diff --git a/client/src/__tests__/App.config.test.tsx b/client/src/__tests__/App.config.test.tsx
new file mode 100644
index 00000000..9b0dedcd
--- /dev/null
+++ b/client/src/__tests__/App.config.test.tsx
@@ -0,0 +1,240 @@
+import React from "react";
+import { render, waitFor } from "@testing-library/react";
+import App from "../App";
+import { DEFAULT_INSPECTOR_CONFIG } from "../lib/constants";
+
+// Mock auth dependencies first
+jest.mock("@modelcontextprotocol/sdk/client/auth.js", () => ({
+  auth: jest.fn(),
+}));
+
+jest.mock("../lib/oauth-state-machine", () => ({
+  OAuthStateMachine: jest.fn(),
+}));
+
+jest.mock("../lib/auth", () => ({
+  InspectorOAuthClientProvider: jest.fn().mockImplementation(() => ({
+    tokens: jest.fn().mockResolvedValue(null),
+    clear: jest.fn(),
+  })),
+  DebugInspectorOAuthClientProvider: jest.fn(),
+}));
+
+// Mock the config utils
+jest.mock("../utils/configUtils", () => ({
+  ...jest.requireActual("../utils/configUtils"),
+  getMCPProxyAddress: jest.fn(() => "http://localhost:6277"),
+  getMCPProxyAuthToken: jest.fn((config) => ({
+    token: config.MCP_PROXY_AUTH_TOKEN.value,
+    header: "X-MCP-Proxy-Auth",
+  })),
+  getInitialTransportType: jest.fn(() => "stdio"),
+  getInitialSseUrl: jest.fn(() => "http://localhost:3001/sse"),
+  getInitialCommand: jest.fn(() => "mcp-server-everything"),
+  getInitialArgs: jest.fn(() => ""),
+  initializeInspectorConfig: jest.fn(() => DEFAULT_INSPECTOR_CONFIG),
+  saveInspectorConfig: jest.fn(),
+}));
+
+// Mock other dependencies
+jest.mock("../lib/hooks/useConnection", () => ({
+  useConnection: () => ({
+    connectionStatus: "disconnected",
+    serverCapabilities: null,
+    mcpClient: null,
+    requestHistory: [],
+    makeRequest: jest.fn(),
+    sendNotification: jest.fn(),
+    handleCompletion: jest.fn(),
+    completionsSupported: false,
+    connect: jest.fn(),
+    disconnect: jest.fn(),
+  }),
+}));
+
+jest.mock("../lib/hooks/useDraggablePane", () => ({
+  useDraggablePane: () => ({
+    height: 300,
+    handleDragStart: jest.fn(),
+  }),
+  useDraggableSidebar: () => ({
+    width: 320,
+    isDragging: false,
+    handleDragStart: jest.fn(),
+  }),
+}));
+
+jest.mock("../components/Sidebar", () => ({
+  __esModule: true,
+  default: () => <div>Sidebar</div>,
+}));
+
+// Mock fetch
+global.fetch = jest.fn();
+
+describe("App - Config Endpoint", () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+    (global.fetch as jest.Mock).mockResolvedValue({
+      json: () =>
+        Promise.resolve({
+          defaultEnvironment: { TEST_ENV: "test" },
+          defaultCommand: "test-command",
+          defaultArgs: "test-args",
+        }),
+    });
+  });
+
+  afterEach(() => {
+    jest.clearAllMocks();
+    
+    // Reset getMCPProxyAuthToken to default behavior
+    const { getMCPProxyAuthToken } = require("../utils/configUtils");
+    getMCPProxyAuthToken.mockImplementation((config) => ({
+      token: config.MCP_PROXY_AUTH_TOKEN.value,
+      header: "X-MCP-Proxy-Auth",
+    }));
+  });
+
+  test("sends X-MCP-Proxy-Auth header when fetching config with proxy auth token", async () => {
+    const mockConfig = {
+      ...DEFAULT_INSPECTOR_CONFIG,
