fix(mcp): keep missing repo_tree paths out of Sentry

[kentcdodds]

Intent

Stop routine repo_tree probes of missing subpaths from opening Sentry platform-bug issues.

Summary

• Agents often call repo_tree on common subpaths (docs/, tests/, .github/, …) that do not exist in the session workspace.
• Those calls threw raw workspace ENOENT errors, which MCP observability reported to Sentry as handled handler failures.
• repo_tree now maps missing-path ENOENT to McpCallerError with a clear path-not-found message, so they stay on mcp-event and out of Sentry (same pattern as fix(mcp): treat missing community listing as caller error #1318 / fix(mcp): stop Sentry noise for unpublished HEAD on repo_open_session #1059).
• Fixes https://sentry.io/organizations/kent-c-dodds-tech-llc/issues/7660643612/

Testing

• packages/worker/src/mcp/capabilities/repo/repo-tree.node.test.ts (ENOENT → McpCallerError; nested cause ENOENT; non-ENOENT still plain Error; happy-path summary)
• Prior Validate green on 5c391ba3 (Node/Workers/MCP/E2E/Static)
• CI green on latest commit

System recap — composes existing primitives (low risk)

Mode: recap · Base: main @ 969e1038 · Head: 39133459

Classification: composes — wires existing McpCallerError classification into the repo_tree missing-path path; no new primitives or schema changes.

Primitives touched

Primitive	Group	Impact
capability-registry	assistant	composes — repo_tree missing-path uses McpCallerError

System map

Missing session subpaths from repo_tree classify as caller-correctable MCP failures instead of Sentry platform bugs.

Legend: green = composes (wiring only) · amber = extended by this PR · red = new primitive · gray = context (unchanged, included only when an edge crosses it).

flowchart LR
	capabilityRegistry["capability-registry<br/>Capability registry"]:::touched
	mcpServer["mcp-server<br/>MCP endpoint"]:::untouched
	capabilityRegistry -->|"throw McpCallerError on missing tree path"| mcpServer
	classDef touched fill:#1a7f37,color:#fff
	classDef extended fill:#9a6700,color:#fff
	classDef added fill:#cf222e,color:#fff
	classDef untouched fill:#57606a,color:#fff

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Summary by CodeRabbit

• Bug Fixes

  • Improved repository tree error handling for missing paths, providing clearer error details.
  • Preserved existing behavior for other repository access failures.

• Tests

  • Added coverage for missing paths, unexpected errors, invalid requests, and repository subtree summaries.

[coderabbitai]

📝 Walkthrough

Walkthrough

The repository tree capability now converts missing paths to McpCallerError, preserves unrelated errors, and includes Vitest coverage for error handling, RPC arguments, and subtree summaries.

Changes

Repository tree errors

Layer / File(s)	Summary
Repository tree error mapping packages/worker/src/mcp/capabilities/repo/repo-tree.ts	The capability detects ENOENT across error cause chains and converts matching failures to McpCallerError. Other errors are rethrown unchanged.
Repository tree behavior coverage packages/worker/src/mcp/capabilities/repo/repo-tree.node.test.ts	Tests cover missing paths, RPC arguments, non-ENOENT failures, and subtree summary counts.

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

Possibly related PRs

• kentcdodds/kody#1038: Updates MCP capability errors to use McpCallerError.
• kentcdodds/kody#1059: Maps expected repository capability failures while preserving unrelated errors.
• kentcdodds/kody#1318: Converts missing-resource failures to McpCallerError and adds coverage.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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 MCP behavior change for missing repo_tree paths and its Sentry impact.
Description check	✅ Passed	The description includes the required Intent, Summary, and Testing sections, plus clear system impact and test coverage details.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch cursor/sentry-triage-kody-cloudflare-7660643612-3220

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@packages/worker/src/mcp/capabilities/repo/repo-tree.node.test.ts`:
- Around line 29-63: Add a test alongside “repo_tree maps missing-path ENOENT to
McpCallerError” where the mocked tree RPC rejects with an outer error whose
cause has code ENOENT. Invoke repoTreeCapability.handler with the same session
and path, then assert it returns McpCallerError with the existing missing-path
message and preserves the expected tree call arguments.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: ff03ae30-0b4a-41f2-81f0-31241ae2549d

📥 Commits

Reviewing files that changed from the base of the PR and between 969e103 and 5c391ba.

📒 Files selected for processing (2)

• packages/worker/src/mcp/capabilities/repo/repo-tree.node.test.ts
• packages/worker/src/mcp/capabilities/repo/repo-tree.ts

[github-actions]

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