# Bug Report: harden-parse-verdict

Bug_find phase observations. Each non-blocking unless marked BLOCKER.

## O1 — `bool(raw_pass.strip())` fallback for "0" / "1" strings

For `{"pass": "0", "score": 0.5}`, the new path strips → "0" → not "true"/
"false" → `bool("0")` = True (non-empty string is truthy).

Pre-fix: `bool("0")` was also True (same).

This is **consistent with v1** — no behavior change. A verifier emitting
`pass: "0"` intending "false" gets `True` in v1 AND in the hardened
implementation. The SPEC says non-`true`/`false` strings fall through to
`bool(...)`, which is truthy for non-empty. Not a regression.

**Not a bug** — documented behavior per SPEC R1 + D-V1. If users want
strict numeric-string handling, that's a separate future task (out of
scope for v1.1 harden-parse-verdict).

## O2 — `float("nan")` serializes back as `NaN` to `.state.loop`

When the verifier emits `NaN` as the score, `parse_verdict` returns
`score=0.5` (without writing to disk by itself). But this score is part
of `verdict` which gets written via `_write_state_loop(loop_path, state)`
into `.state.loop` as JSON. Since the clamp converts NaN to 0.5 BEFORE
the verdict is stored, `.state.loop` gets `0.5`, not `NaN`. No NaN leaks
into the loop state.

**Not a bug** — confirmed via tracing: `parse_verdict` returns the clamped
dict; `cmd_tick` then stores `state["last_verdict"] = verdict` (a clean
dict with `score: 0.5`); the JSON round-trip is clean.

## O3 — `_gate_score_plateau`'s threshold unaffected

`_gate_score_plateau` (status.py) reads `score_history` and decides a halt
when last N scores are within some delta. With clamped scores, the plateau
detection range is now strictly `[0, 1]` instead of `[any, any]`. Brief
review:

- Pre-fix: a verifier could emit `score: 1.5` across N ticks; plateau
  detection sees a flat line at 1.5; halt fires. Expected behavior.
- Post-fix: the same verifier's 1.5 clamps to 1.0 across N ticks; plateau
  sees flat line at 1.0; halt fires. Same outcome.

- Pre-fix: a verifier emits alternating `0.9` and `1.1`; plateau sees a
  bimodal history [0.9, 1.1, 0.9, 1.1] — NOT plateau (variation > epsilon).
- Post-fix: alternating `0.9` and `1.0` (1.1 clamps to 1.0); plateau sees
  [0.9, 1.0, 0.9, 1.0] — still variation above a small epsilon — still NOT
  plateau. Same outcome in this scenario.

Edge case: a verifier emits all `1.0` and `0.99` (vs 1.0 and 1.0 clamped).
The clamp DOES change plateau detection in this case — `1.0 1.0 1.0`
looks more plateau-like than `1.0 0.99 0.99`. Could cause halt earlier than
prior. Documented as a desirable side effect (clamp reduces the verifier's
untrustworthiness from inflating scores; plateau detection is more
honest).

**Not a bug** — improved behavior. Documented in CHANGELOG.

## O4 — Verifier prompt hasn't been updated

`prompts/loop-verifier.md` still asks the model to emit JSON with
`"pass": true/false` and `"score": 0.0-1.0`. The runner now defensive-coerces,
but the prompt's contract is unchanged. Was the prompt already
JSON-typed-booleans-only? Let me check.

**`prompts/loop-verifier.md` review**: still says "Output: strict JSON, no
prose" with example shape. The prompt explicitly tells the model to emit
JSON booleans — no mention of string-typed `pass`. So the v1 contract was
strict; the O6 finding was a defense-in-depth concern, not a present-fault.
The harden task adds belt-and-suspenders without changing the contract.

**Not a bug** — the prompt remains authoritative. No edit needed.

## Verdict

**No blockers.** Proceed to adversarial_bug_find.