_BUILD_TIMEOUT not respected in AWS Amplify — build still cancels after 30 minutes

[brightversion1]

Environment information

Service: AWS Amplify Hosting

Build system: Amplify Console (CodeBuild backend)

Build configuration: Using amplify.yml

Runtime: Node.js 20

Region: (add your region, e.g. eu-west-2)

Branch setup: Multiple branch environments, each with _BUILD_TIMEOUT defined in Amplify environment variables

Describe the bug

Even after defining _BUILD_TIMEOUT as an environment variable (both in Amplify App Environment Variables and Branch-specific Environment Variables), Amplify deployments are still being cancelled automatically after ~30 minutes, which matches the default build timeout.

It appears that the _BUILD_TIMEOUT environment variable is ignored by Amplify’s underlying CodeBuild configuration.

Reproduction steps

🔁 Reproduction Steps

1. Go to Amplify Console → App → App Settings → Environment Variables.

2. Add the variable:

   _BUILD_TIMEOUT=90
   

3. Also add the same variable under Branch settings → Environment variables.

4. Trigger a new deployment (build takes >30 min).

5. Observe that Amplify terminates the build after 30 minutes despite _BUILD_TIMEOUT being set.

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⚙️ Expected Behavior

Amplify should extend the build duration based on _BUILD_TIMEOUT — or provide a documented, working method to configure build timeout per branch/environment.

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### 💬 **Additional Context**

There is no clear documentation on whether `_BUILD_TIMEOUT` is a supported environment variable in Amplify Hosting or only in Amplify CI/CD pipelines.
If not supported, there should be a documented way to increase build time beyond 30 minutes without switching to manual CodeBuild project control.