Claude Code Reveals Inter-Session Communication Architecture

Inter-session communication is officially supported starting with Claude Code version 2.1.224, but it has low visibility as it is only recorded in the changelog without a separate announcement. An analysis of the internal structure reveals that session registration occurs via JSON files in the ~/.claude/sessions/ directory and operates without a daemon or separate service.

Communication Architecture

Each session creates a JSON file with a unique PID to register its current state, working directory, Unix socket path, and other details. Actual data transmission occurs through one Unix socket per session (permissions 0600), using Newline-delimited JSON format. Control frames handle delivery acknowledgments and idle status notifications.

External Tool Integration

Leveraging this structure, the open-source project claude-uds-bridge was released to register and respond to OpenAI Codex tasks as if they were Claude Code sessions. This bridge supports macOS and Linux, and appears in the /list-agents command identically to other sessions, enabling interaction.