fix(proxy): forward reasoning_content sse delta

Author: ymkiux

cli/openai-bridge.js

@@ -794,7 +794,14 @@ function writeChatCompletionChunkAsResponsesSse(state, chunk) {
         const delta = choice && choice.delta && typeof choice.delta === 'object' ? choice.delta : null;
         if (!delta) continue;
 
+        const segments = [];
+        if (typeof delta.reasoning_content === 'string' && delta.reasoning_content) {
+            segments.push(delta.reasoning_content);
+        }
         if (typeof delta.content === 'string' && delta.content) {
+            segments.push(delta.content);
+        }
+        for (const seg of segments) {
             if (!state.messageItem) {
                 state.messageItem = {
                     id: `msg_${crypto.randomBytes(8).toString('hex')}`,
@@ -809,14 +816,14 @@ function writeChatCompletionChunkAsResponsesSse(state, chunk) {
                     item: state.messageItem
                 });
             }
-            state.messageText += delta.content;
+            state.messageText += seg;
             state.messageItem.content[0].text = state.messageText;
             writeSse(state.res, 'response.output_text.delta', {
                 type: 'response.output_text.delta',
                 item_id: state.messageItem.id,
                 output_index: state.output.length - 1,
                 content_index: 0,
-                delta: delta.content,
+                delta: seg,
                 sequence_number: state.nextSeq()
             });
         }

tests/unit/openai-bridge-upstream-responses.test.mjs

@@ -169,6 +169,65 @@ test('openai-bridge streams chat/completions directly when Responses client requ
     await rm(tmpDir, { recursive: true, force: true });
 });
 
+test('openai-bridge forwards upstream reasoning_content as output_text delta', async () => {
+    const upstream = http.createServer((req, res) => {
+        if (req.url === '/v1/chat/completions' && req.method === 'POST') {
+            let body = '';
+            req.on('data', (c) => (body += c));
+            req.on('end', () => {
+                res.writeHead(200, { 'Content-Type': 'text/event-stream; charset=utf-8' });
+                res.write('data: {"id":"r1","model":"deepseek-v4","choices":[{"delta":{"reasoning_content":"thinking-"}}]}\n\n');
+                res.write('data: {"id":"r1","model":"deepseek-v4","choices":[{"delta":{"reasoning_content":"step"}}]}\n\n');
+                res.write('data: {"id":"r1","model":"deepseek-v4","choices":[{"delta":{"content":"answer"}}]}\n\n');
+                res.end('data: [DONE]\n\n');
+            });
+            return;
+        }
+        res.writeHead(404, { 'Content-Type': 'application/json' });
+        res.end(JSON.stringify({ error: 'not found' }));
+    });
+    const { port: upstreamPort } = await listen(upstream);
+
+    const tmpDir = await mkdtemp(path.join(os.tmpdir(), 'codexmate-bridge-test-'));
+    const settingsFile = path.join(tmpDir, 'bridge.json');
+    await writeFile(settingsFile, JSON.stringify({
+        version: 1,
+        providers: {
+            test: { baseUrl: `http://127.0.0.1:${upstreamPort}/v1`, apiKey: 'sk-upstream' }
+        }
+    }), 'utf-8');
+
+    const handler = createOpenaiBridgeHttpHandler({ settingsFile, expectedToken: 'codexmate' });
+    const bridge = http.createServer((req, res) => {
+        if (!handler(req, res)) {
+            res.statusCode = 404;
+            res.end('not handled');
+        }
+    });
+    const { port: bridgePort } = await listen(bridge);
+
+    const base = `http://127.0.0.1:${bridgePort}/bridge/openai/test/v1/responses`;
+    const sse = await requestText(base, {
+        method: 'POST',
+        headers: {
+            'Content-Type': 'application/json',
+            'Accept': 'text/event-stream',
+            'Authorization': 'Bearer codexmate'
+        },
+        body: { model: 'deepseek-v4', input: 'ping', stream: true }
+    });
+    assert.equal(sse.status, 200);
+    assert.match(sse.text, /"delta":"thinking-"/);
+    assert.match(sse.text, /"delta":"step"/);
+    assert.match(sse.text, /"delta":"answer"/);
+    assert.match(sse.text, /"text":"thinking-stepanswer"/);
+    assert.match(sse.text, /data: \[DONE\]/);
+
+    await bridge.close();
+    await upstream.close();
+    await rm(tmpDir, { recursive: true, force: true });
+});
+
 test('openai-bridge reports failed Responses SSE when upstream chat stream ends before DONE', async () => {
     const upstream = http.createServer((req, res) => {
         if (req.url === '/v1/chat/completions' && req.method === 'POST') {