`op: sub`

Decrement a numeric field by a value.

Allowed phases

Phase	Status
`preflight`	✗ forbidden
`core`	✓ allowed
`side_effects`	✗ forbidden

Syntax

- op: sub
  path: /inventory/stock
  value: "event.quantity"
  cap:
    min: 0

Parameters

Field	Required	Description
`path`	yes	Numeric field path
`value`	yes	Amount to subtract
`cap`	no	`{ max: N, min: N }` — clamp result
`if_missing`	no	`create`, `fail`, or `skip`

Behavior

Same parameters as add. Use cap: { min: 0 } to prevent negatives.

See also

Operations index — all ops by phase
actions — rule structure and phases
Intents: Rules — narrative examples