fix(cli): unstick streamingState after Esc-cancel + close leaked turn span

[mabry1985]

Why

Reproduced on Langfuse: session 442ed5c7, turn ba924d250d7c. The trace shows a 739-second turn with zero LLM activity in the middle — only the turn root span and two LLM calls clustered at the very end (which turn out to be the recap + prompt-suggestion calls firing on streamingState=Idle). The 12 minutes weren't model work; the OTel turn span just leaked open and got force-closed when the next prompt finally went through.

User-side, the symptom was: press Esc to cancel a turn → anything typed afterwards is silently dropped → app feels hung.

Root cause (two bugs interacting)

1. cancelOngoingRequest doesn't clear stuck toolCalls. It aborts the controller and flips isResponding=false, but if a tool ignores its AbortSignal (or finishes between the cancel firing and responseSubmittedToGemini being set), the toolCall stays in a non-terminal state. streamingState (useGeminiStream.ts:424-437) computes Responding, and submitQuery's guard (1305-1314) silently returns every subsequent submission. The in-code comment at line 244-245 already documents this class of bug for a different root cause.
2. cancelOngoingRequest doesn't call endTurnSpan, so the OTel turn span leaks. The recap + usePromptSuggestions LLM calls that fire on streamingState=Idle then nest under the dead span — Langfuse reports the turn as 12 minutes long when the actual model work was 1.7s.

Inheritance check

• Upstream QwenLM/qwen-code main: identical cancelOngoingRequest shape, identical silent-return guard. Same bug. Issue #914 closed without resolution.
• Further upstream google-gemini/gemini-cli: PR #21960 (which closed #21096) fixed a different cancel-related issue — retry-loop loading indicator showing stale "still on it" text. Not the same fix. Open issue #18525 ("Agent Stuck between Responses") is essentially this same symptom, still unresolved.
• protoCLI: the toolCall-stuck-state side is inherited. The leaked-turn-span side is fork-only because startTurnSpan / endTurnSpan and the activeTurnContext are part of our agent harness (see docs/architecture/divergence-from-upstream.md).

Fix

1. useReactToolScheduler exposes forceCancelStaleToolCalls() — flips responseSubmittedToGemini=true on terminal calls and synthesizes a cancelled state for non-terminal calls (with a "User cancelled. Tool was force-cleared after abort signal did not stop it within the grace window" message in responseParts so downstream consumers don't choke).
2. cancelOngoingRequest:
   • calls markToolsAsSubmitted on every current toolCall immediately (handles the common case),
   • schedules a 3s setTimeout that runs forceCancelStaleToolCalls and surfaces a WARNING if anything had to be force-cleared,
   • calls endTurnSpan('ok') so the recap/suggestion calls don't attach to the dead span.
3. submitQuery: when dropping a submission because streamingState !== Idle, surfaces a clear WARNING explaining the state (Responding / WaitingForConfirmation / Backgrounded) and the next step. No more silent drops.

Tests

• 3,767 cli tests + 5,337 core tests pass.
• useGeminiStream.test.tsx's 49-test cancellation suite continues to pass with the new flow.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Improved handling of user-initiated cancellations to properly clean up stuck or stale operations.
  • Fixed state synchronization issues that could leave incomplete operations unresolved.

• New Features

  • Added informative warning messages when operations cannot be submitted during active requests, guiding users on next steps.
  • Enhanced automatic cleanup of abandoned operations with 3-second timeout mechanism.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

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Run ID: 1e3be83c-9574-485b-a84e-8d13057f38a4

📥 Commits

Reviewing files that changed from the base of the PR and between d697ddf and a5005ca.

📒 Files selected for processing (2)

• packages/cli/src/ui/hooks/useGeminiStream.ts
• packages/cli/src/ui/hooks/useReactToolScheduler.ts

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Walkthrough

The changes add a cancellation mechanism for stale tool calls. useReactToolScheduler exports a new forceCancelStaleToolCalls callback that synthesizes cancelled entries and updates tool-call state. useGeminiStream integrates this callback into its cancellation path, closing OTel spans, blocking new submissions, and emitting warning messages when tool calls are cleared.

Changes

Cohort / File(s)	Summary
Tool Call Cancellation Enhancement packages/cli/src/ui/hooks/useReactToolScheduler.ts, packages/cli/src/ui/hooks/useGeminiStream.ts	Added forceCancelStaleToolCalls callback to useReactToolScheduler that marks non-terminal tool calls as cancelled and updates state. useGeminiStream now uses this callback on user cancellation, closes OTel turn spans, blocks new submissions, and emits warnings when stale tool calls are cleared.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

✨ Finishing Touches

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• Create stacked PR
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🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/cancel-clears-stuck-state

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