fix: Cursor steering no longer waits for the turn to finish

[mxdhavgautam]

With Follow-up behavior set to Steer, a message sent while a Cursor turn ran only reached Cursor after the turn finished, so Steer acted like Queue. In one run, Cursor finished a sleep 45 and answered the steer 48s after it was sent.

Why

• The ACP runtime runs one session/prompt at a time (fix(grok): Harden ACP resume with replay-idle load readiness #3156). The Cursor adapter sent the steer as a second prompt without cancelling the first, so it waited behind it.
• Cursor itself handles a second prompt by cancelling the running one. A raw ACP probe sent a prompt mid-run, and Cursor cancelled the first within 9ms and answered the new one. Cursor steering (Fix turn fold proejctions #3041) relied on this before fix(grok): Harden ACP resume with replay-idle load readiness #3156 held the second prompt back.

Fix

• A steer now cancels the running prompt and sends its replacement right away, and the turn continues. Grok already does this. A per-session lock covers a send from its steer decision until the prompt is dispatched, and Stop takes the same lock, so Stop can't land between the cancel and the replacement.
• Queue needed a matching change. The web queue sends a queued message after the next tool call, which would now cut Cursor off mid-task. Cursor's own queue waits for the task to finish. Cursor now reports queuesUntilTurnEnd, and the web queue holds its messages until the turn ends.

Scope: I know outside PRs are expected to stay small and start from a triaged issue, and this one touches more than one area. I'm opening it anyway because it is one behavior, Cursor follow-ups, and it gets in the way every day with Cursor as my daily driver in T3 Code. The adapter change is the fix. The contracts and web lines are only there so Queue keeps waiting for the turn once Steer works. Bug report: #14585.

Related: #13423 fixes Stop running a queued steer. Steers no longer queue here, so that case goes away, but both PRs edit sendTurn, so the second to merge needs a rebase.

Proof: A new adapter test uses a first prompt that never resolves. It times out on main and passes now, checking session/prompt, session/cancel, session/prompt and one completed turn. With the real Cursor CLI (2026.09.28) and sleep 45, the steer was answered in 3.5s on macOS, 5.0s on Linux and 5.5s on Windows, against 48 to 52s on main. In a dev build with Cursor Grok 4.7, Steer stopped a sleep 45 and answered 7s after sending. Queue held a message through two tool calls and sent it after the turn ended. On all three OSes, CursorAdapter.test.ts, queuedMessageStore.test.ts, and QueuedMessageSender.test.tsx pass, and contracts, server, and web typecheck and lint pass.

Before / after (dev build, Cursor Grok 4.7, follow-up sent while sleep 45 runs):

Before (main), Steer: answered 45s after sending, only once sleep 45 finished.

before-steer.mp4

After, Steer: answered 3s after sending, while sleep 45 was still running.

after-steer.mp4

After, Queue: the follow-up stays Queued through both commands and goes out after BOTH_DONE.

after-queue.mp4

Not covered:

• Grok and Antigravity also cancel on a mid-turn send, so their Queue still cuts in at the next tool call. This PR does not change them.
• A queued message that starts uploading attachments just as another client starts a Cursor turn can still interrupt that turn. Closing that needs a queue flag on thread.turn.start.

Note

Created with Claude Opus 5.5 in Claude Code (T3 Code). Reviewed with GPT-6.1 Sol in Codex.

Closes #14585

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR changes Cursor's default mid-turn interaction and queued-message timing across the server, contract, and web client, including canceling active prompts and holding follow-ups until turn completion. Although the contract addition is backward-compatible and targeted tests are included, the unconditional product-default change warrants human review.

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📝 Walkthrough

Walkthrough

Cursor steering now cancels an active prompt before dispatching its replacement. A provider capability setting tells the web client to hold queued follow-ups until the turn ends.

