Play Troubleshooting

START Does Nothing

Check that the browser is connected to the right WebSocket port.

For custom ports:

lantern play --ws-port 8790 --http-port 8791

open:

http://127.0.0.1:8791?ws=8790

The UI also infers ws = http_port - 1, so http://127.0.0.1:8791 should connect to 8790.

UI Is Stale After Updating AgentLantern

An already-open tab can keep old JavaScript in memory. Close the tab and reopen the printed URL.

If installed with uv tool:

uv tool install --force git+https://github.com/brellsanwouo/agentlantern.git

When developing from a local checkout:

uv tool install --force --refresh .

Port Already in Use

Use another HTTP/WebSocket pair:

lantern play --ws-port 8792 --http-port 8793

Run Starts but Agents Do Not Move

The target project may be blocked by:

• missing API keys,
• long model calls,
• dependency installation,
• a tool call,
• project startup errors.

Check the Log panel and the terminal running lantern play.

Stop a Run

Use STOP in the UI first.

If the process does not exit, press Ctrl+C in the terminal running lantern play.