🔧 fix: Await MCP Instructions and Filter Malformed Tool Calls (#10485)

* fix: Await MCP instructions formatting in AgentClient

* fix: don't render or aggregate malformed tool calls

* fix: implement filter for malformed tool call content parts and add tests

api/package.json

@@ -47,7 +47,7 @@
     "@langchain/google-genai": "^0.2.13",
     "@langchain/google-vertexai": "^0.2.13",
     "@langchain/textsplitters": "^0.1.0",
-    "@librechat/agents": "^3.0.15",
+    "@librechat/agents": "^3.0.17",
     "@librechat/api": "*",
     "@librechat/data-schemas": "*",
     "@microsoft/microsoft-graph-client": "^3.0.7",

api/server/controllers/agents/client.js

@@ -13,6 +13,7 @@ const {
   memoryInstructions,
   getTransactionsConfig,
   createMemoryProcessor,
+  filterMalformedContentParts,
 } = require('@librechat/api');
 const {
   Callback,
@@ -344,7 +345,7 @@ class AgentClient extends BaseClient {
 
     if (mcpServers.length > 0) {
       try {
-        const mcpInstructions = getMCPManager().formatInstructionsForContext(mcpServers);
+        const mcpInstructions = await getMCPManager().formatInstructionsForContext(mcpServers);
         if (mcpInstructions) {
           systemContent = [systemContent, mcpInstructions].filter(Boolean).join('\n\n');
           logger.debug('[AgentClient] Injected MCP instructions for servers:', mcpServers);
@@ -611,7 +612,7 @@ class AgentClient extends BaseClient {
       userMCPAuthMap: opts.userMCPAuthMap,
       abortController: opts.abortController,
     });
-    return this.contentParts;
+    return filterMalformedContentParts(this.contentParts);
   }
 
   /**

api/server/controllers/agents/client.test.js

@@ -14,6 +14,14 @@ jest.mock('@librechat/api', () => ({
   ...jest.requireActual('@librechat/api'),
 }));
 
+// Mock getMCPManager
+const mockFormatInstructions = jest.fn();
+jest.mock('~/config', () => ({
+  getMCPManager: jest.fn(() => ({
+    formatInstructionsForContext: mockFormatInstructions,
+  })),
+}));
+
 describe('AgentClient - titleConvo', () => {
   let client;
   let mockRun;
@@ -1168,6 +1176,200 @@ describe('AgentClient - titleConvo', () => {
     });
   });
 
