version: "1.0.0" name: code-review description: Review changes in microsoft/microsoft-ui-xaml. Use when reviewing code or pull requests in this repository.

Code Review

1. Match the coding style of the current file. Check that changes follow

the file's existing naming, formatting, and code patterns. Do not request unrelated style changes.

1. Do not include Microsoft internal information. Check code, comments,

documentation, and PR content for internal-only information, such as internal links, confidential details, or credentials. Do not copy that information into review comments; identify its location without repeating it.

1. Check open PRs for related work. Look at open pull requests in

microsoft/microsoft-ui-xaml for changes to the same files, components, or behavior. Inspect likely matches and mention relevant overlap, conflicts, or duplicate work with links to those PRs. If you cannot access the open PRs, state that this check could not be completed.

1. Expect test coverage for every bug fix and new feature. Bug fixes should

include regression tests that fail without the fix and pass with it. New features should have tests for their intended behavior and relevant edge cases. Use the repo's existing test patterns and flag missing coverage.

1. Consider behavioral compatibility, even across major versions. WinUI apps

are historically very sensitive to behavioral changes that seem minor. A semver major version increase can still require care when changing existing behavior. Apps may depend on how WinUI APIs behave, including undocumented behavior or dependencies they took accidentally. For example, changing the order in which events fire can break apps even when API signatures stay the same. Highlight potential compatibility risks and consider whether the change needs additional tests or a gradual rollout.

For behavioral changes, features can use XamlOptionalChanges to let apps opt in to the new behavior first. These behaviors are expected to become the default later, with apps able to opt out. Consider this approach when a change could affect existing apps.