Long inputs often push the model beyond its effective attention capacity, even if they fit within the formal context limit.

As prompts grow, important instructions or early context lose influence. The model technically processes the input, but practical reasoning quality degrades.

The fix is to structure inputs rather than just truncate them. Summarize earlier content, chunk long documents, or use retrieval-based approaches so the model only sees relevant context.

Common mistakes:

• Feeding entire documents directly into prompts

• Assuming larger context windows solve everything

• Letting user input override system instructions

LLMs reason best with focused, curated context.