diff --git a/frontend/src/lib/api/client.ts b/frontend/src/lib/api/client.ts
index d9024c67..8bffc24d 100644
--- a/frontend/src/lib/api/client.ts
+++ b/frontend/src/lib/api/client.ts
@@ -48,6 +48,13 @@ export interface ApiClientDeps {
 	rawFetch: FetchFn;
 	/** Invoked once when a refresh definitively fails (clear session + redirect). */
 	onSessionExpired: () => void;
+	/**
+	 * Invoked when the server returns `403 { error_type: "PasswordChangeRequired" }`.
+	 * Typically routes the SPA to `/profile?forcePasswordChange=1` — the same
+	 * destination the root layout's nav-guard uses for a fresh navigation. Default
+	 * is a no-op; the app wires the real handler at startup.
+	 */
+	onPasswordChangeRequired?: () => void;
 	/** Test seam for `window.location.origin`. */
 	origin?: string;
 }
@@ -77,6 +84,10 @@ function bypassesRetry(urlStr: string): boolean {
  */
 export function createApiFetch(deps: ApiClientDeps): FetchFn {
 	const { rawFetch, onSessionExpired } = deps;
+	// Default no-op keeps existing test callers that don't wire this
+	// dep from crashing on a 403 PasswordChangeRequired — they'd just
+	// see the raw 403 flow through, which is what they already assert.
+	const onPasswordChangeRequired = deps.onPasswordChangeRequired ?? (() => {});
 	let refreshInFlight: Promise<boolean> | null = null;
 
 	async function refresh(): Promise<boolean> {
@@ -114,6 +125,32 @@ export function createApiFetch(deps: ApiClientDeps): FetchFn {
 		// refresh doesn't accidentally clear a live banner.
 		updateFromHeader(response.headers.get(SERVER_STATUS_HEADER));
 
+		// Backend `require_no_password_change_pending_layer` returns 403
+		// `PasswordChangeRequired` on every non-allowlisted endpoint
+		// while the caller's `force_password_change_at_next_login` flag
+		// is set (admin picked a temporary password). Intercepting here
+		// short-circuits any stale-tab request that outran the SPA's
+		// nav-guard — the user is bounced to `/profile` in mandatory
+		// mode, matching what the guard would do on a fresh navigation.
+		//
+		// Clones the body so downstream callers can still consume the
+		// response after we've peeked at the error_type. Skipped for
+		// non-JSON responses (WebDAV, etc.) — the check silently
+		// falls through and returns the original 403 to the caller,
+		// which will surface its own error the usual way.
+		if (response.status === 403) {
+			const clone = response.clone();
+			try {
+				const body = (await clone.json()) as { error_type?: unknown };
+				if (body?.error_type === 'PasswordChangeRequired') {
+					onPasswordChangeRequired();
+				}
+			} catch {
+				/* not JSON or parse failed — pass through as normal 403 */
+			}
+			return response;
+		}
+
 		if (response.status !== 401) return response;
 
 		const urlStr = urlString(input as RequestInfo | URL);
@@ -146,13 +183,35 @@ export function setSessionExpiredHandler(fn: () => void): void {
 	sessionExpiredHandler = fn;
 }
 
+// Same shape as `sessionExpiredHandler` — mutable so the app can install
+// the real behaviour post-mount, and a fallback for the (rare) case
+// where no handler is wired yet (bootstrap, tests). The fallback does
+// a hard `window.location` navigation so a stale tab that outran the
+// SPA's nav-guard still lands the user on the mandatory form.
+let passwordChangeRequiredHandler: () => void = () => {
+	if (typeof window !== 'undefined') {
+		const here = encodeURIComponent(window.location.pathname + window.location.search);
+		window.location.href = `/profile?forcePasswordChange=1&next=${here}`;
+	}
+};
+
+/**
+ * Wire the SPA's mandatory-mode handler. Called once from the root
+ * layout: uses `goto()` for a soft nav so `next=` preserves the
+ * intended destination without triggering a full page reload.
+ */
+export function setPasswordChangeRequiredHandler(fn: () => void): void {
+	passwordChangeRequiredHandler = fn;
+}
+
 const rawFetch: FetchFn =
 	typeof globalThis.fetch === 'function' ? globalThis.fetch.bind(globalThis) : (undefined as never);
 
 /** App-wide fetch — route every API call through this. */
 export const apiFetch: FetchFn = createApiFetch({
 	rawFetch,
-	onSessionExpired: () => sessionExpiredHandler()
+	onSessionExpired: () => sessionExpiredHandler(),
+	onPasswordChangeRequired: () => passwordChangeRequiredHandler()
 });
 
 /** Convenience: fetch JSON, throwing on non-2xx. */
diff --git a/frontend/src/lib/api/types.ts b/frontend/src/lib/api/types.ts
index b3907220..3b2c03c6 100644
--- a/frontend/src/lib/api/types.ts
+++ b/frontend/src/lib/api/types.ts
@@ -216,6 +216,17 @@ export interface User {
 	 * delete it from the bag.
 	 */
 	ui_preferences: Record<string, unknown>;
+	/**
+	 * Mirrors `auth.users.force_password_change_at_next_login`. Only
+	 * populated by `GET /api/auth/me` (see the backend UserDto doc for
+	 * why other UserDto call-sites default to false). When true, the
+	 * SPA MUST lock navigation to the password-change surface — the
+	 * root layout's guard + the backend's `require_no_password_change_pending`
+	 * middleware together enforce this. Optional on the wire because
+	 * older backend builds omit it and `#[serde(default)]` maps
+	 * missing → `false`.
+	 */
+	force_password_change?: boolean;
 }
 
