@tanstack/ai-preact | TanStack AI 한국어

Preact hooks for TanStack AI, providing convenient Preact bindings for the headless client.

Installation

`useRegisterWebMCPTools(tools, options?)`

Register executable client tools after the Preact component mounts. Preact removes them on cleanup and replaces them when tools or options change.

For a complete setup and behavior guide, see WebMCP Tools.

import {
  useRegisterWebMCPTools,
  type UseRegisterWebMCPToolsOptions,
} from "@tanstack/ai-preact";
import { searchProducts } from "./tools";

const tools = [searchProducts];
const options: UseRegisterWebMCPToolsOptions<typeof tools> = {
  onError(error) {
    console.error(error);
  },
};

function ProductsPage() {
  useRegisterWebMCPTools(tools, options);
  return null;
}

UseRegisterWebMCPToolsOptions<TTools, TContext> contains toolOptions, context, and onError. The hook owns the registration signal.

The context field is required when a tool declares a required runtime context. Keep tools and options stable when their values do not change.

`usePageWebMCPTools(options?)`

Read the WebMCP tools on the page as client tools. The array starts empty and updates when the page adds or removes a tool. Pass it to useChat as tools.

import { usePageWebMCPTools } from "@tanstack/ai-preact";

export function useSameOriginPageTools() {
  return usePageWebMCPTools({
    filter: (tool) => tool.origin === location.origin,
  });
}

filter skips a tool when it returns false. onError gets a failed WebMCP read. For a complete guide, see Page WebMCP Tools in Chat.

`useChat(options?)`

Main hook for managing chat state in Preact with full type safety.

import { useChat, fetchServerSentEvents } from "@tanstack/ai-preact";
import { 
  createChatClientOptions, 
  type InferChatMessages 
} from "@tanstack/ai-client";
import { toolDefinition } from "@tanstack/ai";
import { z } from "zod";
import { useState } from "preact/hooks";

const updateUIDef = toolDefinition({
  name: "updateUI",
  description: "Show a notification in the UI",
  inputSchema: z.object({ message: z.string() }),
});

function ChatComponent() {
  const [, setNotification] = useState<string | null>(null);
  // Create client tool implementations
  const updateUI = updateUIDef.client((input) => {
    setNotification(input.message);
    return { success: true };
  });

  // Create typed tools array (no 'as const' needed!)
  const tools = [updateUI];

  const chatOptions = createChatClientOptions({
    connection: fetchServerSentEvents("/api/chat"),
    tools,
  });

  // Fully typed messages!
  type ChatMessages = InferChatMessages<typeof chatOptions>;

  const { messages, sendMessage, isLoading, error, addToolApprovalResponse } =
    useChat(chatOptions);

  return <div>{/* Chat UI with typed messages */}</div>;
}

Options

Extends ChatClientOptions from @tanstack/ai-client:

connection - Connection adapter (required)
tools? - Array of client tool implementations (with .client() method)
initialMessages? - Initial messages array
threadId? - The only identity for this chat. Required when persistence is on. If omitted, minted after mount.
forwardedProps? - Arbitrary client-controlled JSON forwarded to the server in the AG-UI RunAgentInput.forwardedProps field (e.g., { provider: 'openai', model: 'gpt-5.5' })
body? - Deprecated. Use forwardedProps instead. Still works for backward compatibility; values are merged into forwardedProps on the wire
byok? - Optional BYOK keyring from defineByok. On each send the client prepares the resolved provider and stamps x-byok-* request headers. Keys never go in the body
byokProvider? - Optional function that returns the provider slug for this chat. If it returns a slug, only that key is prepared and sent. Otherwise the merged provider from forwardedProps, body, and per-call sendMessage body is used. Later sources win. If no slug resolves, the send throws instead of attaching every stored key
context? - Typed client-local runtime context passed to client tool implementations. This value is not serialized to the server
onResponse? - Callback when response is received
onChunk? - Callback when stream chunk is received
onFinish? - Callback when response finishes
onError? - Callback when error occurs
onInterruptStateChange? - Callback when interrupt state changes; context source is hydrate for restored state and live for streamed or client-initiated updates
streamProcessor? - Stream processing configuration

Note: Client tools are now automatically executed - no onToolCall callback needed!

Returns

import type { UIMessage } from "@tanstack/ai-preact";
import type { ModelMessage } from "@tanstack/ai/client";
import type {
  MultimodalContent,
  SendMessageOptions,
} from "@tanstack/ai-client";

interface UseChatReturn {
  messages: UIMessage[];
  sendMessage: (
    content: string | MultimodalContent,
    options?: SendMessageOptions,
  ) => Promise<void>;
  append: (message: ModelMessage | UIMessage) => Promise<void>;
  addToolResult: (result: {
    toolCallId: string;
    tool: string;
    output: any;
    state?: "output-available" | "output-error";
    errorText?: string;
  }) => Promise<void>;
  addToolApprovalResponse: (response: {
    id: string;
    approved: boolean;
  }) => Promise<void>;
  reload: () => Promise<void>;
  stop: () => void;
  isLoading: boolean;
  isHydrating: boolean;
  error: Error | undefined;
  setMessages: (messages: UIMessage[]) => void;
  clear: () => void;
}

`useByok(client)`

Subscribe to a ByokClient snapshot in Preact.

import { useByok } from "@tanstack/ai-preact";
import { byok } from "./byok";

export function KeyStatus() {
  const snapshot = useByok(byok);
  const openai = snapshot.status.openai;
  const last4 = openai && "masked" in openai ? openai.masked : "No key";
  return <p>{last4}</p>;
}

snapshot has status, locked, and prompt. Call byok.update(provider, value) from your own UI to save a key. See Bring Your Own Key.

