Find the first meaningful error in the build output. The final “build failed” line usually describes the result rather than the cause.
From the project root, collect:
Compare your SDK with the release requirements. The inspected source requires Dart ^3.12.2. Keep the supplied pubspec.lock when reproducing a problem.
Run flutter pub get to restore dependencies. If a generated model/provider file is missing or stale after source changes, run:
For changed ARB translations, run flutter gen-l10n. Do not repair .g.dart or .freezed.dart files manually.
Android errors mentioning Gradle, JDK, SDK, or Kotlin need the Android compatibility article. iOS errors mentioning signing, Pods, or deployment targets need the Xcode article. A Firebase package/bundle mismatch requires the correct Firebase registration and files.
Use flutter clean only when stale build artifacts are a plausible cause, then restore dependencies and rebuild. It does not resolve incompatible package constraints or invalid source code.
If a clean copy of the same release builds but your customized copy does not, compare changes incrementally. Share the first actionable error and environment details with support after removing sensitive information.