On a $20/mo plan doing any sort of agentic coding you'll hit the 5hr window limits in less than 20 minutes.
Claude Code is a whole lot less generous though.
I havent tried agentic coding as I havent set it up in a container yet, and not going to yolo my system (doing stuff via chat and a utility to copy and paste directories and files got me pretty far over the last year and a half).
If you're doing mostly smaller changes, you can go all day with the 20$ Claude plan without hitting the limits. Especially if you need to thoroughly review the AI changes for correctness, instead of relying on automated tests.