I gave Claude Code two GitHub issue links and asked it to fix a Codex CLI scrollback bug in zellij.
To "read" them, it used WebFetch tool, which pipes the page through a summarizer model. The summary came back saying the threads had no real discussion of root cause or fixes.
So it trusted that, skipped the actual comments, and went straight to the source code.
1/3
Then it did genuinely good work: traced the regression through the Rust TUI source, found the exact change that broke zellij scrollback, wrote a patch and a regression test, and spent 32 minutes building a fat-LTO binary.
It even verified the fix by capturing the terminal escape sequences and proving the scroll-region codes zellij chokes on were gone.
Then I asked: can we even upstream this?
2/3
The answer was in the comments WebFetch had summarized away.
A codex maintainer said they removed the zellij workaround on purpose, because zellij 0.44.1 fixed it upstream. zellij's own release notes have a "Codex scrolling bug" line. I was on 0.44.0.
The fix: cargo install zellij. One patch version.
I handed it the answer. It rebuilt the answer from scratch, because a summarizer ate the comments.
Lesson learnt: do NOT trust WebFetch to be accurate. It's a summarizer, not literal
3/3
Cengiz Can