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[Bug]: This model does not support assistant message prefill. The conversation must end with a user message. #463

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[Bug]: This model does not support assistant message prefill. The conversation must end with a user message.#463
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@frap129
frap129
opened on Mar 26, 2026

Bug Description

Ever since 3.1.0, I've been occasionally getting an error in opencode: "This model does not support assistant message prefill. The conversation must end with a user message.". This halts the agents, and I have to prompt it to continue. This is usually preceeded by either a raw dcp tag, or a tool call inserted into the chat raw:

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Expected Behavior

Pre 3.1 behavior, like 3.0.4

Debug Context Logs

None collected, ~/.config/opencode/logs empty

Tool Call Details

No response

DCP Version

3.1.2

Opencode Version

1.3.2

Model

Claude Opus 4

Additional Context

No response

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