If you've spent time building with LLMs, you've hit this wall: you get your agent or workflow running, the outputs are decent, and then... they stay decent. Six months later, the same prompts produce roughly the same quality. The model hasn't gotten worse. The workflow hasn't improved.

The reason is almost always the same: you're missing Phase 4.

The pattern most AI workflows skip

Here's the loop most developers run without naming it:

Write a system prompt and user prompt (Brief)