Billing Issue: Claude 4 Sonnet charging but using Claude 3.5 Sonnet

[kotochern]

Describe the Bug

I’ve noticed a billing discrepancy with the Claude 4 Sonnet model.

When I select Claude 4 Sonnet in chat, the responses I receive appear to be generated by Claude 3.5 Sonnet, not Claude 4. I explicitly ask the model to indicate which version is actually responding (in brackets), and it consistently replies that it’s Claude 3.5 Sonnet.

Despite this, in the dashboard usage logs, I am being charged at the rate for Claude 4 Sonnet.

I also asked the assistant directly what model is being used, and it confirmed that it’s Claude 3.5 Sonnet.

Can you please clarify:
1. Why this fallback is happening?
2. Why I’m being billed for Claude 4 Sonnet if it’s not what’s responding?
3. What can be done to correct this?

Steps to Reproduce

I dont know

Screenshots / Screen Recordings

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.2.4 (Universal)
VSCode Version: 1.99.3
Commit: a8e95743c5268be73767c46944a71f4465d05c90
Date: 2025-07-10T16:55:16.443Z
Electron: 34.5.1
Chromium: 132.0.6834.210
Node.js: 20.19.0
V8: 13.2.152.41-electron.0
OS: Darwin arm64 24.5.0

Does this stop you from using Cursor

No - Cursor works, but with this issue

[condor]

Hi @kotochern and welcome to Cursor Forum.

Thank you for your report and your concern about model usage.

When you select a specific model, your request gets passed to AI provider using that model only. We has checked this several times and there is no routing issue to wrong models.

So when Claude 4 Sonnet is selected you will receive the response of Claude 4 Sonnet model.

Please note following:

• Anthropic models are trained with the name “Claude” only.
• Claude 4 models were trained on data that contained info of Claude 3.5 Sonnet.
• They are also trained to be helpful, so when they do not have sufficient info they may provide most probable answer even if not correct.

I’ve tested this several times, others have checked it as well with Anthropic Console and you can test it with their API. In about 30% of cases the AI answers wrong.

Claude 4 is reporting as Claude 3.5

Models are never aware of themselves as the data they are trained on doesn’t mention them - a bit of a catch-22! “Claude 4” is not a concept on the internet when they train the model, so it’s not aware of it’s own existence, and therefore falls back to saying it is Claude 3.5, as that is a model it is aware of from it’s training data. Rules may fix this, but it’s likely not worth adding a rule just to get it to state it’s real name - you are always talking to the model you pick in Cursor!

Claude 4 Sonnet UI Mislabeling or Misrouting to Claude 3.5 Sonnet

I just checked this in the Anthropic console and got these responses. [image] [image]

Strange name of the model Claude Sonnet 4

Its pretty clear from Anthropics own Console what info models have. Any non-API 3rd party tools have system prompts which has impact on responses. [image] [image] I have posted tests of various models in many threads here and will leave it at that, this has been officially addressed by Cursor Team members in several threads as well. If you have clear info there is an issue with any model please create a full Bug Report with a Request ID that has privacy disabled so the Cursor Team can revi…

[kotochern]

1. The billing error is obvious to me, at the very least based on the screenshot below.

It shows the last four usage records for the GPT-4.1 model:

• Two of them consumed over 200,000 tokens before I restarted Cursor — when the issue was happening.

  (In the chat, the model explicitly said it was Claude 3.5, not GPT-4.1.)

• The other two consumed around 17,000 tokens after I restarted Cursor — when the issue went away.

The complexity of all four prompts was nearly the same. Normally, GPT-4.1 responses cost around 20,000 tokens, so there is a clear 10x discrepancy here for equivalent prompts.

2. After restarting Cursor, the model now correctly displays the actual name for all requests — whether I use Claude 3.5 or Claude 4 in chat.

However, even when I selected GPT-4.1, the model was responding that it was Claude 3.5 — which clearly shouldn’t happen.

Your earlier statement that “the model

doesn’t know which one it is” doesn’t match my experience.

If that were true, why is it now accurately telling me which model is responding?

[condor]

A model that is not Claude 3.5 Sonnet can not tell you ‘accurately’ that it is Claude 3.5 Sonnet.

Could you post a Request ID with privacy disabled so we can look into the details of a request which claims to be a different model? Cursor – Getting a Request ID