I mean I would assume they do, but just wonder if there are ever any severe "gotchas" with a stock split with certain existing buy/sell arrangements, or derivatives etc.
There's a million tiny details like this that can cause consequences that are both different from what a customer intended and what our terms with said customer states, so making sure it's all handled in a safe way is just part of daily business.
Options are also split to take the stock split into account.
Trading platforms shouldn't have to do anything unless they are faking GTC orders by resending them out each day as Day orders.
But if your vendor is doing that then, get a new vendor as that's completely bush league.
Exchanges do not receive or handle GTC or GTD orders, see for example the NYSE pillar spec.[1]
Broker-dealers handle stock splits and the behavior varies according to your broker. Some brokers will request the broker-dealer cancel all orders back, but most brokers allow limit prices to be adjusted for orders "below the market" (buy limit orders and sell stop orders). The Fidelity FAQ is an illustrative one.[2]
I'm not sure what a "vendor" is here, but brokers send GTC orders to broker-dealers, who forward them to the exchange every day as a day order. This behavior is industry standard and certainly not bush league.
[1] https://www.nyse.com/publicdocs/NYSE_Pillar_Gateway_FIX_Prot...
https://www.nasdaqtrader.com/content/ProductsServices/Tradin...
it is true the the NYSE eliminated GTC orders. That just means you can't use them on NYSE, which doesn't affect my point:)
You'll have to flesh out your point more if you still feel like you have one:)
Given that I've written more than one trading systems for a living, I'm going to take my 20 years of experience over a random internet troll.
Here is the specific rule relating to adjusting the price of open orders: https://www.finra.org/rules-guidance/rulebooks/finra-rules/5...