🤖 feat: Global MCP configuration with per-project toggle support

[stirby]

Problem

Currently, MCP servers are configured per-project in .mux/mcp.jsonc. This means users who want to use the same MCP server (e.g., Svelte, GitHub, a custom tooling server) across multiple projects must manually duplicate the configuration in each project's .mux/mcp.jsonc file.

This is tedious and repetitive, especially for:

• Framework-specific MCPs (Svelte, React, Vue) used across many projects
• General-purpose MCPs (GitHub, Slack, database tools) that are useful everywhere
• Custom internal MCPs that a developer uses in their daily workflow

When an MCP configuration needs updating (e.g., new command flags, updated path), users must update it in every project individually.

Proposed Solution

Introduce a global MCP configuration that lives in ~/.mux/mcp.jsonc (or similar). This would define MCP servers available across all projects without duplication.

Key requirements:

1. Global config file: ~/.mux/mcp.jsonc containing MCP server definitions
2. Per-project toggle: Projects should be able to:
   • Enable/disable specific global MCPs (not all global MCPs are relevant to all projects)
   • Override global MCP settings at the project level if needed
3. Precedence: Project-level config should take precedence over global config for the same server name
4. UI support: The MCP panel should show:
   • Which MCPs are global vs project-level
   • Toggle controls for enabling/disabling global MCPs in the current project

Example configuration hierarchy:

~/.mux/mcp.jsonc (global)
├── github-mcp (enabled everywhere by default)
├── svelte-mcp (enabled everywhere by default)
└── internal-tools (enabled everywhere by default)

<project>/.mux/mcp.jsonc (project-level)
├── svelte-mcp: disabled (this project uses Vue)
├── vue-mcp: { ... } (project-specific)
└── internal-tools: { command: "..." } (override global config)

Alternatives Considered

• Copy config via Mux agent: Users can ask Mux to copy MCP config from project A to B, but this still results in duplication and drift over time
• Symlinks: Technical users could symlink config files, but this is fragile and not user-friendly

Additional Context

User feedback from Discord highlights this as a common pain point for developers working across multiple projects with shared tooling needs.

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

[ethanndickson]

Closing as duplicate of #1650