diff --git a/components/bible/bible-reader-app.tsx b/components/bible/bible-reader-app.tsx
index a2e6f8f..355d0fe 100644
--- a/components/bible/bible-reader-app.tsx
+++ b/components/bible/bible-reader-app.tsx
@@ -1,13 +1,15 @@
 'use client'
-import { useState, useEffect } from 'react'
+import { useState, useEffect, useRef } from 'react'
 import { useLocale } from 'next-intl'
 import { Box, Typography, Button } from '@mui/material'
-import { BibleChapter, BibleVerse } from '@/types'
+import { BibleChapter, BibleVerse, BibleHighlight, HighlightColor } from '@/types'
 import { getCachedChapter, cacheChapter } from '@/lib/cache-manager'
 import { SearchNavigator } from './search-navigator'
 import { ReadingView } from './reading-view'
 import { VersDetailsPanel } from './verse-details-panel'
 import { ReadingSettings } from './reading-settings'
+import { HighlightSyncManager } from '@/lib/highlight-sync-manager'
+import { addHighlight, updateHighlight, getHighlightsByVerse, deleteHighlight, getAllHighlights } from '@/lib/highlight-manager'
 
 interface BookInfo {
   id: string // UUID
@@ -31,6 +33,8 @@ export function BibleReaderApp() {
   const [versionId, setVersionId] = useState<string>('')
   const [error, setError] = useState<string | null>(null)
   const [booksLoading, setBooksLoading] = useState(true)
+  const [highlights, setHighlights] = useState<Map<string, BibleHighlight>>(new Map())
+  const syncManager = useRef<HighlightSyncManager | null>(null)
 
   // Load books on mount or when locale changes
   useEffect(() => {
@@ -44,6 +48,24 @@ export function BibleReaderApp() {
     }
   }, [bookId, chapter, booksLoading, books.length])
 
+  // Initialize sync manager on mount
+  useEffect(() => {
+    syncManager.current = new HighlightSyncManager()
+    syncManager.current.init()
+    syncManager.current.startAutoSync(30000, () => {
+      performSync()
+    })
+
+    return () => {
+      syncManager.current?.stopAutoSync()
+    }
+  }, [])
+
+  // Load all highlights on mount
+  useEffect(() => {
+    loadAllHighlights()
+  }, [])
+
   async function loadBooks() {
     setBooksLoading(true)
     setError(null)
@@ -168,6 +190,95 @@ export function BibleReaderApp() {
     console.log(`Note for verse ${selectedVerse.id}:`, note)
   }
 
