Capn Hook gives coding agents local memory that expires when files change

Capn Hook is a local memory layer for coding agents. It lets an agent chart hard-won codebase discoveries as small question-to-file entries, then ask that local chart before repeating the same repository search in a later session.

The useful part is its stale-answer model: every charted answer is tied to backing file hashes. If a referenced file changes or disappears, Capn Hook prunes the entry before it can be used again. That makes it a better fit for fast-moving codebases than a static notes file or a giant persistent context dump.

Why it is worth a bookmark: it integrates with Claude Code and Codex through session-start hooks, stores local markdown entries under .capn/, can run semantic recall through QMD, and offers a deterministic BM25 path with capn init --no-embedding. The README also publishes an eval claim across 60 real developer questions, but treat that as vendor evidence until you test it on your own repository.

Use it if your agents repeatedly rediscover routing, billing, auth, deployment, or test-layout facts. Skip it if your team does not want agent hooks modifying local project setup, or if you cannot review what gets saved under .capn/.