# Authoring Github Workflows

Author and review GitHub Actions workflow YAML safely so syntactically-valid YAML can't...

- Repository: https://github.com/dotnet/skills (5787 stars)
- Category: Design
- License: MIT
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add dotnet/skills --skill authoring-github-workflows -g -a claude-code -y`
Codex: `npx skills add dotnet/skills --skill authoring-github-workflows -g -a codex -y`
Cursor: `npx skills add dotnet/skills --skill authoring-github-workflows -g -a cursor -y`
Gemini CLI: `npx skills add dotnet/skills --skill authoring-github-workflows -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add dotnet/skills`

## Description

Author and review GitHub Actions workflow YAML safely so syntactically-valid YAML can't ship a workflow that GitHub Actions refuses to run. USE FOR: editing, adding, or reviewing any file under .github/workflows/, writing run-name/name/if/env/run values that contain ${{ }} expressions, diagnosing a run that fails with 'This run likely failed because of a workflow file issue' and no jobs starting, deciding when a workflow scalar must be quoted, validating workflows with actionlint. DO NOT USE FOR: authoring application YAML unrelated to GitHub Actions, Azure Pipelines, GitLab CI, or non-workflow YAML. SCOPE: this skill covers *syntactic/structural* correctness of workflow YAML (quoting, parsing, actionlint); for *semantic and functional* workflow design (what a workflow should do, agentic-workflow behavior), see .github/agents/agentic-workflows.agent.md, the two are complementary. INVOKES: actionlint (downloaded pinned binary) plus git/grep for inspection.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Authoring GitHub Actions Workflows Safely

GitHub Actions workflow files are YAML, but **valid YAML is not the same as a valid workflow**. A workflow can parse cleanly with `yaml.safe_load` (or a casual review) yet still be rejected by GitHub Actions at load time, producing the opaque failure *"This run likely failed because of a workflow file issue"* with **zero jobs started**. This skill teaches the YAML-vs-Actions traps (the `#`-as-comment trap above all), how to quote expression scalars correctly, and how to validate with `actionlint` before merge.

> **Scope: syntactic vs. semantic.** This skill is about the *syntactic and structural* correctness of workflow YAML, quoting, parsing, and `actionlint`-level validity that determines whether GitHub Actions will load and run a file at all. It is **not** about *what* a workflow should do or how an agentic workflow should behave. For *semantic and functional* guidance (designing workflow logic, agentic-workflow patterns, gh-aw authoring), use [`.github/agents/agentic-workflows.agent.md`](../../../.github/agents/agentic-workflows.agent.md). The two are complementary: get the behavior right with the agent, get the YAML right with this skill.

## When to Use

- Editing, adding, or reviewing any file under `.github/workflows/`.
- Writing a `run-name`, `name`, `if`, `env`, `with`, or `run` value that embeds a `${{ }}` expression.
- A workflow run failed with *"This run likely failed because of a workflow file issue"* and **no jobs ran**.
- Eval/CI on `main` suddenly breaks for every run after a workflow edit merged, even though the change "looked fine."
- Deciding whether a YAML scalar needs quoting.

## When Not to Use

- Authoring non-Actions YAML (app config, Kubernetes, Compose, Azure Pipelines, GitLab CI).
- Pure shell/script logic inside an already-valid `run:` block (that is a scripting task, not a workflow-syntax task).

## The #1 Trap: `#` inside an unquoted expression becomes a YAML comment

The rest: https://github.com/dotnet/skills/blob/HEAD/.agents/skills/authoring-github-workflows/SKILL.md