fix(explicit-user-abort): separate explicit user abort semantics

[icecrasher321]

Summary

Explicit user abort signal must be distinguished to not kill reconnection chance.

Type of Change

• Bug fix

Testing

Tested manually

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Mar 26, 2026 2:07am

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PR Summary

Medium Risk
Touches chat streaming abort/reconnect paths and tool cancellation logic; mistakes could leave streams running, prevent reconnects, or fail to stop tool mutations when users explicitly cancel.

Overview
Separates explicit user stop from passive disconnect/abort across copilot streaming. Server-side chat streaming now tracks both a transport abortController and a new userStopController, propagating userStopSignal through the orchestrator/tool execution stack so only explicit stops trigger tool cancellation and mutation guards.

Improves client resiliency for interrupted streams. useChat refactors resume/reconnect into resumeOrFinalize() and adds exponential-backoff reconnect retries after network errors, while ensuring reconnection UI state (isReconnecting) is cleared on finalize.

^{Written by Cursor Bugbot for commit bc00454. Configure here.}

[greptile-apps]

Greptile Summary

This PR separates "explicit user stop" semantics from passive transport-disconnect semantics by introducing a dedicated userStopController / userStopSignal signal that only fires when the user actively cancels a generation — not when the SSE connection drops. It also adds a 10-attempt exponential-backoff reconnect loop on the client for network errors, and extracts a resumeOrFinalize helper to deduplicate recovery logic.\n\nKey changes:\n- chat-streaming.ts: activeStreams now stores an ActiveStreamEntry { abortController, userStopController }. Both the explicit-abort HTTP endpoint and the Redis-polling abort path fire both controllers together; a plain transport disconnect only fires abortController.\n- tool-execution.ts / base-tool.ts: abortRequested() and assertServerToolNotAborted now check userStopSignal instead of abortSignal, so in-flight tool mutations survive a transport blip and remain available for reconnection.\n- use-chat.ts: New resumeOrFinalize callback and a retry loop (MAX_RECONNECT_ATTEMPTS = 10, base 1 s, max 30 s backoff) that attempts to re-attach to the buffered stream after a network error.\n- P1 bug: After all 10 reconnect attempts are exhausted, isReconnecting is never reset to false. finalize({ error: true }) does not call setIsReconnecting(false), so the UI will be stuck in a reconnecting spinner indefinitely after a full failure.\n- P2: The resumeOrFinalize call inside the reconnect loop does not forward abortController.signal, leaving fetchStreamBatch un-cancellable during reconnect attempts.

Confidence Score: 4/5

Safe to merge after fixing the isReconnecting state leak; the server-side signal separation is correct and well-scoped.

The core server-side change (separating userStopSignal from abortSignal) is logically sound and the propagation chain is complete. The P1 bug in the client-side reconnect loop (isReconnecting not reset on failure) is a visible UI regression but does not affect data integrity or server behavior. One targeted fix resolves it.

apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.ts — reconnect loop error path needs setIsReconnecting(false) before setError.

Important Files Changed

Filename	Overview
apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.ts	Adds resumeOrFinalize helper to deduplicate reconnect logic and introduces a 10-attempt exponential-backoff reconnect loop on network errors; has a P1 bug where isReconnecting is never reset to false after all attempts are exhausted, and a P2 issue where the abort signal is not forwarded in the reconnect loop.
apps/sim/lib/copilot/chat-streaming.ts	Introduces ActiveStreamEntry with a separate userStopController, correctly wiring it through both the explicit-abort endpoint and the Redis-polling path so only user-initiated stops fire userStopSignal.
apps/sim/lib/copilot/orchestrator/sse/handlers/tool-execution.ts	Changes abortRequested to check only userStopSignal (plus wasAborted), not abortSignal, so transport disconnects no longer halt tool execution — intentional for reconnection support.
apps/sim/lib/copilot/tools/server/base-tool.ts	Switches assertServerToolNotAborted to check userStopSignal instead of abortSignal, preventing transport disconnects from blocking server-side tool mutations.
apps/sim/lib/copilot/orchestrator/types.ts	Adds optional userStopSignal to both OrchestratorOptions and ExecutionContext with a clear JSDoc comment distinguishing its semantics.
apps/sim/lib/copilot/orchestrator/index.ts	Threads userStopSignal from options into execContext, straightforward plumbing change.
apps/sim/lib/copilot/orchestrator/tool-executor/index.ts	Forwards userStopSignal from ExecutionContext into ServerToolContext, completing the signal propagation chain.

Sequence Diagram

sequenceDiagram
    participant UI as Client (use-chat)
    participant Server as SSE Server
    participant Redis as Redis

    Note over UI,Server: Happy path — explicit user stop
    UI->>Server: POST /abort (streamId)
    Server->>Server: userStopController.abort()
    Server->>Server: abortController.abort()
    Server->>Server: assertServerToolNotAborted → throws (userStopSignal fired)
    Server-->>UI: stream closed

    Note over UI,Server: Transport disconnect → reconnect
    UI->>Server: fetch SSE stream
    Server-->>UI: connection drops (network error)
    Note over UI: catch block — NOT an AbortError
    UI->>UI: reconnect loop (attempt 1..10, exponential backoff)
    UI->>Server: fetchStreamBatch (replay buffered events)
    Server-->>UI: buffered events + status
    UI->>Server: attachToExistingStream (live tail)
    Server-->>UI: stream resumes
    Note over Server: abortController NOT fired → tools kept running
    Note over Server: userStopSignal NOT fired → assertServerToolNotAborted passes

    Note over UI,Redis: Redis-triggered abort (e.g. from another tab)
    Redis->>Server: set streamAbortKey
    Server->>Server: poll detects key
    Server->>Server: userStopController.abort()
    Server->>Server: abortController.abort()
    Server->>Redis: del streamAbortKey

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[icecrasher321]

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