Why a form-validation engine should wait for a second repeat before adding a new rule

A developer received three near-identical requests to block certain characters across different form fields, prompting a decision about whether to keep adding one-off checks or formalize a pattern. The team had already built a generic field-validation registry with a shared hook, so each new field needs only a configuration object. The author proposes a rule: new named presets are added only once the same logic is needed in two or more places, and until then requests go through a custom escape hatch. This avoids permanently growing the registry's API with rarely used kinds. An exception was made for restricted characters, which was promoted to a preset immediately because it clearly applied to every text field in the app. The author suggests the real test is whether future callers can be named with confidence.