NIFTY Expansion Runner — Complete Forensic Bug Audit, Configurable Architecture & Holiday Manifesto

🎯 Architectural Philosophy: Why Autonomous Algorithmic Systems Fail in Production

Algorithmic option execution engines rarely fail due to obvious syntax mistakes; they fail at the temporal, calendar, and regulatory boundaries. When an algorithm transitions from synthetic backtests to live exchange feeds, three critical vulnerability vectors emerge:

1. Temporal Asymmetry

Brokers stream ticks with variable timestamp formats (some UTC aware, some IST naive, some Unix epochs). A single unhandled subtraction between a naive and an aware timestamp throws a fatal TypeError that crashes the process mid-trade.

2. Regulatory Desynchronization

Hardcoding legacy assumptions (e.g. Thursday expiry or 50 lot size) causes catastrophic option mispricing, wrong strike resolution, zero gamma participation, and broker order rejections when regulatory rules change.

3. Exchange Holiday Shifts

If an expiry falls on an exchange holiday (e.g. Dussehra or Diwali on Tuesday), contracts expire on Monday. Algorithms that do not prepone will look for non-existent contracts on Tuesday and fail to exit 0-DTE gamma positions.

📋 Complete Forensic Bug Audit & Resolution Matrix

Subsystem	Vulnerability / Bug	Root Cause	Forensic Impact	Engineering Remedy	Status
Data Feed Watchdog	Timestamp subtraction crash	feed_watchdog.py	TypeError: can't subtract offset-naive and offset-aware datetimes. Feed watchdog crashes on live tick.	Normalize all feed timestamps using UTC-aware conversion before delta computation.	FIXED
Symbol Resolver	Weekly Expiry Day & Rollover	symbol_resolver.py	Legacy Thursday assumptions caused 2-day stale option selection and missed 0-DTE gamma squeeze opportunities.	Rebuilt to use ExchangeCalendar with Tuesday weekly default (1), holiday preponement, and env overrides.	FIXED
Risk & Sizing Engine	Lot Size Hardcoding	position_sizer.py	Hardcoding 50 caused order rejections at the broker exchange boundary for NIFTY lot size (65).	Enforced default lot size of 65 shares with dynamic configuration via config/risk.yaml and LOT_SIZE env var.	FIXED
Trade Management	Scaling Profile Resolution	trade_manager.py	0-DTE Expiry Gamma profile failed to activate on Tuesday afternoons; treated Tuesday as normal 5-DTE day.	Integrated ExchangeCalendar.is_expiry_day() to trigger EXPIRY_GAMMA scaling on effective expiry days.	FIXED
Calendar Engine	Holiday on Expiry Day	calendar.py	If Tuesday is an exchange holiday, contracts expire on Monday. System had no holiday preponement logic.	Created ExchangeCalendar with 2025-2027 NSE holidays, preponing expiry to the previous active trading day.	FIXED
Trade Copier Gateway	Child Multiplier Sizing	replicator.py	Replicator used hardcoded lot size in child fan-out calculations causing fractional shares.	Integrated configurable lot_size fallback to LOT_SIZE env var and rounded strictly to nearest lot.	FIXED

📅 Tuesday Weekly Expiry Lifecycle & DTE Matrix

NSE NIFTY weekly index option contracts mature on Tuesday. The system's symbol resolver, strike window span calculator, and gamma strategies default strictly to Tuesday, while fully supporting dynamic configuration.

