400 Bad RequestDon't retry
order canceled in the CTF exchange contract
The Polymarket CLOB API returns this with HTTP 400. Polymarket doesn't document a cause beyond the message.
Retry? Don't retry
Sending the same request again returns the same error. Change the request first.
Any authenticated CLOB endpoint can return this.
Handling it in code
The CLOB API returns errors as {"error": "..."}. It also rewrites status codes by message, so branch on the text: anything containing "not found" becomes 404 and anything containing "unauthorized" becomes 401.
r = session.post(url, json=payload, headers=headers)
if r.status_code >= 400:
msg = r.json().get("error", "")
if "order canceled in the CTF exchange contract" in msg:
raise ValueError(msg) # fix the request, don't retryRelated errors
For errors Polymarket doesn't document, like "order manager not ready" or 403s from the edge, see the full error guide.
Message and status from Polymarket's error reference, synced 2026-10-04.