feat: stream MCP probe progress

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

ARCHITECTURE.md

@@ -276,6 +276,7 @@ Tooling is deliberately split into two levels:
 - **dynamic runtime tools** reported by the Copilot CLI, with a fallback catalog for startup/offline cases
 - **global definitions** for MCP servers and LSP profiles
 - **MCP tool discovery** — when MCP server configs declare wildcard tools (empty `tools` array), the main process probes each server directly via the MCP protocol `tools/list` method to discover available tools, using the same auth credentials Aryx manages for OAuth-protected servers
+- **incremental probe progress** — MCP probing runs concurrently and publishes per-server progress through the pushed workspace snapshot, using the runtime-only `mcpProbingServerIds` field so the renderer can reflect in-flight discovery without persisting transient UI state
 - **pattern defaults** where tool-call approval is enabled by default, plus which known runtime tools can bypass manual approval
 - **per-session overrides** for both tool enablement and tool auto-approval
 

src/main/AryxAppService.ts

@@ -181,12 +181,14 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
   private readonly gitService = new GitService();
   private readonly configScanner = new ConfigScannerRegistry();
   private readonly customizationScanner = new ProjectCustomizationScanner();
+  private readonly probeMcpServers = probeServers;
   private readonly pendingApprovalHandles = new Map<string, PendingApprovalHandle>();
   private readonly pendingUserInputHandles = new Map<string, PendingUserInputHandle>();
   private workspace?: WorkspaceState;
   private sidecarCapabilities?: SidecarCapabilities;
   private sidecarCapabilitiesPromise?: Promise<SidecarCapabilities>;
   private didScheduleInitialProjectGitRefresh = false;
+  private mcpProbeUpdateQueue = Promise.resolve();
 
   async describeSidecarCapabilities(): Promise<SidecarCapabilities> {
     return this.loadSidecarCapabilities();
@@ -346,7 +348,7 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
     const result = await this.persistAndBroadcast(workspace);
 
     if (resolution === 'accept') {
-      void this.probeDiscoveredMcpServers(workspace.settings.discoveredUserTooling, serverIds).catch((error) => {
+      void this.probeDiscoveredMcpServers(workspace, workspace.settings.discoveredUserTooling, serverIds).catch((error) => {
         console.error('[aryx mcp-probe]', error);
       });
     }
@@ -362,7 +364,7 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
     await this.pruneUnavailableApprovalTools(workspace);
     const result = await this.persistAndBroadcast(workspace);
 
-    void this.probeDiscoveredMcpServersFromState(project.discoveredTooling).catch((error) => {
+    void this.probeDiscoveredMcpServersFromState(workspace, project.discoveredTooling).catch((error) => {
       console.error('[aryx mcp-probe]', error);
     });
 
@@ -409,7 +411,7 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
     const result = await this.persistAndBroadcast(workspace);
 
     if (resolution === 'accept') {
-      void this.probeDiscoveredMcpServers(project.discoveredTooling, serverIds).catch((error) => {
+      void this.probeDiscoveredMcpServers(workspace, project.discoveredTooling, serverIds).catch((error) => {
         console.error('[aryx mcp-probe]', error);
       });
     }
@@ -2138,86 +2140,73 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
   }
 
   private async probeAllAcceptedMcpServers(workspace: WorkspaceState): Promise<void> {
-    // Probe discovered MCP servers (from config files)
-    await this.probeDiscoveredMcpServersFromState(workspace.settings.discoveredUserTooling);
-    for (const project of workspace.projects) {
-      await this.probeDiscoveredMcpServersFromState(project.discoveredTooling);
-    }
+    const targets = [
+      ...this.listAcceptedDiscoveredServerDefinitions(
+        workspace,
+        (server) => !server.probedTools || server.probedTools.length === 0,
+      ),
+      ...workspace.settings.tooling.mcpServers.filter(
+        (server) => server.tools.length === 0 && (!server.probedTools || server.probedTools.length === 0),
+      ),
+    ];
 
