release: 4.5.8 fsync atomic writes, parallel filename race, UI persistence

Stability + UX cycle.

- saveConfig and writeQueueToDisk now use openSync+writeSync+fsyncSync+
  closeSync+renameSync via writeFileAtomicSync. Survives power loss
  between write and rename (used to leave the renamed file empty and
  silently reset config / queue on next launch).
- Per-item claimedFilenames map fixes the parallel-download race where
  one item finishing wiped sibling claims and let a third item collide
  on the same output path.
- Renderer queue lookup by [data-id] (no more index drift), active tab
  persisted in localStorage, Escape closes the topmost open modal,
  Ctrl/Cmd+1..5 jumps tabs.

See docs/IMPROVEMENT_LOG.md for the dated rationale and regression run.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/IMPROVEMENT_LOG.md

@@ -0,0 +1,45 @@
+# Improvement Log
+
+Dated entries from improvement cycles. Newest at top.
+
+## 2026-05-03 — Cycle 1: stability & UX polish
+
+Three independent improvements landed this cycle.
+
+### 1. Atomic file writes survive power loss / crash mid-write (correctness)
+
+- **Files**: `src/main.ts` — new `writeFileAtomicSync` helper, `saveConfig`, `writeQueueToDisk`.
+- **Problem**: `saveConfig` and `writeQueueToDisk` used `writeFileSync` + `renameSync`. Node's `writeFileSync` does NOT call `fsync` — the OS may report the rename complete while the file content still sits in the write cache. A power loss / kernel panic between `writeFileSync` and `renameSync` could leave the renamed file empty or truncated. On next launch, `JSON.parse` throws and the app silently falls back to defaults (config) or `[]` (queue). Users would see "settings reset" / "queue lost" with no diagnostic in the debug log beyond a `console.error`.
+- **Fix**: `openSync(tmp, 'w')` → `writeSync(fd, buffer, 0, len, 0)` → `fsyncSync(fd)` → `closeSync(fd)` → `renameSync`. The `fsyncSync` is wrapped in an inner try (some filesystems reject it, e.g. network shares); failure there is non-fatal but the close + rename order is always preserved. The Windows copy/unlink fallback for "rename failed because target locked" is kept.
+
+### 2. Per-item filename claims fix parallel-download race (race condition + dead-code cleanup)
+
+- **Files**: `src/main.ts` — `ensureUniqueFilename`, new `releaseClaimedFilenamesForItem`, every download call site, `splitMergedFile` signature.
+- **Problem**: `claimedFilenames` was a global `Set<string>` and `processOneQueueItem` did `claimedFilenames.clear()` in its `finally`. With parallel downloads enabled (max 2), when item A finished, the `clear()` wiped item B's reservations too. In the narrow window between B claiming a filename via `ensureUniqueFilename` and streamlink actually writing the first bytes to disk, a third item entering the freed slot could compute the SAME filename (claim set empty, file not yet on disk) → both downloads would race writing the same path. The dead `releaseClaimedFilename(filePath)` function was defined at line 722 but never called from anywhere.
+- **Fix**: New `Map<itemId, Set<filename>>` tracks which item claimed which filenames. `ensureUniqueFilename(filePath, itemId)` registers per-item; `releaseClaimedFilenamesForItem(itemId)` removes only that item's claims. `splitMergedFile` gained an `itemId` parameter so split-phase claims register correctly. The dead `releaseClaimedFilename` is gone, replaced by the per-item variant.
+
+### 3. Renderer UX polish — robust progress lookup, persisted active tab, keyboard shortcuts (client-side feature)
+
+- **Files**: `src/renderer-queue.ts`, `src/renderer.ts`.
+- **Problem(s)** (small wins bundled as one coherent UX improvement):
+  - `updateQueueItemProgress` indexed `byId('queueList').children[idx]` by array position — fragile if the queue array and DOM ever diverged for a frame (queue mutated after render-fingerprint shortcut, or during the throttled queue-sync window).
+  - The active tab always reset to `vods` on app launch — annoying for users who live in `settings`, `cutter`, or `merge`.
+  - No way to dismiss any of the three modals (`clipModal`, `templateGuideModal`, `updateModal`) without clicking the close button.
+  - No keyboard navigation between tabs (only `Del` and `S` were wired).
+  - The page title used to show the streamer name even when the user was on Settings or Cutter, because `showTab` always preferred `currentStreamer` over the tab title.
+- **Fix**:
+  - Look up queue items by `[data-id="..."]` selector instead of array index. Resilient to mutation between renders. Determinate / indeterminate progress class logic tightened (`isDeterminate = progress > 0 && progress <= 100`).
+  - Active tab persisted to `localStorage` on every `showTab`; restored on init via `loadPersistedActiveTab`, whitelisted to known tab IDs (`vods | clips | cutter | merge | settings`) so a future rename can't strand users on a missing tab. Title logic fixed: streamer name only appears in the page title when the VODs tab is active.
+  - `Escape` closes the topmost open modal regardless of focus (priority order: clip dialog → template guide → update modal). Works while typing in a modal input.
+  - `Ctrl+1..5` (or `Cmd+1..5` on macOS) jumps directly to a tab. Existing `Del` (delete selected) and `S` (start/pause) shortcuts continue to work and remain blocked while typing in inputs.
+
+### Regression
+
+- `npm run build` — clean (TypeScript strict, 0 errors, 0 new warnings).
+- `node scripts/smoke-test-update-version-logic.js` — passed.
+- `node scripts/smoke-test-merge-split-logic.js` — passed.
+- `node scripts/smoke-test.js` — passed (37 VODs listed, queue add OK, preflight green, `issues: []`).
+- `node scripts/smoke-test-template-guide.js` — passed (17 variable rows, live preview reactive, `failures: []`).
+- `node scripts/smoke-test-full.js` — passed (`failures: []`, `runtimeIssues: []`; flows verified: language switch, queue add, duplicate prevention, runtime metrics, clip queue, pause/resume, retry, reorder, media cut/merge, update check).
+
+ESLint reports 36 pre-existing warnings and 1 pre-existing error (control-character regex in `sanitizeFilenamePart`); none new from this cycle.

