Extensions: advertised-extensions toggle in Server Settings (Phase 2 of #1633) (#1743)

* Extensions: advertised-extensions toggle in Server Settings (Phase 2 of #1633)

Adds the debugging knob from #1633: users choose which extensions the
Inspector advertises to a server, and a server may register different tools
in response. Builds on Phase 1's registry + advertisedExtensions option (#1738).

Settings + persistence (core):
- InspectorServerSettings.advertisedExtensions + StoredMCPServer field, wired
  through serverList's read/write converters and INSPECTOR_FIELD_KEY_MAP
  (omit-when-empty, byte-stable round-trip).
- validateSettings (remote PUT route): isBooleanRecord guard + carry a
  non-empty map; unknown/malformed rejected.
- App.tsx threads savedSettings.advertisedExtensions into the client options.

UI:
- ServerSettingsForm renders an "Advertised Extensions" group of checkboxes
  driven by ADVERTISABLE_EXTENSIONS; a per-server override wins over the
  registry default. Modal folds a toggle into settings.advertisedExtensions.

Test server + proof:
- composable-test-server extensionGatedTools: a tool registered disabled and
  enabled on `initialized` iff the client declared the mapped extension
  (getClientCapabilities). Legacy stateful leg. Threaded through
  load-config/resolve-config; advertised-extensions-http.json showcase + README.
- Integration test connects legacy with/without the tasks extension advertised
  and asserts the gated tool appears/disappears in tools/list — the acceptance
  criterion, proven end to end, not asserted.

Tests: serverList round-trip (non-empty/absent/empty), ServerSettingsForm
toggle rows, ServerSettingsModal fold, validateSettings accept/reject, and the
integration gating test. npm run ci green (per-file ≥90 gate held).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* Extensions: add #1739 proof screenshots (advertised-extensions toggle)

End-to-end smoke test in the web client against the legacy
advertised-extensions-http.json test server (port 3220): connecting with the
Tasks extension advertised (default) lists echo + get_weather, unchecking the
Advertised Extensions → Tasks toggle and reconnecting lists only echo — the
server's tool registration changing on the client-declared extension.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* Extensions: reconverge advertisedExtensions to no-override on default (review)

Address Phase 2 review observation #1: toggling an extension back to its
registry default now deletes the override key (and drops the whole map to
undefined when it empties), so the on-disk `advertisedExtensions` reconverges
to the byte-stable "no override" state instead of persisting a redundant
`{ key: <default> }`. Matches the omit-when-default policy the other settings
use. Only a value that differs from the default is persisted.

Adds a modal test asserting the reconvergence (re-checking the sole disabling
override drops advertisedExtensions to undefined).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/web/src/App.tsx

@@ -2271,6 +2271,12 @@ function App() {
             savedSettings.protocolEra,
           ),
         }),
+        // Per-server advertised-extension overrides (#1739). Absent/empty falls
+        // back to the registry defaults in the InspectorClient constructor.
+        ...(savedSettings?.advertisedExtensions &&
+          Object.keys(savedSettings.advertisedExtensions).length > 0 && {
+            advertisedExtensions: savedSettings.advertisedExtensions,
+          }),
         // Set on the `/oauth/callback` rebuild so the client's `saveSession`
         // events (and any later persistence) key off the same OAuth authId
         // the pre-redirect page saved under.

clients/web/src/components/groups/ServerSettingsForm/ServerSettingsForm.stories.tsx

