Invalid signature in thinking block? It is not rate limiting: a thinking signature in the history is invalid
From a real support ticket: a customer ran a task with thinking enabled in Cherry Studio’s Claude Agent mode. The main conversation never replied, the client showed “too many requests” and retried 10 times, yet the console logs showed normal billed requests. Those were the client’s small auxiliary requests. The cause was an empty signature on the first-turn thinking block in the history, which failed the provider’s check. The same history is sent on every retry, so retries always fail.
The new FAQ lists the four common causes (the client drops signatures, history is altered, switching models mid-conversation, switching keys or groups mid-conversation) and shows how to replay thinking blocks correctly in your own code. The fix is simple: start a new conversation, and use one model and one key per conversation. See How Do I Fix Claude’s Invalid Thinking Signature Error?.
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