The Scott Logic post ("Ponytail? YAGNI!", see #126) argued a bare one-liner
prompt matches ponytail because both shrink the line count. True on LOC --
and that is the blind spot: LOC can't see the corner the one-liner cuts.
The canonical lazy email validator uses re.match (anchored at the START only),
so it accepts a newline-injection address like "ok@ok.com\n<payload>" -- a real
header/log-injection vector. ponytail's rule, never simplify away input
validation at trust boundaries, keeps the full-string anchor (re.fullmatch).
Same shortness, one keeps the guard.
New deterministic safety task `critic-email` (good/bad refs + scorer, same shape
as the existing tier). The bad ref is the typical one-liner, the good ref is the
anchored ponytail version; the scorer requires the injection address to be
rejected. Verifiable with no API key via `run.py --selftest`.
Refs #126
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Rebuild the benchmark to the standard #126 asked for: real headless Claude Code
sessions (not a bare model) editing a real public repo
(tiangolo/full-stack-fastapi-template @ cd83fc1, MIT), fair arms (baseline,
caveman, ponytail, and the "YAGNI + one-liners" prompt), n=4, Haiku 4.5. LOC is
the git diff; the safety tasks execute the produced code against adversarial
input.
Results: ponytail -54% LOC mean (up to -94% on over-build features like the
date/color picker), -22% tokens, -20% cost, -27% time, and never more than
baseline; 100% safe vs the one-liner prompt's 95% (it dropped a path-traversal
guard once). caveman writes less code but spends more tokens.
Also fixes a baseline-contamination bug (the ponytail plugin's SessionStart hook
fired on every arm; now isolated with --setting-sources project,local + per-arm
--plugin-dir) and a Windows subprocess-timeout hang.
Lead both READMEs with the agentic numbers; demote the single-shot 80-94% to a
labelled "isolated generation" note; supersede the contaminated 2026-06-17
writeup. Dead react-app fixture left untracked.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
