I once asked Claude Code to do a moderately complex refactor. Seven or eight minutes in, the terminal was still scrolling.
I couldn't tell where it was stuck. No Bash error, the model was still producing output — it was just slow. Was it re-reading the same file dozens of times? Waiting on IO in some command? Stuck in a loop? Terminal output is all past tense: it scrolls by and it's gone. When the task finally finished, I still couldn't say where the time went.
Then I tried cctrace. Same task, but afterwards I opened the waterfall timeline. One glance: a single Bash tool call had hung for almost two minutes, with batches of fast Read calls before and after it, and a dozen tool results in between. The problem went from "no idea" to "oh, it's right there."
cctrace does one simple thing: it turns a whole agent session into a waterfall timeline you can actually read.
1. The stuff you can't see