 /** Fields rendered by the paginated admin table. Full account details remain
diff --git a/frontend/src/lib/stores/session.svelte.ts b/frontend/src/lib/stores/session.svelte.ts
index 574df8b9..8a78e6cc 100644
--- a/frontend/src/lib/stores/session.svelte.ts
+++ b/frontend/src/lib/stores/session.svelte.ts
@@ -19,6 +19,18 @@ class SessionStore {
 
 	isExternalUser = $derived(this.user?.is_external ?? false);
 	isAuthenticated = $derived(this.user !== null);
+	/**
+	 * TRUE when the backend has set `force_password_change_at_next_login`
+	 * on this account — an admin picked a temporary password and the
+	 * user MUST change it before doing anything else. Drives the root
+	 * layout's mandatory-mode redirect: any protected route other than
+	 * `/profile` bounces back until the flag flips to false.
+	 *
+	 * Set to false by default so an older backend that predates the
+	 * flag (or a malformed `/me` response) doesn't accidentally
+	 * quarantine every user.
+	 */
+	mustChangePassword = $derived(this.user?.force_password_change === true);
 
 	/**
 	 * Resolve the session once. Probes /api/auth/me; on 401 it makes a single
diff --git a/frontend/src/routes/+layout.svelte b/frontend/src/routes/+layout.svelte
index 2052001f..0c847322 100644
--- a/frontend/src/routes/+layout.svelte
+++ b/frontend/src/routes/+layout.svelte
@@ -8,6 +8,7 @@
 	import AppShell from '$lib/components/AppShell.svelte';
 	import DialogHost from '$lib/components/DialogHost.svelte';
 	import Toaster from '$lib/components/Toaster.svelte';
+	import { setPasswordChangeRequiredHandler } from '$lib/api/client';
 	import { session } from '$lib/stores/session.svelte';
 	import { ui } from '$lib/stores/ui.svelte';
 	import { hashUrlToPath } from '$lib/utils/hashRedirect';
@@ -44,6 +45,21 @@
 	// the guard waits for it before deciding.
 	let providers = $state<OidcProviders | null>(null);
 
+	// Wire the fetch-interceptor's mandatory-mode handler to a soft
+	// `goto()` so a stale-tab request that surfaces a 403
+	// `PasswordChangeRequired` routes to `/profile` without a full
+	// page reload — preserving the SPA session, drives cache, etc.
+	// The `next=` carries the intended destination so the profile
+	// page can bounce back after the change lands. Falls back to
+	// `window.location` if no `next` context (see the default handler
+	// in client.ts).
+	setPasswordChangeRequiredHandler(() => {
+		const path = page.url.pathname + page.url.search;
+		void goto(resolve(`/profile?forcePasswordChange=1&next=${encodeURIComponent(path)}`), {
+			replaceState: true
+		});
+	});
+
 	onMount(async () => {
 		await killLegacyServiceWorker();
 
@@ -84,6 +100,34 @@
 		}
 		void goto(resolve(`/login?redirect=${encodeURIComponent(path)}`), { replaceState: true });
 	});
+
+	// Mandatory change-password guard. When the backend has set
+	// `force_password_change_at_next_login` (admin reset), the SPA MUST
+	// keep the user on the profile page until they pick a new password.
+	// The backend also refuses every non-allowlisted endpoint with 403
+	// PasswordChangeRequired — this guard is the UX side of that lock,
+	// so the user sees the password form instead of a wall of 403s
+	// wherever they clicked.
+	//
+	// Runs AFTER the unauthenticated guard so we don't misroute a
+	// still-loading session. Skips the guard on `/login` too — a
+	// signed-out user on the login form doesn't yet have a session
+	// state to consult, and if `session.mustChangePassword` is true
+	// on `/login` (rare — happens if the user reloaded post-login
+	// but before the profile navigation completed), the login-form
+	// success handler will route to `/profile?forcePasswordChange=1`
+	// on its own.
+	$effect(() => {
+		if (!ready) return;
+		if (!session.isAuthenticated) return;
+		if (!session.mustChangePassword) return;
+		const path = page.url.pathname;
+		if (path === '/profile' || isPublic(path)) return;
+		// Preserve the intended destination so the profile page can
+		// bounce back once the password is successfully changed.
+		const next = encodeURIComponent(path);
+		void goto(resolve(`/profile?forcePasswordChange=1&next=${next}`), { replaceState: true });
+	});
 </script>
 
 {#if isPublic(page.url.pathname)}
diff --git a/frontend/src/routes/profile/+page.svelte b/frontend/src/routes/profile/+page.svelte
index ffbe5298..0d8e64ef 100644
--- a/frontend/src/routes/profile/+page.svelte
+++ b/frontend/src/routes/profile/+page.svelte
@@ -1,7 +1,12 @@
 <script lang="ts">
 	import { errorToast } from '$lib/utils/errors';
 	import { relativeTimeAgo } from '$lib/utils/time';
-	import { onMount } from 'svelte';
+	import { onMount, tick } from 'svelte';
+	import { goto } from '$app/navigation';
+	import { resolve } from '$app/paths';
+	import type { Pathname } from '$app/types';
+	import { page } from '$app/state';
+	import { ApiError } from '$lib/api/client';
 	import {
 		changePassword,
 		createAppPassword,
@@ -13,7 +18,7 @@
 		type AppPassword,
 		type ProfilePatch
 	} from '$lib/api/endpoints/profile';
-	import { getOidcProviders } from '$lib/api/endpoints/auth';
+	import { fetchMe, getOidcProviders } from '$lib/api/endpoints/auth';
 	import { SUPPORTED_LOCALES, setLocale, t, type Locale } from '$lib/i18n/index.svelte';
 	import Icon from '$lib/icons/Icon.svelte';
 	import { confirmDialog } from '$lib/stores/dialogs.svelte';
@@ -68,6 +73,37 @@
 	const canEditImage = $derived(session.user?.can_edit_image === true && isLocal);
 	const showPasswordCard = $derived(isLocal && passwordLoginEnabled);
 
