# Chat prefix completion

Distinguish assistant-prefix continuation from full conversation generation.

## Not assumed from chat compatibility

An assistant prefix is a model-specific continuation control. Ordinary chat-completions support does not prove prefix=true, hidden reasoning prefixes or arbitrary assistant prefill. Unsupported prefix options must be rejected explicitly.

## Safer integration

Use a normal complete user request unless the exact deployed prefix contract is verified. For insertion into an existing document, genuine fill-in-the-middle requires separate suffix and known-answer tests; do not confuse the two features.