+  describe('buildMessages with MCP server instructions', () => {
+    let client;
+    let mockReq;
+    let mockRes;
+    let mockAgent;
+    let mockOptions;
+
+    beforeEach(() => {
+      jest.clearAllMocks();
+
+      // Reset the mock to default behavior
+      mockFormatInstructions.mockResolvedValue(
+        '# MCP Server Instructions\n\nTest MCP instructions here',
+      );
+
+      const { DynamicStructuredTool } = require('@langchain/core/tools');
+
+      // Create mock MCP tools with the delimiter pattern
+      const mockMCPTool1 = new DynamicStructuredTool({
+        name: `tool1${Constants.mcp_delimiter}server1`,
+        description: 'Test MCP tool 1',
+        schema: {},
+        func: async () => 'result',
+      });
+
+      const mockMCPTool2 = new DynamicStructuredTool({
+        name: `tool2${Constants.mcp_delimiter}server2`,
+        description: 'Test MCP tool 2',
+        schema: {},
+        func: async () => 'result',
+      });
+
+      mockAgent = {
+        id: 'agent-123',
+        endpoint: EModelEndpoint.openAI,
+        provider: EModelEndpoint.openAI,
+        instructions: 'Base agent instructions',
+        model_parameters: {
+          model: 'gpt-4',
+        },
+        tools: [mockMCPTool1, mockMCPTool2],
+      };
+
+      mockReq = {
+        user: {
+          id: 'user-123',
+        },
+        body: {
+          endpoint: EModelEndpoint.openAI,
+        },
+        config: {},
+      };
+
+      mockRes = {};
+
+      mockOptions = {
+        req: mockReq,
+        res: mockRes,
+        agent: mockAgent,
+        endpoint: EModelEndpoint.agents,
+      };
+
+      client = new AgentClient(mockOptions);
+      client.conversationId = 'convo-123';
+      client.responseMessageId = 'response-123';
+      client.shouldSummarize = false;
+      client.maxContextTokens = 4096;
+    });
+
+    it('should await MCP instructions and not include [object Promise] in agent instructions', async () => {
+      // Set specific return value for this test
+      mockFormatInstructions.mockResolvedValue(
+        '# MCP Server Instructions\n\nUse these tools carefully',
+      );
+
+      const messages = [
+        {
+          messageId: 'msg-1',
+          parentMessageId: null,
+          sender: 'User',
+          text: 'Hello',
+          isCreatedByUser: true,
+        },
+      ];
+
+      await client.buildMessages(messages, null, {
+        instructions: 'Base instructions',
+        additional_instructions: null,
+      });
+
+      // Verify formatInstructionsForContext was called with correct server names
+      expect(mockFormatInstructions).toHaveBeenCalledWith(['server1', 'server2']);
+
+      // Verify the instructions do NOT contain [object Promise]
+      expect(client.options.agent.instructions).not.toContain('[object Promise]');
+
+      // Verify the instructions DO contain the MCP instructions
+      expect(client.options.agent.instructions).toContain('# MCP Server Instructions');
+      expect(client.options.agent.instructions).toContain('Use these tools carefully');
+
+      // Verify the base instructions are also included
+      expect(client.options.agent.instructions).toContain('Base instructions');
+    });
+
+    it('should handle MCP instructions with ephemeral agent', async () => {
+      // Set specific return value for this test
+      mockFormatInstructions.mockResolvedValue(
+        '# Ephemeral MCP Instructions\n\nSpecial ephemeral instructions',
+      );
+
+      // Set up ephemeral agent with MCP servers
+      mockReq.body.ephemeralAgent = {
+        mcp: ['ephemeral-server1', 'ephemeral-server2'],
+      };
+
+      const messages = [
+        {
+          messageId: 'msg-1',
+          parentMessageId: null,
+          sender: 'User',
+          text: 'Test ephemeral',
+          isCreatedByUser: true,
+        },
+      ];
+
+      await client.buildMessages(messages, null, {
+        instructions: 'Ephemeral instructions',
+        additional_instructions: null,
+      });
+
+      // Verify formatInstructionsForContext was called with ephemeral server names
+      expect(mockFormatInstructions).toHaveBeenCalledWith([
+        'ephemeral-server1',
+        'ephemeral-server2',
+      ]);
+
+      // Verify no [object Promise] in instructions
+      expect(client.options.agent.instructions).not.toContain('[object Promise]');
+
+      // Verify ephemeral MCP instructions are included
+      expect(client.options.agent.instructions).toContain('# Ephemeral MCP Instructions');
+      expect(client.options.agent.instructions).toContain('Special ephemeral instructions');
+    });
+
+    it('should handle empty MCP instructions gracefully', async () => {
+      // Set empty return value for this test
+      mockFormatInstructions.mockResolvedValue('');
+
+      const messages = [
+        {
+          messageId: 'msg-1',
+          parentMessageId: null,
+          sender: 'User',
+          text: 'Hello',
+          isCreatedByUser: true,
+        },
+      ];
+
+      await client.buildMessages(messages, null, {
+        instructions: 'Base instructions only',
+        additional_instructions: null,
+      });
+
+      // Verify the instructions still work without MCP content
+      expect(client.options.agent.instructions).toBe('Base instructions only');
+      expect(client.options.agent.instructions).not.toContain('[object Promise]');
+    });
+
+    it('should handle MCP instructions error gracefully', async () => {
+      // Set error return for this test
+      mockFormatInstructions.mockRejectedValue(new Error('MCP error'));
+
+      const messages = [
+        {
+          messageId: 'msg-1',
+          parentMessageId: null,
+          sender: 'User',
+          text: 'Hello',
+          isCreatedByUser: true,
+        },
+      ];
+
+      // Should not throw
+      await client.buildMessages(messages, null, {
+        instructions: 'Base instructions',
+        additional_instructions: null,
+      });
+
+      // Should still have base instructions without MCP content
+      expect(client.options.agent.instructions).toContain('Base instructions');
+      expect(client.options.agent.instructions).not.toContain('[object Promise]');
+    });
+  });
+
   describe('runMemory method', () => {
     let client;
     let mockReq;

client/src/components/Chat/Messages/Content/Part.tsx

@@ -144,6 +144,7 @@ const Part = memo(
             attachments={attachments}
             auth={toolCall.auth}
             expires_at={toolCall.expires_at}
+            isLast={isLast}
           />
         );
       } else if (toolCall.type === ToolCallTypes.CODE_INTERPRETER) {
@@ -192,6 +193,7 @@ const Part = memo(
             args={toolCall.function.arguments as string}
             name={toolCall.function.name}
             output={toolCall.function.output}
+            isLast={isLast}
           />
         );
       }