@@ -137,6 +137,18 @@ function InteractiveRender(args: ServerSettingsFormProps) {
           settings: { ...args.settings, paginatedLists: value },
         });
       }}
+      onAdvertisedExtensionChange={(key, checked) => {
+        args.onAdvertisedExtensionChange(key, checked);
+        updateArgs({
+          settings: {
+            ...args.settings,
+            advertisedExtensions: {
+              ...args.settings.advertisedExtensions,
+              [key]: checked,
+            },
+          },
+        });
+      }}
       onMaxFetchRequestsChange={(value) => {
         args.onMaxFetchRequestsChange(value);
         updateArgs({
@@ -191,6 +203,7 @@ const meta: Meta<typeof ServerSettingsForm> = {
     onTimeoutChange: fn(),
     onAutoRefreshChange: fn(),
     onPaginatedListsChange: fn(),
+    onAdvertisedExtensionChange: fn(),
     onMaxFetchRequestsChange: fn(),
     onProtocolEraChange: fn(),
     onModernLogLevelChange: fn(),

clients/web/src/components/groups/ServerSettingsForm/ServerSettingsForm.test.tsx

@@ -66,6 +66,7 @@ const baseHandlers = {
   onTimeoutChange: vi.fn(),
   onAutoRefreshChange: vi.fn(),
   onPaginatedListsChange: vi.fn(),
+  onAdvertisedExtensionChange: vi.fn(),
   onMaxFetchRequestsChange: vi.fn(),
   onProtocolEraChange: vi.fn(),
   onModernLogLevelChange: vi.fn(),
@@ -452,6 +453,62 @@ describe("ServerSettingsForm", () => {
     expect(onAutoRefreshChange).toHaveBeenCalledWith(true);
   });
 
+  it("renders the Advertised Extensions section with Tasks checked by default", () => {
+    renderWithMantine(
+      <ServerSettingsForm
+        {...baseHandlers}
+        settings={emptySettings}
+        expandedSections={["options"]}
+      />,
+    );
+    const tasks = screen.getByRole("checkbox", {
+      name: /Tasks \(io\.modelcontextprotocol\/tasks\)/,
+    });
+    // No override present → the registry default (advertised) shows checked.
+    expect(tasks).toBeChecked();
+  });
+
+  it("reflects an advertisedExtensions override that disables Tasks", () => {
+    renderWithMantine(
+      <ServerSettingsForm
+        {...baseHandlers}
+        settings={{
+          ...emptySettings,
+          advertisedExtensions: { "io.modelcontextprotocol/tasks": false },
+        }}
+        expandedSections={["options"]}
+      />,
+    );
+    expect(
+      screen.getByRole("checkbox", {
+        name: /Tasks \(io\.modelcontextprotocol\/tasks\)/,
+      }),
+    ).not.toBeChecked();
+  });
+
+  it("invokes onAdvertisedExtensionChange when a Tasks toggle is clicked", async () => {
+    const user = userEvent.setup();
+    const onAdvertisedExtensionChange = vi.fn();
+    renderWithMantine(
+      <ServerSettingsForm
+        {...baseHandlers}
+        onAdvertisedExtensionChange={onAdvertisedExtensionChange}
+        settings={emptySettings}
+        expandedSections={["options"]}
+      />,
+    );
+    // Default is checked; clicking flips it to unadvertised.
+    await user.click(
+      screen.getByRole("checkbox", {
+        name: /Tasks \(io\.modelcontextprotocol\/tasks\)/,
+      }),
+    );
+    expect(onAdvertisedExtensionChange).toHaveBeenCalledWith(
+      "io.modelcontextprotocol/tasks",
+      false,
+    );
+  });
+
   it("renders the Network Log Size field reflecting maxFetchRequests", () => {
     renderWithMantine(
       <ServerSettingsForm

clients/web/src/components/groups/ServerSettingsForm/ServerSettingsForm.tsx

@@ -26,8 +26,22 @@ import {
   MODERN_LOG_LEVELS,
 } from "@inspector/core/mcp/types.js";
 import { isOAuthCapableServerType } from "@inspector/core/mcp/config.js";
+import { ADVERTISABLE_EXTENSIONS } from "@inspector/core/mcp/extensions.js";
 import type { Root } from "@modelcontextprotocol/client";
 
