add bitcoin and usd pricing

highlight amounts over 999.999 and clamp at 9.999.999

src/components/NoteStats/ZapButton.tsx

@@ -4,6 +4,11 @@ import {
   buildOrderedZapLightningAddresses,
   recipientHasAnyPaymentOptions
 } from '@/lib/merge-payment-methods'
+import {
+  buildRecipientZapPaymentData,
+  mergeRecipientZapPaymentData,
+  type RecipientZapPaymentData
+} from '@/hooks/useRecipientAlternativePayments'
 import { getPaymentInfoFromEvent, getProfileFromEvent } from '@/lib/event-metadata'
 import { cn } from '@/lib/utils'
 import { useNoteFeedProfileContext } from '@/providers/NoteFeedProfileContext'
@@ -53,6 +58,7 @@ export function ZapButtonWithStats({ event, hideCount = false, noteStats }: ZapB
 
   const [disable, setDisable] = useState(true)
   const [canLightningZap, setCanLightningZap] = useState(false)
+  const [tipPaymentData, setTipPaymentData] = useState<RecipientZapPaymentData | null>(null)
   const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
   const isLongPressRef = useRef(false)
 
@@ -60,33 +66,49 @@ export function ZapButtonWithStats({ event, hideCount = false, noteStats }: ZapB
     (
       profile: TProfile | null,
       profileEvent: Event | null | undefined,
-      paymentInfo: ReturnType<typeof getPaymentInfoFromEvent> | null
+      paymentInfo: ReturnType<typeof getPaymentInfoFromEvent> | null,
+      forDialogPrefetch: boolean
     ) => {
-      const canTip = recipientHasAnyPaymentOptions(paymentInfo, profile, profileEvent ?? null)
+      const event = profileEvent ?? null
+      const canTip = recipientHasAnyPaymentOptions(paymentInfo, profile, event)
       setDisable(!canTip)
       setCanLightningZap(
-        buildOrderedZapLightningAddresses({ profileEvent, paymentInfo }).length > 0
+        buildOrderedZapLightningAddresses({
+          profileEvent: event,
+          profile,
+          paymentInfo
+        }).length > 0
       )
+      if (forDialogPrefetch) {
+        setTipPaymentData((prev) =>
+          mergeRecipientZapPaymentData(
+            buildRecipientZapPaymentData(paymentInfo, profile, event),
+            prev
+          )
+        )
+      }
     },
     []
   )
 
-  /** Re-enable when the feed batch loads a real profile (not a placeholder row). */
+  /** Enable zap from feed profile; seed dialog prefetch from kind 0 JSON when available. */
   useEffect(() => {
     if (isSelf) return
     if (!feedProfile || feedProfile.batchPlaceholder) return
-    applyTipAvailability(feedProfile, null, null)
+    applyTipAvailability(feedProfile, null, null, true)
   }, [isSelf, feedProfile, feedProfiles?.version, applyTipAvailability])
 
   useEffect(() => {
     if (isSelf) {
       setDisable(true)
       setCanLightningZap(false)
+      setTipPaymentData(null)
       return
     }
 
     setDisable(true)
     setCanLightningZap(false)
+    setTipPaymentData(null)
     let cancelled = false
 
     void Promise.allSettled([
@@ -110,7 +132,7 @@ export function ZapButtonWithStats({ event, hideCount = false, noteStats }: ZapB
         null
       const paymentInfo = paymentEvent ? getPaymentInfoFromEvent(paymentEvent) : null
 
