An agent denied `codegraph` on PATH ran `find / -maxdepth 4 -iname "*codegraph*"`,
found the binary, and invoked it by ABSOLUTE PATH — 12 times in one without-arm
run. So block the invocation itself with a PreToolUse hook on Bash, written into
the run's output dir as an artifact alongside the MCP configs rather than as a
repo file.
The pattern matches command positions only, so looking is still allowed and only
using is denied: `grep codegraph src/`, `ls .codegraph` and `which codegraph`
pass through, while `codegraph explore`, `/abs/path/codegraph …`, `cd x &&
codegraph …` and `VAR=1 codegraph …` are refused. run-all.sh proves both
directions at startup and refuses to run if either fails. parse-run.mjs's
detector uses the same rule, so prevention and detection cannot drift — and it no
longer false-positives on the corpus path, which contains the word codegraph.
Verified end-to-end: the without-arm now probes with `ls .codegraph; which
codegraph`, finds nothing usable, and falls back to Read/Bash.
Colby McHenry
e35d4861e0