What problem does it solve? Jac builds fail or behave inexplicably for reasons that are hard to trace: cryptic E/W diagnostics, stale compiled bytecode or persisted graph data, and client code that silently drifts after a server contract changes. This Skill provides a systematic fix loop for reading jac check output, triaging staleness, and locating the real source of an error. ## Core Features & Use Cases - Diagnostic decoding: Explains the anatomy of jac check errors and warnings (severity letters, category digits, jac guide pointers) and how to suppress codes with # jac:ignore[CODE] or CLI flags. - Stale-cache triage: Maps symptoms like NodeAnchor is not a valid reference to the right cleanup command (jac clean --all --force, jac purge, or removing .jac/data). - Contract drift detection: Interprets W1101/W1051 warnings in client files as pointers to stale callers after a server endpoint rename or retype. - Graph inspection: Uses jac dot to visualize the actual graph when walker logic misbehaves, plus jac browse for end-to-end checks of served apps. - Use Case: After renaming a def:pub endpoint, run jac check project-wide and use this Skill to read the resulting client-file warnings as a list of every stale call site to update. ## Quick Start Ask the assistant to diagnose why your Jac build is failing by pasting the jac check output and having it walk the fix loop.
