# The fact parser: closed classes against the substring stems they replaced

Measured 2026-08-06 at 22edc3c and its parent 0445693, on the corpus in
`internal/router/factparser_corpus_test.go`. Dated file: it is not edited after
today, and a newer number is a new file.

V-586 rewrote `DefaultFactParser` off hand-written Russian stems onto six closed
classes in `internal/lexicon`. Its commit message reported 64/91 on the RU
routing fixture, unchanged. That number does not bear on the change: the fixture
holds three fact cases and all three miss on intent, so the parser is never
reached. This file measures the parser directly, and runs the LLM arm the
original commit skipped.

**The rewrite is better on the utterances it was designed for and no worse on
the ones it was not.** True positives go 35/40 to 39/40, misfires rejected go
8/15 to 14/15. What neither version has is coverage: of 36 plausible utterances
whose word is in no lexicon set, the substring parser caught 3 by accident and
the closed-class parser catches 0. That is the honest headline. The word list
did not shrink the vocabulary — it never had one — it made the boundary visible.

## The corpus

91 cases, three classes. **True positives** are sentences the owner would say,
with the key that must be written. **Misfires** are sentences the substring
parser wrote a fact for and should not have, including the three hard negatives
the rewrite was argued on. **False negatives** are sentences a reasonable person
would say whose word is in no set at all; `want` is the key a human would
assign, and the ship parser is expected to miss them. They are the measurement
of what a closed class costs, not a bug list.

The old parser is carried in the test file as `legacyFactParse`, copied verbatim
from 0445693, so the comparison reruns:

```sh
deps/go/go/bin/go test -run TestFactParserCorpus -v ./internal/router/
```

## Score

| | true positives | misfires rejected | false-negative cases recovered |
|---|---|---|---|
| old (substring stems, 0445693) | 35/40 | 8/15 | 3/36 |
| **new (closed classes, 22edc3c)** | **39/40** | **14/15** | **0/36** |

Sixteen cases disagree. Eleven of them the rewrite wins, three it loses, and two
are cases neither gets.

**Won.** Every misfire the commit message named — `душа болит`, `в комнате
душно`, `это была беда`, `наша победа`, `на душе легко` — plus `водитель пилота
ждёт`, where two stems in one sentence made the old water arm fire. And five true
positives the stems simply did not list: `перекусил`, `передохнул`, `отдыхаю`,
`пойду спать`, `i showered`. Morphology buys those; a stem list would need a new
entry for each.

**Lost.** `допил воду` is a real regression and the only failing true positive.
The vendored dictionary lemmatises `допил` to `допилить`, to finish sawing —
exactly the collision `drink_verbs` already carries `пил` and `пили` as surface
forms to dodge, left unhandled for the prefixed form. `допить` is in the set and
the sentence still misses. It is flagged `broken` in the corpus rather than
fixed, because this branch measures.

`был в душе` and `после душа полегчало` are the price of matching the shower set
exactly. The dictionary makes `душ` and `душа` one word, so a lemma test cannot
tell a shower from a soul; exact matching keeps `на душе легко` out and loses
the oblique cases of the real noun with it. The old parser got both by accident,
along with the soul. That trade is right — writing a shower fact when he said
his soul feels light is worse than missing one — but it is a trade and the two
rows are what it costs.

`недоспал` is the third loss and the least defensible: the old substring `спал`
caught it, and `недоспать` is in no set.

**Neither.** `обеденный перерыв отменили` — a cancelled lunch break — is a fact
for both parsers, `meal` for the old one off the adjective and `break` for the
new one off `перерыв`. Nothing in either design reads the cancellation.
`дрых до обеда` is scored `meal` by both, because the meal arm runs first and
`обеда` is in it, which is not wrong so much as beside the point.

## The false-negative surface

This is the half the routing fixture cannot see and the half that decides
whether the design holds. 36 cases, 0 recovered:

- **water** — `выпил чаю`, `глотнул воды`, `хлебнул воды`, `выпил стакан`,
  `i hydrated`, `finished my bottle of water`. The water arm needs a noun AND a
  verb, so an elided noun or an unlisted verb drops the whole capture.
- **meal** — `ем суп`, `съел бутерброд`, `наелся`, `пожрал`, `полдник был`,
  `snack`, `supper`, `brunch`, `i eat now`. `есть` is deliberately absent for
  `есть новости по бэкапу`, and `ем`, its most ordinary spoken form, goes with it.
- **shower** — `помылся`, `сходил в ванную`, `искупался`, `i am showering`,
  plus the two oblique cases above.
- **break** — `сделал передышку`, `перекур`, `полежал немного`, `сделал паузу`,
  `i took five`, `resting now`.
- **sleep** — `вздремнул`, `прикорнул`, `дрых`, `недоспал`, `лёг в двенадцать`,
  `сон был короткий`, `i napped`, `took a nap`.

