Covalent Bond

What gopalrajsuresh/covalent-bond MCP server does

The gopalrajsuresh/covalent-bond MCP server gives two MCP-compatible coding agents a shared communication channel across separate machines. It supports encrypted text messages and file transfers, allowing one agent to send context, conventions, or project material to another without requiring inbound network ports between the machines.

A session begins when one side calls bond_connect and receives a short session code. A human passes that code to the other operator through a separate channel, such as chat or voice. The second agent calls bond_join with the code. The code authenticates the pairing and is not sent to the relay.

How it works

The agents communicate through a relay that forwards encrypted traffic. The documented design uses X25519 for key exchange and AES-256-GCM for message encryption. The relay receives routing information and ciphertext, but not the session code, encryption keys, or plaintext. Key confirmation is required before application data is exchanged.

After pairing, bond_status reports the connection state, handshake state, pending transfers, and events received since the previous status call. bond_message handles text communication up to 4,000 characters. bond_send encrypts and submits a file with an optional message. The sender is subject to a 10-second rate limit, a file-type whitelist, and a default 256 KB size limit.

The receiver does not write a file automatically. A pending transfer must be approved with bond_accept; accepted content is written under ~/.covalent/incoming/ and returned with untrusted-data markers. bond_decline discards a transfer without notifying the sender. bond_wait long-polls for messages, files, or disconnects during an active conversation, while bond_end closes the session and clears pending transfers.

Setup and configuration

Install the gopalrajsuresh/covalent-bond MCP server through its npm package with npx -y covalent-bond. The README provides a standard stdio configuration for MCP clients. Node.js 18 or newer is listed as a requirement.

Set COVALENT_RELAY_URL to the public relay URL or to a relay you operate. The project also documents deploying a relay to Cloudflare Workers with Wrangler. Both agents must use a relay that can reach the other participant. After changing configuration, restart the MCP client before checking the connection with bond_status.

The documented flow is to configure the server on both machines, create a session on one machine, share the code out-of-band, join from the other machine, and then exchange messages or files. The session ends after inactivity on the public relay according to the documented 30-minute expiry behavior.

Tools and capabilities

The gopalrajsuresh/covalent-bond MCP server exposes these capabilities:

• Create and join authenticated sessions.
• Send encrypted text messages and files.
• Accept or decline pending file transfers.
• Poll for peer events and inspect connection state.
• End a session and remove pending transfers.

Limitations and notes

The gopalrajsuresh/covalent-bond MCP server does not automatically copy an entire agent setup or make decisions about which files should be shared. File receipt requires human consent, and received content should be treated as untrusted data. The public relay is rate-limited and described as best-effort; sessions expire after inactivity and data is not retained there. File size, file type, and message-length limits also constrain transfers.