fix(mcp): keep tools/list absolute timeout ceiling hard

A configured per-server timeout above 60s was expanding maxTotalTimeout past
the intended absolute discovery ceiling. Clamp the idle timeout to the ceiling
too so tools/list can never hang the UI beyond it; connect() and callTool()
still honor the full configured/execution timeout.

Author: waleedlatif1

apps/sim/lib/mcp/client.test.ts

@@ -64,6 +64,7 @@ vi.mock('@/lib/core/execution-limits', () => ({
 }))
 
 import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js'
+import { getMaxExecutionTimeout } from '@/lib/core/execution-limits'
 import { McpClient } from './client'
 import type { McpClientOptions, McpServerConfig } from './types'
 
@@ -82,6 +83,9 @@ describe('McpClient notification handler', () => {
     vi.clearAllMocks()
     mockSdkConnect.mockResolvedValue(undefined)
     mockSdkListTools.mockResolvedValue({ tools: [] })
+    // clearAllMocks resets call history but not implementations; re-establish the
+    // default so a per-test override can't bleed into later tests.
+    vi.mocked(getMaxExecutionTimeout).mockReturnValue(30_000)
   })
 
   it('fires onToolsChanged when a notification arrives while connected', async () => {
@@ -174,6 +178,22 @@ describe('McpClient notification handler', () => {
     )
   })
 
+  it('clamps a configured tools/list timeout to the absolute discovery ceiling', async () => {
+    vi.mocked(getMaxExecutionTimeout).mockReturnValue(120_000)
+    const client = new McpClient({
+      config: { ...createConfig(), timeout: 300_000 },
+      securityPolicy: { requireConsent: false, auditLevel: 'basic' },
+    })
+
+    await client.connect()
+    await client.listTools()
+
+    expect(mockSdkListTools).toHaveBeenCalledWith(
+      undefined,
+      expect.objectContaining({ timeout: 60_000, maxTotalTimeout: 60_000 })
+    )
+  })
+
   it('logs connection diagnostics without header values', async () => {
     const client = new McpClient({
       config: {

apps/sim/lib/mcp/client.ts

@@ -226,16 +226,16 @@ export class McpClient {
     }
 
     const configuredTimeout = this.config.timeout
+    // Idle timeout honors the per-server config but never exceeds the absolute
+    // discovery ceiling, so tools/list can't hang the UI past that cap.
     const idleTimeoutMs = Math.min(
       configuredTimeout !== undefined && Number.isFinite(configuredTimeout) && configuredTimeout > 0
         ? Math.floor(configuredTimeout)
         : MCP_CLIENT_CONSTANTS.LIST_TOOLS_TIMEOUT_MS,
-      getMaxExecutionTimeout()
-    )
-    const maxTotalTimeoutMs = Math.max(
-      idleTimeoutMs,
+      getMaxExecutionTimeout(),
       MCP_CLIENT_CONSTANTS.LIST_TOOLS_MAX_TOTAL_TIMEOUT_MS
     )
+    const maxTotalTimeoutMs = MCP_CLIENT_CONSTANTS.LIST_TOOLS_MAX_TOTAL_TIMEOUT_MS
 
     try {
       const result: ListToolsResult = await this.client.listTools(undefined, {