diff --git a/.github/scripts/deepseek-common.mjs b/.github/scripts/deepseek-common.mjs
index 4d073097a..a7d7e7d30 100644
--- a/.github/scripts/deepseek-common.mjs
+++ b/.github/scripts/deepseek-common.mjs
@@ -236,15 +236,50 @@ export function parseJsonObject(text) {
     return JSON.parse(text);
   } catch {}
 
-  const match = text.match(/\{[\s\S]*\}/);
-  if (!match) {
-    return null;
-  }
-  try {
-    return JSON.parse(match[0]);
-  } catch {
-    return null;
+  let candidateStart = -1;
+  let depth = 0;
+  let escaped = false;
+  let inString = false;
+  let lastParsed = null;
+
+  for (let index = 0; index < text.length; index += 1) {
+    const character = text[index];
+
+    if (candidateStart === -1) {
+      if (character === '{') {
+        candidateStart = index;
+        depth = 1;
+      }
+      continue;
+    }
+
+    if (inString) {
+      if (escaped) {
+        escaped = false;
+      } else if (character === '\\') {
+        escaped = true;
+      } else if (character === '"') {
+        inString = false;
+      }
+      continue;
+    }
+
+    if (character === '"') {
+      inString = true;
+    } else if (character === '{') {
+      depth += 1;
+    } else if (character === '}') {
+      depth -= 1;
+      if (depth === 0) {
+        try {
+          lastParsed = JSON.parse(text.slice(candidateStart, index + 1));
+        } catch {}
+        candidateStart = -1;
+      }
+    }
   }
+
+  return lastParsed;
 }
 
 export async function callDeepSeekJson({
@@ -291,14 +326,26 @@ export async function callDeepSeekJson({
   }
 
   const payload = JSON.parse(rawText);
-  const content = payload.choices?.[0]?.message?.content;
-  if (typeof content !== 'string' || !content.trim()) {
-    throw new Error(`DeepSeek API returned no message content: ${truncate(rawText, 1000, 'response')}`);
+  const message = payload.choices?.[0]?.message;
+  const standardContent =
+    typeof message?.content === 'string' && message.content.trim() ? message.content : null;
+  const reasoningContent =
+    typeof message?.reasoning_content === 'string' && message.reasoning_content.trim()
+      ? message.reasoning_content
+      : null;
+  const content = standardContent || reasoningContent;
+
+  if (!content) {
+    throw new Error(
+      `DeepSeek API returned no message or reasoning content: ${truncate(rawText, 1000, 'response')}`
+    );
   }
 
   const parsed = parseJsonObject(content);
   if (!parsed || typeof parsed !== 'object') {
-    throw new Error(`DeepSeek returned non-JSON content: ${truncate(content, 1000, 'model output')}`);
+    throw new Error(
+      `DeepSeek returned non-JSON content: ${truncate(content, 1000, 'model output')}`
+    );
   }
 
   return {
@@ -312,6 +359,7 @@ function isRetryableDeepSeekOutputError(error) {
   const message = String(error?.message || error)
   return (
     message.includes('DeepSeek API returned no message content') ||
+    message.includes('DeepSeek API returned no message or reasoning content') ||
     message.includes('DeepSeek returned non-JSON content') ||
     message.includes('Model returned an empty body.')
   )
diff --git a/tests/deepseek-common.test.ts b/tests/deepseek-common.test.ts
index ad1a7327d..ca271258d 100644
--- a/tests/deepseek-common.test.ts
+++ b/tests/deepseek-common.test.ts
@@ -176,3 +176,83 @@ describe('deepseek-common PR file pagination', () => {
     ]);
   });
 });
+
+describe('deepseek-common structured response parsing', () => {
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  it('uses reasoning_content when DeepSeek returns an empty content field', async () => {
+    const fetchMock = vi.fn().mockResolvedValue(
+      new Response(
+        JSON.stringify({
+          choices: [
+            {
+              message: {
+                content: '',
+                reasoning_content: '{"body":"No findings.\\n\\n*Open Cowork Bot*"}',
+                role: 'assistant',
+              },
+            },
+          ],
+          usage: { completion_tokens: 128 },
+        }),
+        { status: 200 }
+      )
+    );
+    vi.stubGlobal('fetch', fetchMock);
+    const { callDeepSeekJson } = await import('../.github/scripts/deepseek-common.mjs');
+
+    const result = await callDeepSeekJson({
+      apiKey: 'test-key',
+      baseUrl: 'https://api.deepseek.com',
+      effort: 'high',
+      model: 'deepseek-v4-flash',
+      systemPrompt: 'Review the pull request.',
+      userPrompt: 'Return JSON.',
+    });
+
+    expect(result.parsed).toEqual({
+      body: 'No findings.\n\n*Open Cowork Bot*',
+    });
+    expect(result.content).toContain('No findings.');
+  });
+
+  it('extracts the final JSON object from reasoning prose', async () => {
+    const fetchMock = vi.fn().mockResolvedValue(
+      new Response(
+        JSON.stringify({
+          choices: [
+            {
+              message: {
+                content: null,
+                reasoning_content: [
+                  'I should return an object such as {"example":true}.',
+                  'The review is complete.',
+                  '{"body":"Review mode: initial\\n\\nNo findings."}',
+                ].join('\n'),
+                role: 'assistant',
+              },
+            },
+          ],
+        }),
+        { status: 200 }
+      )
+    );
+    vi.stubGlobal('fetch', fetchMock);
+    const { callDeepSeekJson } = await import('../.github/scripts/deepseek-common.mjs');
+
+    const result = await callDeepSeekJson({
+      apiKey: 'test-key',
+      baseUrl: 'https://api.deepseek.com',
+      effort: 'high',
+      model: 'deepseek-v4-flash',
+      systemPrompt: 'Review the pull request.',
+      userPrompt: 'Return JSON.',
+    });
+
+    expect(result.parsed).toEqual({
+      body: 'Review mode: initial\n\nNo findings.',
+    });
+  });
+});