Thoughtworks measures an 83 percent drop in input tokens per change after refactoring an agent-written Rust file

Sources: martinfowler.com, discussion
Summary: A Thoughtworks experiment refactored one large agent-written Rust file and measured an 83 percent drop in input tokens per change afterwards. The saving tracks the size of the largest file rather than the total line count. The evidence is one experiment on one greenfield code base, and the cost of performing the refactoring was not measured.
Why it matters: File size, not repository size, is the variable that sets the input-token cost of an agent edit, which gives a measurable reason to split agent-written modules even when total lines stay flat.