> If the Model makes repeated mistakes on the same subject matter, you can update your agent.md file ...

That's all just prompting.

> How do you think models are created? They are trained on feedback and learn.

No one is post training models on a single mistake. At least I have not seen it. I also doubt it is effective. Post-training on a single failure will not meaningfully change the model. That even sidesteps the entire problem that you don't even have access to models if you use a provider like anthropic/openai