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.
Third rung of the CMB ladder. Reads explicit combined-rate prose into a canonical
CombinedRateProblem or a closed reader refusal; graded by the CMB-a ruler + CMB-b solver via a new
run_reader lane. Off-serving; no router/contemplation/serving/ledger. Claim: 'English prose reads
into a canonical CMB setup or a closed reader refusal.'
Enforces the CMB-a 2x2 domain-entry grid + the deferral taxonomy (rate_unit_mismatch,
combine_mode_ambiguous, missing_second_rate, three_or_more_rates, reciprocal_work_rate_deferred,
clock_interval_deferred, not_combined_rate_shaped). Non-positive-net / non-integer stay the SOLVER's
refusals (the reader parses them). Router-organ hygiene: foreign R1/R2/R3 text steps aside as
not_combined_rate_shaped (the input_shape family), never a substantive boundary (0 breaches on all
36 R1/R2/R3 gold).
THREE adversarial verification rounds found 11 real wrong=0/hygiene hazards a curated-gold lane
cannot surface; all fixed + regression-tested. Root-cause fixes (not point-patches):
- cues are whole-word; difference = a CLEAN fill-vs-drain OPPOSITION classified per rate clause by
the verb in its own lead-in; rate_a=fill/rate_b=drain BY ROLE (a drain listed first still
subtracts); incidental drain nouns / drain-verbs-between-clauses no longer flip the mode;
- query duration + time-query quantity are read only from AFTER the 'how many' question, so neither
a premise number nor a transitional time marker is mistaken for them;
- the rate regex rejects decimals; substantive refusals are gated behind a real combination cue;
combine_mode_ambiguous requires a genuine COMBINED query (a compared pair steps aside);
- sequential segments (each rate carrying its own duration, tolerant of 'also for') step aside.
reader lane 11/0/0 + 7 refused-correct; gold 18/18; 19+17+3 adversarial triggers across 3 rounds;
126 tests (CMB + router/hygiene + R1/R2/R3 readers); serving + siblings unchanged.
Next (ladder): CMB-d router/contemplation wiring -> CMB-e ledger.
solve_combined_rate(CombinedRateProblem) -> int | Refusal over effective_rate = rate_a +/- rate_b.
effective_rate query returns the net (even <=0); quantity/time queries need a positive net rate
(non_positive_net_rate) and exact division (non_integer_solution). Pure integer arithmetic, no
float/Fraction (CMB v1 crosses no units). Off-serving. Graded by a new run_solver lane in
evals/combined_rate_oracle against the committed gold.
Adversarial 5-lens(+adjudicator) verification returned fix_first; both real hazards fixed:
- wrong=0 breach: negative known-slot inputs (time<0/quantity<0) bypassed the eff<=0 guard and
produced negative answers. FIXED UPSTREAM in model.py __post_init__ — rate_a/rate_b and the known
time/quantity are now positive ints, so the illegal state is unrepresentable and the solver can
never receive a negative-yielding path. Added model + gold (cmb-07d eff<0/time) + lane coverage.
- doc overclaim: the solver lane does NOT grade 'two independent paths' (both solver and the
oracle's _canonical_outcome delegate to model.effective_rate). Corrected both docstrings to name
the true anchor (committed gold + inline-computed literal tests) and added a difference-mode
inline-computed test.
R3-vac came back SOLID (separate PR). gold 18/18 (6/5/7); solver lane 6/0 + 5/0; 36 CMB tests;
router-hygiene + serving unchanged.
First rung of the combined-rate ladder, off-serving (imports no generate.derivation /
core.reliability_gate). Claims exactly: the combined-rate setup ruler is defined and
gold-valid. No reader/solver/wiring yet — no capability claim.
- generate/combined_rate_comprehension/: local RateUnit (decoupled from R3), CombinedRateProblem
(two-explicit-rates + per-query-slot guard; effective_rate = rate_a +/- rate_b; non-positive net
left to the solver, not the model).
- evals/combined_rate_oracle/: span-free signature (sum commutative / difference ordered) + a
NON-VACUOUS validator. 17 gold fixtures: 6 solved (full combine_mode x query grid), 4
solver_refuses, 7 reader_refuses (the complete refusal taxonomy + the 2x2 domain-entry grid).
Adversarial 5-lens verification returned fix_first; the validator now cross-checks every solved
gold and solver_refuses reason against the canonical arithmetic (_canonical_outcome) so a
mislabelled / arithmetically-impossible fixture is rejected (meaningful-fail per CLAUDE.md), with
dedicated tests. Added eff<0 and eff=0/time coverage fixtures; removed a dead determinism guard.
gold 17/17 valid; 25 oracle tests; R1/R2/R3 + router-hygiene + serving all unchanged.
Doc: docs/analysis/cmb-a-combined-rate-ruler-2026-06-08.md
