diff --git a/src/__tests__/api/versions.test.ts b/src/__tests__/api/versions.test.ts
index 2ef1bbe4..18115902 100644
--- a/src/__tests__/api/versions.test.ts
+++ b/src/__tests__/api/versions.test.ts
@@ -29,6 +29,10 @@ describe("GET /api/prompts/[id]/versions", () => {
   });
 
   it("should return empty array for prompt with no versions", async () => {
+    vi.mocked(db.prompt.findUnique).mockResolvedValue({
+      isPrivate: false,
+      authorId: "user1",
+    } as never);
     vi.mocked(db.promptVersion.findMany).mockResolvedValue([]);
 
     const request = new Request("http://localhost:3000/api/prompts/123/versions");
@@ -42,6 +46,10 @@ describe("GET /api/prompts/[id]/versions", () => {
   });
 
   it("should return versions ordered by version desc", async () => {
+    vi.mocked(db.prompt.findUnique).mockResolvedValue({
+      isPrivate: false,
+      authorId: "user1",
+    } as never);
     vi.mocked(db.promptVersion.findMany).mockResolvedValue([
       {
         id: "v3",
@@ -83,6 +91,10 @@ describe("GET /api/prompts/[id]/versions", () => {
   });
 
   it("should include author info in response", async () => {
+    vi.mocked(db.prompt.findUnique).mockResolvedValue({
+      isPrivate: false,
+      authorId: "user1",
+    } as never);
     vi.mocked(db.promptVersion.findMany).mockResolvedValue([
       {
         id: "v1",
@@ -106,6 +118,10 @@ describe("GET /api/prompts/[id]/versions", () => {
   });
 
   it("should call findMany with correct parameters", async () => {
+    vi.mocked(db.prompt.findUnique).mockResolvedValue({
+      isPrivate: false,
+      authorId: "user1",
+    } as never);
     vi.mocked(db.promptVersion.findMany).mockResolvedValue([]);
 