client/src/components/Chat/Messages/Content/ToolCall.tsx

@@ -11,6 +11,7 @@ import { logger, cn } from '~/utils';
 
 export default function ToolCall({
   initialProgress = 0.1,
+  isLast = false,
   isSubmitting,
   name,
   args: _args = '',
@@ -19,6 +20,7 @@ export default function ToolCall({
   auth,
 }: {
   initialProgress: number;
+  isLast?: boolean;
   isSubmitting: boolean;
   name: string;
   args: string | Record<string, unknown>;
@@ -155,6 +157,10 @@ export default function ToolCall({
     };
   }, [showInfo, isAnimating]);
 
+  if (!isLast && (!function_name || function_name.length === 0) && !output) {
+    return null;
+  }
+
   return (
     <>
       <div className="relative my-2.5 flex h-5 shrink-0 items-center gap-2.5">

package-lock.json

@@ -63,7 +63,7 @@
         "@langchain/google-genai": "^0.2.13",
         "@langchain/google-vertexai": "^0.2.13",
         "@langchain/textsplitters": "^0.1.0",
-        "@librechat/agents": "^3.0.15",
+        "@librechat/agents": "^3.0.17",
         "@librechat/api": "*",
         "@librechat/data-schemas": "*",
         "@microsoft/microsoft-graph-client": "^3.0.7",
@@ -16666,9 +16666,9 @@
       }
     },
     "node_modules/@librechat/agents": {
-      "version": "3.0.15",
+      "version": "3.0.17",
-      "resolved": "https://registry.npmjs.org/@librechat/agents/-/agents-3.0.15.tgz",
+      "resolved": "https://registry.npmjs.org/@librechat/agents/-/agents-3.0.17.tgz",
-      "integrity": "sha512-iJyUZnfZrPgCeuhCEMOTJW5rp2z6QBsERwytNAr6haSXKiN4F7A6yfzJUkSTTLAu49+xoMIANAOMi8POaFdZ9Q==",
+      "integrity": "sha512-gnom77oW10cdGmmQ6rExc+Blrfzib9JqrZk2fDPwkSOWXQIK4nMm6vWS+UkhH/YfN996mMnffpWoQQ6QQvkTGg==",
       "license": "MIT",
       "dependencies": {
         "@langchain/anthropic": "^0.3.26",
@@ -46470,7 +46470,7 @@
         "@azure/storage-blob": "^12.27.0",
         "@keyv/redis": "^4.3.3",
         "@langchain/core": "^0.3.79",
-        "@librechat/agents": "^3.0.15",
+        "@librechat/agents": "^3.0.17",
         "@librechat/data-schemas": "*",
         "@modelcontextprotocol/sdk": "^1.21.0",
         "axios": "^1.12.1",

packages/api/package.json

@@ -83,7 +83,7 @@
     "@azure/storage-blob": "^12.27.0",
     "@keyv/redis": "^4.3.3",
     "@langchain/core": "^0.3.79",
-    "@librechat/agents": "^3.0.15",
+    "@librechat/agents": "^3.0.17",
     "@librechat/data-schemas": "*",
     "@modelcontextprotocol/sdk": "^1.21.0",
     "axios": "^1.12.1",

