server: wrap headers for mcp proxy (#21072)

* server: wrap headers for mcp proxy

* Update tools/server/server-cors-proxy.h

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* fix build

* chore: update webui build output

* chore: update webui build output

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
Co-authored-by: Aleksander Grygier <aleksander.grygier@gmail.com>

tools/server/server-cors-proxy.h

@@ -32,13 +32,22 @@ static server_http_res_ptr proxy_request(const server_http_req & req, std::strin
 
     SRV_INF("proxying %s request to %s://%s:%i%s\n", method.c_str(), parsed_url.scheme.c_str(), parsed_url.host.c_str(), parsed_url.port, parsed_url.path.c_str());
 
+    std::map<std::string, std::string> headers;
+    for (auto [key, value] : req.headers) {
+        auto new_key = key;
+        if (string_starts_with(new_key, "X-Proxy-Header-")) {
+            string_replace_all(new_key, "X-Proxy-Header-", "");
+        }
+        headers[new_key] = value;
+    }
+
     auto proxy = std::make_unique<server_http_proxy>(
             method,
             parsed_url.scheme,
             parsed_url.host,
             parsed_url.port,
             parsed_url.path,
-            req.headers,
+            headers,
             req.body,
             req.should_stop,
             600, // timeout_read (default to 10 minutes)

tools/server/server-http.h

@@ -35,7 +35,7 @@ using server_http_res_ptr = std::unique_ptr<server_http_res>;
 
 struct server_http_req {
     std::map<std::string, std::string> params; // path_params + query_params
-    std::map<std::string, std::string> headers; // reserved for future use
+    std::map<std::string, std::string> headers; // used by MCP proxy
     std::string path;
     std::string query_string; // query parameters string (e.g. "action=save")
     std::string body;

tools/server/webui/src/lib/services/mcp.service.ts

@@ -39,7 +39,13 @@ import type {
 	MCPResourceContent,
 	MCPReadResourceResult
 } from '$lib/types';
-import { buildProxiedUrl, throwIfAborted, isAbortError, createBase64DataUrl } from '$lib/utils';
+import {
+	buildProxiedUrl,
+	buildProxiedHeaders,
+	throwIfAborted,
+	isAbortError,
+	createBase64DataUrl
+} from '$lib/utils';
 
 interface ToolResultContentItem {
 	type: string;
@@ -118,7 +124,7 @@ export class MCPService {
 		const requestInit: RequestInit = {};
 
 		if (config.headers) {
-			requestInit.headers = config.headers;
+			requestInit.headers = buildProxiedHeaders(config.headers);
 		}
 
 		if (config.credentials) {

tools/server/webui/src/lib/utils/cors-proxy.ts

@@ -19,6 +19,21 @@ export function buildProxiedUrl(targetUrl: string): URL {
 	return proxyUrl;
 }
 
+/**
+ * Wrap original headers for proxying through the CORS proxy. This avoids issues with duplicated llama.cpp-specific and target headers when using the CORS proxy.
+ * @param headers - The original headers to be proxied to target
+ * @returns List of "wrapped" headers to be sent to the CORS proxy
+ */
+export function buildProxiedHeaders(headers: Record<string, string>): Record<string, string> {
+	const proxiedHeaders: Record<string, string> = {};
+
+	for (const [key, value] of Object.entries(headers)) {
+		proxiedHeaders[`X-Proxy-Header-${key}`] = value;
+	}
+
+	return proxiedHeaders;
+}
+
 /**
  * Get a proxied URL string for use in fetch requests.
  * @param targetUrl - The original URL to proxy

tools/server/webui/src/lib/utils/index.ts

@@ -38,7 +38,7 @@ export { highlightCode, detectIncompleteCodeBlock, type IncompleteCodeBlock } fr
 export { setConfigValue, getConfigValue, configToParameterRecord } from './config-helpers';
 
 // CORS Proxy
-export { buildProxiedUrl, getProxiedUrlString } from './cors-proxy';
+export { buildProxiedUrl, getProxiedUrlString, buildProxiedHeaders } from './cors-proxy';
 
 // Conversation utilities
 export { createMessageCountMap, getMessageCount } from './conversation-utils';