🤖 feat: Global MCP configuration for sharing servers across projects

[stirby]

Problem

Currently, MCP servers are configured per-project in .mux/mcp.jsonc. When using the same MCP server (e.g., Svelte, GitHub, database tools) across multiple projects, users must duplicate the entire server configuration in each project's config file.

This leads to:

• Tedious repetition — copying the same server definitions to every project
• Maintenance burden — updating a server config requires changes in every project
• Inconsistency — easy to have slight variations across projects that cause confusion

Proposed Solution

Introduce a global MCP configuration stored in ~/.mux/mcp.jsonc (or similar) that defines servers available across all projects.

Configuration Hierarchy

~/.mux/mcp.jsonc          # Global servers (available everywhere)
<project>/.mux/mcp.jsonc  # Project-specific servers (committed to repo)
<workspace>/.mux/mcp.local.jsonc  # Workspace overrides (gitignored)

Per-Project Toggle

Users should be able to enable or disable specific global MCPs on a per-project basis. This could work via:

1. Opt-out model — Global servers are available by default, projects can disable specific ones:

   // <project>/.mux/mcp.jsonc
   {
     "globalDisabled": ["some-server-i-dont-need-here"]
   }

2. Opt-in model — Global servers must be explicitly enabled per-project:

   // <project>/.mux/mcp.jsonc
   {
     "globalEnabled": ["svelte", "github"]
   }

3. UI toggle — The MCP panel shows global servers with a toggle to enable/disable them for the current project

User Stories

• As a user working on multiple Svelte projects, I want to configure the Svelte MCP once and have it available everywhere
• As a user, I want to quickly add my "commonly used" MCP servers to a new project without manual config copying
• As a user working on a project that doesn't need certain global servers, I want to disable them to reduce noise

Alternatives Considered

• Copy config via Mux agent — Users can ask Mux to copy MCP config between projects, but this still results in duplication
• Symlinks — Technical users could symlink configs, but this is fragile and not user-friendly

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Generated with mux • Model: anthropic:claude-opus-4-5 • Thinking: high • Cost: $0.58