diff --git a/src/Frontend/src/AuthApp.vue b/src/Frontend/src/AuthApp.vue
index 558e74faa3..af9dba5422 100644
--- a/src/Frontend/src/AuthApp.vue
+++ b/src/Frontend/src/AuthApp.vue
@@ -6,11 +6,12 @@ import { useAuthStore } from "@/stores/AuthStore";
 import routeLinks from "@/router/routeLinks";
 import LoadingSpinner from "@/components/LoadingSpinner.vue";
 import App from "./App.vue";
+import AuthErrorScreen from "@/components/AuthErrorScreen.vue";
 import logger from "@/logger";
 
 const { authenticate } = useAuth();
 const authStore = useAuthStore();
-const { isAuthenticating, loading } = storeToRefs(authStore);
+const { isAuthenticating, loading, authError } = storeToRefs(authStore);
 
 onMounted(async () => {
   try {
@@ -56,6 +57,7 @@ onMounted(async () => {
     <LoadingSpinner />
     <div class="loading-text">Authenticating...</div>
   </div>
+  <AuthErrorScreen v-else-if="authError" :error="authError" />
   <App v-else />
 </template>
 
diff --git a/src/Frontend/src/components/AuthErrorScreen.spec.ts b/src/Frontend/src/components/AuthErrorScreen.spec.ts
new file mode 100644
index 0000000000..3bb4bef77a
--- /dev/null
+++ b/src/Frontend/src/components/AuthErrorScreen.spec.ts
@@ -0,0 +1,26 @@
+import { expect, test, describe, render, screen } from "@component-test-utils";
+
+import AuthErrorScreen from "./AuthErrorScreen.vue";
+
+describe("AuthErrorScreen", () => {
+  test("shows scope-specific guidance and the raw detail for invalid_scope", async () => {
+    render(AuthErrorScreen, {
+      props: {
+        error: { code: "invalid_scope", description: "Invalid scopes: Pulse openid profile email offline_access" },
+      },
+    });
+
+    expect(await screen.findByText("Unable to sign in")).toBeVisible();
+    expect(screen.getByText(/'offline_access' scope may be disabled/)).toBeVisible();
+    expect(screen.getByText(/Invalid scopes: Pulse openid profile email offline_access/)).toBeVisible();
+  });
+
+  test("shows a generic message and the raw detail for an error without a recognized code", async () => {
+    render(AuthErrorScreen, {
+      props: { error: { description: "Callback failed" } },
+    });
+
+    expect(await screen.findByText(/Contact your administrator/)).toBeVisible();
+    expect(screen.getByText(/Callback failed/)).toBeVisible();
+  });
+});
diff --git a/src/Frontend/src/components/AuthErrorScreen.vue b/src/Frontend/src/components/AuthErrorScreen.vue
new file mode 100644
index 0000000000..b0ee4ef5fb
--- /dev/null
+++ b/src/Frontend/src/components/AuthErrorScreen.vue
@@ -0,0 +1,62 @@
+<script setup lang="ts">
+import { computed } from "vue";
+import type { AuthError } from "@/types/auth";
+import { describeAuthError } from "@/composables/authError";
+
+const props = defineProps<{
+  error: AuthError;
+}>();
+
+const display = computed(() => describeAuthError(props.error));
+</script>
+
+<template>
+  <div class="auth-error-container">
+    <div class="auth-error-content">
+      <h1 class="auth-error-title">{{ display.title }}</h1>
+      <p class="auth-error-message">{{ display.message }}</p>
+      <p class="auth-error-detail" role="status">Details: {{ props.error.description }}</p>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+/* Modeled on LoggedOutView.vue for a consistent full-screen auth surface. */
+.auth-error-container {
+  display: flex;
+  justify-content: center;
+  align-items: center;
+  min-height: 100vh;
+  background-color: #f5f5f5;
+  padding: 20px;
+}
+
+.auth-error-content {
+  text-align: center;
+  background: white;
+  padding: 60px 40px;
+  border-radius: 8px;
+  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
+  max-width: 500px;
+  width: 100%;
+}
+
+.auth-error-title {
+  font-size: 24px;
+  font-weight: 600;
+  color: #333;
+  margin-bottom: 16px;
+}
+
+.auth-error-message {
+  font-size: 16px;
+  color: #666;
+  margin-bottom: 24px;
+}
+
+.auth-error-detail {
+  font-size: 13px;
+  color: #999;
+  word-break: break-word;
+}
+</style>
diff --git a/src/Frontend/src/composables/authError.spec.ts b/src/Frontend/src/composables/authError.spec.ts
new file mode 100644
index 0000000000..cca122c640
--- /dev/null
