fix(server): Claude threads no longer get stuck after background commands

[eimexdev]

Problem

A Claude thread started through MCP or mobile can omit fastMode, then receive an ordinary web/desktop follow-up with fastMode: false. With a native background command still running, those equivalent Normal selections produce different query identities and the follow-up is refused. Stop then rejects the failed run because it has no provider turn, and fresh-session recovery can resume a newly allocated native ID using the provider thread's old turn ordinal.

Change

• Normalize omitted fast mode to Normal at the Claude provider boundary. The protection against real model/settings changes killing background work stays intact.
• When the newest failed run has background work but no provider turn, route Stop through its provider thread's latest turn.
• Pass accepted-turn history for the current native ID through the existing turn-start services. Claude creates a fresh native ID and resumes an existing one, retaining compatibility with legacy attempts and callers without the new internal hint.

Five additive regression cases use existing adapter and orchestration test helpers. Existing assertions remain intact. No client, wire-contract, database migration, or documentation changes.

Scope and approval

This addresses the observed Claude background-command failure and its Stop and fresh-session recovery paths: #15471, #15472, and #15103. Maintainer triage confirms the Normal-selection mismatch and the fresh-session resume defect.

The corrections overlap the open proposals #15473, #15474, and #15318. The native-history approach and fallback regression were adapted from #15318. This PR presents the local fix for the captured failure chain; maintainers can choose the existing proposals when resolving that overlap.

Verification

Before the behavioral changes, all five added cases failed with the expected selection refusal, non-interruptible run, or incorrect native-session history. The existing Stop case passed.

vp test run apps/server/src/claudeModelOptions.test.ts apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts apps/server/src/orchestration-v2/BackgroundWorkStop.integration.test.ts apps/server/src/orchestration-v2/testkit/ProviderSwitch.integration.test.ts --maxWorkers=1

After the fix, 203 cases passed and two existing handoff cases timed out. Both timed-out cases passed unchanged in isolation:

vp test run apps/server/src/orchestration-v2/testkit/ProviderSwitch.integration.test.ts --maxWorkers=1 -t 'preserves handoffs through prior-images-reasoning-change-retry-native|preserves handoffs through prior-images-native$'
vp exec tsc --noEmit -p apps/server/tsconfig.json

Server typecheck passed. Targeted vp lint and vp fmt --check on the nine changed files passed; lint retained two pre-existing unused-variable warnings. git diff --check passed. New tests synchronize with frame receipts, persisted events, and effect-worker drains.

Validation used synthetic SDK frames and isolated orchestration state. No live Claude resumed-turn execution or repair of already-broken sessions was verified. No live provider transcripts, installed runtime, active threads/processes, or live T3 database were touched. No browsers, dev servers, or repo-wide checks were used.

Model and harness: GPT-6.1-sol, HIGH reasoning, Codex in T3 Code.

closes

• closes [Bug]: Claude refuses every message as a "model or setting change" when a thread moves between mobile and web while background work runs #15471.
• closes [Bug]: Stop can't end background work after a run fails before its provider starts ("Run … is not interruptible") #15472.
• closes fix(claude): a thread with background work no longer refuses messages sent from another client #15473 (superseded by this implementation).
• closes fix(server): Stop reaches background work after a run fails before its provider starts #15474 (superseded by this implementation).
• closes fix(server): fresh claude sessions no longer resume a missing id #15318 (native-session recovery fix incorporated here).

partially addresses #15103: this fixes opening a newly allocated native session with resume. rejected starts can still leave pending handoff deliveries that unnecessarily force a fresh session, so that issue remains open for the second fix requested in maintainer triage.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — The PR changes the effective Claude fastMode default and also alters provider-session resume and Stop behavior across existing server request paths. These are production behavior changes with cross-cutting orchestration effects, so the change warrants human review.

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📝 Walkthrough

Walkthrough

The orchestration path now tracks whether a native provider thread has accepted turns and passes that state to Claude resumption logic. Interrupt dispatch can fall back to the latest provider-thread turn when the active attempt has no matching turn. Unset Claude fast mode defaults to false.

