AG-UI

Expose Kern agents via the AG-UI protocol

AG-UI, the Agent-User Interaction Protocol, standardizes how AI agents connect to frontend applications.

Note

Migration from Apps: For migration from AGUIApp, see the v2 migration guide for complete steps.

Example usage

Install backend dependencies

1uv pip install ag-ui-protocol

Run the backend

Expose an Kern agent through the AG-UI interface using AgentOS and AGUI.

1from kern.agent.agent import Agent
2from kern.models.openai import OpenAIResponses
3from kern.os import AgentOS
4from kern.os.interfaces.agui import AGUI
5
6chat_agent = Agent(model=OpenAIResponses(id="gpt-5.5"))
7
8agent_os = AgentOS(agents=[chat_agent], interfaces=[AGUI(agent=chat_agent)])
9app = agent_os.get_app()
10
11if __name__ == "__main__":
12    agent_os.serve(app="basic:app", reload=True)

Run the frontend

Use Dojo (ag-ui's frontend) as an advanced, customizable interface for AG-UI agents.

Clone: git clone https://github.com/ag-ui-protocol/ag-ui.git
Install dependencies in /ag-ui/typescript-sdk: pnpm install
Build the Kern package in /ag-ui/integrations/kern: pnpm run build
Start Dojo following the instructions in the repository.

Chat with the Kern Agent

With Dojo running, open http://localhost:3000 and select the Kern agent.

Additional examples are available in the cookbook.

Custom Events

Custom events created in tools are automatically delivered to AG-UI in the AG-UI custom event format.

Creating custom events:

1from dataclasses import dataclass
2from kern.run.agent import CustomEvent
3
4@dataclass
5class CustomerProfileEvent(CustomEvent):
6    customer_name: str
7    customer_email: str

Yielding from tools:

1from kern.tools import tool
2
3@tool()
4async def get_customer_profile(customer_id: str):
5    customer = fetch_customer(customer_id)
6    
7    yield CustomerProfileEvent(
8        customer_name=customer["name"],
9        customer_email=customer["email"],
10    )
11    
12    return f"Profile retrieved for {customer['name']}"

Custom events are streamed in real-time to the AG-UI frontend.

See Custom Events documentation for more details.

Core Components

AGUI (interface): Wraps an Kern Agent or Team into an AG-UI compatible FastAPI router.
AgentOS.serve: Serves the FastAPI app (including the AGUI router) with Uvicorn.

AGUI mounts protocol-compliant routes on the app.

`AGUI` interface

Main entry point for AG-UI exposure.

Initialization Parameters

Parameter	Type	Default	Description
`agent`	`Optional[Union[Agent, RemoteAgent]]`	`None`	Kern `Agent` or `RemoteAgent` instance.
`team`	`Optional[Union[Team, RemoteTeam]]`	`None`	Kern `Team` or `RemoteTeam` instance.
`prefix`	`str`	`""`	Route prefix (e.g., `/chat`, `/web-research`).
`tags`	`Optional[List[str]]`	`["AGUI"]`	OpenAPI tags for the router.

Provide agent or team.

Key Method

Method	Parameters	Return Type	Description
`get_router`	None	`APIRouter`	Returns the AG-UI FastAPI router and attaches endpoints.

Endpoints

Mounted at the interface's route prefix (root by default):

POST /agui: Main entrypoint. Accepts RunAgentInput from ag-ui-protocol. Streams AG-UI events.
GET /status: Health/status endpoint for the interface.

Refer to ag-ui-protocol docs for payload details.

Serving AgentOS

Use AgentOS.serve to run the app with Uvicorn.

Parameters

Parameter	Type	Default	Description
`app`	`Union[str, FastAPI]`	required	FastAPI app instance or import string.
`host`	`str`	`"localhost"`	Host to bind. Override with `AGENT_OS_HOST` env var.
`port`	`int`	`7777`	Port to bind. Override with `AGENT_OS_PORT` env var.
`reload`	`bool`	`False`	Enable auto-reload for development.
`reload_includes`	`Optional[List[str]]`	`None`	File patterns to watch. Auto-adds `.yaml`, `.yml`.
`reload_excludes`	`Optional[List[str]]`	`None`	File patterns to exclude from reload.
`workers`	`Optional[int]`	`None`	Number of Uvicorn worker processes.
`access_log`	`bool`	`False`	Enable Uvicorn access logging.

See cookbook examples for updated interface patterns.