order-lifecycle

Guide the design and implementation of order lifecycle management in trading systems. Owns FIX application-layer message flows (NewOrderSingle, ExecutionReport, cancel/replace) and order state. Use when building an order state machine for an OMS or EMS, handling cancel/replace race conditions, defining pre-submission validation rules (buying power, position limits, restricted lists), selecting order types and time-in-force instructions, designing multi-leg or OCO or bracket orders, building CAT-compliant audit trails, troubleshooting order rejections or unexpected state transitions, hardening an OMS against edge cases, or implementing order persistence and recovery for failover. Also covers execution-report handling, ClOrdID chaining, and partial fill aggregation. For FIX session management (logon, sequence gaps, disconnects) see exchange-connectivity.