Can only use Composer 1 with Perplexity MCP server

[Geoff_White]

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Summary

Perplexity MCP server works correctly with Composer One chat interface but causes ERROR_OPENAI / “Unable to reach the model provider” errors when enabled with other chat interfaces (Gemini Flash, Grok Code, Sonnet 4.5, etc.).

Steps to Reproduce

Steps to Reproduce

1. Configure Perplexity MCP server in ~/.cursor/mcp.json:

   {
     "mcpServers": {
       "perplexity": {
         "command": "node",
         "args": ["/path/to/node_modules/@jschuller/perplexity-mcp/bin.js"],
         "env": {
           "PERPLEXITY_API_KEY": "your-api-key",
           "PERPLEXITY_MODEL": "sonar-pro"
         }
       }
     }
   }
   

2. Restart Cursor IDE

3. Test with Composer One:

   • Open Composer One chat interface
   • Chat works normally
   • Perplexity MCP tools are accessible

4. Test with other chat interfaces:

   • Switch to Gemini Flash, Grok Code, or Sonnet 4.5
   • Attempt to send a chat message
   • Result: ERROR_OPENAI error appears
   • Error message: “Unable to reach the model provider”
   • Chat is completely blocked

Expected Behavior

All chat interfaces should work normally when MCP servers are enabled, regardless of which interface is used.

Actual Behavior

• Composer One: Works correctly with Perplexity MCP enabled
• Other interfaces (Gemini Flash, Grok Code, Sonnet 4.5): Fail with ERROR_OPENAI when Perplexity MCP is enabled
• Other interfaces: Work correctly when Perplexity MCP is disabled

Expected Behavior

Expected Behavior

All chat interfaces should work normally when MCP servers are enabled, regardless of which interface is used.

Actual Behavior

• Composer One: Works correctly with Perplexity MCP enabled
• Other interfaces (Gemini Flash, Grok Code, Sonnet 4.5): Fail with ERROR_OPENAI when Perplexity MCP is enabled
• Other interfaces: Work correctly when Perplexity MCP is disabled

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

• Cursor Version:
  Version: 2.2.43 (Universal)
  VSCode Version: 1.105.1
  Commit: 32cfbe848b35d9eb320980195985450f244b3030
  Date: 2025-12-19T06:06:44.644Z
  Electron: 37.7.0
  Chromium: 138.0.7204.251
  Node.js: 22.20.0
  V8: 13.8.258.32-electron.0
  OS: Darwin arm64 24.6.0
• OS: macOS 24.6.0 (darwin)
• Node Version: v24.2.0
• MCP Server: @jschuller/perplexity-mcp v2.0.1

For AI issues: which model did you use?

The only model that works is Composer 1. All other models don’t work.

Additional Information

Evidence

MCP Server Status

The Perplexity MCP server itself is working correctly:

• Server starts successfully (confirmed in logs: “Storing stdio client user-perplexity”)
• Tools are discovered and registered
• Server responds to MCP protocol messages
• Works perfectly in Composer One interface

Log Evidence

From ~/.cursor/logs/[latest]/window*/exthost/anysphere.cursor-mcp/MCP user-perplexity.log:

[info] Starting new stdio process with command: node /path/to/perplexity-mcp/bin.js
[info] Successfully connected to stdio server
[info] Storing stdio client user-perplexity
[info] CreateClient completed, server stored: true
[info] listOfferings: Found 1 tools

The MCP server initializes successfully, but other chat interfaces still fail.

Error Details

• Error Code: ERROR_OPENAI
• Error Message: “Unable to reach the model provider”
• Additional Info: ConnectError: [unavailable] Error
• Request ID: [varies per attempt]

Workaround

Temporarily disable Perplexity MCP server when using non-Composer-One interfaces:

1. Remove or comment out the perplexity entry in ~/.cursor/mcp.json
2. Restart Cursor
3. Other chat interfaces work normally

Additional Context

MCP Configuration

Full mcp.json configuration (with other working MCP servers):

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "~/path/"],
      "env": {
        "NPM_CONFIG_CACHE": "/path/to/cache"
      }
    },
    "anthropic": {
      "command": "node",
      "args": ["/usr/local/lib/node_modules/server-anthropic/dist/index.js"],
      "env": {
        "ANTHROPIC_API_KEY": "${ANTHROPIC_API_KEY}"
      }
    },
    "openai": {
      "command": "npx",
      "args": ["-y", "openai-mcp-server"],
      "env": {
        "NPM_CONFIG_CACHE": "/path/to/cache",
        "OPENAI_API_KEY": "key"
      }
    },
    "perplexity": {
      "command": "node",
      "args": ["/path/to/node_modules/@jschuller/perplexity-mcp/bin.js"],
      "env": {
        "PERPLEXITY_API_KEY": "key",
        "PERPLEXITY_MODEL": "sonar-pro"
      }
    }
  }
}

Other MCP Servers

• Filesystem MCP: Works with all interfaces
• Anthropic MCP: Works with all interfaces
• OpenAI MCP: Works with all interfaces
• Perplexity MCP: Only works with Composer One

Hypothesis

Composer One appears to have different MCP server initialization/validation logic compared to other chat interfaces. Other interfaces may be:

1. Waiting for all MCP servers to fully initialize before allowing chat
2. Validating MCP servers more strictly
3. Using a different code path that’s incompatible with certain MCP servers
4. Timing out during MCP initialization

Requested Fix

Ensure all chat interfaces handle MCP servers consistently, or at minimum, make MCP server failures non-blocking for chat functionality.

Contact Information

• Email: [[email protected]]
• Cursor Username: [[email protected]]

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Note: This bug report was generated on 2025-12-24. Please include any additional diagnostic information requested by Cursor support.

Does this stop you from using Cursor

No - Cursor works, but with this issue

[deanrie]

Hey, thanks for the report. This looks like a known issue where certain MCP servers can conflict with specific models.

There’s a similar case that was fixed by removing a problematic extension: Unable to Reach Model Provider for All Models Except Composer1

To help diagnose, could you try:

1. Test in a clean profile:

cursor --user-data-dir="CursorData/Test"

Open your project, then try Gemini, Grok, and Sonnet with the Perplexity MCP enabled. Does it work?

2. If it works in the test profile, check extensions:

• Help > Toggle Developer Tools > Console, and look for errors when you send a request
• Try disabling extensions one by one and re-test

3. Collect diagnostics:

• The Request ID from a failed request with Gemini, Grok, or Sonnet
• A screenshot from Developer Tools > Console when the error happens

Let me know the results, especially from the clean profile test. That will help confirm whether this is an extension conflict or an issue in the Perplexity MCP server itself.