A model can produce a convincing patch and still miss the reason a bug happens. The useful test for a new coding model is whether it can follow the behavior across files, make a targeted change and give a reviewer enough evidence to check it.
What changed in Copilot
GitHub announced Claude Fable 5.2 for eligible Copilot plans. The rollout is gradual, and organizations may need their administrator to enable it. GitHub also describes default data retention and a separate option for some eligible enterprise customers. Check your organization’s policy and the settings for this specific model before using it with private code.
Run the same small task twice
Choose a bug with a reproducible failure in a test repository or a branch approved for evaluation. Ask your current model and the new one to explain the failure, make a minimal patch and run the same targeted test. Review which files each model touched and whether either changed behavior outside the task.
Record the time you spent checking the result, including any fixes you made to the patch. A longer response or a larger patch can add review work even when the first draft arrives quickly.