-      applyTipAvailability(profile, profileEvent ?? null, paymentInfo)
+      applyTipAvailability(profile, profileEvent ?? null, paymentInfo, true)
     })
 
     return () => {
@@ -268,6 +290,7 @@ export function ZapButtonWithStats({ event, hideCount = false, noteStats }: ZapB
         }}
         pubkey={event.pubkey}
         event={event}
+        prefetchedPayment={tipPaymentData}
       />
       <TipPublicMessagePrompt
         open={tipNoticeOpen}

src/components/Profile/index.tsx

@@ -85,6 +85,7 @@ import { useCurrentRelays } from '@/providers/CurrentRelaysProvider'
 import { FAST_READ_RELAY_URLS, FAST_WRITE_RELAY_URLS } from '@/constants'
 import { nip66Service } from '@/services/nip66.service'
 import PaymentMethodsSection from '@/components/PaymentMethodsSection'
+import { buildRecipientZapPaymentData } from '@/hooks/useRecipientAlternativePayments'
 import {
   groupPaymentMethodsByDisplayType,
   mergePaymentMethods,
@@ -154,6 +155,14 @@ export default function Profile({
     [paymentInfo, profile, profileEvent]
   )
 
+  const prefetchedZapPayment = useMemo(
+    () =>
+      profile?.pubkey
+        ? buildRecipientZapPaymentData(paymentInfo, profile ?? null, profileEvent ?? null)
+        : null,
+    [paymentInfo, profile, profileEvent]
+  )
+
   const syncAuthorReplaceablesFromCache = useCallback(async (pubkey: string) => {
     try {
       const [paymentEvent, metaEvent] = await Promise.all([
@@ -624,6 +633,7 @@ export default function Profile({
               }}
               pubkey={pubkey}
               defaultLightningAddress={zapLightningDefault}
+              prefetchedPayment={prefetchedZapPayment}
             />
             <div className="flex flex-wrap justify-between items-center gap-x-4 gap-y-2 mt-2 text-sm min-w-0">
               <div className="flex flex-wrap gap-4 items-center min-w-0">

src/components/ZapDialog/ZapSatsAmountInput.tsx

@@ -0,0 +1,64 @@
+import {
+  clampZapSats,
+  formatSatsGrouped,
+  parseGroupedIntegerInput,
+  shouldHighlightLeadingSatsGroups,
+  splitSatsGroupedParts
+} from '@/lib/lightning'
+import { cn } from '@/lib/utils'
+
+const inputTypography =
+  'text-center w-full p-0 text-6xl font-bold tabular-nums tracking-tight'
+
+export default function ZapSatsAmountInput({
+  sats,
+  onSatsChange,
+  id = 'sats'
+}: {
+  sats: number
+  onSatsChange: (next: number) => void
+  id?: string
+}) {
+  const clamped = clampZapSats(sats)
+  const highlightLeading = shouldHighlightLeadingSatsGroups(clamped)
+  const parts = splitSatsGroupedParts(clamped)
+
+  return (
+    <div className="relative flex justify-center w-full max-w-xs min-h-[4.5rem] items-center">
+      <div
+        className={cn(
+          'pointer-events-none absolute inset-0 flex items-center justify-center gap-[0.2em]',
+          inputTypography
+        )}
+        aria-hidden
+      >
+        {parts.map((part, index) => (
+          <span
+            key={`${index}-${part}`}
+            className={cn(index === 0 && highlightLeading && 'text-yellow-400')}
+          >
+            {part}
+          </span>
+        ))}
+      </div>
+      <input
+        id={id}
+        inputMode="numeric"
+        value={formatSatsGrouped(clamped)}
+        onChange={(e) => {
+          onSatsChange(parseGroupedIntegerInput(e.target.value))
+        }}
+        onFocus={(e) => {
+          requestAnimationFrame(() => {
+            const val = e.target.value
+            e.target.setSelectionRange(val.length, val.length)
+          })
+        }}
+        className={cn(
+          inputTypography,
+          'relative z-10 bg-transparent text-transparent caret-foreground focus-visible:outline-none'
+        )}
+      />
+    </div>
+  )
+}

