RhinoAI receives 0 tools (tools/list fails with InvalidHTTPResponse)

Rhino AI
1

Hi McNeel team,

The AI panel opens and Claude answers simple text prompts, but it can never use any Rhino tool. Asking it to create a layer or a sphere always returns: “I don’t have access to Rhino tools in this session.”

Environment

  • Rhino 9 BETA 9.0.26293.12303 (20/10/2026), French UI
  • Windows 11 Pro for Workstations (10.0.26300), x64
  • Claude Code 2.1.302, logged in with a claude.ai Pro account
  • Claude Code was installed with winget (Anthropic.ClaudeCode). The panel did not find it there (“Not found on search paths”), so I copied claude.exe to %USERPROFILE%.local\bin\claude.exe. After restarting Rhino the panel showed “Claude is ready”.

What I observed

  1. The panel starts Claude Code as a child of Rhino with this command line (abridged): claude.exe -p --input-format stream-json --output-format stream-json --verbose --mcp-config {“mcpServers”:{“rhino”:{“type”:“http”,“url”:“http://localhost:10500/agent”}}} --strict-mcp-config --tools “” --allowedTools “mcp__rhino__*” …
  2. The session log shows the API request is sent with an empty tools array.
  3. Running the same command outside Rhino with --debug mcp, the init event reports the rhino server as “connected” with 0 tools. The debug log says:
    • MCP server “rhino”: version negotiation probe failed on the http transport; reconnecting pinned legacy
    • MCP server “rhino”: Successfully connected (transport: http)
    • MCP server “rhino”: HTTP connection dropped after 0s uptime
    • MCP server “rhino”: Connection error: InvalidHTTPResponse fetching “http://localhost:10500/agent”
    • MCP server “rhino”: tools/list failed (InvalidHTTPResponse …); retrying
    • the same error for resources/list
  4. The server itself looks fine from other clients. From Rhino’s Python, from a raw socket (keep-alive: initialize, notifications/initialized (204), tools/list, resources/list) and from the system Node 26.13 fetch, tools/list returns HTTP 200 with a valid Content-Length (35643 bytes, 44 tools). A GET on /agent returns 405 with chunked encoding.
  5. The result is the same with ENABLE_TOOL_SEARCH=false and without --tools “”.

So the failure seems to be specific to the MCP HTTP client inside Claude Code 2.1.302 talking to the Rhino /agent endpoint. I cannot tell whether the cause is on the Rhino side (some detail of the HTTP responses from Microsoft-HTTPAPI) or in Claude Code.

The outside-Rhino route works on the same machine (MCPConnect with the router: I can create and inspect objects in the same Rhino 9 session).

Questions

  • Is this a known issue? Is there a Claude Code version you tested the panel with?
  • Is there a log I can send from the plugin, or a debug option for the /agent endpoint?

Also a small suggestion related to RH-99169: please add the winget install location (%LOCALAPPDATA%\Microsoft\WinGet\Packages\Anthropic.ClaudeCode_*) to the Claude search paths, or let users set the path.

I can provide the full debug log if useful.

Thanks,
Aurélien