[Gourav224]

Fixes #23349

Problem

When the Cursor SDK's stall detector fires, it aborts the request and then rejects an internal promise nothing awaits. The server's unhandledRejection guard only knew two Cursor errors, so this AbortError fell through to process.exit(1) and took the whole backend (and every other provider's sessions) down. This is the same pattern as #22897, with a different error.

Fix

isCursorStallAbort recognizes an AbortError raised from the SDK's onStall (the SDK is minified, so the error name plus the onStall frame in its stack is the only handle). The guard logs it and keeps the server running. Any other AbortError still exits as before.

Evidence

CursorSdk.test.ts gains two cases: a stall abort no longer exits, and an AbortError from elsewhere still does. The first fails without the change and passes with it (4/4 pass; lint and format clean).

Not verified

I did not reproduce a real SDK stall; the trigger is unknown per the issue. The test uses an error shaped like the one in the reported stack. If the SDK changes the frame name, the guard would stop matching and fall back to today's behavior.

🤖 Generated with Claude Code

[macroscopeapp]

Approvability

Verdict: Approved at ac5dc48

Macroscope's review found this PR approvable — Adds a narrowly scoped Cursor SDK stall-abort guard so that this known internal recovery error no longer terminates the server, while unrelated aborts and rejections still do. Regression tests cover both behaviors, and no broader product or infrastructure changes are included.

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Reviewing files that changed from the base of the PR and between ac5dc48 and 38250f5.

📒 Files selected for processing: 2

• packages/provider-cursor/src/server/CursorSdk.test.ts
• packages/provider-cursor/src/server/CursorSdk.ts

🚧 Files skipped from review as they are similar to previous changes: 2

• packages/provider-cursor/src/server/CursorSdk.ts
• packages/provider-cursor/src/server/CursorSdk.test.ts

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📝 Walkthrough

The Cursor SDK server now recognizes unhandled AbortErrors with onStall in their stack and keeps running for those rejections. Tests verify that other abort errors still trigger exit handling.

Changes: Cursor stall abort handling

Layer / File(s)	Summary
Detect and handle stall aborts packages/provider-cursor/src/server/CursorSdk.ts, packages/provider-cursor/src/server/CursorSdk.test.ts	The rejection handler identifies AbortErrors whose stack contains onStall, logs, and returns. Tests verify that this case does not call process.exit, while another abort error calls it with code 1.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to 38250

The reported Cursor stall abort can leave the server running while other tested aborts retain exit handling. No actionable merge-blocking risk remains.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title is concise, specific, and accurately describes the primary fix: preventing an aborted Cursor SDK stall from stopping the server.
Description check		The description explains the problem, fix, linked issue, focused tests, observed results, and verification limits. It uses "Fix" and "Evidence" instead of the template headings "Change" and "Verificat…
Linked Issues check		Issue #23349 requires the Cursor SDK stall AbortError to stop terminating the shared backend. CursorSdk.ts matches an AbortError with an onStall stack frame, logs it, and returns before `proce…
Out of Scope Changes check		The reviewed changes are limited to the Cursor SDK unhandled-rejection guard and its tests. The production change directly implements #23349. The tests verify the new exception path and preserve exist…

Full details: Description check

Explanation

The description explains the problem, fix, linked issue, focused tests, observed results, and verification limits. It uses "Fix" and "Evidence" instead of the template headings "Change" and "Verification," but the required information is present. The linked issue also provides scope context for this focused bug fix.

Full details: Linked Issues check

Explanation

Issue #23349 requires the Cursor SDK stall AbortError to stop terminating the shared backend. CursorSdk.ts matches an AbortError with an onStall stack frame, logs it, and returns before process.exit(1). Other AbortError values still use the exit path. CursorSdk.test.ts covers both behaviors.

Full details: Out of Scope Changes check

Explanation

The reviewed changes are limited to the Cursor SDK unhandled-rejection guard and its tests. The production change directly implements #23349. The tests verify the new exception path and preserve existing exit behavior. No unrelated change is shown.