-    // Probe manually configured MCP servers that have empty tools arrays
-    await this.probeManualMcpServers(workspace);
+    await this.probeWorkspaceMcpServers(workspace, targets);
   }
 
   private async probeDiscoveredMcpServersFromState(
+    workspace: WorkspaceState,
     state?: DiscoveredToolingState,
   ): Promise<void> {
-    const accepted = listAcceptedDiscoveredMcpServers(state);
-    const serversNeedingProbe = accepted.filter(
-      (server) => !server.probedTools || server.probedTools.length === 0,
-    );
-    if (serversNeedingProbe.length === 0) return;
-
-    await this.probeAndApplyResults(state, serversNeedingProbe);
+    const targets = listAcceptedDiscoveredMcpServers(state)
+      .filter((server) => !server.probedTools || server.probedTools.length === 0)
+      .map((server) => this.discoveredServerToDefinition(server));
+    await this.probeWorkspaceMcpServers(workspace, targets);
   }
 
   private async probeDiscoveredMcpServers(
+    workspace: WorkspaceState,
     state: DiscoveredToolingState | undefined,
     serverIds: ReadonlyArray<string>,
   ): Promise<void> {
-    const accepted = listAcceptedDiscoveredMcpServers(state);
-    const targets = accepted.filter((server) => serverIds.includes(server.id));
-    if (targets.length === 0) return;
-
-    await this.probeAndApplyResults(state, targets);
+    const targets = listAcceptedDiscoveredMcpServers(state)
+      .filter((server) => serverIds.includes(server.id))
+      .map((server) => this.discoveredServerToDefinition(server));
+    await this.probeWorkspaceMcpServers(workspace, targets);
   }
 
-  private async probeAndApplyResults(
-    state: DiscoveredToolingState | undefined,
-    targets: ReadonlyArray<DiscoveredMcpServer>,
+  private async probeWorkspaceMcpServers(
+    workspace: WorkspaceState,
+    targets: ReadonlyArray<McpServerDefinition>,
   ): Promise<void> {
+    const uniqueTargets = [...new Map(targets.map((server) => [server.id, server])).values()];
+    if (uniqueTargets.length === 0) {
+      return;
+    }
+
+    const targetIds = uniqueTargets.map((server) => server.id);
     const tokenLookup = (url: string) => getStoredToken(url)?.accessToken;
-    const serverDefs = targets.map((server) => this.discoveredServerToDefinition(server));
-    const results = await probeServers(serverDefs, tokenLookup);
-
-    const resultsById = new Map<string, McpProbeResult>(
-      results.map((r) => [r.serverId, r]),
-    );
-
-    let changed = false;
-    for (const server of state?.mcpServers ?? []) {
-      const result = resultsById.get(server.id);
-      if (result?.status === 'success' && result.tools.length > 0) {
-        server.probedTools = result.tools;
-        changed = true;
+    await this.enqueueMcpProbeUpdate(async () => {
+      if (this.addMcpProbingServerIds(workspace, targetIds)) {
+        await this.persistAndBroadcast(workspace);
       }
-    }
+    });
 
-    if (changed && this.workspace) {
-      await this.persistAndBroadcast(this.workspace);
-    }
-  }
-
-  private async probeManualMcpServers(workspace: WorkspaceState): Promise<void> {
-    const manualServers = workspace.settings.tooling.mcpServers.filter(
-      (server) => server.tools.length === 0 && (!server.probedTools || server.probedTools.length === 0),
-    );
-    if (manualServers.length === 0) return;
-
-    const tokenLookup = (url: string) => getStoredToken(url)?.accessToken;
-    const results = await probeServers(manualServers, tokenLookup);
-
-    let changed = false;
-    for (const result of results) {
-      if (result.status !== 'success' || result.tools.length === 0) continue;
-      const server = workspace.settings.tooling.mcpServers.find((s) => s.id === result.serverId);
-      if (server) {
-        server.probedTools = result.tools;
-        changed = true;
-      }
-    }
-
-    if (changed) {
-      await this.persistAndBroadcast(workspace);
+    try {
+      await this.probeMcpServers(uniqueTargets, tokenLookup, (result) =>
+        this.enqueueMcpProbeUpdate(async () => {
+          const didUpdateProbing = this.removeMcpProbingServerIds(workspace, [result.serverId]);
+          const didApplyResult = this.applyMcpProbeResult(workspace, result);
+          if (didUpdateProbing || didApplyResult) {
+            await this.persistAndBroadcast(workspace);
+          }
+        }),
+      );
+    } finally {
+      await this.enqueueMcpProbeUpdate(async () => {
+        if (this.removeMcpProbingServerIds(workspace, targetIds)) {
+          await this.persistAndBroadcast(workspace);
+        }
+      });
     }
   }
 
