Claude Code's cross-session messaging is just a JSON directory and one Unix socket per session
LeonKohli · reddit · 2026-09-22
- Claude Code quietly shipped cross-session messaging in v2.1.224, buried as a single changelog line with no announcement.
- Discovery is simply a directory: each session writes /.claude/sessions/<pid>. with its PID, cwd, name, socket path and status, and ListAgents reads that folder — no daemon, no service.
- Transport is one Unix socket per session (mode 0600) carrying newline-delimited JSON messages, with control frames for delivery receipts and idle notifications.
- The author built claude-uds-bridge (MIT, macOS/Linux), a plugin that registers a running Codex task in the registry so it appears in /list-agents and answers like any other session. Original transport work by PeterSR.
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