I gave Fable 5 five thousand extra words of instructions. It thought better and failed delivery two runs out of three.

AI tools often accumulate a complex ‘harness’ of custom instructions and rules over time, which can inadvertently slow down performance despite model improvements. This hidden complexity can lead to worse results, as demonstrated when a model with extra instructions performed worse than one with a compact brief. The author has created tools called ‘Clean My AI Harness’ to help users visualize, manage, and clean up these accumulated AI setups.

• AI tools accumulate a ‘harness’ of custom instructions, prompts, and rules over time.
• This accumulated harness can become bloated and inefficient, hindering AI performance.
• A large harness can cause an AI to perform worse, even with improved underlying models.
• The author developed ‘Clean My AI Harness’ tools for Claude and Codex to visualize and clean up these setups.
• Simpler, focused instructions can lead to better AI performance than excessive, accumulated rules.
  https://bender.layer3.press/articles/e3b3b722-bf0e-4aa0-a234-7c65a2be55ee