spec: Feature 4.1 — Model Learning Loop (Phase 4 backlog)

Closed-loop intelligence: settled bets feed back into grading weights.
- Grade accuracy tracking per stat type (A/B/C/D hit rates)
- Signal accuracy tracking (which deltas predict outcomes)
- Kill condition effectiveness (hit_rate_with vs without)
- Conservative weight adjustment (20% cap, 50-pick minimum)
- 4 new DB tables: grade_accuracy, signal_accuracy,
  kill_condition_accuracy, weight_history
- Desk-tier endpoints: /api/model/accuracy, /api/model/insights

Spec complete, ready to build when Phase 3 deployment is stable.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ROADMAP.md

@@ -72,6 +72,19 @@ Depends on: Phase 2 complete
 - Founder code locks rate
 - Status: NOT STARTED
 
+## PHASE 4 — INTELLIGENCE (Backlog)
+
+### Feature 4.1 — Model Learning Loop (depends: 1.3 + 1.5)
+- Settled bets feed back into grading weight analysis
+- Track grade accuracy (A/B/C/D hit rates) per stat type
+- Track signal accuracy (which deltas actually predict outcomes)
+- Track kill condition effectiveness (do they prevent bad bets?)
+- Auto-adjust grading weights with conservative learning rate
+- Weight changes capped at 20% per cycle, min 50 picks per signal
+- GET /api/model/accuracy (Desk tier) — current model stats
+- GET /api/model/insights (Desk tier) — human-readable learnings
+- Status: SPEC COMPLETE — ready to build
+
 ## DEPENDENCY MAP
 ```
 1.1 (Odds API) ──┐

specs/feature-4-1-model-learning-loop.md

@@ -0,0 +1,330 @@
+# Feature 4.1 — Model Learning Loop
+
+## Overview
+Closed-loop intelligence system. Every settled bet feeds back into the grading engine. Track which signals, kill conditions, and composite weights actually predict outcomes. Over time, the model self-calibrates — grades get sharper, kill conditions get validated or deprecated, and weight distribution shifts toward what works.
+
+## Dependencies
+- Feature 1.3 — Prop Analysis Engine (grader.js weights to tune)
+- Feature 1.5 — Bet Submission (settled bets with outcomes)
+- Feature 1.4 — Database Schema (outcomes, picks, performance tables)
+
+## The Loop
+
+```
+User scans parlay → grades assigned with current weights
+  ↓
+User places bet → logs in tracker
+  ↓
+Game plays out → user settles bet (won/lost/push)
+  ↓
+System records: grade predicted X, actual result was Y
+  ↓
+Accumulate enough data (50+ settled picks per signal)
+  ↓
+Recalculate signal accuracy → adjust grading weights
+  ↓
+Next scan uses improved weights
+```
+
+## New Database Tables
+
+### grade_accuracy
+Tracks accuracy of each grade level over time.
+
+```sql
+CREATE TABLE public.grade_accuracy (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  grade TEXT NOT NULL CHECK (grade IN ('A', 'B', 'C', 'D')),
+  stat_type TEXT NOT NULL,
+  total_picks INT NOT NULL DEFAULT 0,
+  hits INT NOT NULL DEFAULT 0,
+  misses INT NOT NULL DEFAULT 0,
+  pushes INT NOT NULL DEFAULT 0,
+  hit_rate NUMERIC(5,2),
+  expected_hit_rate NUMERIC(5,2),
+  calculated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE UNIQUE INDEX idx_grade_accuracy_unique ON public.grade_accuracy(grade, stat_type);
+```
+
+### signal_accuracy
+Tracks how predictive each individual signal is.
+
+```sql
+CREATE TABLE public.signal_accuracy (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  signal_name TEXT NOT NULL,
+  signal_value TEXT NOT NULL,
+  stat_type TEXT NOT NULL,
+  total_picks INT NOT NULL DEFAULT 0,
+  hits INT NOT NULL DEFAULT 0,
+  hit_rate NUMERIC(5,2),
+  avg_edge_when_hit NUMERIC(5,2),
+  avg_edge_when_miss NUMERIC(5,2),
+  predictive_score NUMERIC(5,2),
+  calculated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE UNIQUE INDEX idx_signal_accuracy_unique ON public.signal_accuracy(signal_name, signal_value, stat_type);
+```
+
+### kill_condition_accuracy
+Tracks whether kill conditions actually prevent bad bets.