+/**
+ * Resolve the advertised state of an extension for the form: the per-server
+ * override wins, else the registry default. Mirrors `buildClientExtensions`'s
+ * resolution so the switches show exactly what the client will advertise.
+ */
+function isExtensionAdvertised(
+  settings: InspectorServerSettings,
+  key: string,
+  defaultAdvertised: boolean,
+): boolean {
+  return settings.advertisedExtensions?.[key] ?? defaultAdvertised;
+}
+
 export type ServerSettingsSection =
   | "options"
   | "environment"
@@ -65,6 +79,12 @@ export interface ServerSettingsFormProps {
   ) => void;
   onAutoRefreshChange: (value: boolean) => void;
   onPaginatedListsChange: (value: boolean) => void;
+  /**
+   * Toggle whether the Inspector advertises the extension `key` to this server.
+   * `checked` is the new advertise state; the modal folds it into
+   * `settings.advertisedExtensions`. (#1739)
+   */
+  onAdvertisedExtensionChange: (key: string, checked: boolean) => void;
   onMaxFetchRequestsChange: (value: number) => void;
   onProtocolEraChange: (value: ServerProtocolEra) => void;
   onModernLogLevelChange: (value: ModernLogLevel) => void;
@@ -272,6 +292,7 @@ export function ServerSettingsForm({
   onTimeoutChange,
   onAutoRefreshChange,
   onPaginatedListsChange,
+  onAdvertisedExtensionChange,
   onMaxFetchRequestsChange,
   onProtocolEraChange,
   onModernLogLevelChange,
@@ -380,6 +401,34 @@ export function ServerSettingsForm({
               checked={settings.paginatedLists ?? false}
               onChange={(e) => onPaginatedListsChange(e.currentTarget.checked)}
             />
+            <Stack gap="xs">
+              <Text size="sm" fw={500}>
+                Advertised Extensions
+              </Text>
+              <Text size="xs" c="var(--inspector-text-secondary)">
+                Which extensions the Inspector declares to this server in its
+                client capabilities. A server may register different tools
+                depending on what the client advertises — toggle these to debug
+                that. Takes effect on the next connect.
+              </Text>
+              {ADVERTISABLE_EXTENSIONS.map((ext) => (
+                <Checkbox
+                  key={ext.key}
+                  label={ext.label}
+                  checked={isExtensionAdvertised(
+                    settings,
+                    ext.key,
+                    ext.defaultAdvertised,
+                  )}
+                  onChange={(e) =>
+                    onAdvertisedExtensionChange(
+                      ext.key,
+                      e.currentTarget.checked,
+                    )
+                  }
+                />
+              ))}
+            </Stack>
             <NumberInput
               label="Network Log Size"
               description="Maximum number of HTTP requests kept in the Network log for this server. Older entries rotate out past this limit; a response body that arrives after its entry rotated out is dropped. Use 0 for unlimited (not recommended). Applies immediately to the active connection."

clients/web/src/components/groups/ServerSettingsModal/ServerSettingsModal.test.tsx

@@ -162,6 +162,63 @@ describe("ServerSettingsModal", () => {
     );
   });
 
+  it("folds an advertised-extension toggle into settings.advertisedExtensions (#1739)", async () => {
+    const user = userEvent.setup();
+    const onSettingsChange = vi.fn();
+    renderWithMantine(
+      <ServerSettingsModal
+        opened
+        settings={emptySettings}
+        serverType="streamable-http"
+        isStdio={false}
+        onClose={vi.fn()}
+        onSettingsChange={onSettingsChange}
+      />,
+    );
+    // The Options section is expanded by default; Tasks is checked (registry
+    // default), so clicking it toggles the override off.
+    await user.click(
+      screen.getByRole("checkbox", {
+        name: /Tasks \(io\.modelcontextprotocol\/tasks\)/,
+      }),
+    );
+    expect(onSettingsChange).toHaveBeenCalledWith(
+      expect.objectContaining({
+        advertisedExtensions: { "io.modelcontextprotocol/tasks": false },
+      }),
+    );
+  });
+
+  it("reconverges to no override when an extension toggle returns to its default (#1739)", async () => {
+    const user = userEvent.setup();
+    const onSettingsChange = vi.fn();
+    renderWithMantine(
+      <ServerSettingsModal
+        opened
+        // Start from a disabling override so re-checking Tasks returns it to the
+        // registry default (advertised) and should drop the key entirely.
+        settings={{
+          ...emptySettings,
+          advertisedExtensions: { "io.modelcontextprotocol/tasks": false },
+        }}
+        serverType="streamable-http"
+        isStdio={false}
+        onClose={vi.fn()}
+        onSettingsChange={onSettingsChange}
+      />,
+    );
+    await user.click(
+      screen.getByRole("checkbox", {
+        name: /Tasks \(io\.modelcontextprotocol\/tasks\)/,
+      }),
+    );
+    // The only override returned to its default → the whole map drops to
+    // undefined (no-override), keeping the on-disk round-trip minimal.
+    expect(onSettingsChange).toHaveBeenCalledWith(
+      expect.objectContaining({ advertisedExtensions: undefined }),
+    );
+  });
+
   it("hides the modern log-level control when this server negotiated legacy under 'auto' (#1629)", () => {
     renderWithMantine(
       <ServerSettingsModal

