Periodic "Prompt is too long" for conversation but perhaps be clear about the remaining tokens

Periodically I get this

LLM request failed: status 400 Bad Request (url=http://169.254.169.254/gateway/llm/_/gateway/anthropic/v1/messages, model=claude-opus-4-5-20251101): {"type":"error","error":{"type":"invalid_request_error","message":"prompt is too long: 200251 tokens > 200000 maximum"},"request_id":"req_011CWdepJvA2D819tdYYq4h7"}

and can't send any more messages. @josharian gave me a tip offline which is to instead start a fresh conversation and reference the prior one. Let's figure out how to visually indicate this to a customer and to prevent scaring someone that perhaps their work was lost.