Type Alias: TypedStreamChunk<TTools>

type TypedStreamChunk<
  TTools extends ReadonlyArray<Tool<any, any, any>> = ReadonlyArray<Tool<any, any, any>>,
> =
  HasTypedTools<TTools> extends true
    ?
        | Exclude<
            StreamChunk,
            | { type: 'TOOL_CALL_START' }
            | { type: 'TOOL_CALL_END' }
            | { type: 'CUSTOM' }
          >
        | DistributedToolCallStart<TTools>
        | DistributedToolCallEnd<TTools>
        | TaggedCustomEvent
    : StreamChunk;

Defined in: packages/typescript/ai/src/types.ts

A variant of StreamChunk parameterized by the tools array. When specific tool types are provided (e.g. from chat({ tools: [myTool] })):

TOOL_CALL_START and TOOL_CALL_END events form a discriminated union over tool names.
Checking toolName === 'x' narrows input to that specific tool's input type.
TOOL_CALL_END events have input typed per-tool via Standard Schema inference.
CUSTOM events with literal tagged names (structured-output.start, structured-output.complete, approval-requested, tool-input-available) narrow value to the corresponding payload via the TaggedCustomEvent union.

When tools are untyped or absent, TypedStreamChunk falls back to plain StreamChunk so existing consumers that pass streams as AsyncIterable<StreamChunk> keep working.

This is the type returned by chat() when streaming is enabled (the default). You don't typically need to reference it directly unless annotating function parameters or return types.

import { chat, toolDefinition, type TypedStreamChunk } from "@tanstack/ai";
import { openaiText } from "@tanstack/ai-openai";
import { z } from "zod";

const weatherTool = toolDefinition({
  name: "get_weather",
  description: "Get weather for a location",
  inputSchema: z.object({ location: z.string() }),
});

const searchTool = toolDefinition({
  name: "search",
  description: "Search the web",
  inputSchema: z.object({ query: z.string() }),
});

// Inferred from `chat()` — typed tool call events plus tagged CUSTOM events
const stream = chat({
  adapter: openaiText("gpt-5.5"),
  messages,
  tools: [weatherTool, searchTool],
});

// Explicit annotation
type Chunk = TypedStreamChunk<[typeof weatherTool, typeof searchTool]>;