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "twitch-vod-manager",
-  "version": "4.5.7",
+  "version": "4.5.8",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "twitch-vod-manager",
-      "version": "4.5.7",
+      "version": "4.5.8",
       "license": "MIT",
       "dependencies": {
         "axios": "^1.6.0",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "twitch-vod-manager",
-  "version": "4.5.7",
+  "version": "4.5.8",
   "description": "Twitch VOD Manager - Download Twitch VODs easily",
   "main": "dist/main.js",
   "author": "xRangerDE",

src/main.ts

@@ -268,17 +268,33 @@ function loadConfig(): Config {
     return normalizeConfigTemplates(defaultConfig);
 }
 
-function saveConfig(config: Config): void {
-    const tmpPath = CONFIG_FILE + '.tmp';
+function writeFileAtomicSync(targetPath: string, payload: string | Buffer): void {
+    const buffer = Buffer.isBuffer(payload) ? payload : Buffer.from(payload, 'utf-8');
+    const tmpPath = targetPath + '.tmp';
+
+    let fd: number | null = null;
     try {
-        fs.writeFileSync(tmpPath, JSON.stringify(config, null, 2));
+        fd = fs.openSync(tmpPath, 'w');
+        fs.writeSync(fd, buffer, 0, buffer.length, 0);
+        try { fs.fsyncSync(fd); } catch { /* fsync may fail on some FS; rename is still safer than nothing */ }
+    } finally {
+        if (fd !== null) {
+            try { fs.closeSync(fd); } catch { }
+        }
+    }
+
     try {
-            fs.renameSync(tmpPath, CONFIG_FILE);
+        fs.renameSync(tmpPath, targetPath);
     } catch {
-            // On Windows, rename can fail if target exists in some edge cases
-            fs.copyFileSync(tmpPath, CONFIG_FILE);
+        // On Windows, rename can fail if target exists or is locked. Fall back to copy.
+        fs.copyFileSync(tmpPath, targetPath);
         try { fs.unlinkSync(tmpPath); } catch { }
     }
+}
+
+function saveConfig(config: Config): void {
+    try {
+        writeFileAtomicSync(CONFIG_FILE, JSON.stringify(config, null, 2));
     } catch (e) {
         console.error('Error saving config:', e);
     }
@@ -329,16 +345,8 @@ function writeQueueToDisk(queue: QueueItem[]): void {
         return;
     }
 