Changes

Orchestration and Claude sessions

Layer / File(s)	Summary
Native-thread history propagation apps/server/src/orchestration-v2/ProviderAdapter.ts, apps/server/src/orchestration-v2/ProviderTurnStartService.ts, apps/server/src/orchestration-v2/RunExecutionService.ts, apps/server/src/orchestration-v2/testkit/ProviderSwitch.integration.test.ts	The start-root-run path derives and forwards nativeThreadHasTurns when its value is known. The provider-switch integration test captures the value and checks fallback session behavior.
Claude session and query behavior apps/server/src/claudeModelOptions.ts, apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts, apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts	Claude resumption logic uses the supplied native-thread history flag, or falls back to the provider-turn ordinal when the flag is unknown. Unset fastMode defaults to false. Tests cover fresh sessions and query replacement during background work.
Background-work interrupt fallback apps/server/src/orchestration-v2/Orchestrator.ts, apps/server/src/orchestration-v2/BackgroundWorkStop.integration.test.ts	Interrupt dispatch falls back to the latest provider-thread turn when background work exists and no turn matches the active attempt. Integration tests cover Stop when the newest run fails before provider start and when it completes normally.

Priority: ➖ Normal

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

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant ProviderTurnStartService
  participant RunExecutionService
  participant ClaudeAdapterV2
  ProviderTurnStartService->>RunExecutionService: pass nativeThreadHasTurns when known
  RunExecutionService->>ClaudeAdapterV2: forward nativeThreadHasTurns when defined
  ClaudeAdapterV2->>ClaudeAdapterV2: use supplied history flag for resumption decision

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Suggested reviewers: juliusmarminge, t3dotgg

Merge Risk: 🔵 Low · up to d3e74

Defaulting Claude fast mode to Normal could discard SDK settings passed as a string for fast-mode-capable models. The scenario is narrow and the fix is small, so this can be addressed before or shortly after merge.

Security Architecture Review

Security architecture risk: 🔵 Low · up to d3e74

The change improves recovery and Stop behavior without a demonstrated expansion of access or privileges. Remaining uncertainty concerns live execution and recovery behavior rather than a confirmed security weakness.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The changed interruption routing can affect background commands and subagents across provider threads within the selected application thread. Session resumption uses the selected native identity; the history hint does not supply a replacement target or additional tool privileges. Reachable external assets still depend on existing execution policy, which was not exhaustively audited.

Trust Boundaries and Controls

• observed — In the inspected production path, accepted-history state originates from orchestration records rather than message content. Stop's fallback remains provider-thread-scoped, and the live-session interruption path still enforces the existing interrupt capability policy. These controls are counterevidence to a newly introduced caller-authority bypass.

Resilience and Maintainability Implications

• observed — Interruption is followed by effect-keyed settlement. Cleanup respects run-ordinal bounds and leaves other live provider processes responsible for their own work. Regression assertions cover failed-start Stop routing and fresh-native creation followed by same-native resumption; they do not establish live-provider delivery.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 20.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 9 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly identifies the server fix for Claude threads that become stuck after background commands.
Description check	✅ Passed	The description covers the problem, change, scope and approval context, and focused verification results. It also identifies limitations in live-provider testing and remaining work.

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Inline comments:
Review comments at @apps/server/src/claudeModelOptions.ts:
- Line 40: Update the fastMode defaulting around
getModelSelectionBooleanOptionValue so an omitted fastMode still uses the Normal
default without causing makeClaudeQueryOptions to replace caller-supplied string
sdkSettings with an object; preserve those settings when compiling the
selection.

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📥 Commits

Reviewing files that changed from the base of the PR and between b438198 and d3e74c9.

📒 Files selected for processing (9)

• apps/server/src/claudeModelOptions.ts
• apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts
• apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts
• apps/server/src/orchestration-v2/BackgroundWorkStop.integration.test.ts
• apps/server/src/orchestration-v2/Orchestrator.ts
• apps/server/src/orchestration-v2/ProviderAdapter.ts
• apps/server/src/orchestration-v2/ProviderTurnStartService.ts
• apps/server/src/orchestration-v2/RunExecutionService.ts
• apps/server/src/orchestration-v2/testkit/ProviderSwitch.integration.test.ts

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