01. Core Architecture & Philosophy
Large trading desks and market participants rarely accumulate significant derivatives positions using routine limit orders. Doing so alerts competing algorithms and creates substantial adverse price slippage.
Instead, aggressive market participants deploy aggressive multi-strike sweeps and large block orders. The Arkenwell Unusual Activity Detector continuously monitors the entire National Stock Exchange (NSE) options chain to isolate anomalous order flow in real time.
Unlike generic scanners that only filter for raw volume spikes, the Arkenwell engine utilizes a multi-pillar statistical framework combining Modified Z-Scores (Iglewicz-Hoaglin), 252-Day Implied Volatility Rank (IVR), Rupee Premium Turnover (₹ Cr), and Dealer Gamma (GEX) / Delta (DEX) Exposure Shifts.
02. Robust Statistical Primitives (Modified Z-Score & MAD)
Standard z-scores fail in derivatives analysis because single-day expiry surges distort rolling sample means and standard deviations.
To eliminate false positives caused by routine rollover surges, the detector employs the Iglewicz-Hoaglin Modified Z-Score calculated against a rolling 20-day baseline:
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Median Absolute Deviation (MAD): Evaluates the median dispersion of daily volume across the past 20 trading sessions. If MAD is zero, the engine safely falls back to a neutral score.
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Statistical Multiplier (0.6745): Scales the deviation to align with standard normal distributions for robust outlier detection.
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Expiry Significance Scaling: Adjusts volume sensitivity based on Days to Expiry (DTE). A 5,000-contract sweep on a 25-DTE monthly contract receives a higher statistical weight than the same volume on 0DTE expiry afternoon.
03. Composite Scoring Engine (0 to 100 Scale)
Every screened strike is evaluated through a composite quantitative scoring model calibrated specifically for Indian equity derivatives:
1. Volume Z-Score (35% Weight): Normalized against a saturating z-score cap of 6.0 standard deviations.
2. Open Interest Change % (25% Weight): Measures the percentage shift in open interest relative to the previous session baseline (capped at 50% shift).
3. Rupee Premium Traded (20% Weight): Scaled against a ₹5.00 Crore turnover benchmark to filter out low-value retail trades.
4. 252-Day IV Rank (20% Weight): Tracks where current implied volatility sits relative to the 52-week low and high (0.0 to 1.0), isolating true volatility expansion.
5. Moneyness Weighting & GEX Shift Bonus: Multipliers scale At-the-Money (ATM) and Near-the-Money strikes over far-OTM strikes. If the strike's open interest change forces a dealer GEX shift exceeding 1.5 standard deviations, an additional +8.0 bonus is added to the composite score.
04. Severity Classification Tiers
Screened options signals are categorized into four standardized severity tiers:
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EXTREME (Score ≥ 80): Massive multi-crore turnover with volume z-scores > 4.5σ and substantial open interest buildup. Highest urgency; signals immediate dealer delta-hedging pressure.
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UNUSUAL (Score ≥ 60): Significant volume and open interest expansion exceeding 2.5σ above normal baseline. Strong directional accumulation.
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ELEVATED (Score ≥ 30): Moderate statistical deviation; early position accumulation or spread building.
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NORMAL (Score < 30): Routine baseline market turnover; filtered out of real-time alert broadcasts.
05. 4-State Derivatives Buildup Classification
The engine monitors price tick changes and Open Interest (OI) changes to classify every unusual print into one of four structural market regimes:
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LONG BUILDUP (Price ↑ + OI ↑): Aggressive buyers accumulating long option contracts with rising premium. Bullish directional intent for Calls; downside hedging demand for Puts.
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SHORT BUILDUP (Price ↓ + OI ↑): Option sellers aggressively writing contracts and absorbing incoming flow. Strong overhead resistance for Calls; support floor for Puts.
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SHORT COVERING (Price ↑ + OI ↓): Previous option sellers closing and covering short positions, fueling rapid upward momentum as buyback market orders trigger.