src/components/ZapDialog/index.tsx

@@ -20,6 +20,10 @@ import { Switch } from '@/components/ui/switch'
 import { useNostr } from '@/providers/NostrProvider'
 import { useScreenSize } from '@/providers/ScreenSizeProvider'
 import { useZap } from '@/providers/ZapProvider'
+import { useBtcUsdRate } from '@/hooks/useBtcUsdRate'
+import { clampZapSats, formatSatsGrouped, shouldHighlightLeadingSatsGroups } from '@/lib/lightning'
+import { formatBtcFromSats, formatUsdFromSats } from '@/lib/sats-fiat'
+import { cn } from '@/lib/utils'
 import lightning from '@/services/lightning.service'
 import noteStatsService from '@/services/note-stats.service'
 import { NostrEvent } from 'nostr-tools'
@@ -33,6 +37,7 @@ import {
 } from '@/lib/merge-payment-methods'
 import PaymentMethodsSection from '@/components/PaymentMethodsSection'
 import {
+  mergeRecipientZapPaymentData,
   useRecipientZapPaymentData,
   type RecipientZapPaymentData
 } from '@/hooks/useRecipientAlternativePayments'
@@ -44,6 +49,7 @@ import {
   SelectValue
 } from '@/components/ui/select'
 import TipPublicMessagePrompt from './TipPublicMessagePrompt'
+import ZapSatsAmountInput from './ZapSatsAmountInput'
 import UserAvatar from '../UserAvatar'
 import Username from '../Username'
 
@@ -54,7 +60,8 @@ export default function ZapDialog({
   event,
   defaultAmount,
   defaultComment,
-  defaultLightningAddress
+  defaultLightningAddress,
+  prefetchedPayment = null
 }: {
   open: boolean
   setOpen: Dispatch<SetStateAction<boolean>>
@@ -64,6 +71,8 @@ export default function ZapDialog({
   defaultComment?: string
   /** Lightning address to pre-select (e.g. from a profile payto link click). */
   defaultLightningAddress?: string | null
+  /** Profile/feed snapshot shown immediately; relay fetch while open may enrich this. */
+  prefetchedPayment?: RecipientZapPaymentData | null
 }) {
   const { t } = useTranslation()
   const { isSmallScreen } = useScreenSize()
@@ -72,16 +81,22 @@ export default function ZapDialog({
   const [tipNoticeOpen, setTipNoticeOpen] = useState(false)
   const skipTipNoticeOnCloseRef = useRef(false)
 
-  const recipientPayment = useRecipientZapPaymentData(pubkey, open)
+  const fetchedPayment = useRecipientZapPaymentData(pubkey, open)
+  const recipientPayment = useMemo(
+    () => mergeRecipientZapPaymentData(prefetchedPayment, fetchedPayment),
+    [prefetchedPayment, fetchedPayment]
+  )
   const lightningAddressOptions = useMemo(
     () =>
       buildOrderedZapLightningAddresses({
         profileEvent: recipientPayment.profileEvent,
+        profile: recipientPayment.profile,
         paymentInfo: recipientPayment.paymentInfo,
         preferredAddress: defaultLightningAddress
       }),
     [
       recipientPayment.profileEvent,
+      recipientPayment.profile,
       recipientPayment.paymentInfo,
       defaultLightningAddress
     ]
@@ -245,10 +260,15 @@ function ZapDialogContent({
   const { pubkey } = useNostr()
   const { defaultZapSats, defaultZapComment, includePublicZapReceipt, updateIncludePublicZapReceipt } =
     useZap()
-  const [sats, setSats] = useState(defaultAmount ?? defaultZapSats)
+  const [sats, setSats] = useState(() => clampZapSats(defaultAmount ?? defaultZapSats))
   const [comment, setComment] = useState(defaultComment ?? defaultZapComment)
   const [zapping, setZapping] = useState(false)
   const [selectedLightning, setSelectedLightning] = useState('')
+  const btcUsd = useBtcUsdRate()
+  const clampedSats = clampZapSats(sats)
+  const highlightLargeAmount = shouldHighlightLeadingSatsGroups(clampedSats)
+  const btcEquivalent = useMemo(() => formatBtcFromSats(clampedSats), [clampedSats])
+  const usdEquivalent = useMemo(() => formatUsdFromSats(clampedSats, btcUsd), [clampedSats, btcUsd])
 
