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.

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: Process issue with Codex
        env:
          OPENAI_API_KEY: ${{ secrets.GITHUB_TOKEN }}
          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

          export OPENAI_BASE_URL=https://models.github.ai/inference

          # any provider string would work here, it's just so codex knows it's using a custom model
          codex --approval-mode full-auto --provider github --model openai/gpt-4.1 --quiet "$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