@@ -2227,7 +2216,6 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
    */
   private async reprobeServerByUrl(serverUrl: string): Promise<void> {
     const workspace = await this.loadWorkspace();
-    const tokenLookup = (url: string) => getStoredToken(url)?.accessToken;
 
     // Collect matching servers from manual config and discovered tooling
     const targets: McpServerDefinition[] = [];
@@ -2248,36 +2236,103 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
       }
     }
 
-    if (targets.length === 0) return;
+    await this.probeWorkspaceMcpServers(workspace, targets);
+  }
 
-    const results = await probeServers(targets, tokenLookup);
-    const resultsById = new Map(results.map((r) => [r.serverId, r]));
+  private listAcceptedDiscoveredServerDefinitions(
+    workspace: WorkspaceState,
+    predicate?: (server: DiscoveredMcpServer) => boolean,
+  ): McpServerDefinition[] {
+    const definitions: McpServerDefinition[] = [];
+
+    for (const state of this.listDiscoveredToolingStates(workspace)) {
+      for (const server of listAcceptedDiscoveredMcpServers(state)) {
+        if (predicate && !predicate(server)) {
+          continue;
+        }
+        definitions.push(this.discoveredServerToDefinition(server));
+      }
+    }
+
+    return definitions;
+  }
+
+  private listDiscoveredToolingStates(workspace: WorkspaceState): Array<DiscoveredToolingState | undefined> {
+    return [
+      workspace.settings.discoveredUserTooling,
+      ...workspace.projects.map((project) => project.discoveredTooling),
+    ];
+  }
+
+  private addMcpProbingServerIds(workspace: WorkspaceState, serverIds: ReadonlyArray<string>): boolean {
+    return this.updateMcpProbingServerIds(workspace, serverIds, 'add');
+  }
+
+  private removeMcpProbingServerIds(workspace: WorkspaceState, serverIds: ReadonlyArray<string>): boolean {
+    return this.updateMcpProbingServerIds(workspace, serverIds, 'remove');
+  }
+
+  private updateMcpProbingServerIds(
+    workspace: WorkspaceState,
+    serverIds: ReadonlyArray<string>,
+    operation: 'add' | 'remove',
+  ): boolean {
+    const next = new Set(workspace.mcpProbingServerIds ?? []);
+    const before = next.size;
+
+    for (const serverId of serverIds) {
+      if (operation === 'add') {
+        next.add(serverId);
+      } else {
+        next.delete(serverId);
+      }
+    }
+
+    if (next.size === before) {
+      return false;
+    }
+
+    if (next.size === 0) {
+      delete workspace.mcpProbingServerIds;
+    } else {
+      workspace.mcpProbingServerIds = [...next];
+    }
+
+    return true;
+  }
+
+  private applyMcpProbeResult(workspace: WorkspaceState, result: McpProbeResult): boolean {
+    if (result.status !== 'success' || result.tools.length === 0) {
+      return false;
+    }
 
     let changed = false;
 
-    // Apply to manual servers
     for (const server of workspace.settings.tooling.mcpServers) {
-      const result = resultsById.get(server.id);
-      if (result?.status === 'success' && result.tools.length > 0) {
+      if (server.id !== result.serverId) {
+        continue;
+      }
+      server.probedTools = result.tools;
+      changed = true;
+    }
+
+    for (const state of this.listDiscoveredToolingStates(workspace)) {
+      for (const server of state?.mcpServers ?? []) {
+        if (server.id !== result.serverId) {
+          continue;
+        }
         server.probedTools = result.tools;
         changed = true;
       }
     }
 
-    // Apply to discovered servers
-    for (const state of [workspace.settings.discoveredUserTooling, ...workspace.projects.map((p) => p.discoveredTooling)]) {
-      for (const server of state?.mcpServers ?? []) {
-        const result = resultsById.get(server.id);
-        if (result?.status === 'success' && result.tools.length > 0) {
-          server.probedTools = result.tools;
-          changed = true;
-        }
-      }
-    }
+    return changed;
+  }
 