   const { alternativeGroups } = recipientPayment
 
@@ -261,9 +281,9 @@ function ZapDialogContent({
     () =>
       prepareZapDialogAlternativePayments(
         alternativeGroups,
-        canLightningZap ? sats : ZAP_HIDE_BITCOIN_ALTS_MAX_SATS
+        canLightningZap ? clampedSats : ZAP_HIDE_BITCOIN_ALTS_MAX_SATS
       ),
-    [alternativeGroups, sats, canLightningZap]
+    [alternativeGroups, clampedSats, canLightningZap]
   )
 
   const hasAlternativePayments = zapAlternativePayments.groups.length > 0
@@ -315,7 +335,7 @@ function ZapDialogContent({
       const zapResult = await lightning.zap(
         pubkey,
         event ?? recipient,
-        sats,
+        clampedSats,
         comment,
         closeZapDialog,
         includePublicZapReceipt,
@@ -329,7 +349,7 @@ function ZapDialogContent({
         return
       }
       if (event) {
-        noteStatsService.addZap(pubkey, event.id, zapResult.invoice, sats, comment)
+        noteStatsService.addZap(pubkey, event.id, zapResult.invoice, clampedSats, comment)
       }
     } catch (error) {
       toast.error(`${t('Zap failed')}: ${(error as Error).message}`)
@@ -370,38 +390,35 @@ function ZapDialogContent({
       <div className="space-y-4">
         {/* Sats slider or input */}
         <div className="flex flex-col items-center px-4">
-          <div className="flex justify-center w-full max-w-xs">
-            <input
-              id="sats"
-              value={sats}
-              onChange={(e) => {
-                setSats((pre) => {
-                  if (e.target.value === '') {
-                    return 0
-                  }
-                  let num = parseInt(e.target.value, 10)
-                  if (isNaN(num) || num < 0) {
-                    num = pre
-                  }
-                  return num
-                })
-              }}
-              onFocus={(e) => {
-                requestAnimationFrame(() => {
-                  const val = e.target.value
-                  e.target.setSelectionRange(val.length, val.length)
-                })
-              }}
-              className="bg-transparent text-center w-full p-0 focus-visible:outline-none text-6xl font-bold"
-            />
+          <div
+            className="mb-1 flex min-h-[1.125rem] flex-wrap items-center justify-center gap-x-2 gap-y-0.5 text-xs text-muted-foreground tabular-nums"
+            aria-live="polite"
+          >
+            <span
+              className={cn(
+                highlightLargeAmount &&
+                  'rounded-md bg-yellow-400/25 px-2 py-0.5 font-semibold text-yellow-200 shadow-[0_0_12px_rgba(250,204,21,0.45)] ring-1 ring-yellow-400/70'
+              )}
+            >
+              {btcEquivalent}
+            </span>
+            {usdEquivalent != null ? (
+              <>
+                <span className="text-muted-foreground/40" aria-hidden>
+                  ·
+                </span>
+                <span>{usdEquivalent}</span>
+              </>
+            ) : null}
           </div>
+          <ZapSatsAmountInput sats={sats} onSatsChange={setSats} />
           <Label htmlFor="sats">{t('Sats')}</Label>
         </div>
 
         {/* Preset sats buttons */}
         <div className="grid grid-cols-6 gap-2 px-4">
           {presetAmounts.map(({ display, val }) => (
-            <Button variant="secondary" key={val} onClick={() => setSats(val)}>
+            <Button variant="secondary" key={val} onClick={() => setSats(clampZapSats(val))}>
               {display}
             </Button>
           ))}
@@ -433,38 +450,56 @@ function ZapDialogContent({
         </div>
 
