2. Create the GitHub App

Create the GitHub App that Sinatra uses to read code, open PRs, and receive webhooks.

Sinatra integrates with GitHub through a GitHub App (not a personal access token, not OAuth). The App gets installed on each repo or org you want Sinatra to work in.

Create it

Go to github.com → Settings → Developer settings → GitHub Apps → New GitHub App. (For an organization-owned App, replace the user Settings with Organization → Settings → Developer settings.)

Fill in:

GitHub App name: pick something globally unique, e.g. Sinatra (Acme).
Homepage URL: anything — your company URL or GitHub profile.
Callback URL: leave empty.
Request user authorization (OAuth) during installation: off.
Setup URL: https://YOUR_PUBLIC_API/install/github/callback (use your eventual public URL — see step 8).
Webhook → Active: on.
- Webhook URL: https://YOUR_PUBLIC_API/webhooks/github.
- Webhook secret: generate a random secret and save it — this becomes GITHUB_APP_WEBHOOK_SECRET.
```
node -e "console.log(require('crypto').randomBytes(32).toString('hex'))"
```

Permissions

Repository permissions:

Permission	Access
Contents	Read & write
Pull requests	Read & write
Issues	Read & write
Checks	Read-only
Metadata	Read-only

Issues: Read & write is required if you want to trigger Sinatra from GitHub Issues (the agent comments on issues, reacts with 👀, and may edit the issue body to publish a plan). For PR-only flows you can drop it to read-only.

Tick these:

Check suite, Delete, Installation target, Issue comment, Issues, Label, Pull request, Pull request review, Repository.

Installability

Where can this GitHub App be installed? — pick "Only on this account" for a single-org deploy, or "Any account" if you're operating Sinatra for multiple orgs.

Capture the credentials

After clicking Create GitHub App, you'll land on the App's settings page. You need:

App ID — shown at the top of the page. Goes into GITHUB_APP_ID.
Client ID — shown next to App ID. Not used by Sinatra today but record it anyway.
Slug — visible in the URL, e.g. github.com/apps/sinatra-acme → slug is sinatra-acme. Goes into GITHUB_APP_SLUG.
Private key — scroll down, click Generate a private key. A .pem file downloads. Open it; the contents (including the BEGIN/END lines) become GITHUB_APP_PRIVATE_KEY.

Wrap the PEM in double quotes in your env file so newlines are preserved:

GITHUB_APP_PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----
MIIE...
-----END RSA PRIVATE KEY-----"

Install it on your repos

On the App's settings page, click Install App in the left sidebar. Pick the org/account, choose either "All repositories" or specific ones, and confirm. You can come back and add more repos at any time.

Recap — values you've captured

Env var	Where it came from
`GITHUB_APP_ID`	App ID at top of settings page
`GITHUB_APP_SLUG`	URL slug
`GITHUB_APP_WEBHOOK_SECRET`	Random secret you generated
`GITHUB_APP_PRIVATE_KEY`	Downloaded `.pem` contents

Continue to Create the Linear App →