# Spot-check every background number

Any aggregate an agent reports is a lead, not a fact, until a fast foreground check reproduces it. Pick one number and re-derive it.

From the [Tips & tricks](../index.md#tips) section of [The Muse Field Guide](../index.md).

## The move

Any aggregate an agent reports from a background process is a lead, not a fact, until a fast foreground check reproduces it.

## When to use it

For every summary, census, and digest the agent hands you. Pick one number, ask how it was produced, and have it re-derived in front of you. The habit is cheap, and it catches what confident formatting hides.

## Steps

1. Pick the load-bearing number in the report.
2. Ask for its source and method.
3. Re-derive it once, in the foreground, from the source.
4. Only then let the rest of the report stand on it.

## The gotcha

Long outputs get truncated and misread, and a fluent report formats a guess exactly like a measurement. The formatting carries no signal about which one you are holding.

## Where this came from

In one shipping session the agent misread truncated output, deleted a live snapshot, and quoted deployment identifiers that did not exist: the fourth fabricated identifier of that session. Corrections came from the on-disk logs, not the reports.

Deep dive: [Practices and tips: the resource core](../deep-dives/practices.md)

Related resources: [Verify uptake by claims, not status](verify-uptake-by-claims.md), [Done means verified live](done-means-verified-live.md), [Publish numbers with a source and a verified date](verdict-facts-with-dates.md)

Canonical page: https://www.niclydon.io/muse/items/spot-check-background-numbers.html