+	/**
+	 * Mandatory change-password mode. TRUE when the backend has
+	 * flagged the account (`session.mustChangePassword`) OR the URL
+	 * carries `?forcePasswordChange=1` (arrived here from the login
+	 * form / layout guard). Either signal locks the page into a
+	 * single-purpose form: banner + password card only, other cards
+	 * hidden. The URL param is a belt-and-braces alongside the store
+	 * — a stale-tab session that lost the flag momentarily still
+	 * shows the mandatory UI if the URL says so, and the layout guard
+	 * will bounce a non-flagged user back off `/profile` naturally.
+	 */
+	const forceModeQueryParam = $derived(page.url.searchParams.get('forcePasswordChange') === '1');
+	const mandatoryMode = $derived(session.mustChangePassword || forceModeQueryParam);
+	/**
+	 * Destination to bounce back to after a successful change. Only
+	 * consulted in mandatory mode; caller-supplied via `?next=<encoded>`
+	 * (added by the layout guard). Falls back to `/files` — the
+	 * standard SPA landing point — when absent or when the value
+	 * isn't a same-origin path (`startsWith('/')`).
+	 */
+	const nextAfterChange = $derived.by(() => {
+		const raw = page.url.searchParams.get('next');
+		if (!raw) return '/files';
+		try {
+			const decoded = decodeURIComponent(raw);
+			return decoded.startsWith('/') ? decoded : '/files';
+		} catch {
+			return '/files';
+		}
+	});
+
 	const storagePct = $derived(
 		session.user && session.user.storage_quota_bytes > 0
 			? Math.min(
@@ -161,18 +197,72 @@
 			);
 			return;
 		}
+		if (newPw === currentPw) {
+			// Fast client-side reject — the backend also enforces this
+			// (400 `PasswordUnchanged`) but the SPA can save the round-
+			// trip. Load-bearing in mandatory mode: silently accepting
+			// same-as-current would clear the force flag without a real
+			// rotation, defeating the "temporary password" pattern.
+			ui.notify(
+				t('profile.password_unchanged', 'New password must differ from the current one.'),
+				'error'
+			);
+			return;
+		}
 		savingPassword = true;
 		try {
 			await changePassword(currentPw, newPw);
 			currentPw = newPw = confirmPw = '';
 			ui.notify(t('profile.password_updated', 'Password updated'), 'success');
+
+			// If we're in mandatory mode, the backend just cleared the
+			// force flag AND revoked all sessions. Refresh the session
+			// so the layout guard lifts, then bounce to the intended
+			// destination the layout captured on entry. Refresh order
+			// matters: goto() before the session refresh would race
+			// the layout's `mustChangePassword` derived and re-redirect
+			// us right back to /profile.
+			if (mandatoryMode) {
+				try {
+					const me = await fetchMe();
+					if (me) session.setUser(me);
+				} catch {
+					/* stale session state is recoverable — the next request refreshes it */
+				}
+				await goto(resolve(nextAfterChange as Pathname), { replaceState: true });
+			}
 		} catch (err) {
-			errorToast(err);
+			// Remap the backend's `PasswordUnchanged` error_type to a
+			// specific, translatable message — the generic errorToast
+			// would show the raw server string. Every other error
+			// path still flows through errorToast.
+			if (err instanceof ApiError && err.errorType === 'PasswordUnchanged') {
+				ui.notify(
+					t('profile.password_unchanged', 'New password must differ from the current one.'),
+					'error'
+				);
+			} else {
+				errorToast(err);
+			}
 		} finally {
 			savingPassword = false;
 		}
 	}
 
+	// In mandatory mode, focus the current-password input as soon as
+	// the DOM is ready so the user can type without scrolling / clicking
+	// around to find the form. `tick()` waits for the reactive render;
+	// the null-check tolerates the (rare) case where the form isn't
+	// mounted yet on first paint.
+	onMount(async () => {
+		if (!mandatoryMode) return;
+		await tick();
+		const el = document.querySelector<HTMLInputElement>(
+			'[data-testid="profile-current-password-input"]'
+		);
+		el?.focus();
+	});
+
 	// ── Avatar edit panel ──────────────────────────────────────────────────
 	function openAvatarEdit() {
 		avatarEditOpen = true;
@@ -304,9 +394,41 @@
 
 <svelte:head><title>{t('nav.profile', 'Profile')} · OxiCloud</title></svelte:head>
 
-<main class="profile">
+<main class="profile" class:profile--mandatory={mandatoryMode}>
 	<h1>{t('nav.profile', 'Profile')}</h1>
 
+	{#if mandatoryMode}
+		<!--
+			Mandatory-mode banner. Rendered above every other section
+			whenever `session.mustChangePassword` is TRUE or the URL
+			carries `?forcePasswordChange=1`. Explains WHY the user
+			landed here (an admin picked a temporary password) and
+			what they need to do (rotate before continuing). Backend
+			also refuses every non-allowlisted endpoint with 403
+			PasswordChangeRequired — so a user who dismisses the
+			banner via URL manipulation still can't reach any file /
+			DAV / admin endpoint until the change lands.
+		-->
+		<div
+			class="mandatory-banner"
+			role="alert"
+			data-testid="profile-mandatory-change-password-banner"
+		>
+			<Icon name="shield-alt" />
+			<div class="mandatory-banner__body">
+				<strong>
+					{t('profile.mandatory_change_title', 'Please change your password to continue.')}
+				</strong>
+				<p>
+					{t(
+						'profile.mandatory_change_body',
+						'An administrator has set a temporary password for your account. Choose your own password below before you can access the rest of the application.'
+					)}
+				</p>
+			</div>
+		</div>
+	{/if}
+
 	{#if session.user}
 		<!-- Avatar / identity -->
 		<div class="card avatar-card">
@@ -738,7 +860,7 @@
 
 		<!-- Change password -->
 		{#if showPasswordCard}
-			<form class="card" data-testid="profile-password-form" onsubmit={savePassword}>
+			<form class="card password-card" data-testid="profile-password-form" onsubmit={savePassword}>
 				<h2><Icon name="key" /> {t('profile.change_password', 'Change Password')}</h2>
 				<label>
 					<span>{t('profile.current_password', 'Current Password')}</span>
@@ -800,6 +922,40 @@
 		border-radius: var(--radius-lg);
 	}
 
