Streaming structured output for TypeScript

schema-stream

Typed, schema-shaped JSON snapshots while the response is still arriving.

Read the docs Try the playground GitHub npm

bun add schema-stream zod

snapshot 0parsing every chunk

{
  "checks": [
    {
      "label": "",
      "state": ""
    }
  ],
  "metrics": {
    "score": null
  },
  "summary": "",
  "title": ""
}

Why it exists

Use the fields that are ready. Keep streaming the rest.

Accept arbitrary text and UTF-8 chunk boundaries from provider streams.

Materialize typed snapshots according to an explicit emission policy.

React once when nested keys or values complete, without rescanning the tree.

Less repeated work

Keep parser state. Do not reparse the growing prefix.

SchemaStream consumes each incoming chunk against the parser state it already has. It materializes independent object snapshots only at the cadence your application chooses, then hands those objects directly to application code.

provider chunk → SchemaStream.iterate() → typed object snapshotsnapshotPolicy → control materialization and update frequency

See how the approach works

01
Arbitrary chunks arrive
UTF-8, strings, tokens, and nested values may split anywhere.
02
State advances once
The tokenizer and parser continue from the previous boundary.
03
Your code receives an object
Render a snapshot or react when a completed value matters.

Integrations

One parser boundary. The SDK stays your choice.

OpenAI Agents SDK Vercel AI SDK Mastra Bun WebSocket

Progressive dashboard

See every policy shape the same response.

Open playground