+++ b/src/Frontend/src/composables/authError.spec.ts
@@ -0,0 +1,23 @@
+import { describe, test, expect } from "vitest";
+import { describeAuthError } from "@/composables/authError";
+
+describe("describeAuthError", () => {
+  test("gives scope-specific guidance for invalid_scope", () => {
+    const result = describeAuthError({
+      code: "invalid_scope",
+      description: "Invalid scopes: Pulse openid profile email offline_access",
+    });
+    expect(result.title).toBe("Unable to sign in");
+    expect(result.message).toContain("offline_access");
+  });
+
+  test("gives a generic message for an unrecognized code", () => {
+    const result = describeAuthError({ code: "server_error", description: "server_error" });
+    expect(result.message).toContain("Contact your administrator");
+  });
+
+  test("gives a generic message when there is no code", () => {
+    const result = describeAuthError({ description: "Callback failed" });
+    expect(result.message).toContain("Contact your administrator");
+  });
+});
diff --git a/src/Frontend/src/composables/authError.ts b/src/Frontend/src/composables/authError.ts
new file mode 100644
index 0000000000..89ee75bbae
--- /dev/null
+++ b/src/Frontend/src/composables/authError.ts
@@ -0,0 +1,27 @@
+import type { AuthError } from "@/types/auth";
+
+export interface AuthErrorDisplay {
+  title: string;
+  message: string;
+}
+
+/**
+ * Maps a captured authentication failure to user-facing copy. Recognised OAuth error codes get
+ * specific, actionable guidance; everything else — including local/callback exceptions with no
+ * code — gets a generic message. The raw `error.description` is rendered separately by the
+ * component, so it is not repeated here.
+ */
+export function describeAuthError(error: AuthError): AuthErrorDisplay {
+  switch (error.code) {
+    case "invalid_scope":
+      return {
+        title: "Unable to sign in",
+        message: "Your identity provider rejected one or more of the requested scopes. The 'offline_access' scope may be disabled in your IdP, ask your administrator to enable it or update ServiceControl so ServicePulse does not request it.",
+      };
+    default:
+      return {
+        title: "Unable to sign in",
+        message: "Something went wrong while signing you in. Contact your administrator if the problem continues.",
+      };
+  }
+}
diff --git a/src/Frontend/src/composables/useAuth.ts b/src/Frontend/src/composables/useAuth.ts
index 8bc2694aa1..999fd62ccf 100644
--- a/src/Frontend/src/composables/useAuth.ts
+++ b/src/Frontend/src/composables/useAuth.ts
@@ -29,7 +29,7 @@ export function useAuth() {
       await userManager?.signinRedirect();
     } catch (error) {
       logger.error("Re-authentication after session loss failed:", error);
-      authStore.setAuthError(error instanceof Error ? error.message : "Re-authentication after session loss failed");
+      authStore.setAuthError({ description: error instanceof Error ? error.message : "Re-authentication after session loss failed" });
     } finally {
       authStore.setAuthenticating(false);
     }
@@ -116,7 +116,7 @@ export function useAuth() {
             errorMessage: error instanceof Error ? error.message : "Unknown error",
             errorStack: error instanceof Error ? error.stack : undefined,
           });
-          authStore.setAuthError(error instanceof Error ? error.message : "Callback failed");
+          authStore.setAuthError({ description: error instanceof Error ? error.message : "Callback failed" });
           // Don't continue - callback failed, user needs to try again
           return false;
         } finally {
@@ -124,9 +124,10 @@ export function useAuth() {
         }
       } else if (hasError) {
         // OAuth error in callback
+        const errorCode = params.get("error") ?? undefined;
         const errorDescription = params.get("error_description") || params.get("error");
         logger.error("OAuth error:", errorDescription);
-        authStore.setAuthError(errorDescription || "Authentication failed");
+        authStore.setAuthError({ code: errorCode, description: errorDescription || "Authentication failed" });
         return false;
       }
 
