ context.Context, _ zeroruntime.CompletionRequest) (<-chan zeroruntime.StreamEvent, error) {
+	n := atomic.AddInt32(&p.calls, 1)
+	ch := make(chan zeroruntime.StreamEvent, 3)
+	if n <= p.stallBefore {
+		if p.partialText != "" {
+			ch <- zeroruntime.StreamEvent{Type: zeroruntime.StreamEventText, Content: p.partialText}
+		}
+		if p.reasoningText != "" {
+			ch <- zeroruntime.StreamEvent{Type: zeroruntime.StreamEventReasoning, Content: p.reasoningText}
+		}
+		ch <- zeroruntime.StreamEvent{
+			Type:  zeroruntime.StreamEventError,
+			Error: "provider stream error: no output for 10m (the model produced nothing)",
+		}
+		close(ch)
+		return ch, nil
+	}
+	ch <- zeroruntime.StreamEvent{Type: zeroruntime.StreamEventText, Content: "done"}
+	ch <- zeroruntime.StreamEvent{Type: zeroruntime.StreamEventDone}
+	close(ch)
+	return ch, nil
+}
+
+// A no-output stall is re-issued on a fresh connection and recovers — this is the
+// macOS stale-pooled-connection hang turned into an automatic recovery.
+func TestRunRetriesStreamStallWithNoOutput(t *testing.T) {
+	p := &stallProvider{stallBefore: 1}
+	result, err := Run(context.Background(), "go", p, Options{Registry: tools.NewRegistry()})
+	if err != nil {
+		t.Fatalf("a no-output stall should retry to success, got %v", err)
+	}
+	if result.FinalAnswer != "done" {
+		t.Fatalf("final answer = %q, want %q", result.FinalAnswer, "done")
+	}
+	if got := atomic.LoadInt32(&p.calls); got != 2 {
+		t.Fatalf("want 2 calls (1 stall + 1 retry), got %d", got)
+	}
+}
+
+// A stall AFTER partial output must NOT be retried — re-issuing would duplicate
+// the already-streamed text. It surfaces the error instead.
+func TestRunDoesNotRetryStallAfterPartialOutput(t *testing.T) {
+	p := &stallProvider{stallBefore: 1, partialText: "partial"}
+	_, err := Run(context.Background(), "go", p, Options{Registry: tools.NewRegistry()})
+	if err == nil {
+		t.Fatal("a stall after partial output must NOT be retried; want an error")
+	}
+	if got := atomic.LoadInt32(&p.calls); got != 1 {
+		t.Fatalf("partial-then-stall must not retry, got %d calls", got)
+	}
+}
+
+// A stall after only REASONING was forwarded (no text/tool-calls) must NOT be
+// retried: the user already saw the reasoning, so re-issuing with callbacks
+// re-enabled would duplicate it. collected.Text is empty here, so this exercises
+// the turn-level forwarded-output gate specifically, not the text check.
+func TestRunDoesNotRetryStallAfterForwardedReasoning(t *testing.T) {
+	p := &stallProvider{stallBefore: 1, reasoningText: "thinking hard"}
+	_, err := Run(context.Background(), "go", p, Options{
+		Registry:    tools.NewRegistry(),
+		OnReasoning: func(string) {},
+	})
+	if err == nil {
+		t.Fatal("a stall after forwarded reasoning must NOT be retried; want an error")
+	}
+	if got := atomic.LoadInt32(&p.calls); got != 1 {
+		t.Fatalf("reasoning-then-stall must not retry, got %d calls", got)
+	}
+}
+
+// A persistent stall surfaces an error after exhausting the capped retries.
+func TestRunGivesUpAfterMaxStallRetries(t *testing.T) {
+	p := &stallProvider{stallBefore: 99}
+	_, err := Run(context.Background(), "go", p, Options{Registry: tools.NewRegistry()})
+	if err == nil {
+		t.Fatal("a persistent stall must surface an error after exhausting retries")
+	}
+	if got := atomic.LoadInt32(&p.calls); got != int32(1+maxStreamStallRetries) {
+		t.Fatalf("want %d calls (1 + %d retries), got %d", 1+maxStreamStallRetries, maxStreamStallRetries, got)
+	}
+}
+
+func TestIsStreamTimeoutError(t *testing.T) {
+	timeouts := []string{
+		"provider stream error: no output for 10m (the model produced nothing)",
+		"provider stream error: idle timeout after 5m0s (upstream stopped sending data)",
+		"stream stalled (upstream kept the connection alive but produced no output)",
+	}
+	for _, m := range timeouts {
+		if !isStreamTimeoutError(m) {
+			t.Fatalf("want timeout-classified: %q", m)
+		}
+	}
+	notTimeouts := []string{"", "context length exceeded", "rate limit error: slow down", "model not found"}
+	for _, m := range notTimeouts {
+		if isStreamTimeoutError(m) {
+			t.Fatalf("must NOT classify as timeout: %q", m)
+		}
+	}
+}

internal/config/active_provider_env_test.go

@@ -0,0 +1,49 @@
+package config
+
+import (
+	"os"
+	"testing"
+)
+
+// SetActiveProviderEnv must export the provider name so a child process (whose
+// resolution reads the inherited environment via the nil-map -> os.Getenv path in
+// applyEnv) resolves the SAME active provider. A blank name CLEARS it.
+func TestSetActiveProviderEnvRoundTrips(t *testing.T) {
+	t.Setenv(ActiveProviderEnv, "") // register cleanup; restores the original after
+
+	if err := os.Unsetenv(ActiveProviderEnv); err != nil {
+		t.Fatalf("unset: %v", err)
+	}
+	SetActiveProviderEnv("") // blank with nothing set stays unset
+	if got := os.Getenv(ActiveProviderEnv); got != "" {
+		t.Fatalf("empty name set the env to %q, want unset", got)
+	}
+
+	// Regression: switching from a named provider back to an unnamed/default profile
+	// must CLEAR a previously exported value, not leave it stale for children.
+	if err := os.Setenv(ActiveProviderEnv, "stale-provider"); err != nil {
+		t.Fatalf("seed stale: %v", err)
+	}
+	SetActiveProviderEnv("") // blank must unset the stale value
+	if got := os.Getenv(ActiveProviderEnv); got != "" {
+		t.Fatalf("blank name left stale env %q, want cleared", got)
+	}
+	cfgStale := &FileConfig{}
+	applyEnv(cfgStale, nil)
+	if cfgStale.ActiveProvider != "" {
+		t.Fatalf("applyEnv still resolved stale provider %q after clear", cfgStale.ActiveProvider)
+	}
+
+	SetActiveProviderEnv("ollama-cloud")
+	if got := os.Getenv(ActiveProviderEnv); got != "ollama-cloud" {
+		t.Fatalf("env = %q, want ollama-cloud", got)
+	}
+
+	// applyEnv with a nil map is the exact path a child uses: it falls back to
+	// os.Getenv, so the inherited value selects the active provider.
+	cfg := &FileConfig{}
+	applyEnv(cfg, nil)
+	if cfg.ActiveProvider != "ollama-cloud" {
+		t.Fatalf("applyEnv ActiveProvider = %q, want ollama-cloud (inherited env not read)", cfg.ActiveProvider)
+	}
+}

internal/config/max_turns_env_test.go

@@ -0,0 +1,56 @@
+package config
+
+import (
+	"os"
+	"testing"
+)
+
+// SetMaxTurnsEnv must export the per-run turn budget so a child process (whose
+// resolution reads the inherited environment via the nil-map -> os.Getenv path in
+// applyEnv) runs with the SAME budget the user set via /turns. n <= 0 is a no-op,
+// and a non-numeric/zero env value must not clobber the configured budget.
+func TestSetMaxTurnsEnvRoundTrips(t *testing.T) {
+	t.Setenv(MaxTurnsEnv, "") // register cleanup; restores the original after
+
+	if err := os.Unsetenv(MaxTurnsEnv); err != nil {
+		t.Fatalf("unset: %v", err)
+	}
+	SetMaxTurnsEnv(0) // non-positive must not set anything
+	if got := os.Getenv(MaxTurnsEnv); got != "" {
+		t.Fatalf("n<=0 set the env to %q, want unset", got)
+	}
+
+	SetMaxTurnsEnv(150)
+	if got := os.Getenv(MaxTurnsEnv); got != "150" {
+		t.Fatalf("env = %q, want 150", got)
+	}
+
+	// applyEnv with a nil map is the exact path a child uses: it falls back to
+	// os.Getenv, so the inherited value sets the budget.
+	cfg := &FileConfig{MaxTurns: defaultMaxTurns}
+	applyEnv(cfg, nil)
+	if cfg.MaxTurns != 150 {
+		t.Fatalf("applyEnv MaxTurns = %d, want 150 (inherited env not read)", cfg.MaxTurns)
+	}
+
+	// A garbage env value must leave the configured budget untouched.
+	if err := os.Setenv(MaxTurnsEnv, "not-a-number"); err != nil {
+		t.Fatalf("set: %v", err)
+	}
+	cfg2 := &FileConfig{MaxTurns: defaultMaxTurns}
+	applyEnv(cfg2, nil)
+	if cfg2.MaxTurns != defaultMaxTurns {
+		t.Fatalf("garbage env clobbered MaxTurns to %d, want default %d", cfg2.MaxTurns, defaultMaxTurns)
+	}
+
+	// An over-ceiling env value (e.g. a raw shell export that bypasses the /turns
+	// clamp) must be clamped to MaxTurnsCeiling at the read site.
+	if err := os.Setenv(MaxTurnsEnv, "999999"); err != nil {
+		t.Fatalf("set: %v", err)
+	}
+	cfg3 := &FileConfig{MaxTurns: defaultMaxTurns}
+	applyEnv(cfg3, nil)
+	if cfg3.MaxTurns != MaxTurnsCeiling {
+		t.Fatalf("applyEnv MaxTurns = %d, want clamped to ceiling %d", cfg3.MaxTurns, MaxTurnsCeiling)
+	}
+}

internal/config/resolver.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"net/url"
 	"os"
+	"strconv"
 	"strings"
 
