fix(agents): align Builderlab controls and explain hosting limits

NOTICE.md

@@ -88,6 +88,36 @@ cropped the border, padded it to square, resized to 64×64 and quantised it to
 16 colours. The MIT license terms above also apply to this artwork, with the
 Nous Research copyright notice.
 
+## Model-family brand marks
+
+The additional artwork in `src/shared/design-system/icons/HarnessLogos.tsx`
+identifies model families in shared pickers, including Builderlab and Goose.
+All marks remain the property of their respective owners; their inclusion
+identifies supported models and does not imply endorsement.
+
+DeepSeek: [DeepSeek-icon.svg](https://commons.wikimedia.org/wiki/File:DeepSeek-icon.svg),
+file revision June 30, 2025. Copyright © DeepSeek, MIT (Expat) license.
+The MIT terms reproduced above apply with this copyright notice. The original
+blue fill and path geometry are preserved; this app adds its shared SVG wrapper.
+
+Grok: [Grok-feb-2025-logo.svg](https://commons.wikimedia.org/wiki/File:Grok-feb-2025-logo.svg),
+by X.AI Corp., classified by Wikimedia Commons as public domain because it
+consists of simple geometric shapes or text. This app retains the two mark
+paths, omits the wordmark, crops the viewBox to square, and preserves the
+original `currentColor` fill. Grok is a trademark of xAI.
+
+Z.ai / GLM: [Z.ai (company logo).svg](https://commons.wikimedia.org/wiki/File:Z.ai_(company_logo).svg),
+by Z.ai, sourced from its [official favicon](https://z-cdn.chatglm.cn/z-ai/static/logo.svg).
+Wikimedia Commons classifies the artwork as public domain because it consists
+of simple geometric shapes or text. This app preserves the favicon geometry,
+colors and border, removes unused styles and groups, and adds its shared SVG
+wrapper. Z.ai and GLM are marks of their respective owner.
+
+Kimi: the official [Moonshot Kimi favicon](https://www.kimi.com/favicon-light.ico),
+retrieved October 28, 2026, converted from its 48×48 ICO frame to the colocated
+`icons/kimi.png` without resizing or changing colors. No open-source license is
+asserted for this official brand asset. Kimi is a trademark of Moonshot AI.
+
 ## Plugin catalog artwork
 
