fix(mount): fall back when GitHub tree cursor stalls

[khaliqgant]

Summary

• Reject a non-advancing or cyclic cursor in the GitHub working-tree verification snapshot.
• Reuse the existing typed malformed-pagination error instead of spinning until the reconcile deadline.
• Fall back to the bounded resumable directory traversal, which completes repository bootstrap when the recursive snapshot feed stalls.

Production diagnosis

The failed Agent37 zero-config mount authenticated successfully: all 34 Relayfile responses in the mount window were HTTP 200. The GitHub contents tree then received the same non-empty cursor three times before the one-shot mount exited. The snapshot loop was the only mount pagination loop without a repeated-cursor guard.

Validation

• go test ./internal/mountsync -count=1
• Focused regression proves the snapshot stops after two requests, bounded tree fallback runs, bootstrap completes, and the repository file is materialized.
• git diff --check

No API contract, server route, dependency, credential, or provider mutation changes.

---

Note

Medium Risk
Changes GitHub bootstrap pagination behavior; incorrect guards could block mounts or skip tar seed when the server is healthy.

Overview
GitHub working-tree snapshot pagination now fails closed when ListTree returns a non-empty next cursor that does not advance or repeats a cursor already seen, using the existing MalformedPaginationError / ErrMalformedPagination path (feed label github working-tree). That stops the verification snapshot from spinning until reconcile expires—the gap other paginated feeds already guarded against.

When the tar-seed path hits this error, bootstrap continues via the existing bounded resumable tree pull instead of starting tar export after a broken snapshot.

Comments are generalized from “events” to any paginated feed. Tests cover direct snapshot rejection after two identical cursors and a full Reconcile that completes bootstrap and materializes files without calling tar export.

^{Reviewed by Cursor Bugbot for commit 49fd1c2. Bugbot is set up for automated code reviews on this repo. Configure here.}

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-19T17:31:42.450438Z	49fd1c2	PR opened

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: d8405920-7d42-49a0-b988-0a79d865d8b5

📥 Commits

Reviewing files that changed from the base of the PR and between 66a80c8 and 49fd1c2.

📒 Files selected for processing (2)

• internal/mountsync/syncer.go
• internal/mountsync/syncer_test.go

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The GitHub working-tree snapshot now detects repeated pagination cursors and returns a malformed-pagination error. Tests verify the error details and confirm that reconciliation falls back to bounded tree traversal.

Changes

GitHub pagination validation

Layer / File(s)	Summary
Cursor repeat validation internal/mountsync/syncer.go	githubWorkingTreeSnapshot records page-start cursors and rejects repeated or self-referencing NextCursor values with MalformedPaginationError. Error comments now use general pagination wording.
Pagination failure tests internal/mountsync/syncer_test.go	Tests verify repeated-cursor error fields, requested cursors, and reconciliation fallback to bounded tree traversal without tar export.

Priority: ⬇️ Low

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

Change: Bug fix

Suggested reviewers: miyaontherelay

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 2 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 identifies the main change: fallback behavior when the GitHub tree cursor stalls.
Description check	✅ Passed	The description directly explains the cursor validation, malformed-pagination error, fallback traversal, production diagnosis, and validation performed.
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.

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✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

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🧪 Generate unit tests (beta)

• Commit to this branch
• Create a new PR

---

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_{A rabbit checks each cursor’s trail
No looping hop can now prevail
The snapshot stops with errors clear
Bounded trees bring bootstrap near
README blooms where paths appear}

_{Comment @coderabbitai help to get the list of available commands.}

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

[github-actions]

Relayfile Eval Review

Run: .relayfile/evals/runs/2026-09-19T17-32-27-988Z-HEAD-provider
Mode: provider
Git SHA: 5c83354

Passed: 4 | Needs human: 0 | Reviewable: 0 | Missing output: 0 | Failed: 0 | Skipped: 0

Human Review Cases

No reviewable human-review cases captured Relayfile output.