+
+```sql
+CREATE TABLE public.kill_condition_accuracy (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  kill_condition TEXT NOT NULL,
+  total_triggered INT NOT NULL DEFAULT 0,
+  picks_with_condition INT NOT NULL DEFAULT 0,
+  hits_with_condition INT NOT NULL DEFAULT 0,
+  hit_rate_with NUMERIC(5,2),
+  hit_rate_without NUMERIC(5,2),
+  effectiveness NUMERIC(5,2),
+  calculated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE UNIQUE INDEX idx_kill_accuracy_unique ON public.kill_condition_accuracy(kill_condition);
+```
+
+### weight_history
+Audit trail of weight changes over time.
+
+```sql
+CREATE TABLE public.weight_history (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  weight_set JSONB NOT NULL,
+  reason TEXT NOT NULL,
+  sample_size INT NOT NULL,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+```
+
+## Signal Tracking
+
+On every pick created (via parlay scan), store the individual signal values alongside the pick. This is already partially captured in `picks.reasoning`, but we need structured data for aggregation.
+
+### New column on picks table (migration 003):
+```sql
+ALTER TABLE public.picks ADD COLUMN signal_snapshot JSONB;
+```
+
+`signal_snapshot` stores:
+```json
+{
+  "season_delta": 1.8,
+  "recent_delta": 2.3,
+  "situational_delta": 1.5,
+  "line_edge": 0.5,
+  "home_away_signal": "bullish",
+  "rest_signal": "neutral",
+  "vs_opponent_signal": "strong_bullish",
+  "kill_conditions": ["blowout_risk"],
+  "composite": 2.1,
+  "weights_version": 1
+}
+```
+
+## Accuracy Calculation Pipeline
+
+Triggered periodically (on every 10th bet settlement, or daily cron).
+
+### Step 1: Grade Accuracy
+```
+For each grade (A, B, C, D) × stat_type:
+  - Count settled picks with that grade + stat
+  - Count hits (outcome = 'hit')
+  - Calculate hit_rate = hits / total * 100
+  - Compare to expected:
+    - A should hit ~70-80%
+    - B should hit ~55-65%
+    - C should hit ~45-55%
+    - D should hit ~30-40%
+  - If actual diverges from expected by >10%: flag for weight adjustment
+```
+
+### Step 2: Signal Accuracy
+```
+For each signal (season_delta, recent_delta, etc.):
+  - Group picks by signal_value bucket:
+    - "strong_bullish" (delta >= 4)
+    - "bullish" (2-4)
+    - "lean" (0.5-2)
+    - "neutral" (< 0.5)
+    - bearish equivalents
+  - For each bucket:
+    - hit_rate = hits / total
+    - avg_edge_when_hit vs avg_edge_when_miss
+    - predictive_score = (hit_rate - 0.5) * log(total)
+      (rewards accuracy AND sample size)
+```
+
+### Step 3: Kill Condition Effectiveness
+```
+For each kill condition:
+  - Picks where this condition triggered: hit_rate_with
+  - Picks where this condition did NOT trigger: hit_rate_without
+  - effectiveness = hit_rate_without - hit_rate_with
+    (positive = the kill condition correctly identifies bad bets)
+  - If effectiveness < 5%: kill condition may not be useful
+  - If effectiveness > 20%: kill condition is highly predictive
+```
+
+### Step 4: Weight Adjustment
+```
+Current weights: season=1.0, recent=1.5, situational=1.2, lineEdge=0.8
+
+If a signal's predictive_score is higher than its current weight influence:
+  → Increase that weight
+If a signal's predictive_score is lower:
+  → Decrease that weight
+
+Adjustment formula:
+  new_weight = current_weight * (1 + (predictive_score - baseline) * learning_rate)
+  learning_rate = 0.1 (conservative — small steps)
+
+Constraints:
+  - No weight can drop below 0.3 or exceed 3.0
+  - Total weight sum stays within 3.5-5.5 range
+  - Changes capped at 20% per adjustment cycle
+  - Minimum 50 picks per signal before adjusting
+
+Store new weights in weight_history.
+Apply new weights to grader.js (load from DB on startup, fallback to defaults).
+```
+
+## Endpoints
+
+### GET /api/model/accuracy (auth required, Desk tier only)
+Returns current model accuracy stats.
+
+**Response (200):**
+```json
+{
+  "grade_accuracy": [
+    { "grade": "A", "stat_type": "points", "total": 120, "hit_rate": 72.5, "expected": 75.0 },
+    { "grade": "B", "stat_type": "points", "total": 200, "hit_rate": 58.0, "expected": 60.0 }
+  ],
+  "signal_accuracy": [
+    { "signal": "recent_delta", "value": "bullish", "stat_type": "points", "hit_rate": 68.0, "predictive_score": 4.2 }
+  ],
+  "kill_condition_effectiveness": [
+    { "condition": "blowout_risk", "effectiveness": 22.5, "triggered": 45 },
+    { "condition": "low_minutes", "effectiveness": 18.0, "triggered": 30 }
+  ],
+  "current_weights": {
+    "season": 1.0, "recent": 1.5, "situational": 1.2, "lineEdge": 0.8,
+    "version": 3, "last_updated": "2026-04-15T00:00:00Z"
+  },
+  "total_settled_picks": 850,
+  "model_confidence": "high"
+}
+```
+
+### GET /api/model/insights (auth required, Desk tier only)
+Returns human-readable insights from the learning loop.
