fix(ci): close remaining uv sync diagnostic gaps (#8249)

[ll7]

Summary

This successor closes the remaining boundedness gap in the CI ci_uv_sync_diag probe. It removes
the unbounded uv cache size traversal and makes both advisory du probes deadline-aware and
diagnostically explicit.

Linked Issues

• Relates to friction: stabilize ci_uv_sync_diag timeout under shared-host load #8249 (successor follow-up to merged PR fix(ci): bound uv-sync-diag du probes under shared-host load (#8249) #8365; the issue is reopened for this work).

Stack / Dependency

• Base dependency: none.
• Required prior PRs and stack follow-up issues: none.
• Safe to review independently: yes; the branch is based on current main.

What Changed

• Removed the redundant uv cache size cache-root traversal.
• Require a positive ROBOT_SF_DIAG_DU_TIMEOUT_SECONDS value, defaulting invalid values (including
  zero) to 10 seconds.
• Detect GNU timeout(1) explicitly and use --kill-after=2s after the configured deadline.
• Emit ok, timed-out, or error sizing status markers and exit codes for cache and virtualenv
  probes.
• Added deterministic tests for the unbounded-uv regression, zero timeout, hard timeout timing,
  non-timeout errors, no-GNU fallback behavior, and the script contract.

Why It Matters

The diagnostic remains advisory and exits zero, while its expensive cache and virtual-environment
walks no longer hide failures or consume the full readiness test budget. Hosts without GNU
timeout(1) retain the prior direct-du fallback and ordinary output keys.

Research / Evidence Notes

Not applicable — this is a CI/tooling reliability change with no research, benchmark, metric, or
paper-facing claim.

Validation / Proof

• tests/dev/test_ci_uv_sync_diag.py: 12 passed.
• tests/test_ci_script_contract.py: 153 passed.
• bash -n scripts/dev/ci_uv_sync_diag.sh: passed.
• Ruff check and format checks for both changed Python test files: passed.
• BASE_REF=origin/main PR_READY_MODE=final ... scripts/dev/pr_ready_check.sh: passed on
  committed head 8e7015c578279c1d4e1dd31279b0143bf9161eec against base
  5f476625eba9c4ae2fa5770781852b78c865fd8b.

Risks / Rollback

The no-GNU fallback remains intentionally unbounded for compatibility with stock macOS-style
hosts. Revert commit 8e7015c57 to restore the preceding diagnostic implementation if needed.

Docs / Provenance

No durable benchmark or model artifacts were produced. Readiness receipts remain worktree-local
ignored output; the source contract and reproducible test fixtures are tracked in this PR.

Downstream Propagation

Not applicable — support/tooling change; no benchmark, metric, model, claim-map, registry, or
durable evidence update is required.

Follow-Up / Residual Scope

No deferred work remains for this implementation slice. Issue #8249 is reopened for this PR; this
is the immediate successor requested for the remaining uv sync diagnostic gaps.

Reviewer Notes

• Verify that uv cache size is absent from the executable path and that the later bounded du
  remains the sole cache-size traversal.
• Verify that timeout expirations are not attributed to host contention without evidence and that
  non-timeout tool failures remain visible.

[coderabbitai]

Important

• 🔍 Trigger review

This repository does not receive automatic reviews because it has fewer than 10 stars.

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Team

Run ID: 81b0cd43-453b-41f9-aeda-41513bbad9fd

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

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

[github-actions]

🔍 PR Contract Check Summary

Overall Status: 🟢 PASSED

Check	Status	Description
1. Closes-discipline	✅ PASSED	Demand Refs #N for epic issues
2. Closure declaration	⚠️ WARNING	Require Closes/Refs for title issues
3. State-refresh-only	✅ PASSED	Reject docs/context state updates
4. Evidence hygiene	✅ PASSED	Checks markers and provenance fields
5. Evidence writer usage	✅ PASSED	Require the shared marked writer path
6. Successor discipline	⚠️ WARNING	Require successor statement on multi-PR issues
7. Worker-lane label	⚪ None	Label PRs from cheap worker lane
8. Placeholder docstring ratchet	✅ PASSED	Reject NEW TODO/empty docstrings in added diff lines

