Rebuilding corpus fast-path metadata from the real router moves the slice-22 1652-row five-way numbers by ≤2pp (heads 0.772→0.751 acc, e5-linear 0.722/0.712→0.720/0.731 macro-F1) and every aggregate slice-22 conclusion survives, so the learned non-action router investigation is closed as run; the residual pool is 1509 non-action + 720 action OOD rows, and the deterministic hash-classifier floor collapses to acc 0.066 because its earlier 0.171 was almost entirely the 185 rows the stale mirror had mislabelled as residual while the real grammars already resolve them

Date: 2026-09-08 · Task: slice 23 (fast-path metadata reconciliation; postscript to the accepted slice 22, task/725) · Box: workpc, Arch, RX 7900 GRE, 32 GB · Build: internal/router/semantic/fastpath.go + cmd/semantic-router-experiment/slice23/ (Go 1.25.12) + slice23_emit.py/slice23_main.py in the frozen venv /tmp/mvn-exp-venv (sklearn 1.9.0); ONNX via MAVEN_ONNX_LIB pointing at the venv's libonnxruntime.so.1.29.0.

Replaces the corrected-population numbers in slice 22. The slice-22 file keeps its role for the run itself; its 1652-row pool is no longer the current measurement population.

0. What changed and what did not

The corpus's fast_path_resolved flag was stamped by a hand-written regex mirror (classifyFastPath in cmd/corpus-factory/main.go) that drifted from the stage-0 grammars. Slice 22 noticed 185 residual rows resolving at runtime. This slice makes the flag a derivation from the real router and re-measures.

corpus 3025 rows, dev pool 2490, frozen holdout 535            unchanged
dataset_hash b27fd48f478ca477cab1e59773bb353a                  unchanged (texts)
fast_path_resolved      82 → 271   (dev 72 → 261, frozen 10, preserved)
residual                2943 → 2754 (dev 2418 → 2229, frozen 525, preserved)
residual non-action pool 1652 → 1509
  knowledge 715→558 / memory_write 553→541 / system 184→220 / conversation 93→91 / uncertain 107→99
action OOD probes        766 → 720
residual dev pool folds {0:317,1:140,2:410,3:408,4:377} → {0:247,1:111,2:373,3:386,4:392}

The rebuild changed exactly the derived fields on exactly the 277 dev rows that disagree with the router: 0 rows differ in text, route, source, source_id, split_group, or the non-router_residual tags. The 22 stale frozen rows (see §1) are preserved verbatim per the merge rule — reported, never silently rewritten.

1. The drift, decomposed (299 disagreements across 3025 corpus rows)

cmd/semantic-router-experiment/slice23 runs DeriveFastPath (the production TryFastPath over StageZeroGrammars with the experiment act allowlist) on every row and attributes the winner. Output: /tmp/mvn-s23/drift.json.

mirror_missed (stored residual, runtime resolves)      249
  dev 233  = 185 non-action + 48 action
    dev non-action by grammar: calendar-query 66, definition-query 30,
      narrative-query 26, task-capture 12, agenda-query 9, task-list-query 9,
      plan-day-query 8, ambiguous-fragment 7, time-query 6, rest-of-day 5,
      event-time 4, possession-statement 2, reminder-wakeword 1
  frozen 16 (possession 6, implicit-elapsed 3, wakeword-act 2, + 5 singles)
claimed_fast_now_miss (stored fast, runtime declines)   50
  dev 44 (system 42, action 2) + frozen 6 (memory_write "note: " rows)
  every one has ≥1 stage-0 grammar matching its shape and declining the build;
  none is a "no grammar matches" row

The 185 dev non-action mirror_missed rows are byte-identical in count and route split to the slice-22 harness's grammar_hits_in_pool: 185 (knowledge 157, memory_write 12, system 6, conversation 2, uncertain 8) — a strong cross-check that DeriveFastPath equals what the slice-22 harness measured through Route().

