Apply when auditing test coverage on changed packages. Used by the `tester` agent. Encodes the project's stance: branch and invariant coverage matter more than total %, deliberate exclusions must be recorded with reasoning.
Apply when verifying that comments and docs match the current code state. Used by the `tech-writer` agent. Encodes the project's WHY-only comment rule and the doc surfaces that must stay in sync (CLAUDE.md, README.md, config.example.{json,yaml}).
Apply when reviewing Go code in this repo for idiom, allocation cost, struct layout, error wrapping, concurrency safety. Triggered by review-style requests on `.go` files, by the `architect` agent when forming verdicts, and by the `developer` agent self-checking before reporting. Loads the project's Go-style rule set.
Apply when reviewing or writing code that touches the IMAP sync flow — anything in internal/client, internal/app/sync.go, internal/app/worker.go, internal/app/show.go. Encodes the non-obvious correctness traps specific to IMAP and to this tool's plan-confirm-execute model.
Apply when auditing changes for security in this repo. Used by the `security` agent. Encodes the threat model (operator trusted, IMAP servers + network partially trusted, no listening sockets) and the standing checklist.