Comb pass 2026-05-21.
Item 17 — redundant ``^`` anchors in ``re.match()`` patterns:
``re.match`` anchors at the start of the string automatically, so
the leading ``^`` was documentation-only noise on every pattern
consumed via ``.match()``. Audited each pattern's call site:
* ``_RULES`` (line 144) — used via ``pattern.match(text)`` → strip
* ``_ANAPHORIC_FOLLOWUPS`` — used via ``pattern.match(text)`` → strip
* Module-level ``_COMPARE_RE`` / ``_TRANSITIVE_QUERY_RE`` /
``_FRAME_TRANSFER_RE`` / ``_BELONG_QUERY_RE`` /
``_DECLARATIVE_RELATION_RE`` / ``_HOW_DOES_X_RE`` — all
``.match()`` → strip
* Inline ``re.match`` in ``_strip_confirmation_tail`` → strip
* ``_RESPONSE_MODE_RULES`` — used via ``pattern.search(text)`` →
KEEP ``^`` (``re.search`` does not anchor)
Trailing ``$`` anchors retained throughout because neither
``re.match`` nor ``re.search`` anchors at the end.
A comment block documents the convention so future contributors
understand the ``^`` retain-vs-strip rule.
Tier 5 minor (``chat/runtime.py``):
* Hoisted ``{"is", "are", "was", "were"}`` to module-level
``_BE_FORMS`` constant. Pre-fix ``_prefer_prompt_anchor``
constructed this set on every English turn.
* Replaced the content-token list comprehension + ``[-1]`` slice
with a reverse-iteration short-circuit. Pre-fix the function
materialised the full filtered list just to pick the last
element.
* Cached ``token.casefold()`` once per token via a local in the
loop body. Pre-fix the comprehension called ``.casefold()``
twice per token (against ``_QUESTION_WORDS`` and the inline
aux-verb set).
Validation:
* ``core eval cognition`` byte-identical across all three splits:
public 100/100/91.7/100, dev 100/100/78.6/100, holdout
100/100/83.3/100.
* ``core test --suite cognition`` 120/0/1, ``smoke`` 67/0.
* ``pytest -k intent`` 236/0 (all intent classification tests
pass with the ``^`` removals — the patterns behave identically
under ``re.match`` regardless of the leading anchor).
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