Root cause, two mechanisms:

Grammar coverage grew after the corpus froze. calendar-query (67), definition-query (31), narrative-query (27), task-status (24), agenda-query (9), possession-statement (8), plan-day-query (8), event-time-query (4) and the rest are current stage-0 rules with no counterpart in the mirror. The mirror ever only knew a fixed verb list.
The mirror's verb lists over-stamped. The 50 claimed_fast_now_miss rows ("покажи uptime", "note: кран на кухне капает", "what's the date сегодня") matched toolAliasRe/captureVerbRe/timeQueryRe, but no real grammar accepts them: rules like task-list-query/list-capture use a catch-all (?s)^\s*(.+)$ pattern with the real gate in Build, which declines. The mirror had no concept of a build gate.

The frozen 22 (16 + 6) are the same two mechanisms on holdout families, including three ru_routing_v1 rows ("что у меня стоит в календаре на послезавтра", "расскажи про битву при Ватерлоо", "кто такой Линус Торвальдс?") now resolved by calendar/narrative/definition grammars.

2. The authoritative derivation

internal/router/semantic/fastpath.go (non-test) owns:

ExperimentActVerbs() — the 18 verbs formerly duplicated in helpers_test.go, legacy_build.go and heads_main.go; now one non-test list, so propagation can never drift from measurement.
DeriveFastPath(text) FastPathOutcome{Matched, Grammar} — builds the exact router the legacy baseline measures (router.StageZeroGrammars + the experiment act matcher + StubDateTimeParser/DefaultFactParser) and runs TryFastPath(NormalizedInput{Text, MatchText: NormalizeMatchText(Text)}). Grammar attribution replays the ordered first-accept walk the router performs, including wake-stripped alternates and build-declined fall-through.

Consumers:

cmd/corpus-factory stamps fast_path_resolved/router_residual from DeriveFastPath; the regex mirror is deleted.
cmd/merge-corpus validates every v2 row against the derivation and fails on a stale value; frozen holdout drift is reported only.
internal/router/semantic/fastpath_invariant_test.go asserts every dev row satisfies fast_path_resolved == DeriveFastPath(text).Matched; frozen rows are exempt by the merge rule.

3. Rebuild proofs

factory v2:  3008 rows, text-set identical old↔new
             diff = exactly the fast-path fields on 296 rows; 0 other diffs
merge:       v2 dev rows 2490 all validated against the router (0 stale)
             frozen 535 preserved; 22 drift rows reported, none rewritten
v1 embedded: 3025 rows, text-set identical; dataset_hash unchanged
             diff = fast-path fields on the 277 dev rows; 0 other diffs
embeddings:  regenerated (fast_path_count 82 → 271, residual_count 2943 → 2754)
             all 3025 vectors differ by ≤ ~0.02 max-abs from the slice-22 file
             (onnxruntime build noise); on the same 1509 pool the e5-linear
             score moves only −0.0014 acc / −0.0002 macro-F1 (C=10), i.e. the
             population effect, not the embedding noise, drives every delta

4. Baseline deltas on the corrected population

measure	slice 22 (n=1652)	slice 23 (n=1509)
legacy hash floor	0.1707 / 0.1202 (illegal 3)	0.0663 / 0.0265 (illegal 2)
deployed cascade (heads)	0.7724 / 0.7150 (illegal 143)	0.7515 / 0.7065 (illegal 142)
e5-linear C=10	0.7222 / 0.7117	0.7203 / 0.7310
centroid (cosine)	0.6731 / 0.6494	0.6753 / 0.6494
sparse word+char (both)	0.6247 / 0.4463 (vocab 6951)	0.5991 / 0.4588
majority	0.4328 / 0.1208	0.3698 / 0.1080
leave-one-family-out	0.6824 / 0.1499, 53 fm	0.6863 / 0.1519, 53 fm
fact holdout	0.0180 (n 389)	0.0077 (n 389)
world holdout	0.7622 (n 143)	0.6552 (n 87)
recall holdout	0.7632 (n 114)	0.5667 (n 90)
calendar holdout	0.6304 (n 92)	0.5185 (n 27)
K/MW water pairs	0.863 (480), +0.298	0.850 (480), +0.275
K/MW homelab pairs	0.106 (180), −0.228	0.072 (180), −0.247
K/MW task pairs	0.735 (720), +0.122	0.403 (216), −0.095
uncertain OOF P/R/F1	0.758 / 0.701 / 0.728	0.734 / 0.697 / 0.715
action OOD swallowed	knowledge 370, mw 347 of 766 (conf>0.9: 0.060)	knowledge 364, mw 312 of 720 (conf>0.9: 0.056)
grammar hits in pool	185 / 1467 pure	0 / 1509 pure

