GitHub Action

The Loopback Action runs jobs in your own GitHub Actions runners: the checkout and your AI provider key stay there, and Loopback receives the results of each job. Code understanding and verification are powered by vexp.

The workflow

The onboarding pull request adds this file, shown here for a runner with Claude Code and an API key. For your repository it also sets up the Node version the repository declares and the sign-in to Bedrock or Vertex when you use them, and derives the time limit from your job limit. Loopback starts a job with a repository_dispatch event whose payload carries only the job id and the API address.

# .github/workflows/loopback.ymlname: Loopbackrun-name: Loopback ${{ github.event.client_payload.job_id }}on:  repository_dispatch:    types: [loopback-job]permissions:  contents: write  pull-requests: write  id-token: write          # OIDC sign-in to Loopbackconcurrency:  group: loopback-${{ github.event.client_payload.job_id }}jobs:  run:    runs-on: ubuntu-latest    timeout-minutes: 75    steps:      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1        with:          fetch-depth: 0          persist-credentials: false      - uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0        if: ${{ github.event.repository.private }}        with:          path: .vexp          key: loopback-index-${{ github.run_id }}-${{ github.run_attempt }}          restore-keys: loopback-index-      - name: Install bubblewrap        run: sudo apt-get update -q && sudo apt-get install -y bubblewrap      - uses: loopback-dev/action@v1        with:          agent-key: ${{ secrets.LOOPBACK_AGENT_KEY }}          api-url: "https://api.loopback.so"      - uses: actions/cache/save@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0        if: ${{ !cancelled() && github.event.repository.private }}        with:          path: .vexp          key: loopback-index-${{ github.run_id }}-${{ github.run_attempt }}

What one run does

1. Reads the job id from the dispatch event.
2. Asks GitHub for an OIDC ID token with audience loopback and exchanges it for a job token, valid for that job of that repository for 60 minutes, and an agent token valid only for the tools of that job. Each ID token is accepted once.
3. Downloads the job and prepares the checkout at the job’s base commit, removing the credentials that actions/checkout leaves behind.
4. Runs the agent of the workspace or of .loopback.yml, and streams progress and heartbeats to Loopback; the job can be followed and cancelled from the dashboard.
5. For a fix, runs the verification and your tests, commits only when both pass, and pushes the loopback/ branch with a short-lived token; Loopback opens the pull request.
6. Reports the result. Reporting is idempotent: running the workflow again never creates a second pull request.

Inputs

Outputs

Permissions

• id-token: write lets the job ask GitHub for an OIDC ID token: that is how it signs in to Loopback, with no long-lived secret in your repository.
• The fix branch is pushed with a short-lived installation token that Loopback issues for that job only, limited to the repository and to contents: write, and only to the job’s loopback/ branch.
• The tag is always created by the GitHub App after the approval, never by GITHUB_TOKEN: events of GITHUB_TOKEN do not start other workflows, so your release workflows would not start.

Security model

• No long-lived Loopback secret in your repository: the job signs in with OIDC.
• The job token covers one job and expires in 60 minutes; renewals never outlive the job’s time limit and never add permissions. Only fix jobs can get a push token.
• Every token is masked in the workflow log as soon as the Action holds it.
• The agent cannot push: credentials persisted in the checkout are removed before it starts, and its git commands run without hooks and without any transport.
• The agent runs with a private home, no global git config, and an environment without the Action’s inputs, GITHUB_TOKEN or the OIDC request token.
• Credential files in the checkout, such as .env, private keys and registry credentials, are not readable by the built-in agent, Claude Code or opencode.
• A change that touches .github/, .loopback.yml or .vexp/ is rejected, and the tree is frozen before verification: the commit contains exactly what was verified.
• Ticket text and logs reach the agent wrapped as untrusted content, and secrets are masked out of everything the harness reports.

Agents and credentials

• builtin, the default: the built-in agent with the provider of your key, Bedrock or Vertex.
• claude-code: an Anthropic API key, Bedrock or Vertex. Subscription logins are refused outside MCP mode.
• codex: an OpenAI API key, or a ChatGPT login stored in Loopback, refreshed and saved back after each job, one job at a time.
• opencode: the API key of its provider.
• Bedrock: add aws-actions/configure-aws-credentials with OIDC before the step and set agent.auth: bedrock. Vertex: add google-github-actions/auth and set agent.auth: vertex.

bubblewrap for Claude Code, Codex and your tests

Claude Code runs the agent’s commands through bubblewrap, which removes credentials from their environment. Codex runs only inside bubblewrap, where it cannot see the job’s credentials or the machine’s logins. The harness also runs your installs, tests and type-check in bubblewrap, where they cannot see the job’s credentials. On GitHub-hosted runners the Loopback step installs it. On a self-hosted runner, install it before the Loopback step and allow unprivileged user namespaces; without it the agent does not run your tests, and the harness reports them as not run.

      - name: Install bubblewrap        run: sudo apt-get update -q && sudo apt-get install -y bubblewrap      - uses: loopback-dev/action@v1        with:          agent-key: ${{ secrets.LOOPBACK_AGENT_KEY }}          api-url: "https://api.loopback.so"

Source maps

Add a step after your production build, so that minified stack traces point to real files and lines. The embedded sources are removed before the upload: your code does not leave the runner.

      - run: npm run build      - uses: loopback-dev/action@v1        with:          command: upload-sourcemaps          sourcemaps-path: dist          url-prefix: /          release: my-app@${{ github.ref_name }}          api-url: https://api.loopback.so