Why Prompt-Only Moderation Failed in My AI Generation App

When I first added moderation to my AI generation app, I treated it as a text problem. That seemed reasonable at the time. A user sends a prompt, I check the prompt, and if it looks unsafe, I block the request before it reaches the model. That approach worked for a very short time. It stopped working the moment I supported image inputs, reference images, and multiple generation flows. At that point, I realized something important: prompt-only moderation is not really moderation. It is just one partial check inside a much larger pipeline. This post is about what changed in my backend once I accepted that. The mistake: treating moderation as a wrapper A lot of AI products start with moderation as a thin wrapper around generation: receive a prompt run a text safety check call the model provider return the result The problem is that real generation workflows are rarely that simple. Once users can upload source images, provide reference images, or switch between text-to-image and image-to-i