Files
Alem Tuzlak 8a5a976f1a feat(core): expose webmcp-enabled frontend tools to browser agents (#6847)
## What does this PR do?

Hooks can now expose a frontend tool to browser agents through the
WebMCP browser API, next to the normal agent registration. Set `webmcp:
true`, or pass `{ annotations }` for WebMCP hints:

```ts
useFrontendTool({
  name: "searchOrders",
  description: "Search the signed-in user's orders by status",
  parameters: z.object({ status: z.enum(["open", "shipped", "delivered"]) }),
  handler: async ({ status }) => searchOrders(status),
  webmcp: { annotations: { readOnlyHint: true } },
});
```

How it works:

1. `FrontendTool` in `@copilotkit/core` gains the `webmcp` option. A new
`WebMCPRegistry` registers the tool on `document.modelContext` with its
name, description, input schema, and annotations. `execute` runs the
tool's own handler. The handler context has no `agent` there.
2. Every tool registry change in `RunHandler` reconciles the WebMCP
registrations. The same availability rules apply as for the agent tool
list. Removing a tool aborts its registration signal, and the browser
then unregisters it.
3. Each adapter picks the option up from core: v2 `useFrontendTool`
(React, Vue, React Native), the v1 `useCopilotAction` and
`useFrontendTool` wrappers (React, Vue), and Angular's
`registerFrontendTool`. Where WebMCP is not available (SSR, React
Native, browsers without the API), registration is a no-op.

The `webmcp` prop is documented on the React, Vue, and Angular reference
pages in shell-docs.

## Related PRs and Issues

- None.

## Checklist

- [x] I have read the [Contribution
Guide](https://github.com/copilotkit/copilotkit/blob/master/CONTRIBUTING.md)
- [x] If the PR changes or adds functionality, I have updated the
relevant documentation
- [ ] "Allow edits by maintainers" is checked (lets us help iterate on
your PR directly — faster turnaround for everyone)

## Testing

**Commands run**

- `pnpm nx run-many -t check-types
--projects=@copilotkit/core,@copilotkit/react-core,@copilotkit/vue,@copilotkit/angular`
— all pass.
- Full test suites: core (829 tests), vue (103), and angular pass.
react-core passes standalone (1589 tests). Under the lefthook pre-commit
hook, react-core flakes on pre-existing e2e tests (A2UI, MCP Apps) that
do not touch this code. Those tests pass when run alone.

**Manual test**

Requires Chrome 149+ with the WebMCP origin trial, or the testing flag.

1. Enable `chrome://flags/#enable-webmcp-testing`, then relaunch Chrome.
2. In an app that uses CopilotKit, register a tool with `webmcp: true`.
3. Run `await document.modelContext.getTools()` in DevTools. The tool is
listed with its schema and annotations.
4. Unmount the hook. Run the command again. The tool is gone.

**How this PR makes testing easy**

The behavior has automated tests on this branch:

- `packages/core/src/core/__tests__/run-handler-webmcp.test.ts` — 15
tests with a `document.modelContext` stub: registration, annotations,
unregistration, availability rules, name collisions, stale-rejection
races, and handler execution.
-
`packages/react-core/src/v2/hooks/__tests__/use-frontend-tool-webmcp.test.tsx`
and the mirrored
`packages/vue/src/v2/hooks/__tests__/use-frontend-tool-webmcp.test.ts` —
pass-through, re-registration, and agent-scoped cases at the hook level.
- `packages/vue/src/hooks/__tests__/use-frontend-tool-webmcp.test.ts` —
reactive `webmcp` getters through the v1 Vue API.

## Risk / rollback

Low. The feature is opt-in per tool. Without `webmcp`, no code path
changes. Where WebMCP is unsupported, registration is a no-op. Revert
this PR to roll back.

## Public API change

New optional `webmcp` prop on frontend tool registrations. Existing call
sites do not change.

