diff --git a/src/App.svelte b/src/App.svelte
index 0fa27ba..9e94c91 100644
--- a/src/App.svelte
+++ b/src/App.svelte
@@ -68,6 +68,7 @@
   import { OPEN_THESAURUS_EVENT } from './lib/spell/thesaurus';
   import StyleManagerDialog from './lib/components/StyleManagerDialog.svelte';
   import NoteOptionsDialog from './lib/components/NoteOptionsDialog.svelte';
+  import SaveFormatDialog from './lib/components/SaveFormatDialog.svelte';
   import { t, locale } from './lib/i18n/i18n.svelte';
   import { fnv1a } from './lib/utils/hash';
   import { withShortcut } from './lib/i18n/shortcut';
@@ -569,6 +570,7 @@
   let fileInput: HTMLInputElement | null = $state(null);
   let pdfBusy = $state(false);
   let exportMenuOpen = $state(false);
+  let saveFormatOpen = $state(false);
 
   // The editable zones as one section — section 1 of the export.
   function hfSetOfState(): HfSet {
@@ -979,6 +981,9 @@
   async function handleSave() {
     if (!editor) return;
     exportMenuOpen = false;
+    // A document with no file behind it has no format yet: ask, the way saving an
+    // untitled document does everywhere else, and let Save As do the rest.
+    if (!fileHandle && !documentHasFile) { saveFormatOpen = true; return; }
     if (!(await ensurePassword())) return;
     const json = editor.getJSON() as TiptapNode;
     try {
@@ -1765,6 +1770,7 @@
        callers only say which family to land on. -->
   <StyleManagerDialog bind:open={styleManagerOpen} family={styleManagerFamily} editor={activeEditor} />
   <NoteOptionsDialog bind:open={noteOptionsOpen} />
+  <SaveFormatDialog bind:open={saveFormatOpen} onPick={handleSaveAs} />
 </main>
 
 <style>
diff --git a/src/lib/components/SaveFormatDialog.svelte b/src/lib/components/SaveFormatDialog.svelte
new file mode 100644
index 0000000..82989ed
--- /dev/null
+++ b/src/lib/components/SaveFormatDialog.svelte
@@ -0,0 +1,83 @@
+<script lang="ts">
+  import { t } from '../i18n/i18n.svelte';
+
+  // Asked for a document that has no file behind it yet: the format has to be settled
+  // before the bytes are built, and the download route cannot read one back.
+  let { open = $bindable(false), onPick }: {
+    open?: boolean;
+    onPick: (kind: 'odt' | 'docx') => void;
+  } = $props();
+
+  let dialogEl = $state<HTMLDialogElement | null>(null);
+
+  $effect(() => {
+    const el = dialogEl;
+    if (!el) return;
+    if (open && !el.open) el.showModal();
+    else if (!open && el.open) el.close();
+  });
+
+  function pick(kind: 'odt' | 'docx') {
+    open = false;
+    onPick(kind);
+  }
+</script>
+
+<dialog
+  bind:this={dialogEl}
+  onclose={() => (open = false)}
+  onclick={(e) => e.target === dialogEl && (open = false)}
+  aria-label={t().dialogs.chooseFormat}
+>
+  <div class="body">
+    <h2>{t().dialogs.chooseFormat}</h2>
+    <button class="format" onclick={() => pick('odt')}>OpenDocument Text (.odt)</button>
+    <button class="format" onclick={() => pick('docx')}>Word Document (.docx)</button>
+    <div class="actions">
+      <button onclick={() => (open = false)}>{t().common.cancel}</button>
+    </div>
+  </div>
+</dialog>
+
+<style>
+  dialog {
+    /* The global reset zeroes every margin, which also takes the auto centring a
+       modal <dialog> gets by default. */
+    margin: auto;
+    border: none;
+    border-radius: 8px;
+    padding: 0;
+    background: var(--color-surface);
+    color: var(--color-text);
+    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
+  }
+
+  dialog::backdrop { background: rgba(0, 0, 0, 0.35); }
+
+  .body {
+    display: flex;
+    flex-direction: column;
+    gap: 8px;
+    width: 300px;
+    padding: 18px 20px 16px;
+    font-family: var(--font-sans);
+    font-size: 0.85rem;
+  }
+
+  h2 { font-size: 1rem; margin-bottom: 4px; }
+
+  button {
+    border: 1px solid var(--color-border);
+    border-radius: var(--radius);
+    background: var(--color-surface);
+    color: var(--color-text);
+    padding: 7px 14px;
+    font: inherit;
+    text-align: left;
+    cursor: pointer;
+  }
+  button:hover { background: var(--color-btn-hover); }
+
+  .actions { display: flex; justify-content: flex-end; margin-top: 4px; }
+  .actions button { text-align: center; }
+</style>
diff --git a/src/lib/export/CLAUDE.md b/src/lib/export/CLAUDE.md
index 577f8ad..25b10ba 100644
--- a/src/lib/export/CLAUDE.md
+++ b/src/lib/export/CLAUDE.md
@@ -11,6 +11,8 @@ are built, because the download route (Brave ships with the File System Access A
 read a changed name back from the browser's dialog — and Chrome's macOS save panel has no format
 popup and admits only the first picker type's extensions anyway. The chosen format is the
 document's from then on; a template follows the document's format (`.ott`, or `.dotx` for `.docx`).
+Save on a document with no file behind it therefore asks first (`SaveFormatDialog`, App.svelte)
+and hands over to Save As — the same beat as saving an untitled document elsewhere.
 
