fix(server): surface ACP stderr when cursor-agent exits at session start

[cestercian]

Summary

When cursor-agent acp rejects a project .cursor/cli.json and exits 1, T3 dropped the schema error and reported only ProviderAdapterSessionClosedError.

This keeps a redacted stderr tail on AcpProcessExitedError and maps process exits to ProviderAdapterProcessError whose detail is the excerpt (all ACP drivers). The excerpt from cursor-agent already names the rejected keys, so a separate cli.json key detector was dropped during review to keep this scoped to the reported bug.

Fixes #12451

Test plan

• vp test run — 66 passed (stderr sanitizer, mapper, runtime attach-on-exit, Cursor adapter with reporter’s unrecognized_keys payload)
• effect-acp client/protocol/stdio — 39 passed
• Manual: open a workspace with deprecated .cursor/cli.json keys and confirm the schema stderr is visible instead of a closed-session error

Summary by CodeRabbit

• Bug Fixes
  • Improved provider error messages by surfacing relevant process output, including configuration validation details.
  • Replaced generic closed-session errors with clearer process-failure information when an agent exits unexpectedly.
  • Preserved useful diagnostic context while limiting output and masking sensitive paths, URLs, and credentials.
  • Cursor configuration issues now identify affected files and unrecognized settings more clearly.
  • Process failures without diagnostic output now provide clearer exit-status information.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This cross-cutting ACP runtime change propagates subprocess stderr into structured, user-facing process errors across all ACP drivers, creating a sensitive diagnostic-data and redaction boundary. It also adds a static-analysis suppression and has unresolved concerns about credential exposure, so the change warrants human review.

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📒 Files selected for processing (1)

• apps/server/src/provider/acp/AcpStderr.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• apps/server/src/provider/acp/AcpStderr.ts

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📝 Walkthrough

Walkthrough

ACP process exits now retain sanitized stderr, map to ProviderAdapterProcessError, and preserve detailed failure text through orchestration. Tests cover stderr capture, secret redaction, error mapping, and Cursor startup failures.

Changes

Cursor ACP diagnostics

Layer / File(s)	Summary
Capture and format ACP stderr packages/effect-acp/src/errors.ts, apps/server/src/provider/acp/AcpStderr.ts, apps/server/src/provider/acp/AcpSessionRuntime.ts, apps/server/src/provider/acp/*test.ts	AcpProcessExitedError can include stderr. AcpSessionRuntime retains, sanitizes, and attaches a bounded stderr tail. Tests cover capture, redaction, and schema-error output.
Map ACP failures to provider errors apps/server/src/provider/acp/AcpAdapterSupport.ts, apps/server/src/provider/acp/AcpAdapterSupport.test.ts, apps/server/src/provider/Layers/CursorAdapter.test.ts	ACP process exits map to ProviderAdapterProcessError with process details. Cursor startup tests verify schema errors and offending keys are surfaced without closed-session wording.
Preserve process details in orchestration apps/server/src/orchestration/Layers/ProviderCommandReactor.ts	The command reactor returns ProviderAdapterProcessError.detail for process failures.

Priority: ⬆️ High

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: High

Sequence Diagram(s)

sequenceDiagram
  participant cursorAgent
  participant AcpSessionRuntime
  participant AcpAdapterSupport
  participant ProviderCommandReactor
  cursorAgent->>AcpSessionRuntime: write schema error to stderr and exit
  AcpSessionRuntime->>AcpSessionRuntime: retain and sanitize stderr
  AcpSessionRuntime-->>AcpAdapterSupport: return AcpProcessExitedError with stderr
  AcpAdapterSupport->>AcpAdapterSupport: map to ProviderAdapterProcessError
  AcpAdapterSupport-->>ProviderCommandReactor: return provider process error
  ProviderCommandReactor-->>ProviderCommandReactor: format process error detail

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Suggested reviewers: juliusmarminge

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	Issue #12451 requires startup stderr to reach the user. AcpSessionRuntime retains and sanitizes stderr, AcpProcessExitedError includes it, and mapAcpToAdapterError creates `ProviderAdapterProces…	Implement and test deprecated-key detection, destination mapping to .cursor/permissions.json and .cursor/sandbox.json, and a user-facing auto-migration prompt. Alternatively, split or update issue #12451 so the deferred migration requir…
Docstring Coverage	⚠️ Warning	Docstring coverage is 12.50% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 8 functions across 12 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: surfacing ACP stderr when cursor-agent exits during session startup.
Description check	✅ Passed	The description explains what changed, why it changed, the issue addressed, test coverage, and the remaining manual test. It uses different headings from the template and omits the non-applicable UI C…
Out of Scope Changes check	✅ Passed	The stderr retention, redaction, process-error mapping, failure formatting, and related tests directly support the stderr and actionable-error objectives in issue #12451. The shared ACP mapping suppor…

