Drop-in Codex AI agent with GitHub Models

_CODEX_GITHUB_MODELS.md

This is a drop-in, zero-config Actions harness for OpenAI's Codex agent. It uses GitHub Models for inference, so you don't need to set up any secrets - just copy-pasting the action into your repo should work as-is.

You may need to go into your settings and check the "allow Actions to open PRs" checkbox.

To use it, open an issue in your repo with [codex] in the issue name.

Note: I've updated this to work for the latest version of Codex (the Rust one). If you're using the Python one, you'll have to go to a previous version of this Gist.

codex.yml

name: Codex on GitHub Models

on:
  issues:
    types: [opened]

jobs:
  process-issue:
    if: contains(github.event.issue.title, '[codex]')
    runs-on: ubuntu-latest
    permissions:
      contents: write
      issues: write
      pull-requests: write
      models: read

    steps:
      - name: Checkout repository
        uses: actions/checkout@v3

      - name: Setup Node.js
        uses: actions/setup-node@v3
        with:
          node-version: '22'

      - name: Install Codex CLI
        run: npm install -g @openai/codex
        
      - name: Install ripgrep
        run: sudo apt-get update && sudo apt-get install -y ripgrep

      - name: Process issue with Codex
        env:
          ISSUE_BODY: ${{ github.event.issue.body }}
          ISSUE_NUMBER: ${{ github.event.issue.number }}
          ISSUE_TITLE: ${{ github.event.issue.title }}
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          INSTRUCTION="$ISSUE_TITLE  --- $ISSUE_BODY"
          
          BRANCH_NAME="codex/issue-$ISSUE_NUMBER"
          git checkout -b $BRANCH_NAME

          codex exec \
            -c model=gpt-4.1 \
            -c model_provider=github \
            -c 'model_providers.github={name="GitHub Models", base_url="https://models.github.ai/inference", env_key="GH_TOKEN", wire_api="chat"}' \
            --full-auto "$INSTRUCTION"
          
          if [[ -n $(git status --porcelain) ]]; then
            git config user.name "GitHub Models Codex Bot"
            git config user.email "[email protected]"
            
            git add .
            git commit -m "Codex changes for issue #$ISSUE_NUMBER"
            git push origin $BRANCH_NAME
            
            # Create PR and comment on issue using the same token
            gh pr create --title "Codex: ${{ github.event.issue.title }}" \
              --body "Auto-generated by Codex for issue #$ISSUE_NUMBER" \
              --base ${{ github.event.repository.default_branch }} \
              --head $BRANCH_NAME
              
            gh issue comment $ISSUE_NUMBER --body "Codex created a PR for this issue"
          else
            gh issue comment $ISSUE_NUMBER --body "Codex processed this issue but made no changes"
          fi

@naXa777 Thank you for the feedback! I've added a step to install ripgrep.

About the 413 error - unfortunately the free tier of GitHub Models doesn't have a large enough context window to run Codex (it's 8k tokens max). There's no way around that without going into your GitHub settings for Models and turning on paid usage.

in a public repository, anyone can create an issue with [codex] in the title, which would trigger the workflow.

If you did want to lock this down in a public repository, the easiest way would be to have some kind of allowlist in the workflow body, e.g.:

      - name: Check if user is allowed
        id: check_user
        run: |
          ALLOWED_USERS="user1 user2"
          if [[ " $ALLOWED_USERS " =~ " ${{ github.event.issue.user.login }} " ]]; then
            echo "allowed=true" >> $GITHUB_OUTPUT
          else
            echo "allowed=false" >> $GITHUB_OUTPUT
          fi

      - name: Comment and close if not allowed
        if: steps.check_user.outputs.allowed != 'true'
        run: |
          gh issue comment ${{ github.event.issue.number }} --body "Sorry, only approved users can create [codex] issues."
          gh issue close ${{ github.event.issue.number }}

You could also use the API to check for org membership if you wanted to get more sophisticated with it.