github-actions

name

github-actions

description

Generates and validates GitHub Actions workflows and custom actions (composite/Docker/JavaScript) with SHA-pinned supply chain security, SLSA attestation, OIDC federation, and harden-runner enforcement. Use when creating, editing, reviewing, or validating CI/CD pipelines, reusable workflows, monorepo CI patterns, container build/deploy orchestration, or advanced triggers (workflow_run, dispatch, ChatOps).

[H1][GITHUB-ACTIONS]

Dictum: Workflow generation and validation enforce security, performance, and supply chain integrity.

Generate and validate production-ready GitHub Actions workflows and custom actions.

Tasks:

1. Gather requirements — triggers, runners, dependencies, environments, security posture.
2. Read best-practices.md — security hardening, supply chain, performance, anti-patterns.
3. Read version-discovery.md — SHA resolution protocol, action index, permissions.
4. Read expressions-and-contexts.md — contexts, functions, injection prevention.
5. (advanced triggers) Read advanced-triggers.md — workflow_run, dispatch, ChatOps, merge queue.
6. (custom actions) Read custom-actions.md — composite, Docker, JavaScript action authoring.
7. Resolve action versions — git ls-remote, Context7 MCP, or WebSearch for latest SHA.
8. Generate — SHA-pinned actions, minimal permissions, concurrency, caching, timeouts, harden-runner.
9. Validate — Read validation references, run actionlint, apply 11 best practice checks.
10. Fix and re-validate until passing (max 3 iterations).

Scope:

• Workflow files (.github/workflows/*.yml).
• Custom actions — composite, Docker, JavaScript (.github/actions/*/action.yml).
• Reusable workflows (workflow_call).
• Supply chain — SLSA attestation, SBOM, Cosign signing.
• Monorepo CI — Nx affected detection, sparse checkout, pnpm workspace caching.

References:

Domain	File
Best Practices	best-practices.md
Version Discovery	version-discovery.md
Expressions	expressions-and-contexts.md
Advanced Triggers	advanced-triggers.md
Custom Actions	custom-actions.md
Common Errors	common_errors.md
Supply Chain	supply_chain.md
Modern Features	modern_features.md
Runners	runners.md
Actionlint + Act	act_usage.md
Template	basic-workflow.template.yml
Template	reusable-workflow.template.yml
Template	composite-action.template.yml
Template	docker-action.template.yml
Template	javascript-action.template.yml
Example	nodejs-ci.yml
Example	docker-build-push.yml
Example	monorepo-ci.yml
Example	dependency-review.yml
Example	sbom-attestation.yml
Example	setup-node-cached-action.yml
Example	chatops-dispatch.yml

---

[1][STANDARDS]

Dictum: Mandatory standards enforce baseline quality across all generated workflows.

Every generated workflow enforces defense-in-depth: supply chain integrity prevents compromised actions from executing, minimal permissions limit blast radius if a job is compromised, and harden-runner detects anomalous behavior at runtime. These layers are independent — failure of one leaves others intact.

[CRITICAL]:

• [ALWAYS] SHA-pin every uses: reference — mutable tags (@v1, @main) enable supply chain attacks. The tj-actions incident (CVE-2025-30066) compromised 23,000+ repos via tag retargeting.
• [ALWAYS] step-security/harden-runner as first step in every job — detected the tj-actions breach before any other tool.
• [ALWAYS] Top-level permissions: {} (deny-all default); grant minimal per-job permissions.
• [ALWAYS] timeout-minutes: on every job — prevents runaway billing on stuck workflows.

[IMPORTANT]:

• [ALWAYS] OIDC federation (id-token: write) for cloud auth — eliminates static credentials entirely.
• [ALWAYS] actions/create-github-app-token for cross-repo ops — scoped, 1-hour expiry, survives offboarding.
• [ALWAYS] >> $GITHUB_OUTPUT for step outputs; >> $GITHUB_STEP_SUMMARY for job summaries.
• [NEVER] Direct ${{ }} interpolation of untrusted input in run: blocks — route through env: indirection.

[REFERENCE] best-practices.md — Security checklist, supply chain controls, anti-patterns.

---

[2][TEMPLATES]

Dictum: Templates scaffold canonical workflow and action structure.

