🏷️ feat: Request Placeholders for Custom Endpoint & MCP Headers (#9095)

* feat: Add conversation ID support to custom endpoint headers

- Add LIBRECHAT_CONVERSATION_ID to customUserVars when provided
- Pass conversation ID to header resolution for dynamic headers
- Add comprehensive test coverage

Enables custom endpoints to access conversation context using {{LIBRECHAT_CONVERSATION_ID}} placeholder.

* fix: filter out unresolved placeholders from headers (thanks @MrunmayS)

* feat: add support for request body placeholders in custom endpoint headers

- Add {{LIBRECHAT_BODY_*}} placeholders for conversationId, parentMessageId, messageId
- Update tests to reflect new body placeholder functionality

* refactor resolveHeaders

* style: minor styling cleanup

* fix: type error in unit test

* feat: add body to other endpoints

* feat: add body for mcp tool calls

* chore: remove changes that unnecessarily increase scope after clarification of requirements

* refactor: move http.ts to packages/api and have RequestBody intersect with Express request body

* refactor: processMCPEnv now uses single object argument pattern

* refactor: update processMCPEnv to use 'options' parameter and align types across MCP connection classes

* feat: enhance MCP connection handling with dynamic request headers to pass request body fields

---------

Co-authored-by: Gopal Sharma <gopalsharma@gopal.sharma1>
Co-authored-by: s10gopal <36487439+s10gopal@users.noreply.github.com>
Co-authored-by: Dustin Healy <dustinhealy1@gmail.com>

api/server/services/Endpoints/azureAssistants/initialize.js

@@ -109,14 +109,14 @@ const initializeClient = async ({ req, res, version, endpointOption, initAppClie
 
     apiKey = azureOptions.azureOpenAIApiKey;
     opts.defaultQuery = { 'api-version': azureOptions.azureOpenAIApiVersion };
-    opts.defaultHeaders = resolveHeaders(
-      {
+    opts.defaultHeaders = resolveHeaders({
+      headers: {
         ...headers,
         'api-key': apiKey,
         'OpenAI-Beta': `assistants=${version}`,
       },
-      req.user,
-    );
+      user: req.user,
+    });
     opts.model = azureOptions.azureOpenAIApiDeploymentName;
 
     if (initAppClient) {

api/server/services/Endpoints/custom/initialize.js

@@ -28,7 +28,11 @@ const initializeClient = async ({ req, res, endpointOption, optionsOnly, overrid
   const CUSTOM_API_KEY = extractEnvVariable(endpointConfig.apiKey);
   const CUSTOM_BASE_URL = extractEnvVariable(endpointConfig.baseURL);
 
-  let resolvedHeaders = resolveHeaders(endpointConfig.headers, req.user);
+  let resolvedHeaders = resolveHeaders({
+    headers: endpointConfig.headers,
+    user: req.user,
+    body: req.body,
+  });
 
   if (CUSTOM_API_KEY.match(envVarRegex)) {
     throw new Error(`Missing API Key for ${endpoint}.`);

api/server/services/Endpoints/custom/initialize.spec.js

@@ -64,13 +64,14 @@ describe('custom/initializeClient', () => {
     jest.clearAllMocks();
   });
 
-  it('calls resolveHeaders with headers and user', async () => {
+  it('calls resolveHeaders with headers, user, and body for body placeholder support', async () => {
     const { resolveHeaders } = require('@librechat/api');
     await initializeClient({ req: mockRequest, res: mockResponse, optionsOnly: true });
-    expect(resolveHeaders).toHaveBeenCalledWith(
-      { 'x-user': '{{LIBRECHAT_USER_ID}}', 'x-email': '{{LIBRECHAT_USER_EMAIL}}' },
-      { id: 'user-123', email: 'test@example.com' },
-    );
+    expect(resolveHeaders).toHaveBeenCalledWith({
+      headers: { 'x-user': '{{LIBRECHAT_USER_ID}}', 'x-email': '{{LIBRECHAT_USER_EMAIL}}' },
+      user: { id: 'user-123', email: 'test@example.com' },
+      body: { endpoint: 'test-endpoint' }, // body - supports {{LIBRECHAT_BODY_*}} placeholders
+    });
   });
 
   it('throws if endpoint config is missing', async () => {

api/server/services/Endpoints/openAI/initialize.js

@@ -81,10 +81,10 @@ const initializeClient = async ({
     serverless = _serverless;
 
     clientOptions.reverseProxyUrl = baseURL ?? clientOptions.reverseProxyUrl;
-    clientOptions.headers = resolveHeaders(
-      { ...headers, ...(clientOptions.headers ?? {}) },
-      req.user,
-    );
+    clientOptions.headers = resolveHeaders({
+      headers: { ...headers, ...(clientOptions.headers ?? {}) },
+      user: req.user,
+    });
 
     clientOptions.titleConvo = azureConfig.titleConvo;
     clientOptions.titleModel = azureConfig.titleModel;

api/server/services/MCP.js

@@ -186,6 +186,7 @@ async function createMCPTool({ req, res, toolKey, provider: _provider }) {
           signal: derivedSignal,
         },
         user: config?.configurable?.user,
+        requestBody: config?.configurable?.requestBody,
         customUserVars,
         flowManager,
         tokenMethods: {