feat(backlog): server-fetch tasks + hydrate BacklogStore on page load

Page now fetches tasks parallel to stories and groups by story_id.
BacklogHydrationWrapper calls setInitialData on mount so the store
is ready for downstream SSE consumers.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/(app)/products/[id]/page.tsx

@@ -7,6 +7,7 @@ import { SplitPane } from '@/components/split-pane/split-pane'
 import { PbiList } from '@/components/backlog/pbi-list'
 import { StoryPanel } from '@/components/backlog/story-panel'
 import type { Story } from '@/components/backlog/story-panel'
+import { BacklogHydrationWrapper } from '@/components/backlog/backlog-hydration-wrapper'
 import { StartSprintButton } from '@/components/sprint/start-sprint-button'
 import { ActivateProductButton } from '@/components/shared/activate-product-button'
 import Link from 'next/link'
@@ -33,21 +34,37 @@ export default async function ProductBacklogPage({ params }: Props) {
     orderBy: [{ priority: 'asc' }, { sort_order: 'asc' }],
   })
 
-  const stories = await prisma.story.findMany({
-    where: { product_id: id },
-    orderBy: [{ priority: 'asc' }, { sort_order: 'asc' }],
-    select: {
-      id: true,
-      code: true,
-      title: true,
-      description: true,
-      acceptance_criteria: true,
-      priority: true,
-      status: true,
-      pbi_id: true,
-      created_at: true,
-    },
-  })
+  const [stories, tasks] = await Promise.all([
+    prisma.story.findMany({
+      where: { product_id: id },
+      orderBy: [{ priority: 'asc' }, { sort_order: 'asc' }],
+      select: {
+        id: true,
+        code: true,
+        title: true,
+        description: true,
+        acceptance_criteria: true,
+        priority: true,
+        status: true,
+        pbi_id: true,
+        created_at: true,
+      },
+    }),
+    prisma.task.findMany({
+      where: { story: { pbi: { product_id: id } } },
+      select: {
+        id: true,
+        title: true,
+        description: true,
+        priority: true,
+        status: true,
+        sort_order: true,
+        story_id: true,
+        created_at: true,
+      },
+      orderBy: [{ priority: 'asc' }, { sort_order: 'asc' }],
+    }),
+  ])
 
   // Group stories by PBI id
   const storiesByPbi: Record<string, Story[]> = {}
@@ -56,6 +73,13 @@ export default async function ProductBacklogPage({ params }: Props) {
     storiesByPbi[story.pbi_id].push(story)
   }
 
+  // Group tasks by story id
+  const tasksByStory: Record<string, typeof tasks> = {}
+  for (const task of tasks) {
+    if (!tasksByStory[task.story_id]) tasksByStory[task.story_id] = []
+    tasksByStory[task.story_id].push(task)
+  }
+
   const isDemo = session.isDemo ?? false
 
   return (
@@ -90,25 +114,33 @@ export default async function ProductBacklogPage({ params }: Props) {
 
       {/* Split pane */}
       <div className="flex-1 overflow-hidden">
-        <SplitPane
-          cookieKey={`backlog-${id}`}
-          defaultSplit={[20, 80]}
-          tabLabels={['Backlog', 'Stories']}
-          panes={[
-            <PbiList
-              key="pbi"
-              productId={id}
-              pbis={pbis.map((p: (typeof pbis)[number]) => ({ id: p.id, code: p.code, title: p.title, priority: p.priority, description: p.description, created_at: p.created_at, status: pbiStatusToApi(p.status) }))}
-              isDemo={isDemo}
-            />,
-            <StoryPanel
-              key="story"
-              productId={id}
-              storiesByPbi={storiesByPbi}
-              isDemo={isDemo}
-            />,
-          ]}
-        />
+        <BacklogHydrationWrapper
+          initialData={{
+            pbis: pbis.map((p) => ({ id: p.id, code: p.code, title: p.title, priority: p.priority, description: p.description, created_at: p.created_at, status: pbiStatusToApi(p.status) })),
+            storiesByPbi,
+            tasksByStory,
+          }}
+        >
+          <SplitPane
+            cookieKey={`backlog-${id}`}
+            defaultSplit={[20, 80]}
+            tabLabels={['Backlog', 'Stories']}
+            panes={[
+              <PbiList
+                key="pbi"
+                productId={id}
+                pbis={pbis.map((p: (typeof pbis)[number]) => ({ id: p.id, code: p.code, title: p.title, priority: p.priority, description: p.description, created_at: p.created_at, status: pbiStatusToApi(p.status) }))}
+                isDemo={isDemo}
+              />,
+              <StoryPanel
+                key="story"
+                productId={id}
+                storiesByPbi={storiesByPbi}
+                isDemo={isDemo}
+              />,
+            ]}
+          />
+        </BacklogHydrationWrapper>
       </div>
     </div>
   )

components/backlog/backlog-hydration-wrapper.tsx

@@ -0,0 +1,26 @@
+'use client'
+
+import { useEffect } from 'react'
+import { useBacklogStore, type BacklogPbi, type BacklogStory, type BacklogTask } from '@/stores/backlog-store'
+
+interface InitialData {
+  pbis: BacklogPbi[]
+  storiesByPbi: Record<string, BacklogStory[]>
+  tasksByStory: Record<string, BacklogTask[]>
+}
+
+interface BacklogHydrationWrapperProps {
+  initialData: InitialData
+  children: React.ReactNode
+}
+
+export function BacklogHydrationWrapper({ initialData, children }: BacklogHydrationWrapperProps) {
+  const setInitialData = useBacklogStore((s) => s.setInitialData)
+
+  useEffect(() => {
+    setInitialData(initialData)
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [])
+
+  return <>{children}</>
+}