# Usage validation

> Enforce count relationships, null handling, and checked arithmetic at the usage boundary.

- Path: `Guides > Inference > Usage > Usage validation`
- Human: https://looprig.com/docs/guides/inference/usage/validation
- Machine index: https://looprig.com/llms.txt

Usage normalization rejects unrepresentable provider values before a response
or terminal stream result is published.

## Rules

`usagenorm.Count` accepts bounded nonnegative integer values and distinguishes
missing/null fields from zero. Normalization rejects negative, fractional, and
out-of-range values. Cache-read and cache-creation subsets must not exceed
gross input. `content.Usage.Validate` is deprecated and no decoder calls it:
the reasoning-within-output relationship is now the predicate
`content.Usage.ReasoningWithinOutput`, and nothing gates on it.
`ContextTokens`, `TotalTokens`, and `Add` use checked addition.

## Errors

```go
var err error // set by a codec decoder
var normalizeErr *inferenceusage.UsageNormalizationError
if errors.As(err, &normalizeErr) {
	fmt.Println(normalizeErr.Field, normalizeErr.Reason)
}
```

No raw provider body or model output is stored in these errors. A decoder
returns the error and does not publish a partially normalized value.

## Source and proof

- [`internal/usagenorm/count.go`](https://github.com/looprig/inference/blob/v0.12.0/internal/usagenorm/count.go)
- [`internal/usagenorm/field.go`](https://github.com/looprig/inference/blob/v0.12.0/internal/usagenorm/field.go)
- [`usage/errors.go`](https://github.com/looprig/inference/blob/v0.12.0/usage/errors.go)
- [`core/content/usage.go`](https://github.com/looprig/core/blob/v0.6.0/content/usage.go)

Run `go test ./internal/usagenorm ./usage` and `go test` in the core module for domain validation.