The mandatory lookback before CMB-d (3+ PRs on one surface; next-phase boundary). A 5-dimension
read-only fan-out audit over the 10-item checklist found the CMB-a/b/c substrate composes cleanly:
25 solid / 4 drift / 8 gap / 1 reader hazard. Doc:
docs/analysis/cmb-lookback-review-2026-06-08.md.
Fixes the one real hazard (H3): a query attributing the answer to a SINGLE agent ('how many words
does Alice type' with a distractor second rate) wrongly claimed the substantive
combine_mode_ambiguous — a hygiene over-claim that would corrupt the shared router in CMB-d. The
combined-query gate now excludes single-agent 'does <Agent>' attribution (_SINGLE_AGENT_QUERY) and
steps aside as not_combined_rate_shaped; the genuinely-combined forms ('do they' / 'are produced' /
'does it') still yield combine_mode_ambiguous. Pinned by gold cmb-16 + a reader test.
The review also resolves the CMB-d failure-family classification (input_shape:
not_combined_rate_shaped; must_remain_refused incl. rate_unit_mismatch — DECISIVELY, the reader has
no dimension representation so it cannot tell convertible from incompatible units; proposal_allowed:
combine_mode_ambiguous, missing_second_rate) and enumerates the live CMB-d registry preconditions
(not_combined_rate_shaped mapping, rate_unit_mismatch/non_integer_solution string collisions,
non_positive_net_rate family, Organ/ALL_REASONS extension). Provenance false-alarm (stale local main
checkout) noted + verified against origin/main.
gold 19/19 (6/5/8); reader 11/0/0 + 8 refused-correct; solver 6/0 + 5/0; 0 hygiene breaches; 123
tests; serving + R1/R2/R3 unchanged.
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