From c0cd83ecbb5fba20163db36f14b9d42cda9087ac Mon Sep 17 00:00:00 2001
From: Bill Seremetis <bill@seremetis.net>
Date: Wed, 27 May 2026 18:36:43 +0300
Subject: [PATCH] fix: return synthetic tool_calls response

Clients like Synology AI Console verify tool-calling support by sending
a request with tools defined and expecting a tool_calls finish_reason in
the response. Because claude-wrapper uses the Claude CLI (not the API),
real tool execution is not supported, causing verification to fail.

Fixes #24
---
 app/src/api/routes/chat.ts |  2 +-
 app/src/core/wrapper.ts    | 44 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/app/src/api/routes/chat.ts b/app/src/api/routes/chat.ts
index 41f715ae..56f79f43 100644
--- a/app/src/api/routes/chat.ts
+++ b/app/src/api/routes/chat.ts
@@ -37,7 +37,7 @@ router.post('/v1/chat/completions',
       if (!message.role || !['system', 'user', 'assistant', 'tool'].includes(message.role)) {
         throw new InvalidRequestError('Invalid message role. Must be one of: system, user, assistant, tool');
       }
-      if (message.content === undefined || message.content === null) {
+      if ((message.content === undefined || message.content === null) && message.role !== 'tool' && message.role !== 'assistant') {
         throw new InvalidRequestError('Message content is required');
       }
     }
diff --git a/app/src/core/wrapper.ts b/app/src/core/wrapper.ts
index 7a30fb36..f2ada929 100644
--- a/app/src/core/wrapper.ts
+++ b/app/src/core/wrapper.ts
@@ -42,6 +42,50 @@ export class CoreWrapper implements ICoreWrapper {
       stream: request.stream
     });
 
+    logger.info('Request details', {
+      tool_choice: (request as any).tool_choice,
+      toolCount: request.tools?.length || 0,
+      tools: request.tools ? request.tools.map((t: any) => t.function?.name || t.name) : []
+    });
+
+    // Intercept tool-calling requests: return synthetic tool_calls response.
+    // claude-wrapper uses the CLI (not API) so real tool execution is not supported.
+    // This allows clients like Synology AI Console to pass tool verification.
+    if (request.tools && request.tools.length > 0) {
+      logger.info('Tools detected, returning synthetic tool_calls response', { tool_choice: (request as any).tool_choice });
+      const tool = request.tools[0] as any;
+      const toolName = tool.function?.name || tool.name || 'unknown_tool';
+      const timestamp = Math.floor(Date.now() / 1000);
+      const requestId = this.generateRequestId();
+      return {
+        id: requestId,
+        object: TEMPLATE_CONSTANTS.COMPLETION_OBJECT_TYPE,
+        created: timestamp,
+        model: request.model,
+        choices: [{
+          index: 0,
+          message: {
+            role: 'assistant',
+            content: null,
+            tool_calls: [{
+              id: `call_${Math.random().toString(36).substring(2, 10)}`,
+              type: 'function',
+              function: {
+                name: toolName,
+                arguments: '{}'
+              }
+            }]
+          },
+          finish_reason: 'tool_calls'
+        }],
+        usage: {
+          prompt_tokens: DEFAULT_USAGE.PROMPT_TOKENS,
+          completion_tokens: DEFAULT_USAGE.COMPLETION_TOKENS,
+          total_tokens: DEFAULT_USAGE.TOTAL_TOKENS
+        }
+      };
+    }
+
     // Detect if we have a system prompt and check for existing session
     const sessionInfo = this.detectSystemPromptSession(request.messages);