diff --git a/lib/sandbox/__tests__/validateSnapshotPatchBody.test.ts b/lib/sandbox/__tests__/validateSnapshotPatchBody.test.ts
index 95ea0631..af6634d8 100644
--- a/lib/sandbox/__tests__/validateSnapshotPatchBody.test.ts
+++ b/lib/sandbox/__tests__/validateSnapshotPatchBody.test.ts
@@ -30,6 +30,7 @@ describe("validateSnapshotPatchBody", () => {
   });
 
   it("returns 401 when auth fails", async () => {
+    vi.mocked(safeParseJson).mockResolvedValue({ snapshotId: "snap_abc123" });
     vi.mocked(validateAuthContext).mockResolvedValue(
       NextResponse.json({ error: "Unauthorized" }, { status: 401 }),
     );
@@ -41,31 +42,24 @@ describe("validateSnapshotPatchBody", () => {
     expect((result as NextResponse).status).toBe(401);
   });
 
-  it("returns validated body with auth context when snapshotId is provided", async () => {
+  it("returns validated body when snapshotId is provided", async () => {
+    vi.mocked(safeParseJson).mockResolvedValue({ snapshotId: "snap_abc123" });
     vi.mocked(validateAuthContext).mockResolvedValue({
       accountId: "acc_123",
       orgId: "org_456",
       authToken: "token",
     });
-    vi.mocked(safeParseJson).mockResolvedValue({ snapshotId: "snap_abc123" });
 
     const request = createMockRequest();
     const result = await validateSnapshotPatchBody(request);
 
     expect(result).toEqual({
       accountId: "acc_123",
-      orgId: "org_456",
-      authToken: "token",
       snapshotId: "snap_abc123",
     });
   });
 
   it("returns error response when snapshotId is missing", async () => {
-    vi.mocked(validateAuthContext).mockResolvedValue({
-      accountId: "acc_123",
-      orgId: null,
-      authToken: "token",
-    });
     vi.mocked(safeParseJson).mockResolvedValue({});
 
     const request = createMockRequest();
@@ -78,17 +72,68 @@ describe("validateSnapshotPatchBody", () => {
   });
 
   it("returns error response when snapshotId is empty string", async () => {
+    vi.mocked(safeParseJson).mockResolvedValue({ snapshotId: "" });
+
+    const request = createMockRequest();
+    const result = await validateSnapshotPatchBody(request);
+
+    expect(result).toBeInstanceOf(NextResponse);
+    expect((result as NextResponse).status).toBe(400);
+  });
+
+  it("passes account_id to validateAuthContext when provided", async () => {
+    const targetAccountId = "550e8400-e29b-41d4-a716-446655440000";
+    vi.mocked(safeParseJson).mockResolvedValue({
+      snapshotId: "snap_abc123",
+      account_id: targetAccountId,
+    });
     vi.mocked(validateAuthContext).mockResolvedValue({
-      accountId: "acc_123",
-      orgId: null,
+      accountId: targetAccountId,
+      orgId: "org_789",
       authToken: "token",
     });
-    vi.mocked(safeParseJson).mockResolvedValue({ snapshotId: "" });
+
+    const request = createMockRequest();
+    const result = await validateSnapshotPatchBody(request);
+
+    expect(validateAuthContext).toHaveBeenCalledWith(request, {
+      accountId: targetAccountId,
+    });
+    expect(result).toEqual({
+      accountId: targetAccountId,
+      snapshotId: "snap_abc123",
+    });
+  });
+
+  it("returns 403 when account_id override is denied", async () => {
+    const unauthorizedAccountId = "660e8400-e29b-41d4-a716-446655440001";
+    vi.mocked(safeParseJson).mockResolvedValue({
+      snapshotId: "snap_abc123",
+      account_id: unauthorizedAccountId,
+    });
+    vi.mocked(validateAuthContext).mockResolvedValue(
+      NextResponse.json({ error: "Access denied to specified account_id" }, { status: 403 }),
+    );
+
+    const request = createMockRequest();
+    const result = await validateSnapshotPatchBody(request);
+
+    expect(result).toBeInstanceOf(NextResponse);
+    expect((result as NextResponse).status).toBe(403);
+  });
+
+  it("returns error when account_id is not a valid UUID", async () => {
+    vi.mocked(safeParseJson).mockResolvedValue({
+      snapshotId: "snap_abc123",
+      account_id: "not-a-uuid",
+    });
 
     const request = createMockRequest();
     const result = await validateSnapshotPatchBody(request);
 
     expect(result).toBeInstanceOf(NextResponse);
     expect((result as NextResponse).status).toBe(400);
+    const json = await (result as NextResponse).json();
+    expect(json.error).toContain("account_id");
   });
 });
diff --git a/lib/sandbox/validateSnapshotPatchBody.ts b/lib/sandbox/validateSnapshotPatchBody.ts
index 9783d7db..08f33c17 100644
--- a/lib/sandbox/validateSnapshotPatchBody.ts
+++ b/lib/sandbox/validateSnapshotPatchBody.ts
@@ -1,18 +1,26 @@
 import type { NextRequest } from "next/server";
 import { NextResponse } from "next/server";
 import { getCorsHeaders } from "@/lib/networking/getCorsHeaders";
-import { validateAuthContext, type AuthContext } from "@/lib/auth/validateAuthContext";
+import { validateAuthContext } from "@/lib/auth/validateAuthContext";
 import { safeParseJson } from "@/lib/networking/safeParseJson";
 import { z } from "zod";
 
 export const snapshotPatchBodySchema = z.object({
   snapshotId: z.string({ message: "snapshotId is required" }).min(1, "snapshotId cannot be empty"),
+  account_id: z.string().uuid("account_id must be a valid UUID").optional(),
 });
 
-export type SnapshotPatchBody = z.infer<typeof snapshotPatchBodySchema> & AuthContext;
+export type SnapshotPatchBody = {
+  /** The account ID to update */
+  accountId: string;
+  /** The snapshot ID to set */
+  snapshotId: string;
+};
 
 /**
  * Validates auth and request body for PATCH /api/sandboxes/snapshot.
+ * Handles authentication via x-api-key or Authorization bearer token,
+ * body validation, and optional account_id override for organization API keys.
  *
  * @param request - The NextRequest object
  * @returns A NextResponse with an error if validation fails, or the validated body with auth context.
@@ -20,11 +28,6 @@ export type SnapshotPatchBody = z.infer<typeof snapshotPatchBodySchema> & AuthCo
 export async function validateSnapshotPatchBody(
   request: NextRequest,
 ): Promise<NextResponse | SnapshotPatchBody> {
-  const authResult = await validateAuthContext(request);
-  if (authResult instanceof NextResponse) {
-    return authResult;
-  }
-
   const body = await safeParseJson(request);
   const result = snapshotPatchBodySchema.safeParse(body);
 
@@ -43,8 +46,18 @@ export async function validateSnapshotPatchBody(
     );
   }
 
+  const { snapshotId, account_id: targetAccountId } = result.data;
+
+  const authResult = await validateAuthContext(request, {
+    accountId: targetAccountId,
+  });
+
+  if (authResult instanceof NextResponse) {
+    return authResult;
+  }
+
   return {
-    ...authResult,
-    ...result.data,
+    accountId: authResult.accountId,
+    snapshotId,
   };
 }