Files
hermes-agent/tools
Teknium cd7150a195 perf(approval): precompile DANGEROUS_PATTERNS and HARDLINE_PATTERNS (#17206)
detect_dangerous_command() and detect_hardline_command() were calling
re.search(pattern, text, re.IGNORECASE | re.DOTALL) inline — Python's
re._cache (512 patterns) amortizes compile cost on the warm path, but:

  1. The first terminal() call per process pays the full compile fan-out
     for all 59 patterns (12 HARDLINE + 47 DANGEROUS). Measured at
     ~2.6 ms per detect_dangerous_command() call after re.purge().
  2. The re._cache is LRU — unrelated regex work elsewhere in the agent
     (response parsing, text normalization, etc.) can evict our patterns
     and silently re-compile them on the next terminal() call.

Precompiling at module load eliminates both costs:

  detect_dangerous_command:
    cold  2.613 ms  →  0.298 ms   (-88%)
    warm  0.042 ms  →  0.004 ms   (-90%)
  detect_hardline_command:
    cold  ~0.6 ms   →  0.006 ms
    warm  0.011 ms  →  0.002 ms

Savings are per terminal() call. Agents with heavy terminal use see
compound savings; the bigger value is the stability guarantee (no
re._cache eviction can silently re-introduce the 2.6 ms cold cost
mid-session).

Implementation:
- HARDLINE_PATTERNS_COMPILED and DANGEROUS_PATTERNS_COMPILED built at
  module load from the existing (pattern, description) tuples, using
  shared _RE_FLAGS = re.IGNORECASE | re.DOTALL.
- detect_* functions now iterate the compiled list and call pattern_re.search(text).
- Original HARDLINE_PATTERNS and DANGEROUS_PATTERNS lists kept as-is
  (other code in the file uses them for key derivation /
  _PATTERN_KEY_ALIASES).

Verified:
- 160/161 tests/tools/test_approval*.py pass (1 pre-existing heartbeat
  test flake on main).
- 349/349 tests/tools/ 'approval or terminal or dangerous' pass.
- Live hermes chat smoke: 3 benign terminal commands + 1 rm -rf /tmp/
  (clarify prompt fired — approval path still works) + 1 sudo (sudo
  password prompt fired — DANGEROUS pattern match still works). 23
  log lines in the smoke window, zero errors.

Co-authored-by: teknium1 <teknium@users.noreply.github.com>
2026-04-28 18:44:14 -07:00
..