[ci-doctor] CI Test Failure — Run #29057896142 (bun-version: latest regression)

[github-actions]

Summary

The Test & Lint job failed at the Test step (bun test --coverage ./tests/) on commit 7c5ea995, which merged PR #410 ("Improve Evergreen CI diagnostics"). Only workflow files were changed — no source or test code was modified.

Failure Details

• Run: 29057896142
• Commit: 7c5ea995df0694314856f08440316b53004183d9
• Trigger: push (merge of PR Improve Evergreen CI diagnostics #410)
• Failed Step: bun test --coverage ./tests/ (ran for ~4 seconds)
• Previous successful run: 29052744071 on commit a7269d37

Root Cause Analysis

No source code or test files were changed between the successful and failing runs — only workflow files (.github/workflows/evergreen.lock.yml, .github/workflows/evergreen.md, .github/workflows/shared/evergreen/repo-policy.md).

The most likely cause is that bun-version: latest in ci.yml pulled a new bun version between the two runs, which introduced a regression in the test runner or coverage reporting.

This is a recurring pattern — an identical failure occurred previously (see #307).

Failed Jobs and Errors

Job	Step	Result
Test & Lint	Test	❌ failure
Test & Lint	Type check	✅ success
Test & Lint	Lint	✅ success

CI logs are not publicly accessible (require admin), so the exact test failure message is unavailable.

Investigation Findings

1. Only .github/workflows/ files changed — code is unchanged
2. The Test step ran for ~4 seconds (23:38:38–23:38:42), which is abnormally short for a full test suite
3. Build and cross-validation steps were skipped (they depend on test passing)
4. This is at least the third occurrence of this pattern (see also [ci-doctor] CI Test Failure — Run #25838576963 (merge of autoloop PR #302) #307)

Recommended Actions

• Pin bun version in .github/workflows/ci.yml: change bun-version: latest → bun-version: "1.2.x" (or the last known-good version)
• Retry the failed run — a re-run may succeed if the issue is a transient bun release
• Check bun release notes for any test runner or coverage changes between the last successful and current bun version

Prevention Strategies

1. Pin bun to a specific version in all CI workflows; update deliberately after reviewing release notes
2. Consider adding a continue-on-error: false with explicit bun version check
3. Add a note to AGENTS.md reminding agents that bun-version: latest is not allowed in CI

AI Team Self-Improvement

## CI Stability: Bun Version Pinning (CRITICAL)
- NEVER use `bun-version: latest` in CI workflow files (.github/workflows/*.yml).
  Always pin to a specific version, e.g. `bun-version: "1.2.15"`.
- When modifying any CI workflow, verify that `bun-version` is pinned and not set to `latest`.
- Recurring test failures where only workflow files changed are almost always caused by
  bun-version: latest pulling a new release with a regression. Recommend pinning immediately.

Historical Context

• Issue [ci-doctor] CI Test Failure — Run #25838576963 (merge of autoloop PR #302) #307 (May 2026): Same pattern — bun test CI failure after autoloop merge, only workflow or unrelated files changed, tests pass locally. Root cause identified as bun-version: latest.
• This is the third known occurrence of this pattern in this repository.

Generated by CI Failure Doctor · 326.4 AIC · ⌖ 11 AIC · ⊞ 28.1K · ◷

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