Weekday	Python Index	DTE (Days to Tuesday)	Strike Window Span	Session Profile
Tuesday	1	0 DTE (Expiry Day)	±1 Strike (ATM ±50 pts)	EXPIRY_GAMMA (Active post-13:00)
Wednesday	2	5 DTE (New Weekly Cycle)	±5 Strikes (±250 pts)	STANDARD_BALANCED
Thursday	3	4 DTE	±4 Strikes (±200 pts)	TREND_RUNNER / QUICK_HARVEST
Friday	4	3 DTE	±3 Strikes (±150 pts)	STANDARD_BALANCED
Monday	0	1 DTE (Pre-Expiry)	±2 Strikes (±100 pts)	QUICK_HARVEST / MOMENTUM

📦 NIFTY Contract Sizing (65 Shares / Lot)

The official lot size for NIFTY 50 options is 65 shares. All position sizing, risk budgeting, broker fan-out, and trade copier allocations strictly calculate quantities as integer multiples of 65:

1 Lot

65 Shares

2 Lots

130 Shares

3 Lots

195 Shares

4 Lots

260 Shares

🏛️ NSE Exchange Holiday Preponement Architecture

Under National Stock Exchange (NSE) circulars and derivatives contract specifications, if a scheduled expiry date falls on an official exchange trading holiday or weekend, the expiry date automatically prepones to the immediately preceding active trading day.

Standard Tuesday Holiday Scenario

If Tuesday is a scheduled trading holiday (e.g. Dussehra on Oct 20, 2026), the contract expiry rolls back by 1 day to Monday (Oct 19, 2026). On Monday afternoon, the system activates the EXPIRY_GAMMA scaling profile, selects 0-DTE strikes, and manages gamma acceleration.

Consecutive Holiday Cascade Scenario

If Tuesday is a holiday AND Monday is also a holiday, the system iteratively rolls back across the weekend to Friday. The algorithm will never stop at Sunday or Saturday; it continues backward until a genuine exchange trading day is reached.

📅 Verified Real-World 2026 NSE Tuesday Holidays (Automatically Handled)

Holiday Name	Scheduled Expiry (Holiday)	Effective Trading Expiry	Preponement Shift	System Behavior
Dussehra	Tuesday, Oct 20, 2026	Monday, Oct 19, 2026	-1 Trading Day	0-DTE Gamma active on Monday; Tuesday market closed
Diwali Balipratipada	Tuesday, Nov 10, 2026	Monday, Nov 09, 2026	-1 Trading Day	0-DTE Gamma active on Monday; Tuesday market closed
Gurunanak Jayanti	Tuesday, Nov 24, 2026	Monday, Nov 23, 2026	-1 Trading Day	0-DTE Gamma active on Monday; Tuesday market closed

⚙️ Dynamic Future-Proof Configuration Hierarchy

To protect against future regulatory modifications (such as SEBI changing expiry days from Tuesday to Wednesday, or resizing lots from 65 to 50 or 75), the architecture implements a 4-tier configuration hierarchy:

Tier 1: Env Vars

EXPIRY_WEEKDAY=1
LOT_SIZE=65
NSE_HOLIDAYS=...

Highest Priority

Tier 2: YAML Config

config/risk.yaml
expiry_weekday: 1
calendar.holidays: []

File-based defaults

Tier 3: Python API

ExchangeCalendar.set_expiry_weekday()
ExchangeCalendar.add_holidays()

Runtime programmatic

Tier 4: Hard Invariants

Default: Tuesday (1)
Default: 65 Shares
Embedded 2025-27 Calendar

Fallback safety

Autonomous System Bug Audit, Configurable Architecture & Exchange Holiday Manifesto

🎯 Architectural Philosophy: Why Autonomous Algorithmic Systems Fail in Production

📋 Complete Forensic Bug Audit & Resolution Matrix

1. Feed Watchdog: Datetime Timezone Normalization

2. Position Sizer: Configurable Lot Size (Default 65 Shares)

3. Symbol Resolver: Tuesday Expiry & Calendar Delegation

🛡️ 18-Strategy Multi-Regime Adversary Validation Suite

📅 Tuesday Weekly Expiry Lifecycle & DTE Matrix

📦 NIFTY Contract Sizing (65 Shares / Lot)

🏛️ NSE Exchange Holiday Preponement Architecture

📅 Verified Real-World 2026 NSE Tuesday Holidays (Automatically Handled)

⚙️ Dynamic Future-Proof Configuration Hierarchy

AWS EC2 Production Instance Live Status

🧮 Interactive Holiday-Aware Expiry & Position Sizing Simulator