None of these are exotic. They are the second and third word a person reaches
for, and every one of them is a fact the owner stated and Maven silently did not
record. A silent miss is the worst failure mode this parser has: he said it, she
heard it, nothing was written, and nothing told him.

## The routing fixture, LLM arm

The arm 22edc3c skipped. `MAVEN_LLM_URL` points the harness at any llama-server;
the previous run reported none reachable, which was the shell's `HTTP_PROXY` and
not the network. Run against **gemma-4-12B-it-qat-UD-Q4_K_XL on the workstation
at `192.168.1.105:8080`**, the same box as the 02-08 measurement, with
`NO_PROXY=192.168.1.105`:

```sh
NO_PROXY=192.168.1.105 no_proxy=192.168.1.105 \
  make eval-models MAVEN_LLM_URL=http://192.168.1.105:8080
```

| | full | intent-only | p50 |
|---|---|---|---|
| llm-only, 0445693 | 51.6% (47/91) | 82.4% | — |
| llm-only, 22edc3c | 52.7% (48/91) | 83.5% | 341ms |
| cascade+llm, 0445693 | 85.7% (78/91) | 93.4% | — |
| **cascade+llm, 22edc3c** | **86.8% (79/91)** | **94.5%** | 334ms |

One case either way, both directions, and the failing set is identical between
the two commits. That is run-to-run variance on a sampling model, not a signal.
The parser change is invisible to the routing fixture on the LLM arm for the
same reason it is invisible on the classifier arm: the three fact cases miss on
intent and the parser is never called. Do not read these rows as evidence about
the parser. They are evidence that the fixture cannot answer the question, which
is why the corpus above exists.

## Verdict

The closed-class rewrite holds up as a rewrite. It is strictly better than what
it replaced on both classes anyone argued about, and the one regression
(`допил`) and one bad trade (the oblique `душ`) are both dictionary collisions
rather than design faults.

It does not hold up as an answer. A closed class is the right mechanism for a
set that is actually closed — interrogatives, weekdays, cardinals — and
"the words a person uses to say he ate" is not that set. The corpus puts a
number on it: 36 ordinary sentences, 0 recovered, and every new one costs a
lexicon edit by whoever notices. The three mechanisms CLAUDE.md names do not
contain the right one for this job. The embedder-topic mechanism is the closest
fit and is wrong too, because this is slot extraction rather than aboutness.

This is a case for the V-546 slot-tagging head. Self-care facts are a bounded
key space (five keys) over unbounded surface forms, which is exactly what a BIO
tagger on e5-small is for: it generalises to `вздремнул` without anyone adding
`вздремнуть` to a list, and max softmax gives the confidence the parser's
hardcoded `true` does not have. Until it lands, the closed classes are the
correct floor and the 36 rows above are the size of the gap they leave.