 	"github.com/Gitlawb/zero/internal/modelregistry"
@@ -13,7 +14,15 @@ import (
 	"github.com/Gitlawb/zero/internal/sandbox"
 )
 
-const defaultMaxTurns = 30
+// defaultMaxTurns is the per-run tool-turn budget when none is configured. 30 was
+// too low for real multi-step agentic work (agents ran out mid-task before reaching
+// later steps); 50 matches the old "deep" preset. Raise per-session with /turns.
+const defaultMaxTurns = 50
+
+// MaxTurnsCeiling caps the per-run tool-turn budget so a stray env value or typo
+// can't set an absurd ceiling. Shared between applyEnv (read site) and the /turns
+// command (write site) so the bound holds even if the env is set by a raw shell.
+const MaxTurnsCeiling = 500
 
 // defaultDeferThreshold is the number of deferred-eligible (MCP) tools at which
 // Zero collapses their full JSON schemas into compact `tool_search` reminder
@@ -431,11 +440,53 @@ func mergeProfile(base ProviderProfile, next ProviderProfile) ProviderProfile {
 	return base
 }
 
+// ActiveProviderEnv selects the active provider profile by name (read in applyEnv).
+const ActiveProviderEnv = "ZERO_PROVIDER"
+
+// SetActiveProviderEnv exports the active provider name to the process environment
+// so a spawned child process (which inherits the environment) resolves the SAME
+// provider profile — and therefore the same credentials (env key / stored key /
+// OAuth) — as its parent. Without this a sub-agent re-resolves config.json's
+// default provider and can land on one whose credentials don't match the parent's
+// live selection, failing auth the instant it spawns. A blank name CLEARS the
+// variable: switching back to an unnamed/default profile must not keep exporting a
+// stale provider to children.
+func SetActiveProviderEnv(name string) {
+	name = strings.TrimSpace(name)
+	if name == "" {
+		_ = os.Unsetenv(ActiveProviderEnv)
+		return
+	}
+	_ = os.Setenv(ActiveProviderEnv, name)
+}
+
+// MaxTurnsEnv overrides the per-run tool-turn budget by name (read in applyEnv).
+const MaxTurnsEnv = "ZERO_MAX_TURNS"
+
+// SetMaxTurnsEnv exports the per-run tool-turn budget to the process environment so
+// a spawned child (sub-agent / swarm member, which inherits the environment) runs
+// with the SAME budget the user set via /turns. Without it a child re-resolves
+// config.json's default and a large delegated task can exhaust its turns mid-run
+// (exit 4 / max-turns). No-op for n <= 0.
+func SetMaxTurnsEnv(n int) {
+	if n > 0 {
+		_ = os.Setenv(MaxTurnsEnv, strconv.Itoa(n))
+	}
+}
+
 func applyEnv(cfg *FileConfig, env map[string]string) {
-	activeProvider := strings.TrimSpace(envValue(env, "ZERO_PROVIDER"))
+	activeProvider := strings.TrimSpace(envValue(env, ActiveProviderEnv))
 	if activeProvider != "" {
 		cfg.ActiveProvider = activeProvider
 	}
+	if maxTurns := strings.TrimSpace(envValue(env, MaxTurnsEnv)); maxTurns != "" {
+		if n, err := strconv.Atoi(maxTurns); err == nil && n > 0 {
+			if n > MaxTurnsCeiling {
+				n = MaxTurnsCeiling
+			}
+			cfg.MaxTurns = n
+		}
+	}
 
 	applyProviderEnv(cfg, ProviderKindOpenAI, envProfile{
 		Name:    string(ProviderKindOpenAI),

internal/config/resolver_test.go

@@ -883,8 +883,8 @@ func TestResolveAllowsNoConfiguredProviders(t *testing.T) {
 	if HasProviderProfile(resolved.Provider) {
 		t.Fatalf("Provider = %#v, want zero value", resolved.Provider)
 	}
-	if resolved.MaxTurns != 30 {
-		t.Fatalf("MaxTurns = %d, want 30", resolved.MaxTurns)
+	if resolved.MaxTurns != defaultMaxTurns {
+		t.Fatalf("MaxTurns = %d, want default %d", resolved.MaxTurns, defaultMaxTurns)
 	}
 }
 

internal/providers/anthropic/provider.go

@@ -211,11 +211,11 @@ func (provider *Provider) stream(ctx context.Context, body []byte, events chan<-
 	err = providerio.ScanSSEDataWithContext(streamCtx, cancelStream, response.Body, provider.streamIdleTimeout, func(data string) bool {
 		return provider.emitPayload(ctx, data, state, events)
 	})
-	if errors.Is(err, providerio.ErrStreamIdle) {
+	if errors.Is(err, providerio.ErrStreamIdle) || errors.Is(err, providerio.ErrStreamStalled) {
 		state.closeOpen(ctx, events)
 		providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
 			Type:  zeroruntime.StreamEventError,
-			Error: provider.redact(fmt.Sprintf("provider stream error: idle timeout after %s (upstream stopped sending data)", provider.streamIdleTimeout)),
+			Error: provider.redact("provider stream error: " + providerio.StreamTimeoutMessage(err, provider.streamIdleTimeout)),
 		})
 		return
 	}

internal/providers/factory_test.go

@@ -264,6 +264,13 @@ func TestNewRejectsUnsupportedProviderKind(t *testing.T) {
 }
 
 func TestNewRoutesChatGPTCatalogToCodexProvider(t *testing.T) {
+	// Isolate the OAuth token store to an empty temp path so the factory reads no
+	// stored login — otherwise this test picks up the developer's real chatgpt
+	// OAuth token and the "want empty chatgpt-account-id" assertion fails locally
+	// (it still passes in CI, where no login is stored). Mirrors the isolation in
+	// TestNewRoutesChatGPTCatalogWithStoredAccountID.
+	t.Setenv("ZERO_OAUTH_TOKENS_PATH", t.TempDir()+"/tokens.json")
+
 	transport := &captureTransport{
 		responseBody: "data: [DONE]\n\n",
 	}

internal/providers/gemini/provider.go

@@ -158,10 +158,10 @@ func (provider *Provider) stream(ctx context.Context, body []byte, events chan<-
 	err = providerio.ScanSSEDataWithContext(streamCtx, cancelStream, response.Body, provider.streamIdleTimeout, func(data string) bool {
 		return provider.emitPayload(ctx, data, &state, events)
 	})
-	if errors.Is(err, providerio.ErrStreamIdle) {
+	if errors.Is(err, providerio.ErrStreamIdle) || errors.Is(err, providerio.ErrStreamStalled) {
 		providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
 			Type:  zeroruntime.StreamEventError,
-			Error: provider.redact(fmt.Sprintf("provider stream error: idle timeout after %s (upstream stopped sending data)", provider.streamIdleTimeout)),
+			Error: provider.redact("provider stream error: " + providerio.StreamTimeoutMessage(err, provider.streamIdleTimeout)),
 		})
 		return
 	}

internal/providers/openai/codex_responses.go

@@ -59,6 +59,7 @@ const (
 	responsesEventOutputItemAdded   = "response.output_item.added"
 	responsesEventContentPartAdded  = "response.content_part.added"
 	responsesEventOutputTextDelta   = "response.output_text.delta"
+	responsesEventReasoningDelta    = "response.reasoning_summary_text.delta"
 	responsesEventOutputTextDone    = "response.output_text.done"
 	responsesEventFunctionArgsDelta = "response.function_call_arguments.delta"
 	responsesEventContentPartDone   = "response.content_part.done"
@@ -86,6 +87,10 @@ type responsesRequest struct {
 // here; omitted entirely when the caller requests no (or an unsupported) effort.
 type responsesReasoning struct {
 	Effort string `json:"effort,omitempty"`
+	// Summary requests a streamed reasoning summary ("auto" lets the API pick a
+	// level). Without it the backend emits no reasoning events, so a long thinking
+	// phase produces zero visible output and reads as a hang in the UI.
+	Summary string `json:"summary,omitempty"`
 }
 
