ChatGPT Pro on web suddenly behaves like instant/low-reasoning mode, while mobile app works normally

I’m a ChatGPT Pro user and I’ve been experiencing a serious issue for almost two days.

The problem is that ChatGPT on the desktop web version suddenly behaves as if it is running in an “instant” or low-reasoning mode, even when I select the Pro / reasoning model. The replies come back almost immediately, with very little apparent reasoning, much shorter analysis, and noticeably worse quality than usual.

This is not just a subjective “answer quality” complaint. The behavior is very different from normal Pro model behavior:

  • Complex coding, analysis, or reasoning prompts are answered in only a few seconds.
  • The responses are much shorter and less structured than before.
  • The model feels like it is silently falling back to a cheaper/faster route.
  • The same account works much better on the mobile app.
  • The issue is mainly happening on desktop web in Chrome.
  • Switching VPN nodes seems to affect the behavior somewhat. The issue became worse after switching to a Japan VPN node, and improved slightly after switching back to a US node, but it has not fully recovered.

Environment:

  • Plan: ChatGPT Pro
  • Platform affected: ChatGPT web
  • Browser: Chrome on macOS
  • Mobile app: appears normal with the same account
  • Duration: almost two days

Expected behavior:

When I select a Pro / reasoning model, the web version should actually route the request to the proper Pro reasoning model and provide normal reasoning-quality responses.

Actual behavior:

The web version often replies almost instantly and the quality looks like a fallback / instant route, even though the UI still shows the Pro model. This makes the Pro subscription almost unusable for complex tasks on desktop.

I have already contacted Support, but the replies so far have been generic canned troubleshooting responses. They did not address the possibility of a model-routing, account flag, IP risk, or web-client fallback issue.

Could someone from OpenAI please check whether there is a known routing/fallback issue affecting ChatGPT Pro users on the web, especially when VPN/IP reputation or region changes are involved?

It would also be helpful if the product could clearly show whether a request is actually being served by the selected Pro reasoning model or silently routed to a lower-latency fallback.

I am experiencing the same issue. It is very clearly related to VPN use. Actually the OpenAI support bot did mention VPN and their troubleshooting questions. Some clarity and official recommendation would be nice.