**Before**

```ts
useFrontendTool({
  name: "searchOrders",
  description: "Search orders by status",
  parameters: z.object({ status: z.string() }),
  handler: async ({ status }) => searchOrders(status),
});
```

**After**

```ts
useFrontendTool({
  name: "searchOrders",
  description: "Search orders by status",
  parameters: z.object({ status: z.string() }),
  handler: async ({ status }) => searchOrders(status),
  webmcp: { annotations: { readOnlyHint: true } },
});
```


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
  * Tools can now be exposed to browser agents through WebMCP.
* Added support for custom annotations and automatic parameter schema
generation.
* WebMCP registrations stay synchronized as tools are added, removed,
enabled, or updated.
  * Available across Angular, React, and Vue tool APIs.
* WebMCP reuses existing handlers and safely does nothing when
unavailable.

* **Documentation**
* Added usage guidance and examples for configuring WebMCP-enabled
tools.
  * Documented that WebMCP invocations do not include an agent context.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
2026-09-03 14:15:29 +02:00
..
2026-04-10 23:38:59 +00:00
2026-09-01 17:59:58 +00:00

CopilotKit for Angular

First-party Angular bindings for CopilotKit core and AG-UI agents. The package ships standalone chat, popup, and sidebar components as well as signal-based headless APIs, tool and activity renderers, threads, memories, interrupts, attachments, A2UI, Open Generative UI, and opt-in MCP Apps support.

Want to contribute? Read the Angular contribution guide.

Installation

# npm
npm install @copilotkit/angular

Peer dependencies you provide in your app:

  • @angular/core and @angular/common (Angular 22)
  • @angular/cdk (match your Angular major)
  • rxjs 7.8 or newer

The exact versions exercised by the packed-consumer release matrix are stored in package.json under copilotkit.angularSupport. The library is compiled at the Angular 22 baseline and installed with strict peer checking against that supported major.

Quick start

1) Provide CopilotKit

Configure runtime and tools in your app config:

import { ApplicationConfig } from "@angular/core";
import { provideCopilotKit } from "@copilotkit/angular";

export const appConfig: ApplicationConfig = {
  providers: [
    provideCopilotKit({
      runtimeUrl: "http://localhost:3001/api/copilotkit",
      headers: { Authorization: "Bearer ..." },
      properties: { app: "demo" },
    }),
  ],
};

2) Build a custom UI with injectAgentStore

import { Component, inject, signal } from "@angular/core";
import { Message } from "@ag-ui/client";
import { CopilotKit, injectAgentStore } from "@copilotkit/angular";
import { randomUUID } from "@copilotkit/shared";

@Component({
  template: `
    @for (let message of messages(); track message.id) {
      <div>
        <em>{{ message.role }}</em>
        <p>{{ message.content }}</p>
      </div>
    }

    <input
      [value]="input()"
      (input)="input.set($any($event.target).value)"
      (keyup.enter)="send()"
    />
    <button (click)="send()" [disabled]="store().isRunning()">Send</button>
  `,
})
export class HeadlessChatComponent {
  readonly copilotKit = inject(CopilotKit);
  readonly store = injectAgentStore("default");
  readonly messages = this.store().messages;

  readonly input = signal("");

  async send() {
    const content = this.input().trim();
    if (!content) return;

    const agent = this.store().agent;

    agent.addMessage({
      id: randomUUID(),
      role: "user",
      content,
    });

    this.input.set("");

    await this.copilotKit.core.runAgent({ agent });
  }
}

The agent is an AG-UI AbstractAgent. Refer to your AG-UI agent implementation for available methods and message formats.

