The container works on your laptop but fails in production with "exec format error". What happened?

The image was built for the wrong CPU architecture: arm64 on the Mac, amd64 in production.

• Check with docker image inspect (Architecture) or docker manifest inspect.
• Fix: build in CI, not on laptops, or use docker buildx build --platform linux/amd64 (or a multi-arch image for both).
• The same error appears when a script has no shebang or has Windows line endings, so check that if the architecture matches.