 // inputItem is one element of the Responses `input` array. The Type field
@@ -256,7 +261,9 @@ func (p *CodexProvider) buildResponsesRequest(request zeroruntime.CompletionRequ
 	// and an empty or unsupported effort simply omits the field — without this the
 	// caller's chosen effort was silently dropped for every Codex model.
 	if effort := openAIReasoningEffort(request.ReasoningEffort); effort != "" {
-		req.Reasoning = &responsesReasoning{Effort: effort}
+		// Summary "auto" makes the backend stream reasoning_summary_text deltas so a
+		// long thinking phase shows live progress instead of looking hung.
+		req.Reasoning = &responsesReasoning{Effort: effort, Summary: "auto"}
 	}
 	return req, nil
 }
@@ -382,10 +389,10 @@ func (p *CodexProvider) streamResponses(
 	err = providerio.ScanSSEDataWithContext(streamCtx, cancelStream, response.Body, inner.streamIdleTimeout, func(data string) bool {
 		return p.emitResponsesEvent(ctx, data, state, events)
 	})
-	if errors.Is(err, providerio.ErrStreamIdle) {
+	if errors.Is(err, providerio.ErrStreamIdle) || errors.Is(err, providerio.ErrStreamStalled) {
 		providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
 			Type:  zeroruntime.StreamEventError,
-			Error: p.redact(fmt.Sprintf("provider stream error: idle timeout after %s (upstream stopped sending data)", inner.streamIdleTimeout)),
+			Error: p.redact("provider stream error: " + providerio.StreamTimeoutMessage(err, inner.streamIdleTimeout)),
 		})
 		return
 	}
@@ -501,6 +508,17 @@ func (p *CodexProvider) emitResponsesEvent(
 			})
 		}
 		return true
+	case responsesEventReasoningDelta:
+		// Reasoning summary deltas: surface as live "thinking" so a long reasoning
+		// phase shows progress (and keeps the activity clock fresh) instead of
+		// looking like a hang. Requested via reasoning.summary="auto".
+		if event.Delta != "" {
+			providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
+				Type:    zeroruntime.StreamEventReasoning,
+				Content: event.Delta,
+			})
+		}
+		return true
 	case responsesEventFunctionArgsDelta:
 		p.handleFunctionArgsDelta(ctx, &event, state, events)
 		return true

internal/providers/openai/codex_test.go

@@ -485,6 +485,58 @@ func TestCodexProviderForwardsReasoningEffort(t *testing.T) {
 	if reasoning["effort"] != "high" {
 		t.Fatalf("body.reasoning.effort = %#v, want high", reasoning["effort"])
 	}
+	// A reasoning summary must be requested so the backend streams
+	// reasoning_summary_text deltas — otherwise a long think shows no live output.
+	if reasoning["summary"] != "auto" {
+		t.Fatalf("body.reasoning.summary = %#v, want auto", reasoning["summary"])
+	}
+}
+
+func TestCodexProviderStreamsReasoningSummaryDeltas(t *testing.T) {
+	// reasoning_summary_text deltas must surface as StreamEventReasoning (live
+	// "thinking"), in order, alongside the normal text output. Without this a long
+	// reasoning phase produces zero visible output and reads as a hang.
+	var rec codexRequest
+	srv := newCodexResponsesServer(t, &rec,
+		`{"type":"response.created","response":{"id":"resp-1","status":"in_progress"}}`,
+		`{"type":"response.reasoning_summary_text.delta","delta":"Thinking. "}`,
+		`{"type":"response.reasoning_summary_text.delta","delta":"Planning."}`,
+		`{"type":"response.output_text.delta","delta":"done"}`,
+		`{"type":"response.completed","response":{"id":"resp-1","status":"completed"}}`,
+	)
+	defer srv.Close()
+
+	provider, err := NewCodexProvider(CodexOptions{
+		Options:   Options{APIKey: "sk-test", BaseURL: srv.URL, Model: "gpt-5"},
+		AccountID: "acc-x",
+	})
+	if err != nil {
+		t.Fatalf("NewCodexProvider: %v", err)
+	}
+	stream, err := provider.StreamCompletion(context.Background(), zeroruntime.CompletionRequest{
+		Messages:        []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "solve it"}},
+		ReasoningEffort: "high",
+	})
+	if err != nil {
+		t.Fatalf("StreamCompletion: %v", err)
+	}
+	var reasoning, text []string
+	for ev := range stream {
+		switch ev.Type {
+		case zeroruntime.StreamEventReasoning:
+			reasoning = append(reasoning, ev.Content)
+		case zeroruntime.StreamEventText:
+			text = append(text, ev.Content)
+		case zeroruntime.StreamEventError:
+			t.Fatalf("unexpected error event: %q", ev.Error)
+		}
+	}
+	if got := strings.Join(reasoning, ""); got != "Thinking. Planning." {
+		t.Fatalf("reasoning deltas = %q, want %q", got, "Thinking. Planning.")
+	}
+	if got := strings.Join(text, ""); got != "done" {
+		t.Fatalf("text deltas = %q, want %q", got, "done")
+	}
 }
 
 func TestCodexProviderOmitsReasoningWhenUnset(t *testing.T) {

internal/providers/openai/provider.go

@@ -102,10 +102,11 @@ func New(options Options) (*Provider, error) {
 		endpoint = baseURL + "/chat/completions"
 	}
 
-	httpClient := options.HTTPClient
-	if httpClient == nil {
-		httpClient = http.DefaultClient
-	}
+	// Route through providerio.HTTPClient so a missing client gets the shared,
+	// stall-hardened transport (bounded response-header wait + shorter idle-conn
+	// reuse) rather than the raw http.DefaultClient, which hangs on a reused-dead
+	// pooled connection (the macOS-only "both providers stall" bug).
+	httpClient := providerio.HTTPClient(options.HTTPClient)
 
 	maxTokens := options.MaxTokens
 	if maxTokens < 0 {
@@ -218,12 +219,12 @@ func (provider *Provider) stream(ctx context.Context, body []byte, events chan<-
 	err = providerio.ScanSSEDataWithContext(streamCtx, cancelStream, response.Body, provider.streamIdleTimeout, func(data string) bool {
 		return provider.emitPayload(ctx, data, state, events)
 	})
-	if errors.Is(err, providerio.ErrStreamIdle) {
+	if errors.Is(err, providerio.ErrStreamIdle) || errors.Is(err, providerio.ErrStreamStalled) {
 		state.flushBufferedContent(events)
 		state.closeBufferedOpen(events)
 		sendEvent(ctx, events, zeroruntime.StreamEvent{
 			Type:  zeroruntime.StreamEventError,
-			Error: provider.redact(fmt.Sprintf("provider stream error: idle timeout after %s (upstream stopped sending data)", provider.streamIdleTimeout)),
+			Error: provider.redact("provider stream error: " + providerio.StreamTimeoutMessage(err, provider.streamIdleTimeout)),
 		})
 		return
 	}

internal/providers/providerio/providerio.go

@@ -23,6 +23,26 @@ const maxSSELineBytes = 16 * 1024 * 1024
 // closing the connection. Callers surface it as an idle-timeout error.
 var ErrStreamIdle = errors.New("idle timeout (upstream stopped sending data)")
 
+// ErrStreamStalled reports that a streaming upstream kept the connection alive
+// (SSE keep-alives reset the idle watchdog, so it never fired) but produced no
+// actual output for streamContentStallFactor × the idle timeout. Without this an
+// upstream that heartbeats-but-stalls — observed on chatgpt/gpt-5.x and ollama
+// reasoning models — would hang the agent indefinitely.
+var ErrStreamStalled = errors.New("stream stalled (upstream kept the connection alive but produced no output)")
+
+// StreamTimeoutMessage returns the human-readable detail for a stream-timeout
+// error (ErrStreamIdle or ErrStreamStalled), given the configured idle timeout.
+// Callers prepend their own "provider stream error: " prefix. A stalled stream
+// gets a distinct, actionable message — it did NOT stop sending data (keep-alives
+// kept arriving); it just produced no output, which usually means the model is
+// stuck or very slow.
+func StreamTimeoutMessage(err error, idleTimeout time.Duration) string {
+	if errors.Is(err, ErrStreamStalled) {
+		return fmt.Sprintf("no output for %s (the model kept the connection alive but produced nothing — it may be stuck; try a faster model or lower reasoning effort)", idleTimeout*streamContentStallFactor)
+	}
+	return fmt.Sprintf("idle timeout after %s (upstream stopped sending data)", idleTimeout)
+}
+
 // DefaultStreamIdleTimeout is the single source of truth for how long every
 // provider waits on a silent stream before aborting it. The watchdog only fires
 // on genuine silence — SSE keep-alive comments reset it (see
@@ -33,6 +53,14 @@ var ErrStreamIdle = errors.New("idle timeout (upstream stopped sending data)")
 // Override globally with ZERO_STREAM_IDLE_TIMEOUT.
 const DefaultStreamIdleTimeout = 5 * time.Minute
 