Core configuration

CopilotKitConfig

provideCopilotKit accepts a CopilotKitConfig object:

export interface CopilotKitConfig {
  runtimeUrl?: string;
  headers?: Record<string, string>;
  credentials?: RequestCredentials;
  licenseKey?: string;
  properties?: Record<string, unknown>;
  agents?: Record<string, AbstractAgent>;
  selfManagedAgents?: Record<string, AbstractAgent>;
  tools?: ClientTool[];
  renderToolCalls?: RenderToolCallConfig[];
  renderActivityMessages?: RenderActivityMessageConfig[];
  suggestionsConfig?: SuggestionsConfig[];
  frontendTools?: FrontendToolConfig[];
  humanInTheLoop?: HumanInTheLoopConfig[];
  defaultToolRendering?: boolean;
  a2ui?: A2UIConfig;
  openGenerativeUI?: OpenGenerativeUIConfig;
}
  • runtimeUrl: URL to your CopilotKit runtime.
  • headers: Default headers sent to the runtime.
  • credentials: Fetch credentials mode. Use "include" for cross-origin HTTP-only cookies.
  • properties: Arbitrary props forwarded to agent runs.
  • agents: Local, in-browser agents keyed by agentId.
  • selfManagedAgents: AG-UI agents managed directly by the application.
  • tools: Tool definitions advertised to the runtime (no handler).
  • renderToolCalls: Components to render tool calls in the UI.
  • renderActivityMessages: Components to render AG-UI activity messages.
  • suggestionsConfig: Static or runtime-generated chat suggestions.
  • frontendTools: Client-side tools with handlers.
  • humanInTheLoop: Tools that pause for user input.
  • defaultToolRendering: Opt in to the text-only renderer for unknown tools. It is disabled by default so missing renderers remain visible integration errors rather than silently changing the experience.
  • a2ui: Theme, catalog, schema, loading UI, and recovery policy for A2UI.
  • openGenerativeUI: Sandboxed UI functions and optional design guidance.

Injection helpers

  • provideCopilotKit(config): Provider for CopilotKitConfig.

CopilotKit service

Readonly signals

  • agents: Signal<Record<string, AbstractAgent>>
  • runtimeConnectionStatus: Signal<CopilotKitCoreRuntimeConnectionStatus>
  • runtimeUrl: Signal<string | undefined>
  • runtimeTransport: Signal<CopilotRuntimeTransport> ("rest" | "single")
  • headers: Signal<Record<string, string>>
  • credentials: Signal<RequestCredentials | undefined>
  • toolCallRenderConfigs: Signal<RenderToolCallConfig[]>
  • clientToolCallRenderConfigs: Signal<FrontendToolConfig[]>
  • humanInTheLoopToolRenderConfigs: Signal<HumanInTheLoopConfig[]>

Methods

  • getAgent(agentId: string): AbstractAgent | undefined
  • addFrontendTool(config: FrontendToolConfig & { injector: Injector }): void
  • addRenderToolCall(config: RenderToolCallConfig): void
  • addHumanInTheLoop(config: HumanInTheLoopConfig): void
  • removeTool(toolName: string, agentId?: string): void
  • updateRuntime(options: { runtimeUrl?: string; runtimeTransport?: CopilotRuntimeTransport; headers?: Record<string,string>; credentials?: RequestCredentials; properties?: Record<string, unknown>; agents?: Record<string, AbstractAgent>; selfManagedAgents?: Record<string, AbstractAgent>; }): void

Advanced

  • core: The underlying CopilotKitCore instance.

Agents

injectAgentStore

const store = injectAgentStore("default");
// or: injectAgentStore(signal(agentId))

Returns a Signal<AgentStore>. The store exposes:

  • agent: AbstractAgent
  • messages: Signal<Message[]>
  • state: Signal<any>
  • isRunning: Signal<boolean>
  • teardown(): Clean up subscriptions

If the agent is not available locally but a runtimeUrl is configured, a proxy agent is created while the runtime connects. If the agent still cannot be resolved, an error is thrown that includes the configured runtime and known agent IDs.

CopilotkitAgentFactory

Advanced factory for creating AgentStore signals. Most apps should use injectAgentStore instead.

