shared-file-guard

A Claude Code mod for running several sessions on the same project. It refuses a shell command that would write a shared file (STATUS.md, CLAUDE.md, MEMORY.md, or the files you name) when this session never read it, or another session changed it since. Part of claude-plugins.

What it does

• The Edit and Write tools already refuse a file that changed since it was read. This closes the shell gap: heredocs, python3 scripts, sed -i, tee, mv and cp.
• The refusal names the file and tells Claude to read it again, merge, then write.
• A cat or grep counts as a read; a session's own writes do not block its next one; creating a file that does not exist yet is allowed.
• /shared-file-guard lists the files this session has seen; /shared-file-guard off|on.
• If the mod fails, the command runs as normal.

Settings

| Setting | Default | What it does | |---|---|---| | watched_files | STATUS.md,CLAUDE.md,MEMORY.md | Comma separated file names; * matches any run of name characters, such as *register*.md |

What it reads and does

• Reads: which shared files (the project's status, instructions, memory and register files) this session read and when they last changed on disk, and the command line of each shell command.
• Does: refuses a shell write to a shared file that another session changed since this one read it, and logs a line saying so.
• Hooks: tool.call on Read, Edit and Write only records what was read. tool.call on Bash may refuse that one command; it never changes it. command.run answers its own /shared-file-guard command and no other.
• Privacy: see PRIVACY.md.
• Never: sends anything anywhere (no network calls, no telemetry).

Install

Needs Claude Code 2.1.287 or later (mods). Tested on 2.1.289.

/plugin marketplace add mutlumehmet/claude-plugins
/plugin install shared-file-guard@mehmetmutlu

A mod runs inside Claude Code with your permissions. Read the code before you install any mod. Settings are asked for at install, or later with /plugin configure shared-file-guard@mehmetmutlu.

Known gaps

• Paths built inside a script, and relative paths after a cd in the same command, are not seen.
• It compares date and size, not a hash.

About

Made by Mehmet Mutlu, part of claude-plugins. More of his work at mehmetmutlu.dev.

License

MIT