When a command exits non-zero, scan the first 4KB of output for
well-known failure shapes and attach one short, actionable recovery
hint to the tool result ('hint' field):
- gh 'Unknown JSON field' (9.2k occurrences in a 250k-call window)
- git merge conflicts (1.2k) — stop verbatim retries
- command not found (1.0k), incl. python->python3 and pip->pip3
- ModuleNotFoundError (739) — venv activation guidance
- 'already exists' (633), gh rate limits (133), permission denied
- exit-code-only tier: 124 timeout, 126 not-executable, 137 SIGKILL
Hints are suppressed when the existing exit_code_meaning tier already
explains the code (grep=1 etc). Pattern order = production frequency
from state.db mining; first match wins; pure function, no I/O.
Teknium