Hi ChatGPT told me that parallelism doesn't rule out debugging categorically. You can do it (so it tells me) with a grade which contains "par.gc.debug". Is this bullshit? I couldn'tĀ build the libraries in the grade "asm_fast.par.gc.debug.stseg". I got: mercury_compile: Debugging is not available in parallel grades. Cheers, Volker