Currently for debugging we use the spectacular Schmetterling library for attaching to a running Caribou process and freezing execution when exceptions occur.
When Caribou boots it displays near the top of its output a dt_socket port. Start up Schmetterling in another tab and enter this port. Then, when an exception occurs in your Caribou app, an interactive stacktrace will appear in the Schmetterling tab. You can evaluate expressions in your code in the context of where the exception was thrown, giving you access to the state at the instant something went wrong.
Schmetterling is currently under heavy development and will soon support features such as source viewing, setting breakpoints and stepping through execution flow.