-    if (changed) {
-      await this.persistAndBroadcast(workspace);
-    }
+  private async enqueueMcpProbeUpdate(update: () => Promise<void>): Promise<void> {
+    const next = this.mcpProbeUpdateQueue.then(update, update);
+    this.mcpProbeUpdateQueue = next.catch(() => undefined);
+    await next;
   }
 
   private discoveredServerToDefinition(server: DiscoveredMcpServer): McpServerDefinition {

src/main/persistence/workspaceRepository.ts

@@ -123,8 +123,9 @@ export class WorkspaceRepository {
   }
 
   async save(workspace: WorkspaceState): Promise<void> {
+    const { mcpProbingServerIds: _mcpProbingServerIds, ...persistedWorkspace } = workspace;
     await writeJsonFile(this.filePath, {
-      ...workspace,
+      ...persistedWorkspace,
       lastUpdatedAt: nowIso(),
     });
   }

src/main/services/mcpToolProber.ts

@@ -25,30 +25,32 @@ const MAX_CONCURRENCY = 5;
 export async function probeServers(
   servers: ReadonlyArray<McpServerDefinition>,
   tokenLookup?: (serverUrl: string) => string | undefined,
+  onResult?: (result: McpProbeResult) => void | Promise<void>,
 ): Promise<McpProbeResult[]> {
-  const pending = [...servers];
-  const results: McpProbeResult[] = [];
-  const active: Promise<void>[] = [];
+  if (servers.length === 0) {
+    return [];
+  }
 
-  for (const server of pending) {
-    const task = probeServer(server, tokenLookup).then((result) => {
-      results.push(result);
-    });
-    active.push(task);
+  const results = new Array<McpProbeResult>(servers.length);
+  let nextIndex = 0;
+  const workerCount = Math.min(MAX_CONCURRENCY, servers.length);
 
-    if (active.length >= MAX_CONCURRENCY) {
-      await Promise.race(active);
-      // Remove settled promises
-      for (let i = active.length - 1; i >= 0; i--) {
-        const status = await Promise.race([active[i].then(() => 'done'), Promise.resolve('pending')]);
-        if (status === 'done') {
-          active.splice(i, 1);
-        }
+  async function worker(): Promise<void> {
+    while (true) {
+      const index = nextIndex;
+      nextIndex += 1;
+      const server = servers[index];
+      if (!server) {
+        return;
       }
+
+      const result = await probeServer(server, tokenLookup);
+      results[index] = result;
+      await onResult?.(result);
     }
   }
 
-  await Promise.allSettled(active);
+  await Promise.all(Array.from({ length: workerCount }, () => worker()));
   return results;
 }
 

src/shared/domain/workspace.ts

@@ -10,6 +10,8 @@ export interface WorkspaceState {
   patterns: PatternDefinition[];
   sessions: SessionRecord[];
   settings: WorkspaceSettings;
+  /** Runtime-only MCP probe progress for live UI updates. */
+  mcpProbingServerIds?: string[];
   selectedProjectId?: string;
   selectedPatternId?: string;
   selectedSessionId?: string;

