fix: bookmark toggle is optimistic and no longer fails silently

The detail-page bookmark toggle awaited the round-trip before updating and
had no catch — a failed create/delete threw unhandled and the user saw
nothing. It now flips optimistically (placeholder reconciled with the server
row on success), rolls back on error, and surfaces a toast, matching the
sibling like/dislike buttons.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/Cargo.lock

@@ -1558,7 +1558,7 @@ checksum = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
 
 [[package]]
 name = "mangalord"
-version = "0.115.0"
+version = "0.115.1"
 dependencies = [
  "anyhow",
  "argon2",

backend/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mangalord"
-version = "0.115.0"
+version = "0.115.1"
 edition = "2021"
 default-run = "mangalord"
 

frontend/e2e/detail-bookmark.spec.ts

@@ -0,0 +1,115 @@
+import { test, expect, type Page } from './fixtures';
+
+// The detail-page bookmark toggle should feel instant (optimistic) and never
+// fail silently: a rejected create/delete must roll the button back and
+// surface a toast.
+
+const mangaId = 'b1111111-1111-1111-1111-111111111111';
+
+async function mockDetail(page: Page) {
+    await page.route('**/api/v1/auth/config', (r) =>
+        r.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({ self_register_enabled: true, private_mode: false })
+        })
+    );
+    await page.route('**/api/v1/auth/me', (r) =>
+        r.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({
+                user: { id: 'u1', username: 'reader', created_at: '2026-01-01T00:00:00Z', is_admin: false }
+            })
+        })
+    );
+    await page.route('**/api/v1/auth/me/preferences', (r) =>
+        r.fulfill({ status: 200, contentType: 'application/json', body: '{}' })
+    );
+    await page.route('**/api/v1/me/bookmarks*', (r) =>
+        r.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({ items: [], page: { limit: 50, offset: 0, total: 0 } })
+        })
+    );
+    await page.route(`**/api/v1/mangas/${mangaId}/chapters*`, (r) =>
+        r.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({ items: [], page: { limit: 50, offset: 0, total: 0 } })
+        })
+    );
+    await page.route(`**/api/v1/mangas/${mangaId}/similar`, (r) =>
+        r.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify({ items: [] }) })
+    );
+    await page.route(`**/api/v1/me/read-progress/${mangaId}`, (r) =>
+        r.fulfill({ status: 404, contentType: 'application/json', body: '{"error":{"code":"x","message":"x"}}' })
+    );
+    await page.route(`**/api/v1/me/reactions/${mangaId}`, (r) =>
+        r.fulfill({ status: 404, contentType: 'application/json', body: '{"error":{"code":"x","message":"x"}}' })
+    );
+    await page.route(`**/api/v1/mangas/${mangaId}`, (r) =>
+        r.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({
+                id: mangaId, title: 'Berserk', status: 'ongoing', alt_titles: [], description: null,
+                cover_image_path: null, created_at: '2026-01-01T00:00:00Z', updated_at: '2026-01-01T00:00:00Z',
+                authors: [], genres: [], tags: [], content_warnings: [], chapter_storage_bytes: 0
+            })
+        })
+    );
+}
+
+test('bookmark toggles optimistically before the request resolves', async ({ page }) => {
+    await mockDetail(page);
+
+    // Hold the create request open so we can observe the pre-response state.
+    let release: () => void = () => {};
+    const gate = new Promise<void>((resolve) => {
+        release = resolve;
+    });
+    await page.route('**/api/v1/bookmarks', async (route) => {
+        await gate;
+        await route.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({
+                id: 'bk1', user_id: 'u1', manga_id: mangaId, chapter_id: null, page: null,
+                created_at: '2026-01-01T00:00:00Z'
+            })
+        });
+    });
+
+    await page.goto(`/manga/${mangaId}`);
+    const btn = page.getByTestId('bookmark-toggle');
+    await expect(btn).toHaveAttribute('aria-pressed', 'false');
+
+    await btn.click();
+    // Optimistic: reflects bookmarked state while the POST is still pending.
+    await expect(btn).toHaveAttribute('aria-pressed', 'true');
+
+    release();
+    // Stays bookmarked once the server confirms.
+    await expect(btn).toHaveAttribute('aria-pressed', 'true');
+});
+
+test('a failed bookmark rolls back and shows an error toast', async ({ page }) => {
+    await mockDetail(page);
+    await page.route('**/api/v1/bookmarks', (route) =>
+        route.fulfill({
+            status: 500,
+            contentType: 'application/json',
+            body: JSON.stringify({ error: { code: 'internal', message: 'boom' } })
+        })
+    );
+
+    await page.goto(`/manga/${mangaId}`);
+    const btn = page.getByTestId('bookmark-toggle');
+    await btn.click();
+
+    // Rolls back to un-bookmarked, and the failure is surfaced (not silent).
+    await expect(btn).toHaveAttribute('aria-pressed', 'false');
+    await expect(page.getByTestId('toast')).toBeVisible();
+});

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.115.0",
+  "version": "0.115.1",
   "private": true,
   "type": "module",
   "scripts": {

frontend/src/routes/manga/[id]/+page.svelte

@@ -18,6 +18,7 @@
     import { listTags, type Tag } from '$lib/api/tags';
     import type { ContentWarning } from '$lib/api/page_tags';
     import { session } from '$lib/session.svelte';
+    import { toast } from '$lib/toast.svelte';
     import Chip from '$lib/components/Chip.svelte';
     import MangaCard from '$lib/components/MangaCard.svelte';
     import ReactionButtons from '$lib/components/ReactionButtons.svelte';
@@ -155,17 +156,36 @@
     });
 
     async function toggleBookmark() {
-        if (!session.user) return;
+        if (!session.user || busy) return;
+        const existing = mangaBookmark;
+        // Snapshot for rollback — the update below is applied optimistically
+        // so the button flips instantly, then reconciled/reverted.
+        const snapshot = bookmarks;
         busy = true;
         try {
-            if (mangaBookmark) {
-                const id = mangaBookmark.id;
-                await deleteBookmark(id);
-                bookmarks = bookmarks.filter((b) => b.id !== id);
+            if (existing) {
+                bookmarks = bookmarks.filter((b) => b.id !== existing.id);
+                await deleteBookmark(existing.id);
             } else {
+                // Temporary placeholder so the derived `mangaBookmark` flips
+                // immediately; swapped for the server row (with its real id)
+                // once the POST returns.
+                const tempId = `optimistic-${crypto.randomUUID()}`;
+                const placeholder: Bookmark = {
+                    id: tempId,
+                    user_id: session.user.id,
+                    manga_id: manga.id,
+                    chapter_id: null,
+                    page: null,
+                    created_at: new Date().toISOString()
+                };
+                bookmarks = [placeholder, ...bookmarks];
                 const b = await createBookmark({ manga_id: manga.id });
-                bookmarks = [b, ...bookmarks];
+                bookmarks = [b, ...bookmarks.filter((x) => x.id !== tempId)];
             }
+        } catch {
+            bookmarks = snapshot;
+            toast.error(existing ? 'Could not remove bookmark.' : 'Could not add bookmark.');
         } finally {
             busy = false;
         }