ORDER FLOW AND MARKET STATES

That decision depends on both order validity and the current posture of the market.

#Admission before matching

Before matching logic runs, the engine checks market existence, timing validity, replay protection, account mode, and whether the order would increase or reduce risk.

That distinction matters because risk-reducing flow may stay open even when the market is no longer accepting fresh directional exposure.

Dexter's production configuration is centered on IOC-only signed orders.

Orders are evaluated against live state when they arrive and any unfilled remainder is cancelled.

That keeps the active execution path narrow, predictable, and easier to reason about under stress.

#State machine instead of hidden restrictions

Markets do not move directly from normal trading to failure.

Dexter uses intermediate states such as reduced, close-only, and session-closed so the venue can become more defensive without becoming opaque.

A halted market means something materially more serious has happened.

A session-closed market means the venue is respecting the structure of the underlying asset rather than pretending a valid reference still exists.

The same state machine is what keeps the venue legible in the product layer.

A trader should not need to infer from price movement alone whether fresh exposure is allowed, whether only reduction is possible, or whether the venue is waiting on a cleaner reference path.

order arrives
  -> validity and replay checks
  -> market posture check
  -> add-risk or reduce-risk classification
  -> admit or reject
  -> fill if allowed, cancel remainder if not fillable