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[{"skill":"github-actions-pipeline-builder","reason":"Builder creates workflows, this skill diagnoses when they break"},{"skill":"ci-cache-optimizer","reason":"Many CI failures stem from cache misses or stale caches"},{"skill":"test-automation-expert","reason":"Flaky test diagnosis often requires test framework expertise"}]
CI Status Checker
Diagnoses CI/CD pipeline failures by reading GitHub Actions logs, identifying failure patterns, and producing actionable fix recommendations. This skill does not write workflows from scratch -- it triages what went wrong with existing ones.
Activation Triggers
Activate on: "CI failing", "build broken", "workflow error", "GitHub Actions debug", "flaky CI", "pipeline timeout", "CI red", "actions run failed", "check failed on PR", "why is CI broken"
Read GitHub Actions run logs and extract the failing step with surrounding context
Classify failures into known categories (dependency, build, test, timeout, OOM, permissions, config)
Suggest targeted fixes based on error pattern matching against known CI failure modes
Detect workflow YAML syntax and configuration issues before they cause runtime failures
Identify flaky tests by analyzing pass/fail patterns across recent runs
Check for common misconfigurations: wrong Node version, missing secrets, incorrect paths
Diagnose matrix build failures where only specific combinations fail
Trace failure cascades (step A fails silently, step B fails loudly because of A)
Diagnostic Process
Step 1: Get Run Status
# Check most recent run status
gh run list --limit 5
# Get details for a specific failed run
gh run view <run-id>
# Get the full log for a failed run
gh run view <run-id> --log-failed
Always start with --log-failed rather than --log to avoid pulling megabytes of passing step output. Only escalate to full logs if the failed step output is insufficient.
Step 2: Identify the Failing Step
Parse the log output to find the first step that failed. CI logs contain noise -- focus on:
The step name that shows a red X
The last 50 lines of that step's output
The exit code (non-zero)
Any ##[error] annotations
Step 3: Classify the Failure
Failure Classification Guide
Category 1: Dependency Installation Failures
Signals:
npm ERR! or yarn error in install step
ERESOLVE unable to resolve dependency tree
404 Not Found for a package
ENOENT for lockfile
pip install failures with version conflicts
Could not find a version that satisfies the requirement
Common causes and fixes:
Error Pattern
Likely Cause
Fix
ERESOLVE peer dependency conflict
Incompatible package versions
npm install --legacy-peer-deps or fix version constraints
404 Not Found for package
Package unpublished or registry down
Check npm status, pin working version
ENOENT package-lock.json
Lockfile not committed
Commit lockfile, or use npm install instead of npm ci
engine "node" incompatible
Wrong Node version in CI
Match node-version in workflow to engines in package.json
ENOMEM during install
Runner out of memory
Use larger runner or reduce parallelism
ETARGET no matching version
Version range resolves to nothing
Pin specific version, check if package was yanked
Category 2: Build Failures
Signals:
TypeScript errors: TS2304, TS2339, TS2345, etc.
Module not found or Cannot find module
SyntaxError: Unexpected token
Build step exits non-zero
Common causes and fixes:
Error Pattern
Likely Cause
Fix
TS2307: Cannot find module
Missing type declarations
Install @types/* package or add to tsconfig.json paths
TS2345: Argument of type
Type mismatch introduced in PR
Fix the type error in source code
Module not found: 'X'
Import path wrong or package missing
Check import paths, verify package in dependencies
JavaScript heap out of memory
Build exceeds Node memory limit
Add NODE_OPTIONS=--max-old-space-size=4096 to env
SIGKILL during build
OOM killer terminated process
Use larger runner (ubuntu-latest-4-cores) or optimize build
Category 3: Test Failures
Signals:
Test runner reports failures with assertion messages
FAIL markers in Jest/Vitest output
Expected X but received Y
Test timeout exceeded
Common causes and fixes:
Error Pattern
Likely Cause
Fix
Assertion failure with clear diff
Real bug introduced in PR
Fix the code (not the test, unless test is wrong)
Timeout on async test
Missing await or slow operation
Add proper await, increase timeout, or mock slow calls
ECONNREFUSED in test
Test needs running service
Use service containers or mock the dependency
Snapshot mismatch
Intentional UI change
Update snapshots with --update-snapshot if change is correct
The job running on runner ... has exceeded the maximum execution time
Step shows no output for extended period then dies
##[error]The operation was canceled
Common causes and fixes:
Error Pattern
Likely Cause
Fix
Job timeout (6h default)
Infinite loop or hung process
Set explicit timeout-minutes per job, investigate hang
Step hangs with no output
Interactive prompt waiting for input
Add -y or --yes flags, pipe yes, set CI=true env
E2E test timeout
Browser not starting or page not loading
Check playwright install --with-deps, add retry
Docker build timeout
Layer cache miss on large image
Use docker/build-push-action with cache-from
Category 5: Permission and Secret Failures
Signals:
Error: Resource not accessible by integration
Error: Input required and not supplied: token
fatal: could not read Username
403 Forbidden on API calls
Common causes and fixes:
Error Pattern
Likely Cause
Fix
Resource not accessible
Insufficient GITHUB_TOKEN permissions
Add permissions: block to workflow
Input required: token
Secret not available in fork PRs
Use pull_request_target or conditional step
could not read Username
Private repo access without token
Use actions/checkout with token: ${{ secrets.PAT }}
403 on deployment
Deploy key or token expired
Rotate secret in repo settings
Category 6: Workflow Configuration Errors
Signals:
Invalid workflow file before any step runs
Unexpected value in YAML parsing
Steps reference nonexistent actions or wrong versions
Common causes and fixes:
Error Pattern
Likely Cause
Fix
Invalid workflow file
YAML syntax error
Validate with actionlint locally
Unexpected value 'X'
Wrong key name or indentation
Check GitHub Actions schema for correct key names
Unable to resolve action
Action not found or wrong version
Verify action exists, use @v4 not @master
Context access might be invalid
Typo in ${{ }} expression
Check variable names against available contexts
Flaky Test Analysis
Flaky tests are tests that pass and fail nondeterministically. They erode trust in CI. Diagnose by pattern:
Detection
# Get last 20 runs for the test job
gh run list --workflow=tests.yml --limit 20 --json status,conclusion,startedAt
# Compare pass/fail ratio
gh run list --workflow=tests.yml --limit 50 --json conclusion | \
jq 'group_by(.conclusion) | map({conclusion: .[0].conclusion, count: length})'
If the same workflow alternates between success and failure without code changes, you have flaky tests.