-    const tmpPath = QUEUE_FILE + '.tmp';
     try {
-        fs.writeFileSync(tmpPath, JSON.stringify(queue, null, 2));
-        try {
-            fs.renameSync(tmpPath, QUEUE_FILE);
-        } catch {
-            // On Windows, rename can fail if target exists in some edge cases
-            fs.copyFileSync(tmpPath, QUEUE_FILE);
-            try { fs.unlinkSync(tmpPath); } catch { }
-        }
+        writeFileAtomicSync(QUEUE_FILE, JSON.stringify(queue, null, 2));
     } catch (e) {
         console.error('Error saving queue:', e);
     }
@@ -704,8 +712,9 @@ function formatDurationDashed(seconds: number): string {
 }
 
 const claimedFilenames = new Set<string>();
+const itemClaimedFilenames = new Map<string, Set<string>>();
 
-function ensureUniqueFilename(filePath: string): string {
+function ensureUniqueFilename(filePath: string, itemId: string | null = null): string {
     const dir = path.dirname(filePath);
     const ext = path.extname(filePath);
     const base = path.basename(filePath, ext);
@@ -716,11 +725,22 @@ function ensureUniqueFilename(filePath: string): string {
         candidate = path.join(dir, `${base}_${counter}${ext}`);
     }
     claimedFilenames.add(candidate);
+    if (itemId) {
+        let perItem = itemClaimedFilenames.get(itemId);
+        if (!perItem) {
+            perItem = new Set();
+            itemClaimedFilenames.set(itemId, perItem);
+        }
+        perItem.add(candidate);
+    }
     return candidate;
 }
 
-function releaseClaimedFilename(filePath: string): void {
-    claimedFilenames.delete(filePath);
+function releaseClaimedFilenamesForItem(itemId: string): void {
+    const perItem = itemClaimedFilenames.get(itemId);
+    if (!perItem) return;
+    for (const f of perItem) claimedFilenames.delete(f);
+    itemClaimedFilenames.delete(itemId);
 }
 
 function sanitizeFilenamePart(input: string, fallback = 'unnamed'): string {
@@ -2124,7 +2144,8 @@ async function splitMergedFile(
     partDurationSec: number,
     totalDurationSec: number,
     filenameGenerator: (partNum: number) => string,
-    onProgress: (currentPart: number, totalParts: number) => void
+    onProgress: (currentPart: number, totalParts: number) => void,
+    itemId: string | null = null
 ): Promise<{ success: boolean; files: string[] }> {
     const ffmpegReady = await ensureFfmpegInstalled();
     if (!ffmpegReady) {
@@ -2143,7 +2164,7 @@ async function splitMergedFile(
 
         const startSec = i * partDurationSec;
         const thisDuration = Math.min(partDurationSec, totalDurationSec - startSec);
-        const outputFile = ensureUniqueFilename(path.join(outputFolder, filenameGenerator(i + 1)));
+        const outputFile = ensureUniqueFilename(path.join(outputFolder, filenameGenerator(i + 1)), itemId);
 
         onProgress(i + 1, numParts);
 
@@ -2490,7 +2511,7 @@ async function downloadVOD(
                 const remainingDuration = clip.durationSec - (i * partDuration);
                 const thisDuration = Math.min(partDuration, remainingDuration);
 
-                const partFilename = ensureUniqueFilename(makeClipFilename(partNum, startOffset, thisDuration));
+                const partFilename = ensureUniqueFilename(makeClipFilename(partNum, startOffset, thisDuration), item.id);
 
                 const result = await downloadVODPart(
                     item.url,
@@ -2513,7 +2534,7 @@ async function downloadVOD(
             };
         } else {
             // Single clip file
-            const filename = ensureUniqueFilename(makeClipFilename(clip.startPart, clip.startSec, clip.durationSec));
+            const filename = ensureUniqueFilename(makeClipFilename(clip.startPart, clip.startSec, clip.durationSec), item.id);
             return await downloadVODPart(
                 item.url,
                 filename,
@@ -2536,7 +2557,7 @@ async function downloadVOD(
             1,
             0,
             totalDuration
-        ));
+        ), item.id);
         return await downloadVODPart(item.url, filename, null, null, onProgress, item.id, 1, 1);
     } else {
         // Part-based download
@@ -2557,7 +2578,7 @@ async function downloadVOD(
                 i + 1,
                 startSec,
                 duration
-            ));
+            ), item.id);
 
             const result = await downloadVODPart(
                 item.url,
@@ -2642,7 +2663,7 @@ async function processDownloadMergeGroup(
             saveQueue(downloadQueue);
 
             const vodItem = mg.items[i];
-            const tmpFilename = ensureUniqueFilename(path.join(folder, `merge_tmp_${i}_${Date.now()}.mp4`));
+            const tmpFilename = ensureUniqueFilename(path.join(folder, `merge_tmp_${i}_${Date.now()}.mp4`), item.id);
 
