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

What common mistake do developers make with Status codes, why does the mistake cause problems, and what is the safer approach? One recurring problem with status codes is applying it without understanding the boundary it protects. Returning HTML error pages from a JSON API without considering content negotiation and client expectations. In addition, API endpoints should return meaningful HTTP status codes that clients can interpret. 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.