 The generated plugin PNG artwork in `src/bundled/*/icon.png` was created by

src/bundled/agents/AgentSettingsHost.test.tsx

@@ -0,0 +1,178 @@
+// @vitest-environment jsdom
+import "@testing-library/jest-dom/vitest";
+import { cleanup, render, screen, waitFor } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { afterEach, expect, it, vi } from "vitest";
+import type {
+  Agent,
+  Agents,
+  RegisteredAgentType,
+} from "../../features/agents/service";
+import { RobotIcon } from "../../shared/design-system/icons";
+import { useAgentSettingsHost } from "./AgentSettingsHost";
+
+afterEach(cleanup);
+
+function fixture({ hosted = true, anotherLocal = true, place = "here" } = {}) {
+  const agent = {
+    key: "a".repeat(64),
+    pubkey: "a".repeat(64),
+    name: "Ada",
+    place,
+    type: "local/echo",
+    config: {},
+  } as Agent;
+  const local = {
+    key: agent.type,
+    pluginId: "local",
+    revision: "1",
+    id: "echo",
+    title: "Echo",
+    defaults: () => ({ config: {} }),
+  } satisfies RegisteredAgentType;
+  const remote = {
+    ...local,
+    key: "hosted/builderlab",
+    pluginId: "hosted",
+    id: "builderlab",
+    title: "Builderlab",
+    icon: RobotIcon,
+    remote: {
+      provision: vi.fn(),
+      activate: vi.fn(),
+      profile: vi.fn(),
+      remove: vi.fn(),
+    },
+  } satisfies RegisteredAgentType;
+  const next = { ...local, key: "local/next", id: "next", title: "Next" };
+  const types = [
+    local,
+    ...(hosted ? [remote] : []),
+    ...(anotherLocal ? [next] : []),
+  ];
+  const previewRetype = vi.fn(() => ({
+    config: {},
+    moved: [],
+    dropped: [],
+    settings: [],
+  }));
+  const retype = vi.fn();
+  const agents = { previewRetype, retype } as unknown as Agents;
+  function Host() {
+    const host = useAgentSettingsHost({ agents, agent, type: local, types });
+    return (
+      <>
+        {host.settingsHost.typeControl?.(false)}
+        <output aria-label="Selected harness">{host.agent.type}</output>
+        <output aria-label="Pending change">
+          {String(Boolean(host.settingsHost.pendingSave))}
+        </output>
+      </>
+    );
+  }
+  render(<Host />);
+  return { previewRetype, retype, remote };
+}
+
+it.each([false, true])(
+  "explains hosted choices without staging a migration (another local %s)",
+  async (anotherLocal) => {
+    const user = userEvent.setup();
+    const { previewRetype, retype, remote } = fixture({ anotherLocal });
+    await user.click(
+      screen.getByRole("button", { name: "Change harness from Echo" }),
+    );
+    const hosted = await screen.findByRole("menuitemradio", {
+      name: "Builderlab",
+    });
+    expect(hosted).toHaveAttribute("aria-disabled", "true");
+    expect(hosted).not.toBeChecked();
+    expect(hosted.querySelector("svg")).not.toBeNull();
+    await user.hover(hosted);
+    const help = await screen.findByRole("dialog", {
+      name: "Builderlab hosting",
+    });
+    expect(help).toHaveTextContent(
+      "This agent’s signing key is stored on this device. Buzz can’t move that identity to Builderlab yet. To run hosted, create a new Builderlab agent.",
+    );
+    await user.hover(help);
+    expect(screen.getByRole("menu")).toBeVisible();
+    expect(help).toBeVisible();
+    await user.hover(hosted);
+    await user.click(hosted);
+    expect(screen.getByRole("menu")).toBeVisible();
+    expect(screen.getByLabelText("Selected harness")).toHaveTextContent(
+      "local/echo",
+    );
+    expect(screen.getByLabelText("Pending change")).toHaveTextContent("false");
+    expect(previewRetype).not.toHaveBeenCalled();
+    expect(retype).not.toHaveBeenCalled();
+    expect(remote.remote.provision).not.toHaveBeenCalled();
+    await user.unhover(hosted);
+    await waitFor(() =>
+      expect(
+        screen.queryByRole("dialog", { name: "Builderlab hosting" }),
+      ).toBeNull(),
+    );
+    await user.keyboard("{Home}{ArrowDown}{Enter}");
+    expect(hosted).toHaveFocus();
+    expect(
+      await screen.findByRole("dialog", { name: "Builderlab hosting" }),
+    ).toBeVisible();
+    expect(hosted).toHaveAccessibleDescription(/signing key/);
+    await user.keyboard("{ArrowUp}");
+    expect(screen.getByRole("menuitemradio", { name: "Echo" })).toHaveFocus();
+    await waitFor(() =>
+      expect(
+        screen.queryByRole("dialog", { name: "Builderlab hosting" }),
+      ).toBeNull(),
+    );
+    await user.keyboard("{ArrowDown}{Enter}");
+    expect(
+      await screen.findByRole("dialog", { name: "Builderlab hosting" }),
+    ).toBeVisible();
+    await user.keyboard("{Escape}");
+    await waitFor(() =>
+      expect(
+        screen.queryByRole("dialog", { name: "Builderlab hosting" }),
+      ).toBeNull(),
+    );
+    expect(screen.getByRole("menu")).toBeVisible();
+    await user.keyboard("{Enter}");
+    expect(
+      await screen.findByRole("dialog", { name: "Builderlab hosting" }),
+    ).toBeVisible();
+    expect(previewRetype).not.toHaveBeenCalled();
+    expect(retype).not.toHaveBeenCalled();
+  },
+);
+
+it("keeps the existing local migration flow available", async () => {
+  const user = userEvent.setup();
+  const { previewRetype, retype } = fixture({ hosted: false });
+  await user.click(
+    screen.getByRole("button", { name: "Change harness from Echo" }),
+  );
+  expect(
+    screen.queryByRole("menuitemradio", { name: "Builderlab" }),
+  ).toBeNull();
+  await user.click(await screen.findByRole("menuitemradio", { name: "Next" }));
+  expect(
+    await screen.findByRole("dialog", { name: "Move Ada to Next?" }),
+  ).toBeVisible();
+  expect(previewRetype).toHaveBeenCalledWith("a".repeat(64), "local/next");
+  await user.click(screen.getByRole("button", { name: "Continue" }));
+  expect(screen.getByLabelText("Selected harness")).toHaveTextContent(
+    "local/next",
+  );
+  expect(screen.getByLabelText("Pending change")).toHaveTextContent("true");
+  expect(retype).not.toHaveBeenCalled();
+});
+
+it.each(["hosted", "elsewhere"])(
+  "does not offer local migration for an agent %s",
+  (place) => {
+    fixture({ place });
+    expect(screen.queryByRole("button", { name: /Change harness/ })).toBeNull();
+  },
+);

