Show ramp crypto amounts at the asset's own decimal precision

CHANGELOG.md

@@ -18,6 +18,7 @@
 - changed: (ARRR) Pirate Chain wallets run on `react-native-pirate-wallet` 0.3.4, replacing `react-native-piratechain`
 - changed: Balance-effect checks and the login FIO refresh wait for engine readiness on cache-emitted wallets
 - changed: Opening any wallet-scoped scene asks the core to prioritize that wallet's engine startup in the post-login queue.
+- changed: Buy/sell crypto amount field shows up to nine decimals, matching the asset's precision, instead of six
 - fixed: A send whose funds are not spendable yet says so instead of reporting a network error
 - fixed: Auto-login starting two competing accounts when both `YOLO_PASSWORD` and `YOLO_PIN` are set, and attempting a login when either is set to an empty string.
 - fixed: Auto-login never running on a device with no accounts, since the welcome carousel took priority over the login scene that owns it.

src/components/scenes/RampCreateScene.tsx

@@ -87,6 +87,13 @@ import { EdgeText } from '../themed/EdgeText'
 import { FilledTextInput } from '../themed/FilledTextInput'
 import { RampRegionSelect } from './RampCreateScene/RampRegionSelect'
 
+/**
+ * Upper bound on the decimals the crypto amount field renders, for assets whose
+ * own precision goes beyond what a ramp quote can express. See
+ * `cryptoMaxDecimals`.
+ */
+const MAX_CRYPTO_ENTRY_DECIMALS = 9
+
 export interface RampCreateParams {
   forcedWalletResult?: WalletListWalletResult
   regionCode?: string
@@ -617,6 +624,21 @@ export const RampCreateScene: React.FC<Props> = (props: Props) => {
     denomination
   ])
 
+  // How many decimals the crypto field renders. Providers quote each asset at
+  // its own precision and change it over time (Moonpay moves BTC 5 -> 8 and
+  // ETH/SOL to 9 decimals on the buy flow in September 2026), so this follows
+  // the asset instead of assuming a count. The 9-decimal ceiling keeps the
+  // field readable for high-precision assets such as ETH, whose 18 decimals
+  // would expose the rounding noise of the float exchange rate that
+  // `displayCryptoAmount` divides by while the user types a fiat amount.
+  const cryptoMaxDecimals = React.useMemo(() => {
+    if (denomination == null) return MAX_CRYPTO_ENTRY_DECIMALS
+    return Math.min(
+      mulToPrecision(denomination.multiplier),
+      MAX_CRYPTO_ENTRY_DECIMALS
+    )
+  }, [denomination])
+
   // Log the quote event only when the scene is focused
   useFocusEffect(() => {
     dispatch(logEvent(direction === 'buy' ? 'Buy_Quote' : 'Sell_Quote'))
@@ -1129,7 +1151,7 @@ export const RampCreateScene: React.FC<Props> = (props: Props) => {
                 placeholder={cryptoAmountPlaceholder}
                 keyboardType="decimal-pad"
                 numeric
-                maxDecimals={6}
+                maxDecimals={cryptoMaxDecimals}
                 returnKeyType="done"
                 showSpinner={isFetchingQuotes && lastUsedInput === 'fiat'}
                 disabled={cryptoInputDisabled}