fix: surface server error body on non-2xx responses

Author: SavioBS629

src/lib/apiClient.ts

@@ -152,8 +152,18 @@ class ApiClient {
       const res = await fn(this.axiosAgent);
       return new ApiResponse<T>(res);
     } catch (error: any) {
-      if (error.response && !raise_error) {
-        return new ApiResponse<T>(error.response);
+      if (error.response) {
+        if (!raise_error) {
+          return new ApiResponse<T>(error.response);
+        }
+        const body = error.response.data;
+        const serverMessage =
+          typeof body === "string"
+            ? body
+            : (body?.message ?? body?.error ?? JSON.stringify(body));
+        if (serverMessage) {
+          error.message = `Request failed with status code ${error.response.status}: ${serverMessage}`;
+        }
       }
       throw error;
     }

tests/lib/apiClient.test.ts

@@ -0,0 +1,83 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+const { postMock } = vi.hoisted(() => ({ postMock: vi.fn() }));
+
+vi.mock("axios", () => ({
+  default: {
+    create: () => ({
+      get: vi.fn(),
+      post: postMock,
+      put: vi.fn(),
+      patch: vi.fn(),
+      delete: vi.fn(),
+    }),
+  },
+}));
+
+vi.mock("../../src/config", () => ({
+  default: {
+    browserstackLocalOptions: {},
+  },
+}));
+
+// utils.ts (a transitive import of apiClient) imports trackMCP from index.ts,
+// whose top-level main() would otherwise run on import. Stub it out.
+vi.mock("../../src/index", () => ({
+  trackMCP: vi.fn(),
+}));
+
+import { apiClient } from "../../src/lib/apiClient";
+
+describe("apiClient error surfacing", () => {
+  beforeEach(() => {
+    postMock.mockReset();
+  });
+
+  it("includes the server's JSON error message in the thrown error", async () => {
+    postMock.mockRejectedValueOnce({
+      message: "Request failed with status code 400",
+      response: {
+        status: 400,
+        data: {
+          success: false,
+          message: "Max Testcase IDs supported limit exceeded.",
+        },
+      },
+    });
+
+    await expect(
+      apiClient.post({ url: "https://example.com/api", body: {} }),
+    ).rejects.toMatchObject({
+      message:
+        "Request failed with status code 400: Max Testcase IDs supported limit exceeded.",
+    });
+  });
+
+  it("falls back to a string error body", async () => {
+    postMock.mockRejectedValueOnce({
+      message: "Request failed with status code 422",
+      response: { status: 422, data: "Unprocessable Entity" },
+    });
+
+    await expect(
+      apiClient.post({ url: "https://example.com/api", body: {} }),
+    ).rejects.toMatchObject({
+      message: "Request failed with status code 422: Unprocessable Entity",
+    });
+  });
+
+  it("returns the response instead of throwing when raise_error is false", async () => {
+    postMock.mockRejectedValueOnce({
+      message: "Request failed with status code 400",
+      response: { status: 400, data: { success: false } },
+    });
+
+    const res = await apiClient.post({
+      url: "https://example.com/api",
+      body: {},
+      raise_error: false,
+    });
+    expect(res.status).toBe(400);
+    expect(res.data).toEqual({ success: false });
+  });
+});