         <div className="min-w-0 space-y-1.5">
-          <Label htmlFor="zap-lightning-address">{t('Lightning address for zap')}</Label>
-          <Select value={selectedLightning} onValueChange={setSelectedLightning}>
-            <SelectTrigger id="zap-lightning-address" className="min-w-0 gap-2">
-              <SelectValue placeholder={t('Select lightning address')}>
-                {selectedLightning ? (
-                  <span className="flex min-w-0 items-center gap-2">
-                    <span className="shrink-0 text-lg leading-none text-yellow-400" aria-hidden>
-                      ⚡
+          <Label
+            htmlFor={
+              lightningAddressOptions.length > 1 ? 'zap-lightning-address' : undefined
+            }
+          >
+            {t('Lightning address for zap')}
+          </Label>
+          {lightningAddressOptions.length === 1 ? (
+            <p
+              id="zap-lightning-address"
+              className="flex min-w-0 items-center gap-2 text-sm text-muted-foreground"
+            >
+              <span className="shrink-0 text-lg leading-none text-yellow-400" aria-hidden>
+                ⚡
+              </span>
+              <span className="min-w-0 break-all">{lightningAddressOptions[0]}</span>
+            </p>
+          ) : (
+            <Select value={selectedLightning} onValueChange={setSelectedLightning}>
+              <SelectTrigger id="zap-lightning-address" className="min-w-0 gap-2">
+                <SelectValue placeholder={t('Select lightning address')}>
+                  {selectedLightning ? (
+                    <span className="flex min-w-0 items-center gap-2">
+                      <span className="shrink-0 text-lg leading-none text-yellow-400" aria-hidden>
+                        ⚡
+                      </span>
+                      <span className="min-w-0 truncate">{selectedLightning}</span>
                     </span>
-                    <span className="min-w-0 truncate">{selectedLightning}</span>
-                  </span>
-                ) : null}
-              </SelectValue>
-            </SelectTrigger>
-            <SelectContent>
-              {lightningAddressOptions.map((addr) => (
-                <SelectItem key={addr} value={addr} className="break-all">
-                  <span className="flex items-start gap-2">
-                    <span className="shrink-0 text-lg leading-none text-yellow-400" aria-hidden>
-                      ⚡
+                  ) : null}
+                </SelectValue>
+              </SelectTrigger>
+              <SelectContent>
+                {lightningAddressOptions.map((addr) => (
+                  <SelectItem key={addr} value={addr} className="break-all">
+                    <span className="flex items-start gap-2">
+                      <span className="shrink-0 text-lg leading-none text-yellow-400" aria-hidden>
+                        ⚡
+                      </span>
+                      <span className="min-w-0 break-all">{addr}</span>
                     </span>
-                    <span className="min-w-0 break-all">{addr}</span>
-                  </span>
-                </SelectItem>
-              ))}
-            </SelectContent>
-          </Select>
+                  </SelectItem>
+                ))}
+              </SelectContent>
+            </Select>
+          )}
         </div>
 
         <Button onClick={handleZap} className="w-full">
           {zapping && <Skeleton className="mr-2 inline-block size-4 shrink-0 rounded-full align-middle" aria-hidden />}{' '}
-          {t('Zap n sats', { n: sats })}
+          {t('Zap n sats', { n: formatSatsGrouped(clampedSats) })}
         </Button>
 
         {hasAlternativePayments ? (

src/hooks/useBtcUsdRate.ts

@@ -0,0 +1,19 @@
+import { fetchBtcUsdRate } from '@/lib/btc-usd-rate'
+import { useEffect, useState } from 'react'
+
+/** BTC/USD spot for zap amount hints (null while loading or if fetch failed). */
+export function useBtcUsdRate() {
+  const [btcUsd, setBtcUsd] = useState<number | null>(null)
+
+  useEffect(() => {
+    let cancelled = false
+    fetchBtcUsdRate().then((rate) => {
+      if (!cancelled) setBtcUsd(rate)
+    })
+    return () => {
+      cancelled = true
+    }
+  }, [])
+
+  return btcUsd
+}

