Session 50: Complete Parlay Lab (2215 tests)

Correlation-aware combined parlay grading — the Desk-tier differentiator.

- Correlation model (parlayService.js, added to S28 funcs): correlationScore
  (game-aware 0.7/0.4/0.2/0.0), combinedGrade (avg penalized by avgCorr*0.5),
  estimatedPayout (fair-odds product * (1-avgCorr) discount), correlationWarning,
  gradeParlay.
- POST /api/parlay/grade (public, 2-6 legs) -> {combined,correlation,payout,legs}.
  Fixed the Next proxy (was forwarding to /api/scan/parlay).
- ParlayContext: legs gained team/game/archetype; tier-aware maxLegs; auto-grades
  the slip (debounced) when legs>=2 -> live combined/correlation/payout; hasLeg/
  legKey/atCap.
- "+" button on every graded prop: StatStrip onAddLeg/isLegActive, wired by
  vyndr/GameCard via useParlay (builds leg w/ team + game). GradeResultCard feeds
  the same context from the scan page.
- ParlayPanel (replaces legacy ParlayTray): bottom slide-up w/ legs, combined
  grade, correlation warning, est payout, CLEAR ALL + floating leg-count badge.
  Tier-gated: free 2 legs (payout blurred -> Desk upsell), Analyst 4, Desk 6.

Backend 2185 -> 2215 tests (+30), 187 suites. Web build clean (exit 0).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/unit/parlayCorrelation.test.js

@@ -0,0 +1,85 @@
+// Session 50 — Parlay Lab correlation-score model.
+
+const svc = require('../../src/services/parlayService');
+
+const leg = (over) => ({ player: 'P', team: 'NYY', game: 'NYY@BOS', stat: 'hits', grade: 'A', ...over });
+
+describe('correlationScore', () => {
+  it('same player, same game → 0.7', () => {
+    expect(svc.correlationScore(leg({ stat: 'hits' }), leg({ stat: 'total_bases' }))).toBe(0.7);
+  });
+  it('same team, same game, different players → 0.4', () => {
+    expect(svc.correlationScore(leg({ player: 'A' }), leg({ player: 'B' }))).toBe(0.4);
+  });
+  it('same game, different teams → 0.2', () => {
+    expect(svc.correlationScore(leg({ player: 'A', team: 'NYY' }), leg({ player: 'B', team: 'BOS' }))).toBe(0.2);
+  });
+  it('different games → 0.0', () => {
+    expect(svc.correlationScore(leg({ game: 'NYY@BOS' }), leg({ game: 'LAD@SF', player: 'B', team: 'LAD' }))).toBe(0);
+  });
+});
+
+describe('combinedGrade', () => {
+  it('3 independent A legs → A (no penalty)', () => {
+    const r = svc.combinedGrade([
+      { grade: 'A', game: 'g1', team: 't1', player: 'a' },
+      { grade: 'A', game: 'g2', team: 't2', player: 'b' },
+      { grade: 'A', game: 'g3', team: 't3', player: 'c' },
+    ]);
+    expect(r.grade).toBe('A');
+    expect(r.penalty).toBe(0);
+  });
+  it('3 same-team same-game A legs → penalized below A', () => {
+    const r = svc.combinedGrade([
+      { grade: 'A', game: 'g1', team: 'NYY', player: 'a' },
+      { grade: 'A', game: 'g1', team: 'NYY', player: 'b' },
+      { grade: 'A', game: 'g1', team: 'NYY', player: 'c' },
+    ]);
+    expect(r.avgCorrelation).toBe(0.4);
+    expect(r.penalty).toBeGreaterThan(0);
+    expect(['B+', 'B', 'B-', 'A-']).toContain(r.grade);
+    expect(svc.gradeScore(r.grade)).toBeLessThan(svc.gradeScore('A'));
+  });
+});
+
+describe('estimatedPayout', () => {
+  it('returns multiplier + discount for a 3-leg parlay', () => {
+    const r = svc.estimatedPayout([{ grade: 'A' }, { grade: 'B+' }, { grade: 'A' }], 10);
+    expect(r.fairMultiplier).toBeCloseTo(1.25 * 1.45 * 1.25, 2);
+    expect(r.correlationDiscount).toBe(1); // independent
+    expect(r.payout).toBeGreaterThan(10);
+  });
+  it('discounts correlated slips', () => {
+    const corr = svc.estimatedPayout([{ grade: 'A', game: 'g', team: 'NYY', player: 'a' }, { grade: 'A', game: 'g', team: 'NYY', player: 'b' }], 10);
+    expect(corr.correlationDiscount).toBeLessThan(1);
+  });
+});
+
+describe('correlationWarning', () => {
+  it('flags 2+ legs from the same team', () => {
+    const w = svc.correlationWarning([
+      { game: 'g', team: 'PHI', player: 'a' }, { game: 'g', team: 'PHI', player: 'b' }, { game: 'g2', team: 'NYY', player: 'c' },
+    ]);
+    expect(w).toBe('⚠ 2 legs from PHI — high correlation');
+  });
+  it('flags same-game legs on different teams', () => {
+    expect(svc.correlationWarning([{ game: 'g', team: 'A', player: 'x' }, { game: 'g', team: 'B', player: 'y' }]))
+      .toBe('⚠ 2 legs from the same game — correlated');
+  });
+  it('null when all legs are independent', () => {
+    expect(svc.correlationWarning([{ game: 'g1', team: 'A', player: 'x' }, { game: 'g2', team: 'B', player: 'y' }])).toBeNull();
+  });
+});
+
+describe('gradeParlay (full analysis)', () => {
+  it('returns combined + correlation + payout + legs', () => {
+    const r = svc.gradeParlay([
+      { grade: 'A', game: 'g', team: 'NYY', player: 'a', stat: 'hits', line: 1.5 },
+      { grade: 'B+', game: 'g', team: 'NYY', player: 'b', stat: 'tb', line: 1.5 },
+    ], 10);
+    expect(r.combined.grade).toBeTruthy();
+    expect(r.correlation.warning).toContain('NYY');
+    expect(r.payout.amount).toBeGreaterThan(0);
+    expect(r.legs).toHaveLength(2);
+  });
+});