Include commit URLs in VERCEL_RELATED_PROJECTS and deployment webhooks for monorepo E2E testing

Problem

When using Related Projects in a monorepo with two apps (e.g., api and ui), it’s difficult to run E2E tests against commit-specific preview deployments due to URL mismatches.

Current behavior:

The VERCEL_RELATED_PROJECTS environment variable only includes the branch URL for preview deployments, not the commit-specific URL:

{
  "preview": {
    "branch": "my-app-git-feature-branch-team.vercel.app"
  }
}

The vercel.deployment.success repository_dispatch webhook event_payload only includes the commit URL, not the branch URL:

{
  "url": "https://my-app-a1b2c3d4-team.vercel.app"
}

The issue:

The api uses VERCEL_RELATED_PROJECTS to configure CORS, so it only allows the ui’s branch URL.
The GitHub workflow receives the commit URL from the webhook.
E2E tests running against the commit URL fail CORS because only the branch URL is allowed.
Commit URLs cannot be derived between projects (different deployment IDs despite same git SHA).
Branch URLs cannot be derived in the GitHub Action from the payload.

Proposed Solution

Add branchUrl to the repository_dispatch payload:

{
  "url": "https://my-app-a1b2c3d4-team.vercel.app",
  "branchUrl": "https://my-app-git-feature-branch-team.vercel.app"
}

This would enable testing against the branch URL, if wanted.

Add commit (commit URL) to VERCEL_RELATED_PROJECTS for preview:

{
  "preview": {
    "branch": "my-app-git-feature-branch-team.vercel.app",
    "commit": "my-app-a1b2c3d4-team.vercel.app"
  }
}

This would help to setup the correct CORS URL and each ui commit would run against the related commit URL of the backend (preventing version/commit mismatch).

Use Case

Running E2E tests in CI against commit-specific preview deployments in a monorepo where the frontend needs to communicate with a related api project, and CORS must be correctly configured.

Thank you for considering this!