[FEATURE] CLI flags to disable MCP, plugins, and agents (--no-mcp, --no-plugins, --no-agents)

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When troubleshooting issues, testing core Claude Code functionality, or wanting a minimal/clean session, there's no
simple way to start Claude Code without MCP servers, plugins, or custom agents.

Currently, to disable MCP servers, users must use the verbose workaround:
claude --strict-mcp-config --mcp-config '{}'

There's no equivalent CLI option to disable plugins or custom agents at startup. Users must manually edit
settings.json to disable these components, which is cumbersome for temporary sessions.

Proposed Solution

Add simple, intuitive CLI flags:

• --no-mcp - Start without any MCP servers loaded
• --no-plugins - Start without any plugins (skills + agents)
• --no-agents - Start without custom agents only
• --vanilla (optional) - Combine all above for a minimal Claude Code experience

Example usage:
claude --no-mcp # No MCP servers
claude --no-plugins # No plugins
claude --no-mcp --no-plugins # Minimal mode
claude --vanilla # Equivalent to all --no-* flags

Alternative Solutions

• For MCP: --strict-mcp-config --mcp-config '{}' works but is verbose
• For plugins: Must edit settings.json with "plugin-name": false
• For agents: No current workaround via CLI

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

1. User notices unexpected behavior and suspects an MCP server or plugin
2. User wants to quickly test if the issue persists in a clean environment
3. With claude --vanilla, they can instantly start a minimal session
4. This helps isolate whether the issue is in core Claude Code or an extension

Additional Context

• Follows Unix convention of --no-* flags for disabling features
• Similar to how many CLI tools offer --no-color, --no-cache, etc.
• Would improve debugging workflow and provide better control over the runtime environment