copilot plugin install does not register plugin MCP servers into ~/.copilot/mcp-config.json

[Sozhan308]

Describe the bug

When a plugin ships an .mcp.json (referenced via "mcpServers": ".mcp.json" in plugin.json, running

copilot plugin install correctly copies the file to ~/.copilot/installed-plugins/_direct//.mcp.json — but those servers are never registered in ~/.copilot/mcp-config.json and are therefore invisible to the CLI.

Affected version

1.0.68

Steps to reproduce the behavior

• Create a plugin with plugin.json declaring "mcpServers": ".mcp.json" and a .mcp.json with one or more stdio servers.
• Run copilot plugin install ./my-plugin
• Run copilot mcp list → shows "No MCP servers configured"
• Verify the .mcp.json was copied: cat ~/.copilot/installed-plugins/_direct/my-plugin/.mcp.json → file exists with correct content
• Start a session with copilot cli and switch to agent from plugin invoke any tool from the plugin's MCP server → tool not found

Expected behavior

• copilot plugin install should merge the plugin's MCP server definitions into ~/.copilot/mcp-config.json

Additional context

Actual behavior: copilot mcp list reports "No MCP servers configured" even after installing a plugin that declares MCP servers. The agent in the same plugin references those tools by name (e.g. jira-mcp-server/jira_request) but they are unavailable at runtime, causing tool-not-found errors.

Environment:

Copilot CLI: 1.0.68
OS: Linux
Plugin manifest field: "mcpServers": ".mcp.json"

The .mcp.json uses VS Code's ${input:...} syntax for secure credential prompting. The CLI has no equivalent interactive input mechanism, so a complete fix would also need either:

Support for ${input:...} resolution at session start (prompt user for values)