diff --git a/db/services/settings.ts b/db/services/settings.ts
index dd2fed9f..6742e944 100644
--- a/db/services/settings.ts
+++ b/db/services/settings.ts
@@ -1,6 +1,7 @@
 import { and, eq } from "drizzle-orm";
 import type { AccessScope } from "@shared/identity/access-scope";
 import { db, settings } from "@db";
+import { ensureScope } from "@db/services/scope";
 
 const gatewayModelKey = "gateway_model";
 const defaultGatewayModel = "openai/gpt-6.1-sol-fast";
@@ -24,6 +25,7 @@ export async function getGatewayModel(scope: AccessScope) {
 }
 
 export async function selectGatewayModel(scope: AccessScope, modelId: string) {
+  await ensureScope(scope);
   await db
     .insert(settings)
     .values({
diff --git a/web/trpc/model-settings.test.ts b/web/trpc/model-settings.test.ts
new file mode 100644
index 00000000..6c06c9c3
--- /dev/null
+++ b/web/trpc/model-settings.test.ts
@@ -0,0 +1,64 @@
+import { PGlite } from "@electric-sql/pglite";
+import { drizzle } from "drizzle-orm/pglite";
+import { migrate } from "drizzle-orm/pglite/migrator";
+import {
+  afterAll,
+  beforeAll,
+  beforeEach,
+  describe,
+  expect,
+  it,
+  vi,
+} from "vitest";
+import * as Database from "@db";
+import * as schema from "@db/schema";
+import { getGatewayModel } from "@db/services/settings";
+import { ensureScope } from "@db/services/scope";
+import { accessScopeForUser } from "@shared/identity/access-scope";
+import { appRouter } from "./router";
+
+const client = new PGlite();
+const database = drizzle(client, { schema });
+const scope = accessScopeForUser("first-model-selection");
+const caller = appRouter.createCaller({ origin: "https://example.com", scope });
+const defaultModel = "openai/gpt-6.1-sol-fast";
+
+beforeAll(async () => {
+  await migrate(database, { migrationsFolder: "db/migrations" });
+  // SAFETY: PGlite implements the real Drizzle query-builder contract; only the database driver is replaced.
+  // oxlint-disable-next-line typescript/no-unsafe-type-assertion -- Real committed migrations and real tRPC/service caller use an owned PostgreSQL-compatible database.
+  vi.spyOn(Database, "db", "get").mockReturnValue(database as never);
+}, 20_000);
+
+beforeEach(async () => {
+  await database.delete(schema.workspaces);
+});
+afterAll(async () => {
+  vi.restoreAllMocks();
+  await client.close();
+});
+
+describe("workspace model selection", () => {
+  it("saves the first model selection before a chat or vault initializes the workspace", async () => {
+    expect(await getGatewayModel(scope)).toBe(defaultModel);
+    expect(await database.select().from(schema.workspaces)).toHaveLength(0);
+    await caller.settings.selectModel({ modelId: defaultModel });
+    expect(await database.select().from(schema.settings)).toMatchObject([
+      { value: defaultModel, workspaceId: scope.workspaceId },
+    ]);
+    expect(
+      await database.select().from(schema.workspaceMemberships)
+    ).toMatchObject([{ userId: scope.userId, workspaceId: scope.workspaceId }]);
+  });
+
+  it("still updates an already initialized workspace without duplicate rows", async () => {
+    await ensureScope(scope);
+    await caller.settings.selectModel({ modelId: defaultModel });
+    await caller.settings.selectModel({ modelId: "meta/muse-spark-1.3" });
+    expect(await getGatewayModel(scope)).toBe("meta/muse-spark-1.3");
+    expect(await database.select().from(schema.settings)).toHaveLength(1);
+    expect(
+      await database.select().from(schema.workspaceMemberships)
+    ).toHaveLength(1);
+  });
+});