tests/main/appServiceMcpProbing.test.ts

@@ -0,0 +1,278 @@
+import { beforeEach, describe, expect, mock, test } from 'bun:test';
+
+import type { ProjectRecord } from '@shared/domain/project';
+import { createWorkspaceSeed, type WorkspaceState } from '@shared/domain/workspace';
+
+const TIMESTAMP = '2026-03-28T00:00:00.000Z';
+
+type MockProbeResult = {
+  serverId: string;
+  serverName: string;
+  tools: Array<{ name: string; description?: string }>;
+  status: 'success' | 'failed';
+  error?: string;
+};
+
+const probeCalls: string[][] = [];
+let probeResults: MockProbeResult[] = [];
+
+mock.module('electron', () => {
+  const electronMock = {
+    app: {
+      isPackaged: false,
+      getAppPath: () => 'C:\\workspace\\personal\\repositories\\aryx',
+      getPath: () => 'C:\\workspace\\personal\\repositories\\aryx\\tests\\fixtures',
+    },
+    dialog: {
+      showOpenDialog: async () => ({ canceled: true, filePaths: [] }),
+    },
+    shell: {
+      openPath: async () => '',
+    },
+  };
+
+  return {
+    ...electronMock,
+    default: electronMock,
+  };
+});
+
+mock.module('keytar', () => ({
+  default: {
+    getPassword: async () => null,
+    setPassword: async () => undefined,
+    deletePassword: async () => false,
+  },
+}));
+
+const { AryxAppService } = await import('@main/AryxAppService');
+
+beforeEach(() => {
+  probeCalls.length = 0;
+  probeResults = [];
+});
+
+function createProject(overrides?: Partial<ProjectRecord>): ProjectRecord {
+  return {
+    id: 'project-alpha',
+    name: 'alpha',
+    path: 'C:\\workspace\\alpha',
+    addedAt: TIMESTAMP,
+    ...overrides,
+  };
+}
+
+function cloneWorkspaceState(workspace: WorkspaceState): WorkspaceState {
+  return JSON.parse(JSON.stringify(workspace)) as WorkspaceState;
+}
+
+function createService(workspace: WorkspaceState): {
+  service: InstanceType<typeof AryxAppService>;
+  snapshots: WorkspaceState[];
+} {
+  const service = new AryxAppService();
+  const internals = service as unknown as Record<string, unknown>;
+  const snapshots: WorkspaceState[] = [];
+
+  internals.loadWorkspace = async () => workspace;
+  internals.persistAndBroadcast = async (nextWorkspace: WorkspaceState) => {
+    snapshots.push(cloneWorkspaceState(nextWorkspace));
+    return nextWorkspace;
+  };
+  internals.probeMcpServers = async (
+    servers: Array<{ id: string }>,
+    _tokenLookup?: (serverUrl: string) => string | undefined,
+    onResult?: (result: MockProbeResult) => void | Promise<void>,
+  ) => {
+    probeCalls.push(servers.map((server) => server.id));
+    for (const result of probeResults) {
+      await onResult?.(result);
+    }
+    return probeResults;
+  };
+
+  return { service, snapshots };
+}
+
+describe('AryxAppService MCP probing', () => {
+  test('probes accepted discovered and manual MCP servers in one batch with incremental workspace updates', async () => {
+    const workspace = createWorkspaceSeed();
+    const project = createProject({
+      discoveredTooling: {
+        mcpServers: [
+          {
+            id: 'project-server',
+            name: 'Project MCP',
+            transport: 'local',
+            command: 'project-mcp',
+            args: [],
+            tools: [],
+            scope: 'project',
+            scannerId: 'vscode-mcp',
+            sourcePath: 'C:\\workspace\\alpha\\.vscode\\mcp.json',
+            sourceLabel: '.vscode\\mcp.json',
+            fingerprint: 'project-fingerprint',
+            status: 'accepted',
+          },
+        ],
+        lastScannedAt: TIMESTAMP,
+      },
+    });
+
+    workspace.projects = [project];
+    workspace.settings.discoveredUserTooling = {
+      mcpServers: [
+        {
+          id: 'user-server',
+          name: 'User MCP',
+          transport: 'local',
+          command: 'user-mcp',
+          args: [],
+          tools: [],
+          scope: 'user',
+          scannerId: 'copilot-user-mcp',
+          sourcePath: 'C:\\Users\\tester\\.copilot\\mcp.json',
+          sourceLabel: '~\\.copilot\\mcp.json',
+          fingerprint: 'user-fingerprint',
+          status: 'accepted',
