diff --git a/frontend/src/App.svelte b/frontend/src/App.svelte
index 5dc5584..94ff430 100644
--- a/frontend/src/App.svelte
+++ b/frontend/src/App.svelte
@@ -14,6 +14,7 @@
   import PublicList from './components/PublicList.svelte';
   import Admin from './components/Admin.svelte';
   import ModerateTags from './components/ModerateTags.svelte';
+  import UnlockBanner from './components/UnlockBanner.svelte';
   import ActivityPermalink from './components/ActivityPermalink.svelte';
   import Personvern from './components/Personvern.svelte';
   import TagPage from './components/TagPage.svelte';
@@ -263,6 +264,8 @@
     {/if}
   </nav>
 
+  <UnlockBanner />
+
   {#if view === 'loading'}
     <p class="muted">Laster …</p>
   {:else if view === 'public-list'}
diff --git a/frontend/src/components/ActivityForm.svelte b/frontend/src/components/ActivityForm.svelte
index a64d8d3..69b5942 100644
--- a/frontend/src/components/ActivityForm.svelte
+++ b/frontend/src/components/ActivityForm.svelte
@@ -107,7 +107,12 @@
    */
   function buildBody(): CreateActivityRequest {
     if (visibility === 'private') {
-      if (!session.dek) throw new Error('not_logged_in');
+      if (!session.dek) {
+        // Caller (submit) catches this and surfaces a useful message
+        // pointing at the unlock banner. The error code is a sentinel,
+        // not user-facing text.
+        throw new Error('dek_missing');
+      }
       const payload: PrivatePayload = {
         title: title.trim(),
         tags,
@@ -166,6 +171,14 @@
       error = 'Tittel er påkrevd.';
       return;
     }
+    // Pre-flight: if the user picked Privat but the DEK is missing
+    // (post-reload state), point them at the unlock banner instead of
+    // letting them fill out a form they can't submit. Same check in
+    // buildBody catches direct mis-calls.
+    if (visibility === 'private' && !session.dek) {
+      error = 'Privat innhold er låst etter sideoppdatering. Lås opp øverst på siden, så kan du lagre.';
+      return;
+    }
     busy = true;
     try {
       const body = buildBody();
@@ -175,7 +188,11 @@
       await syncPrivateTagIndex();
       onCreated(result);
     } catch (err) {
-      error = err instanceof Error ? err.message : String(err);
+      if (err instanceof Error && err.message === 'dek_missing') {
+        error = 'Privat innhold er låst etter sideoppdatering. Lås opp øverst på siden, så kan du lagre.';
+      } else {
+        error = err instanceof Error ? err.message : String(err);
+      }
     } finally {
       busy = false;
     }
diff --git a/frontend/src/components/ActivityRow.svelte b/frontend/src/components/ActivityRow.svelte
index d481812..c619342 100644
--- a/frontend/src/components/ActivityRow.svelte
+++ b/frontend/src/components/ActivityRow.svelte
@@ -316,7 +316,7 @@
         <span class="vis-badge private">Privat</span>
       </h3>
       <p class="muted">
-        Innholdet er kryptert. Logg inn på nytt med passordet ditt for å vise det.
+        Innholdet er kryptert. Lås opp øverst på siden for å vise det.
       </p>
     {:else}
       <p class="muted">Dekrypterer …</p>
diff --git a/frontend/src/components/Profile.svelte b/frontend/src/components/Profile.svelte
index 447a2a3..7d78462 100644
--- a/frontend/src/components/Profile.svelte
+++ b/frontend/src/components/Profile.svelte
@@ -204,6 +204,13 @@
     exporting = true;
     exportError = null;
     exportSize = null;
+    // Without the DEK we'd silently drop every private row from the
+    // export. Surface that instead of producing a confusingly small file.
+    if (!session.dek) {
+      exportError = 'Privat innhold er låst etter sideoppdatering. Lås opp øverst på siden, så får du med alt.';
+      exporting = false;
+      return;
+    }
     try {
       exportSize = await downloadExport();
     } catch {
diff --git a/frontend/src/components/UnlockBanner.svelte b/frontend/src/components/UnlockBanner.svelte
new file mode 100644
index 0000000..a252fa8
--- /dev/null
+++ b/frontend/src/components/UnlockBanner.svelte
@@ -0,0 +1,75 @@
+<script lang="ts">
+  /**
+   * Persistent banner shown when a user has a server session but no DEK.
+   *
+   * Happens after every full-page reload (the DEK lives only in memory —
+   * see lib/session.svelte.ts) and means private rows can't decrypt and
+   * new private rows can't be created. Without this banner the user
+   * encountered confusing failure modes (a "Logg inn på nytt" line under
+   * each private row, a raw `not_logged_in` error on save).
+   *
+   * The form runs the regular login() flow under the hood — that
+   * derives the KEK from the password and salt and unwraps the existing
+   * wrapped_dek_pw, so private ciphertexts from before the reload stay
+   * readable. The cookie is replaced as a side effect; that's fine.
+   *
+   * Hidden until both: user IS logged in, DEK IS missing. Renders
+   * nothing otherwise — App.svelte mounts it unconditionally.
+   */
+  import { session } from '../lib/session.svelte';
+  import { login } from '../lib/auth';
+  import { ApiError } from '../lib/api';
+
+  let password = $state('');
+  let busy = $state(false);
+  let error: string | null = $state(null);
+
+  // Show the banner whenever the user is "logged in but locked." A
+  // dismissed flag would only hide it temporarily — the next reload puts
+  // them right back here, and the message is brief enough that it doesn't
+  // pay to make it dismissable.
+  const visible = $derived(!!session.user && !session.dek);
+
+  async function submit(e: SubmitEvent) {
+    e.preventDefault();
+    if (!session.user || busy) return;
+    error = null;
+    busy = true;
+    try {
+      await login(session.user.email, password);
+      password = '';
+    } catch (err) {
+      error = err instanceof ApiError && err.status === 401
+        ? 'Feil passord. Prøv igjen.'
+        : 'Klarte ikke å låse opp. Prøv igjen om litt.';
+    } finally {
+      busy = false;
+    }
+  }
+</script>
+
+{#if visible}
+  <aside class="banner" role="region" aria-label="Lås opp privat innhold">
+    <form onsubmit={submit} class="row" style="gap: 0.5rem; align-items: center; margin: 0;">
+      <span style="flex: 1 1 auto;">
+        🔒 Privat innhold er låst etter sideoppdatering.
+      </span>
+      <input
+        type="password"
+        autocomplete="current-password"
+        bind:value={password}
+        placeholder="Passord"
+        aria-label="Passord"
+        required
+        minlength="12"
+        style="flex: 0 1 14rem; min-width: 0;"
+      />
+      <button class="primary" type="submit" disabled={busy}>
+        {busy ? 'Låser opp …' : 'Lås opp'}
+      </button>
+    </form>
+    {#if error}
+      <p class="error" role="alert" style="margin: 0.4rem 0 0;">{error}</p>
+    {/if}
+  </aside>
+{/if}