clients/web/src/components/groups/ServerSettingsModal/ServerSettingsModal.tsx

@@ -9,6 +9,7 @@ import type {
   ServerType,
 } from "@inspector/core/mcp/types.js";
 import { isOAuthCapableServerType } from "@inspector/core/mcp/config.js";
+import { ADVERTISABLE_EXTENSIONS } from "@inspector/core/mcp/extensions.js";
 import { ListToggle } from "../../elements/ListToggle/ListToggle";
 import {
   ServerSettingsForm,
@@ -176,6 +177,24 @@ export function ServerSettingsModal({
     onSettingsChange({ ...settings, paginatedLists: value });
   }
 
+  function handleAdvertisedExtensionChange(key: string, checked: boolean) {
+    const next = { ...settings.advertisedExtensions };
+    const ext = ADVERTISABLE_EXTENSIONS.find((e) => e.key === key);
+    // Reconverge to "no override" when the toggle returns to the registry
+    // default, so the on-disk map (and its byte-stable round-trip) stays minimal
+    // — matching the omit-when-default policy used for the other settings. Only
+    // a value that actually differs from the default is persisted.
+    if (ext && checked === ext.defaultAdvertised) {
+      delete next[key];
+    } else {
+      next[key] = checked;
+    }
+    onSettingsChange({
+      ...settings,
+      advertisedExtensions: Object.keys(next).length > 0 ? next : undefined,
+    });
+  }
+
   function handleMaxFetchRequestsChange(value: number) {
     onSettingsChange({ ...settings, maxFetchRequests: value });
   }
@@ -251,6 +270,7 @@ export function ServerSettingsModal({
           onTimeoutChange={handleTimeoutChange}
           onAutoRefreshChange={handleAutoRefreshChange}
           onPaginatedListsChange={handlePaginatedListsChange}
+          onAdvertisedExtensionChange={handleAdvertisedExtensionChange}
           onMaxFetchRequestsChange={handleMaxFetchRequestsChange}
           onProtocolEraChange={handleProtocolEraChange}
           onModernLogLevelChange={handleModernLogLevelChange}

clients/web/src/test/core/mcp/serverList.test.ts

@@ -284,6 +284,63 @@ describe("serverEntriesToMcpConfig", () => {
     expect(round).toEqual(original);
   });
 
