Response streaming
Response streaming pipes the model's output token-by-token to the client as it's generated, so users see text appearing in real time instead of waiting for the full answer.
Streaming is mandatory for any user-facing LLM feature in 2026 — without it the user stares at a spinner for 5-30 seconds. Every major API supports server-sent events (SSE) or websocket streaming. The engineering trade-offs: streaming complicates error handling mid-response, makes structured-output mode (JSON) harder to validate progressively, and prevents the server from inspecting the full output before sending. For tool-use loops, stream the user-facing answer but buffer tool calls until complete.
When to use response streaming
- Any chat or assistant UX.
- Long-form generation where users want immediate feedback.
Common mistakes
- Streaming JSON without progressive validation — partial JSON breaks parsing.
- No abort/cancel on the client — runaway streams keep generating after the user navigates away.
FAQ
What is response streaming?
Response streaming pipes the model's output token-by-token to the client as it's generated, so users see text appearing in real time instead of waiting for the full answer.
When should I use response streaming?
Any chat or assistant UX. Long-form generation where users want immediate feedback.
What are the most common mistakes with response streaming?
Streaming JSON without progressive validation — partial JSON breaks parsing. No abort/cancel on the client — runaway streams keep generating after the user navigates away.
Related terms
- Context window — The context window is the maximum number of tokens — system prompt, conversation history, retrieved documents, and the response — that a language model can process in a single turn.
- AI agent — An AI agent is a system where a language model autonomously plans and executes a sequence of tool calls to accomplish a goal.
- System prompt — A system prompt is the high-priority instruction block that defines a model's role, constraints, and default behaviors for an entire conversation.
Last updated: 2026-06-01. Raw markdown: https://promtable.com/glossary/response-streaming.md.