Claude Code sessions can message each other but still overwrite shared files

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Anthropic's Claude Code supports cross-session messaging via ListAgents and SendMessage tools, allowing separate AI coding sessions to communicate — but this coordination channel does not prevent file conflicts. Two sessions pointed at the same file in a shared directory can silently overwrite each other's changes, as there is no underlying file-locking or merge mechanism. The feature requires Claude Code version 2.1.224 or later on macOS, Linux, and WSL 2, and 2.1.234 or later on native Windows. Developers are advised to use the worktree-per-session approach, where each session gets its own directory and branch, enforcing file isolation rather than relying on agent agreement. For files that multiple sessions must edit, the recommended practice remains assigning a single owner at a time and requiring a commit before any handoff.

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