+        },
+      ],
+      lastScannedAt: TIMESTAMP,
+    };
+    workspace.settings.tooling.mcpServers = [
+      {
+        id: 'manual-server',
+        name: 'Manual MCP',
+        transport: 'local',
+        command: 'manual-mcp',
+        args: [],
+        tools: [],
+        createdAt: TIMESTAMP,
+        updatedAt: TIMESTAMP,
+      },
+    ];
+
+    probeResults = [
+      {
+        serverId: 'project-server',
+        serverName: 'Project MCP',
+        status: 'success',
+        tools: [{ name: 'project.status' }],
+      },
+      {
+        serverId: 'manual-server',
+        serverName: 'Manual MCP',
+        status: 'success',
+        tools: [{ name: 'manual.status' }],
+      },
+      {
+        serverId: 'user-server',
+        serverName: 'User MCP',
+        status: 'failed',
+        tools: [],
+        error: 'boom',
+      },
+    ];
+
+    const { service, snapshots } = createService(workspace);
+
+    await (
+      service as unknown as {
+        probeAllAcceptedMcpServers: (nextWorkspace: WorkspaceState) => Promise<void>;
+      }
+    ).probeAllAcceptedMcpServers(workspace);
+
+    expect(probeCalls).toEqual([[
+      'user-server',
+      'project-server',
+      'manual-server',
+    ]]);
+    expect(snapshots.map((snapshot) => snapshot.mcpProbingServerIds)).toEqual([
+      ['user-server', 'project-server', 'manual-server'],
+      ['user-server', 'manual-server'],
+      ['user-server'],
+      undefined,
+    ]);
+    expect(workspace.projects[0]?.discoveredTooling?.mcpServers[0]?.probedTools).toEqual([
+      { name: 'project.status' },
+    ]);
+    expect(workspace.settings.tooling.mcpServers[0]?.probedTools).toEqual([
+      { name: 'manual.status' },
+    ]);
+    expect(workspace.settings.discoveredUserTooling.mcpServers[0]?.probedTools).toBeUndefined();
+  });
+
+  test('tracks probing progress while re-probing matching remote MCP servers after OAuth', async () => {
+    const workspace = createWorkspaceSeed();
+    workspace.settings.discoveredUserTooling = {
+      mcpServers: [
+        {
+          id: 'discovered-remote',
+          name: 'Discovered Remote',
+          transport: 'http',
+          url: 'https://example.com/mcp',
+          headers: { 'X-Test': '1' },
+          tools: [],
+          scope: 'user',
+          scannerId: 'copilot-user-mcp',
+          sourcePath: 'C:\\Users\\tester\\.copilot\\mcp.json',
+          sourceLabel: '~\\.copilot\\mcp.json',
+          fingerprint: 'remote-fingerprint',
+          status: 'accepted',
+        },
+      ],
+      lastScannedAt: TIMESTAMP,
+    };
+    workspace.settings.tooling.mcpServers = [
+      {
+        id: 'manual-remote',
+        name: 'Manual Remote',
+        transport: 'http',
+        url: 'https://example.com/mcp',
+        headers: { Authorization: 'Bearer token' },
+        tools: [],
+        createdAt: TIMESTAMP,
+        updatedAt: TIMESTAMP,
+      },
+    ];
+
+    probeResults = [
+      {
+        serverId: 'manual-remote',
+        serverName: 'Manual Remote',
+        status: 'success',
+        tools: [{ name: 'manual.remote' }],
+      },
+      {
+        serverId: 'discovered-remote',
+        serverName: 'Discovered Remote',
+        status: 'success',
+        tools: [{ name: 'discovered.remote' }],
+      },
+    ];
+
+    const { service, snapshots } = createService(workspace);
+
+    await (
+      service as unknown as {
+        reprobeServerByUrl: (serverUrl: string) => Promise<void>;
+      }
+    ).reprobeServerByUrl('https://example.com/mcp');
+
+    expect(probeCalls).toEqual([[
+      'manual-remote',
+      'discovered-remote',
+    ]]);
+    expect(snapshots.map((snapshot) => snapshot.mcpProbingServerIds)).toEqual([
+      ['manual-remote', 'discovered-remote'],
+      ['discovered-remote'],
+      undefined,
+    ]);
+    expect(workspace.settings.tooling.mcpServers[0]?.probedTools).toEqual([
+      { name: 'manual.remote' },
+    ]);
+    expect(workspace.settings.discoveredUserTooling.mcpServers[0]?.probedTools).toEqual([
+      { name: 'discovered.remote' },
+    ]);
+  });
+});