Changes

Cursor steering

Layer / File(s)	Summary
Cursor prompt lifecycle apps/server/src/provider/Layers/CursorAdapter.ts, apps/server/src/provider/Layers/CursorAdapter.test.ts	Steering settles pending approvals and user inputs, cancels the active ACP prompt, and dispatches the replacement prompt. Prompt registration and interruption use a per-session semaphore. Prompt counts use scoped acquisition and release, and only the last in-flight prompt emits turn.completed. The test checks cancellation order, turn ID reuse, and turn events.

Provider capability and queued follow-ups

Layer / File(s)	Summary
Provider capability and queue timing packages/contracts/src/server.ts, apps/server/src/provider/providerSnapshot.ts, apps/server/src/provider/Layers/CursorProvider.ts, apps/web/src/queuedMessageStore.ts, apps/web/src/components/QueuedMessageSender.tsx, apps/web/src/queuedMessageStore.test.ts, apps/web/src/components/QueuedMessageSender.test.tsx, docs/user/composer.md	The provider contract and server snapshot expose queuesUntilTurnEnd, which Cursor sets to true. The web client passes the setting to isQueuedMessageDue, which holds a queued message during a running turn when enabled. Tests cover the due timing, and the composer documentation describes the Cursor-specific behavior.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: 🔵 Low · up to a4350

Immediate Cursor steering is implemented, but an automatic queued attachment can unexpectedly interrupt a turn started during its upload. Merge with explicit acceptance of this narrow limitation, or recheck queue eligibility after uploads.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 9 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main fix: Cursor steering no longer waits for the current turn to finish.
Description check	✅ Passed	The description explains the problem, fix, scope, linked issue, verification results, limitations, and agent usage. Although it uses custom headings instead of the template headings, it provides the r…
Linked Issues check	✅ Passed	The changes satisfy the coding requirements in [#14585]. CursorAdapter uses a per-session lifecycle semaphore to serialize steer dispatch with cancellation and replacement registration. The adapter …
Out of Scope Changes check	✅ Passed	The changes stay within [#14585]. The contracts, provider snapshot, web queue logic, documentation, and tests directly support Cursor steer cancellation or the required Queue behavior. No unrelated ch…

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @apps/server/src/provider/Layers/CursorAdapter.ts:
- Around line 1150-1160: Reset ctx.assistantReply in the steered-prompt path
before dispatching the replacement prompt. Locate the steeringTurnId branch in
CursorAdapter and clear the cancelled prompt’s transport failure so the later
failure guard cannot reject a successful replacement that emits no content
delta.

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📒 Files selected for processing (10)

• apps/server/src/provider/Layers/CursorAdapter.test.ts
• apps/server/src/provider/Layers/CursorAdapter.ts
• apps/server/src/provider/Layers/CursorProvider.ts
• apps/server/src/provider/providerSnapshot.ts
• apps/web/src/components/QueuedMessageSender.test.tsx
• apps/web/src/components/QueuedMessageSender.tsx
• apps/web/src/queuedMessageStore.test.ts
• apps/web/src/queuedMessageStore.ts
• docs/user/composer.md
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[coderabbitai]

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⚠️ Outside diff range comments (1)

🟡 Minor · Recheck the automatic queue state after attachment uploads. · QueuedMessageSender.tsx:96-104

apps/web/src/components/QueuedMessageSender.tsx:96-104
🩺 Stability & Availability | 🟡 Minor | ⚡ Quick win

Recheck the automatic queue state after attachment uploads.

The base already had the asynchronous upload gap, but this PR adds queuesUntilTurnEnd and documents that Cursor automatic messages wait for the turn to end. The new guard runs only when QueuedMessageSender selects the message.

If the thread is ready at selection time and another client starts a Cursor turn during awaitAttachmentUploads, sendQueuedMessage still calls startTurn. Cursor treats that call as a steer, cancels the active turn, and replaces it. markDispatching checks only queue ownership.

Pass an automatic-dispatch flag to sendQueuedMessage. Immediately before dispatch, re-read the thread and rerun isQueuedMessageDue for automatic sends. If the message is no longer due, clear its preparing state and leave it queued. Keep the explicit Send now path unchanged.

