Classify WIT interface changes as breaking or non-breaking against frozen version markers. Use this skill when the user wants to check WIT breaking changes, review a WIT diff, verify whether a WIT change is breaking, or run a WIT compat check. Trigger on: 'check WIT breaking changes', 'review WIT diff', 'is this WIT change breaking', 'WIT compat check'.
Installation
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Classify WIT interface changes as breaking or non-breaking against frozen version markers. Use this skill when the user wants to check WIT breaking changes, review a WIT diff, verify whether a WIT change is breaking, or run a WIT compat check. Trigger on: 'check WIT breaking changes', 'review WIT diff', 'is this WIT change breaking', 'WIT compat check'.
WIT Breaking Change Check
Classifies every modification in the current WIT diff against the breaking-change taxonomy and reports a verdict for each finding.
When to Use
Before merging any branch that touches wit/
When reviewing a PR that modifies WIT interface definitions
To verify a WIT change is safe before publishing a plugin-compatible release
Procedure
Run git diff origin/master -- wit/ to obtain the current diff.
For each wit/vN/ directory in the diff, check whether wit/vN/.frozen exists. If absent, report the version as experimental and skip it.
For each frozen version with changes, classify every modification against the breaking-change taxonomy in wit/VERSIONING.md:
Breaking: removing/renaming any type, function, record field, or variant case; changing a function signature; changing a field type; reordering record fields; adding a required (non-optional) field to an existing record; adding a non-capability-gated required function to an existing interface.
Non-breaking: new flags bits, new capability-gated functions, new record/variant/enum types, new interfaces, new worlds, @since/@unstable annotation additions.
Report each finding with a verdict:
✅ Non-breaking — with a brief reason citing the taxonomy
❌ Breaking — with a brief reason citing the taxonomy
⚠️ Uncertain — with the ambiguity explained
If any breaking change is found, summarize the required migration path for plugin authors.
Notes
The .frozen marker is a human-readable convention: its presence signals to reviewers and this skill that the version is stable and requires the breaking-change check before merge. Experimental (unfrozen) versions are skipped without a verdict.