+// streamContentStallFactor bounds a heartbeat-but-no-output stream. Keep-alives
+// reset the idle watchdog (a heartbeating upstream is not "dead"), but if NO real
+// data line arrives for streamContentStallFactor × the idle timeout, the stream is
+// treated as stalled and aborted (ErrStreamStalled). It is > 1 so a slow-but-
+// producing request — one that emits data between heartbeats — is never killed; the
+// content watchdog only catches a stream that heartbeats while producing nothing.
+const streamContentStallFactor = 2
+
 // streamIdleTimeoutEnv is the global override for the stream idle timeout. It
 // accepts a Go duration ("5m", "300s", "90s") or a bare number of seconds
 // ("300"). A value of "0", "off", "none", or "disabled" turns the watchdog off
@@ -77,12 +105,42 @@ func NormalizeBaseURL(baseURL string, defaultBaseURL string, label string) (stri
 	return baseURL, nil
 }
 
-// HTTPClient returns the configured client or the process default.
+// sharedHTTPClient is the process-wide client used when a provider supplies none.
+// It tunes the default transport to defeat the stale-pooled-connection hang: Go
+// keeps idle keep-alive connections in a pool, and a later request can reuse one
+// the server/NAT has silently dropped. Because the model call is a POST (non-
+// idempotent), Go will NOT auto-retry it on a fresh connection — so it blocks
+// forever waiting for a response that never arrives. This is provider-agnostic
+// (every provider shares the default transport), which is why it reproduced on
+// BOTH chatgpt and ollama, and it surfaces on macOS far more than Linux because
+// macOS keeps dead pooled connections around longer.
+//
+//   - ResponseHeaderTimeout bounds the gap between finishing the request and the
+//     first response header, so a reused-dead connection fails fast (then the
+//     reconnect path re-dials) instead of hanging. It does NOT bound streaming
+//     after the 200 header arrives, so slow first tokens / long reasoning are
+//     unaffected (the stream-idle + content watchdogs cover that).
+//   - IdleConnTimeout is shortened so a connection that went idle across a pause
+//     is closed (and re-dialed fresh) rather than reused after it has gone stale.
+var sharedHTTPClient = func() *http.Client {
+	transport := http.DefaultTransport.(*http.Transport).Clone()
+	// 120s, not 60s: a slow cloud proxy (e.g. ollama `*:cloud`) can withhold its
+	// 200 response header until the upstream model emits a first token, so a 60s cap
+	// risked aborting a legitimately-slow-but-alive request. 120s still bounds a
+	// truly dead reused connection (which never responds) while tolerating slow
+	// header delivery; slow first tokens after the header are covered by the idle +
+	// content-stall watchdogs.
+	transport.ResponseHeaderTimeout = 120 * time.Second
+	transport.IdleConnTimeout = 30 * time.Second
+	return &http.Client{Transport: transport}
+}()
+
+// HTTPClient returns the configured client or the shared, stall-hardened default.
 func HTTPClient(client *http.Client) *http.Client {
 	if client != nil {
 		return client
 	}
-	return http.DefaultClient
+	return sharedHTTPClient
 }
 
 // SendEvent writes a provider event without blocking cancellation cleanup.
@@ -202,21 +260,36 @@ func ScanSSEDataWithContext(
 	// The idle watchdog is optional. When idleTimeout <= 0 it is disabled, but we
 	// STILL run the goroutine + select loop so ctx cancellation is always honored
 	// (a nil idleC channel simply never fires in the select).
-	var idleC <-chan time.Time
+	var idleC, contentC <-chan time.Time
 	resetIdle := func() {}
+	resetContent := func() {}
 	if idleTimeout > 0 {
+		// reset drains the timer's channel if it already fired before re-arming, so
+		// a stale tick can't trip the watchdog after activity resumed.
+		reset := func(t *time.Timer, d time.Duration) func() {
+			return func() {
+				if !t.Stop() {
+					select {
+					case <-t.C:
+					default:
+					}
+				}
+				t.Reset(d)
+			}
+		}
 		idle := time.NewTimer(idleTimeout)
 		defer idle.Stop()
 		idleC = idle.C
-		resetIdle = func() {
-			if !idle.Stop() {
-				select {
-				case <-idle.C:
-				default:
-				}
-			}
-			idle.Reset(idleTimeout)
-		}
+		resetIdle = reset(idle, idleTimeout)
+
+		// Content watchdog: only real data lines reset it (keep-alives do not), so a
+		// stream that heartbeats without producing output is bounded instead of
+		// hanging forever.
+		contentTimeout := idleTimeout * streamContentStallFactor
+		content := time.NewTimer(contentTimeout)
+		defer content.Stop()
+		contentC = content.C
+		resetContent = reset(content, contentTimeout)
 	}
 
 	for {
@@ -232,6 +305,12 @@ func ScanSSEDataWithContext(
 			// a timeout instead of blocking the agent forever.
 			cancel()
 			return ErrStreamIdle
+		case <-contentC:
+			// Upstream kept heartbeating (idle watchdog never fired) but produced
+			// no output for the content window. Treat as stalled and abort rather
+			// than hanging forever.
+			cancel()
+			return ErrStreamStalled
 		case item, ok := <-payloads:
 			if !ok {
 				// Reader finished: deliver its terminal status (EOF -> nil,
@@ -246,8 +325,11 @@ func ScanSSEDataWithContext(
 			}
 			resetIdle()
 			if item.keepAlive {
+				// A heartbeat keeps the connection "alive" (idle watchdog) but is
+				// NOT output, so it must not reset the content watchdog.
 				continue
 			}
+			resetContent()
 			if !handle(item.data) {
 				// The provider asked to stop (e.g. it already emitted an error
 				// for this payload). Abort the read and end like ScanSSEData:

internal/providers/providerio/providerio_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"io"
+	"net/http"
 	"strings"
 	"testing"
 	"time"
@@ -201,3 +202,133 @@ func TestUpstreamUnreachable(t *testing.T) {
 		})
 	}
 }
+
+// A heartbeating-but-output-less upstream must not hang forever: SSE keep-alives
+// feed the idle watchdog (so it never fires), but the content watchdog
+// (idleTimeout × streamContentStallFactor) aborts with ErrStreamStalled when no
+// real data line arrives. This is the gpt-5.x / ollama "still generating forever"
+// hang.
+func TestScanSSEDataWithContextAbortsOnContentStall(t *testing.T) {
+	pr, pw := io.Pipe()
+	defer func() { _ = pw.Close() }()
+
+	stop := make(chan struct{})
+	defer close(stop)
+	go func() {
+		// Heartbeat every 30ms — comfortably under the 100ms idle timeout, so idle
+		// never fires under CI/GC jitter — but never send a data line.
+		for {
+			select {
+			case <-stop:
+				return
+			default:
+			}
+			if _, err := io.WriteString(pw, ": keep-alive\n\n"); err != nil {
+				return
+			}
+			time.Sleep(30 * time.Millisecond)
+		}
+	}()
+
+	cancelled := false
+	cancel := func() { cancelled = true }
+
+	done := make(chan error, 1)
+	go func() {
+		// idle 100ms → content stall at 200ms. Keep-alives reset idle but not content.
+		done <- ScanSSEDataWithContext(context.Background(), cancel, pr, 100*time.Millisecond, func(string) bool { return true })
+	}()
+
+	select {
+	case err := <-done:
+		if !errors.Is(err, ErrStreamStalled) {
+			t.Fatalf("err = %v, want ErrStreamStalled", err)
+		}
+	case <-time.After(3 * time.Second):
+		t.Fatal("ScanSSEDataWithContext hung on a heartbeat-but-no-output stream")
+	}
+	if !cancelled {
+		t.Fatal("content stall did not cancel the request context")
+	}
+}
+
+// Real data lines reset the content watchdog, so a slow-but-producing stream that
+// runs longer than the content window is never aborted.
+func TestScanSSEDataWithContextContentResetsOnData(t *testing.T) {
+	pr, pw := io.Pipe()
+
+	go func() {
+		// One data line every 30ms for ~300ms (well past the 200ms content window,
+		// with comfortable slack under the 100ms idle timeout), so the content
+		// watchdog keeps resetting, then close cleanly.
+		for i := 0; i < 10; i++ {
+			if _, err := io.WriteString(pw, "data: chunk\n\n"); err != nil {
+				return
+			}
+			time.Sleep(30 * time.Millisecond)
+		}
+		_ = pw.Close()
+	}()
+
+	n := 0
+	done := make(chan error, 1)
+	go func() {
+		done <- ScanSSEDataWithContext(context.Background(), func() {}, pr, 100*time.Millisecond, func(string) bool { n++; return true })
+	}()
+
+	select {
+	case err := <-done:
+		if err != nil {
+			t.Fatalf("err = %v, want nil (data kept the stream alive)", err)
+		}
+	case <-time.After(3 * time.Second):
+		t.Fatal("ScanSSEDataWithContext hung on a producing stream")
+	}
+	if n != 10 {
+		t.Fatalf("handled %d data lines, want 10", n)
+	}
+}
+
+// StreamTimeoutMessage must give a stalled stream a distinct, accurate detail —
+// it reports the content window (idle × factor) and must NOT claim the upstream
+// "stopped sending data" (keep-alives were still arriving).
+func TestStreamTimeoutMessage(t *testing.T) {
+	idle := 5 * time.Minute
+	if msg := StreamTimeoutMessage(ErrStreamIdle, idle); !strings.Contains(msg, "idle timeout after 5m") {
+		t.Fatalf("idle message = %q, want it to mention the 5m idle timeout", msg)
+	}
+	stalled := StreamTimeoutMessage(ErrStreamStalled, idle)
+	if !strings.Contains(stalled, "no output for 10m") {
+		t.Fatalf("stalled message = %q, want it to report the 10m content window", stalled)
+	}
+	if strings.Contains(stalled, "stopped sending data") {
+		t.Fatalf("stalled message must not claim the upstream stopped sending data: %q", stalled)
+	}
+}
+
+// HTTPClient(nil) must return the shared, stall-hardened transport (bounded
+// response-header wait + shorter idle-conn reuse) that defeats the macOS stale-
+// pooled-connection hang; an explicit client is returned untouched.
+func TestHTTPClientReturnsStallHardenedSharedClient(t *testing.T) {
+	got := HTTPClient(nil)
+	if got == nil {
+		t.Fatal("HTTPClient(nil) returned nil")
+	}
+	tr, ok := got.Transport.(*http.Transport)
+	if !ok {
+		t.Fatalf("transport type = %T, want *http.Transport", got.Transport)
+	}
+	if tr.ResponseHeaderTimeout != 120*time.Second {
+		t.Fatalf("ResponseHeaderTimeout = %v, want 120s", tr.ResponseHeaderTimeout)
+	}
+	if tr.IdleConnTimeout != 30*time.Second {
+		t.Fatalf("IdleConnTimeout = %v, want 30s", tr.IdleConnTimeout)
+	}
+	if HTTPClient(nil) != got {
+		t.Fatal("HTTPClient(nil) must return a shared instance so the conn pool is reused")
+	}
+	custom := &http.Client{}
+	if HTTPClient(custom) != custom {
+		t.Fatal("an explicit client must be returned unchanged")
+	}
+}