@@ -144,7 +145,7 @@ export function useAuth() {
     } catch (error) {
       authStore.setAuthenticating(false);
       const errorMessage = error instanceof Error ? error.message : "Unknown authentication error";
-      authStore.setAuthError(errorMessage);
+      authStore.setAuthError({ description: errorMessage });
       logger.error("Authentication error:", error);
       throw error;
     }
diff --git a/src/Frontend/src/stores/AuthStore.spec.ts b/src/Frontend/src/stores/AuthStore.spec.ts
new file mode 100644
index 0000000000..fd140bddc6
--- /dev/null
+++ b/src/Frontend/src/stores/AuthStore.spec.ts
@@ -0,0 +1,47 @@
+import { beforeEach, describe, expect, test, vi } from "vitest";
+import { createPinia, setActivePinia } from "pinia";
+import serviceControlClient from "@/components/serviceControlClient";
+import { useAuthStore } from "@/stores/AuthStore";
+
+describe("AuthStore tests", () => {
+  const baseResponse = {
+    enabled: true,
+    role_based_authorization_enabled: true,
+    client_id: "test-client-id",
+    authority: "https://login.example.com",
+    api_scopes: JSON.stringify(["api://test-audience/.default"]),
+    audience: "api://test-audience",
+  };
+
+  beforeEach(() => {
+    setActivePinia(createPinia());
+  });
+
+  test("uses the composed scopes field from ServiceControl when present", async () => {
+    // The store must pass `scopes` through untouched. This value deliberately differs from anything
+    // derivable from api_scopes (a different scope, and no offline_access) so the test fails if the
+    // store ever reverts to assembling the scope string itself instead of trusting ServiceControl.
+    vi.spyOn(serviceControlClient, "fetchTypedFromServiceControl").mockResolvedValue([
+      {} as Response,
+      {
+        ...baseResponse,
+        scopes: "api://servicecontrol/composed-by-servicecontrol openid profile email",
+      },
+    ]);
+
+    const store = useAuthStore();
+    await store.refresh();
+
+    expect(store.authConfig?.scope).toBe("api://servicecontrol/composed-by-servicecontrol openid profile email");
+  });
+
+  test("falls back to assembling scopes from api_scopes when talking to an older ServiceControl", async () => {
+    // Older ServiceControl versions don't send the `scopes` field at all.
+    vi.spyOn(serviceControlClient, "fetchTypedFromServiceControl").mockResolvedValue([{} as Response, { ...baseResponse }]);
+
+    const store = useAuthStore();
+    await store.refresh();
+
+    expect(store.authConfig?.scope).toBe("api://test-audience/.default openid profile email offline_access");
+  });
+});
diff --git a/src/Frontend/src/stores/AuthStore.ts b/src/Frontend/src/stores/AuthStore.ts
index 64c4012136..1a81418498 100644
--- a/src/Frontend/src/stores/AuthStore.ts
+++ b/src/Frontend/src/stores/AuthStore.ts
@@ -1,7 +1,7 @@
 import { acceptHMRUpdate, defineStore } from "pinia";
 import logger from "@/logger";
 import { ref } from "vue";
-import type { AuthConfig } from "@/types/auth";
+import type { AuthConfig, AuthError } from "@/types/auth";
 import { WebStorageStateStore } from "oidc-client-ts";
 import routeLinks from "@/router/routeLinks";
 import serviceControlClient from "@/components/serviceControlClient";
@@ -14,13 +14,17 @@ interface AuthConfigResponse {
   authority: string;
   api_scopes: string;
   audience: string;
+  // Complete scope string composed by ServiceControl (api scopes + openid profile email + offline_access,
+  // the last omitted if the operator disabled it). Absent on ServiceControl versions older than the one
+  // that introduced this field, in which case we fall back to assembling it ourselves below.
+  scopes?: string;
 }
 
 export const useAuthStore = defineStore("auth", () => {
   const token = ref<string | null>(null);
   const isAuthenticated = ref(false);
   const isAuthenticating = ref(false);
-  const authError = ref<string | null>(null);
+  const authError = ref<AuthError | null>(null);
   const authConfig = ref<AuthConfig | null>(null);
   const authEnabled = ref(false);
   // undefined means ServiceControl didn't report this field (older version) — treat as enabled.
@@ -52,7 +56,11 @@ export const useAuthStore = defineStore("auth", () => {
   }
 
   function transformToAuthConfig(config: AuthConfigResponse): AuthConfig {
+    // ServiceControl composes the full scope string (including whether offline_access is permitted
+    // by the identity provider). Older ServiceControl versions don't send it, so fall back to the
+    // previous behaviour of assembling it from api_scopes.
     const apiScope = JSON.parse(config.api_scopes).join(" ");
+    const scope = config.scopes ?? `${apiScope} openid profile email offline_access`;
     // Use hash-based URL for post-logout redirect since the app uses hash routing
     const postLogoutRedirectUri = `${window.location.origin}${window.location.pathname}#${routeLinks.loggedOut}`;
     return {
@@ -61,7 +69,7 @@ export const useAuthStore = defineStore("auth", () => {
       redirect_uri: window.location.origin,
       post_logout_redirect_uri: postLogoutRedirectUri,
       response_type: "code",
-      scope: `${apiScope} openid profile email offline_access`,
+      scope,
       automaticSilentRenew: true,
       loadUserInfo: false,
       includeIdTokenInSilentRenew: true,
@@ -102,7 +110,7 @@ export const useAuthStore = defineStore("auth", () => {
     isAuthenticating.value = value;
   }
 
