fix(proxy): keep stream guards active through sse piping

src/proxy/server/messages-route.ts

@@ -221,8 +221,6 @@ export async function handleProxyMessagesRequest(
         resolveOpenAIChatCompletionsUrl(upstream.route.profile.baseUrl),
         buildFetchInit(upstream.route.profile, upstream.body, controller.signal, insecureDispatcher)
       );
-      clearTimeout(timeout);
-      cleanupDisconnectHandlers();
       logger.info('response.received', 'Received upstream response', {
         profileName: profile.profileName,
         routedProfileName: upstream.route.profile.profileName,

src/proxy/transformers/sse-stream-transformer.ts

@@ -3,8 +3,8 @@ import { GlmtTransformer } from '../../glmt/glmt-transformer';
 import { SSEParser } from '../../glmt/sse-parser';
 import type { OpenAIResponse, SSEEvent } from '../../glmt/pipeline';
 
-const JSON_TRANSLATION_ERROR_MESSAGE = 'Failed to translate Cursor JSON response';
+const JSON_TRANSLATION_ERROR_MESSAGE = 'Failed to translate OpenAI-compatible JSON response';
-const STREAM_TRANSLATION_ERROR_MESSAGE = 'Failed to translate Cursor SSE response';
+const STREAM_TRANSLATION_ERROR_MESSAGE = 'Failed to translate OpenAI-compatible SSE response';
 
 type ResponseHeaders = Headers | Record<string, string> | Array<[string, string]>;
 
@@ -103,7 +103,7 @@ async function createAnthropicErrorProxyResponse(response: Response): Promise<Re
         : response.status >= 400 && response.status < 500
           ? 'invalid_request_error'
           : 'api_error';
-  let message = `Cursor request failed with status ${response.status}`;
+  let message = `Upstream request failed with status ${response.status}`;
 
   try {
     const contentType = (response.headers.get('content-type') || '').toLowerCase();
@@ -145,7 +145,7 @@ async function createAnthropicJsonResponse(response: Response): Promise<Response
     const anthropicResponse = new GlmtTransformer().transformResponse(openAIResponse);
     if (isSyntheticTransformationFallback(anthropicResponse)) {
       logTranslationError(
-        'Cursor JSON translation produced synthetic fallback response',
+        'OpenAI-compatible JSON translation produced synthetic fallback response',
         anthropicResponse
       );
       return createAnthropicErrorResponse(502, 'api_error', JSON_TRANSLATION_ERROR_MESSAGE);
@@ -156,7 +156,7 @@ async function createAnthropicJsonResponse(response: Response): Promise<Response
       headers: { 'Content-Type': 'application/json' },
     });
   } catch (error) {
-    logTranslationError('Cursor JSON translation failed', error);
+    logTranslationError('OpenAI-compatible JSON translation failed', error);
     return createAnthropicErrorResponse(502, 'api_error', JSON_TRANSLATION_ERROR_MESSAGE);
   }
 }
@@ -167,7 +167,7 @@ function createAnthropicStreamingResponse(response: Response): Response {
     return createAnthropicErrorResponse(
       502,
       'api_error',
-      'Cursor stream ended before a response body was available'
+      'Upstream stream ended before a response body was available'
     );
   }
 
@@ -209,7 +209,7 @@ function createAnthropicStreamingResponse(response: Response): Response {
           }
         }
       } catch (error) {
-        logTranslationError('Cursor SSE translation failed', error);
+        logTranslationError('OpenAI-compatible SSE translation failed', error);
         controller.enqueue(
           encoder.encode(
             formatSseEvent(

tests/integration/proxy/messages-edge-cases.test.ts

@@ -140,7 +140,7 @@ describe('openai proxy message edge cases', () => {
       type: 'error',
       error: {
         type: 'api_error',
-        message: 'Failed to translate Cursor JSON response',
+        message: 'Failed to translate OpenAI-compatible JSON response',
       },
     });
   });
@@ -202,6 +202,28 @@ describe('openai proxy message edge cases', () => {
     });
   });
 
