Feature: Inter-session communication between Claude Code instances

Problem

When using Claude Code for multi-agent workflows (orchestrator + workers), there is no way for one session to communicate with another. Sessions are completely isolated, even when running on the same machine working on the same codebase.

Current Workaround

Using a tmux MCP server to spawn and interact with agent sessions. This works but has significant friction:

• Permission prompts block unattended agents (requires --dangerously-skip-permissions or manual approval)
• Shell initialization (oh-my-zsh update prompts, etc.) interferes with first commands
• send_keys has edge cases with key name parsing
• No structured communication, just pasting text into terminals
• Orchestrator can't see agent output without polling capture_pane

Proposed Feature

Allow Claude Code sessions on the same machine to discover and communicate with each other.

Minimum viable version:

• claude --list-sessions to see running instances (session ID, working directory, status)
• Session output tailing from another instance (read-only visibility into what another session is doing)

Ideal version:

• Inter-session messaging: one session can send a structured message to another
• An orchestrator session can spawn worker sessions and receive their results
• Workers can ask questions that route to the orchestrator instead of blocking on a permission prompt

Use Case

A common workflow for power users:

1. Open a "strategy" session to plan work and make decisions
2. Spawn worker sessions for parallel implementation tasks (e.g., polish a UI component, fix a bug, refactor a module)
3. Workers hit questions or decisions that need the orchestrator's input
4. Currently: worker blocks on a permission prompt or makes a guess. User must manually switch terminals to approve/respond.
5. Ideal: worker sends a question to the orchestrator, orchestrator responds, worker continues autonomously.

This pattern is increasingly common as people use Claude Code for larger tasks that benefit from parallelism. The team/swarm features in Claude Code are a step in this direction, but they only work within a single session's context. Cross-session communication would unlock true multi-terminal workflows.

Environment

• macOS (primary), Linux
• Multiple iTerm2 tabs or tmux panes running separate claude instances
• Typical setup: 2-4 concurrent sessions