Daily metrics that cannot drift: subtract yesterday's total

Most dashboards I have seen drift, and the team cannot say when it started. The Daily Metrics automation in the software factory built in public at software-factory.dev (opens in a new tab) is built to avoid that, and the reason sits in one instruction repeated all the way through its prompt.

This automation is the part that keeps its numbers honest.

A fixed snapshot, once a day

It runs once a day. The trigger is a single cron line, 0 9 * * *, so the snapshot lands at 9am whether anyone is watching or not.

What it does is mechanical on purpose. It runs fixed commands to count lines of code, pull requests, commits, issues, tests, CI health and coverage. It writes the result into a strict JSON file where every field is named in advance. It validates that file against the schema. Then it rebuilds the full time series from every daily snapshot on disk.

The fields are not optional. Even when a count is zero, the field is still there, set to zero. A missing field is treated as a bug, not an empty day.

Deltas come from subtraction, not from date queries

Here is the detail worth copying. The daily change, the delta, is never measured with a date-filtered query. The prompt says so for pull requests and again for commits: do not use a query filtered by date. Compute the delta by subtracting yesterday’s cumulative total from today’s.

Date-filtered queries drift without any warning. Timezones, indexing lag, an issue edited after midnight, and your “merged today” count is off by two with no error fired. Subtracting two cumulative totals cannot drift that way. If yesterday’s number was right and today’s is right, the difference is right.

One method, applied the same way every day

That is the whole idea. A number you can trust does not come from a clever query. It comes from one method, applied the exact same way every day, with the previous day as the anchor.

For a team standing up its own factory, this is the unglamorous part that decides whether the dashboard is worth looking at in six months.

The automation itself: daily-metrics.yaml in the factory’s repository (opens in a new tab).

Which of your team’s daily numbers is computed a slightly different way each time you look?

Further reading

• Quality and productivity metrics →
• Agentic Software Factory: Advanced Team Training →