+	/*
+	 * Mandatory-mode: hide every card except the identity header
+	 * (`.avatar-card` keeps context — who am I?) and the password
+	 * form. Backend blocks non-allowlisted endpoints with 403 anyway;
+	 * this is the UX side of that lock so the user sees exactly one
+	 * form to fill in. Ergonomically loud banner + a single card.
+	 */
+	.profile--mandatory :global(.card):not(.avatar-card, .password-card) {
+		display: none;
+	}
+
+	.mandatory-banner {
+		display: flex;
+		align-items: flex-start;
+		gap: 0.75rem;
+		padding: 1rem 1.25rem;
+		background: var(--color-bg-warning-subtle, var(--color-bg-surface));
+		border: 1px solid var(--color-border-warning, var(--color-border));
+		border-left: 4px solid var(--color-accent-warning, var(--color-accent));
+		border-radius: var(--radius-md, var(--radius-lg));
+		color: var(--color-text);
+	}
+
+	.mandatory-banner__body strong {
+		display: block;
+		margin-bottom: 0.25rem;
+	}
+
+	.mandatory-banner__body p {
+		margin: 0;
+		font-size: 0.9rem;
+		color: var(--color-text-muted);
+	}
+
 	.card h2 {
 		margin: 0 0 0.25rem;
 		font-size: 1.125rem;
diff --git a/src/application/dtos/user_dto.rs b/src/application/dtos/user_dto.rs
index 6db3a368..d811fd5a 100644
--- a/src/application/dtos/user_dto.rs
+++ b/src/application/dtos/user_dto.rs
@@ -72,6 +72,28 @@ pub struct UserDto {
     /// `frontend/src/lib/stores/preferences.svelte.ts`). Always present
     /// on the wire; empty bag is `{}`, never `null`.
     pub ui_preferences: serde_json::Value,
+    /// Mirrors `auth.users.force_password_change_at_next_login`. Set
+    /// TRUE by the admin password-reset flow (see
+    /// `AuthApplicationService::admin_reset_password`) and cleared by
+    /// a successful self-service `POST /api/auth/change-password`.
+    ///
+    /// Populated only by the `/api/auth/me` handler and the login
+    /// response minter (via a distinct code path). `From<User>` — used
+    /// by admin listings, share-recipient responses, group-member DTOs,
+    /// etc. — leaves it at `false`. The flag is a per-session-account
+    /// concern (does *this* user need to change their password before
+    /// they can proceed?), not a general user attribute worth
+    /// surfacing on every list row.
+    ///
+    /// The load-bearing consumer is the SPA's session store: on
+    /// startup and after every refresh, `/me` returns the current
+    /// flag value and the SPA's nav-guard blocks navigation to
+    /// anything but the change-password surface until it flips
+    /// back to false. Backend enforcement is separate (see the
+    /// `require_no_password_change_pending` middleware) — this DTO
+    /// field is what the SPA reads to render the mandatory-mode UI.
+    #[serde(default)]
+    pub force_password_change: bool,
 }
 
 /// Compact row returned by the paginated admin user table.
@@ -145,6 +167,13 @@ impl From<User> for UserDto {
             preferred_locale: p.preferred_locale,
             notify_on_share: p.notify_on_share,
             ui_preferences: p.ui_preferences,
+            // Defaults to false. The `/me` handler + the login-response
+            // minter populate this via a distinct code path (a
+            // repo read that goes through the auth service's cache);
+            // admin listings and other UserDto consumers deliberately
+            // leave it false — the flag is per-session-account state,
+            // not a general user attribute.
+            force_password_change: false,
         }
     }
 }
diff --git a/src/application/services/auth_application_service.rs b/src/application/services/auth_application_service.rs
index 394f9a36..6f496536 100644
--- a/src/application/services/auth_application_service.rs
+++ b/src/application/services/auth_application_service.rs
@@ -1863,6 +1863,27 @@ impl AuthApplicationService {
             ));
         }
 
+        // Reject same-as-current. Load-bearing when the caller is on
+        // an admin-picked temp password (force_password_change_at_next_login
+        // = TRUE): silently accepting the same string would clear the
+        // force flag without the user actually rotating the credential,
+        // defeating the whole "temporary password" pattern. Verify
+        // against the stored hash (constant-time via `verify_password`)
+        // rather than string-comparing plaintexts, so length / case
+        // typos on the caller's part still fail cleanly. Handler
+        // layer remaps the message to `error_type: "PasswordUnchanged"`.
+        let same_as_current = self
+            .password_hasher
+            .verify_password(&dto.new_password, hash)
+            .await?;
+        if same_as_current {
+            return Err(DomainError::new(
+                ErrorKind::InvalidInput,
+                "User",
+                "New password must differ from the current password",
+            ));
+        }
+
         // Hash new password and update user
         let new_hash = self
             .password_hasher
@@ -1889,6 +1910,15 @@ impl AuthApplicationService {
             );
         }
 
+        // Evict the cached UserFlags entry so
+        // `require_no_password_change_pending` sees the just-cleared
+        // flag on the next request — otherwise the caller would keep
+        // hitting 403 PasswordChangeRequired until the 30 s TTL rolls
+        // over. (The revoke_all_user_sessions below will force a
+        // re-login anyway, but the cache eviction covers the window
+        // between change_password success and the new session mint.)
+        self.user_flags_cache.invalidate(&user_id).await;
+
         // Optional: revoke all sessions to force re-login with new password
         self.session_storage
             .revoke_all_user_sessions(user_id)
@@ -2755,13 +2785,70 @@ impl AuthApplicationService {
         let hash = self.password_hasher.hash_password(new_password).await?;
         self.user_storage.change_password(user_id, &hash).await?;
 
