"Apply to Specific Files" rules not being applied for GPT-5.4

[Kossuranta (Anssi Koskenranta)]

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

I have written rules for backend that should be applied for .cs files, but they are not working and agent tells me that they don’t have that file in context at all after editing multiple C# files. Rules with alwaysApply: true work just fine and agent has them in context.

Opus 4.6 and Composer 1.5 did read the rule file, but GPT-5.4 keeps ignoring it

File location .cursor/rules/backend.md and it’s visible in Cursor settings menu

---
description: Backend C#/.NET conventions - build/test commands, C# style, prohibited actions, safe change practices.
globs: **/*.cs
alwaysApply: false
---

Steps to Reproduce

1. Select GPT-5.4 as agent (tested with High and Extra High versions too)
2. Create rule that’s set to apply for specific files
3. Set globs to **/*.cs
4. Tell agent to create or edit C# file
5. Ask agent if it has the rule in context

Expected Behavior

Rule file for the set filetype being edited should always be read before editing or creating files

Screenshots / Screen Recordings

Operating System

Windows 10/11

Version Information

Version: 2.6.18 (system setup)
VSCode Version: 1.105.1
Commit: 68fbec5aed9da587d1c6a64172792f505bafa250
Date: 2026-03-10T02:01:17.430Z
Build Type: Stable
Release Track: Default
Electron: 39.6.0
Chromium: 142.0.7444.265
Node.js: 22.22.0
V8: 14.2.231.22-electron.0
OS: Windows_NT x64 10.0.26100

For AI issues: which model did you use?

Model name: GPT-5.4

Does this stop you from using Cursor

No - Cursor works, but with this issue

[deanrie]

Hey, thanks for the detailed report and the screenshot. It clearly shows the rule file isn’t being loaded into context.

This looks like a bug in how glob-scoped rules are injected for GPT-5.4 specifically. The fact that Opus 4.6 and Composer 1.5 pick up the same rule fine confirms it’s model-specific.

As a workaround for now, you can temporarily set alwaysApply: true for this rule. It’s not ideal since it’ll be included in all chats, but it should make sure GPT-5.4 actually reads it until this is fixed.

Let me know if you need anything else.