The signature type tells Polymarket's exchange which wallet arrangement is signing an order — a plain externally owned account, the proxy wallet created by the Polymarket interface, or a Safe-based smart wallet. Sending the wrong type causes signature validation to fail even when the signature itself is correct.
Per the setup documented in our build guide, type 1 corresponds to the Polymarket-UI proxy arrangement and type 2 to Safe-based smart wallets. Match the type to how the account was actually created rather than copying a value from an example.
API keys are bound to the address that derived them, which is a related trap: a key generated by one address cannot be used to trade another account's positions without the correct funder and signature type in place.
Copying a signature type out of an example rather than matching how the account was actually created. The signature itself is valid, so the error looks like a signing bug rather than a configuration one.
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