internal/specialist/exec.go

@@ -204,7 +204,11 @@ type ChildRunResult struct {
 	Events   []streamjson.Event
 	Stderr   string
 	ExitCode int
-	Started  bool
+	// Signal is a human-readable description (e.g. "signal: killed") when the child
+	// was terminated by a signal rather than exiting normally; empty otherwise. It
+	// turns an opaque exit -1 into an actionable reason (SIGKILL ~ out of memory).
+	Signal  string
+	Started bool
 }
 
 func (executor Executor) Run(ctx context.Context, params TaskParameters, options TaskRunOptions) (ExecResult, error) {
@@ -566,17 +570,35 @@ func (executor Executor) runBuiltArgs(ctx context.Context, built BuildArgsResult
 		exitCode := run.exitCodeOr(-1)
 		summary := SummarizeStream(run.Events, exitCode)
 		executor.recordSpecialistStop(accounting, summary, "error", summary.ExitCode, err, false)
-		return ExecResult{}, err
+		// Carry the child session id even on a post-start failure so a caller (the
+		// swarm launcher -> FailWithSession) can still make the failed member
+		// drillable; the session exists once the child has started.
+		return ExecResult{SessionID: built.SessionID}, err
 	}
 	summary := SummarizeStream(run.Events, run.ExitCode)
 	rolledUp := executor.rollUpSpecialistUsage(accounting, summary)
 	executor.recordSpecialistStop(accounting, summary, summary.Status, summary.ExitCode, nil, rolledUp)
 	return ExecResult{
-		Result:    BuildFinalResult(run.Events, run.Stderr, run.ExitCode),
+		Result:    BuildFinalResult(run.Events, run.Stderr, run.ExitCode, run.Signal),
 		SessionID: built.SessionID,
 	}, nil
 }
 
+// availableSpecialistList renders the registered specialist names for a corrective
+// "not found" error, so a model that guessed a wrong name learns the real options.
+func availableSpecialistList(result LoadResult) string {
+	names := make([]string, 0, len(result.Specialists))
+	for _, manifest := range result.Specialists {
+		if n := strings.TrimSpace(manifest.Metadata.Name); n != "" {
+			names = append(names, n)
+		}
+	}
+	if len(names) == 0 {
+		return "(none registered)"
+	}
+	return strings.Join(names, ", ")
+}
+
 func (executor Executor) loadManifest(name string) (Manifest, error) {
 	name = strings.TrimSpace(name)
 	if name == "" {
@@ -592,7 +614,12 @@ func (executor Executor) loadManifest(name string) (Manifest, error) {
 	}
 	manifest, ok := Find(result, name)
 	if !ok {
-		return Manifest{}, fmt.Errorf("specialist %q not found", name)
+		// Corrective error: a model that invents a specialist name (e.g.
+		// "validator-runner", "file-writer") otherwise gets an opaque "not found"
+		// and keeps retrying made-up names. List the ACTUALLY-registered ones so it
+		// self-corrects — no hardcoded names, since a custom registry may not have
+		// worker/explorer/code-review.
+		return Manifest{}, fmt.Errorf("specialist %q not found. Available: %s. Pick one of these whose tools fit the task, or omit the name to use the default", name, availableSpecialistList(result))
 	}
 	return manifest, nil
 }
@@ -783,15 +810,22 @@ func runChildProcess(ctx context.Context, binaryPath string, args []string, prog
 	}
 	exitCode := 0
 	started := true
+	signalDesc := ""
 	if err := command.Wait(); err != nil {
 		var exitErr *osexec.ExitError
 		if errors.As(err, &exitErr) {
 			exitCode = exitErr.ExitCode()
+			if exitCode < 0 && exitErr.ProcessState != nil {
+				// ExitCode() is -1 when the child was terminated by a signal rather
+				// than exiting. ProcessState.String() is the portable description
+				// (e.g. "signal: killed") — capture it so the failure isn't opaque.
+				signalDesc = exitErr.ProcessState.String()
+			}
 		} else {
 			return ChildRunResult{Events: events, Stderr: stderr.String(), ExitCode: -1, Started: started}, fmt.Errorf("run specialist child: %w", err)
 		}
 	}
-	return ChildRunResult{Events: events, Stderr: stderr.String(), ExitCode: exitCode, Started: started}, nil
+	return ChildRunResult{Events: events, Stderr: stderr.String(), ExitCode: exitCode, Signal: signalDesc, Started: started}, nil
 }
 
 func (run ChildRunResult) exitCodeOr(defaultExitCode int) int {

internal/specialist/load_manifest_error_test.go

@@ -0,0 +1,32 @@
+package specialist
+
+import (
+	"strings"
+	"testing"
+)
+
+// A model that invents a specialist name (e.g. "validator-runner", "file-writer")
+// must get a corrective error listing the real specialists, so it self-corrects to a
+// capable one instead of looping on made-up names that spawn doomed sub-agents.
+func TestLoadManifestUnknownNameListsAvailable(t *testing.T) {
+	executor := Executor{
+		Load: func(LoadOptions) (LoadResult, error) {
+			return LoadResult{Specialists: []Manifest{
+				{Metadata: Metadata{Name: "worker"}},
+				{Metadata: Metadata{Name: "explorer"}},
+				{Metadata: Metadata{Name: "code-review"}},
+			}}, nil
+		},
+	}
+
+	_, err := executor.loadManifest("validator-runner")
+	if err == nil {
+		t.Fatal("an unknown specialist name must error")
+	}
+	msg := err.Error()
+	for _, want := range []string{"validator-runner", "not found", "worker", "explorer", "code-review"} {
+		if !strings.Contains(msg, want) {
+			t.Fatalf("error %q missing %q (must steer the model to a real specialist)", msg, want)
+		}
+	}
+}

internal/specialist/output_tool.go

@@ -260,6 +260,12 @@ func formatTaskOutputSummary(task background.Task, summary StreamResult, rawLine
 	if !task.CompletedAt.IsZero() {
 		fmt.Fprintf(&builder, "completed_at: %s\n", task.CompletedAt.Format(time.RFC3339))
 		fmt.Fprintf(&builder, "exit_code: %d\n", task.ExitCode)
+		if task.ExitCode < 0 {
+			// A negative exit code means the background child was terminated by a
+			// signal rather than exiting (the int-only launcher can't carry the
+			// signal name). Give the same actionable hint the foreground path does.
+			builder.WriteString("note: terminated by a signal — killed before it finished. Likely causes: the OS out-of-memory killer (common when many sub-agents run in parallel — try fewer), a timeout, or cancellation.\n")
+		}
 	}
 
 	if summary.Text != "" {

internal/specialist/streamer.go

@@ -134,12 +134,17 @@ func SummarizeStream(events []streamjson.Event, processExitCode int) StreamResul
 	return result
 }
 