Templates use [PLACEHOLDER] syntax for generation-time substitution. SHA resolution happens at generation time via the discovery protocol — templates contain placeholder SHAs, not static pins.

[2.1][PLACEHOLDER_CONVENTION]

All templates use a unified [UPPER_SNAKE_CASE] placeholder convention:

[CATEGORY]	[PLACEHOLDERS]
Identity	[ACTION_NAME], [WORKFLOW_NAME], [DESCRIPTION], [AUTHOR_NAME]
Runtime	[RUNTIME_VERSION], [RUNTIME_ENV_KEY], [ENABLE_CMD]
Package Mgr	[PACKAGE_MANAGER], [INSTALL_CMD]
Build/Test	[BUILD_CMD], [LINT_CMD], [TEST_CMD], [BUILD_PATH], [RESULTS_PATH]
Deploy	[ENV_NAME], [ENV_URL], [DEPLOY_CMD], [VERIFY_CMD]
Secrets	[SECRET_KEY], [SECRET_NAME], [REGISTRY_TOKEN]
Docker	[BASE_IMAGE], [BUILDER_IMAGE], [ENTRYPOINT]

[2.2][HARDEN_RUNNER_SCOPE]

harden-runner is included as the first step in every workflow job template (basic, reusable). Action templates (composite, Docker, JavaScript) do NOT include harden-runner — the calling workflow is responsible for adding it as the first step in the job that invokes the action. Actions are steps, not jobs.

[2.3][TEMPLATE_INDEX]

[INDEX]	[TEMPLATE]	[PATH]	[SCAFFOLDS]
[1]	Basic Workflow	templates/basic-workflow.template.yml	CI pipeline: lint, test, build, deploy with parameterized runtime.
[2]	Reusable Workflow	templates/reusable-workflow.template.yml	workflow_call with typed inputs, secrets, version extraction.
[3]	Composite Action	templates/composite-action.template.yml	Multi-step action with parameterized runtime and error handling.
[4]	Docker Action	templates/docker-action.template.yml	Container action with distroless multi-stage Dockerfile pattern.
[5]	JavaScript Action	templates/javascript-action.template.yml	Node 24 action with pre/post lifecycle, typed error handling.

[REFERENCE] custom-actions.md — Action type selection, metadata, runtime deprecation.

---

[3][EXAMPLES]

Dictum: Examples demonstrate production patterns for common scenarios.

Each example demonstrates distinct patterns with minimal overlap. Load relevant examples before generation to match the target scenario.

[INDEX]	[EXAMPLE]	[PATH]	[DEMONSTRATES]
[1]	Node.js CI	examples/nodejs-ci.yml	Matrix testing, caching, artifact upload, coverage, summaries.
[2]	Docker Build + Push	examples/docker-build-push.yml	Multi-platform builds, GHCR, BuildKit caching, SLSA provenance.
[3]	Monorepo CI	examples/monorepo-ci.yml	Nx affected detection, pnpm workspace, sparse checkout.
[4]	PR Security Gate	examples/dependency-review.yml	Multi-job security: dep review, CodeQL, Gitleaks, triage.
[5]	Container Supply Chain	examples/sbom-attestation.yml	SBOM, Trivy severity gating, Cosign, gh attestation verify.
[6]	Composite Action (setup-node-cached)	examples/setup-node-cached-action.yml	Smart caching, corepack detection, cache-dir resolution.
[7]	ChatOps Dispatch	examples/chatops-dispatch.yml	Slash commands, injection prevention, App token, env indirection.
[8]	Multi-Cloud OIDC Auth	examples/oidc-cloud-auth-action.yml	Composite action: AWS/GCP/Azure OIDC, output normalization.
[9]	Release + Deploy	examples/release-deploy.yml	Environment promotion, reusable workflow, concurrency groups.
[10]	Docker Lint + Scan	examples/docker-lint-scan-action.yml	Composite action: Trivy scan, hadolint, SARIF output.
[11]	PR Change Router	examples/pr-change-router-action.yml

---

[4][ACTION_DISCOVERY]

Dictum: Runtime version resolution prevents stale SHA pins and supply chain drift.

Static SHA catalogs decay — actions release frequently and stale pins miss security patches. Resolve versions at generation time. Never embed hardcoded SHAs in reference docs or templates.