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only still-valid issues, skip the rest with a brief reason, keep changes
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Review comment at @apps/web/src/components/QueuedMessageSender.tsx around lines
96 - 104:
Update QueuedMessageSender and sendQueuedMessage so automatic dispatches re-read
the thread after attachment uploads and recheck isQueuedMessageDue immediately
before starting the turn; if the message is no longer due, clear its preparing
state and leave it queued. Pass an automatic-dispatch flag to distinguish this
path, and keep the explicit Send now path unchanged.

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only still-valid issues, skip the rest with a brief reason, keep changes
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Outside diff comments:
Review comments at @apps/web/src/components/QueuedMessageSender.tsx:
- Around line 96-104: Update QueuedMessageSender and sendQueuedMessage so
automatic dispatches re-read the thread after attachment uploads and recheck
isQueuedMessageDue immediately before starting the turn; if the message is no
longer due, clear its preparing state and leave it queued. Pass an
automatic-dispatch flag to distinguish this path, and keep the explicit Send now
path unchanged.

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[mxdhavgautam]

@coderabbitai on the outside-diff note about re-checking the queue after attachment uploads: this is a real gap, but I'm leaving it out of this PR. It needs a second client to start a Cursor turn while a queued message is uploading, and the same gap already exists for every provider. A re-check before dispatch would narrow it but not close it, because the command can still land mid-turn in transit. Closing it properly takes a queued-send flag on thread.turn.start so the server can decide. That's a contract change of its own, which is why the PR lists it under "Not covered".

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@mxdhavgautam Thanks for clarifying. Keeping this pre-existing race outside #14586 is reasonable. A client-side re-check would reduce the race window but would not close it. The queued-send flag on thread.turn.start would let the server decide whether to dispatch or hold the message.

Would you like me to open a follow-up issue for that contract change?

---

✏️ Learnings added

Learnt from: mxdhavgautam
URL: https://github.com/pingdotgg/t3code/pull/14586

Timestamp: 2026-10-01T11:06:21.447Z
Learning: PR #14586 intentionally excludes the queued attachment-upload race, documented under "Not covered". This pre-existing gap affects every provider: another client can start a turn while a queued message uploads. A client-side queue re-check before dispatch only narrows the race because the command can arrive after another turn starts. The intended complete fix requires a queued-send flag on `thread.turn.start` so the server can decide whether to dispatch or hold the queued message.

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[juliusmarminge]

Note

This comment is posted by Julius' dot

The adapter tests and reported timings support the Cursor steering fix, but no before/after captures or recording show the changed Steer and Queue behavior in the client. Closing for missing interaction verification. Attach before/after captures and a short recording showing Steer interrupting the running task while Queue waits for the turn to finish, then request reconsideration. The regression report in #14585 remains useful.

[mxdhavgautam]

Added the interaction evidence requested above. Same dev build, Cursor Grok 4.7, follow-up sent while sleep 45 is running.

Before (main), Steer. Sent at 18.6s, answered at 64.1s, only after sleep 45 finished. The turn ran 1m 4s.

before-steer.mp4

After, Steer. Sent at 17.6s, answered at 20.8s while sleep 45 was still running. The turn ran 22s.

after-steer.mp4

After, Queue. The follow-up stays Queued through both commands, goes out after BOTH_DONE at 55.5s, and is answered at 59.0s.

after-queue.mp4

The branch is rebased onto main (263168d37). Requesting reconsideration.

[mxdhavgautam]

Note

🤖 Claude Opus 5.5 responding on behalf of Madhav

Superseded by Orchestrator v2 (#2829). The files this PR changed no longer exist on main; v2 now handles Cursor Steer with interrupt-and-restart in CommandPolicy.

Verified on main at 43bd66773 (nightly 0.0.46-nightly.20261003.2610 plus two unrelated web fixes), Cursor Grok 4.7 via @cursor/sdk, follow-up sent while sleep 45 was running:

• Steer: sent at 35.0s, the running attempt was superseded, answered at 39.7s.
• Queue: stayed Queued until the turn finished at 53.1s, then answered at 58.3s.

Leaving this closed. Thanks for the fix.