Agent context

connectAgentContext

Connect AG-UI context to the runtime (auto-cleanup when the effect is destroyed):

import { connectAgentContext } from "@copilotkit/angular";

connectAgentContext({
  description: "User preferences",
  value: { theme: "dark" },
});

You must call it within an injection context (e.g., inside a component constructor or runInInjectionContext), or pass an explicit Injector:

connectAgentContext(contextSignal, { injector });

Tools and tool rendering

Types

export interface RenderToolCallConfig<Args> {
  name: string;              // tool name, or "*" for wildcard
  args: z.ZodType<Args>;      // Zod schema for args
  component: Type<ToolRenderer<Args>>;
  agentId?: string;           // optional agent scope
}

export interface FrontendToolConfig<Args> {
  name: string;
  description: string;
  parameters: z.ZodType<Args>;
  component?: Type<ToolRenderer<Args>>; // optional UI renderer
  handler: (args: Args, context: FrontendToolHandlerContext) => Promise<unknown>;
  agentId?: string;
}

export interface HumanInTheLoopConfig<Args> {
  name: string;
  description: string;
  parameters: z.ZodType<Args>;
  component: Type<HumanInTheLoopToolRenderer<Args>>;
  agentId?: string;
}

export type ClientTool<Args> = Omit<FrontendTool<Args>, \"handler\"> & {
  renderer?: Type<ToolRenderer<Args>>;
};

Renderer components receive a signal:

export interface ToolRenderer<Args> {
  toolCall: Signal<AngularToolCall<Args>>;
}

export interface HumanInTheLoopToolRenderer<Args> {
  toolCall: Signal<HumanInTheLoopToolCall<Args>>; // includes respond(result)
}

AngularToolCall / HumanInTheLoopToolCall expose args, status ("in-progress" | "executing" | "complete"), and result.

Register tools with DI

These helpers auto-remove tools when the current injection context is destroyed: Call them from an injection context (e.g., a component constructor, directive, or runInInjectionContext).

import {
  registerFrontendTool,
  registerRenderToolCall,
  registerHumanInTheLoop,
} from "@copilotkit/angular";
import { z } from "zod";

registerFrontendTool({
  name: "lookup",
  description: "Fetch a record",
  parameters: z.object({ id: z.string() }),
  handler: async ({ id }) => ({ id, ok: true }),
});

registerRenderToolCall({
  name: "*", // wildcard renderer
  args: z.any(),
  component: MyToolCallRenderer,
});

registerHumanInTheLoop({
  name: "approval",
  description: "Request approval",
  parameters: z.object({ reason: z.string() }),
  component: ApprovalRenderer,
});

Configure tools in provideCopilotKit

provideCopilotKit({
  frontendTools: [
    /* FrontendToolConfig[] */
  ],
  renderToolCalls: [
    /* RenderToolCallConfig[] */
  ],
  humanInTheLoop: [
    /* HumanInTheLoopConfig[] */
  ],
  tools: [
    /* ClientTool[] */
  ],
});

tools are advertised to the runtime. If you include renderer + parameters on a ClientTool, CopilotKit will also register a renderer for tool calls.

Prebuilt UI

All UI exports are standalone Angular components. Import the component classes directly and import @copilotkit/angular/styles.css once in the application's global stylesheet.

Full-page chat

import { Component } from "@angular/core";
import { CopilotChat } from "@copilotkit/angular";

@Component({
  selector: "app-assistant",
  imports: [CopilotChat],
  template: `<copilot-chat [agentId]="'default'" />`,
})
export class AssistantComponent {}

Use CopilotPopup for a floating dialog and CopilotSidebar for responsive overlay or docked presentation. Their open inputs are model signals, so [(open)] supports controlled application state. Both include focus trapping, Escape handling, focus restoration, accessible dialog naming, reduced-motion behavior, and safe-area-aware mobile layouts.

import { Component, signal } from "@angular/core";
import { CopilotPopup, CopilotSidebar } from "@copilotkit/angular";

@Component({
  imports: [CopilotPopup, CopilotSidebar],
  template: `
    <copilot-popup [(open)]="popupOpen" title="Support assistant" />
    <copilot-sidebar
      [(open)]="sidebarOpen"
      mode="docked"
      position="right"
      title="Workspace assistant"
    />
  `,
})
export class AssistantSurfacesComponent {
  readonly popupOpen = signal(false);
  readonly sidebarOpen = signal(false);
}

CopilotChatView, message, input, toolbar, button, attachment, and slot components are supported public customization primitives. See API.md for the exhaustive export inventory; use the higher-level components unless you are replacing part of the default composition.

