u/BigFuckingStonk

I had a hard time finding this searching through the pisspool of self promo and ai written posts so here it is for Linux or Windows :

Linux:

1. Open Terminal.
2. Check that the Codex folder exists:

​

ls -la ~/.codex

1. Check that this file exists:

​

ls -l ~/.codex/models_cache.json

1. Make a copy so Codex does not overwrite your edited file:

​

cp ~/.codex/models_cache.json ~/.codex/models_luna_v2.json

1. Open the copied file:

​

nano ~/.codex/models_luna_v2.json

1. In Nano, press:

​

Ctrl+W

then type:

gpt-5.6-luna

1. Inside the Luna section, find:

​

"multi_agent_version": "v1"

Change it to:

"multi_agent_version": "v2"

1. Save the file:

​

Ctrl+O
Enter
Ctrl+X

1. Get the full path of the file:

​

realpath ~/.codex/models_luna_v2.json

It will look like:

/home/yourname/.codex/models_luna_v2.json

1. Open Codex's configuration file:

​

nano ~/.codex/config.toml

1. Add this line, using your real path:

​

model_catalog_json = "/home/yourname/.codex/models_luna_v2.json"

1. Save:

​

Ctrl+O
Enter
Ctrl+X

1. Fully close Codex and VS Code.
2. Reopen VS Code and Codex.
3. Check whether Luna is now available as an agent/subagent model.

Windows:

1. Open File Explorer.
2. In the address bar, type:

​

%USERPROFILE%\.codex

and press Enter.

This usually opens something like:

C:\Users\YourName\.codex

1. Find:

​

models_cache.json

1. Copy it.
2. Rename the copy to:

​

models_luna_v2.json

1. Open models_luna_v2.json with VS Code or Notepad.
2. Search for:

​

gpt-5.6-luna

1. Inside the Luna object, find:

​

"multi_agent_version": "v1"

Change it to:

"multi_agent_version": "v2"

1. Save the file.
2. Copy the full path. It will usually be something like:

​

C:\Users\YourName\.codex\models_luna_v2.json

1. In the same .codex folder, open:

​

config.toml

1. Add this line:

​

model_catalog_json = "C:\\Users\\YourName\\.codex\\models_luna_v2.json"

Using doubled backslashes is the safest TOML form on Windows.

Alternatively, forward slashes usually work too:

model_catalog_json = "C:/Users/YourName/.codex/models_luna_v2.json"

1. Save config.toml.
2. Fully close VS Code and Codex.
3. Reopen VS Code and Codex.
4. Check whether Luna is now available as the agent model.

Important: edit the copied file, not models_cache.json itself. Codex can refresh the cache and overwrite your changes.

THERE