What I missed here was the importance of keeping careful notes as you go. What exactly happened when we constructed that weird input and commented out line 353?

What I missed here was the importance of keeping careful notes as you go. What exactly happened when we constructed that weird input and commented out line 353? What hypotheses are we entertaining? Can we rule out any of them based on our evidence? It’s very easy to dupe yourself if you’re doing it all in your head.