+        // Mark the admin-picked password as temporary so the user gets
+        // prompted to pick their own on next login. Two branches:
+        //
+        //   * OPAQUE wired: `clear_registration` is the atomic write
+        //     that (a) NULLs the OPAQUE envelope + migration mark so
+        //     the migrated user drops back to legacy login (the old
+        //     envelope is bound to the OLD passphrase and would fail
+        //     OPAQUE KE3), and (b) sets `force_password_change`.
+        //     Silent-migration on the next legacy login re-mints a
+        //     fresh envelope bound to the admin's new password; the
+        //     force flag then routes the SPA to change-password.
+        //
+        //   * OPAQUE off: no envelope to invalidate; just flip the
+        //     force flag directly via user_storage. Same downstream
+        //     behaviour — SPA sees force_password_change=true on
+        //     the next login response and routes accordingly.
+        //
+        // Both writes are non-fatal (logged at warn on failure): the
+        // password reset itself succeeded, and a stale force flag is
+        // recoverable on the next admin reset.
+        if let Some(opaque) = self.opaque_repo.as_ref() {
+            if let Err(e) = opaque.clear_registration(user_id).await {
+                tracing::warn!(
+                    target: "audit",
+                    event = "auth.admin_reset_opaque_clear_failed",
+                    user_id = %user_id,
+                    error = %e,
+                    "OPAQUE clear_registration failed during admin password reset — \
+                     force flag + envelope invalidation deferred to next opportunity"
+                );
+            }
+        } else if let Err(e) = self.user_storage.set_force_password_change(user_id).await {
+            tracing::warn!(
+                target: "audit",
+                event = "auth.admin_reset_force_flag_failed",
+                user_id = %user_id,
+                error = %e,
+                "set_force_password_change failed during admin password reset — \
+                 user will not be prompted to change from admin's temp password"
+            );
+        }
+
         // Invalidate all existing sessions so the user must re-login
         // with the new password.  Mirrors the behaviour of change_password().
         self.session_storage
             .revoke_all_user_sessions(user_id)
             .await?;
 
-        tracing::info!(user_id = %user_id, "Admin reset password — all sessions revoked");
+        // Evict the cached UserFlags row so the next authenticated
+        // request from this user (on their next session) sees the
+        // updated force_password_change value without waiting for
+        // the 30s TTL. The middleware
+        // `require_no_password_change_pending` reads from this cache
+        // — a stale FALSE would keep the API open to the admin's
+        // temp-password holder until the TTL rolled over.
+        self.user_flags_cache.invalidate(&user_id).await;
+
+        tracing::info!(
+            target: "audit",
+            event = "auth.admin_reset_password",
+            user_id = %user_id,
+            opaque_wired = self.opaque_repo.is_some(),
+            "👮🏻‍♂️ Admin reset password — sessions revoked, force-change flag set"
+        );
         Ok(())
     }
 
diff --git a/src/domain/entities/user.rs b/src/domain/entities/user.rs
index 38675f5a..a12e50be 100644
--- a/src/domain/entities/user.rs
+++ b/src/domain/entities/user.rs
@@ -38,6 +38,15 @@ pub struct UserFlags {
     pub role: UserRole,
     pub is_external: bool,
     pub active: bool,
+    /// Mirrors `auth.users.force_password_change_at_next_login`. TRUE
+    /// after an admin password-reset; the `require_no_password_change_pending`
+    /// middleware refuses every authenticated endpoint except the
+    /// change-password / me / logout / refresh allowlist while it's set.
+    /// Cached alongside the other flags so per-request enforcement
+    /// doesn't add a DB round-trip. Eagerly invalidated by
+    /// `admin_reset_password` (flip to TRUE) and `change_password`
+    /// (flip to FALSE) so the gate lifts within one round-trip.
+    pub force_password_change: bool,
 }
 
 #[derive(Debug, Clone)]
diff --git a/src/infrastructure/repositories/pg/user_pg_repository.rs b/src/infrastructure/repositories/pg/user_pg_repository.rs
index fdda28d5..7aef057c 100644
--- a/src/infrastructure/repositories/pg/user_pg_repository.rs
+++ b/src/infrastructure/repositories/pg/user_pg_repository.rs
@@ -62,9 +62,12 @@ impl UserPgRepository {
     pub async fn get_user_flags(&self, id: Uuid) -> UserRepositoryResult<UserFlags> {
         let row = sqlx::query(
             r#"
-            SELECT role::text as role_text, is_external, active
-            FROM auth.users
-            WHERE id = $1
+            SELECT role::text as role_text,
+                   is_external,
+                   active,
+                   force_password_change_at_next_login
+              FROM auth.users
+             WHERE id = $1
             "#,
         )
         .bind(id)
@@ -82,6 +85,7 @@ impl UserPgRepository {
             role,
             is_external: row.get("is_external"),
             active: row.get("active"),
+            force_password_change: row.get("force_password_change_at_next_login"),
         })
     }
 
