Last month I tracked Claude Code and Codex pass rates for 95 days. The question I got most in response was not about quality at all. It was "what does this actually cost you?"
Fair question. Claude Code is an agentic tool, not a chat window. One request from you can trigger dozens of model calls, and every call re-sends the entire growing conversation as input tokens. Input volume, not output, drives the bill. Output is usually a rounding error.
So I sat down and did the session math properly. Here it is.
Where the tokens actually go
System prompt and tool definitions: roughly 15 to 20K tokens, re-sent with every single model call.
