curl --request POST \
--url https://api.limitless.exchange/heartbeats \
--header 'Content-Type: application/json' \
--header 'lmts-api-key: <api-key>' \
--data '
{
"cancelAt": 1800000010000
}
'{
"errorCode": "cancellation_in_progress",
"message": "Cancellation in progress"
}Trading
Market Maker Heartbeat
A safety timer for your orders. Set a deadline, then keep extending it while your trading service runs. If updates stop and the deadline passes, Limitless starts canceling your open orders across all markets. This does not block new orders, so stop placing them if an update fails.
POST
/
heartbeats
curl --request POST \
--url https://api.limitless.exchange/heartbeats \
--header 'Content-Type: application/json' \
--header 'lmts-api-key: <api-key>' \
--data '
{
"cancelAt": 1800000010000
}
'{
"errorCode": "cancellation_in_progress",
"message": "Cancellation in progress"
}Set or update a deadline
SendcancelAt as a Unix timestamp in milliseconds. It must be a whole number at least five seconds later than server time. Each successful request replaces your previous deadline. The timestamp below is an example; calculate a new one for each request.
{
"cancelAt": 1800000010000
}
Turn off the timer
Send an empty JSON object to remove your deadline:{}
Authentication and results
Authenticate as the profile whose orders you want to cover. If you use a scoped API token, it needs thetrading scope. Sign the exact JSON body and /heartbeats path; see HMAC request signing. This endpoint does not accept onBehalfOf: a partner token cannot set a deadline for a sub-account.
200 OK: deadline set, updated, or removed. No response data is returned.400 Bad Request:cancelAtis invalid or too close to server time.401 Unauthorized: authentication or profile is missing.403 Forbidden: the API token lacks thetradingscope.409 ConflictwitherrorCode: "cancellation_in_progress": the deadline passed and cancellation has started. Stop placing orders. You can set a new deadline after cancellation finishes.
Authorizations
Scoped API token with HMAC-SHA256 signing. Requires three headers: lmts-api-key (token ID), lmts-timestamp (ISO-8601), lmts-signature (Base64-encoded HMAC). See Authentication docs for details.
Body
application/json
Include cancelAt to set or update a deadline; send {} to turn off the timer.
Future Unix timestamp in milliseconds, at least five seconds after server time. Leave out to turn off the timer.
Example:
1800000010000
Response
Deadline set, updated, or removed; no response data