     const request = new Request("http://localhost:3000/api/prompts/123/versions");
diff --git a/src/__tests__/lib/prompt-access.test.ts b/src/__tests__/lib/prompt-access.test.ts
new file mode 100644
index 00000000..5730663b
--- /dev/null
+++ b/src/__tests__/lib/prompt-access.test.ts
@@ -0,0 +1,108 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { canViewPrompt, checkPromptAccess } from "@/lib/prompt-access";
+import { auth } from "@/lib/auth";
+import type { Session } from "next-auth";
+
+vi.mock("@/lib/auth", () => ({
+  auth: vi.fn(),
+}));
+
+describe("canViewPrompt", () => {
+  it("should return false for null prompt", () => {
+    expect(canViewPrompt(null, null)).toBe(false);
+  });
+
+  it("should return true for public prompt with no session", () => {
+    expect(
+      canViewPrompt({ isPrivate: false, authorId: "user1" }, null)
+    ).toBe(true);
+  });
+
+  it("should return true for public prompt with any session", () => {
+    const session = { user: { id: "other" } } as Session;
+    expect(
+      canViewPrompt({ isPrivate: false, authorId: "user1" }, session)
+    ).toBe(true);
+  });
+
+  it("should return false for private prompt with no session", () => {
+    expect(
+      canViewPrompt({ isPrivate: true, authorId: "user1" }, null)
+    ).toBe(false);
+  });
+
+  it("should return false for private prompt when user is not owner", () => {
+    const session = { user: { id: "other", role: "USER" } } as Session;
+    expect(
+      canViewPrompt({ isPrivate: true, authorId: "user1" }, session)
+    ).toBe(false);
+  });
+
+  it("should return true for private prompt when user is the owner", () => {
+    const session = { user: { id: "user1", role: "USER" } } as Session;
+    expect(
+      canViewPrompt({ isPrivate: true, authorId: "user1" }, session)
+    ).toBe(true);
+  });
+
+  it("should return true for private prompt when user is admin", () => {
+    const session = { user: { id: "admin1", role: "ADMIN" } } as Session;
+    expect(
+      canViewPrompt({ isPrivate: true, authorId: "user1" }, session)
+    ).toBe(true);
+  });
+
+  it("should return false for private prompt with session missing user", () => {
+    const session = {} as Session;
+    expect(
+      canViewPrompt({ isPrivate: true, authorId: "user1" }, session)
+    ).toBe(false);
+  });
+});
+
+describe("checkPromptAccess", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("should return 404 for null prompt", async () => {
+    const result = await checkPromptAccess(null);
+    expect(result).not.toBeNull();
+    expect(result!.status).toBe(404);
+    const data = await result!.json();
+    expect(data.error).toBe("not_found");
+  });
+
+  it("should return null for public prompt (no auth call)", async () => {
+    const result = await checkPromptAccess({ isPrivate: false, authorId: "user1" });
+    expect(result).toBeNull();
+    expect(auth).not.toHaveBeenCalled();
+  });
+
+  it("should return 404 for private prompt with no session", async () => {
+    vi.mocked(auth).mockResolvedValue(null);
+    const result = await checkPromptAccess({ isPrivate: true, authorId: "user1" });
+    expect(result).not.toBeNull();
+    expect(result!.status).toBe(404);
+    expect(auth).toHaveBeenCalledOnce();
+  });
+
+  it("should return 404 for private prompt when user is not owner", async () => {
+    vi.mocked(auth).mockResolvedValue({ user: { id: "other", role: "USER" } } as never);
+    const result = await checkPromptAccess({ isPrivate: true, authorId: "user1" });
+    expect(result).not.toBeNull();
+    expect(result!.status).toBe(404);
+  });
+
+  it("should return null for private prompt when user is the owner", async () => {
+    vi.mocked(auth).mockResolvedValue({ user: { id: "user1", role: "USER" } } as never);
+    const result = await checkPromptAccess({ isPrivate: true, authorId: "user1" });
+    expect(result).toBeNull();
+  });
+
+  it("should return null for private prompt when user is admin", async () => {
+    vi.mocked(auth).mockResolvedValue({ user: { id: "admin1", role: "ADMIN" } } as never);
+    const result = await checkPromptAccess({ isPrivate: true, authorId: "user1" });
+    expect(result).toBeNull();
+  });
+});
diff --git a/src/app/api/prompts/[id]/changes/[changeId]/route.ts b/src/app/api/prompts/[id]/changes/[changeId]/route.ts
index cff5d962..39ff3fae 100644
--- a/src/app/api/prompts/[id]/changes/[changeId]/route.ts
+++ b/src/app/api/prompts/[id]/changes/[changeId]/route.ts
@@ -2,6 +2,7 @@ import { NextRequest, NextResponse } from "next/server";
 import { z } from "zod";
 import { auth } from "@/lib/auth";
 import { db } from "@/lib/db";
+import { checkPromptAccess } from "@/lib/prompt-access";
 
 const updateChangeRequestSchema = z.object({
   status: z.enum(["APPROVED", "REJECTED", "PENDING"]),
@@ -196,7 +197,8 @@ export async function GET(
           select: {
             id: true,
             title: true,
-            content: true,
+            isPrivate: true,
+            authorId: true,
           },
         },
       },
@@ -209,6 +211,9 @@ export async function GET(
       );
     }
 
+    const denied = await checkPromptAccess(changeRequest.prompt);
+    if (denied) return denied;
+
     return NextResponse.json(changeRequest);
   } catch (error) {
     console.error("Get change request error:", error);
diff --git a/src/app/api/prompts/[id]/changes/route.ts b/src/app/api/prompts/[id]/changes/route.ts
index 23f35a9e..31c70b19 100644
--- a/src/app/api/prompts/[id]/changes/route.ts
+++ b/src/app/api/prompts/[id]/changes/route.ts
@@ -2,6 +2,7 @@ import { NextRequest, NextResponse } from "next/server";
 import { z } from "zod";
 import { auth } from "@/lib/auth";
 import { db } from "@/lib/db";
+import { checkPromptAccess } from "@/lib/prompt-access";
 
 const createChangeRequestSchema = z.object({
   proposedContent: z.string().min(1),
@@ -94,6 +95,14 @@ export async function GET(
   try {
     const { id: promptId } = await params;
 
