Analyze CI Failures

vcpkg CI Failures Analyzer

Overview

Consumes already-collected CI evidence, cross-references it with baselines, and produces a regression report. If evidence has not yet been collected, invoke fetch-vcpkg-ci-logs first, then return to this workflow. Do not duplicate its acquisition steps here.

MCP Tools

Prerequisites

• Local failed step logs and relevant extracted failure-log artifacts.
• Build metadata and full Azure build URL.
• For PR builds, PR metadata and full PR URL.

Evidence Acquisition

When the required evidence is not already local, delegate acquisition to a subagent using fetch-vcpkg-ci-logs. Prefer a fast, low-cost model for this mechanical work. Ask the subagent to return only the evidence inventory and local paths; keep regression analysis and report generation in the main agent.

When the evidence is already available locally, proceed directly to analysis.

Workflow

OUTPUT RULE: This skill applies only when the user asked for triage or report output, so a report.md is always required once it is selected. Write it as soon as step-log analysis completes, then enhance it from artifacts. Your response MUST also contain the complete report content — not a summary.

URL RULE: Your response text (not just the report file) MUST include:

• For scheduled/manual builds: the full Azure DevOps URL https://dev.azure.com/vcpkg/public/_build/results?buildId={buildId}
• For PR builds: both the full PR URL https://github.com/microsoft/vcpkg/pull/{prNumber} AND the Azure DevOps build URL

Before analysis, read .\.github\skills\shared\azure-vcpkg-ci-notes.md.

Phase 1: Analyze failed step logs

1. Inventory evidence — Confirm the build metadata, failed step-log paths, artifact paths, and triplets available from the acquisition step.

2. Scan step logs — Extract every REGRESSION: line and retain exact failure type keywords: BUILD_FAILED, FILE_CONFLICTS, POST_BUILD_CHECKS_FAILED, and CASCADED_DUE_TO_MISSING_DEPENDENCIES. Capture 2-3 surrounding lines for context.

3. PR feature-test logs — PR builds may not have REGRESSION: lines. Instead scan for FAIL:, failed with, and feature-test error: lines. Capture verbatim:

   • Compiler errors (missing headers, undefined symbols)
   • Post-build check failures (file path issues, misplaced files)
   • Version validation errors
   • Platform-specific feature guard messages

   Report each feature failure individually. Dependency ports that fail get their own entry.

4. Version validation — Inspect the "Validate version files" evidence for version database errors.

5. Write report immediately — Generate and save report.md using the step-log evidence.

Phase 2: Analyze artifacts and enhance

6. Analyze artifacts — Read relevant stdout-{triplet}.log tails and supporting logs. Classify per references/vcpkg-failure-patterns.md.
7. Baselines — Check both ci.baseline.txt and ci.feature.baseline.txt.
8. Enhance report — Add root causes, downstream impact, and actionable recommendations supported by the evidence.

Report Requirements

Format per references/report-template.md:

• Full build URL: [{buildNumber}](https://dev.azure.com/vcpkg/public/_build/results?buildId={buildId})
• For PRs: [#{prNumber}](https://github.com/microsoft/vcpkg/pull/{prNumber})
• List every triplet by full name (e.g., x64-windows, arm64-linux) — never "N triplets". Only include triplets that actually had failures for this specific build.
• Use exact failure type keywords from logs: BUILD_FAILED, POST_BUILD_CHECKS_FAILED, FILE_CONFLICTS, CASCADED_DUE_TO_MISSING_DEPENDENCIES — never paraphrase
• Include error messages verbatim — quote the exact text from logs for compiler errors, path issues, and validation failures
• Dependency ports' failures as separate entries
• Include baseline/known failures — report them with their failure types, but classify them separately from new regressions

Output Structure

Write reports under the session folder from the environment context, alongside the raw evidence, never into the repository working tree:

{session-folder}/files/ci-failure-analysis/
├── ci-129315/         ← scheduled build
│   └── report.md
└── pr-51202/          ← PR build
    └── report.md

Raw evidence stays where fetch-vcpkg-ci-logs placed it, in {session-folder}/files/ci-failure-logs/; reference those paths from the report instead of copying them.

Critical Rules

• Do not fetch or download logs as part of this skill; use the acquisition skill first.
• Scan step logs first because FILE_CONFLICTS may appear only there.
• Check both baseline files
• Never suggest <= version constraints or VCPKG_BUILD_TYPE release
• Clearly distinguish proven root causes from hypotheses and requests for additional diagnostics.