+      MCP_PROXY_AUTH_TOKEN: {
+        ...DEFAULT_INSPECTOR_CONFIG.MCP_PROXY_AUTH_TOKEN,
+        value: "test-proxy-token",
+      },
+    };
+
+    // Mock initializeInspectorConfig to return our test config
+    const { initializeInspectorConfig } = require("../utils/configUtils");
+    initializeInspectorConfig.mockReturnValue(mockConfig);
+
+    render(<App />);
+
+    await waitFor(() => {
+      expect(global.fetch).toHaveBeenCalledWith(
+        "http://localhost:6277/config",
+        {
+          headers: {
+            "X-MCP-Proxy-Auth": "Bearer test-proxy-token",
+          },
+        }
+      );
+    });
+  });
+
+  test("does not send auth header when proxy auth token is empty", async () => {
+    const mockConfig = {
+      ...DEFAULT_INSPECTOR_CONFIG,
+      MCP_PROXY_AUTH_TOKEN: {
+        ...DEFAULT_INSPECTOR_CONFIG.MCP_PROXY_AUTH_TOKEN,
+        value: "",
+      },
+    };
+
+    // Mock initializeInspectorConfig to return our test config
+    const { initializeInspectorConfig } = require("../utils/configUtils");
+    initializeInspectorConfig.mockReturnValue(mockConfig);
+
+    render(<App />);
+
+    await waitFor(() => {
+      expect(global.fetch).toHaveBeenCalledWith(
+        "http://localhost:6277/config",
+        {
+          headers: {},
+        }
+      );
+    });
+  });
+
+  test("uses custom header name if getMCPProxyAuthToken returns different header", async () => {
+    const mockConfig = {
+      ...DEFAULT_INSPECTOR_CONFIG,
+      MCP_PROXY_AUTH_TOKEN: {
+        ...DEFAULT_INSPECTOR_CONFIG.MCP_PROXY_AUTH_TOKEN,
+        value: "test-proxy-token",
+      },
+    };
+
+    // Mock to return a custom header name
+    const { getMCPProxyAuthToken, initializeInspectorConfig } = require("../utils/configUtils");
+    getMCPProxyAuthToken.mockReturnValue({
+      token: "test-proxy-token",
+      header: "X-Custom-Auth",
+    });
+    initializeInspectorConfig.mockReturnValue(mockConfig);
+
+    render(<App />);
+
+    await waitFor(() => {
+      expect(global.fetch).toHaveBeenCalledWith(
+        "http://localhost:6277/config",
+        {
+          headers: {
+            "X-Custom-Auth": "Bearer test-proxy-token",
+          },
+        }
+      );
+    });
+  });
+
+  test("config endpoint response updates app state", async () => {
+    const mockConfig = {
+      ...DEFAULT_INSPECTOR_CONFIG,
+      MCP_PROXY_AUTH_TOKEN: {
+        ...DEFAULT_INSPECTOR_CONFIG.MCP_PROXY_AUTH_TOKEN,
+        value: "test-proxy-token",
+      },
+    };
+
+    const { initializeInspectorConfig } = require("../utils/configUtils");
+    initializeInspectorConfig.mockReturnValue(mockConfig);
+
+    const { container } = render(<App />);
+
+    await waitFor(() => {
+      expect(global.fetch).toHaveBeenCalledTimes(1);
+    });
+
+    // Verify the fetch was called with correct parameters
+    expect(global.fetch).toHaveBeenCalledWith(
+      "http://localhost:6277/config",
+      expect.objectContaining({
+        headers: expect.objectContaining({
+          "X-MCP-Proxy-Auth": "Bearer test-proxy-token",
+        }),
+      })
+    );
+  });
+
+  test("handles config endpoint errors gracefully", async () => {
