Vibe Coding
Anthropic's Fable 5.1 guide ships a copy-paste block that stops an agent ending its turn on a promise
The 'Finish the whole task' section names the failure directly: without a nudge, Fable 5.1 describes what it would do next ('Next, I'll…') or asks permission for a step the original request already covered. The fix is two system-prompt blocks, and the guide says the opening sentence carries most of the effect and should be kept verbatim: 'You are operating autonomously. The user is not watching in real time and cannot answer questions mid-task.' The second block defines the user's request as the scope of the deliverable and tells the model a decided step is something to run, not to announce.
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