How pages are built

1. Split. System prompt, instructions and the latest turns stay as text. Older history, character sheets and lore become pages. (Drawing instructions as well made the model treat them as reference material instead of rules.)
2. Render. Text is laid out densely on fixed-size pages: square 1932 px PNGs for Claude, which bills images by area, and vector PDF pages for Gemini, which bills a PDF page at a flat rate.
3. Append. A full page never changes. New turns only add pages at the end, so the prompt prefix stays byte-identical from one turn to the next and prompt caching keeps working.

No embeddings, no vector store, no extra model calls. It runs in your own process right before the normal API request.