-func BuildFinalResult(events []streamjson.Event, stderrOutput string, processExitCode int) tools.Result {
+func BuildFinalResult(events []streamjson.Event, stderrOutput string, processExitCode int, signalDesc string) tools.Result {
 	summary := SummarizeStream(events, processExitCode)
 	hasErrors := len(summary.Errors) > 0 || summary.ExitCode != 0
 	if summary.Status != "" && summary.Status != "success" && summary.Status != "ok" {
 		hasErrors = true
 	}
+	// A captured kill signal must always surface, even if a late run_end reported a
+	// clean exit just before the child was killed during teardown.
+	if strings.TrimSpace(signalDesc) != "" {
+		hasErrors = true
+	}
 	if !hasErrors {
 		output := summary.Text
 		if summary.SessionID != "" {
@@ -149,7 +154,15 @@ func BuildFinalResult(events []streamjson.Event, stderrOutput string, processExi
 	}
 
 	var builder strings.Builder
-	fmt.Fprintf(&builder, "Subagent failed (exit %d)\n", summary.ExitCode)
+	if signal := strings.TrimSpace(signalDesc); signal != "" {
+		// The child was terminated by a signal (exit code -1) rather than exiting.
+		// Surface the signal instead of an opaque "exit -1", and list the common
+		// causes evenhandedly — this branch also covers timeouts and cancellations,
+		// so don't assert OOM.
+		fmt.Fprintf(&builder, "Subagent terminated by a signal (%s) — it was killed before it finished. Common causes: an out-of-memory kill, a timeout, or cancellation; check the signal to tell which. If you were running many sub-agents in parallel, reduce the concurrency.\n", signal)
+	} else {
+		fmt.Fprintf(&builder, "Subagent failed (exit %d)\n", summary.ExitCode)
+	}
 	if len(summary.Errors) > 0 {
 		fmt.Fprintf(&builder, "errors: %s\n", strings.Join(summary.Errors, "; "))
 	}

internal/specialist/streamer_test.go

@@ -25,7 +25,7 @@ func TestParseStreamAndBuildFinalResultSuccess(t *testing.T) {
 	if summary.SessionID != "child" || summary.Text != "done" || summary.ExitCode != 0 || len(summary.Tools) != 1 || summary.Tools[0] != "grep" {
 		t.Fatalf("unexpected summary: %#v", summary)
 	}
-	result := BuildFinalResult(events, "", 0)
+	result := BuildFinalResult(events, "", 0, "")
 	if result.Status != tools.StatusOK || result.Output != "session_id: child\ndone" {
 		t.Fatalf("unexpected final result: %#v", result)
 	}
@@ -41,7 +41,7 @@ func TestBuildFinalResultUsesTextDeltasWhenFinalMissing(t *testing.T) {
 	if err != nil {
 		t.Fatalf("ParseStream returned error: %v", err)
 	}
-	result := BuildFinalResult(events, "", 0)
+	result := BuildFinalResult(events, "", 0, "")
 	if result.Status != tools.StatusOK || result.Output != "session_id: child\nhello world" {
 		t.Fatalf("unexpected final result: %#v", result)
 	}
@@ -82,7 +82,7 @@ func TestBuildFinalResultErrorIncludesDiagnostics(t *testing.T) {
 	if err != nil {
 		t.Fatalf("ParseStream returned error: %v", err)
 	}
-	result := BuildFinalResult(events, "stderr text", 0)
+	result := BuildFinalResult(events, "stderr text", 0, "")
 	if result.Status != tools.StatusError {
 		t.Fatalf("Status = %s, want error", result.Status)
 	}
@@ -93,6 +93,33 @@ func TestBuildFinalResultErrorIncludesDiagnostics(t *testing.T) {
 	}
 }
 
+// A child terminated by a signal (exit code -1) must surface the signal + an
+// actionable hint, not an opaque "Subagent failed (exit -1)".
+func TestBuildFinalResultSurfacesKillSignal(t *testing.T) {
+	events, err := ParseStream(strings.NewReader(strings.Join([]string{
+		`{"schemaVersion":2,"type":"run_start","runId":"run_1","sessionId":"child"}`,
+		`{"schemaVersion":2,"type":"tool_call","runId":"run_1","id":"call_1","name":"read_file"}`,
+		"",
+	}, "\n")))
+	if err != nil {
+		t.Fatalf("ParseStream returned error: %v", err)
+	}
+	result := BuildFinalResult(events, "", -1, "signal: killed")
+	if result.Status != tools.StatusError {
+		t.Fatalf("Status = %s, want error", result.Status)
+	}
+	// Surfaces the signal + lists causes (OOM/timeout/cancellation) without asserting
+	// OOM as the sole cause.
+	for _, want := range []string{"terminated by a signal", "signal: killed", "out-of-memory", "timeout", "cancellation"} {
+		if !strings.Contains(result.Output, want) {
+			t.Fatalf("kill output missing %q:\n%s", want, result.Output)
+		}
+	}
+	if strings.Contains(result.Output, "Subagent failed (exit") {
+		t.Fatalf("signaled child should not show the opaque exit line:\n%s", result.Output)
+	}
+}
+
 func TestParseStreamRejectsInvalidLines(t *testing.T) {
 	_, err := ParseStream(strings.NewReader(`{"schemaVersion":2,"runId":"run_1"}` + "\n"))
 	if err == nil || !strings.Contains(err.Error(), "type is required") {

internal/swarm/coordinator.go

@@ -166,6 +166,12 @@ func (c *Coordinator) Fail(id, errMsg string) error {
 	return c.finish(id, StatusFailed, "", errMsg, "")
 }
 
+// FailWithSession marks a task failed but keeps its child session id, so a member
+// that ran and failed (e.g. exited non-zero / hit max-turns) is still drillable.
+func (c *Coordinator) FailWithSession(id, errMsg, sessionID string) error {
+	return c.finish(id, StatusFailed, "", errMsg, sessionID)
+}
+
 func (c *Coordinator) finish(id string, status TaskStatus, result, errMsg, sessionID string) error {
 	c.mu.Lock()
 	defer c.mu.Unlock()

internal/swarm/launcher_specialist.go

@@ -2,8 +2,10 @@ package swarm
 
 import (
 	"context"
+	"errors"
 
 	"github.com/Gitlawb/zero/internal/specialist"
+	"github.com/Gitlawb/zero/internal/tools"
 )
 
 // NewSpecialistLauncher adapts internal/specialist.Executor into a
@@ -54,7 +56,18 @@ func NewSpecialistLauncher(executor specialist.Executor) MemberLauncher {
 			MemberAutonomy: true,
 		})
 		if err != nil {
-			return MemberResult{}, err
+			// Preserve the child session id on a post-start failure too (exec.go
+			// returns it on the error path) so lifecycle's FailWithSession can keep
+			// the failed member drillable, not just the StatusError case below.
+			return MemberResult{SessionID: res.SessionID}, err
+		}
+		if res.Result.Status == tools.StatusError {
+			// The child ran but its task FAILED (e.g. non-zero exit / max-turns).
+			// Surface it as a member failure so the swarm marks it [failed], not
+			// [done] — otherwise the orchestrator (which can't see the AGENTS panel)
+			// trusts incomplete work. Keep the session id so the failed member is
+			// still drillable, and carry its report as the failure message.
+			return MemberResult{SessionID: res.SessionID}, errors.New(res.Result.Output)
 		}
 		return MemberResult{Result: res.Result.Output, SessionID: res.SessionID}, nil
 	}}

internal/swarm/launcher_specialist_test.go

@@ -67,3 +67,50 @@ func TestSpecialistLauncherRunsUnregisteredSwarmAgent(t *testing.T) {
 		t.Fatalf("member args missing agent type: %#v", gotArgs)
 	}
 }
+
+// A member whose child exits non-zero (e.g. exit 4 / max-turns) must be reported as
+// a FAILURE — otherwise the swarm marks it [done] and the orchestrator trusts
+// incomplete work. The failed member keeps its session id (drill-in) and the child
+// report rides along as the failure message.
+func TestSpecialistLauncherMarksNonZeroExitAsFailed(t *testing.T) {
+	four := 4
+	executor := specialist.Executor{
+		BinaryPath:   "/usr/local/bin/zero",
+		NewSessionID: func() (string, error) { return "member_task", nil },
+		Load: func(specialist.LoadOptions) (specialist.LoadResult, error) {
+			return specialist.LoadResult{}, nil
+		},
+		RunChild: func(ctx context.Context, binaryPath string, args []string, progress func(streamjson.Event)) (specialist.ChildRunResult, error) {
+			return specialist.ChildRunResult{
+				Events: []streamjson.Event{
+					{Type: streamjson.EventRunStart, SessionID: "member_task"},
+					{Type: streamjson.EventFinal, Text: "i could not finish the objective"},
+					{Type: streamjson.EventRunEnd, Status: "error", ExitCode: &four},
+				},
+				ExitCode: 4,
+			}, nil
+		},
+	}
+
+	handle, err := NewSpecialistLauncher(executor).Launch(context.Background(), MemberSpec{
+		ID:           "m1",
+		TaskID:       "m1",
+		AgentType:    "subagent",
+		Team:         "probe",
+		Task:         "a task too big for the budget",
+		SystemPrompt: "You are a subagent spawned to complete a specific task.",
+	})
+	if err != nil {
+		t.Fatalf("launch: %v", err)
+	}
+	res, err := handle.Wait()
+	if err == nil {
+		t.Fatal("a member that exited non-zero must be reported as FAILED, got nil error")
+	}
+	if !strings.Contains(err.Error(), "exit 4") {
+		t.Fatalf("failure should carry the child report (exit 4), got %q", err.Error())
+	}
+	if res.SessionID != "member_task" {
+		t.Fatalf("a failed member must keep its session id for drill-in, got %q", res.SessionID)
+	}
+}

internal/swarm/lifecycle.go

@@ -71,7 +71,9 @@ func (s *Swarm) watch(t *Team, m *Member, spec MemberSpec) {
 			}
 			// fall through to record the original error if relaunch fails
 		}
-		_ = s.coord.Fail(m.TaskID, memberError(err))
+		// res.SessionID is preserved by the handle even on error, so a member that
+		// ran then failed stays drillable; a pure launch error carries an empty id.
+		_ = s.coord.FailWithSession(m.TaskID, memberError(err), res.SessionID)
 	} else {
 		_ = s.coord.CompleteWithSession(m.TaskID, res.Result, res.SessionID)
 	}

internal/swarm/tools.go

@@ -103,6 +103,25 @@ func errResult(format string, a ...any) tools.Result {
 	return tools.Result{Status: tools.StatusError, Output: "Error: " + fmt.Sprintf(format, a...)}
 }
 