+    const mockConfig = {
+      ...DEFAULT_INSPECTOR_CONFIG,
+      MCP_PROXY_AUTH_TOKEN: {
+        ...DEFAULT_INSPECTOR_CONFIG.MCP_PROXY_AUTH_TOKEN,
+        value: "test-proxy-token",
+      },
+    };
+
+    const { initializeInspectorConfig } = require("../utils/configUtils");
+    initializeInspectorConfig.mockReturnValue(mockConfig);
+
+    // Mock fetch to reject
+    (global.fetch as jest.Mock).mockRejectedValue(new Error("Network error"));
+
+    // Spy on console.error
+    const consoleErrorSpy = jest.spyOn(console, "error").mockImplementation();
+
+    render(<App />);
+
+    await waitFor(() => {
+      expect(consoleErrorSpy).toHaveBeenCalledWith(
+        "Error fetching default environment:",
+        expect.any(Error)
+      );
+    });
+
+    consoleErrorSpy.mockRestore();
+  });
+});
\ No newline at end of file
diff --git a/client/src/utils/__tests__/configUtils.test.ts b/client/src/utils/__tests__/configUtils.test.ts
new file mode 100644
index 00000000..38ce163b
--- /dev/null
+++ b/client/src/utils/__tests__/configUtils.test.ts
@@ -0,0 +1,72 @@
+import { getMCPProxyAuthToken } from "../configUtils";
+import { DEFAULT_INSPECTOR_CONFIG } from "../../lib/constants";
+import { InspectorConfig } from "../../lib/configurationTypes";
+
+describe("configUtils", () => {
+  describe("getMCPProxyAuthToken", () => {
+    test("returns token and default header name", () => {
+      const config: InspectorConfig = {
+        ...DEFAULT_INSPECTOR_CONFIG,
+        MCP_PROXY_AUTH_TOKEN: {
+          ...DEFAULT_INSPECTOR_CONFIG.MCP_PROXY_AUTH_TOKEN,
+          value: "test-token-123",
+        },
+      };
+
+      const result = getMCPProxyAuthToken(config);
+
+      expect(result).toEqual({
+        token: "test-token-123",
+        header: "X-MCP-Proxy-Auth",
+      });
+    });
+
+    test("returns empty token when not configured", () => {
+      const config: InspectorConfig = {
+        ...DEFAULT_INSPECTOR_CONFIG,
+        MCP_PROXY_AUTH_TOKEN: {
+          ...DEFAULT_INSPECTOR_CONFIG.MCP_PROXY_AUTH_TOKEN,
+          value: "",
+        },
+      };
+
+      const result = getMCPProxyAuthToken(config);
+
+      expect(result).toEqual({
+        token: "",
+        header: "X-MCP-Proxy-Auth",
+      });
+    });
+
+    test("always returns X-MCP-Proxy-Auth as header name", () => {
+      const config: InspectorConfig = {
+        ...DEFAULT_INSPECTOR_CONFIG,
+        MCP_PROXY_AUTH_TOKEN: {
+          ...DEFAULT_INSPECTOR_CONFIG.MCP_PROXY_AUTH_TOKEN,
+          value: "any-token",
+        },
+      };
+
+      const result = getMCPProxyAuthToken(config);
+
+      expect(result.header).toBe("X-MCP-Proxy-Auth");
+    });
+
+    test("handles null/undefined value gracefully", () => {
+      const config: InspectorConfig = {
+        ...DEFAULT_INSPECTOR_CONFIG,
+        MCP_PROXY_AUTH_TOKEN: {
+          ...DEFAULT_INSPECTOR_CONFIG.MCP_PROXY_AUTH_TOKEN,
+          value: null as any,
+        },
+      };
+
+      const result = getMCPProxyAuthToken(config);
+
+      expect(result).toEqual({
+        token: null,
+        header: "X-MCP-Proxy-Auth",
+      });
+    });
+  });
+});
\ No newline at end of file