fix(tools): bound internal tool calls by the plan deadline, not Bun's fetch default

[icecrasher321]

Summary

Every internal tool call was capped at 5 minutes regardless of plan.

tools/index.ts computes a plan-aware deadline for internal routes — getMaxExecutionTimeout(), 3000s on enterprise — and hands it to its own AbortController. It never handed it to the transport. So Bun's fetch idle timer governed instead, and its default is 300s.

Bun's own source describes that timer as re-arming on writes and body-phase reads but not on response-header reads, making it "an absolute deadline for the header block to complete." An AbortSignal cannot raise it. Any route that computes before it answers therefore dies at five minutes no matter what deadline was computed for it.

Reproduced in production on a workflow whose Function block runs a 15–40 minute sandboxed engine: all 16 parallel shards failed together at 300.5s with a bare fetch failed. An earlier run of the same workflow failed at 250.9s with TimeoutError: The operation timed out.

Type of Change

• Bug fix

Testing

N/A

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		Aug 11, 2026 6:59pm

[cursor]

PR Summary

Medium Risk
Touches the core internal tool HTTP path and timeout behavior for all internal routes on Bun; incorrect deadline mapping could cause hangs or premature failures, but behavior is covered by unit tests and Node is documented as ignoring the option.

Overview
Fixes long internal tool runs (e.g. Function blocks) dying at ~5 minutes even when the executor already computed a much larger plan timeout. Bun’s fetch idle timer defaults to 300s and is not raised by AbortSignal alone; only the in-process abort was wired before.

Adds withFetchDeadline to set Bun’s timeout on RequestInit to match the same deadlineMs used for the local AbortController (or timeout: false when there is no valid positive deadline, so the runtime does not silently keep the 300s default). Adds isTransportTimeoutError to recognize Bun’s opaque TimeoutError / fetch failed cases.

Internal route requests in tools/index.ts wrap fetch with withFetchDeadline(..., timeout) and, on transport timeout, rethrow with tool id, elapsed time, and deadline while preserving the original message for retry classification.

^{Reviewed by Cursor Bugbot for commit 0f421b1. Configure here.}

[greptile-apps]

Greptile Summary

The PR prevents Bun’s default transport timeout from undercutting the plan-aware deadline on internal tool requests.

• Adds a request-init helper that disables Bun’s transport timer while preserving the caller-owned abort signal.
• Annotates recognized transport failures with the tool ID, elapsed time, and configured deadline.
• Adds unit coverage for request-init preservation and transport-timeout recognition.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
apps/sim/lib/core/utils/fetch-deadline.ts	Introduces a focused helper for disabling Bun’s transport timeout and a classifier for recognized transport failures.
apps/sim/lib/core/utils/fetch-deadline.test.ts	Covers helper output, immutability, init preservation, and timeout-error classification.
apps/sim/tools/index.ts	Applies the helper to internal tool requests while retaining the existing AbortController deadline and adds contextual transport errors.

Sequence Diagram

sequenceDiagram
participant Executor as Tool executor
participant Timer as Plan deadline timer
participant Fetch as Bun fetch
participant Route as Internal route
Executor->>Timer: Arm AbortController with plan-aware timeout
Executor->>Fetch: "Request with signal and timeout=false"
Fetch->>Route: Internal tool request
alt Route responds before deadline
Route-->>Fetch: Response
Fetch-->>Executor: Tool response
else Plan deadline expires
Timer->>Fetch: Abort signal
Fetch-->>Executor: AbortError
else Transport fails
Fetch-->>Executor: TimeoutError or fetch failed
Executor->>Executor: Add tool, elapsed-time, and deadline context
end

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_{Reviews (2): Last reviewed commit: "fix(tools): disarm Bun's fetch idle time..." | Re-trigger Greptile}

[icecrasher321]

@greptile

[icecrasher321]

@cursor review

[cursor]

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^{Reviewed by Cursor Bugbot for commit 3d10803. Configure here.}