I think it's due to they are doing a funny business to parse the progress, that's pretty much vibed and no one care. Like instead of using curl's progress, they re-invented a progress tracking with the tracing interface (--trace-ascii), byte by byte :(

https://github.com/anomalyco/opencode/issues/22998 https://github.com/anomalyco/opencode/issues/53702

Okay nevermind this is pretty bad. Although humans do this too and I've also done this without realizing it, only noticed when I was trying to move a file bigger than few kilobytes.