Rider is unable to debug an Unreal Engine project after attachment

Problem

When attaching Rider debugger to a running Unreal Engine project on Windows, Rider is unable to resolve and trigger breakpoints in a game/plugin/module.

Cause

Projects targeting Unreal Engine can often have over 500 modules. By default, Windows limits debuggers to loading only the first 500 modules.

Resolution

Module limit can be increased using the DebuggerMaxModuleMsgs registry key. The key can be added manually via Registry Editor or via the .reg file.

The following steps describe how to add a registry key manually:

1. Open Registry Editor (with administrator privileges)
2. Find and select HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager node
3. Right-click on the Session Manager node or the right pane of Registry Editor and use New->DWORD (32-bit) Value
4. Name the keyDebuggerMaxModuleMsgs
5. Modify the value (double-click / use Enter / right-click and use Modify)
6. Set the value to 2048 (decimal) or higher
7. Reboot the system for changes to take effect

Alternatively, a registry key can be imported via the registry file:

1. Create a file with a .reg extension and the following content (DebuggerMaxModuleMsgs is set to 5120 in this example):

   Windows Registry Editor Version 5.00
   
   [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager]
   "DebuggerMaxModuleMsgs"=dword:00001400
   

2. Open Registry Editor (with administrator privileges)

3. Use File->Import to import the .reg file

4. Reboot the system

A sample registry file can be found in the attachment.