Bad Request Error ([invalid_argument]) in a Specific Chat — Can’t Use Claude or Other Models

[Ibrahim-Ogbadu_Abdul (Ibrahim-Ogbadu Abdulsamad)]

Describe the Bug

I’m on the Pro Plan and consistently getting this error when trying to use the Claude-4-Sonnet model (and others) but only in one specific chat.

Request ID: 72558be4-6720-4e90-ac10-962be3740b15
{“error”:“ERROR_BAD_REQUEST”,“details”:{“title”:“Bad request.”,“detail”:“Bad Request”,“isRetryable”:false,“additionalInfo”:{},“buttons”:},“isExpected”:true}
ConnectError: [invalid_argument] Error
What Works / Fails:

I can send requests in new chats — no errors.

I get the Bad Request error only in the affected chat, even when switching models (Claude, GPT-4, GPT-3.5).

Network diagnostics all pass: DNS, HTTP/2, SSL, API, Agent, etc.

What I’ve Tried:

Restarted Cursor
Switched AI models
Ran full diagnostics (all green)
Is this a known issue with corrupt chat state or message formatting? Is there a way to reset/fix the broken chat thread?

Steps to Reproduce

Open Cursor (Linux AppImage, Pro Plan).

Go to an existing chat where you previously used Claude or another agent.

Attempt to:

Use a background agent (e.g., Ask AI to summarize or explain)

Or send a prompt manually using Claude-4-Sonnet or any model

Observe the error:
Bad Request with invalid_argument (Request ID: 72558be4-6720-4e90-ac10-962be3740b15)

Create a new chat, select the same model, and send a similar request.
It works normally in the new chat — the issue only affects one or more specific chats.

Operating System

Linux

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.2.4
VSCode Version: 1.99.3
Commit: a8e95743c5268be73767c46944a71f4465d05c90
Date: 2025-07-10T16:59:43.242Z
Electron: 34.5.1
Chromium: 132.0.6834.210
Node.js: 20.19.0
V8: 13.2.152.41-electron.0
OS: Linux x64 6.14.5-300.fc42.x86_64

Does this stop you from using Cursor

Yes - Cursor is unusable

[condor (Condor (Tee))]

Hi @Ibrahim-Ogbadu_Abdul and welcome to Cursor Forum.

Thank you for the detailed bug report.

Could you please update to latest Cursor (1.3.7 at the moment) and let me know if the same issue still occurs in a new chat?

[deanrie]

Hey, it seems this chat is broken and it’s unlikely to get it working again. It looks like an error occurred when calling some tool. This happens when you switch models within the same chat session.

You can create a new chat referring to the past chat so the new chat is aware of the events. Hope this helps.