The Microfrontends Config Present deployment check prevents broken production routing by blocking any default app deployment that is missing its microfrontends.json. This appears alongside other Native Deployment Checks, such as lint and typecheck.
The check is blocking by default for eligible apps, with no opt-in required. Eligible apps are projects enrolled in Vercel Microfrontends and designated as the default app in a Microfrontends group. If microfrontends.json is missing from the deployment's build outputs, the check fails and prevents the deployment from reaching production.
This can happen when a deployment from an older branch without the Microfrontends config is manually promoted. The check passes on the next deployment once microfrontends.json is included in the build outputs.
To adjust check behavior, visit your project's Build and Deployment Settings.