src/bundled/agents/AgentSettingsHost.tsx

@@ -1,5 +1,5 @@
 import { ProviderDialog } from "./ProviderDialog";
-import { useRef, useState } from "react";
+import { useId, useRef, useState } from "react";
 import type {
   Agent,
   AgentSettingsHost,
@@ -20,6 +20,12 @@ import {
   MenuRoot,
   MenuTrigger,
 } from "../../shared/design-system/ui/Menu";
+import {
+  PopoverRoot,
+  PopoverTrigger,
+  PopoverPopup,
+  PopoverDescription,
+} from "../../shared/design-system/ui/Popover";
 
 const message = (error: unknown) =>
   error instanceof Error ? error.message : String(error);
@@ -82,9 +88,8 @@ export function useAgentSettingsHost({
         setPendingType(undefined);
       }
     : undefined;
-  const canRetype =
-    agent?.place === "here" &&
-    types.some((item) => !item.remote && item.key !== agent.type);
+  const showTypeControl =
+    agent?.place === "here" && types.some((item) => item.key !== agent.type);
   return {
     agent: settingsAgent,
     type: settingsType,
@@ -93,7 +98,7 @@ export function useAgentSettingsHost({
       agents && agent
         ? {
             ...(pendingTypeSave ? { pendingSave: pendingTypeSave } : {}),
-            ...(canRetype
+            ...(showTypeControl
               ? {
                   typeControl: (dirty: boolean) => (
                     <TypeField
@@ -136,8 +141,7 @@ function TypeField({
   selected: string;
   onSelect(type: { key: string; config: unknown } | undefined): void;
 }) {
-  const available =
-    agent.place === "here" ? types.filter((item) => !item.remote) : [];
+  const available = agent.place === "here" ? types : [];
   const others = available.filter((item) => item.key !== agent.type);
   const selectedType = available.find((item) => item.key === selected) ?? type;
   const TypeIcon = selectedType?.icon;
@@ -156,7 +160,7 @@ function TypeField({
       return;
     }
     const target = available.find((item) => item.key === next);
-    if (!target) return;
+    if (!target || target.remote) return;
     setError("");
     try {
       setMigration({
@@ -224,6 +228,10 @@ function TypeField({
                     onValueChange={(next) => choose(String(next))}
                   >
                     {available.map((item) => {
+                      if (item.remote)
+                        return (
+                          <HostedHarnessChoice key={item.key} type={item} />
+                        );
                       const Icon = item.icon;
                       return (
                         <MenuRadioItem
@@ -308,6 +316,81 @@ function TypeField({
   );
 }
 
+function HostedHarnessChoice({ type }: { type: RegisteredAgentType }) {
+  const triggerId = useId();
+  const trigger = useRef<HTMLElement>(null);
+  const description = useId();
+  const [open, setOpen] = useState(false);
+  const Icon = type.icon;
+  return (
+    <PopoverRoot
+      open={open}
+      triggerId={triggerId}
+      onOpenChange={(next, details) => {
+        // The menu returns focus to itself when the pointer enters this card.
+        // Let hover dismissal handle that move; another item still closes it.
+        if (
+          details.reason === "focus-out" &&
+          "relatedTarget" in details.event &&
+          details.event.relatedTarget ===
+            trigger.current?.closest('[role="menu"]')
+        ) {
+          details.cancel();
+          return;
+        }
+        setOpen(next);
+      }}
+    >
+      <PopoverTrigger
+        id={triggerId}
+        openOnHover="preview"
+        nativeButton={false}
+        role="menuitemradio"
+        onFocus={(event) => {
+          if (event.currentTarget.matches(":focus-visible")) setOpen(true);
+        }}
+        onKeyDownCapture={(event) => {
+          if (event.key === "Escape" && open) {
+            event.preventDefault();
+            event.stopPropagation();
+            setOpen(false);
+          } else if (event.key === "Enter" || event.key === " ") {
+            event.preventDefault();
+            setOpen(true);
+          }
+        }}
+        aria-describedby={open ? description : undefined}
+        render={
+          <MenuRadioItem
+            ref={trigger}
+            value={type.key}
+            selection="highlight"
+            disabled
+          >
+            <ChoiceRow
+              label={type.title}
+              leading={Icon ? <Icon size={20} /> : undefined}
+            />
+          </MenuRadioItem>
+        }
+      />
+      <PopoverPopup
+        side="right"
+        align="start"
+        aria-label={`${type.title} hosting`}
+        initialFocus={false}
+        finalFocus={false}
+      >
+        <PopoverDescription id={description}>
+          This agent’s signing key is stored on this device. Buzz can’t move
+          that identity to {type.title} yet. To run hosted, create a new{" "}
+          {type.title} agent.
+        </PopoverDescription>
+      </PopoverPopup>
+    </PopoverRoot>
+  );
+}
+
 export function MigrationPreview({
   source,
   target,