Read a diagnostic
Text diagnostics identify a source path, line, column, severity, code and message. Text lines and columns are one-based; columns count UTF-8 bytes. JSON primary/related spans are zero-based, half-open UTF-8 byte offsets into the identified source revision, not editor character positions. LSP positions use their negotiated encoding (UTF-16 by default). JSON output is available for commands that support --format=json; preserve its completeness and omitted-count fields when automating. Exit status 0 means no blocking diagnostics, 10 means source errors were reported, and 2 means command or tool failure. Warnings alone do not block.
can check Tasks.can
can check --format=json Tasks.can
can explain E7004
Use can explain CODE when a diagnostic code has a registered explanation. A corrective suggestion is guidance; recheck the source after applying it, since a fix can expose another type or authority issue.
Repair at the owner
Follow the name in the diagnostic to its owning declaration. A missing imported member is usually repaired in the provider declaration or composition, not by adding a guessed local alias. A type error belongs at the expression or declared field boundary. An authorization error belongs in the policy or operation declaration; exposing a hidden control does not repair it.
Parser errors can cause later lines to be interpreted incorrectly. Fix the earliest structural error first, then rerun the check. When a diagnostic refers to generated implementation, use generation lifecycle and editing and refinement; do not weaken a source contract merely to silence a generated-code mismatch.
Inspect source constructs
can help COMMAND displays command help. can policy FILE.can inspects the declared role and policy gates. Construct-specific help uses stable source-owned identifiers through the development controls; it is tied to a source revision. If a request refers to an obsolete revision, refresh status and ask for help against the current source. Exact language forms remain owned by the grammar (on GitHub) and language design (on GitHub).
Do not paste private business records, credentials or generated customer content into diagnostic feedback. Report the source location, diagnostic code, expected behavior and a small safe reproduction.