+  it("round-trips advertisedExtensions: lifts a non-empty map to settings and back to disk", () => {
+    const original: MCPConfig = {
+      mcpServers: {
+        exttest: {
+          type: "streamable-http",
+          url: "https://x.test/mcp",
+          advertisedExtensions: { "io.modelcontextprotocol/tasks": false },
+        },
+      },
+    };
+    const [entry] = mcpConfigToServerEntries(original);
+    expect(entry?.settings?.advertisedExtensions).toEqual({
+      "io.modelcontextprotocol/tasks": false,
+    });
+    const round = serverEntriesToMcpConfig(mcpConfigToServerEntries(original));
+    expect(round).toEqual(original);
+  });
+
+  it("omits advertisedExtensions from disk when unset, and leaves settings unset", () => {
+    const original: MCPConfig = {
+      mcpServers: {
+        extnone: {
+          type: "streamable-http",
+          url: "https://x.test/mcp",
+          connectionTimeout: 5000,
+        },
+      },
+    };
+    const [entry] = mcpConfigToServerEntries(original);
+    expect(entry?.settings?.advertisedExtensions).toBeUndefined();
+    const round = serverEntriesToMcpConfig(mcpConfigToServerEntries(original));
+    expect("advertisedExtensions" in (round.mcpServers.extnone ?? {})).toBe(
+      false,
+    );
+    expect(round).toEqual(original);
+  });
+
+  it("treats an empty advertisedExtensions map on disk as unset (omitted on write)", () => {
+    const original: MCPConfig = {
+      mcpServers: {
+        extempty: {
+          type: "streamable-http",
+          url: "https://x.test/mcp",
+          advertisedExtensions: {},
+        },
+      },
+    };
+    const [entry] = mcpConfigToServerEntries(original);
+    // An empty map reads back as unset for the form...
+    expect(entry?.settings?.advertisedExtensions).toBeUndefined();
+    // ...and the write side omits it, so the empty map does not round-trip.
+    const round = serverEntriesToMcpConfig(mcpConfigToServerEntries(original));
+    expect("advertisedExtensions" in (round.mcpServers.extempty ?? {})).toBe(
+      false,
+    );
+  });
+
   it("round-trips maxFetchRequests: lifts a non-default value to settings and back to disk", () => {
     const original: MCPConfig = {
       mcpServers: {

clients/web/src/test/integration/mcp/inspectorClient-advertised-extensions.test.ts