+  it('emits an SSE error if the upstream stalls after response headers are sent', async () => {
+    process.env.CCS_OPENAI_PROXY_REQUEST_TIMEOUT_MS = '50';
+    await startProxyWithHandler((_req, res) => {
+      res.writeHead(200, { 'Content-Type': 'text/event-stream' });
+      res.write(
+        'data: {"id":"chatcmpl_1","model":"hf-model","choices":[{"index":0,"delta":{"role":"assistant","content":"partial"}}]}\n\n'
+      );
+    });
+
+    const response = await requestProxy({
+      model: 'hf-model',
+      stream: true,
+      messages: [{ role: 'user', content: 'hello' }],
+    });
+
+    expect(response.status).toBe(200);
+    const body = await response.text();
+    expect(body).toContain('event: message_start');
+    expect(body).toContain('event: error');
+    expect(body).toContain('"message":"Failed to translate OpenAI-compatible SSE response"');
+  });
+
   it('aborts the upstream request when the client disconnects mid-flight', async () => {
     await startProxyWithHandler(() => {});
 

tests/unit/cursor/cursor-anthropic-translator.test.ts

@@ -281,7 +281,7 @@ describe('createAnthropicProxyResponse', () => {
     };
     expect(body.type).toBe('error');
     expect(body.error?.type).toBe('api_error');
-    expect(body.error?.message).toBe('Failed to translate Cursor JSON response');
+    expect(body.error?.message).toBe('Failed to translate OpenAI-compatible JSON response');
   });
 
   it('returns 502 when Cursor response is missing choices', async () => {
@@ -305,7 +305,7 @@ describe('createAnthropicProxyResponse', () => {
     };
     expect(body.type).toBe('error');
     expect(body.error?.type).toBe('api_error');
-    expect(body.error?.message).toBe('Failed to translate Cursor JSON response');
+    expect(body.error?.message).toBe('Failed to translate OpenAI-compatible JSON response');
   });
 
   it('returns 502 when Cursor response has empty choices', async () => {
@@ -330,7 +330,7 @@ describe('createAnthropicProxyResponse', () => {
     };
     expect(body.type).toBe('error');
     expect(body.error?.type).toBe('api_error');
-    expect(body.error?.message).toBe('Failed to translate Cursor JSON response');
+    expect(body.error?.message).toBe('Failed to translate OpenAI-compatible JSON response');
   });
 
   it('returns Anthropic error envelopes for non-OK upstream JSON errors', async () => {
@@ -382,7 +382,7 @@ describe('createAnthropicProxyResponse', () => {
     };
     expect(body.type).toBe('error');
     expect(body.error?.type).toBe('api_error');
-    expect(body.error?.message).toBe('Failed to translate Cursor JSON response');
+    expect(body.error?.message).toBe('Failed to translate OpenAI-compatible JSON response');
   });
 
   it('converts OpenAI SSE chunks into Anthropic SSE events', async () => {
@@ -420,7 +420,7 @@ describe('createAnthropicProxyResponse', () => {
     expect(body).toContain('event: error');
     expect(body).toContain('"type":"error"');
     expect(body).toContain('"error":{"type":"api_error"');
-    expect(body).toContain('Failed to translate Cursor SSE response');
+    expect(body).toContain('Failed to translate OpenAI-compatible SSE response');
   });
 
   it('emits Anthropic-style error events when SSE JSON is malformed', async () => {
@@ -435,6 +435,6 @@ describe('createAnthropicProxyResponse', () => {
     expect(body).toContain('event: error');
     expect(body).toContain('"type":"error"');
     expect(body).toContain('"error":{"type":"api_error"');
-    expect(body).toContain('Failed to translate Cursor SSE response');
+    expect(body).toContain('Failed to translate OpenAI-compatible SSE response');
   });
 });