Connect an Agent (Experimental)

You need:

• JetCad3 installed and running;
• Codex, Claude Code, or another MCP-compatible client installed on the same computer; and
• the JetCad3 project you want to use open in its own tab.

Keeping a project open does not give an agent access by itself—the client must connect and explicitly bind that tab. In this experimental release, the automation tools operate in Drafting even if the project also contains work from other workspaces.

1. Open Settings → Agentic MCP.
2. Check Enable Agentic MCP.
3. Leave the loopback port at 47330 unless another local program already uses it.
4. Save Settings.
5. Reopen Settings → Agentic MCP and confirm the listener says Running.

The default local endpoint is:

http://127.0.0.1:47330/mcp

Keep JetCad3 running while the agent is connected.

1. In Settings → Agentic MCP, click Copy Codex config.
2. Add the copied block to your Codex configuration file:
   • macOS and Linux: ~/.codex/config.toml
   • Windows: %USERPROFILE%\.codex\config.toml
3. Close the current Codex session and start a fresh one.

The copied block already contains the correct local URL and pairing token. It has this shape:

[mcp_servers.jetcad3]
url = "http://127.0.0.1:47330/mcp"
http_headers = { Authorization = "Bearer <pairing-token>" }

Use the text copied from JetCad3; do not type the token shown above.

1. In Settings → Agentic MCP, click Copy Claude command.
2. Paste and run that command in the terminal where you use Claude Code.
3. Close the current Claude Code session and start a fresh one.

JetCad3 generates a command with the local endpoint and pairing token already included. The connection is registered under the name jetcad3.

Click Copy JSON and paste the result into your client's MCP server settings. The configuration uses Streamable HTTP, the local /mcp endpoint, and an Authorization header containing the pairing token.

If the client asks for the transport separately, choose HTTP or Streamable HTTP. The connection will not work from a different computer because JetCad3 deliberately accepts loopback connections only.

Open the desired project in JetCad3 before starting the agent session. You can then ask the agent plainly:

Use the JetCad3 MCP to inspect the open project and help me model this part.

A correctly connected agent can discover JetCad3, list the open tabs, bind the project you choose, read its Project Memory and geometry, and then ask for any design decisions it still needs. The agent should use revision checks, checkpoints, evaluation waits, and current screenshots while it works.

Only one project tab is bound by a particular document handle. Opening or closing other tabs does not silently redirect the agent to a different design.

The pairing token authorizes local control of JetCad3. Treat copied client configuration like a password:

• do not post it in screenshots, forum messages, or shared project files;
• do not commit it to a repository;
• use Rotate Pairing Token if it may have been exposed; and
• copy a fresh configuration into every client after rotating it.

Rotating the token immediately disconnects existing MCP sessions. Disabling Agentic MCP also closes all connected sessions.

The agent has no JetCad3 tools

Confirm the listener says Running, then start a completely fresh agent session. Most clients load their MCP tool list when a session starts and will not add a newly configured server to a conversation that is already open.

Connection refused or “fetch failed”

JetCad3 is not running, Agentic MCP is disabled, or the configured port does not match. Reopen Settings, confirm the running endpoint, and copy the configuration again.

“No valid MCP session ID was provided” after restarting JetCad3

The application restart ended the old transport session. Start a fresh agent session so the client negotiates a new MCP connection.

The pairing token is rejected

Use Copy Codex config, Copy Claude command, or Copy JSON again. If necessary, rotate the pairing token and replace the old client configuration.

The agent cannot find the project

Make sure the project is open in JetCad3. Ask the agent to list documents and bind the desired tab again; document handles do not survive closing or replacing a tab.

The listener cannot start

Another local program may already be using the selected port. Choose a different port, save Settings, then copy a new client configuration because the endpoint changed.