The causally-correct defence atom proves where the crude one did not

Kev's insight holds, and the data says so cleanly. defense_by_direction PROVES
on hits -- n=528, Brier -0.0034, interval [-0.0059, -0.0009] at the 99.9% level
the cumulative correction now demands -- while team-average defence remains not
proven, its interval still spanning zero. Same signal, same rows, different
unit.

The detail worth keeping is that the causally-correct atom moves the number
LESS THAN HALF as much as the crude one, 0.013 against 0.030, and is the one
that is reliably right. The team average was moving more and knowing less. Big
movement is not evidence of a good factor; it is frequently the tell.

Both halves turned out to be free, as the order expected. Savant's batted-ball
leaderboard carries pull/straight/oppo crossed with ground/air for 609 hitters
-- the statcast leaderboard we already pull does not, it has nineteen columns
and no direction at all -- and the OAA feed already carries each fielder's
position, so per-position defence is a regrouping of last week's ingest rather
than a new source. Verified in production: 609 spray profiles, 31 teams.

Handedness is what joins them and getting it backwards would have been
invisible. Pull for a right-handed hitter is the left side; for a left-handed
hitter it is the right side. A model that ignored `bats` would send half the
league's grounders to the wrong infielders and still look like it was reading
defence, and nothing downstream would have caught it. Switch hitters bat
opposite the pitcher, which this does not resolve, so they are unreadable
rather than guessed.

Unmeasured zones are renormalised away rather than contributing a zero, since a
zero asserts an exactly-average fielder standing there, and coverage states
honestly what share of a hitter's contact we could actually read.

ATOM 2 is input-blocked rather than sample-blocked, and the distinction matters
because waiting will not fix it. The weather free-source check passes --
Open-Meteo is already wired and exposes temperature, wind speed, wind direction
and precipitation -- but those raw fields are collapsed into a single scalar
modifier and wx_forecast is empty on all 1,119 settled rows. Park DIMENSIONS
are not ingested at all; parkFactors holds coefficients, not wall heights or
fence distances. A park-and-weather-to-hit-type conversion needs both, so it is
scoped rather than half-built: retaining the raw weather fields is the cheap
half, dimensions are the missing one.

Proven factors for hits are now pitcher_contact_profile and
defense_by_direction, both pooled; every per-archetype slot remains
sample-blocked.

4,297 tests green (342 suites); web build exit 0.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W1sivYNqY2TS5ftykmHBU9

BUILD-STATE.md

@@ -3,6 +3,27 @@
 ## Last Updated
 2026-08-03
 
+## Session 93 (2026-08-04) — Causally-correct defence atom PROVES ✅
+4,297 tests / 342 suites green, build exit 0. Counter + frozen clusters
+byte-identical.
+- **ATOM 1 BUILT AND PROVEN.** `defense_by_direction` (spray×trajectory ×
+  positional OAA, joined by handedness) **PROVES** on hits: n=528, Brier −0.0034,
+  CI [−0.0059,−0.0009] at 99.9%. Team-average `defense` remains NOT PROVEN.
+  Kev's insight confirmed: the crude operationalization was the problem.
+- **It moves the number LESS (0.013 vs 0.030) and is more reliably right** —
+  bigger movement is often the tell, not the signal.
+- **Zero new sourcing**, as predicted: Savant `leaderboard/batted-ball` has
+  pull/straight/oppo × gb/air (609 hitters, free); per-position OAA is a
+  regrouping of the fielding feed. Prod-verified: spray 609, team_defense 31.
+- **Proven set for hits now: `pitcher_contact_profile` + `defense_by_direction`.**
+  Both pooled; per-archetype still sample-blocked (BOMBER 225–294, GHOST 86–125).
+- **ATOM 2 INPUT-BLOCKED.** Weather free source PASSES (Open-Meteo wired, exposes
+  temp/wind_mph/wind_dir/precip) but raw fields are collapsed to a scalar and
+  `wx_forecast` is 0/1119. **Park dimensions are not ingested at all** — a
+  hit-type conversion needs them. Not half-built.
+- **Next:** retain raw weather fields (cheap), source park dimensions, then build
+  ATOM 2. Sequence/reliever layer stays gated behind proven atoms.
+
 ## Session 92 (2026-08-04) — The two-part factor gate; one factor proves ✅
 4,286 tests / 340 suites green, build exit 0. Counter + frozen clusters
 byte-identical.