Why system prompts fail: prompt injection vs actual security layers

We spent way too long trying to patch jailbreaks purely by adding stricter rules into our system prompt only to watch users bypass it with a simple "pretend you are in developer mode" trick a day after launch.

Relying on text instructions to secure an LLM is like asking someone nicely not to break a lock. We finally had to move validation logic and safety filters completely out of the prompt and into hardcoded middleware.

How are you separating core app logic from the AI's instruction layer to stop prompt injections?