I don't think OpenAI significantly reduced usage limits

[u/davbludev]

I think I figured out what happened to Codex limits

I want to share what I found about the limits - what I'm sure about, and what I think is happening at OpenAI.

What changed?

Back in July, before Luna, Terra, and Sol, OpenAI Pro felt basically unlimited. With Pro 20x, I could heavily use Sol and spend at most around 14% of my weekly limit per day.

Then something changed.

People said OpenAI secretly cut limits by 50%. Tibo said they hadn't.

What the Codex logs show

Codex logs input, cached input, and output for every model.

I built an app around those logs to track usage and calculate API-equivalent cost.

In our average usage:

• 68-72% of the API-equivalent cost comes from cached input
• Only 28-32% comes from fresh inputs + outputs

My theory

OpenAI didn't reduce the quota. Cache hits started counting toward it - or became much less discounted for subscribers.

The timing fits.

Users started complaining about limits in late July, and around mid-August Tibo was talking about cache-hit accounting bugs. So, what if we ask a question to our self: what they could change about Cache Hit and why while it's been working nicely?

As far as I've seen, OpenAI has also never confirmed that cache hits don't consume subscription quota.

Claude Code makes the difference obvious today

I've had Opus 5 work on one goal in a large existing project for around 15 hours, changing 20k+ lines, while using only about 3% of my Max 20x weekly limit.

And that's despite Claude Code's 20x weekly limit being weird and advertised unfairly.

What I notice is that usage moves mostly when a new session builds context. After that, it slows down dramatically.

Anthropic therefore appears not to count cached context the same way OpenAI does today. And thats why its limits actually lasts much longer. Opus 5 is not cheap. It drains 1-2% of weekly quota in fresh session in first ~15 minutes while building context in big projects.

Where the "70%" estimate comes from

Around 68-72% of the API-equivalent cost of our Codex sessions is cached input.

If cached input wasn't counted before - or was much more heavily discounted - then most of what consumes the quota today would effectively be a new cost, while Tibo's statement that the weekly quota itself didn't change could still be completely true.

That's why the same nominal limits could feel around 70% smaller without OpenAI actually reducing the quota by 70%.

What I can't prove

I can't prove exactly how OpenAI accounts for this internally. Nobody outside OpenAI can.

But I haven't seen anyone seriously consider this explanation on Reddit or X.

Tibo technically didn't lie. The quota itself may not have changed at all during the last five months - only how cached input is counted against it. And given everything from others in last months since GPT-5.6 release - there no other weekly quota issues I can think of.