packages/api/src/utils/content.spec.ts

@@ -0,0 +1,200 @@
+import { ContentTypes, ToolCallTypes } from 'librechat-data-provider';
+import type { Agents, PartMetadata, TMessageContentParts } from 'librechat-data-provider';
+import type { ToolCall } from '@langchain/core/messages/tool';
+import { filterMalformedContentParts } from './content';
+
+describe('filterMalformedContentParts', () => {
+  describe('basic filtering', () => {
+    it('should keep valid tool_call content parts', () => {
+      const parts: TMessageContentParts[] = [
+        {
+          type: ContentTypes.TOOL_CALL,
+          tool_call: {
+            id: 'test-id',
+            name: 'test_function',
+            type: ToolCallTypes.TOOL_CALL,
+            args: '{}',
+            progress: 1,
+            output: 'result',
+          },
+        },
+      ];
+
+      const result = filterMalformedContentParts(parts);
+      expect(result).toHaveLength(1);
+      expect(result[0]).toEqual(parts[0]);
+    });
+
+    it('should filter out malformed tool_call content parts without tool_call property', () => {
+      const parts: TMessageContentParts[] = [
+        { type: ContentTypes.TOOL_CALL } as TMessageContentParts,
+      ];
+
+      const result = filterMalformedContentParts(parts);
+      expect(result).toHaveLength(0);
+    });
+
+    it('should keep other content types unchanged', () => {
+      const parts: TMessageContentParts[] = [
+        { type: ContentTypes.TEXT, text: 'Hello world' },
+        { type: ContentTypes.THINK, think: 'Thinking...' },
+      ];
+
+      const result = filterMalformedContentParts(parts);
+      expect(result).toHaveLength(2);
+      expect(result).toEqual(parts);
+    });
+
+    it('should filter out null or undefined parts', () => {
+      const parts = [
+        { type: ContentTypes.TEXT, text: 'Valid' },
+        null,
+        undefined,
+        { type: ContentTypes.TEXT, text: 'Also valid' },
+      ] as TMessageContentParts[];
+
+      const result = filterMalformedContentParts(parts);
+      expect(result).toHaveLength(2);
+      expect(result[0]).toHaveProperty('text', 'Valid');
+      expect(result[1]).toHaveProperty('text', 'Also valid');
+    });
+
+    it('should return non-array input unchanged', () => {
+      const notAnArray = { some: 'object' };
+      const result = filterMalformedContentParts(notAnArray);
+      expect(result).toBe(notAnArray);
+    });
+  });
+
+  describe('real-life example with multiple tool calls', () => {
+    it('should filter out malformed tool_call entries from actual MCP response', () => {
+      const parts: TMessageContentParts[] = [
+        {
+          type: ContentTypes.THINK,
+          think:
+            'The user is asking for 10 different time zones, similar to what would be displayed in a stock trading room floor.',
+        },
+        {
+          type: ContentTypes.TEXT,
+          text: '# Global Market Times\n\nShowing current time in 10 major financial centers:',
+          tool_call_ids: ['tooluse_Yjfib8PoRXCeCcHRH0JqCw'],
+        },
+        {
+          type: ContentTypes.TOOL_CALL,
+          tool_call: {
+            id: 'tooluse_Yjfib8PoRXCeCcHRH0JqCw',
+            name: 'get_current_time_mcp_time',
+            args: '{"timezone":"America/New_York"}',
+            type: ToolCallTypes.TOOL_CALL,
+            progress: 1,
+            output: '{"timezone":"America/New_York","datetime":"2025-11-13T13:43:17-05:00"}',
+          },
+        },
+        { type: ContentTypes.TOOL_CALL } as TMessageContentParts,
+        {
+          type: ContentTypes.TOOL_CALL,
+          tool_call: {
+            id: 'tooluse_CPsGv9kXTrewVkcO7BEYIg',
+            name: 'get_current_time_mcp_time',
+            args: '{"timezone":"Europe/London"}',
+            type: ToolCallTypes.TOOL_CALL,
+            progress: 1,
+            output: '{"timezone":"Europe/London","datetime":"2025-11-13T18:43:19+00:00"}',
+          },
+        },
+        { type: ContentTypes.TOOL_CALL } as TMessageContentParts,
+        {
+          type: ContentTypes.TOOL_CALL,
+          tool_call: {
+            id: 'tooluse_5jihRbd4TDWCGebwmAUlfQ',
+            name: 'get_current_time_mcp_time',
+            args: '{"timezone":"Asia/Tokyo"}',
+            type: ToolCallTypes.TOOL_CALL,
+            progress: 1,
+            output: '{"timezone":"Asia/Tokyo","datetime":"2025-11-14T03:43:21+09:00"}',
+          },
+        },
+        { type: ContentTypes.TOOL_CALL } as TMessageContentParts,
+        { type: ContentTypes.TOOL_CALL } as TMessageContentParts,
+        { type: ContentTypes.TOOL_CALL } as TMessageContentParts,
+        {
+          type: ContentTypes.TEXT,
+          text: '## Major Financial Markets Clock:\n\n| Market | Local Time | Day |',
+        },
+      ];
+
+      const result = filterMalformedContentParts(parts);
+
+      expect(result).toHaveLength(6);
+
+      expect(result[0].type).toBe(ContentTypes.THINK);
+      expect(result[1].type).toBe(ContentTypes.TEXT);
+      expect(result[2].type).toBe(ContentTypes.TOOL_CALL);
+      expect(result[3].type).toBe(ContentTypes.TOOL_CALL);
+      expect(result[4].type).toBe(ContentTypes.TOOL_CALL);
+      expect(result[5].type).toBe(ContentTypes.TEXT);
+
+      const toolCalls = result.filter((part) => part.type === ContentTypes.TOOL_CALL);
+      expect(toolCalls).toHaveLength(3);
+
+      toolCalls.forEach((toolCall) => {
+        if (toolCall.type === ContentTypes.TOOL_CALL) {
+          expect(toolCall.tool_call).toBeDefined();
+          expect(toolCall.tool_call).toHaveProperty('id');
+          expect(toolCall.tool_call).toHaveProperty('name');
+        }
+      });
+    });
+
+    it('should handle empty array', () => {
+      const result = filterMalformedContentParts([]);
+      expect(result).toEqual([]);
+    });
+
+    it('should handle array with only malformed tool calls', () => {
+      const parts = [
+        { type: ContentTypes.TOOL_CALL },
+        { type: ContentTypes.TOOL_CALL },
+        { type: ContentTypes.TOOL_CALL },
+      ] as TMessageContentParts[];
+
+      const result = filterMalformedContentParts(parts);
+      expect(result).toHaveLength(0);
+    });
+  });
+
+  describe('edge cases', () => {
+    it('should filter out tool_call with null tool_call property', () => {
+      const parts = [
+        { type: ContentTypes.TOOL_CALL, tool_call: null as unknown as ToolCall },
+      ] as TMessageContentParts[];
+
+      const result = filterMalformedContentParts(parts);
+      expect(result).toHaveLength(0);
+    });
+
+    it('should filter out tool_call with non-object tool_call property', () => {
+      const parts = [
+        {
+          type: ContentTypes.TOOL_CALL,
+          tool_call: 'not an object' as unknown as ToolCall & PartMetadata,
+        },
+      ] as TMessageContentParts[];
+
+      const result = filterMalformedContentParts(parts);
+      expect(result).toHaveLength(0);
+    });
+
+    it('should keep tool_call with empty object as tool_call', () => {
+      const parts: TMessageContentParts[] = [
+        {
+          type: ContentTypes.TOOL_CALL,
+          tool_call: {} as unknown as Agents.ToolCall & PartMetadata,
+        },
+      ];
+
+      const result = filterMalformedContentParts(parts);
+      expect(result).toHaveLength(1);
+    });
+  });
+});