Resolution protocol:

1. git ls-remote --tags https://github.com/{owner}/{repo} — verify tag exists.
2. gh api repos/{owner}/{repo}/git/ref/tags/{tag} --jq '.object.sha' — resolve tag to full SHA.
3. Format: owner/repo@<40-char-SHA> # vX.Y.Z.

Fallback methods:

• Context7 MCP: resolve-library-id then get-library-docs for action documentation.
• WebSearch: "[owner/repo] [version] github action" for release notes.

[IMPORTANT]:

• [ALWAYS] Verify the tag exists before pinning — deleted tags return empty results.
• [ALWAYS] Include version comment suffix (# vX.Y.Z) — Dependabot/Renovate parse these for automated updates.
• [NEVER] Embed static SHAs in reference files — they decay within weeks.

[REFERENCE] version-discovery.md — Discovery protocol, SHA pinning format, common actions index, automated maintenance.

---

[5][VALIDATION]

Dictum: Three-stage pipeline and 11 best practice checks gate workflow quality.

Validation pipeline:

[INDEX]	[STAGE]	[TOOL]	[VALIDATES]
[1]	Static Analysis	actionlint 1.7.10	YAML syntax, expressions, runner labels, action inputs, CRON, globs.
[2]	Best Practices	11 custom checks	SHA pinning, permissions, injection, timeouts, harden-runner.
[3]	Local Execution	act v0.2.84	Dry-run validation against Docker images (requires Docker).

Best practice checks (11):

[INDEX]	[CHECK]	[TAG]	[DETECTS]
[1]	Deprecated commands	[DEPRECATED-CMD]	::set-output, ::save-state, ::set-env, ::add-path.
[2]	Missing permissions	[PERMISSIONS]	No top-level permissions: {} deny-all default.
[3]	Unpinned actions	[UNPINNED]	Mutable tags (@v1, @main), abbreviated SHAs.
[4]	SHA without comment	[SHA-NO-COMMENT]	SHA-pinned but missing # vX.Y.Z version comment.
[5]	Missing timeout	[TIMEOUT]	Jobs without timeout-minutes: (default is 6 hours).
[6]	Deprecated runners	[RUNNER]	ubuntu-20.04, macos-12, macos-13, windows-2019.
[7]	Missing concurrency	[CONCURRENCY]	No concurrency: group or missing cancel-in-progress.
[8]	PAT usage	[APP-TOKEN]	PATs for cross-repo ops (use create-github-app-token).
[9]	No harden-runner	[HARDEN]	Missing or not first step in job (CVE-2025-30066 detection).
[10]	Expression injection	[INJECTION]

Error routing: Match error patterns to reference files — common_errors.md (syntax, expressions, deprecated), runners.md (labels, deprecations), supply_chain.md (SHA, OIDC, SBOM, harden-runner), modern_features.md (reusable workflows, concurrency, matrix, node runtime), act_usage.md (actionlint rules, act limitations).

Troubleshooting:

[INDEX]	[ISSUE]	[SOLUTION]
[1]	Tools not found	Install actionlint + act (see act_usage.md).
[2]	Docker not running	Start Docker or validate with actionlint only.
[3]	act fails, GitHub works	See act_usage.md — Limitations.
[4]	ARM Mac arch mismatch	Add --container-architecture linux/amd64.
[5]	Custom runner labels	Declare in .github/actionlint.yaml.

[VERIFY] Completion:

• Supply chain: Every uses: reference SHA-pinned with # vX.Y.Z comment suffix.
• Security: Top-level permissions: {}, per-job minimal grants, harden-runner first step.
• Injection: No direct ${{ github.event.* }} in run: blocks — all through env: indirection.
• Performance: Caching enabled, concurrency groups set, timeout-minutes: on every job.
• Structure: Descriptive name: on workflow/jobs/steps, lowercase-hyphen filenames.
• Outputs: >> $GITHUB_OUTPUT for data, >> $GITHUB_STEP_SUMMARY for summaries.
• Harden-runner: Workflow jobs include it; action templates note caller responsibility.
• All errors resolved with reference-backed fixes; warnings documented.

[REFERENCE] best-practices.md — Anti-patterns with specific remediations.