No. FIX clients are not required to send new exchange codes immediately. IBKR will try to resolve the contract based on the exchange received from the FIX client. If the provided exchange code is one of the old codes, IBKR will automatically switch to the new exchange code to resolve the contract. When IBKR sends back the order status and trades, the original exchange code received from the client will be provided.
Are FIX Clients required to send the new exchange code in New Order messages from day 1?
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Taiwan Stock Exchange (TWSE) equities offering
Are TWS Api Clients required to send the new Exchange name from day 1 a product moves from oldExch to newExch ?
Which FIX Tags are in scope for IB's Exchange translation?
Which Exchange Code will Dropcopy FIX sessions receive in the execution report?