Claude Code workflow (DifferentiableUniverseInitiative/jax_cosmo)

The Claude Code workflow from DifferentiableUniverseInitiative/jax_cosmo, explained and optimized by Latchkey.

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Source: DifferentiableUniverseInitiative/jax_cosmo.github/workflows/claude.ymlLicense MITView source

What it does

This is the Claude Code workflow from the DifferentiableUniverseInitiative/jax_cosmo repository, a real project running GitHub Actions. It is shown here with attribution under its MIT license.

Below, Latchkey shows a faster, safer version produced by its optimization engine.

The workflow

workflow (.yml)

name: Claude Code

on:
  issue_comment:
    types: [created]
  pull_request_review_comment:
    types: [created]
  issues:
    types: [opened, assigned]
  pull_request_review:
    types: [submitted]

jobs:
  claude:
    if: |
      (github.event_name == 'issue_comment' && contains(github.event.comment.body, '@claude') && github.event.comment.user.login == 'EiffL') ||
      (github.event_name == 'pull_request_review_comment' && contains(github.event.comment.body, '@claude') && github.event.comment.user.login == 'EiffL') ||
      (github.event_name == 'pull_request_review' && contains(github.event.review.body, '@claude') && github.event.review.user.login == 'EiffL') ||
      (github.event_name == 'issues' && (contains(github.event.issue.body, '@claude') || contains(github.event.issue.title, '@claude')) && github.event.issue.user.login == 'EiffL')
    runs-on: ubuntu-latest
    permissions:
      contents: read
      pull-requests: read
      issues: read
      id-token: write
    steps:
      - name: Checkout repository
        uses: actions/checkout@v4
        with:
          fetch-depth: 1

      - name: Run Claude Code
        id: claude
        uses: anthropics/claude-code-action@beta
        with:
          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
          
          # Optional: Specify model (defaults to Claude Sonnet 4, uncomment for Claude Opus 4)
          # model: "claude-opus-4-20250514"
          
          # Optional: Customize the trigger phrase (default: @claude)
          # trigger_phrase: "/claude"
          
          # Optional: Trigger when specific user is assigned to an issue
          # assignee_trigger: "claude-bot"
          
          # Optional: Allow Claude to run specific commands
          allowed_tools: "Bash(python *),Bash(git *),Bash(pip *)"
          
          # Optional: Add custom instructions for Claude to customize its behavior for your project
          custom_instructions: |
            Follow our coding standards
            Ensure all new code has tests, try to test against PyCCL as much as possible
            Prefer simplicity and clarity in code, and functional programming principles
          
          # Optional: Custom environment variables for Claude
          # claude_env: |
          #   NODE_ENV: test

The same workflow, on Latchkey

Removes redundant runs and caps runaway jobs. Added and changed lines are highlighted.

name: Claude Code
 
on:
  issue_comment:
    types: [created]
  pull_request_review_comment:
    types: [created]
  issues:
    types: [opened, assigned]
  pull_request_review:
    types: [submitted]
 
jobs:
  claude:
    timeout-minutes: 30
    if: |
      (github.event_name == 'issue_comment' && contains(github.event.comment.body, '@claude') && github.event.comment.user.login == 'EiffL') ||
      (github.event_name == 'pull_request_review_comment' && contains(github.event.comment.body, '@claude') && github.event.comment.user.login == 'EiffL') ||
      (github.event_name == 'pull_request_review' && contains(github.event.review.body, '@claude') && github.event.review.user.login == 'EiffL') ||
      (github.event_name == 'issues' && (contains(github.event.issue.body, '@claude') || contains(github.event.issue.title, '@claude')) && github.event.issue.user.login == 'EiffL')
    runs-on: latchkey-small
    permissions:
      contents: read
      pull-requests: read
      issues: read
      id-token: write
    steps:
      - name: Checkout repository
        uses: actions/checkout@v4
        with:
          fetch-depth: 1
 
      - name: Run Claude Code
        id: claude
        uses: anthropics/claude-code-action@beta
        with:
          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
          
          # Optional: Specify model (defaults to Claude Sonnet 4, uncomment for Claude Opus 4)
          # model: "claude-opus-4-20250514"
          
          # Optional: Customize the trigger phrase (default: @claude)
          # trigger_phrase: "/claude"
          
          # Optional: Trigger when specific user is assigned to an issue
          # assignee_trigger: "claude-bot"
          
          # Optional: Allow Claude to run specific commands
          allowed_tools: "Bash(python *),Bash(git *),Bash(pip *)"
          
          # Optional: Add custom instructions for Claude to customize its behavior for your project
          custom_instructions: |
            Follow our coding standards
            Ensure all new code has tests, try to test against PyCCL as much as possible
            Prefer simplicity and clarity in code, and functional programming principles
          
          # Optional: Custom environment variables for Claude
          # claude_env: |
          #   NODE_ENV: test

What changed

Run on Latchkey managed runners with one line (runs-on), which apply the fixes below automatically and self-heal transient failures. This example uses latchkey-small; pick the runner size that fits the job.
Add a job timeout so a hung step cannot burn hours of runner time.

1 third-party action is referenced by a movable tag. Pin it to the commit SHA (Latchkey resolves and applies this automatically) so a repointed tag cannot change what runs.

This workflow runs 1 job per trigger. On Latchkey the same minutes cost up to 58% less than GitHub-hosted, with zero queue time.

Actions used in this workflow

actions/checkout