+// agentTypeProperty builds the schema for an agent-type parameter, constraining it
+// to the roster's currently registered types (the built-ins plus any user-registered
+// agents) via an enum so a model can't spawn or hand off to an unknown type — the
+// schema teaches the valid set up front instead of the model learning it from a
+// failed call. Falls back to a free-form string if the roster is unavailable or
+// empty (so the tool never advertises an empty, un-satisfiable enum).
+func agentTypeProperty(sw *Swarm, description string) tools.PropertySchema {
+	prop := tools.PropertySchema{Type: "string", Description: description}
+	if sw == nil {
+		return prop
+	}
+	if registry := sw.Registry(); registry != nil {
+		if types := registry.AgentTypes(); len(types) > 0 {
+			prop.Enum = types
+		}
+	}
+	return prop
+}
+
 // ---- swarm_spawn -----------------------------------------------------------
 
 type spawnTool struct {
@@ -118,7 +137,7 @@ func (t *spawnTool) Parameters() tools.Schema {
 	return tools.Schema{
 		Type: "object",
 		Properties: map[string]tools.PropertySchema{
-			"agent_type": {Type: "string", Description: "Roster agent type to spawn (e.g. teammate, subagent)."},
+			"agent_type": agentTypeProperty(t.sw, "Roster agent type to spawn."),
 			"task":       {Type: "string", Description: "The focused task/briefing for the member."},
 			"team":       {Type: "string", Description: "Team to spawn into. Defaults to \"default\"."},
 		},
@@ -353,7 +372,7 @@ func (t *handoffTool) Parameters() tools.Schema {
 		Type: "object",
 		Properties: map[string]tools.PropertySchema{
 			"task_id":       {Type: "string", Description: "Task id to hand off."},
-			"to_agent_type": {Type: "string", Description: "Roster agent type to take over."},
+			"to_agent_type": agentTypeProperty(t.sw, "Roster agent type to take over."),
 			"note":          {Type: "string", Description: "Optional handoff note delivered to the new member's inbox."},
 			"team":          {Type: "string", Description: "Team the task belongs to. Defaults to \"default\"."},
 		},

internal/swarm/tools_test.go

@@ -2,6 +2,7 @@ package swarm
 
 import (
 	"context"
+	"slices"
 	"strings"
 	"testing"
 	"time"
@@ -10,6 +11,46 @@ import (
 	"github.com/Gitlawb/zero/internal/tools"
 )
 
+func TestSpawnAndHandoffAgentTypeEnumReflectsRoster(t *testing.T) {
+	sw := newSwarmFor(t, newLauncher(okFor))
+	want := sw.Registry().AgentTypes() // sorted built-ins: subagent, teammate
+
+	spawnEnum := (&spawnTool{sw: sw}).Parameters().Properties["agent_type"].Enum
+	if !slices.Equal(spawnEnum, want) {
+		t.Fatalf("spawn agent_type enum = %v, want roster %v", spawnEnum, want)
+	}
+	if !slices.Contains(spawnEnum, "subagent") || !slices.Contains(spawnEnum, "teammate") {
+		t.Fatalf("enum missing built-in roster types: %v", spawnEnum)
+	}
+	handoffEnum := (&handoffTool{sw: sw}).Parameters().Properties["to_agent_type"].Enum
+	if !slices.Equal(handoffEnum, want) {
+		t.Fatalf("handoff to_agent_type enum = %v, want roster %v", handoffEnum, want)
+	}
+
+	// A user-registered custom type must extend the enum (not a hardcoded list).
+	if err := sw.Registry().Register(Definition{AgentType: "researcher"}); err != nil {
+		t.Fatalf("register custom agent: %v", err)
+	}
+	spawnEnum = (&spawnTool{sw: sw}).Parameters().Properties["agent_type"].Enum
+	if !slices.Contains(spawnEnum, "researcher") {
+		t.Fatalf("custom agent type not reflected in spawn enum: %v", spawnEnum)
+	}
+	handoffEnum = (&handoffTool{sw: sw}).Parameters().Properties["to_agent_type"].Enum
+	if !slices.Contains(handoffEnum, "researcher") {
+		t.Fatalf("custom agent type not reflected in handoff enum: %v", handoffEnum)
+	}
+}
+
+func TestAgentTypePropertyFallsBackWithoutRoster(t *testing.T) {
+	prop := agentTypeProperty(nil, "desc")
+	if prop.Type != "string" || prop.Description != "desc" {
+		t.Fatalf("unexpected property: %+v", prop)
+	}
+	if prop.Enum != nil {
+		t.Fatalf("nil swarm must not advertise an (empty) enum, got %v", prop.Enum)
+	}
+}
+
 func TestCollapseRuneSafeTruncation(t *testing.T) {
 	// 300 multi-byte runes: truncation must not split a rune (no invalid UTF-8).
 	got := collapse(strings.Repeat("🚀", 300))

internal/tui/command_center.go

@@ -441,6 +441,8 @@ func (m model) handleModelCommand(args string) (model, string) {
 	m.providerProfile = nextProfile
 	m.provider = nextProvider
 	m.providerName = displayValue(nextProfile.Name, string(metadata.ProviderKind))
+	// Keep sub-agent child processes on the same provider we just switched to.
+	config.SetActiveProviderEnv(nextProfile.Name)
 	m.modelName = target.modelID
 	resetEffort := false
 	if m.reasoningEffort != "" && !reasoningEffortAllowed(target.reasoningEfforts, m.reasoningEffort) {
@@ -516,6 +518,8 @@ func (m model) switchProviderModel(providerName, modelID string) (model, string)
 	m.providerProfile = target
 	m.providerName = target.Name
 	m.modelName = target.Model
+	// Keep sub-agent child processes on the same provider we just switched to.
+	config.SetActiveProviderEnv(target.Name)
 	if strings.TrimSpace(m.userConfigPath) != "" {
 		_, _ = config.SetActiveProvider(m.userConfigPath, target.Name)
 		_, _ = config.SetProviderModel(m.userConfigPath, target.Name, target.Model)

internal/tui/commands.go

@@ -40,6 +40,7 @@ const (
 	commandImage
 	commandAddDir
 	commandSelfCorrect
+	commandTurns
 	commandUnknown
 )
 
@@ -241,6 +242,13 @@ var commandDefinitions = []commandDefinition{
 		description: "Show or set post-edit self-correction depth (LSP-only default; on/tests/full add the project test plan; off/lsp disable tests, LSP-only).",
 		kind:        commandSelfCorrect,
 	},
+	{
+		name:        "/turns",
+		usage:       "/turns [n]",
+		group:       commandGroupSession,
+		description: "Show or set the per-run tool-turn budget for this session (raise it for long multi-step tasks).",
+		kind:        commandTurns,
+	},
 	{
 		name:        "/help",
 		usage:       "/help",

internal/tui/model.go

@@ -3465,6 +3465,18 @@ func (m model) handleSubmit() (tea.Model, tea.Cmd) {
 		m, text = m.handleSelfCorrectCommand(command.text)
 		m.transcript = reduceTranscript(m.transcript, transcriptAction{kind: actionAppendSystem, text: text})
 		return m, nil
+	case commandTurns:
+		// Changing the budget mid-run would mutate the inherited ZERO_MAX_TURNS env
+		// that sub-agents spawned later in THIS run read, making the run's budget
+		// inconsistent. Require an idle session (the new budget applies next run).
+		if m.pending && strings.TrimSpace(command.text) != "" {
+			m.transcript = reduceTranscript(m.transcript, transcriptAction{kind: actionAppendSystem, text: "Turns\nFinish or stop the current run before changing the tool-turn budget."})
+			return m, nil
+		}
+		text := ""
+		m, text = m.handleTurnsCommand(command.text)
+		m.transcript = reduceTranscript(m.transcript, transcriptAction{kind: actionAppendSystem, text: text})
+		return m, nil
 	case commandTheme:
 		text := ""
 		m, text = m.handleThemeCommand(command.text)

internal/tui/session_controls.go

@@ -9,6 +9,7 @@ import (
 	tea "charm.land/bubbletea/v2"
 