 `saveFile.ts` picks the path: `showSaveFilePicker` where there is one, else a download —
 Gecko has none and Brave disables the whole File System Access API by default. The first
diff --git a/src/lib/i18n/locales/de.ts b/src/lib/i18n/locales/de.ts
index f7f904e..c1eb288 100644
--- a/src/lib/i18n/locales/de.ts
+++ b/src/lib/i18n/locales/de.ts
@@ -1082,6 +1082,7 @@ const de: Messages = {
     confirmReplace: 'Beim Öffnen dieser Datei wird das aktuelle Dokument ersetzt. Fortfahren?',
     openedWithLimitations: (list) => `Mit Einschränkungen geöffnet:\n• ${list}`,
     couldNotOpen: 'Diese Datei konnte nicht geöffnet werden.',
+    chooseFormat: 'In welchem Format speichern?',
     couldNotSave: 'Diese Datei konnte nicht gespeichert werden.',
     scriptBlocked: 'Ein Teil der App konnte nicht geladen werden — ein Skript-Blocker (uBlock Origin, NoScript, strenger Schutzmodus) verhindert das. Erlaube diese Seite und versuche es erneut.',
     couldNotExportPdf: 'PDF-Export nicht möglich.',
diff --git a/src/lib/i18n/locales/en.ts b/src/lib/i18n/locales/en.ts
index a328eb1..c2290b8 100644
--- a/src/lib/i18n/locales/en.ts
+++ b/src/lib/i18n/locales/en.ts
@@ -1088,6 +1088,7 @@ const en = {
     confirmReplace: 'Opening this file will replace the current document. Continue?',
     openedWithLimitations: (list: string) => `Opened with limitations:\n• ${list}`,
     couldNotOpen: 'Could not open this file.',
+    chooseFormat: 'Save in which format?',
     couldNotSave: 'Could not save this file.',
     scriptBlocked: 'Part of the app could not be loaded — a script blocker (uBlock Origin, NoScript, strict privacy mode) is blocking it. Allow this site and try again.',
     couldNotExportPdf: 'Could not export to PDF.',
diff --git a/tests/dom/run.mjs b/tests/dom/run.mjs
index 227f22d..361ebb5 100644
--- a/tests/dom/run.mjs
+++ b/tests/dom/run.mjs
@@ -30,6 +30,19 @@ try {
   await page.reload({ waitUntil: 'load' });
   await page.waitForSelector('.tiptap', { timeout: 15_000 });
 
+  // Save on a document with no file behind it settles the format first: the download
+  // route cannot read one back from the browser's own dialog.
+  await page.evaluate(() => { window.showSaveFilePicker = undefined; });
+  await page.click('.tiptap');
+  await page.keyboard.type('Format first');
+  await page.keyboard.press(`${MOD}+s`);
+  const [firstSave] = await Promise.all([
+    page.waitForEvent('download', { timeout: 30_000 }),
+    page.locator('dialog[open] button', { hasText: '(.docx)' }).first().click(),
+  ]);
+  check(firstSave.suggestedFilename().endsWith('.docx'),
+    `Ctrl+S on an unsaved document asks for the format (${firstSave.suggestedFilename()})`);
+
   // A multi-page corpus document, through the file input (no picker in headless).
   await page.setInputFiles('input.file-input[accept*=".odt"]', join(ROOT, 'tests/corpus/05-breaks.odt'));
   await page.waitForFunction(() => (document.querySelector('.tiptap')?.textContent ?? '').length > 200,