Common Flaky Patterns
Race condition: Tests share mutable state. Fix: isolate test state, use beforeEach reset.
Timing dependency: Test assumes operation completes in N ms. Fix: use polling/waitFor instead of sleep.
Order dependency: Test passes in isolation but fails when run after another test. Fix: ensure cleanup in afterEach.
Port collision: Multiple test suites bind to same port. Fix: use random ports or --shard.
Timezone/locale: Test passes in US locale but fails in CI (usually UTC). Fix: set TZ=UTC in test env.
File system ordering: readdir returns different order on different OS. Fix: sort results before comparing.
Quarantine Strategy
If a flaky test cannot be fixed immediately:
Move to a flaky/ directory or tag with .skip + a TODO comment with issue link
Create a tracking issue with reproduction details
Set a deadline (2 weeks max) for resolution
Never delete a flaky test -- it caught a real issue at least once
Workflow Validation
Before a workflow runs in CI, validate it locally:
# Install actionlint (the gold standard for workflow linting)
brew install actionlint # macOS# or: go install github.com/rhysd/actionlint/cmd/actionlint@latest# Lint all workflow files
actionlint .github/workflows/*.yml
# Check a specific file with verbose output
actionlint -verbose .github/workflows/ci.yml
Common YAML Pitfalls
Unquoted on: triggers: on: push works, but on: [push, pull_request] needs the brackets
Missing runs-on: Every job needs it
Wrong indentation: Steps under steps: must be at the right level
Expression syntax: ${{ github.event.pull_request.number }} not ${ github.event... }
Matrix include/exclude: include adds combinations, it does not filter -- use exclude to remove
Anti-Patterns
1. Retry Until Green
Symptom: Re-running failed workflow until it passes
Why wrong: Masks real issues, wastes compute minutes, teaches team to ignore CI
Fix: Investigate every failure. If genuinely flaky, quarantine the test and fix the root cause.
2. Disabling Failing Checks
Symptom: Removing status checks from branch protection because they fail
Why wrong: Opens main branch to broken code
Fix: Fix the check, or mark it as continue-on-error: true with a tracking issue.
3. Blaming the Runner
Symptom: "CI is slow/broken, works on my machine"
Why wrong: CI environment differences are the test -- if it fails there, the code has assumptions
Fix: Match CI environment locally. Use act or Docker to reproduce. Add CI=true to local test runs.
4. Giant Log Dumps
Symptom: Pasting entire CI log into an issue or PR comment
Why wrong: No one reads 10,000 lines of logs
Fix: Extract the relevant 10-20 lines around the failure. Include the step name, error message, and exit code.
5. Ignoring Warnings
Symptom: CI passes but with deprecation warnings, security advisories, or linting warnings
Why wrong: Warnings become errors in the next major version. Technical debt compounds.
Fix: Treat warnings as errors in CI (--max-warnings 0 for ESLint, --strict for TypeScript).
6. Monolithic Workflow Files
Symptom: Single 500-line workflow file that does lint + test + build + deploy
Why wrong: One failure blocks everything, hard to debug, impossible to re-run selectively
Fix: Split into separate workflows or use reusable workflows with workflow_call.
If infrastructure is healthy, the failure is yours to own.
When matrix failures are partial
If only node-18, ubuntu-latest fails but node-20, ubuntu-latest passes:
The fix is probably a Node 18 compatibility issue
Check if the project's engines.node matches the matrix
Consider dropping the failing version if it is EOL
Quality Checklist
[ ] Identified the exact failing step (not just "CI failed")
[ ] Classified failure into correct category (dependency/build/test/timeout/permission/config)
[ ] Reproduced locally when possible (or explained why not)
[ ] Fix addresses root cause, not symptoms (no blind retries)
[ ] Flaky tests either fixed or quarantined with tracking issue
[ ] Workflow YAML validates with actionlint after changes
[ ] CI minutes impact considered (larger runner = more cost)
[ ] Secrets verified as available for the trigger type (push vs pull_request vs fork)
[ ] Timeout values set explicitly on long-running jobs
[ ] Status check passes on the fix PR before merging
Quick Reference Commands
# List recent workflow runs
gh run list --limit 10
# View a specific run (shows jobs and steps)
gh run view <run-id>
# Get only failed step logs
gh run view <run-id> --log-failed
# Re-run failed jobs only (not the whole workflow)
gh run rerun <run-id> --failed
# Watch a running workflow
gh run watch <run-id>
# List workflow filesls .github/workflows/
# Validate workflow syntax locally
actionlint .github/workflows/*.yml
# Check GitHub Actions service status
open https://www.githubstatus.com/
# Run workflow manually (if workflow_dispatch enabled)
gh workflow run <workflow-name>