Connection Adapters

Re-exported from @tanstack/ai-client for convenience:

import {
  fetchServerSentEvents,
  fetchHttpStream,
  fetchJson,
  stream,
  type ConnectionAdapter,
} from "@tanstack/ai-preact";

Example: Basic Chat

import { useState } from "preact/hooks";
import { useChat, fetchServerSentEvents } from "@tanstack/ai-preact";

export function Chat() {
  const [input, setInput] = useState("");

  const { messages, sendMessage, isLoading } = useChat({
    connection: fetchServerSentEvents("/api/chat"),
  });

  const handleSubmit = (e: Event) => {
    e.preventDefault();
    if (input.trim() && !isLoading) {
      sendMessage(input);
      setInput("");
    }
  };

  return (
    <div>
      <div>
        {messages.map((message) => (
          <div key={message.id}>
            <strong>{message.role}:</strong>
            {message.parts.map((part, idx) => {
              if (part.type === "thinking") {
                return (
                  <div key={idx} class="text-sm text-gray-500 italic">
                    💭 Thinking: {part.content}
                  </div>
                );
              }
              if (part.type === "text") {
                return <span key={idx}>{part.content}</span>;
              }
              return null;
            })}
          </div>
        ))}
      </div>
      <form onSubmit={handleSubmit}>
        <input
          value={input}
          onInput={(e) => setInput(e.currentTarget.value)}
          disabled={isLoading}
        />
        <button type="submit" disabled={isLoading}>
          Send
        </button>
      </form>
    </div>
  );
}

Example: Tool Approval

import { useChat, fetchServerSentEvents } from "@tanstack/ai-preact";

export function ChatWithApproval() {
  const { messages, sendMessage, addToolApprovalResponse } = useChat({
    connection: fetchServerSentEvents("/api/chat"),
  });

  return (
    <div>
      {messages.map((message) =>
        message.parts.map((part) => {
          if (
            part.type === "tool-call" &&
            part.state === "approval-requested" &&
            part.approval
          ) {
            return (
              <div key={part.id}>
                <p>Approve: {part.name}</p>
                <button
                  onClick={() =>
                    addToolApprovalResponse({
                      id: part.approval!.id,
                      approved: true,
                    })
                  }
                >
                  Approve
                </button>
                <button
                  onClick={() =>
                    addToolApprovalResponse({
                      id: part.approval!.id,
                      approved: false,
                    })
                  }
                >
                  Deny
                </button>
              </div>
            );
          }
          return null;
        })
      )}
    </div>
  );
}

Example: Client Tools with Type Safety

import { useChat, fetchServerSentEvents } from "@tanstack/ai-preact";
import { 
  createChatClientOptions, 
  type InferChatMessages 
} from "@tanstack/ai-client";
import { toolDefinition } from "@tanstack/ai";
import { z } from "zod";
import { useState } from "preact/hooks";

const updateUIDef = toolDefinition({
  name: "updateUI",
  description: "Show a notification in the UI",
  inputSchema: z.object({ message: z.string(), type: z.string() }),
});

const saveToStorageDef = toolDefinition({
  name: "saveToStorage",
  description: "Save a value to localStorage",
  inputSchema: z.object({ key: z.string(), value: z.string() }),
});

export function ChatWithClientTools() {
  const [notification, setNotification] = useState<{ message: string; type: string } | null>(null);

  // Create client implementations
  const updateUI = updateUIDef.client((input) => {
    // ✅ input is fully typed!
    setNotification({ message: input.message, type: input.type });
    return { success: true };
  });

  const saveToStorage = saveToStorageDef.client((input) => {
    localStorage.setItem(input.key, input.value);
    return { saved: true };
  });

  // Create typed tools array (no 'as const' needed!)
  const tools = [updateUI, saveToStorage];

  const { messages, sendMessage } = useChat({
    connection: fetchServerSentEvents("/api/chat"),
    tools, // ✅ Automatic execution, full type safety
  });

  return (
    <div>
      {messages.map((message) =>
        message.parts.map((part) => {
          if (part.type === "tool-call" && part.name === "updateUI") {
            // ✅ part.input and part.output are fully typed!
            return <div>Tool executed: {part.name}</div>;
          }
          return null;
        })
      )}
    </div>
  );
}

`createChatClientOptions(options)`

Helper to create typed chat options (re-exported from @tanstack/ai-client).

import { 
  createChatClientOptions, 
  type InferChatMessages 
} from "@tanstack/ai-client";
import { fetchServerSentEvents } from "@tanstack/ai-preact";
import { tool1, tool2 } from "./tools";

// Create typed tools array (no 'as const' needed!)
const tools = [tool1, tool2];

const chatOptions = createChatClientOptions({
  connection: fetchServerSentEvents("/api/chat"),
  tools,
});

type Messages = InferChatMessages<typeof chatOptions>;

Types

Re-exported from @tanstack/ai-client:

UIMessage<TTools> - Message type with tool type parameter
MessagePart<TTools> - Message part with tool type parameter
TextPart - Text content part
ThinkingPart - Thinking content part
ToolCallPart<TTools> - Tool call part (discriminated union)
ToolResultPart - Tool result part
ChatClientOptions<TTools, TContext> - Chat client options with typed client runtime context
ConnectionAdapter - Connection adapter interface
InferChatMessages<T> - Extract message type from options

Re-exported from @tanstack/ai:

toolDefinition() - Create isomorphic tool definition
ToolDefinitionInstance - Tool definition type
ClientTool - Client tool type
ServerTool - Server tool type

Next Steps

Getting Started - Learn the basics
Tools Guide - Learn about the isomorphic tool system
Client Tools - Learn about client-side tools