Describe the Bug
I usually have multiple agent tabs going. One of them is often a research tab, where I’ll have background research going on a given topic. I had one of these running for a while, as I was working in another chat tab. I’ve been using GPT-5 for everything lately since it was free, and I wanted to give it a thorough review. When I returned to my research chat tab, despite referencing multiple @Docs I had indexed, GPT-5 was NOT using ANY of the indexed docs. Turned out, it had been searching the web, searching the web, thinking, searching the web, over and over and over, for a good while, and had NOT found what I’d asked it to find, even though I know for a fact it was in the docs I had indexed. I tried to get it to use the docs, but it simply would not…so it appears there is a bug with GPT-5 with regards to not using locally indexed @Docs from Cursor.
I switched to Gemini 2.5, using the exact same prompt, and it instantly responded with the condensed knowledge I had expected GPT-5 to provide, thanks to actually using the @Docs indexed in Cursor. No web searches, no latency, the response was instant.
Steps to Reproduce
Start a new agent chat.
Use a GPT-5 model.
Ask it a question with references to relevant indexed @Docs.
Weep at the excessive use of web searches that fail to find any relevant information…?
Expected Behavior
Repeat steps to reproduce, replace weeping with joyous celebration at the instantaneous response of condensed and targeted knowledge exactly meeting your needs. 
Operating System
MacOS
Current Cursor Version (Menu → About Cursor → Copy)
Version: 1.4.3 (Universal)
VSCode Version: 1.99.3
Commit: e50823e9ded15fddfd743c7122b4724130c25df0
Date: 2025-08-08T17:34:53.060Z
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