Module intercept 

mushroomdb intercept — the optional PreToolUse hook body (experimental).

Claude Code runs this before a Grep, handing it the tool call as JSON on stdin. When the pattern is a bare identifier the graph already holds as a symbol, the search is a question explore answers exactly — the definition, the callers and the callees, in one reply — where the grep returns every line the name appears on and leaves the reading to the model. Exit 2 with a message on stderr is Claude Code’s way of saying so: the tool call is blocked and the message reaches the model.

Why it is this conservative

A hook that blocks a search wrongly is far worse than one that never fires, so decide answers Some only where the graph provably has the better answer:

• The pattern must be a bare identifier ([is_identifier]). Anything with regex syntax in it — ., *, |, an anchor, a space — is a search, not a name, and the graph has no opinion about it.
• It must be at least three characters. id may well be a symbol, and a grep for it is still almost certainly not a request for that symbol.
• It must resolve to at least one Symbol node, through the same lookup context uses for a bare name, so the explore the message points at is one that will actually answer.

Everything else — a store that will not open, a payload that will not parse, a missing field — is silence and exit 0, like every other hook this binary writes.

Functions

decide

Whether this Grep should be redirected, and what to say if so.

run_intercept

The whole hook body: parse the payload, open the store, decide.