@@ -0,0 +1,129 @@
+import { describe, it, expect, afterEach } from "vitest";
+import * as z from "zod/v4";
+import { InspectorClient } from "@inspector/core/mcp/inspectorClient.js";
+import { createTransportNode } from "@inspector/core/mcp/node/transport.js";
+import { TASKS_EXTENSION_KEY } from "@inspector/core/mcp/modernTaskSchemas.js";
+import {
+  createTestServerHttp,
+  type TestServerHttp,
+  createTestServerInfo,
+} from "@modelcontextprotocol/inspector-test-server";
+
+/**
+ * Live coverage of advertised-extension gating (#1739). The Inspector advertises
+ * a per-server `capabilities.extensions` map (Phase 1, #1738), and a server may
+ * register different tools depending on what the client declared. Here a legacy
+ * stateful server gates a tool on the `io.modelcontextprotocol/tasks` extension:
+ * with the extension advertised the tool appears in `tools/list`; with it
+ * disabled via `advertisedExtensions` the same tool is absent. Driven against a
+ * real server over a real transport.
+ *
+ * A FRESH server is started per scenario on purpose: the gate's `oninitialized`
+ * hook only enables the tool, so a server that already saw a tasks-advertising
+ * client would keep it enabled for a later connection.
+ */
+describe("advertised-extension gating (#1739)", () => {
+  const GATED_TOOL = "gated_tool";
+  const ALWAYS_TOOL = "always_tool";
+
+  let client: InspectorClient | null = null;
+  const servers: TestServerHttp[] = [];
+
+  afterEach(async () => {
+    if (client) {
+      try {
+        await client.disconnect();
+      } catch {
+        // ignore
+      }
+      client = null;
+    }
+    while (servers.length) {
+      const s = servers.pop();
+      try {
+        await s?.stop();
+      } catch {
+        // ignore
+      }
+    }
+  });
+
+  async function startGatedServer(): Promise<TestServerHttp> {
+    const started = createTestServerHttp({
+      serverInfo: createTestServerInfo("advertised-ext-test", "1.0.0"),
+      tools: [
+        {
+          name: ALWAYS_TOOL,
+          description: "Always registered",
+          inputSchema: { message: z.string().optional() },
+          handler: async () => ({
+            content: [{ type: "text" as const, text: "always" }],
+          }),
+        },
+        {
+          name: GATED_TOOL,
+          description: "Registered only when the client declares tasks",
+          inputSchema: { message: z.string().optional() },
+          handler: async () => ({
+            content: [{ type: "text" as const, text: "gated" }],
+          }),
+        },
+      ],
+      extensionGatedTools: { [TASKS_EXTENSION_KEY]: GATED_TOOL },
+    });
+    await started.start();
+    servers.push(started);
+    return started;
+  }
+
+  async function connect(
+    url: string,
+    advertisedExtensions?: Record<string, boolean>,
+  ): Promise<InspectorClient> {
+    const connected = new InspectorClient(
+      { type: "streamable-http", url },
+      {
+        environment: { transport: createTransportNode },
+        ...(advertisedExtensions && { advertisedExtensions }),
+      },
+    );
+    await connected.connect();
+    client = connected;
+    return connected;
+  }
+
+  async function toolNames(connected: InspectorClient): Promise<string[]> {
+    const { tools } = await connected.listTools();
+    return tools.map((t) => t.name);
+  }
+
+  it("registers the gated tool when the client advertises the extension (default)", async () => {
+    const started = await startGatedServer();
+    // Default config: the Tasks extension is advertised by the registry default.
+    const connected = await connect(started.url);
+    const names = await toolNames(connected);
+    expect(names).toContain(ALWAYS_TOOL);
+    expect(names).toContain(GATED_TOOL);
+  });
+
+  it("registers the gated tool when the extension is explicitly advertised", async () => {
+    const started = await startGatedServer();
+    const connected = await connect(started.url, {
+      [TASKS_EXTENSION_KEY]: true,
+    });
+    const names = await toolNames(connected);
+    expect(names).toContain(GATED_TOOL);
+  });
+
+  it("omits the gated tool when the extension is not advertised", async () => {
+    const started = await startGatedServer();
+    // Disable the only registry extension → the client sends no extensions,
+    // so the server never enables the gated tool.
+    const connected = await connect(started.url, {
+      [TASKS_EXTENSION_KEY]: false,
+    });
+    const names = await toolNames(connected);
+    expect(names).toContain(ALWAYS_TOOL);
+    expect(names).not.toContain(GATED_TOOL);
+  });
+});

clients/web/src/test/integration/mcp/remote/server-extra-coverage.test.ts

@@ -513,6 +513,27 @@ describe("server.ts supplemental coverage", () => {
       expect((await res.json()).error).toMatch(/modernLogLevel/);
     });
 
+    it("rejects a non-boolean-valued advertisedExtensions (#1739)", async () => {
+      const res = await postSettings({
+        ...base,
+        advertisedExtensions: { "io.modelcontextprotocol/tasks": "yes" },
+      });
+      expect((await res.json()).error).toMatch(/advertisedExtensions/);
+    });
+
+    it("rejects a non-object advertisedExtensions (#1739)", async () => {
+      const res = await postSettings({
+        ...base,
+        advertisedExtensions: ["io.modelcontextprotocol/tasks"],
+      });
+      expect((await res.json()).error).toMatch(/advertisedExtensions/);
+    });
+
+    it("accepts an empty advertisedExtensions map without persisting it (#1739)", async () => {
+      const res = await postSettings({ ...base, advertisedExtensions: {} });
+      expect(res.status).toBe(200);
+    });
+
     it("accepts a fully-populated valid settings payload", async () => {
       const res = await postSettings({
         ...base,
@@ -521,6 +542,7 @@ describe("server.ts supplemental coverage", () => {
         taskTtl: 1000,
         autoRefreshOnListChanged: true,
         paginatedLists: true,
+        advertisedExtensions: { "io.modelcontextprotocol/tasks": false },
         maxFetchRequests: 5,
         protocolEra: "modern",
         modernLogLevel: "off",