sapling

Create a Mononoke server-side hook with 3-diff split (tests, wiring, implementation), unit tests, and integration tests

Add or review structured error logging in EdenFS daemon (C++) — the ErrorLogger / EdenErrorInfo system that feeds the edenfs_errors table. Use when writing a catch block or handling a boxed/async exception (folly::Try / exception_wrapper / .thenError), instrumenting a failure path, or debugging a wrong stack trace or wrong component. Covers throw-site trace rules, component choice, errorType, noise filtering, gating, and testing.

Triage systemd-managed EdenFS issues on Linux devservers and OnDemands. Use when investigating EdenFS service failures, unexpected restarts, systemctl errors, edenfs_upgrade/edenfs_restarter problems, or when a user reports EdenFS is down on a systemd-enabled host. Also use when someone asks how systemd-managed EdenFS works, how to monitor it, or how to check its health. Use when asked to build a timeline of EdenFS lifecycle events, show edenfs restart history, or understand how edenfs reached its current state. Trigger on mentions of edenfs systemd, edenfs@ service, edenfs_upgrade timer, edenfs auto-restart, eden status --debug, systemctl edenfs, edenfs lifecycle management, edenfs timeline, edenfs restart history, or "what happened to edenfs".

Load FIRST before searching code in eden/. Contains component-to-file maps, key type names, and architecture diagrams for EdenFS, Sapling, and Mononoke. Tells you exactly which files to read for any task. References contain per-component quick reference tables.