RenderToolCalls component

RenderToolCalls renders tool call components under an assistant message based on registered render configs.

<copilot-render-tool-calls
  [message]="assistantMessage"
  [messages]="messages"
  [isLoading]="isRunning"
></copilot-render-tool-calls>

Inputs:

  • message: AssistantMessage (must include toolCalls)
  • messages: full Message[] list (used to find tool results)
  • isLoading: whether the agent is currently running

Tool arguments are parsed with partialJSONParse, so incomplete JSON during streaming still renders.

Runtime notes

  • Set runtimeUrl to your CopilotKit runtime endpoint.
  • If you need to change runtime settings at runtime, call CopilotKit.updateRuntime(...).
  • runtimeTransport supports "rest" or "single" (SSE single-stream transport).
  • For cross-origin cookie authentication, set credentials: "include" and enable credentialed CORS for the Angular app's exact origin.

Activity renderers and generative UI

Register application activity renderers with registerRenderActivityMessage or the renderActivityMessages provider option. Application registrations take precedence over optional built-ins.

  • A2UI is enabled when the runtime advertises the capability or when a2ui.catalog is supplied. An explicit catalog enables its renderers and agent context even when runtime /info does not advertise A2UI, matching the React provider contract. Configure recovery exposure independently of server-provided lifecycle content.
  • Open Generative UI is enabled with openGenerativeUI: { ... }. Generated UI runs in an isolated WebSandbox; expose only narrowly scoped sandboxFunctions and never place credentials in browser configuration.
  • MCP Apps is intentionally a secondary entry point. Add provideMCPApps() to application providers and import advanced host APIs from @copilotkit/angular/mcp-apps. MCP resource and tool requests travel through the selected AG-UI agent; the browser provider does not accept a server URL. The renderer uses the same inline srcdoc sandbox, sandbox permissions, and resource-domain CSP as the React SDK.

Lifecycle and cleanup

Call injectAgentStore, connectAgentContext, registerFrontendTool, registerRenderToolCall, registerRenderActivityMessage, injectInterrupt, injectThreads, and injectMemories from an Angular injection context. The helpers bind subscriptions, effects, timers, runtime registrations, and observers to the owning DestroyRef. Changing a signal-based agent ID tears down the previous agent subscription before connecting the replacement.

Do not create these helpers in module-level code or cache an injected controller beyond the lifetime of its injector. AgentStore.teardown() is public for advanced manually constructed stores; stores returned by injectAgentStore are cleaned up automatically and should not need a manual call.

Application-owned asynchronous work remains application-owned. Cancel fetches or other side effects started by a frontend-tool handler when its host is destroyed, and do not resolve an interrupt after its controller has left the view.

SSR, hydration, and zoneless Angular

The package is designed for standalone, OnPush, signal-based applications and is tested with provideZonelessChangeDetection(). No Zone.js dependency is required. Keep application state in signals or Angular outputs so zoneless change detection can observe updates.

Browser-only DOM setup is deferred to render lifecycle hooks or guarded by the platform where the package owns it. For SSR and hydration:

  • provide the same CopilotKit configuration and initial open/agentId values on the server and first client render;
  • do not access returned agents or run tools during server rendering;
  • make runtime URLs absolute when the server and browser use different origins, or proxy a same-origin /api/copilotkit endpoint;
  • enable A2UI, Open Generative UI, audio recording, and MCP Apps in the browser; their interactive sandboxes, custom elements, media APIs, and iframes become active after hydration;
  • avoid branching the component tree on window before hydration. Use Angular platform guards and afterNextRender for application-owned browser work.

Public API contract

API.md lists every supported export from the root and MCP Apps entry points and identifies the single internal extension token. A package test compares that inventory to TypeScript's resolved entry-point exports so a new public symbol cannot be introduced without documentation.