Build opportunity_drift axis on challengerProjection (arch-v1)

Champion p_win and the live grade path are BYTE-IDENTICAL: the axis writes
only to p_win_challenger / challenger_adjustments in the ledger.

STEP 1 -- MAP THE INPUT. MLB_LOG_FIELD now maps at_bats -> 'atBats'.
Deliberately NOT added to outcomeService's map or liveTracking's
LIVE_BOX_FIELD: those exist to SETTLE and TRACK graded props, and nothing
grades at-bats, so adding it there would imply a settlement path for a
market we do not carry. A test asserts the settle map still lacks it.

STEP 2 -- DRIFT, NOT LEVEL. opportunity_drift = mean(last-5 atBats) /
(season atBats / games). The LEVEL is collinear with l20_avg (same
games denominator; hits/game ~= (hits/AB) x (AB/game)), so the projection
already embeds it multiplicatively and adding it would double-count. A
deviation from the player's own baseline is the part the projection does
not contain.

HONEST ABSENCE throughout: fewer than 3 at-bat rows, no at-bats in the
logs, or no season baseline all leave drift UNDEFINED -- never 1.0 by
default and never 0. Number(null) === 0 here would read as "zero at-bats",
the strongest possible fade, invented from missing data. Four tests cover
the absent paths.

STEP 3 -- THE AXIS. opportunityNudge composes in the same log-odds space
as park and platoon (log of a ratio), with two guards the measured axes do
not need: a +/-10% DEADBAND (a rest day or a blowout can move a 5-game
window without any role change) and a tighter cap (0.15 vs the
environment's 0.30) so a noisy PROXY cannot outvote measured signals.
Every adjustment carries is_proxy: true and
proxy_for: 'confirmed_batting_order' so nothing downstream can mistake it
for a lineup feed.

The axis can stand ALONE -- without it the early return would gate
opportunity off on exactly the thin-classification rows it is most likely
to help.

Zero extra I/O: analyzeViaEngine1 attaches drift from the feature vector
it has already built, and attachChallenger reads it off the grade. Nothing
re-fetches in a loop that runs over hundreds of props.

COLLINEARITY GUARD added to the coverage probe: Pearson r of drift against
l20_avg / l5_avg / ab_per_game, returning null under n=8 rather than
reporting a correlation on a handful of rows. If drift just re-encodes the
projection, the axis is dead signal and gets shelved.

Gates: 4,073 tests / 326 suites green; next build exit 0.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QJs13VsyiSKYQP6rj3NNmc

src/services/intelligence/analyzeViaEngine1.js

@@ -384,6 +384,18 @@ function buildIntelFields(features = {}, opts = {}) {
   if (matchup) out.matchup_grade = matchup;
 
   if (Number.isFinite(features.rest_days)) out.rest = features.rest_days === 0 ? 'B2B' : `${features.rest_days}d rest`;
+
+  // OPPORTUNITY DRIFT (2026-08-01) — carried onto the grade so the challenger
+  // can read it WITHOUT a second fetch. The feature is already computed here;
+  // re-resolving it downstream would add per-prop I/O to a path that grades
+  // hundreds of props in a tight loop.
+  //
+  // Raw numbers only — no display string. This is a model input, not a card
+  // field, and rendering an unvalidated proxy as if it were a finding is the
+  // thing we keep removing.
+  if (Number.isFinite(features.opportunity_drift)) out.opportunity_drift = Math.round(features.opportunity_drift * 1000) / 1000;
+  if (Number.isFinite(features.recent_ab_per_game)) out.recent_ab_per_game = round1(features.recent_ab_per_game);
+  if (Number.isFinite(features.ab_per_game)) out.ab_per_game = round1(features.ab_per_game);
   return out;
 }
 

src/services/intelligence/featureCache.js

@@ -84,6 +84,16 @@ const MLB_LOG_FIELD = {
   innings_pitched: 'inningsPitched',
   // Session 56 audit — real boxscore/game-log fields (Braves@Pirates verified).
   doubles: 'doubles', triples: 'triples', outs: 'outs',
+  // OPPORTUNITY INPUT (2026-08-01) — at-bats is NOT a gradeable stat_type and no
+  // market exists for it. It is mapped here only so `mlbStatValue` can read
+  // per-game at-bats out of a log row for the opportunity-drift axis.
+  //
+  // DELIBERATELY NOT ADDED to the other two MLB maps (outcomeService's
+  // MLB_LOG_FIELD, liveTrackingService's LIVE_BOX_FIELD). Those exist to SETTLE
+  // and to TRACK graded props; nothing grades at-bats, so adding it there would
+  // imply a settlement path for a market we do not carry. The three-map split
+  // is intentional — see CLAUDE.md.
+  at_bats: 'atBats',
 };
 
 function mlbStatValue(statObj, statType) {
@@ -153,6 +163,42 @@ function mlbGameLogFeatures(res, statType) {
   if (Number.isFinite(ab) && Number.isFinite(games) && games > 0) {
     out.ab_per_game = ab / games;
   }
+
+  // OPPORTUNITY DRIFT (2026-08-01) — recent at-bats per game against the
+  // player's OWN season baseline.
+  //
+  //   opportunity_drift = mean(last 5 games' atBats) / (season atBats / games)
+  //
+  // WHY A RATIO AND NOT THE LEVEL: `l20_avg` is seasonTotal/games — the SAME
+  // denominator as `ab_per_game` — so for a batter
+  // hits/game ~= (hits/AB) x (AB/game), and the projection ALREADY embeds the
+  // opportunity LEVEL multiplicatively. Adding that level as another input
+  // double-counts it. A deviation from the player's own baseline is the part
+  // the projection does not already contain.
+  //
+  //   > 1  batting higher / playing more than his baseline
+  //   < 1  reduced role, platoon, lower slot
+  //
+  // HONEST ABSENCE: no at-bat rows, or no season baseline, leaves this
+  // UNDEFINED. It is never 1.0-by-default and never 0 — `Number(null) === 0`
+  // here would read as "no opportunity at all", the strongest possible signal,
+  // from missing data.
+  //
+  // THIS IS A PROXY. The real driver of plate appearances is tonight's
+  // confirmed batting order, which no wired source exposes (depthChartService
+  // returns battingOrder: null for MLB; PropLine /context carries only a
+  // lineup_confirmed boolean). Replace this with the real slot when a lineup
+  // feed exists — do not present it as one.
+  const abRows = logs.map((g) => mlbStatValue(g.stat, 'at_bats')).filter((v) => v != null);
+  if (abRows.length >= 3) {
+    const recentAb = avg(abRows.slice(-5));
+    if (recentAb != null) {
+      out.recent_ab_per_game = recentAb;
+      if (Number.isFinite(out.ab_per_game) && out.ab_per_game > 0) {
+        out.opportunity_drift = recentAb / out.ab_per_game;
+      }
+    }
+  }
   return out;
 }
 
@@ -521,6 +567,9 @@ module.exports = {
     statFromGameLog,
     mlbGameLogFeatures,
     mlbStatValue,
+    // Exported so the opportunity-input test can assert at_bats is mapped HERE
+    // and deliberately NOT in the settlement map (the three-map split).
+    MLB_LOG_FIELD,
     nbaGameLogFeatures,
     NBA_LOG_FIELD,
     avg,