src/hooks/useRecipientAlternativePayments.test.ts

@@ -0,0 +1,19 @@
+import { describe, expect, it } from 'vitest'
+import { buildRecipientZapPaymentData, mergeRecipientZapPaymentData } from './useRecipientAlternativePayments'
+import type { TProfile } from '@/types'
+
+describe('mergeRecipientZapPaymentData', () => {
+  it('keeps lightning from feed profile when relay fetch is still empty', () => {
+    const feedProfile = {
+      pubkey: 'aa'.repeat(32),
+      lightningAddress: 'user@example.com'
+    } as TProfile
+    const partial = buildRecipientZapPaymentData(null, feedProfile, null)
+    const empty = buildRecipientZapPaymentData(null, null, null)
+    const merged = mergeRecipientZapPaymentData(partial, empty)
+    expect(merged.canReceiveTip).toBe(true)
+    expect(
+      merged.alternativeGroups.length + (partial.canReceiveTip ? 1 : 0)
+    ).toBeGreaterThan(0)
+  })
+})

src/hooks/useRecipientAlternativePayments.ts

@@ -22,6 +22,48 @@ export type RecipientZapPaymentData = {
   canReceiveTip: boolean
 }
 
+export function buildRecipientZapPaymentData(
+  paymentInfo: TPaymentInfo | null,
+  profile: TProfile | null,
+  profileEvent: Event | null
+): RecipientZapPaymentData {
+  const canReceiveTip = recipientHasAnyPaymentOptions(paymentInfo, profile, profileEvent)
+  const merged = sortMergedPaymentMethods(mergePaymentMethods(paymentInfo, profile, profileEvent))
+  const alts = getAlternativePaymentMethods(merged)
+  const alternativeGroups = groupPaymentMethodsByDisplayType(alts)
+  return { paymentInfo, profile, profileEvent, alternativeGroups, canReceiveTip }
+}
+
+/** Combine feed/profile snapshot with fresher relay data (dialog opens fast, then enriches). */
+export function mergeRecipientZapPaymentData(
+  partial: RecipientZapPaymentData | null | undefined,
+  fresh: RecipientZapPaymentData | null | undefined
+): RecipientZapPaymentData {
+  if (!partial) {
+    return fresh ?? buildRecipientZapPaymentData(null, null, null)
+  }
+  if (!fresh) return partial
+
+  const profileEvent = fresh.profileEvent ?? partial.profileEvent
+  const profile = profileEvent
+    ? (fresh.profile ?? partial.profile)
+    : (partial.profile ?? fresh.profile)
+  const paymentInfo = pickRicherPaymentInfo(partial.paymentInfo, fresh.paymentInfo)
+
+  return buildRecipientZapPaymentData(paymentInfo, profile ?? null, profileEvent)
+}
+
+function pickRicherPaymentInfo(
+  a: TPaymentInfo | null | undefined,
+  b: TPaymentInfo | null | undefined
+): TPaymentInfo | null {
+  const score = (p: TPaymentInfo | null | undefined) =>
+    p?.methods?.length ?? (p?.payto ? 1 : 0)
+  if (score(b) > score(a)) return b ?? null
+  if (score(a) > score(b)) return a ?? null
+  return b ?? a ?? null
+}
+
 /** Kind 10133 + profile payto targets except the Lightning address used for zapping. */
 export function useRecipientZapPaymentData(
   recipientPubkey: string | undefined,
@@ -62,19 +104,10 @@ export function useRecipientZapPaymentData(
     }
   }, [recipientPubkey, enabled])
 
-  const canReceiveTip = useMemo(
-    () => recipientHasAnyPaymentOptions(paymentInfo, profile, profileEvent),
+  return useMemo(
+    () => buildRecipientZapPaymentData(paymentInfo, profile, profileEvent),
     [paymentInfo, profile, profileEvent]
   )
-
-  const alternativeGroups = useMemo(() => {
-    if (!recipientPubkey) return []
-    const merged = sortMergedPaymentMethods(mergePaymentMethods(paymentInfo, profile, profileEvent))
-    const alts = getAlternativePaymentMethods(merged)
-    return groupPaymentMethodsByDisplayType(alts)
-  }, [recipientPubkey, paymentInfo, profile, profileEvent])
-
-  return { paymentInfo, profile, profileEvent, alternativeGroups, canReceiveTip }
 }
 