+    const prompt = await db.prompt.findUnique({
+      where: { id: promptId },
+      select: { isPrivate: true, authorId: true },
+    });
+
+    const denied = await checkPromptAccess(prompt);
+    if (denied) return denied;
+
     const changeRequests = await db.changeRequest.findMany({
       where: { promptId },
       orderBy: { createdAt: "desc" },
diff --git a/src/app/api/prompts/[id]/examples/route.ts b/src/app/api/prompts/[id]/examples/route.ts
index 8009c90a..baa57811 100644
--- a/src/app/api/prompts/[id]/examples/route.ts
+++ b/src/app/api/prompts/[id]/examples/route.ts
@@ -2,6 +2,7 @@ import { NextRequest, NextResponse } from "next/server";
 import { auth } from "@/lib/auth";
 import { db } from "@/lib/db";
 import { z } from "zod";
+import { checkPromptAccess } from "@/lib/prompt-access";
 
 const addExampleSchema = z.object({
   mediaUrl: z.string().url(),
@@ -16,12 +17,11 @@ export async function GET(
 
   const prompt = await db.prompt.findUnique({
     where: { id: promptId },
-    select: { id: true, type: true },
+    select: { id: true, type: true, isPrivate: true, authorId: true },
   });
 
-  if (!prompt) {
-    return NextResponse.json({ error: "Prompt not found" }, { status: 404 });
-  }
+  const denied = await checkPromptAccess(prompt);
+  if (denied || !prompt) return denied!;
 
   // Only allow examples for IMAGE and VIDEO prompts
   if (prompt.type !== "IMAGE" && prompt.type !== "VIDEO") {
diff --git a/src/app/api/prompts/[id]/versions/route.ts b/src/app/api/prompts/[id]/versions/route.ts
index a894e81f..19b280b9 100644
--- a/src/app/api/prompts/[id]/versions/route.ts
+++ b/src/app/api/prompts/[id]/versions/route.ts
@@ -2,6 +2,7 @@ import { NextRequest, NextResponse } from "next/server";
 import { z } from "zod";
 import { auth } from "@/lib/auth";
 import { db } from "@/lib/db";
+import { checkPromptAccess } from "@/lib/prompt-access";
 
 const createVersionSchema = z.object({
   content: z.string().min(1, "Content is required"),
@@ -116,6 +117,14 @@ export async function GET(
   try {
     const { id: promptId } = await params;
 
+    const prompt = await db.prompt.findUnique({
+      where: { id: promptId },
+      select: { isPrivate: true, authorId: true },
+    });
+
+    const denied = await checkPromptAccess(prompt);
+    if (denied) return denied;
+
     const versions = await db.promptVersion.findMany({
       where: { promptId },
       orderBy: { version: "desc" },
diff --git a/src/app/api/prompts/[id]/vote/route.ts b/src/app/api/prompts/[id]/vote/route.ts
index 468723bf..71b64292 100644
--- a/src/app/api/prompts/[id]/vote/route.ts
+++ b/src/app/api/prompts/[id]/vote/route.ts
@@ -1,6 +1,7 @@
 import { NextRequest, NextResponse } from "next/server";
 import { auth } from "@/lib/auth";
 import { db } from "@/lib/db";
+import { checkPromptAccess } from "@/lib/prompt-access";
 
 // POST - Upvote a prompt
 export async function POST(
@@ -21,14 +22,11 @@ export async function POST(
     // Check if prompt exists
     const prompt = await db.prompt.findUnique({
       where: { id: promptId },
+      select: { isPrivate: true, authorId: true },
     });
 
-    if (!prompt) {
-      return NextResponse.json(
-        { error: "not_found", message: "Prompt not found" },
-        { status: 404 }
-      );
-    }
+    const denied = await checkPromptAccess(prompt);
+    if (denied) return denied;
 
