Portway
A local proxy that cuts a coding agent's upload to the size of what changed.
A coding agent resends its whole conversation on every turn: the system prompt, every earlier message, and every tool result. Turn N is turn N-1 plus a few kilobytes, yet the entire body is uploaded again, so the upload volume of a session grows with the square of the number of turns. Portway sits between the agent and the LLM API, and with portway receive running at the other end, each request crosses the network as the difference from the previous one. On a 1 MiB context, a turn that would upload about 1 MiB uploads about 1 KiB.
The delta is a Dictionary-Compressed Zstandard frame as specified in RFC 9842, keyed by the SHA-256 of the body the receiver confirmed it stored. A lost dictionary falls back to plain zstd, a refused zstd body to an uncompressed one, and application errors are never retried. Around the compression sit model-based routing, a record of every request with its tokens and cost per model and service tier, and two live views of all of it: a terminal dashboard and a browser console.
