diff --git a/memento-note/lib/ai/providers/custom-openai.ts b/memento-note/lib/ai/providers/custom-openai.ts
index 63914c9..9f6d550 100644
--- a/memento-note/lib/ai/providers/custom-openai.ts
+++ b/memento-note/lib/ai/providers/custom-openai.ts
@@ -26,6 +26,19 @@ export class CustomOpenAIProvider implements AIProvider {
         const headers = new Headers(options?.headers);
         headers.set('HTTP-Referer', 'https://localhost:3000');
         headers.set('X-Title', 'Memento AI');
+        // Disable DeepSeek extended thinking for reliable tool/function calling
+        if (options?.body) {
+          try {
+            const body = JSON.parse(options.body as string)
+            if (
+              typeof body.model === 'string' &&
+              (body.model.includes('deepseek') || body.model.includes('thinking') || body.model.includes('reasoner'))
+            ) {
+              body.thinking = { type: 'disabled' }
+            }
+            return fetch(url, { ...options, headers, body: JSON.stringify(body) })
+          } catch { /* ignore parse errors */ }
+        }
         return fetch(url, { ...options, headers });
       }
     });
diff --git a/memento-note/lib/ai/providers/deepseek.ts b/memento-note/lib/ai/providers/deepseek.ts
index b59897b..ea411b3 100644
--- a/memento-note/lib/ai/providers/deepseek.ts
+++ b/memento-note/lib/ai/providers/deepseek.ts
@@ -9,9 +9,21 @@ export class DeepSeekProvider implements AIProvider {
 
   constructor(apiKey: string, modelName: string = 'deepseek-chat', embeddingModelName: string = 'deepseek-embedding') {
     // Create OpenAI-compatible client for DeepSeek
+    // Disable extended thinking to ensure reliable tool/function calling
     const deepseek = createOpenAI({
       baseURL: 'https://api.deepseek.com/v1',
       apiKey: apiKey,
+      fetch: async (url, options) => {
+        if (options?.body) {
+          try {
+            const body = JSON.parse(options.body as string)
+            // Disable thinking mode — tool calling is unreliable with it enabled
+            body.thinking = { type: 'disabled' }
+            return fetch(url, { ...options, body: JSON.stringify(body) })
+          } catch { /* ignore parse errors */ }
+        }
+        return fetch(url, options)
+      },
     });
 
     this.model = deepseek.chat(modelName);