diff --git a/components/ChangelogTabs.tsx b/components/ChangelogTabs.tsx
index d73ae00..a92d8f5 100644
--- a/components/ChangelogTabs.tsx
+++ b/components/ChangelogTabs.tsx
@@ -4,6 +4,8 @@ import { useEffect, useState } from 'react'
 import { PortableTextRenderer } from '@/components/PortableTextRenderer'
 import { RoadmapItem } from '@/components/RoadmapItem'
 import type { ChangelogEntry, RoadmapItemData, Tab, VoteState } from '@/types/changelog'
+import { useAuth } from '@/context/AuthContext'
+import Link from 'next/link'
 
 const TABS: { id: Tab; label: string }[] = [
   { id: 'whats-new', label: "What's New" },
@@ -44,8 +46,71 @@ export function ChangelogTabs({
       )
   )
 
-  // Filled in Task 5 — no-op for now
-  function handleVote(_id: string) {}
+  const { user } = useAuth()
+  const [showSignInPrompt, setShowSignInPrompt] = useState(false)
+  const [votesFetched, setVotesFetched] = useState(false)
+
+  // Fetch vote state when the What's Next tab is first viewed
+  useEffect(() => {
+    if (activeTab !== 'whats-next' || votesFetched || roadmapItems.length === 0) return
+    setVotesFetched(true)
+
+    const ids = roadmapItems.map((i) => i._id).join(',')
+    fetch(`/api/roadmap/votes?ids=${encodeURIComponent(ids)}`, {
+      credentials: 'include',
+    })
+      .then((r) => (r.ok ? r.json() : {}))
+      .then((data: Record<string, { count: number; voted: boolean }>) => {
+        setVoteState((prev) => {
+          const next = { ...prev }
+          for (const [id, v] of Object.entries(data)) {
+            next[id] = { count: v.count, voted: v.voted, loading: false }
+          }
+          return next
+        })
+      })
+      .catch(() => {
+        // Spring Boot not yet available — silently keep count=0
+      })
+  }, [activeTab, votesFetched, roadmapItems])
+
+  async function handleVote(id: string) {
+    if (!user) {
+      setShowSignInPrompt(true)
+      setTimeout(() => setShowSignInPrompt(false), 4000)
+      return
+    }
+
+    const current = voteState[id] ?? { count: 0, voted: false, loading: false }
+
+    // Optimistic update
+    setVoteState((prev) => ({
+      ...prev,
+      [id]: {
+        count: current.voted ? current.count - 1 : current.count + 1,
+        voted: !current.voted,
+        loading: true,
+      },
+    }))
+
+    try {
+      const res = await fetch(`/api/roadmap/${encodeURIComponent(id)}/vote`, {
+        method: 'POST',
+        credentials: 'include',
+      })
+      if (res.ok) {
+        const data: { count: number; voted: boolean } = await res.json()
+        setVoteState((prev) => ({
+          ...prev,
+          [id]: { count: data.count, voted: data.voted, loading: false },
+        }))
+      } else {
+        setVoteState((prev) => ({ ...prev, [id]: { ...current, loading: false } }))
+      }
+    } catch {
+      setVoteState((prev) => ({ ...prev, [id]: { ...current, loading: false } }))
+    }
+  }
 
   useEffect(() => {
     const hash = window.location.hash.replace('#', '') as Tab
@@ -140,63 +205,67 @@ export function ChangelogTabs({
             </p>
           ) : (
             <>
-              {roadmapItems.filter((i) => i.status === 'in-progress').length > 0 && (
-                <div className="mb-8">
-                  <p className="mb-3 text-[10px] font-bold uppercase tracking-[0.18em] text-zinc-600">
-                    In Progress
-                  </p>
-                  <div className="flex flex-col gap-2.5">
-                    {roadmapItems
-                      .filter((i) => i.status === 'in-progress')
-                      .map((item) => (
-                        <RoadmapItem
-                          key={item._id}
-                          id={item._id}
-                          title={item.title}
-                          description={item.description}
-                          status={item.status}
-                          vote={
-                            voteState[item._id] ?? {
-                              count: 0,
-                              voted: false,
-                              loading: false,
-                            }
-                          }
-                          onVote={handleVote}
-                        />
-                      ))}
-                  </div>
-                </div>
-              )}
+              {(() => {
+                const inProgress = roadmapItems.filter((i) => i.status === 'in-progress')
+                const planned = roadmapItems.filter((i) => i.status === 'planned')
+                return (
+                  <>
+                    {inProgress.length > 0 && (
+                      <div className="mb-8">
+                        <p className="mb-3 text-[10px] font-bold uppercase tracking-[0.18em] text-zinc-600">
+                          In Progress
+                        </p>
+                        <div className="flex flex-col gap-2.5">
+                          {inProgress.map((item) => (
+                            <RoadmapItem
+                              key={item._id}
+                              id={item._id}
+                              title={item.title}
+                              description={item.description}
+                              status={item.status}
+                              vote={
+                                voteState[item._id] ?? {
+                                  count: 0,
+                                  voted: false,
+                                  loading: false,
+                                }
+                              }
+                              onVote={handleVote}
+                            />
+                          ))}
+                        </div>
+                      </div>
+                    )}
 
-              {roadmapItems.filter((i) => i.status === 'planned').length > 0 && (
-                <div>
-                  <p className="mb-3 text-[10px] font-bold uppercase tracking-[0.18em] text-zinc-600">
-                    Planned
-                  </p>
-                  <div className="flex flex-col gap-2.5">
-                    {roadmapItems
-                      .filter((i) => i.status === 'planned')
-                      .map((item) => (
-                        <RoadmapItem
-                          key={item._id}
-                          id={item._id}
-                          title={item.title}
-                          description={item.description}
-                          status={item.status}
-                          vote={
-                            voteState[item._id] ?? {
-                              count: 0,
-                              voted: false,
-                              loading: false,
-                            }
-                          }
-                          onVote={handleVote}
-                        />
-                      ))}
-                  </div>
-                </div>
-              )}
+                    {planned.length > 0 && (
+                      <div>
+                        <p className="mb-3 text-[10px] font-bold uppercase tracking-[0.18em] text-zinc-600">
+                          Planned
+                        </p>
+                        <div className="flex flex-col gap-2.5">
+                          {planned.map((item) => (
+                            <RoadmapItem
+                              key={item._id}
+                              id={item._id}
+                              title={item.title}
+                              description={item.description}
+                              status={item.status}
+                              vote={
+                                voteState[item._id] ?? {
+                                  count: 0,
+                                  voted: false,
+                                  loading: false,
+                                }
+                              }
+                              onVote={handleVote}
+                            />
+                          ))}
+                        </div>
+                      </div>
+                    )}
+                  </>
+                )
+              })()}
 
               <p className="mt-8 text-xs text-zinc-600">
                 Don&apos;t see what you need?{' '}
@@ -207,6 +276,15 @@ export function ChangelogTabs({
                   Give us feedback →
                 </button>
               </p>
+
+              {showSignInPrompt && (
+                <p className="mt-3 text-xs text-amber-400">
+                  <Link href="/login" className="underline underline-offset-2 hover:text-amber-300">
+                    Sign in
+                  </Link>{' '}
+                  to upvote roadmap items.
+                </p>
+              )}
             </>
           )}
         </div>