Full details: Linked Issues check

Explanation

Issue #12451 requires startup stderr to reach the user. AcpSessionRuntime retains and sanitizes stderr, AcpProcessExitedError includes it, and mapAcpToAdapterError creates ProviderAdapterProcessError with tests for the schema error. Issue #12451 also requires detection of deprecated approvalMode, autoRun, and sandbox keys, migration destinations, and an auto-migration prompt. The reviewed changes do not implement or test these behaviors.

Resolution

Implement and test deprecated-key detection, destination mapping to .cursor/permissions.json and .cursor/sandbox.json, and a user-facing auto-migration prompt. Alternatively, split or update issue #12451 so the deferred migration requirements are not part of this pull request.

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Actionable comments posted: 1

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🤖 Prompt to fix review comments

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only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
In `@apps/server/src/provider/acp/AcpStderr.ts`:
- Around line 31-34: Update the sanitizer in AcpStderr to redact sk-proj-style
secret tokens, Authorization: Basic credential values, and x-api-key values
before they reach AcpProcessExitedError details; preserve the existing pairing
URL, bearer token, and SECRET_TOKEN_PATTERN redaction, and add tests covering
each newly supported format.

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Reviewing files that changed from the base of the PR and between 8dd0247 and d8d2b6d.

📒 Files selected for processing (12)

• apps/server/src/orchestration/Layers/ProviderCommandReactor.ts
• apps/server/src/provider/Layers/CursorAdapter.test.ts
• apps/server/src/provider/Layers/CursorAdapter.ts
• apps/server/src/provider/acp/AcpAdapterSupport.test.ts
• apps/server/src/provider/acp/AcpAdapterSupport.ts
• apps/server/src/provider/acp/AcpJsonRpcConnection.test.ts
• apps/server/src/provider/acp/AcpSessionRuntime.ts
• apps/server/src/provider/acp/AcpStderr.test.ts
• apps/server/src/provider/acp/AcpStderr.ts
• apps/server/src/provider/acp/CursorCliConfig.test.ts
• apps/server/src/provider/acp/CursorCliConfig.ts
• packages/effect-acp/src/errors.ts

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Actionable comments posted: 1

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Inline comments:
In `@apps/server/src/provider/acp/AcpStderr.ts`:
- Line 38: Update the ACP stderr sanitization at the redaction chain in
AcpStderr so quoted JSON credential fields such as token, authToken, and apiKey
have their values replaced before stderr is retained, while preserving the
existing SECRET_TOKEN_PATTERN redaction.

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📒 Files selected for processing (5)

• apps/server/src/provider/Layers/CursorAdapter.ts
• apps/server/src/provider/acp/AcpStderr.test.ts
• apps/server/src/provider/acp/AcpStderr.ts
• apps/server/src/provider/acp/CursorCliConfig.test.ts
• apps/server/src/provider/acp/CursorCliConfig.ts

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[juliusmarminge]

Pushed two changes on top of your branch (thanks for maintainerCanModify): dropped CursorCliConfig.ts and its test, and removed formatAcpProcessExitDetail in favour of AcpProcessExitedError.message, which already formats the same string. The stderr excerpt from cursor-agent names the rejected keys, so the detector was adding a hard-coded copy of Cursor's moving schema to solve something the excerpt already solves. Core fix is unchanged and is the right one.

[juliusmarminge]

/recheck-vouch

[macroscopeapp]

Additional Effect service convention finding in apps/server/src/provider/acp/AcpAdapterSupport.ts:27: the translation copies AcpProcessExitedError.message, including child stderr, into ProviderAdapterProcessError.detail. Keep the source error as cause, map only normalized exit attributes into the adapter error, and route intentionally displayed diagnostics through a separate controlled channel.

Suggested fix: No single-hunk fix is safe because the adapter error schema and diagnostic delivery path must change together.

^{Posted via Macroscope — Effect Service Conventions}

[macroscopeapp]

Correction: the AcpAdapterSupport.ts:27 finding is part of the same raw-stderr error-model issue already reported inline on packages/effect-acp/src/errors.ts; it is not an additional independent finding.

^{Posted via Macroscope — Effect Service Conventions}