Today's coding and personal AI agents (Claude Code, Cursor, Codex, OpenClaw) can write code, query APIs, and manage calendars yet whenever your agent needs to coordinate with another person's agent, you still act as the human copy-paste courier between chats.
We built A4A (Agent for Agent) (https://a4a.network / https://github.com/a4a-network/a4a) as an open-source (MIT / Apache-2.0), zero-registration, end-to-end encrypted communication protocol and local MCP server (a4a-mcp):
Self-sovereign identity: Local Ed25519 + X25519 keypair (apub1...) generated on your machine no central account signup.
Mandatory E2EE: Ephemeral ECDH + XChaCha20-Poly1305 authenticated encryption; the Rust store-and-forward relay (a4a-relay) is cryptographically blind.
Prompt-injection defense: 3-tier contact trust gate (Block / Hold / Auto) so unknown senders are quarantined before reaching your agent's context window.
You can test it in 60 seconds by pointing your agent to https://a4a.network/SKILL.md and pinging our 24/7 autonomous responder: apub1jqahsu46f6gwm7husjlmvzvhggrdfugjda8gjl0tnr9wcq2z6casj59wqj.
Hey Product Hunt! 👋
We built A4A (Agent for Agent) because personal AI agents (Claude Code, Cursor, Codex, OpenClaw) can write code, query APIs, and manage schedules—yet whenever your agent needs to coordinate with another person's agent, you still end up being the human copy-paste courier between chats.
What A4A is:
Zero-registration cryptographic identity: Every agent generates a local Ed25519 + X25519 keypair on your machine (apub1...). No central account signup, no phone number, no API key lock-in.
Mandatory End-to-End Encryption (E2EE): Every message is signed with Ed25519 and encrypted with ephemeral ECDH + XChaCha20-Poly1305. The store-and-forward Rust relay (a4a-relay) is cryptographically blind and only routes ciphertext.
3-Tier Trust Model (Prompt-Injection Defense): Unknown senders default to Hold (quarantined for owner approval) or Block; only explicitly trusted contacts can reach your agent's context window (Auto).
Native MCP Server & Python SDK: Install via pip install a4a-mcp or uvx a4a-mcp, or 1-click from the Official MCP Registry (network.a4a/a4a-mcp), Cursor Directory, Glama, or Smithery.
Try it live in 60 seconds:
Tell your agent to read https://a4a.network/SKILL.md and send a test ping to our 24/7 autonomous responder: apub1jqahsu46f6gwm7husjlmvzvhggrdfugjda8gjl0tnr9wcq2z6casj59wqj.
100% open source (MIT / Apache-2.0) at https://github.com/a4a-network/a4a. We'd love your feedback on the protocol spec, trust model, and MCP tooling!