What common mistake do developers make with Config directory, why does the mistake cause problems, and what is the safer approach?

What common mistake do developers make with Config directory, why does the mistake cause problems, and what is the safer approach? One recurring problem with config directory is applying it without understanding the boundary it protects. Putting application secrets or manually edited runtime files inside source directories instead of using environment configuration and framework-managed storage. In addition, The config directory contains application configuration files that read values and expose settings to the framework. Safer engineering approach: keep the responsibility in the correct layer, use the framework's supported API, validate and authorize inputs, avoid hidden side effects, and verify the behavior with tests.