⚠️ Warnings

• WARN: PR title references issue friction: stabilize ci_uv_sync_diag timeout under shared-host load #8249, but the PR body lacks a closure declaration (e.g., 'Closes friction: stabilize ci_uv_sync_diag timeout under shared-host load #8249' or 'Refs friction: stabilize ci_uv_sync_diag timeout under shared-host load #8249').
• WARN: Issue friction: stabilize ci_uv_sync_diag timeout under shared-host load #8249 has already been referenced in 3 merged PR(s), but the PR body does not contain a successor statement ('successor slice' or 'does not duplicate').

ℹ️ Info

• No worker-lane provenance detected.

---

This check is mechanized. Please resolve any blockers to pass CI.

[ll7]

Exact-head implementation review

Reviewed PR #8446 at exact head 8e7015c578279c1d4e1dd31279b0143bf9161eec against
origin/main 5f476625eba9c4ae2fa5770781852b78c865fd8b.

Scope and design

This is a support/tooling-only successor for #8249. It removes the unbounded uv cache size
probe, bounds GNU du calls with an explicit positive timeout and kill-after grace period, keeps
the direct-du fallback for hosts without GNU timeout, and exposes timeout/error markers while
preserving advisory zero-exit behavior. It makes no research, benchmark, model, metric, or
paper-facing claim.

Validation

• pytest -q tests/dev/test_ci_uv_sync_diag.py tests/test_ci_script_contract.py — 165 passed.
• Ruff 0.16.5 check/format, bash -n scripts/dev/ci_uv_sync_diag.sh,
  git diff --check, and clean git merge-tree --write-tree origin/main HEAD — passed.
• Hosted status is not yet terminal: smoke-artifacts and changed-coverage-gate remain in
  progress, so no hosted success is inferred.

Findings and disposition

No actionable P0–P3 implementation finding was identified. The timeout detection, GNU capability
check, non-timeout error reporting, compatibility fallback, and no-uv cache size contract are
covered by the focused tests. The PR is current-base, non-draft, and has no domain or evidence
hold in its declared contract; final admission still requires terminal hosted checks and the
repository’s guarded merge receipt.

Decision: accept the implementation slice provisionally, subject to exact-head hosted checks and
the canonical receipt. No source repair is required.

gate-verdict: accepted @ 8e7015c
pr-metadata: reconciled @ 4f7a712bc6fa0d761e1bcfcc6053a318b46e3b39658b8951284e208764e9b345

[ll7]

Exact-head implementation review

Reviewed PR #8446 at exact head 8e7015c578279c1d4e1dd31279b0143bf9161eec against
origin/main 5f476625eba9c4ae2fa5770781852b78c865fd8b.

This is a support/tooling-only successor for #8249. It removes the unbounded uv cache size
probe, bounds GNU du calls with an explicit positive timeout and kill-after grace period, keeps
the direct-du fallback for hosts without GNU timeout, and exposes timeout/error markers while
preserving advisory zero-exit behavior. It makes no research, benchmark, model, metric, or
paper-facing claim.

The focused proof passed: 165 passed across the changed diagnostic and script-contract tests;
Ruff 0.16.5, formatting, shell syntax, diff, and merge-tree checks passed. Hosted CI is now
terminal for this exact head with 32 success and 1 skipped checks. No actionable P0–P3
implementation finding was identified, and no domain, scientific-evidence, legal, security, or
dependency hold is declared. The implementation is accepted for the guarded merge path, subject
to the repository’s exact-head merge receipt and merge-queue gate.

Decision: accept this tooling slice. No source repair is required.

gate-verdict: accepted @ 8e7015c
pr-metadata: reconciled @ b546fe9f1c49ed8eae046bcfffa581cbf3935f64751e8f7fa2699ba138c56b4d