Every hour on the invoice traces back to a specific work session, and the method was written down before anyone asked. That is what makes it hold up when someone does.
Context
When agents write the code, hours worked stops being obvious. The engineer steers while the machines produce. Months of consulting work needed a defensible answer to a simple question. How much time was actually spent?
The problem
Reconstruct billable hours after the fact, at audit grade, in a way both sides of the invoice can trust, with every number traceable to evidence.
Key decisions
Hours come from the agent session history, with any gap over 45 minutes removed. Where a session no longer exists, the commit history fills in. Time is only ever subtracted, never added, so the count can only come out low. The result was checked against a separate measure built from version-control activity, which came out higher and confirmed the bias was safe. The numbers ship with the method written out and the likely objections answered in advance.
What this demonstrates
The same habit applied to billing as to software. Nothing runs on vibes, and every number traces back to where it came from. It was built to survive a client who disputes it.
Python · Agent session logs · Git history analysis · CSV