diff --git a/BUILD-STATE.md b/BUILD-STATE.md
index 2574dcc..d5d2622 100755
--- a/BUILD-STATE.md
+++ b/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.
diff --git a/CLAUDE.md b/CLAUDE.md
index 17ecccc..a95af46 100755
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -1689,6 +1689,36 @@ phased plan in the Session-57 conversation / BUILD-STATE Next section).
   `parkFactors.STAT_BASE` maps `hits → run_base`, so there is **no hits-specific
   park factor**: a park that turns outs into hits without scoring is invisible.
 
+## Causally-correct atoms (Session 93 — non-obvious)
+- **KEV'S INSIGHT IS CONFIRMED ON DATA: crude operationalizations under-prove.**
+  `defense_by_direction` **PROVES** (n=528, Brier −0.0034, CI [−0.0059,−0.0009]
+  at 99.9%) where team-average `defense` does NOT (CI spans zero). And the
+  causally-correct atom **MOVES THE NUMBER LESS THAN HALF AS MUCH** (0.013 vs
+  0.030) while being reliably right — the crude version was moving more and
+  knowing less. Bigger movement is not better; it is often the tell.
+- **`src/services/model/sprayDefense.js`** = spray×trajectory × positional OAA,
+  joined by HANDEDNESS. Pull for a RHB is the LEFT side (3B/SS/LF); for a LHB the
+  RIGHT side (1B/2B/RF). Getting that backwards sends half the league's grounders
+  to the wrong infielders and **still looks like it's reading defence** — nothing
+  downstream would catch it. Switch hitters are UNREADABLE (they bat opposite the
+  pitcher, unresolved here), not guessed.
+- **Both halves were already free.** Savant's `leaderboard/batted-ball` carries
+  pull/straight/oppo × ground/air (609 hitters) — the `statcast` leaderboard does
+  NOT (19 cols, no direction). And the OAA feed already carries each fielder's
+  position, so per-position defence is a REGROUPING of last week's ingest.
+  `team_defense.position_oaa` + `batter_spray` (dated). Prod-verified 609/31.
+- **Unmeasured zones are RENORMALISED AWAY, never zero** — a zero asserts an
+  exactly-average fielder standing there. `coverage` states what share of a
+  hitter's contact we could actually read; nothing readable → null.
+- **ATOM 2 (park+weather→hit-type) is INPUT-BLOCKED, not sample-blocked.**
+  Weather's free source check PASSES (Open-Meteo already wired via
+  `weatherService`, exposing temp_f/wind_mph/wind_dir/precip_mm) — but those raw
+  fields are collapsed into a scalar `env_weather_mod` and `wx_forecast` is
+  **0/1119** on settled rows. And **park DIMENSIONS are not ingested at all**
+  (parkFactors holds coefficients, not wall heights or fence distances). A
+  hit-type conversion needs both; retaining the raw weather fields is the cheap
+  half, dimensions are the missing one.
+
 ## Active Skills
 - vyndr-voice (all user-facing output)
 - prop-analysis (grading methodology)
diff --git a/scripts/prove-hit-factors.js b/scripts/prove-hit-factors.js
index 8a159dd..3edf727 100644
--- a/scripts/prove-hit-factors.js
+++ b/scripts/prove-hit-factors.js
@@ -25,6 +25,7 @@ const tl = require('../src/services/model/testLedger');
 const mlb = require('../src/services/adapters/mlbStatsAdapter');
 const { knownNumber, knownRate } = require('../src/utils/known');
 const { nameKey } = require('../src/utils/playerName');
+const sd = require('../src/services/model/sprayDefense');
 
 const SB_URL = process.env.SUPABASE_URL;
 const SB_KEY = process.env.SUPABASE_SERVICE_ROLE_KEY || process.env.SUPABASE_SERVICE_KEY;
@@ -49,6 +50,12 @@ async function page(sb, table, select, apply) {
  * than nudge it toward some default.
  */
 const FACTORS = [
+  {
+    key: 'defense_by_direction',
+    needs: ['spray_multiplier'],
+    mechanism: 'CAUSALLY-CORRECT DEFENCE. Where the hitter puts the ball (pull/straight/oppo x ground/air) crossed with the OAA of the fielders actually standing in those zones, joined by handedness. Team-average failed the gate because it averages in five fielders who will never touch his ball.',
+    apply: (r) => r.spray_multiplier,
+  },
   {
     key: 'defense',
     needs: ['team_defense'],
@@ -88,6 +95,14 @@ async function main() {
     if (r.role === 'pitcher' && r.source_id != null) pitchersById.set(Number(r.source_id), prof);
     if (r.role === 'batter' && r.player_key) batters.set(r.player_key, prof);
   }
+  const sprayRows = await page(sb, 'batter_spray', '*', (q) => q.eq('sport', 'mlb'));
+  const sprayByKey = new Map();
+  for (const r of sprayRows) {
+    if (!r.player_key) continue;
+    const prev = sprayByKey.get(r.player_key);
+    if (!prev || String(r.as_of_date) > String(prev.as_of_date)) sprayByKey.set(r.player_key, r);
+  }
+
   const defRows = await page(sb, 'team_defense', '*', (q) => q.eq('sport', 'mlb'));
   const defByTeam = new Map();
   for (const d of defRows) defByTeam.set(d.team, d);
@@ -155,6 +170,13 @@ async function main() {
       team_defense: def ? knownNumber(def.oaa_sum) : null,
       pitcher_hard_hit_allowed: pit ? knownRate(pit.hard_hit_pct) : null,
       park_factor: knownNumber(r.env_park_base),
+      spray_multiplier: (() => {
+        const sp = sprayByKey.get(r.player_key);
+        const posOaa = def && def.position_oaa ? def.position_oaa : null;
+        if (!sp || !posOaa || !bat || !bat.bats) return null;
+        const out = sd.sprayDefenseMultiplier({ spray: sp, bats: bat.bats, positionOaa: posOaa });
+        return out ? out.multiplier : null;
+      })(),
       platoon_edge: (bat && pit && bat.bats && pit.throws)
         ? (String(bat.bats)[0] !== String(pit.throws)[0] ? 1 : -1) : null,
     });