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LONG UNWINDING (Price ↓ + OI ↓): Long contract holders taking profits or cutting losses, leading to liquidity drain and premium erosion.
06. Directional Conviction & Flow Attribution
To assist desks in interpreting whether a large sweep is directional or part of an institutional multi-leg hedge, the detector calculates Directional Flow Conviction (-100 to +100):
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Positive Conviction (+100.0): Net bullish capital commitment (Call Long Buildup or Put Short Buildup) aligned with Kalman spot momentum and positive GEX delta.
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Negative Conviction (-100.0): Net bearish capital commitment (Put Long Buildup or Call Short Buildup) indicating downside positioning or overhead supply.
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Neutral / Hedging Spread (0.0): Balanced dual-strike activity representing delta-neutral straddles, strangles, or collar structures.
07. Real Market Case Study: NIFTY ATM Straddle Dislocation
During a live session, NIFTY spot trades near 24,020 with India VIX stable at 14.1%.
At 10:14 IST, the Unusual Activity Detector flags two simultaneous EXTREME alerts:
1. 24,000 PE: Score 96.7 | Severity EXTREME | Buildup: SHORT BUILDUP | Vol Z: +5.78σ | OI Change: +246.6% | Premium: ₹35.55 Cr | IV Rank: 50.0%
2. 24,000 CE: Score 92.6 | Severity EXTREME | Buildup: SHORT BUILDUP | Vol Z: +5.07σ | OI Change: +172.1% | Premium: ₹34.68 Cr | IV Rank: 50.0%
Interpretation: Market makers and large option sellers aggressively wrote both the 24,000 Call and Put, deploying over ₹70 Crores in combined premium. This created an immediate Gamma Pinning Zone at 24,000, causing NIFTY to consolidate within a tight 30-point corridor for the remainder of the session.
08. Quantitative Noise Rejection & Filtering Rules
To avoid false alarms on illiquid contracts, the engine applies three strict gatekeeping rules:
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Minimum Liquidity Volume Gate: Strikes with contract volume below 500 lots are automatically dropped from scoring.
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Bid-Ask Spread Filter: Eliminates deep out-of-the-money options where wide spreads artificially inflate traded premium metrics.
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Lot Size Normalization: Scales traded units by official NSE contract lot sizes (e.g., 25 for NIFTY, 15 for BANKNIFTY, stock-specific lot sizes for single-stock F&O).
09. Common Trader Mistakes vs. Reality
* Common Belief: A large spike in Put volume always indicates impending market collapse.
* Reality: High Put volume with rising Open Interest (Short Buildup) indicates aggressive option writing, forming strong support rather than a breakdown.
* Common Belief: Volume alone is sufficient to identify unusual activity.
* Reality: High volume without significant Open Interest change simply reflects intraday day-trading churning rather than structural overnight capital commitment.
* Common Belief: Every alert should be traded immediately as a directional breakout.
* Reality: Unusual activity must always be verified against the strike's Dealer Gamma Flip line and underlying liquidity regime.
10. Terminal Workflow & Command Usage
To navigate and operate the Unusual Activity Detector in Arkenwell:
1. Open OPTIONS ORDER FLOW → Unusual Activity Detector from the main navigation or type
SWEEPS in the Command Palette.2. Use the Filter Drawer to set minimum Score thresholds (e.g., Score ≥ 70) and isolate specific Buildup types.
3. Double-click any signal row to open the detailed Strike Inspector displaying live Greeks, IV skew, and historical volume distributions.
4. Enable Audio Telemetry Alerts to receive instant sound cues when EXTREME tier alerts trigger.
11. Professional Summary & Key Takeaways
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Modified Z-Scores with 20-day MAD eliminate rollover noise and highlight genuine volume dislocations.
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4-State Buildup classification reveals whether capital is actively buying premium or writing contracts.
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Combining Rupee Premium, IV Rank, and GEX shift ensures alerts reflect genuine market impact.
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Real-time flow filtering identifies high-conviction opportunities before price breaks out.
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