---

name: measurement-infrastructure description: Build prediction logging, outcome tracking, and data pipelines for model calibration. Read FIRST before any model, calibration, or signal work. Covers PredictionRecord schema, async outcome matcher, JSONL persistence, and market state snapshots. user-invocable: false

Measurement Infrastructure Skill

Purpose

Build the prediction logging and outcome tracking system that all other model improvements depend on. This is the foundation - without proper measurement, you can't know if anything else is working.

READ THIS SKILL FIRST before any model work.

When to Use

• Setting up a new trading system from scratch
• Adding prediction logging to an existing quote engine
• Building the data pipeline for calibration analysis
• Any time you're about to build a predictive model

Core Principle

Every quote cycle, your system makes implicit predictions:

• "If I place a bid at this price, the probability of fill in 1s is X%"
• "If I get filled, the probability of adverse selection is Y%"
• "The price will move Z bps in the next 10 seconds"

These predictions must be recorded with enough granularity to diagnose failures.

---

Schema Definitions

1. Prediction Record (Top Level)

struct PredictionRecord {
    timestamp_ns: u64,
    quote_cycle_id: u64,
    market_state: MarketStateSnapshot,
    predictions: ModelPredictions,
    outcomes: Option<ObservedOutcomes>,
}

2. Market State Snapshot

Capture everything the model could condition on:

struct MarketStateSnapshot {
    // L2 Book State
    bid_levels: Vec<(f64, f64)>,  // (price, size) top N
    ask_levels: Vec<(f64, f64)>,
    spread_bps: f64,
    microprice: f64,
    book_imbalance: f64,  // (bid_size - ask_size) / total

    // Kappa
    kappa_book: f64,
    kappa_robust: f64,
    kappa_own: f64,
    kappa_final: f64,

    // Volatility
    sigma_bipower: f64,
    sigma_realized_1m: f64,
    sigma_realized_5m: f64,

    // Gamma
    gamma_base: f64,
    gamma_effective: f64,

    // Hyperliquid-specific
    funding_rate: f64,
    time_to_funding_settlement_s: f64,
    open_interest: f64,
    open_interest_delta_1m: f64,

    // Cross-exchange
    binance_mid: Option<f64>,
    binance_hl_basis_bps: Option<f64>,

    // Position
    inventory: f64,
    inventory_age_s: f64,

    // Regime
    regime_quiet_prob: f64,
    regime_trending_prob: f64,
    regime_volatile_prob: f64,
    regime_cascade_prob: f64,
}

3. Model Predictions

struct ModelPredictions {
    levels: Vec<LevelPrediction>,
    expected_fill_rate_1s: f64,
    expected_adverse_selection_bps: f64,
    predicted_price_direction_1s: f64,  // [-1, 1]
    direction_confidence: f64,
}

struct LevelPrediction {
    side: Side,
    price: f64,
    size: f64,
    depth_from_mid_bps: f64,
    p_fill_1s: f64,
    p_fill_10s: f64,
    p_adverse_given_fill: f64,
    expected_pnl_given_fill: f64,
}

4. Observed Outcomes

struct ObservedOutcomes {
    fills: Vec<FillOutcome>,
    price_1s_later: f64,
    price_10s_later: f64,
    price_60s_later: f64,
    realized_adverse_selection_bps: f64,
}

struct FillOutcome {
    level_index: usize,
    fill_timestamp_ns: u64,
    fill_price: f64,
    fill_size: f64,
    mark_price_at_fill: f64,
    mark_price_1s_later: f64,
    mark_price_10s_later: f64,
}

---

Implementation Checklist

Step 1: Instrument Quote Generation

Capture market state BEFORE computing quotes, extract predictions, log as JSONL (one record per line). Outcomes are filled asynchronously via the outcome matcher.

Step 2: Build Async Outcome Matcher

Track pending predictions in a HashMap by cycle_id. On fill events, match to the originating prediction. On price updates, fill in price evolution fields. Flush completed records (age > max_horizon_s) to JSONL.

Step 3: Storage Layer

Use JSONL (one JSON record per line) for persistence. This is what the actual codebase uses — see src/market_maker/analytics/persistence.rs. Files are written to logs/ with rotation by date. The let _ = pattern ensures logging never crashes the trader.

---

What to Log vs What to Skip

Must Log (Critical)

• All fill probability predictions
• All fill outcomes
• Post-fill price evolution (for adverse selection)
• Market state at prediction time
• Regime probabilities

Should Log (Important)

• Kappa inputs and outputs
• Gamma inputs and outputs
• Queue position estimates
• Cross-exchange state

Can Skip (Space Optimization)

• Full L2 book beyond top 5 levels
• Sub-100ms price updates
• Predictions for orders that were never placed

---

Dependencies

• Requires: Your existing quote engine, market data feed
• Enables: calibration-analysis, signal-audit, all model skills

Common Mistakes

1. Logging only aggregates: You need per-prediction granularity to diagnose issues
2. Missing market state: Without conditioning variables, you can't do conditional calibration
3. Synchronous outcome filling: This blocks the hot path; must be async
4. Not logging "boring" periods: Quiet market data is just as important for calibration
5. Forgetting to log predictions for orders that didn't fill: These are negative examples

---

Next Steps

Once this infrastructure is in place:

1. Read calibration-analysis/SKILL.md to analyze the logged data
2. Read signal-audit/SKILL.md to measure signal information content
3. Then proceed to specific model skills