+  async function loadAllHighlights() {
+    try {
+      const highlightList = await getAllHighlights()
+      const map = new Map(highlightList.map(h => [h.verseId, h]))
+      setHighlights(map)
+    } catch (error) {
+      console.error('Failed to load highlights:', error)
+    }
+  }
+
+  async function handleHighlightVerse(color: HighlightColor = 'yellow') {
+    if (!selectedVerse) return
+
+    const highlight: BibleHighlight = {
+      id: `h-${selectedVerse.id}-${Date.now()}`,
+      verseId: selectedVerse.id,
+      color,
+      createdAt: Date.now(),
+      updatedAt: Date.now(),
+      syncStatus: 'pending'
+    }
+
+    try {
+      await addHighlight(highlight)
+      const newMap = new Map(highlights)
+      newMap.set(selectedVerse.id, highlight)
+      setHighlights(newMap)
+    } catch (error) {
+      console.error('Failed to highlight verse:', error)
+    }
+  }
+
+  async function handleChangeHighlightColor(color: HighlightColor) {
+    if (!selectedVerse) return
+
+    const existing = highlights.get(selectedVerse.id)
+    if (existing) {
+      const updated = {
+        ...existing,
+        color,
+        updatedAt: Date.now(),
+        syncStatus: 'pending' as const
+      }
+      try {
+        await updateHighlight(updated)
+        const newMap = new Map(highlights)
+        newMap.set(selectedVerse.id, updated)
+        setHighlights(newMap)
+      } catch (error) {
+        console.error('Failed to update highlight color:', error)
+      }
+    }
+  }
+
+  async function handleRemoveHighlight() {
+    if (!selectedVerse) return
+
+    try {
+      // Find and delete all highlights for this verse
+      const existing = highlights.get(selectedVerse.id)
+      if (existing) {
+        await deleteHighlight(existing.id)
+        const newMap = new Map(highlights)
+        newMap.delete(selectedVerse.id)
+        setHighlights(newMap)
+      }
+    } catch (error) {
+      console.error('Failed to remove highlight:', error)
+    }
+  }
+
+  async function performSync() {
+    if (!syncManager.current) return
+
+    try {
+      const pending = await syncManager.current.getPendingSyncItems()
+      if (pending.length === 0) return
+
+      await syncManager.current.markSyncing(pending.map(h => h.id))
+
+      // TODO: POST to /api/highlights/bulk in Phase 2.1B
+
+      await syncManager.current.markSynced(pending.map(h => h.id))
+    } catch (error) {
+      console.error('Sync failed:', error)
+      // Mark items with error status
+    }
+  }
+
   return (
     <Box sx={{ display: 'flex', flexDirection: 'column', height: 'auto', overflow: 'hidden' }}>
       {/* Header with search */}
@@ -238,6 +349,11 @@ export function BibleReaderApp() {
         isBookmarked={selectedVerse ? bookmarks.has(selectedVerse.id) : false}
         onToggleBookmark={handleToggleBookmark}
         onAddNote={handleAddNote}
+        isHighlighted={highlights.has(selectedVerse?.id || '')}
+        currentHighlightColor={highlights.get(selectedVerse?.id || '')?.color}
+        onHighlightVerse={handleHighlightVerse}
+        onChangeHighlightColor={handleChangeHighlightColor}
+        onRemoveHighlight={handleRemoveHighlight}
       />
 
       {/* Settings panel */}
diff --git a/components/bible/verse-details-panel.tsx b/components/bible/verse-details-panel.tsx
index 13f74f7..543baaa 100644
--- a/components/bible/verse-details-panel.tsx
+++ b/components/bible/verse-details-panel.tsx
@@ -2,7 +2,7 @@
 import { useState, useEffect } from 'react'
 import { Box, Paper, Typography, Tabs, Tab, IconButton, useMediaQuery, useTheme, TextField, Button } from '@mui/material'
 import { Close, Bookmark, BookmarkBorder } from '@mui/icons-material'
-import { BibleVerse } from '@/types'
+import { BibleVerse, HighlightColor } from '@/types'
 import { HighlightsTab } from './highlights-tab'
 
 interface VersDetailsPanelProps {
@@ -12,6 +12,11 @@ interface VersDetailsPanelProps {
   isBookmarked: boolean
   onToggleBookmark: () => void
   onAddNote: (note: string) => void
+  isHighlighted?: boolean
+  currentHighlightColor?: HighlightColor | null
+  onHighlightVerse?: (color: HighlightColor) => void
+  onChangeHighlightColor?: (color: HighlightColor) => void
+  onRemoveHighlight?: () => void
 }
 
 export function VersDetailsPanel({
@@ -21,6 +26,11 @@ export function VersDetailsPanel({
   isBookmarked,
   onToggleBookmark,
   onAddNote,
+  isHighlighted,
+  currentHighlightColor,
+  onHighlightVerse,
+  onChangeHighlightColor,
+  onRemoveHighlight,
 }: VersDetailsPanelProps) {
   const theme = useTheme()
   const isMobile = useMediaQuery(theme.breakpoints.down('sm'))
@@ -121,10 +131,16 @@ export function VersDetailsPanel({
         {tabValue === 1 && (
           <HighlightsTab
             verse={verse}
-            isHighlighted={false} // TODO: get from state
-            currentColor={null} // TODO: get from state
-            onToggleHighlight={() => {}} // TODO: implement
-            onColorChange={() => {}} // TODO: implement
+            isHighlighted={isHighlighted || false}
+            currentColor={currentHighlightColor || null}
+            onToggleHighlight={() => {
+              if (isHighlighted) {
+                onRemoveHighlight?.()
+              } else {
+                onHighlightVerse?.('yellow')
+              }
+            }}
+            onColorChange={(color) => onChangeHighlightColor?.(color)}
           />
         )}