It helps that Codex is so much slower than Anthropic models, a 4.5 hours Codex session might as well be a 2 hour Claude Code one. I use both extensively FWIW.
It really depends. When building a lot of new features it happens quite fast. With some attention to context length I was often able to go for over an hour on the 20$ claude plan.
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.
I find that I use it on isolated changes where Claude doesn’t really need to access a ton of files to figure out what to do and I can easily use it without hitting limits. The only time I hit the 4-5 hour limit is when I’m going nuts on a prototype idea and vibe coding absolutely everything, and usually when I hit the limit, I’m pretty mentally spent anyway so I use it as a sign to go do something else. I suppose everyone has different styles and different codebases, but for me I can pretty easily stay under the limit without that it’s hard to justify $100 or $200 a month.
With Codex it only happened to me once in my 4.5hr session here: https://simonwillison.net/2025/Dec/15/porting-justhtml/
Claude Code is a whole lot less generous though.
For sure. On one project I kept using codex just to see where the wall was. Took a long time.
It helps that Codex is so much slower than Anthropic models, a 4.5 hours Codex session might as well be a 2 hour Claude Code one. I use both extensively FWIW.
It really depends. When building a lot of new features it happens quite fast. With some attention to context length I was often able to go for over an hour on the 20$ claude plan.
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.
I find that I use it on isolated changes where Claude doesn’t really need to access a ton of files to figure out what to do and I can easily use it without hitting limits. The only time I hit the 4-5 hour limit is when I’m going nuts on a prototype idea and vibe coding absolutely everything, and usually when I hit the limit, I’m pretty mentally spent anyway so I use it as a sign to go do something else. I suppose everyone has different styles and different codebases, but for me I can pretty easily stay under the limit without that it’s hard to justify $100 or $200 a month.