tests/main/mcpToolProber.test.ts

@@ -0,0 +1,133 @@
+import { beforeEach, describe, expect, mock, test } from 'bun:test';
+
+const commandDelaysMs = new Map<string, number>();
+let activeListTools = 0;
+let maxActiveListTools = 0;
+
+class FakeStdioClientTransport {
+  readonly command: string;
+  readonly args?: string[];
+  readonly env?: Record<string, string>;
+  readonly cwd?: string;
+  readonly stderr?: 'ignore';
+  onmessage?: (message: unknown) => void;
+
+  constructor(options: {
+    command: string;
+    args?: string[];
+    env?: Record<string, string>;
+    cwd?: string;
+    stderr?: 'ignore';
+  }) {
+    this.command = options.command;
+    this.args = options.args;
+    this.env = options.env;
+    this.cwd = options.cwd;
+    this.stderr = options.stderr;
+  }
+
+  async send(_message: unknown): Promise<void> {}
+}
+
+class FakeSSEClientTransport {
+  onmessage?: (message: unknown) => void;
+
+  constructor(_url: URL, _options?: unknown) {}
+
+  async send(_message: unknown): Promise<void> {}
+}
+
+class FakeStreamableHTTPClientTransport {
+  onmessage?: (message: unknown) => void;
+
+  constructor(_url: URL, _options?: unknown) {}
+
+  async send(_message: unknown): Promise<void> {}
+}
+
+class FakeClient {
+  private transport?: FakeStdioClientTransport;
+
+  constructor(_clientInfo: unknown, _options: unknown) {}
+
+  async connect(transport: FakeStdioClientTransport): Promise<void> {
+    this.transport = transport;
+  }
+
+  async listTools(): Promise<{ tools: Array<{ name: string }> }> {
+    const command = this.transport?.command;
+    if (!command) {
+      throw new Error('Expected a command for the fake MCP transport.');
+    }
+
+    activeListTools += 1;
+    maxActiveListTools = Math.max(maxActiveListTools, activeListTools);
+    await new Promise((resolve) => setTimeout(resolve, commandDelaysMs.get(command) ?? 0));
+    activeListTools -= 1;
+
+    return {
+      tools: [{ name: `${command}.tool` }],
+    };
+  }
+
+  async close(): Promise<void> {}
+}
+
+mock.module('@modelcontextprotocol/sdk/client/index.js', () => ({
+  Client: FakeClient,
+}));
+
+mock.module('@modelcontextprotocol/sdk/client/stdio.js', () => ({
+  StdioClientTransport: FakeStdioClientTransport,
+}));
+
+mock.module('@modelcontextprotocol/sdk/client/sse.js', () => ({
+  SSEClientTransport: FakeSSEClientTransport,
+}));
+
+mock.module('@modelcontextprotocol/sdk/client/streamableHttp.js', () => ({
+  StreamableHTTPClientTransport: FakeStreamableHTTPClientTransport,
+}));
+
+const { probeServers } = await import('../../src/main/services/mcpToolProber');
+
+const TIMESTAMP = '2026-03-28T00:00:00.000Z';
+
+beforeEach(() => {
+  commandDelaysMs.clear();
+  activeListTools = 0;
+  maxActiveListTools = 0;
+});
+
+describe('probeServers', () => {
+  test('fires onResult as probes finish while preserving input order and concurrency limit', async () => {
+    const servers = Array.from({ length: 7 }, (_, index) => ({
+      id: `server-${index}`,
+      name: `Server ${index}`,
+      transport: 'local' as const,
+      command: `cmd-${index}`,
+      args: [] as string[],
+      tools: [] as string[],
+      createdAt: TIMESTAMP,
+      updatedAt: TIMESTAMP,
+    }));
+
+    const delays = [70, 60, 50, 40, 30, 20, 10];
+    for (const [index, server] of servers.entries()) {
+      commandDelaysMs.set(server.command, delays[index] ?? 0);
+    }
+
+    const callbackOrder: string[] = [];
+    const results = await probeServers(servers, undefined, (result) => {
+      callbackOrder.push(result.serverId);
+    });
+
+    expect(results.map((result) => result.serverId)).toEqual(servers.map((server) => server.id));
+    expect(results.map((result) => result.tools[0]?.name)).toEqual(
+      servers.map((server) => `${server.command}.tool`),
+    );
+    expect(callbackOrder).not.toEqual(servers.map((server) => server.id));
+    expect([...callbackOrder].sort()).toEqual(servers.map((server) => server.id).sort());
+    expect(maxActiveListTools).toBe(5);
+  });
+});

tests/main/workspaceRepositoryScratchpad.test.ts

@@ -87,4 +87,18 @@ describe('WorkspaceRepository scratchpad migration', () => {
     const persisted = JSON.parse(await readFile(workspaceFilePath, 'utf8')) as WorkspaceState;
     expect(persisted.sessions[0]?.cwd).toBe(expectedSessionPath);
   });
+
+  test('strips runtime MCP probing state before persisting workspace data', async () => {
+    const workspaceFilePath = join(USER_DATA_PATH, 'workspace.json');
+    await mkdir(USER_DATA_PATH, { recursive: true });
+
+    const repository = new WorkspaceRepository();
+    const workspace = createStoredWorkspace();
+    workspace.mcpProbingServerIds = ['server-a', 'server-b'];
+
+    await repository.save(workspace);
+
+    const persisted = JSON.parse(await readFile(workspaceFilePath, 'utf8')) as WorkspaceState;
+    expect('mcpProbingServerIds' in persisted).toBe(false);
+  });
 });