Status line: expose active agents and connected MCP servers in stdin JSON

Feature Request

Summary

Add active agent invocations and connected MCP server state to the status line stdin JSON, so custom status line scripts can display real-time session state.

Current behaviour

The stdin JSON passed to statusLine.command contains:

• model (display name, id)
• context_window.used_percentage
• cost.total_cost_usd
• workspace.current_dir

It does not contain which agents have been invoked or which MCP servers are actually connected.

Desired behaviour

Add two fields to the stdin JSON:

{
  "agents": {
    "available": ["sustainable-coder", "reviewer"],
    "active": ["sustainable-coder"]
  },
  "mcp": {
    "configured": ["gmail", "n8n", "ide"],
    "connected": ["n8n", "ide"]
  }
}

• agents.available — agents loadable from ~/.claude/agents/ and project .claude/agents/
• agents.active — agents currently invoked/running in this session
• mcp.configured — servers in mcp.json
• mcp.connected — servers that successfully connected at session start

Why this matters

Custom status lines (via statusLine.command) are a powerful way to surface session state in the terminal. Right now scripts can only approximate this by listing config files — they can't distinguish a connected MCP from a broken one, or know if an agent is currently running.

This would enable status lines like:

MINAI | claude-sonnet-4-6 | ctx:42% | $0.18
agents:sustainable-coder(active) | mcp:n8n✓ ide✓ gmail✗

Workaround

Currently listing all files in ~/.claude/agents/ and all keys in mcp.json as an approximation. Works for configured state, not actual connection/activity state.

🤖 Submitted via Claude Code