packages/api/src/utils/content.ts

@@ -0,0 +1,46 @@
+import { ContentTypes } from 'librechat-data-provider';
+import type { TMessageContentParts } from 'librechat-data-provider';
+
+/**
+ * Filters out malformed tool call content parts that don't have the required tool_call property.
+ * This handles edge cases where tool_call content parts may be created with only a type property
+ * but missing the actual tool_call data.
+ *
+ * @param contentParts - Array of content parts to filter
+ * @returns Filtered array with malformed tool calls removed
+ *
+ * @example
+ * // Removes malformed tool_call without the tool_call property
+ * const parts = [
+ *   { type: 'tool_call', tool_call: { id: '123', name: 'test' } }, // valid - kept
+ *   { type: 'tool_call' }, // invalid - filtered out
+ *   { type: 'text', text: 'Hello' }, // valid - kept (other types pass through)
+ * ];
+ * const filtered = filterMalformedContentParts(parts);
+ * // Returns all parts except the malformed tool_call
+ */
+export function filterMalformedContentParts(
+  contentParts: TMessageContentParts[],
+): TMessageContentParts[];
+export function filterMalformedContentParts<T>(contentParts: T): T;
+export function filterMalformedContentParts<T>(
+  contentParts: T | TMessageContentParts[],
+): T | TMessageContentParts[] {
+  if (!Array.isArray(contentParts)) {
+    return contentParts;
+  }
+
+  return contentParts.filter((part) => {
+    if (!part || typeof part !== 'object') {
+      return false;
+    }
+
+    const { type } = part;
+
+    if (type === ContentTypes.TOOL_CALL) {
+      return 'tool_call' in part && part.tool_call != null && typeof part.tool_call === 'object';
+    }
+
+    return true;
+  });
+}

packages/api/src/utils/index.ts

@@ -1,6 +1,7 @@
 export * from './axios';
 export * from './azure';
 export * from './common';
+export * from './content';
 export * from './email';
 export * from './env';
 export * from './events';