+
+**Response (200):**
+```json
+{
+  "insights": [
+    {
+      "type": "signal_outperforming",
+      "message": "Recent form (last 10 games) is the strongest predictor for points props. It outperforms season average by 12%.",
+      "action": "Recent form weight increased from 1.5 to 1.65."
+    },
+    {
+      "type": "kill_condition_validated",
+      "message": "blowout_risk is your most effective kill condition. Props in blowout games hit 15% less often.",
+      "action": "No change needed — working as designed."
+    },
+    {
+      "type": "grade_calibration",
+      "message": "Grade A picks on rebounds are hitting at 68% instead of expected 75%. Sample is small (40 picks) — monitoring.",
+      "action": "No weight change yet. Need 50+ picks to adjust."
+    }
+  ],
+  "next_recalculation_at": "2026-04-20T00:00:00Z"
+}
+```
+
+## Service Architecture
+
+```
+src/
+├── services/
+│   ├── modelLearningService.js    # Orchestrator: triggers accuracy calc + weight adjustment
+│   ├── accuracyCalculator.js      # Grade, signal, kill condition accuracy from settled data
+│   └── weightAdjuster.js          # Computes new weights, stores history, applies to grader
+├── routes/
+│   └── model.js                   # GET /api/model/accuracy, GET /api/model/insights
+```
+
+## Integration Points
+
+### On bet settlement (betService.js):
+```
+After settling a bet:
+  1. Check total settled picks for this user
+  2. Every 10th settlement: trigger modelLearningService.recalculate()
+  3. This is global (not per-user) — all users' data feeds the model
+```
+
+### On pick creation (parlayScanService.js):
+```
+When creating a pick:
+  1. Attach signal_snapshot JSONB with all signal values + current weights version
+  2. This enables retrospective analysis of which weights were active when the pick was made
+```
+
+### On grader startup (grader.js):
+```
+On first call:
+  1. Load latest weight_set from weight_history table
+  2. If no weights in DB: use hardcoded defaults
+  3. Cache weights in memory, refresh every hour
+```
+
+## Acceptance Criteria
+
+1. Every settled pick updates grade_accuracy, signal_accuracy, and kill_condition_accuracy tables
+2. Grade accuracy tracks hit rate per grade per stat type
+3. Signal accuracy tracks predictive score per signal per stat type
+4. Kill condition effectiveness measures hit_rate_with vs hit_rate_without
+5. Weight adjustment runs after every 10th settlement (global)
+6. Weight changes are capped at 20% per cycle, bounded 0.3-3.0
+7. Weight history is stored with reason and sample size
+8. `GET /api/model/accuracy` returns current stats (Desk tier only)
+9. `GET /api/model/insights` returns human-readable insights
+10. signal_snapshot JSONB attached to every new pick
+11. Grader loads weights from DB on startup, falls back to defaults
+12. Minimum 50 picks per signal before weight adjustment triggers
+
+## Test Plan
+
+### Unit Tests (accuracyCalculator.js)
+- Correctly computes hit rate from settled picks
+- Groups by grade + stat_type
+- Groups by signal + value + stat_type
+- Kill condition effectiveness: difference between with/without
+- Handles zero settled picks gracefully
+
+### Unit Tests (weightAdjuster.js)
+- Increases weight when predictive_score exceeds baseline
+- Decreases weight when predictive_score below baseline
+- Caps changes at 20% per cycle
+- Enforces min/max bounds (0.3-3.0)
+- Stores weight history with correct reason
+- Does not adjust with < 50 picks per signal
+
+### Integration Tests
+- Full loop: create pick with signal_snapshot → settle → accuracy updated → weights adjusted
+- GET /api/model/accuracy returns correct stats
+- GET /api/model/insights generates relevant insights
+- Desk tier only: free/analyst get 403
+- Weight changes reflected in next grading call
+
+## Open Questions
+- **Global vs per-user model:** This spec uses a global model (all users' data combined). Per-user models would require significantly more data. Global is correct for MVP — the model learns from collective intelligence. Per-user customization can layer on top later.
+- **Cold start:** With < 50 settled picks, no adjustments fire. The hardcoded defaults carry the system until enough data accumulates. This is intentional — bad adjustments on small samples would be worse than no adjustments.