## The corpus, case by case

| utterance | class | want | old (substring) | new (closed class) |
|---|---|---|---|---|
| `выпил стакан воды` | tp | water | water | water |
| `попил воды` | tp | water | water | water |
| `я попил водички` | tp | water | water | water |
| `пью воду` | tp | water | water | water |
| `воду пил уже` | tp | water | water | water |
| `допил воду` | tp | water | water | — **≠** |
| `запил таблетку водой` | tp | water | water | water |
| `drank water` | tp | water | water | water |
| `i drank some water` | tp | water | water | water |
| `поужинал` | tp | meal | meal | meal |
| `я пообедал` | tp | meal | meal | meal |
| `позавтракал кашей` | tp | meal | meal | meal |
| `перекусил бутербродом` | tp | meal | — | meal **≠** |
| `покушал` | tp | meal | meal | meal |
| `поел супа` | tp | meal | meal | meal |
| `обед был в час` | tp | meal | meal | meal |
| `ужинать буду позже` | tp | meal | meal | meal |
| `i ate` | tp | meal | meal | meal |
| `had lunch` | tp | meal | meal | meal |
| `dinner done` | tp | meal | meal | meal |
| `принял душ` | tp | shower | shower | shower |
| `сходил в душ` | tp | shower | shower | shower |
| `душ принят` | tp | shower | shower | shower |
| `ополоснулся душем` | tp | shower | shower | shower |
| `took a shower` | tp | shower | shower | shower |
| `i showered` | tp | shower | — | shower **≠** |
| `сделал перерыв` | tp | break | break | break |
| `отдохнул полчаса` | tp | break | break | break |
| `передохнул немного` | tp | break | — | break **≠** |
| `отдыхаю` | tp | break | — | break **≠** |
| `был перерыв на обед` | tp | meal | meal | meal |
| `took a break` | tp | break | break | break |
| `спал восемь часов` | tp | sleep | sleep | sleep |
| `спала плохо` | tp | sleep | sleep | sleep |
| `поспал днём` | tp | sleep | sleep | sleep |
| `выспался наконец` | tp | sleep | sleep | sleep |
| `проспал будильник` | tp | sleep | sleep | sleep |
| `пойду спать` | tp | sleep | — | sleep **≠** |
| `slept 8 hours` | tp | sleep | sleep | sleep |
| `i slept badly` | tp | sleep | sleep | sleep |
| `пилот сказал что вылет через час` | misfire | — | — | — |
| `водитель уже подъехал` | misfire | — | — | — |
| `надо заводить машину` | misfire | — | — | — |
| `душа болит` | misfire | — | shower | — **≠** |
| `в комнате душно` | misfire | — | shower | — **≠** |
| `это была беда` | misfire | — | meal | — **≠** |
| `наша победа` | misfire | — | meal | — **≠** |
| `пила лежит в гараже` | misfire | — | — | — |
| `водитель пилота ждёт` | misfire | — | water | — **≠** |
| `обеденный перерыв отменили` | misfire | — | meal | break **≠** |
| `есть новости по бэкапу базы` | misfire | — | — | — |
| `напоминания на завтра есть` | misfire | — | — | — |
| `на душе легко` | misfire | — | shower | — **≠** |
| `пилил доску весь вечер` | misfire | — | — | — |
| `поставь будильник на завтра` | misfire | — | — | — |
| `выпил чаю` | fn | water | — | — |
| `глотнул воды` | fn | water | — | — |
| `хлебнул воды` | fn | water | — | — |
| `воды хлебнул из бутылки` | fn | water | — | — |
| `выпил стакан` | fn | water | — | — |
| `i hydrated` | fn | water | — | — |
| `finished my bottle of water` | fn | water | — | — |
| `ем суп` | fn | meal | — | — |
| `съел бутерброд` | fn | meal | — | — |
| `наелся` | fn | meal | — | — |
| `пожрал` | fn | meal | — | — |
| `полдник был` | fn | meal | — | — |
| `i had a snack` | fn | meal | — | — |
| `having supper` | fn | meal | — | — |
| `brunch was good` | fn | meal | — | — |
| `i eat now` | fn | meal | — | — |
| `был в душе` | fn | shower | shower | — **≠** |
| `после душа полегчало` | fn | shower | shower | — **≠** |
| `помылся` | fn | shower | — | — |
| `сходил в ванную` | fn | shower | — | — |
| `искупался` | fn | shower | — | — |
| `i am showering` | fn | shower | — | — |
| `сделал передышку` | fn | break | — | — |
| `перекур` | fn | break | — | — |
| `полежал немного` | fn | break | — | — |
| `сделал паузу` | fn | break | — | — |
| `i took five` | fn | break | — | — |
| `resting now` | fn | break | — | — |
| `вздремнул` | fn | sleep | — | — |
| `прикорнул на диване` | fn | sleep | — | — |
| `дрых до обеда` | fn | sleep | meal | meal |
| `недоспал` | fn | sleep | sleep | — **≠** |
| `лёг в двенадцать` | fn | sleep | — | — |
| `сон был короткий` | fn | sleep | — | — |
| `i napped` | fn | sleep | — | — |
| `took a nap` | fn | sleep | — | — |
`≠` marks a disagreement. `—` is no fact written.