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Actionable comments posted: 1

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Inline comments:
Review comments at @packages/provider-cursor/src/server/CursorSdk.ts:
- Line 56: Update the `onStall` stack predicate to match an actual call frame
rather than any occurrence in stack text, so an `AbortError` message containing
`onStall` follows the existing exit path; add a near-miss test for that message
case.

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• packages/provider-cursor/src/server/CursorSdk.test.ts
• packages/provider-cursor/src/server/CursorSdk.ts

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[shivamhwp]

Tested this in a real dev server (vp run dev) with the web app open, on main (05b697f, this PR's base) and then on this PR (38250f5).

How I triggered it: a test-only --import preload in the server process. On a signal it raises the rejection the SDK's stall detector raises: an AbortError created inside Is.onStall (the SDK's onStall:()=>{…,N()} in dist/cjs/689.js), rejected from a promise nothing awaits. I couldn't get the real SDK to hit this end to end. Against a fake Cursor backend the stall detector fired and retried, but it didn't crash main either, so this injects the same rejection into the real server instead. The orange/green box is a test overlay showing the server log live.

main: the server prints the DOMException [AbortError] and exits (Failed running 'src/bin.ts'). The app goes to "corex-t3 is reconnecting" and stays there.

main.mp4

This PR: the server logs Cursor SDK aborted a stalled request. The server will keep running. and keeps serving. After that I opened a thread, a new thread, and Settings, and all of them loaded from the server.

pr.mp4

Unit test (CursorSdk.test.ts):

• this PR: 5 passed
• main's guard: keeps the server running when the SDK aborts a stalled request fails (expected [ [ 1 ] ] to deeply equal [], meaning process.exit(1) was called), and the other 4 pass

Looks good to merge.

[shivamhwp]

Re-tested with the real Cursor SDK and a real Cursor account

The earlier recordings used an injected rejection. This time I ran a real Cursor agent (Composer 2.5) in a dev T3 server, signed in through the SDK, with all Cursor traffic going through a local HTTPS proxy in front of api2.cursor.sh. The proxy kept the SDK on HTTP/2, the same path users are on, and could freeze replies or drop the network on command.

main (05b697f): no crash in any real stall

Scenario	Result
Freeze replies mid-answer, hold 45s	Stall detector aborted at 34s, SDK retried, answer finished, server up
Freeze while a 21s shell command runs	Aborted at 35s, retried, server up
Network dead before the run, so the 1.2 MB run upload is blocked by HTTP/2 flow control	Aborted at 30s, retried once the network came back, server up
Freeze while a 71s command is still running	Aborted at 35s with the tool still running, retried, server up
Network dead for 3 minutes mid-answer	5 stall aborts in a row, SDK kept retrying with backoff, recovered, server up

On the PR (38250f5), the mid-answer freeze behaved the same as main: abort at 30s, retry, answer finished.

What this shows

• The issue's frame 689.js:1:111536 is exactly the N() context cancel inside this onStall in @cursor/sdk 1.0.35. That is the code I triggered above, so the PR's frame check matches the reported error.
• In every case I could create, the SDK handled that abort itself and retried. The stray unhandled rejection from Cursor SDK stall AbortError crashes the desktop backend #23349 needs a condition I couldn't reproduce, possibly the macOS desktop runtime, heavy concurrent sessions, or timing. The stack only shows who cancelled, not which promise was left unhandled.
• When the SDK does handle this abort, it retries. So ignoring a stray copy of it most likely leaves the Cursor session to recover, instead of process.exit(1) taking down every provider's sessions.

Still fine to merge: low risk, a narrow match, and easy to revert.

Unrelated, noticed while testing: on Linux, Cursor in Supervised mode fails to start a turn with Local SDK sandboxing was requested, but sandboxing is not supported in this environment.