calldiff

calldiff answers "who calls whom", read straight from a git tree. It is syntactic (tree-sitter, no type checking), so it is fast and needs no build, and it will miss dynamic dispatch. Treat its output as evidence that narrows attention — never as proof that nothing else is affected.

Installed globally: run calldiff, not npx calldiff.

The three modes worth using

command	use for
`calldiff reach --entry <fn> --to <symbol> --locs`	blast radius. Every call path from an entrypoint down to a target, each hop with `file:line`. Use before editing a shared function, and to answer "can this change reach X".
`calldiff diff --file <path>`	structural review of one changed file: which calls this change added, removed, or swapped, shown in tree context.
`calldiff tree --file <path>`	a call outline of one module, when you need its shape before reading it.

Add --max-depth <n> when a tree runs long. --locs is cheap and almost always worth it — line numbers make the output actionable.