MCP config tools panic with "interface conversion: interface {} is nil, not string" when using protocol version 2025-11-25

[mahrens61]

Bug Report

Version: nginx-ui 2.3.5 (build 516, commit 1a9cd29)
OS: Linux (amd64)
MCP Client: Claude Desktop (mcp-remote 0.1.38, protocol version 2025-11-25)

Description

All MCP configuration tools panic with an interface conversion error when called via Claude Desktop. Only nginx_status and nginx_config_base_path work correctly.

Affected tools

• nginx_config_list
• nginx_config_get
• nginx_config_add
• nginx_config_modify
• nginx_config_rename
• nginx_config_mkdir
• nginx_config_history
• nginx_config_enable

Error message

MCP error -32603: panic recovered in nginx_config_list tool handler:
interface conversion: interface {} is nil, not string

Steps to reproduce

1. Configure nginx-ui as an MCP server in Claude Desktop using mcp-remote with --transport sse-only
2. Connect successfully (nginx_status returns {"running":true})
3. Call any config tool, e.g. nginx_config_list with path /etc/nginx
4. Server panics with the above error

Expected behavior

Config tools should return the list/content of Nginx configuration files.

Suspected cause

Likely a parameter deserialization mismatch between the MCP protocol version 2025-11-25 used by Claude Desktop and the mcp-go version bundled with nginx-ui 2.3.5. The tool handlers appear to receive nil instead of the expected string for path parameters.