From 898b08854d64befbbb7f6e22a5e3052d65e94f4b Mon Sep 17 00:00:00 2001
From: Xuan-Son Nguyen <son@huggingface.co>
Date: Mon, 6 Jul 2026 08:41:39 +0200
Subject: [PATCH] ui: fake 200 for proxy DELETE req (#25298)

---
 tools/ui/src/lib/services/mcp.service.ts | 24 ++++++++++++++++++++++
 tools/ui/tests/unit/mcp-service.test.ts  | 26 ++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/tools/ui/src/lib/services/mcp.service.ts b/tools/ui/src/lib/services/mcp.service.ts
index 4432989171..ae98632a6f 100644
--- a/tools/ui/src/lib/services/mcp.service.ts
+++ b/tools/ui/src/lib/services/mcp.service.ts
@@ -314,6 +314,30 @@ export class MCPService {
 					)
 				);
 
+				if (method === 'DELETE' && url.includes(CORS_PROXY_ENDPOINT)) {
+					const response = new Response(null, { status: 200, statusText: 'OK' });
+
+					logIfEnabled(
+						this.createLog(
+							MCPConnectionPhase.INITIALIZING,
+							`HTTP 200 ${method} ${url} (fake response)`,
+							MCPLogLevel.INFO,
+							{
+								response: {
+									url,
+									status: response.status,
+									statusText: response.statusText,
+									durationMs: 0,
+									isFake: true
+								}
+							}
+						)
+					);
+
+					// fake response, bypass real fetch()
+					return response;
+				}
+
 				try {
 					const response = await fetch(input, {
 						...baseInit,
diff --git a/tools/ui/tests/unit/mcp-service.test.ts b/tools/ui/tests/unit/mcp-service.test.ts
index 1f6fdda377..d3af906813 100644
--- a/tools/ui/tests/unit/mcp-service.test.ts
+++ b/tools/ui/tests/unit/mcp-service.test.ts
@@ -154,6 +154,32 @@ describe('MCPService', () => {
 		});
 	});
 
+	it('DELETE request with CORS proxy should return a fake 200 response', async () => {
+		const logs: MCPConnectionLog[] = [];
+		const fetchMock = vi.fn();
+
+		vi.stubGlobal('fetch', fetchMock);
+
+		const config: MCPServerConfig = {
+			url: 'https://example.com/mcp',
+			transport: MCPTransportType.STREAMABLE_HTTP,
+			useProxy: true
+		};
+
+		const controller = createDiagnosticFetch(config, (log) => logs.push(log), {}, true);
+
+		const response = await controller.fetch(
+			'http://localhost:8080/cors-proxy?url=https%3A%2F%2Fexample.com%2Fmcp',
+			{ method: 'DELETE' }
+		);
+
+		expect(fetchMock).not.toHaveBeenCalled();
+		expect(response.status).toBe(200);
+		expect(logs.at(-1)?.details).toMatchObject({
+			response: { status: 200, isFake: true }
+		});
+	});
+
 	it('partially redacts mcp-session-id in diagnostic request and response logs', async () => {
 		const logs: MCPConnectionLog[] = [];
 		const response = new Response('{}', {