User message
A user message is a single turn of input in a conversation with a language model, carrying the specific request and any material that request depends on.
Splitting instructions between a system prompt and a user message matters when calling an API directly. Stable behaviour goes in the system prompt; the particular task, its source material, and its one-off constraints go in the user message. Pasting everything into one block works in a chat interface but loses that separation.
Related terms
- System prompt
- A system prompt is a persistent instruction that sets a model’s role, rules, and boundaries for an entire conversation, separate from the individual messages a user sends.
- Assistant prefill
- An assistant prefill is text placed at the start of the model’s own reply so that it continues from there instead of choosing its own opening.
More on core concepts
See the full glossary, read the guides, or put it into practice in the prompt builder.