diff --git a/actions/ideas.ts b/actions/ideas.ts
index 1ae5e47..dbfa806 100644
--- a/actions/ideas.ts
+++ b/actions/ideas.ts
@@ -10,6 +10,8 @@ import { revalidatePath } from 'next/cache'
 import { cookies } from 'next/headers'
 import { getIronSession } from 'iron-session'
 
+import { z } from 'zod'
+
 import { prisma } from '@/lib/prisma'
 import { SessionData, sessionOptions } from '@/lib/session'
 import { enforceUserRateLimit } from '@/lib/rate-limit'
@@ -165,6 +167,63 @@ export async function deleteIdeaAction(id: string): Promise<ActionResult> {
   return { success: true }
 }
 
+// ---------------------------------------------------------------------------
+// Secondary products
+
+const secondaryProductsSchema = z.object({
+  ideaId: z.string().cuid(),
+  productIds: z.array(z.string().cuid()).max(10),
+})
+
+export async function updateSecondaryProductsAction(
+  ideaId: string,
+  productIds: string[],
+): Promise<ActionResult> {
+  const session = await getSession()
+  if (!session.userId) return { error: 'Niet ingelogd', code: 401 }
+  if (session.isDemo) return { error: 'Niet beschikbaar in demo-modus', code: 403 }
+
+  const parsed = secondaryProductsSchema.safeParse({ ideaId, productIds })
+  if (!parsed.success) return { error: 'Ongeldige invoer', code: 422 }
+
+  const idea = await prisma.idea.findFirst({
+    where: { id: parsed.data.ideaId, user_id: session.userId },
+    select: { id: true, product_id: true },
+  })
+  if (!idea) return { error: 'Idee niet gevonden', code: 404 }
+
+  // Verwijder primair product uit de lijst (mag niet dubbel)
+  const filtered = parsed.data.productIds.filter((pid) => pid !== idea.product_id)
+
+  // Valideer dat alle gevraagde producten toegankelijk zijn voor de user
+  if (filtered.length > 0) {
+    const { productAccessFilter } = await import('@/lib/product-access')
+    const accessible = await prisma.product.findMany({
+      where: { id: { in: filtered }, ...productAccessFilter(session.userId) },
+      select: { id: true },
+    })
+    if (accessible.length !== filtered.length)
+      return { error: 'Een of meer producten zijn niet toegankelijk', code: 403 }
+  }
+
+  // Atomisch: verwijder alle bestaande, voeg nieuwe in
+  await prisma.$transaction([
+    prisma.ideaProduct.deleteMany({ where: { idea_id: idea.id } }),
+    ...(filtered.length > 0
+      ? [
+          prisma.ideaProduct.createMany({
+            data: filtered.map((pid) => ({ idea_id: idea.id, product_id: pid })),
+            skipDuplicates: true,
+          }),
+        ]
+      : []),
+  ])
+
+  revalidatePath('/ideas/' + idea.id, 'page')
+  revalidatePath('/ideas', 'page')
+  return { success: true }
+}
+
 // ---------------------------------------------------------------------------
 // Markdown-edits (grill_md & plan_md handmatig fine-tunen)
 
diff --git a/app/(app)/ideas/[id]/page.tsx b/app/(app)/ideas/[id]/page.tsx
index 10439f2..d548a81 100644
--- a/app/(app)/ideas/[id]/page.tsx
+++ b/app/(app)/ideas/[id]/page.tsx
@@ -29,6 +29,7 @@ export default async function IdeaDetailPage({ params, searchParams }: PageProps
     include: {
       product: { select: { id: true, name: true, repo_url: true } },
       pbi: { select: { id: true, code: true, title: true } },
+      secondary_products: { include: { product: { select: { id: true, name: true } } } },
     },
   })
   if (!idea) notFound()
diff --git a/app/(app)/ideas/page.tsx b/app/(app)/ideas/page.tsx
index 142e376..1b2c45d 100644
--- a/app/(app)/ideas/page.tsx
+++ b/app/(app)/ideas/page.tsx
@@ -16,7 +16,10 @@ export default async function IdeasPage() {
   const ideas = await prisma.idea.findMany({
     where: { user_id: session.userId, archived: false },
     orderBy: { created_at: 'desc' },
-    include: { product: { select: { id: true, name: true, repo_url: true } } },
+    include: {
+      product: { select: { id: true, name: true, repo_url: true } },
+      secondary_products: { include: { product: { select: { id: true, name: true } } } },
+    },
     take: 200,
   })
 
diff --git a/app/api/ideas/route.ts b/app/api/ideas/route.ts
index 84d1ad7..7da26ac 100644
--- a/app/api/ideas/route.ts
+++ b/app/api/ideas/route.ts
@@ -32,7 +32,10 @@ export async function GET(request: Request) {
       ...(productIdParam ? { product_id: productIdParam } : {}),
       ...(status ? { status } : {}),
     },
-    include: { product: { select: { id: true, name: true, repo_url: true } } },
+    include: {
+      product: { select: { id: true, name: true, repo_url: true } },
+      secondary_products: { include: { product: { select: { id: true, name: true } } } },
+    },
     orderBy: { created_at: 'desc' },
     take: 200,
   })
diff --git a/lib/idea-dto.ts b/lib/idea-dto.ts
index b32d14a..3b6557c 100644
--- a/lib/idea-dto.ts
+++ b/lib/idea-dto.ts
@@ -9,6 +9,7 @@ import type { Idea, IdeaStatus, Product } from '@prisma/client'
 type IdeaWithProduct = Idea & {
   product: Pick<Product, 'id' | 'name' | 'repo_url'> | null
   pbi?: { id: string; code: string; title: string } | null
+  secondary_products?: { id: string; product_id: string; product: { id: string; name: string } }[]
 }
 
 export interface IdeaDto {
@@ -21,6 +22,7 @@ export interface IdeaDto {
   product: { id: string; name: string; repo_url: string | null } | null
   pbi_id: string | null
   pbi?: { id: string; code: string; title: string } | null
+  secondary_products: { id: string; product_id: string; product: { id: string; name: string } }[]
   archived: boolean
   has_grill_md: boolean
   has_plan_md: boolean
@@ -39,6 +41,7 @@ export function ideaToDto(idea: IdeaWithProduct & { status: IdeaStatus }): IdeaD
     product: idea.product,
     pbi_id: idea.pbi_id,
     pbi: idea.pbi ?? null,
+    secondary_products: idea.secondary_products ?? [],
     archived: idea.archived,
     // Geen md-content in lijst-payloads (kan groot zijn) — enkel een vlag.
     has_grill_md: idea.grill_md !== null,