@@ -161,6 +165,30 @@ impl UserPgRepository {
         Ok(())
     }
 
+    /// Set `force_password_change_at_next_login = TRUE`. Used by
+    /// admin-initiated password reset when the OPAQUE substrate is NOT
+    /// wired. When it IS wired, callers should prefer
+    /// `OpaquePgRepository::clear_registration` which does the same
+    /// flag flip AND invalidates the OPAQUE envelope in one UPDATE
+    /// (see the port doc on `clear_registration` for the atomicity
+    /// contract). This method exists so OPAQUE-off deployments still
+    /// get the "admin's temp password prompts change on next login"
+    /// behaviour without having to depend on the OPAQUE code path.
+    pub async fn set_force_password_change(&self, id: Uuid) -> UserRepositoryResult<()> {
+        sqlx::query(
+            r#"
+            UPDATE auth.users
+               SET force_password_change_at_next_login = TRUE
+             WHERE id = $1
+            "#,
+        )
+        .bind(id)
+        .execute(&*self.pool)
+        .await
+        .map_err(Self::map_sqlx_error)?;
+        Ok(())
+    }
+
     /// Updates a user's profile image (URL or data URI). Not part of the
     /// `UserRepository` trait — called directly from `AuthApplicationService`.
     pub async fn update_image(
diff --git a/src/interfaces/api/handlers/auth_handler.rs b/src/interfaces/api/handlers/auth_handler.rs
index 5e5a66de..d3f5bd65 100644
--- a/src/interfaces/api/handlers/auth_handler.rs
+++ b/src/interfaces/api/handlers/auth_handler.rs
@@ -614,11 +614,24 @@ pub async fn get_current_user(
     // never count against this envelope — collaborating in a team drive
     // costs no personal bytes. The matching cap is
     // `storage_quota_bytes` (admin-only mutation).
-    let user = auth_service
+    let mut user = auth_service
         .auth_application_service
         .get_user_by_id(user_id)
         .await?;
 
+    // Overlay the cached `force_password_change` flag (see UserFlags).
+    // `From<User>` defaults to false; the SPA reads this field on
+    // startup to decide whether to enter mandatory change-password
+    // mode. Using the cached path (`get_user_flags` → `user_flags_cache`)
+    // avoids a second DB round-trip on this hot endpoint.
+    if let Ok(flags) = auth_service
+        .auth_application_service
+        .get_user_flags(user_id)
+        .await
+    {
+        user.force_password_change = flags.force_password_change;
+    }
+
     Ok((StatusCode::OK, Json(user)))
 }
 
@@ -652,12 +665,28 @@ pub async fn change_password(
         .as_ref()
         .ok_or_else(|| AppError::internal_error("Authentication service not configured"))?;
 
-    auth_service
+    match auth_service
         .auth_application_service
         .change_password(user_id, dto)
-        .await?;
-
-    Ok(StatusCode::OK)
+        .await
+    {
+        Ok(()) => Ok(StatusCode::OK),
+        Err(err) => {
+            // Remap the same-as-current guard into a stable error_type
+            // the SPA can surface as "pick a different one" without
+            // needing to fall back to the generic 400 message. The
+            // service returns InvalidInput; keep the 400 status but
+            // swap the shape.
+            if err.message == "New password must differ from the current password" {
+                return Err(AppError::new(
+                    StatusCode::BAD_REQUEST,
+                    "New password must differ from the current password",
+                    "PasswordUnchanged",
+                ));
+            }
+            Err(err.into())
+        }
+    }
 }
 
 /// Convert the authenticated external user into a full internal
diff --git a/src/interfaces/middleware/user.rs b/src/interfaces/middleware/user.rs
index e97de322..7c351b64 100644
--- a/src/interfaces/middleware/user.rs
+++ b/src/interfaces/middleware/user.rs
@@ -242,6 +242,129 @@ pub async fn require_internal_user_layer(
     next.run(request).await
 }
 
+/// Endpoints the gate lets through even when
+/// `force_password_change_at_next_login` is TRUE — the caller needs
+/// them to complete the mandatory reset:
+///
+///   * `GET  /api/auth/me`             — the SPA must be able to read
+///     the flag (that's what tells it to enter mandatory-mode).
+///   * `PUT  /api/auth/change-password` — the way OUT of the state.
+///   * `POST /api/auth/logout`         — bailing out is always allowed.
+///
+/// `/api/auth/refresh` is not on this list because refresh is mounted
+/// on a rate-limited public path that doesn't carry a `CurrentUser` at
+/// middleware time; the gate never fires on it. If refresh ever moves
+/// under the gate, add `(&Method::POST, "/api/auth/refresh")` here.
+fn is_password_change_pending_allowlisted(
+    method: &axum::http::Method,
+    path: &str,
+) -> bool {
+    use axum::http::Method;
+    matches!(
+        (method, path),
+        (&Method::GET, "/api/auth/me")
+            | (&Method::PUT, "/api/auth/change-password")
+            | (&Method::POST, "/api/auth/logout")
+    )
+}
+
+/// Axum middleware layer that blocks EVERY authenticated request when
+/// the caller's `force_password_change_at_next_login` flag is TRUE —
+/// EXCEPT the small allowlist above ([`is_password_change_pending_allowlisted`]).
+/// Mounted on all authenticated `/api/*` subtrees so an admin-set
+/// temp password cannot be used to hit files / WebDAV / CalDAV / etc.
+/// via any non-SPA client.
+///
+/// The flag is read from the cached `UserFlags` (same cache the role /
+/// external guards use — see [`require_internal_user`]), so this adds
+/// no DB round-trip on the hot path. `admin_reset_password` and
+/// `change_password` both invalidate the entry eagerly so the gate
+/// lifts within one request round-trip.
+///
+/// Response shape on refusal: `403 { error_type: "PasswordChangeRequired" }`.
+/// The SPA reads that error_type on any subsequent request that leaks
+/// past its own nav guard (mid-navigation refresh, stale tab, …) and
+/// bounces the user back to the change-password screen. Non-SPA
+/// clients (WebDAV sync, mobile app, curl) get the same 403 — that's
+/// intentional; they need to log in via the SPA once to complete the
+/// reset before other clients work again.
+///
+/// Must run AFTER the auth middleware. On unauthenticated paths (no
+/// `CurrentUser` populated) this is a pass-through — the inner
+/// handler / auth layer will produce the 401.
+pub async fn require_no_password_change_pending_layer(
+    State(state): State<Arc<AppState>>,
+    request: Request,
+    next: Next,
+) -> Response {
+    // Cheap path check FIRST — allowlisted endpoints never even hit
+    // the flag lookup. Keeps the /me polling path (which the SPA hits
+    // as part of every session-probe) from doing the cache lookup on
+    // every call, and makes the allowlist trivially auditable in one
+    // place (see `is_password_change_pending_allowlisted`).
+    //
+    // MUST use `OriginalUri` — axum's `.nest("/api/auth", …)` strips
+    // the prefix so `request.uri().path()` returns `/me` inside the
+    // nested router, not `/api/auth/me`. The allowlist is defined
+    // against the operator-visible full URL, so we need the pre-strip
+    // path. `OriginalUri` is set on the request extensions by axum
+    // whenever a nest strips a prefix; falls back to the current path
+    // when this middleware is layered on a top-level (non-nested)
+    // router (defense in depth).
+    let full_path = request
+        .extensions()
+        .get::<axum::extract::OriginalUri>()
+        .map(|uri| uri.0.path().to_owned())
+        .unwrap_or_else(|| request.uri().path().to_owned());
+    if is_password_change_pending_allowlisted(request.method(), &full_path) {
+        return next.run(request).await;
+    }
+
+    let caller_id = request
+        .extensions()
+        .get::<Arc<CurrentUser>>()
+        .map(|cu| cu.id);
+
+    let (Some(caller_id), Some(svc)) = (
+        caller_id,
+        state
+            .auth_service
+            .as_ref()
+            .map(|s| &*s.auth_application_service),
+    ) else {
+        return next.run(request).await;
+    };
+
+    // Cached lookup — no DB hit on the hot path. Fail-open on repo
+    // error (the same posture as require_internal_user_layer above):
+    // a transient DB blip must not lock every user out of every API,
+    // and the SPA-side nav guard is a defense-in-depth backstop.
+    let flag = match svc.get_user_flags(caller_id).await {
+        Ok(f) => f.force_password_change,
+        Err(_) => false,
+    };
+    if flag {
+        // Log the operator-visible full path (not the nest-stripped
+        // one). `full_path` was computed above via `OriginalUri`.
+        tracing::info!(
+            target: "audit",
+            event = "auth.password_change_required_blocked",
+            reason = "force_password_change_pending",
+            caller_id = %caller_id,
+            path = %full_path,
+            "👮🏻‍♂️ Blocked API access — user must change admin-set temp password first"
+        );
+        return AppError::new(
+            StatusCode::FORBIDDEN,
+            "Password change required before accessing this endpoint",
+            "PasswordChangeRequired",
+        )
+        .into_response();
+    }
+
+    next.run(request).await
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -251,6 +374,7 @@ mod tests {
             role,
             is_external: false,
             active,
+            force_password_change: false,
         }
     }
 