 	"github.com/Gitlawb/zero/internal/agent"
+	"github.com/Gitlawb/zero/internal/config"
 	"github.com/Gitlawb/zero/internal/modelregistry"
 	"github.com/Gitlawb/zero/internal/sessions"
 	"github.com/Gitlawb/zero/internal/usage"
@@ -256,6 +257,42 @@ func (m model) handleSelfCorrectCommand(args string) (model, string) {
 	return m, m.selfCorrectText()
 }
 
+// maxTurnsCeiling caps the per-session /turns budget so a typo (e.g. /turns 99999)
+// can't set an absurd ceiling; real multi-step tasks fit comfortably under it. Shared
+// with config so applyEnv enforces the same bound on an inherited ZERO_MAX_TURNS.
+const maxTurnsCeiling = config.MaxTurnsCeiling
+
+func (m model) handleTurnsCommand(args string) (model, string) {
+	args = strings.TrimSpace(args)
+	if args == "" || strings.EqualFold(args, "status") {
+		return m, m.turnsText()
+	}
+	n, err := strconv.Atoi(args)
+	if err != nil || n < 1 {
+		return m, "Turns\nUsage: /turns <n> — set the per-run tool-turn budget for this session (a positive number, e.g. /turns 150)."
+	}
+	if n > maxTurnsCeiling {
+		n = maxTurnsCeiling
+	}
+	m.agentOptions.MaxTurns = n
+	// Propagate the budget to spawned sub-agents / swarm members (which inherit the
+	// environment) so a delegated task gets the same budget, not config.json's default.
+	config.SetMaxTurnsEnv(n)
+	return m, m.turnsText()
+}
+
+func (m model) turnsText() string {
+	return renderCommandOutput(commandOutput{
+		Title:  "Turns",
+		Status: commandStatusOK,
+		Sections: []commandSection{{
+			Title: "State",
+			Lines: []string{fmt.Sprintf("max tool-turns per run: %d", m.agentOptions.MaxTurns)},
+		}},
+		Hints: []string{fmt.Sprintf("/turns <n> sets this session's tool-turn budget (max %d); raise it for long multi-step tasks like delegation/swarm runs", maxTurnsCeiling)},
+	})
+}
+
 func (m model) selfCorrectText() string {
 	depth := "LSP diagnostics only — fast, scoped to changed files"
 	if m.selfCorrectTests {

internal/tui/sidebar.go

@@ -261,13 +261,11 @@ func (m model) swarmSpawnedAgents() []swarmAgent {
 			switch a.state {
 			case "done", "failed", "completed", "cancelled":
 				a.finishing = true
-				if m.pending {
-					// Run still going: keep it visible and clickable, no fade.
-					a.finishedAt = time.Time{}
-					live = append(live, a)
-					continue
-				}
-				// Turn ended: fade out over the linger window, then drop.
+				// A member drops once ITS OWN task completes — not when the whole turn
+				// ends: fade out over the linger window from when it was first seen
+				// finished (stamped each tick by stampSwarmDone), then remove. This
+				// holds whether or not the overall run is still in flight, mirroring
+				// how finished specialists drop (sidebarSpecialists).
 				doneAt, stamped := m.swarmDoneAt[a.id]
 				if stamped && m.now().Sub(doneAt) >= sidebarAgentLinger {
 					continue // past the linger window — remove

internal/tui/sidebar_test.go

@@ -391,32 +391,32 @@ func TestSidebarShowsSwarmSpawnedAgents(t *testing.T) {
 // row (e.g. a resumed transcript that dropped the call): the member is still
 // A finished member stays visible (and clickable) while the run is still in
 // flight, so the user can inspect it; only once the turn ends does it drop.
-func TestSwarmAgentsPersistWhileRunInFlight(t *testing.T) {
+func TestSwarmAgentDropsOnOwnCompletionEvenMidRun(t *testing.T) {
 	base := time.Date(2026, 6, 24, 12, 0, 0, 0, time.UTC)
 	m := sidebarTestModel()
 	m.now = func() time.Time { return base }
-	m.pending = true  // run still going
+	m.pending = true  // run STILL going — a member must still drop on its OWN completion
 	m.activeRunID = 7 // exercise the run-scoped filter with a non-zero id
 	m.transcript = append(m.transcript,
 		transcriptRow{kind: rowToolCall, tool: "swarm_spawn", detail: "build homepage", runID: 7},
 		transcriptRow{kind: rowToolResult, tool: "swarm_spawn", detail: "Spawned subagent as task subagent-1 on team default.", runID: 7},
 		transcriptRow{kind: rowToolResult, tool: "swarm_collect", detail: "Results: 1 task(s)\n- subagent-1 [done] build homepage", runID: 7},
 	)
-	// Long past the linger window — but it must still show while pending.
-	m.swarmDoneAt = map[string]time.Time{"subagent-1": base.Add(-10 * sidebarAgentLinger)}
-
+	// Just finished, still within the linger window: shows briefly with a fading ✓.
+	m.swarmDoneAt = map[string]time.Time{"subagent-1": base.Add(-sidebarAgentLinger / 2)}
 	agents := m.swarmSpawnedAgents()
 	if len(agents) != 1 {
-		t.Fatalf("a finished member must stay while the run is in flight, got %d: %+v", len(agents), agents)
+		t.Fatalf("within the linger window a finished member should still show (fading), got %d: %+v", len(agents), agents)
 	}
 	if !agents[0].finishing {
 		t.Fatalf("a finished member should render done (✓), got %+v", agents[0])
 	}
 
-	// Once the turn ends, the long-finished member fades out and drops.
-	m.pending = false
+	// Past the linger window: it drops — even though the overall run is still in
+	// flight (previously a finished member lingered until the whole turn ended).
+	m.swarmDoneAt = map[string]time.Time{"subagent-1": base.Add(-2 * sidebarAgentLinger)}
 	if got := len(m.swarmSpawnedAgents()); got != 0 {
-		t.Fatalf("after the turn ends a long-finished member should drop, got %d", got)
+		t.Fatalf("a member past its linger window must drop on its own completion mid-run, got %d", got)
 	}
 }
 

internal/tui/turns_command_test.go

@@ -0,0 +1,62 @@
+package tui
+
+import (
+	"os"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+func TestHandleTurnsCommand(t *testing.T) {
+	// Isolate the inherited-by-children budget env this command exports.
+	t.Setenv("ZERO_MAX_TURNS", "")
+
+	t.Run("sets a valid budget and exports it for children", func(t *testing.T) {
+		got, out := model{}.handleTurnsCommand("150")
+		if got.agentOptions.MaxTurns != 150 {
+			t.Fatalf("MaxTurns = %d, want 150", got.agentOptions.MaxTurns)
+		}
+		if !strings.Contains(out, "150") {
+			t.Fatalf("output should report 150, got %q", out)
+		}
+		if env := os.Getenv("ZERO_MAX_TURNS"); env != "150" {
+			t.Fatalf("ZERO_MAX_TURNS = %q, want 150 (so sub-agents inherit it)", env)
+		}
+	})
+
+	t.Run("clamps above the ceiling (env too)", func(t *testing.T) {
+		got, _ := model{}.handleTurnsCommand("99999")
+		if got.agentOptions.MaxTurns != maxTurnsCeiling {
+			t.Fatalf("MaxTurns = %d, want clamp to %d", got.agentOptions.MaxTurns, maxTurnsCeiling)
+		}
+		if env := os.Getenv("ZERO_MAX_TURNS"); env != strconv.Itoa(maxTurnsCeiling) {
+			t.Fatalf("ZERO_MAX_TURNS = %q, want clamped %d", env, maxTurnsCeiling)
+		}
+	})
+
+	t.Run("invalid / non-positive input is rejected without changing the budget", func(t *testing.T) {
+		for _, in := range []string{"abc", "0", "-5", "3.5"} {
+			m := model{}
+			m.agentOptions.MaxTurns = 42
+			got, out := m.handleTurnsCommand(in)
+			if got.agentOptions.MaxTurns != 42 {
+				t.Fatalf("input %q changed MaxTurns to %d, want unchanged (42)", in, got.agentOptions.MaxTurns)
+			}
+			if !strings.Contains(out, "Usage") {
+				t.Fatalf("input %q should show usage, got %q", in, out)
+			}
+		}
+	})
+
+	t.Run("empty / status shows the current budget without changing it", func(t *testing.T) {
+		m := model{}
+		m.agentOptions.MaxTurns = 42
+		got, out := m.handleTurnsCommand("")
+		if got.agentOptions.MaxTurns != 42 {
+			t.Fatalf("status changed MaxTurns to %d, want 42", got.agentOptions.MaxTurns)
+		}
+		if !strings.Contains(out, "42") {
+			t.Fatalf("status should report current 42, got %q", out)
+		}
+	})
+}