fix(pi): queue turn-start prompts when native work is running

[StiensWout]

Pi can resume extension work before T3 receives its native wake event. The next user prompt then fails with "Agent is already processing", leaving the turn failed.

Always send turn-start prompts with streamingBehavior: "steer", so Pi atomically queues them during an active run or starts a new run when idle. Add coverage for resumed idle and streaming sessions before wake events arrive, and update Pi replay expectations.

Closes #15221.

Verified with 97 targeted adapter and Pi orchestration replay tests, provider package typecheck, targeted lint, and formatting. A live Pi 1.1.0 RPC probe against an isolated local model endpoint confirmed bare-prompt rejection during streaming, queued steer prompts, and normal idle starts.

_{Prepared for Wout by gpt-6.1-sol in T3 Code through the Codex harness.}

[macroscopeapp]

Approvability

Verdict: Approved at 137ad3a

Macroscope's review found this PR approvable — This is a narrowly scoped Pi adapter bug fix that atomically queues turn-start prompts during active native work while preserving idle execution. It includes targeted coverage for both streaming and idle states; the other changes only update replay expectations.

Notes:

• Diff unchanged. Approvability was decided on eligibility alone.

^{You can add or adjust custom eligibility rules. Learn more.}

Dismissing prior approval to re-evaluate 137ad3a

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Path: .coderabbit.config.ts
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• Run ID: 9e290b39-4055-4c5f-ac25-45215f32505a

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📥 Commits

Reviewing files that changed from the base of the PR and between 5753207 and 137ad3a.

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📒 Files selected for processing (11)

• apps/server/src/orchestration-v2/testkit/fixtures/message_steering/pi_output.ts
• apps/server/src/orchestration-v2/testkit/fixtures/message_steering/pi_transcript.ndjson
• apps/server/src/orchestration-v2/testkit/fixtures/multi_turn/pi_transcript.ndjson
• apps/server/src/orchestration-v2/testkit/fixtures/pi_compaction/pi_transcript.ndjson
• apps/server/src/orchestration-v2/testkit/fixtures/provider_thread_resume/pi_transcript.ndjson
• apps/server/src/orchestration-v2/testkit/fixtures/simple/pi_transcript.ndjson
• apps/server/src/orchestration-v2/testkit/fixtures/thread_rollback/pi_transcript.ndjson
• apps/server/src/orchestration-v2/testkit/fixtures/thread_rollback_after_stop/pi_transcript.ndjson
• apps/server/src/orchestration-v2/testkit/fixtures/turn_interrupt_mid_tool/pi_transcript.ndjson
• packages/provider-pi/src/server/adapter.test.ts
• packages/provider-pi/src/server/adapter.ts

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📝 Walkthrough

Walkthrough

The Pi adapter now sends non-compact turn-start prompts with streamingBehavior: "steer". Adapter tests cover streaming and idle Pi states, and orchestration replay fixtures expect the added field.

Changes

Pi prompt steering

Layer / File(s)	Summary
Turn-start prompt contract and coverage packages/provider-pi/src/server/adapter.ts, packages/provider-pi/src/server/adapter.test.ts, apps/server/src/orchestration-v2/testkit/fixtures/*/pi_output.ts, apps/server/src/orchestration-v2/testkit/fixtures/*/pi_transcript.ndjson	startTurn now includes streamingBehavior: "steer" on non-compact prompts. The adapter test fake can report streaming state and the tests cover resumed turns when Pi is streaming or idle. Replay fixture expectations now include the steer field.

Priority: ➖ Normal

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

Change: Bug fix · Severity of issue fixed: Medium

Possibly related PRs

• pingdotgg/t3code#15444: Adds the same steer streaming behavior to Pi turn-start prompts and tests the “Agent is already processing” case.

Suggested reviewers: juliusmarminge

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Merge Risk | ⚪ Minimal · up to 137ad

Merge Risk: ⚪ Minimal · up to 137ad

Turn-start prompts now request steer behavior, including when Pi is already streaming. No actionable merge risk remains beyond normal checks.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 137ad

The change uses an existing queuing mode and does not demonstrate increased access or privileges. Some cancellation and completion edge cases remain unverified.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The changed reachability is admission of user text and images into an already-running, bound native session instead of rejection. Any resulting activity uses that session's existing authority; the production diff does not grant additional credentials, tools, or process privileges. This is not evidence of tenant or host isolation.

Trust Boundaries and Controls

• observed — The existing transport separates correlated request responses from asynchronous session events. Turn-start prompt acknowledgements are handled as deferred events and matched against the pending provider-turn identity. The PR changes busy-session admission, not this identity handling.

Resilience and Maintainability Implications

• observed — Normal settlement checks streaming, compaction, pending-message count, turn identity, and probe generation before finalizing. User Stop requests runtime restart and reaches process termination; ordinary interruption can instead use native abort. Native queue cleanup under that soft-abort path remains unverified.

Hardening Proposals

• proposed — Validate the queue lifecycle against supported native versions: delay acknowledgement during a no-wake start, interrupt before queued consumption, and repeat or recover the turn. Establish that cancelled input cannot execute later and that completion cannot precede pending command expansion.

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Pre-merge checks | 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check		The title clearly summarizes the primary fix: queueing Pi turn-start prompts while native work is running. It is concise and specific.
Description check		The description explains the problem, the implementation, the linked issue, and focused verification results. It does not use the template headings, but it includes the required information and is suf…
Linked Issues check		The PR addresses active issue #15221. In packages/provider-pi/src/server/adapter.ts, every non-compact turn-start prompt now sends streamingBehavior: "steer". This lets Pi queue the prompt during …
Out of Scope Changes check		The changes remain within #15221. The adapter change fixes the Pi prompt contract. The fake Pi behavior, targeted race test, and replay expectation updates support and verify that contract. No unrelat…

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✨ Finishing Touches

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