diff --git a/src/main.rs b/src/main.rs
index bb16ef0c..29661296 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -776,6 +776,10 @@ async fn run() -> Result<(), Box<dyn std::error::Error>> {
         let auth_public = auth_public_routes().with_state(app_state.clone());
         // Protected auth routes (/me, /change-password, /logout) — require auth + CSRF
         let auth_protected = auth_protected_routes()
+            .layer(axum::middleware::from_fn_with_state(
+                app_state.clone(),
+                require_no_password_change_pending_layer,
+            ))
             .layer(axum::middleware::from_fn(csrf_middleware))
             .layer(axum::middleware::from_fn_with_state(
                 app_state.clone(),
@@ -784,6 +788,10 @@ async fn run() -> Result<(), Box<dyn std::error::Error>> {
             .with_state(app_state.clone());
         // App password management routes — require auth + CSRF
         let app_pw_protected = app_password_handler::app_password_routes()
+            .layer(axum::middleware::from_fn_with_state(
+                app_state.clone(),
+                require_no_password_change_pending_layer,
+            ))
             .layer(axum::middleware::from_fn(csrf_middleware))
             .layer(axum::middleware::from_fn_with_state(
                 app_state.clone(),
@@ -802,6 +810,10 @@ async fn run() -> Result<(), Box<dyn std::error::Error>> {
         // is safe.
         let opaque_register_protected =
             oxicloud::interfaces::api::handlers::opaque_auth_handler::opaque_register_routes()
+                .layer(axum::middleware::from_fn_with_state(
+                    app_state.clone(),
+                    require_no_password_change_pending_layer,
+                ))
                 .layer(axum::middleware::from_fn(csrf_middleware))
                 .layer(axum::middleware::from_fn_with_state(
                     app_state.clone(),
@@ -835,6 +847,10 @@ async fn run() -> Result<(), Box<dyn std::error::Error>> {
             device_auth_handler::device_auth_public_routes().with_state(app_state.clone());
         // Protected endpoints: /api/auth/device/verify, /api/auth/device/devices
         let device_protected = device_auth_handler::device_auth_protected_routes()
+            .layer(axum::middleware::from_fn_with_state(
+                app_state.clone(),
+                require_no_password_change_pending_layer,
+            ))
             .layer(axum::middleware::from_fn(csrf_middleware))
             .layer(axum::middleware::from_fn_with_state(
                 app_state.clone(),
@@ -844,6 +860,10 @@ async fn run() -> Result<(), Box<dyn std::error::Error>> {
 
