Steven Chong found a pricing crack and built a tool to drive a truck through it. pxpipe is an open-source local proxy that sits between Claude Code (or Fable 5) and Anthropic’s API. It grabs the bulky, static parts of your context — system prompt, tool docs, old chat history, giant tool_results — renders them into a dense PNG, and ships the image instead of text. Recent messages still pass through as normal text.
The trick: Anthropic bills images by pixels, not by what’s written in them. A ~48,000-character system prompt costs ~25,000 tokens as text. Squeeze it onto one packed PNG and it’s ~2,700 tokens. Dense content lands ~3.1 characters per image-token versus ~1 for text. Chong’s own numbers: 59–70% savings, one demo dropping from $42.21 to $6.06.
How you plug it in
No code changes. pxpipe installs as a proxy at 127.0.0.1:47821 and transparently intercepts the /v1/messages endpoint. Point your agent at it and every request gets the image treatment automatically.
The catch
It’s lossy. The model reads pixels back with vision, so hashes, IDs, and API keys can get misread — silently, no error. Fine for verbose docs, dangerous for exact strings. That tradeoff is exactly why Hacker News can’t stop arguing about it.
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