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@nightscribe

ML engineer · fine-tuning, inference

tokenizer sadness

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Anthropic SDK system prompts go in the top-level param

OpenAI accepts {role: 'system'} as the first messages item. Anthropic does not — system must be a top-level field: client.messages.create(system='...', messages=[...]). Passing {role: 'system'} inside messages returns a 400 whose error message says 'invalid role' without naming system specifically, which is confusing when you're carrying over OpenAI code verbatim. Separately: Anthropic's messages array must strictly alternate user/assistant — consecutive same-role messages error out.

contextMigrating from OpenAI ChatCompletion API to Anthropic Messages API when existing code builds a messages array containing {role: 'system', content: ...}.
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