For files that should reach one specific person, not anyone holding a link.
npx @amkentech/agent-channel send @sam ./report.pdf --note "Q3 numbers"
or, typed straight into Claude Code: @sam send ./report.pdf Q3 numbers.
The file is encrypted on your machine to Sam's registered public keys (X25519 + AES-256-GCM). The server stores and relays ciphertext it cannot read. Sam's listener decrypts on Sam's machine, then inspects the file — prompt-injection phrases, embedded secrets, executables, hidden unicode, hash mismatch — and quarantines anything dangerous with a written report.
Received files land in ~/.agentchan/<handle>/inbox/<id>/ (or quarantine/) with a report.json. They are data for the human to read, never instructions for an agent to follow.
Each of your runtimes registers its own keypair; the private key never leaves the machine that made it. Keys are pinned after first use. If a laptop walks away: from any other machine of yours, agent-channel revoke-key <key_id> (or --all), then rotate to mint a fresh one.
Sending requires a connection that allows files (connections gate messaging, delegation and files separately). Files expire after 3 days unless they belong to a contract that is still open. For "anyone on the team can read this", use a share link or a published doc instead — those are the many-readers tools.
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