         // Protected API routes — require valid JWT token
         let protected_api = api_routes
+            .layer(axum::middleware::from_fn_with_state(
+                app_state.clone(),
+                require_no_password_change_pending_layer,
+            ))
             .layer(axum::middleware::from_fn(csrf_middleware))
             .layer(axum::middleware::from_fn_with_state(
                 app_state.clone(),
@@ -857,8 +877,22 @@ async fn run() -> Result<(), Box<dyn std::error::Error>> {
         // surface to a principal kind that can do nothing with it. The
         // `require_internal_user_layer` runs AFTER auth (tower order:
         // later .layer() = outermost = runs first).
-        use oxicloud::interfaces::middleware::user::require_internal_user_layer;
+        //
+        // `require_no_password_change_pending_layer` is layered on
+        // every authenticated /api/* subtree so an admin-set temp
+        // password cannot be used against files / WebDAV / CalDAV /
+        // admin from any non-SPA client. The layer allowlists /me,
+        // change-password, and logout internally so the SPA can
+        // complete the reset flow — see the middleware doc for the
+        // allowlist and its rationale.
+        use oxicloud::interfaces::middleware::user::{
+            require_internal_user_layer, require_no_password_change_pending_layer,
+        };
         let caldav_protected = caldav_router
+            .layer(axum::middleware::from_fn_with_state(
+                app_state.clone(),
+                require_no_password_change_pending_layer,
+            ))
             .layer(axum::middleware::from_fn_with_state(
                 app_state.clone(),
                 require_internal_user_layer,
@@ -868,6 +902,10 @@ async fn run() -> Result<(), Box<dyn std::error::Error>> {
                 auth_middleware,
             ));
         let carddav_protected = carddav_router
+            .layer(axum::middleware::from_fn_with_state(
+                app_state.clone(),
+                require_no_password_change_pending_layer,
+            ))
             .layer(axum::middleware::from_fn_with_state(
                 app_state.clone(),
                 require_internal_user_layer,
@@ -877,6 +915,10 @@ async fn run() -> Result<(), Box<dyn std::error::Error>> {
                 auth_middleware,
             ));
         let webdav_protected = webdav_router
+            .layer(axum::middleware::from_fn_with_state(
+                app_state.clone(),
+                require_no_password_change_pending_layer,
+            ))
             .layer(axum::middleware::from_fn_with_state(
                 app_state.clone(),
                 require_internal_user_layer,
diff --git a/tests/api/admin_user_ops.hurl b/tests/api/admin_user_ops.hurl
index e19e2c06..0abbe1bf 100644
--- a/tests/api/admin_user_ops.hurl
+++ b/tests/api/admin_user_ops.hurl
@@ -130,7 +130,13 @@ Content-Type: application/json
 
 HTTP 403
 
-# New password works.
+# New password works AND the login response carries
+# `force_password_change: true` — the admin-picked password is
+# temporary; the SPA reads this to enter mandatory-mode and route
+# the user to `/profile?forcePasswordChange=1`. See the backend
+# `admin_reset_password` → `OpaquePgRepository::clear_registration`
+# (or `UserPgRepository::set_force_password_change` when OPAQUE is
+# off) for the atomic flag write.
 POST {{base_url}}/api/auth/login
 Content-Type: application/json
 { "username": "charlie-ops", "password": "AdminResetPassword2!" }
@@ -138,6 +144,82 @@ Content-Type: application/json
 HTTP 200
 [Captures]
 charlie_token_v2: jsonpath "$.access_token"
+[Asserts]
+jsonpath "$.force_password_change" == true
+
+
+# `require_no_password_change_pending_layer` middleware assertion:
+# a random authenticated endpoint that ISN'T on the allowlist
+# (`/me`, `/change-password`, `/logout`) must refuse with
+# `403 PasswordChangeRequired` while the flag is set. Without
+# this gate the admin-picked password would let holders reach
+# files / DAV / admin via any non-SPA client.
+GET {{base_url}}/api/folders
+Authorization: Bearer {{charlie_token_v2}}
+
+HTTP 403
+[Asserts]
+jsonpath "$.error_type" == "PasswordChangeRequired"
+
+
+# Same session, but the allowlisted `/api/auth/me` DOES pass —
+# the SPA needs this to detect the flag and render the mandatory
+# banner. Response also mirrors the flag so a page reload sees
+# the same state a fresh login would.
+GET {{base_url}}/api/auth/me
+Authorization: Bearer {{charlie_token_v2}}
+
+HTTP 200
+[Asserts]
+jsonpath "$.force_password_change" == true
+
+
+# Trying to change back to the SAME password must fail with a
+# distinct `PasswordUnchanged` error_type — silently accepting
+# the no-op would clear the force flag without actually rotating
+# the credential, defeating the temporary-password pattern.
+PUT {{base_url}}/api/auth/change-password
+Authorization: Bearer {{charlie_token_v2}}
+Content-Type: application/json
+{ "current_password": "AdminResetPassword2!", "new_password": "AdminResetPassword2!" }
+
+HTTP 400
+[Asserts]
+jsonpath "$.error_type" == "PasswordUnchanged"
+
+
+# Change to a genuinely different password: succeeds AND
+# `change_password` revokes all sessions (per its own contract);
+# the CURRENT token stops working right after. That side effect
+# is what forces the user through a fresh login where the flag
+# is now cleared.
+PUT {{base_url}}/api/auth/change-password
+Authorization: Bearer {{charlie_token_v2}}
+Content-Type: application/json
+{ "current_password": "AdminResetPassword2!", "new_password": "CharliePicked3!" }
+
+HTTP 200
+
+
+# Fresh login with the user-picked password: succeeds AND the
+# flag has flipped back to false, so mandatory-mode is off.
+POST {{base_url}}/api/auth/login
+Content-Type: application/json
+{ "username": "charlie-ops", "password": "CharliePicked3!" }
+
+HTTP 200
+[Captures]
+charlie_token_v3: jsonpath "$.access_token"
+[Asserts]
+jsonpath "$.force_password_change" == false
+
+
+# Same random endpoint that 403'd above now succeeds — the gate
+# has lifted.
+GET {{base_url}}/api/folders
+Authorization: Bearer {{charlie_token_v3}}
+
+HTTP 200
 
 
 # ─────────────────────────────────────────────────────────────
@@ -155,7 +237,7 @@ HTTP 200
 
 POST {{base_url}}/api/auth/login
 Content-Type: application/json
-{ "username": "charlie-ops", "password": "AdminResetPassword2!" }
+{ "username": "charlie-ops", "password": "CharliePicked3!" }
 
 HTTP 403
 
@@ -172,7 +254,7 @@ HTTP 200
 
 POST {{base_url}}/api/auth/login
 Content-Type: application/json
-{ "username": "charlie-ops", "password": "AdminResetPassword2!" }
+{ "username": "charlie-ops", "password": "CharliePicked3!" }
 
 HTTP 200