Eve Runtime

@assistant-ui/eve integrates assistant-ui with Eve, Vercel's filesystem-first framework for durable agents. It wraps Eve's useEveAgent hook and exposes it as an assistant-ui ExternalStoreRuntime, so Eve owns the session stream while assistant-ui renders messages, reasoning, dynamic tool calls, and approval requests.

When to use it

Pick the Eve runtime when:

• You want your agent implementation to live under agent/ and be served by eve/next.
• You want Eve sessions, continuation tokens, NDJSON streaming, and local development tooling.
• You want assistant-ui to render Eve messages and human-in-the-loop tool approvals without writing a custom runtime adapter.

Architecture

The Next.js app mounts Eve with withEve() and assistant-ui's registry transform with withAui():

import { withAui } from "@assistant-ui/next";
import type { NextConfig } from "next";
import { withEve } from "eve/next";

const nextConfig: NextConfig = {};

export default withEve(withAui(nextConfig));

On the client, useEveAgentRuntime() calls Eve's React hook and converts Eve message parts into assistant-ui thread messages:

"use client";

import { Thread } from "@/components/assistant-ui/elements/thread.aui";
import { useEveAgentRuntime } from "@assistant-ui/eve";
import { AssistantRuntimeProvider } from "@assistant-ui/react";

export default function Home() {
  const runtime = useEveAgentRuntime();

  return (
    <AssistantRuntimeProvider runtime={runtime}>
      <Thread />
    </AssistantRuntimeProvider>
  );
}

The custom bag of a per-turn runConfig is forwarded to Eve as clientContext, so runConfig: { custom: { page: "/pricing" } } arrives as clientContext: { page: "/pricing" }. An empty or absent bag is omitted, and every value must be JSON-serializable.

Eve turns that object into a model context message, which is why the assistant-ui custom envelope is unwrapped: the envelope would put a literal custom key in the prompt. It is page or client context rather than run configuration, and it cannot select a model or change how the turn executes. Keep secrets, credentials, and personal data out of it, since the model reads it as message text.

Connector authorization

When Eve pauses for connector authorization, the runtime emits an assistant data part named authorization. Its data includes state, name, and the available display fields such as displayName, description, url, userCode, instructions, and expiresAt. Completed parts may also include outcome and reason. url is present only when the connector supplied an http(s) address; the adapter drops other schemes so a renderer can link to it directly.

The Eve template ships this renderer as components/eve-authorization.tsx and mounts it next to <Thread />. To add it to an existing app, register a data UI for the part and type it with the exported EveAuthorizationData:

import type { EveAuthorizationData } from "@assistant-ui/eve";
import { makeAssistantDataUI } from "@assistant-ui/react";

export const AuthorizationUI = makeAssistantDataUI<EveAuthorizationData>({
  name: "authorization",
  render: ({ data }) => (
    <div>
      {data.state === "required" ? (
        <>
          <p>{data.instructions ?? `Sign in to ${data.displayName ?? data.name}`}</p>
          {data.userCode && <code>{data.userCode}</code>}
          {data.url && <a href={data.url}>Continue to sign in</a>}
        </>
      ) : (
        <p>{data.outcome ?? "Authorization completed"}</p>
      )}
    </div>
  ),
});

Mount <AuthorizationUI /> inside the AssistantRuntimeProvider tree. The standard thread intentionally leaves unmatched data parts unrendered.

Requirements

• Node.js 24 or higher.
• React 18 or 19.
• An Eve app mounted with eve/next.
• A model credential for the model configured in agent/agent.ts.

Eve's default gateway model ids route through the Vercel AI Gateway. Use AI_GATEWAY_API_KEY or Vercel OIDC, or configure a direct provider LanguageModel. For local development, a direct LanguageModel can also run on a ChatGPT Plus or Pro plan without any API key; see ChatGPT Subscription.

Install

npm install @assistant-ui/react @assistant-ui/eve eve

Auth note

Eve's built-in eve channel accepts localhost during development and trusted Vercel OIDC callers. It does not automatically admit browser users in production. Before deploying a public app, add agent/channels/eve.ts and wire the channel to your application auth.

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