 /** @deprecated Use {@link useRecipientZapPaymentData} */

src/lib/btc-usd-rate.ts

@@ -0,0 +1,21 @@
+const CACHE_MS = 5 * 60 * 1000
+
+let cache: { usd: number; at: number } | null = null
+
+/** Latest BTC/USD spot price (cached ~5 min). */
+export async function fetchBtcUsdRate(): Promise<number | null> {
+  if (cache && Date.now() - cache.at < CACHE_MS) {
+    return cache.usd
+  }
+  try {
+    const res = await fetch('https://mempool.space/api/v1/prices')
+    if (!res.ok) return cache?.usd ?? null
+    const data = (await res.json()) as { USD?: number }
+    const usd = Number(data.USD)
+    if (!Number.isFinite(usd) || usd <= 0) return cache?.usd ?? null
+    cache = { usd, at: Date.now() }
+    return usd
+  } catch {
+    return cache?.usd ?? null
+  }
+}

src/lib/lightning-zap-amount.test.ts

@@ -0,0 +1,21 @@
+import { describe, expect, it } from 'vitest'
+import {
+  MAX_ZAP_SATS,
+  clampZapSats,
+  parseGroupedIntegerInput,
+  shouldHighlightLeadingSatsGroups,
+  splitSatsGroupedParts
+} from './lightning'
+
+describe('zap sats amount limits', () => {
+  it('clamps to 7 digits', () => {
+    expect(clampZapSats(99_999_999)).toBe(MAX_ZAP_SATS)
+    expect(parseGroupedIntegerInput('12345678')).toBe(1_234_567)
+  })
+
+  it('highlights leading group above 999 999 sats', () => {
+    expect(shouldHighlightLeadingSatsGroups(999_999)).toBe(false)
+    expect(shouldHighlightLeadingSatsGroups(1_000_000)).toBe(true)
+    expect(splitSatsGroupedParts(1_000_000)).toEqual(['1', '000', '000'])
+  })
+})

src/lib/lightning.ts

@@ -13,6 +13,45 @@ export function formatAmount(amount: number) {
   return `${Math.round(amount / 100000) / 10}M`
 }
 
+const SAT_GROUP_SEPARATOR = '\u2009'
+
+/** Max sats digits in the zap amount field (9 999 999). */
+export const MAX_ZAP_SATS = 9_999_999
+
+/** Leading digit group + BTC hint styling above this amount (exclusive). */
+export const ZAP_SATS_HIGHLIGHT_ABOVE = 999_999
+
+/** Group sats in threes with a thin space (e.g. 210 000). */
+export function formatSatsGrouped(amount: number): string {
+  const n = clampZapSats(amount)
+  return n.toLocaleString('en-US').replace(/,/g, SAT_GROUP_SEPARATOR)
+}
+
+export function clampZapSats(amount: number): number {
+  if (!Number.isFinite(amount) || amount < 0) return 0
+  return Math.min(MAX_ZAP_SATS, Math.floor(amount))
+}
+
+/** True when amount is above 999 999 sats (≥ 1 000 000). */
+export function shouldHighlightLeadingSatsGroups(amount: number): boolean {
+  return clampZapSats(amount) > ZAP_SATS_HIGHLIGHT_ABOVE
+}
+
+/** Digit groups for display (e.g. ["210", "000"]). */
+export function splitSatsGroupedParts(amount: number): string[] {
+  const formatted = formatSatsGrouped(amount)
+  if (!formatted) return ['0']
+  return formatted.split(SAT_GROUP_SEPARATOR)
+}
+
+/** Parse user input that may contain digit grouping spaces. */
+export function parseGroupedIntegerInput(raw: string): number {
+  const digits = raw.replace(/\D/g, '').slice(0, 7)
+  if (digits === '') return 0
+  const num = parseInt(digits, 10)
+  return Number.isFinite(num) ? clampZapSats(num) : 0
+}
+
 export function getLightningAddressFromProfile(profile: TProfile) {
   if (profile.lightningAddress?.trim()) return profile.lightningAddress.trim()
   if (profile.lightningAddressList?.length) {

