Amount input

An amount or count typed as a mask: only digits and separators are accepted, thousands are grouped as you type, and nothing the user typed is ever cut off silently. Component AmountInput (packages/ui/src/components/AmountInput.tsx), built on packages/ui/src/lib/number-core.ts — the same core as number editing in RecordRail. Merged to origin/main 28 September 2026 (acrm MR !4089, "fix(ui): M3 masek — částka = maska (AmountInput), tečka podle kontextu"), under the owner's binding rule of 14 Sep 2026 (.claude/rules/design-system.md §"Vstupy a mobil"): a structured value is a mask, never free text.

The value contract is the raw string -?\d*(\.\d*)? (dot decimal, no grouping) — exactly what <input type="number"> used to emit, so host calculations do not change. The formatted text (1 234,50) lives only inside the input.

When to use

• Money amounts in forms and drawers (costs, advances, benefits, budgets, prices, KPI money targets) — decimals={2} (default), unit as suffix ("Kč", "%").
• Counts (KPI calls, headcount) — decimals={0}; the field then refuses any decimal separator.
• Negative values only where the domain allows them — negative.

When not to use

• Inline table cells with their own editing model (deal detail line items) — keep the cell editor.
• Identifiers that happen to be digits (IČO, PSČ, phone) — use Masked input / Phone input.
• Read-only display of an amount — format it as text (see "Compact money" canon), not a disabled field.

Anatomy

• .acrm-inputwrap.acrm-amountwrap — the field shell; the number is right-aligned like in listings.
• input — type="text", inputMode="decimal" (or numeric for decimals={0}).
• .acrm-amount-suffix — optional muted unit at the end (aria-hidden; put the unit into the label or ariaLabel too).

Best practices

Do

• Comma is always the decimal separator; at most decimals digits after it — a further digit is simply not accepted.
• A dot is read by context (AD 28 Sep 2026): followed by exactly three digits (or groups of three) it is a thousands separator — 12.345 → 12 345, 1.234.567 → 1 234 567; followed by one or two digits it is a decimal — 12.5 shows as typed and becomes 12,5 on blur. Pasting follows the same rule (1 234,50 → 1234.50).
• Let the field keep its own draft: a host that stores minor units (haléře) does not lose a trailing 12,.
• Arrow ↑/↓ step the value like the native stepper.

Don't

• Don't truncate or round what the user typed — an invalid shape (12.3456, two commas, 1.2,5) is refused, the text stays as it was.
• Don't use type="number" — it drops grouped values (300 000) entirely.
• Don't re-format on every host render — pass the raw value back and let the field format.

Content

• Label says what and in which unit ("Částka (Kč)", "Měsíční náklad"); the unit also goes into suffix when it helps scanning.
• No placeholder amounts that look like real data; empty is empty.

Related

• Masked input, Phone input — the other structured-value masks.
• Input — plain text field.
• Record rail — number editing in the rail shares number-core (caret anchoring); amounts in the rail will take the same dot rule (wave M4b).