There are many trace switches in Algernon. The following commands turn on selections of them, providing decreasing amounts of information. trace-logic is perhaps the most useful for debugging.
It can be useful to turn on tracing during an operation, using the Lisp versions of the trace commands. For example, to start the trace after it is learned that the color of block is red,
(:rules blocks ((color ?b red) -> (:eval (acom-trace-logic))))