src/lib/merge-payment-methods.ts

@@ -281,6 +281,8 @@ export function groupPaymentMethodsByDisplayType(methods: MergedPaymentMethod[])
  */
 export function buildOrderedZapLightningAddresses(opts: {
   profileEvent?: Event | null
+  /** Parsed kind 0 when the event is not loaded yet (e.g. feed profile row). */
+  profile?: TProfile | null
   paymentInfo: ReturnType<typeof getPaymentInfoFromEvent> | null
   preferredAddress?: string | null
 }): string[] {
@@ -297,7 +299,8 @@ export function buildOrderedZapLightningAddresses(opts: {
   }
 
   const ev = opts.profileEvent
-  const profile = ev?.kind === kinds.Metadata ? getProfileFromEvent(ev) : null
+  const profile =
+    ev?.kind === kinds.Metadata ? getProfileFromEvent(ev) : (opts.profile ?? null)
   if (ev?.kind === kinds.Metadata) {
     for (const tag of ev.tags) {
       if (tag[0] === 'lud16' && tag[1]) add(tag[1])

src/lib/sats-fiat.test.ts

@@ -0,0 +1,22 @@
+import { describe, expect, it } from 'vitest'
+import { formatBtcFromSats, formatUsdFromSats, satsToBtc, satsToUsd } from './sats-fiat'
+
+describe('sats-fiat', () => {
+  it('converts sats to btc', () => {
+    expect(satsToBtc(100_000_000)).toBe(1)
+    expect(satsToBtc(210_000)).toBe(0.0021)
+  })
+
+  it('formats btc from sats', () => {
+    expect(formatBtcFromSats(0)).toBe('0 BTC')
+    expect(formatBtcFromSats(210_000)).toContain('BTC')
+    expect(formatBtcFromSats(210_000)).toMatch(/0\.0021|0,0021/)
+  })
+
+  it('formats usd when rate is known', () => {
+    expect(formatUsdFromSats(210_000, null)).toBeNull()
+    const usd = formatUsdFromSats(100_000_000, 100_000)
+    expect(usd).toMatch(/\$|USD/)
+    expect(satsToUsd(100_000_000, 100_000)).toBe(100_000)
+  })
+})

src/lib/sats-fiat.ts

@@ -0,0 +1,34 @@
+const SATS_PER_BTC = 100_000_000
+
+export function satsToBtc(sats: number): number {
+  return Math.max(0, sats) / SATS_PER_BTC
+}
+
+export function satsToUsd(sats: number, btcUsd: number): number {
+  return satsToBtc(sats) * btcUsd
+}
+
+/** Human-readable BTC equivalent (e.g. 0.0021 BTC). */
+export function formatBtcFromSats(sats: number): string {
+  const btc = satsToBtc(sats)
+  if (btc === 0) return '0 BTC'
+  const maxFrac = btc >= 1 ? 4 : btc >= 0.01 ? 6 : 8
+  const num = btc.toLocaleString(undefined, {
+    minimumFractionDigits: 0,
+    maximumFractionDigits: maxFrac
+  })
+  return `${num} BTC`
+}
+
+/** USD equivalent; returns null when no rate is available. */
+export function formatUsdFromSats(sats: number, btcUsd: number | null): string | null {
+  if (btcUsd == null || !Number.isFinite(btcUsd) || btcUsd <= 0) return null
+  const usd = satsToUsd(sats, btcUsd)
+  const maxFrac = usd >= 1 ? 2 : 4
+  return new Intl.NumberFormat(undefined, {
+    style: 'currency',
+    currency: 'USD',
+    minimumFractionDigits: 2,
+    maximumFractionDigits: maxFrac
+  }).format(usd)
+}