Web chat interface for any agent

[DouweM]

Description

Now that we have #2923, we can add a clai web command and/or Agent.to_web() method to launch a web chat app for any agent.

The frontend is nearly ready in https://github.com/pydantic/ai-chat-ui. Since it lets the user select a model and toggle builtin tools, we need to add a way to Pydantic AI to easily determine which builtin tools are supported by a given model, and then let you specify on the method/command which models to present as options, as well as which builtin tools.

References

No response

[adtyavrdhn]

I am not sure if it is already done(or in plan) but if we could support multiple agents and toggle between them in the UI that would be great.

[echarles]

Love this, a default feature set for the ui is a great quick-win.

Question:

• Will it be possible to support also both vercel streaming and ag-ui protocol? (prolly out of scope of the first implementation, but worth to consider while designing)
• What about having the ability to bring its own UI (I guess providing a link to a CDN hosted js).

[DouweM]

• Will it be possible to support also both vercel streaming and ag-ui protocol? (prolly out
  of scope of the first implementation, but worth to consider while designing)

@echarles What would be the advantage of having both? For the most part, users should just use the chat app, without needing to care about the implementation detials.

• What about having the ability to bring its own UI (I guess providing a link to a CDN hosted js).

I think that goes beyond the scope of this "instant chat app for your agent" feature -- if you want a custom frontend, you can just write your own little FastAPI app that uses UIAdapter.dispatch_request (https://ai.pydantic.dev/ui/overview/)

[echarles]

@echarles What would be the advantage of having both? For the most part, users should just use the chat app, without needing to care about the implementation detials.

We have a case where a customer is willing to use our backend serivces via their own custom ui. The to_web('ag-ui') case would allow us to develop on our side, make sure it works, and then ship/deploy what we have done the the customer would consume through AG-UI messages.

I think that goes beyond the scope of this "instant chat app for your agent" feature -- if you want a custom frontend, you can just write your own little FastAPI app that uses UIAdapter.dispatch_request (https://ai.pydantic.dev/ui/overview/)

Make sense, was just wondering.

[DouweM]

@echarles Note that you can already use the AG-UI Dojo to test your backend easily: https://ai.pydantic.dev/examples/ag-ui/

[echarles]

Note that you can already use the AG-UI Do

Yep, I have used that. It help but lacks way to run your effective agent, or you have to hack the source code

btw I have opened #3387 to fix the broken link to the ag-ui dojo.

[dsfaccini]

I made a concept for this uvx pydantic-work. I'd need to figure out how to make the agent loading faster but other than that it should work fine. @echarles if you want to give it a try let me know how it goes.

Screen.Recording.2025-11-10.at.12.54.45.mov

Here's the fork ai-chat-ui