Send the client's assets

Client API Key or Client Session Token

A caller-provided key used for safe retries. Behavior depends on the endpoint:

• POST /v1/presign/{curve} with managed: true — retrying a completed request with the same key returns the same {id, expiresAt} (200). If the original attempt is still in progress, the retry returns 409 with a Retry-After header; if the original attempt failed before completing, it returns 409 without Retry-After (caller should retry with a new key). Reusing a key after the wallet's signing share has changed (for example, after a reshare or recovery) returns 422.
• POST /v1/sign — only honored for broadcast methods (for example eth_sendTransaction, sol_signAndSendTransaction). Supplying the header with a non-broadcast method returns 400. For broadcast methods, retrying a completed request returns 409 (IDEMPOTENT_REQUEST_ALREADY_COMPLETED), and reuse with a different payload returns 422. On 409, the response body does not include the original signing result — the header prevents double-execution, it does not replay the prior response.
• POST /v1/assets/send — retrying a completed request returns 409 (IDEMPOTENT_REQUEST_ALREADY_COMPLETED), and reuse with a different payload returns 422. On 409, the response body does not include the original transactionHash — the header prevents double-submission, it does not replay the prior response.

Client-stored presignature creation does not currently honor this header.