gpt-5-mini is not persistent set for future sessions

[luis-baquero-dnv]

Describe the bug

Model selection not persisted: after running /model gpt-5-mini, the selection is active for the
current session, but after closing and reopening the Copilot CL,I the model reverts to claude-sonnet-4.6 instead of
persisting "gpt-5-mini".has reverted; expected behavior is that the chosen model persists across sessions; it occurs every time.

Affected version

GitHub Copilot CLI 0.0.422.

Steps to reproduce the behavior

(1) run "/model gpt-5-mini"
(2) close the terminal
(3) reopen Copilot

and observe that the model is changed and not gpt-5-miniany longer

Expected behavior

If the user previously selected the gpt-5-mini model using the coman /model command, then for all future Copilot CLI sessions, gpt-5-mini should be set as the default model unless changed again. This ensures continuity in model selection based on the user's last explicit choice.

Additional context

No response

[luis-baquero-dnv]

I created a .bat file to launch Copilot with the gpt-5-mini model, so I don't have to switch to a free model manually

@echo off
powershell -NoProfile -ExecutionPolicy Bypass -NoExit -Command "copilot -i '/model gpt-5-mini'"

[tangrufus]

Encountering the same issue.

Steps:

1. add "model": "gpt-5-mini" in ~/.copilot/config.json.
2. run $ copilot (without --model gpt-5-mini)

Expected Behaviors:

1. Boot with gpt-5-mini
2. ~/.copilot/config.json remains unchanged

Actual Behaviors:

1. Boot with Claude Sonnet 4.6
2. ~/.copilot/config.json got reverted. model is removed.

Copilot itself said it's probably because of some sanitation and/or validation, but provided no solutions.

[cyberjob001]

Encountering the same issue.

added "model": "gpt-5-mini" in ~/.copilot/config.json.
start copilot (without --model gpt-5-mini)

Expected Behaviors:
Boot with gpt-5-mini
~/.copilot/config.json remains unchanged

Actual Behaviors:
Boot with Claude Sonnet 4.6
~/.copilot/config.json is auto updated and the model is being removed.

[kennethk-corp]

Some models persist. Some don't. For instance, if you just type copilot and then within the cli type /model and set to opus 4.6, exit and come back in, it will be persisted. same with opus 4.5. But if you do this with sonnet 4.5, or gpt-5 mini, it won't. I didn't try all of them. after you exit, you can actually verify the .copilot\config.json file that it did get persisted. But once you run copilot, it changes it.

I could just type: copilot --model gpt-5-mini to get the model i want.
I can also set the model in an environment variable:
set COPILOT_MODEL=gpt-5-mini
before calling copilot.

This is a bug because the documentation clearly states you should be able to edit the config file and set the default model.

Design decision:
I don't know if the requirement is clear as to whether a command such as copilot --model gpt-5-mini should set the default in the config file or not. My thinking is that it shouldn't because command-line options should be treated as "overrides", where as setting it from within the cli using /model one may want to be persisted.

Alternatively, the design can be that /model from within the cli is for that session only, and if you want the default changed you have to edit the config file directly. I didn't come across anything in the docs on which it is. I'll let smarter those smarter than me decide, but it should be consistent.

[oceanlongnion]

+1 on this — same problem here, but with Opus:

• I select claude-opus-4.7 via /model (or the picker in VS Code's Copilot CLI integration)
• Within the same conversation, it sometimes silently reverts to claude-sonnet-4.6 mid-session (not just across restarts)
• Next time I look, I'm back on Sonnet and have to re-select Opus

Repro: pick Opus, do a few turns, occasionally a system note appears that the model changed. I'd expect my explicit /model choice to persist for the duration of the session at minimum and across sessions ideally.

Version: GitHub Copilot CLI 1.0.49 (VS Code integration). Would love to see this fixed — having to re-pick the model repeatedly is friction.