diff --git a/frontend/src/core/artifacts/loader.ts b/frontend/src/core/artifacts/loader.ts
index afcf70a6a..eb8e8a92f 100644
--- a/frontend/src/core/artifacts/loader.ts
+++ b/frontend/src/core/artifacts/loader.ts
@@ -1,5 +1,7 @@
 import type { BaseStream } from "@langchain/langgraph-sdk/react";
 
+import { fetch } from "@/core/api/fetcher";
+
 import type { AgentThreadState } from "../threads";
 
 import { buildWriteFileDraftContent } from "./preview";
diff --git a/frontend/src/core/models/api.ts b/frontend/src/core/models/api.ts
index d924e3529..8af78089e 100644
--- a/frontend/src/core/models/api.ts
+++ b/frontend/src/core/models/api.ts
@@ -1,3 +1,6 @@
+import { throwGatewayApiError } from "@/core/api/errors";
+import { fetch } from "@/core/api/fetcher";
+
 import { getBackendBaseURL } from "../config";
 import { isStaticWebsiteOnly } from "../static-mode";
 
@@ -14,6 +17,12 @@ export async function loadModels(): Promise<ModelsResponse> {
   }
 
   const res = await fetch(`${getBackendBaseURL()}/api/models`);
+  if (!res.ok) {
+    await throwGatewayApiError(
+      res,
+      `Failed to load models: ${res.status} ${res.statusText}`.trim(),
+    );
+  }
   const data = (await res.json()) as Partial<ModelsResponse>;
   return {
     models: data.models ?? [],
diff --git a/frontend/src/core/workspace-changes/api.ts b/frontend/src/core/workspace-changes/api.ts
index 34577d472..b175db728 100644
--- a/frontend/src/core/workspace-changes/api.ts
+++ b/frontend/src/core/workspace-changes/api.ts
@@ -1,3 +1,4 @@
+import { fetch } from "@/core/api/fetcher";
 import { getBackendBaseURL } from "@/core/config";
 
 import type { WorkspaceChangesResponse } from "./types";
diff --git a/frontend/tests/unit/core/artifacts/loader.test.ts b/frontend/tests/unit/core/artifacts/loader.test.ts
index b8aee01b4..ca2947e1e 100644
--- a/frontend/tests/unit/core/artifacts/loader.test.ts
+++ b/frontend/tests/unit/core/artifacts/loader.test.ts
@@ -51,6 +51,7 @@ describe("loadArtifactContent", () => {
       expect(new Headers(init?.headers).get("Range")).toBe(
         `bytes=0-${ARTIFACT_PREVIEW_MAX_BYTES - 1}`,
       );
+      expect(init?.credentials).toBe("include");
       return new Response(bytes, {
         status: 206,
         headers: {
diff --git a/frontend/tests/unit/core/models/api.test.ts b/frontend/tests/unit/core/models/api.test.ts
new file mode 100644
index 000000000..ca1ca28cf
--- /dev/null
+++ b/frontend/tests/unit/core/models/api.test.ts
@@ -0,0 +1,71 @@
+import { afterEach, expect, test, rs } from "@rstest/core";
+
+afterEach(() => {
+  rs.unstubAllGlobals();
+});
+
+test("loadModels includes credentials for authenticated gateway requests", async () => {
+  let requestedInit: RequestInit | undefined;
+  const fetchMock = rs.fn(
+    async (_input: RequestInfo | URL, init?: RequestInit) => {
+      requestedInit = init;
+      return new Response(
+        JSON.stringify({
+          models: [
+            {
+              id: "model-1",
+              name: "model-1",
+              model: "model-1",
+              display_name: "Model 1",
+            },
+          ],
+          token_usage: { enabled: true },
+        }),
+        { status: 200 },
+      );
+    },
+  );
+  rs.stubGlobal("fetch", fetchMock);
+
+  const { loadModels } = await import("@/core/models/api");
+
+  await expect(loadModels()).resolves.toMatchObject({
+    models: [{ id: "model-1" }],
+    token_usage: { enabled: true },
+  });
+  expect(requestedInit?.credentials).toBe("include");
+});
+
+test("loadModels rejects unsuccessful gateway responses", async () => {
+  rs.stubGlobal(
+    "fetch",
+    rs.fn(
+      async () =>
+        new Response(JSON.stringify({ detail: "Model registry unavailable" }), {
+          status: 503,
+          statusText: "Service Unavailable",
+        }),
+    ),
+  );
+
+  const { loadModels } = await import("@/core/models/api");
+
+  await expect(loadModels()).rejects.toThrow("Model registry unavailable");
+});
+
+test("loadModels includes the status code when statusText is empty", async () => {
+  rs.stubGlobal(
+    "fetch",
+    rs.fn(
+      async () =>
+        new Response("upstream unavailable", {
+          status: 503,
+          statusText: "",
+        }),
+    ),
+  );
+
+  const { loadModels } = await import("@/core/models/api");
+
+  await expect(loadModels()).rejects.toThrow("Failed to load models: 503");
+});
diff --git a/frontend/tests/unit/core/workspace-changes/api.test.ts b/frontend/tests/unit/core/workspace-changes/api.test.ts
index 4ff402df1..0b5dcb2d8 100644
--- a/frontend/tests/unit/core/workspace-changes/api.test.ts
+++ b/frontend/tests/unit/core/workspace-changes/api.test.ts
@@ -47,4 +47,8 @@ test("fetchWorkspaceChanges can request file metadata without diffs", async () =
   const url = new URL(requestedUrl, "http://localhost");
   expect(url.searchParams.get("include_files")).toBe("true");
   expect(url.searchParams.get("include_diff")).toBe("false");
+  expect(fetchMock).toHaveBeenCalledWith(
+    expect.any(String),
+    expect.objectContaining({ credentials: "include" }),
+  );
 });