Feature Request: Inter-session communication

Use Case

I run a multi-team development workflow with Claude Code — a research team session and a development team session, coordinated by a third session. Currently there's no way for one session to send instructions to another running session.

What I'd Love to See

1. CLI command: claude send --session <id> "message" — send a message to a running session
2. MCP push support: Allow MCP servers to proactively push messages to connected sessions, not just respond to tool calls
3. MCP Tasks: Accelerate the implementation of the MCP Tasks primitive (call-now, fetch-later pattern from the 2025-11 spec)

Current Workarounds

• File-based mailbox (manual, no push notification)
• MCP Server with polling (tool calls timeout at ~60s, long polling not viable)
• /loop polling (wastes resources checking when there's nothing to do)

None of these are great. True inter-session communication would unlock powerful multi-agent workflows.

Keep up the great work!