-  function setAuthError(error: string | null) {
+  function setAuthError(error: AuthError | null) {
     authError.value = error;
   }
 
diff --git a/src/Frontend/src/types/auth.ts b/src/Frontend/src/types/auth.ts
index cdcafba80f..9e1bc96a34 100644
--- a/src/Frontend/src/types/auth.ts
+++ b/src/Frontend/src/types/auth.ts
@@ -5,3 +5,15 @@ import type { UserManagerSettings } from "oidc-client-ts";
  * This provides type-safe configuration for any OIDC-compliant identity provider
  */
 export type AuthConfig = UserManagerSettings;
+
+/**
+ * A captured authentication failure.
+ * `code` is the OAuth error code from an identity-provider error redirect (e.g. "invalid_scope");
+ * it is absent for local/callback exceptions that carry no OAuth code.
+ * `description` is the human-readable detail (the IdP's error_description or an exception message)
+ * and is always shown to the user.
+ */
+export interface AuthError {
+  code?: string;
+  description: string;
+}
diff --git a/src/Frontend/test/specs/authentication/auth-callback-error.spec.ts b/src/Frontend/test/specs/authentication/auth-callback-error.spec.ts
index 218a4e1d46..a26adca737 100644
--- a/src/Frontend/test/specs/authentication/auth-callback-error.spec.ts
+++ b/src/Frontend/test/specs/authentication/auth-callback-error.spec.ts
@@ -52,7 +52,7 @@ describe("FEATURE: OAuth Callback Error Handling (Scenario 16)", () => {
       });
 
       // Verify the error message contains the description
-      expect(authStore.authError).toContain("cancelled");
+      expect(authStore.authError?.description).toContain("cancelled");
 
       // User should not be authenticated
       expect(authStore.isAuthenticated).toBe(false);
@@ -94,7 +94,7 @@ describe("FEATURE: OAuth Callback Error Handling (Scenario 16)", () => {
       });
 
       // Verify the error captures the description
-      expect(authStore.authError).toContain("Missing");
+      expect(authStore.authError?.description).toContain("Missing");
 
       // User should not be authenticated
       expect(authStore.isAuthenticated).toBe(false);
@@ -136,7 +136,7 @@ describe("FEATURE: OAuth Callback Error Handling (Scenario 16)", () => {
       });
 
       // When no description, the error code should be used
-      expect(authStore.authError).toBe("server_error");
+      expect(authStore.authError?.description).toBe("server_error");
 
       // User should not be authenticated
       expect(authStore.isAuthenticated).toBe(false);
@@ -148,5 +148,44 @@ describe("FEATURE: OAuth Callback Error Handling (Scenario 16)", () => {
         configurable: true,
       });
     });
+
+    test("EXAMPLE: invalid_scope error captures the OAuth error code", async ({ driver }) => {
+      const mockSearch = "?error=invalid_scope&error_description=Invalid%20scopes%3A%20Pulse%20openid%20profile%20email%20offline_access";
+
+      const mockLocation = {
+        ...originalLocation,
+        search: mockSearch,
+        hash: "#/dashboard",
+        href: `http://localhost:5173${mockSearch}#/dashboard`,
+      };
+
+      Object.defineProperty(window, "location", {
+        value: mockLocation,
+        writable: true,
+        configurable: true,
+      });
+
+      await driver.setUp(precondition.serviceControlWithMonitoring);
+      await driver.setUp(precondition.hasAuthenticationEnabled());
+
+      await driver.goTo("/dashboard");
+
+      const authStore = useAuthStore();
+
+      await waitFor(() => {
+        expect(authStore.authError).toBeTruthy();
+      });
+
+      expect(authStore.authError?.code).toBe("invalid_scope");
+      expect(authStore.authError?.description).toContain("Invalid scopes");
+
+      expect(authStore.isAuthenticated).toBe(false);
+
+      Object.defineProperty(window, "location", {
+        value: originalLocation,
+        writable: true,
+        configurable: true,
+      });
+    });
   });
 });