bug:

[sailin-x]

---

Title:
OpenRouter Free Models: All AI Commands Fail with JSON Parse Errors (parse-prd, add-task, etc.)

---

Body:

Describe the bug
All AI-powered commands (e.g., parse-prd, add-task) fail with JSON parsing errors when using any free OpenRouter model as the main model. No tasks are generated from the PRD, and completions do not work.

To Reproduce
Steps to reproduce the behavior:

1. Install latest Task Master AI globally:
   npm install -g task-master-ai
2. Set up .cursor/mcp.json with a valid OpenRouter API key:

   {
     "mcpServers": {
       "task-master-ai": {
         "env": {
           "OPENROUTER_API_KEY": "sk-or-..."
         }
       }
     }
   }

3. Set main model to a free OpenRouter model, e.g.:

   npx task-master-ai models --set-main deepseek/deepseek-chat-v3-0324:free --openrouter
   

4. Run:

   npx task-master-ai parse-prd --input=scripts/prd.txt
   

   or

   npx task-master-ai add-task --prompt="Test if OpenRouter works"
   

Expected behavior
Tasks should be generated from the PRD, and completions should work.

Actual behavior
All AI commands fail with errors like:

[FastMCP error] SyntaxError: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    ...
[FastMCP error] SyntaxError: Unexpected token 'p', "npx task-ma"... is not valid JSON
    at JSON.parse (<anonymous>)
    ...

Environment:

• OS: macOS (Apple Silicon)
• Node.js: v23.11.0
• Task Master AI: latest (as of June 2024)
• OpenRouter API key: valid, free tier
• Models tried: deepseek/deepseek-chat-v3-0324:free, google/gemma-3-12b-it:free, mistralai/mistral-small-3.1-24b-instruct:free, etc.

Additional context

• Model selection and API key detection work (no auth errors).
• Manual task management and documentation features work.
• The error only occurs on AI completions.
• I have tried updating Task Master AI, switching models, and restarting the MCP server and Cursor.
• The same error occurs for all free OpenRouter models.

Full error output:

[FastMCP warning] could not infer client capabilities

[FastMCP error] SyntaxError: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    at deserializeMessage (file:///opt/homebrew/lib/node_modules/task-master-ai/node_modules/@modelcontextprotocol/sdk/dist/esm/shared/stdio.js:26:44)
    ...
[FastMCP error] SyntaxError: Unexpected token 'p', "npx task-ma"... is not valid JSON
    at JSON.parse (<anonymous>)
    ...

.cursor/mcp.json (redacted):

{
  "mcpServers": {
    "task-master-ai": {
      "env": {
        "OPENROUTER_API_KEY": "sk-or-..."
      }
    }
  }
}

---

[Crunchyman-ralph]

can I see the whole mcp.json with api keys redacted.

Can I also see your .taskmasterconfig ?

Moving this to discussions as I think this seems like a setup issue

[sailin-x]

Hi! Thanks for your response. Here are the files you requested, with API keys redacted.

---

.cursor/mcp.json

{
    "mcpServers": {
        "task-master-ai": {
            "command": "npx",
            "args": [
                "-y",
                "--package=task-master-ai",
                "task-master-ai"
            ],
            "env": {
                "ANTHROPIC_API_KEY": "ANTHROPIC_API_KEY_HERE",
                "PERPLEXITY_API_KEY": "PERPLEXITY_API_KEY_HERE",
                "OPENAI_API_KEY": "OPENAI_API_KEY_HERE",
                "GOOGLE_API_KEY": "GOOGLE_API_KEY_HERE",
                "XAI_API_KEY": "XAI_API_KEY_HERE",
                "OPENROUTER_API_KEY": "OPENROUTER_API_KEY_HERE",
                "MISTRAL_API_KEY": "MISTRAL_API_KEY_HERE",
                "AZURE_OPENAI_API_KEY": "AZURE_OPENAI_API_KEY_HERE",
                "OLLAMA_API_KEY": "OLLAMA_API_KEY_HERE"
            }
        }
    }
}

---

.taskmasterconfig

{
  "models": {
    "main": {
      "provider": "openrouter",
      "modelId": "openrouter/auto",
      "maxTokens": 120000,
      "temperature": 0.2
    },
    "research": {
      "provider": "perplexity",
      "modelId": "sonar-pro",
      "maxTokens": 8700,
      "temperature": 0.1
    },
    "fallback": {
      "provider": "anthropic",
      "modelId": "claude-3-5-sonnet-20240620",
      "maxTokens": 8192,
      "temperature": 0.1
    }
  },
  "global": {
    "logLevel": "info",
    "debug": false,
    "defaultSubtasks": 5,
    "defaultPriority": "medium",
    "projectName": "Taskmaster",
    "ollamaBaseUrl": "http://localhost:11434/api",
    "azureOpenaiBaseUrl": "https://your-endpoint.openai.azure.com/",
    "userId": "1234567890"
  }
}

---

What We’ve Tried

• Reinstalled Task Master AI globally (npm uninstall -g task-master-ai && npm install -g task-master-ai)
• Tested with both paid and free models (OpenRouter, Perplexity, etc.)
• Confirmed API keys are present and detected (no auth errors)
• Tried setting main model to various free OpenRouter models (e.g., deepseek/deepseek-chat-v3-0324:free, google/gemma-3-12b-it:free, mistralai/mistral-small-3.1-24b-instruct:free)
• Restarted MCP server and Cursor
• Manual task management and documentation features work fine

---

Ongoing Issue

• All AI-powered commands (parse-prd, add-task, etc.) fail with JSON parsing errors when using any free OpenRouter model as the main model.
• No tasks are generated from the PRD, and completions do not work.
• Error examples:

  [FastMCP error] SyntaxError: Unexpected end of JSON input
  [FastMCP error] SyntaxError: Unexpected token 'p', "npx task-ma"... is not valid JSON
  

• This only happens with free OpenRouter models. Paid models and Perplexity work, but we want to use the free tier if possible.

---

Let us know if you need any more info or want us to try something else! Thanks for looking into this.

---

[Crunchyman-ralph]

Hey!

So actually we haven't been able to fully support openrouter because there are so many models out there.

So we decided to only support openrouter models that have tool_use.

The thing is that most openrouter free models don't have tool use at the moment. as soon as they do, we will be able to support them!

[sailin-x]

ah thank you very much for the clarification. cheers