feat: implement issue #678 — [Phase 1] Graceful degradation: warn (never fake) when an MCP server is unavailable

[don-petry]

Closes #678

Implemented by dev-lead agent. Please review.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 53167164-46b6-4aa9-b321-7312230516f6

📥 Commits

Reviewing files that changed from the base of the PR and between 3ff67db and 3f75216.

📒 Files selected for processing (2)

• scripts/engine.sh
• tests/dev-lead/unit/test_engine_mcp.bats

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch dev-lead/issue-678-20260614-1430

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[don-petry]

Dev-Lead — review-changes (no-changes)

No changes were needed for this PR.

[gemini-code-assist]

Code Review

This pull request implements graceful degradation for MCP server connection and initialization failures by scanning CLI output files and emitting a warning without altering the final exit code. It also adds comprehensive unit tests to verify this behavior. A critical issue was identified in the server name extraction pipeline, where a grep failure could trigger 'set -e' and prematurely terminate the script; appending '|| true' to the pipeline is recommended to prevent this.

[don-petry]

Dev-Lead — fix-reviews (applied)

Changes committed and pushed.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[don-petry]

Dev-Lead — review-changes (no-changes)

No changes were needed for this PR.

[donpetry-bot]

Automated review — APPROVED ✓

Risk: LOW
Reviewed commit: 3f752165d8f38c986caa8e3f356e58c8e0d13140
Review mode: triage-approved (single reviewer)

Summary

Adds warn-and-continue graceful degradation for MCP server connection/init failures in scripts/engine.sh (issue #678), plus 5 bats tests. The new _emit_mcp_failure_warning helper scans captured CLI output and emits a ::warning:: naming the affected server(s) without ever altering final_rc — so the review completes on the model's base capabilities rather than fatal-exiting or faking an all-clear. +117/-0 across 2 files; logic is isolated and control-flow-neutral.

Linked issue analysis

Closes #678. All four acceptance criteria are substantively met: AC#1 (::warning:: names the failed server and review continues), AC#2 (no fatal exit, no fabricated/empty verdict — final_rc untouched), AC#3 (inert when REVIEW_MCP_CONFIG knob is unset), AC#4 (synthetic failure transcripts asserted in tests). Implementation stays confined to engine.sh + a bats file as the issue specified, and the failure regex is deliberately kept clear of rate-limit vocabulary to avoid misclassification into cross-engine fallback, per the issue's dev notes.

Findings

No blocking findings. Prior gemini-code-assist review on the first commit (1ba4da2) flagged a set -e risk: a grep pipeline failure could prematurely terminate the script. Verified resolved in the fix commit (3f75216), which appended '|| true' to the server-name extraction pipeline; the detection grep is also guarded with '|| return 0'. coderabbit review was dismissed (rate-limited). No unresolved human review threads or unanswered questions. Warn-only feature with no control-flow impact and good test coverage (agentic + duck paths, knob-set/unset, named/unnamed server).

CI status

All required checks green. shellcheck, bats, unit-tests, CodeQL (actions + python), SonarCloud (Quality Gate passed), gitleaks secret scan, AgentShield, and dev-lead test suite all SUCCESS; dependency-audit ecosystem sub-jobs and dependabot SKIPPED as expected. mergeStateStatus is BLOCKED only because org-leads review is still required (REVIEW_REQUIRED), not due to any failing check.

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