The hash floor's collapse is explained structurally: the 185 removed rows were nearly all the hash classifier's correct knowledge hits (correct predictions 282 → 98, a one-to-one loss with the drift), so the deterministic floor "resolves" the same rows the real grammars already own.

5. The decisions requested

Drift decomposition — §1; 299 = 249 + 50; the slice-22 185 reproduces exactly.
Root cause — §1; coverage growth + build-gate over-stamp, neither visible to a regex mirror.
Authoritative derivation — §2; DeriveFastPath on the standard experiment router; duplicated act list removed.
Corpus-builder change — §2-§3; factory stamps from the router, merge validates (fail on stale) + reports frozen drift, invariant test enforces it.
Corrected counts — §0; fast 82→271, residual 2943→2754, pool 1652→1509 non-action + 720 OOD; dataset hash unchanged proves only the derived field moved.
Baseline deltas — §4; all ≤2pp on the head scores; hash floor collapses because its output was the drifted rows.

6. Conclusion survival and the gate

Every aggregate slice-22 conclusion is unchanged on the corrected population:

e5-linear ≈ deployed cascade. e5 0.7203 vs heads 0.7515 acc (slice 22: 0.7222 vs 0.7724); macro-F1 e5 0.7310 now exceeds heads 0.7065. The ≈3pp gap stands; a head on frozen e5 embeddings adds nothing a linear probe lacks.
Cross-family transfer is structurally absent. LOFO macro-F1 0.1519; fact holdout 0.0077; system/conversation/uncertain holdouts 0.0000.
K/MW is a deterministic semantic defect. Homelab pairs still order backwards (0.072, margin −0.247); task pairs now order backwards too (0.403, margin −0.095, pairs 720→216 as the calendar/task queries leave the pool). Water stays right (0.850). No learned head fixes this at the margin.
The deterministic floor is not a baseline. acc 0.0663 ≈ predicting uncertain for everything.
Action OOD is still swallowed. 676 of 720 (93.9%) land in knowledge/memory_write at argmax; conf>0.9 5.6%.

Decision gate from the brief: conclusions materially the same. The learned non-action-router investigation is closed; no new representation or head is justified. Next slice: the note-vs-recall disambiguator (the one genuine residual deterministic defect the K/MW numbers keep surfacing).

Artifacts

Re-run (corrected population):

go run ./cmd/semantic-router-experiment/slice23/ -out /tmp/mvn-s23/drift.json
go build -o /tmp/mvn-s23/s23 ./cmd/semantic-router-experiment/slice22/
MAVEN_ONNX_LIB=…/libonnxruntime.so.1.29.0 /tmp/mvn-s23/s23 -mode legacy -pool /tmp/mvn-s23/pool.json -out /tmp/mvn-s23/legacy.json
MAVEN_ONNX_LIB=… /tmp/mvn-s23/s23 -mode heads -pool /tmp/mvn-s23/pool.json -out /tmp/mvn-s23/legacy_heads.json
python3 slice23_emit.py            # → /tmp/mvn-s23/{pool,ood,stats}.json (1509/720)
MAVEN_ONNX_LIB=… python3 slice23_main.py   # → /tmp/mvn-s23/results.json

Corpus rebuild (proofs in §3): corpus-factory -out /tmp/corpus_v2.json, then merge-corpus -v1 corpus_v1.json -v2 /tmp/corpus_v2.json -out corpus_v1.json (identity of the change verified against /tmp/mvn-s23/corpus_v1.old.json). Embedding regeneration (noise isolation against /tmp/mvn-s23/embeddings.old.json).

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