     // Check if already voted
     const existing = await db.promptVote.findUnique({
@@ -86,6 +84,14 @@ export async function DELETE(
 
     const { id: promptId } = await params;
 
+    const prompt = await db.prompt.findUnique({
+      where: { id: promptId },
+      select: { isPrivate: true, authorId: true },
+    });
+
+    const denied = await checkPromptAccess(prompt);
+    if (denied) return denied;
+
     // Delete vote
     await db.promptVote.deleteMany({
       where: {
diff --git a/src/app/prompts/[id]/page.tsx b/src/app/prompts/[id]/page.tsx
index 42ecda19..e86d593b 100644
--- a/src/app/prompts/[id]/page.tsx
+++ b/src/app/prompts/[id]/page.tsx
@@ -8,6 +8,7 @@ import { AnimatedDate } from "@/components/ui/animated-date";
 import { ShareDropdown } from "@/components/prompts/share-dropdown";
 import { auth } from "@/lib/auth";
 import { db } from "@/lib/db";
+import { canViewPrompt } from "@/lib/prompt-access";
 import { Button } from "@/components/ui/button";
 import { Badge } from "@/components/ui/badge";
 import { Avatar, AvatarFallback, AvatarImage } from "@/components/ui/avatar";
@@ -62,13 +63,20 @@ export async function generateMetadata({ params }: PromptPageProps): Promise<Met
   const id = extractPromptId(idParam);
   const prompt = await db.prompt.findUnique({
     where: { id },
-    select: { title: true, description: true },
+    select: { title: true, description: true, isPrivate: true, authorId: true },
   });
 
   if (!prompt) {
     return { title: "Prompt Not Found" };
   }
 
+  if (prompt.isPrivate) {
+    const session = await auth();
+    if (!canViewPrompt(prompt, session)) {
+      return { title: "Prompt Not Found" };
+    }
+  }
+
   return {
     title: prompt.title,
     description: prompt.description || `View the prompt: ${prompt.title}`,
@@ -224,7 +232,7 @@ export default async function PromptPage({ params }: PromptPageProps) {
   }
 
   // Check if user can view private prompt
-  if (prompt.isPrivate && prompt.authorId !== session?.user?.id) {
+  if (!canViewPrompt(prompt, session)) {
     notFound();
   }
 
diff --git a/src/lib/prompt-access.ts b/src/lib/prompt-access.ts
new file mode 100644
index 00000000..ef216b78
--- /dev/null
+++ b/src/lib/prompt-access.ts
@@ -0,0 +1,49 @@
+import { NextResponse } from "next/server";
+import { auth } from "@/lib/auth";
+import type { Session } from "next-auth";
+
+/**
+ * Check if a user can view a prompt that may be private.
+ * Returns true for public prompts, and for private prompts only if the user is the owner or an admin.
+ */
+export function canViewPrompt(
+  prompt: { isPrivate: boolean; authorId: string } | null,
+  session: Session | null
+): boolean {
+  if (!prompt) return false;
+  if (!prompt.isPrivate) return true;
+  return prompt.authorId === session?.user?.id || session?.user?.role === "ADMIN";
+}
+
+/**
+ * API route guard for prompt privacy. Returns a 404 NextResponse if access is denied, or null if allowed.
+ * Returning 403 is also leak existence of the prompt itself !
+ * Calls auth() lazily — only when the prompt is private.
+ * 
+ *
+ * Usage:
+ *   const denied = await checkPromptAccess(prompt);
+ *   if (denied) return denied;
+ */
+export async function checkPromptAccess(
+  prompt: { isPrivate: boolean; authorId: string } | null
+): Promise<NextResponse | null> {
+  if (!prompt) {
+    return NextResponse.json(
+      { error: "not_found", message: "Prompt not found" },
+      { status: 404 }
+    );
+  }
+
+  if (!prompt.isPrivate) return null;
+
+  const session = await auth();
+  if (!canViewPrompt(prompt, session)) {
+    return NextResponse.json(
+      { error: "not_found", message: "Prompt not found" },
+      { status: 404 }
+    );
+  }
+
+  return null;
+}