             // Calculate progress weighting per VOD
             const vodDuration = parseDuration(vodItem.duration_str);
@@ -2781,7 +2802,8 @@ async function processDownloadMergeGroup(
                 currentPart,
                 totalParts
             });
-        }
+        },
+        item.id
     );
 
     if (!splitResult.success) {
@@ -2932,8 +2954,8 @@ async function processOneQueueItem(item: QueueItem): Promise<void> {
     } finally {
         activeDownloads.delete(item.id);
         cancelledItemIds.delete(item.id);
-        // Release any filenames claimed during this download (prevents stale claims blocking re-downloads)
-        claimedFilenames.clear();
+        // Release only THIS item's claimed filenames (other parallel downloads keep their claims)
+        releaseClaimedFilenamesForItem(item.id);
     }
 }
 

src/renderer-queue.ts

@@ -180,22 +180,27 @@ async function createMergeGroupFromSelection(): Promise<void> {
 }
 
 function updateQueueItemProgress(progress: DownloadProgress): void {
-    const items = byId('queueList').children;
-    const idx = queue.findIndex(i => i.id === progress.id);
-    if (idx < 0 || idx >= items.length) return;
+    // Lookup by data-id attribute, not array index — survives queue mutation between renders
+    const safeId = String(progress.id ?? '').replace(/"/g, '\\"');
+    if (!safeId) return;
+    const el = byId('queueList').querySelector(`[data-id="${safeId}"]`) as HTMLElement | null;
+    if (!el) return;
 
-    const el = items[idx];
-    const bar = el.querySelector('.queue-progress-bar') as HTMLElement;
-    const text = el.querySelector('.queue-progress-text') as HTMLElement;
-    const meta = el.querySelector('.queue-meta') as HTMLElement;
+    const item = queue.find(i => i.id === progress.id);
+    if (!item) return;
+
+    const bar = el.querySelector('.queue-progress-bar') as HTMLElement | null;
+    const text = el.querySelector('.queue-progress-text') as HTMLElement | null;
+    const meta = el.querySelector('.queue-meta') as HTMLElement | null;
 
     if (bar) {
-        const pct = progress.progress > 0 ? Math.min(100, progress.progress) : 0;
+        const isDeterminate = progress.progress > 0 && progress.progress <= 100;
+        const pct = isDeterminate ? Math.min(100, progress.progress) : 0;
         bar.style.width = `${pct}%`;
-        bar.className = `queue-progress-bar${progress.progress <= 0 ? ' indeterminate' : ''}`;
+        bar.className = `queue-progress-bar${isDeterminate ? '' : ' indeterminate'}`;
     }
-    if (text) text.textContent = getQueueProgressText(queue[idx]);
-    if (meta) meta.textContent = getQueueMetaText(queue[idx]);
+    if (text) text.textContent = getQueueProgressText(item);
+    if (meta) meta.textContent = getQueueMetaText(item);
 }
 
 function toggleQueueDetails(id: string): void {

src/renderer.ts

@@ -45,6 +45,9 @@ async function init(): Promise<void> {
     initQueueDragDrop();
     updateDownloadButtonState();
 
+    // Restore last active tab from previous session (default 'vods')
+    showTab(loadPersistedActiveTab());
+
     window.api.onQueueUpdated((q: QueueItem[]) => {
         queue = mergeQueueState(Array.isArray(q) ? q : []);
         renderQueue();
@@ -126,9 +129,28 @@ async function init(): Promise<void> {
 
     // Keyboard shortcuts
     document.addEventListener('keydown', (e) => {
-        // Skip if user is typing in an input field
+        // Esc closes any open modal — works regardless of focus, so users can dismiss
+        // a modal that took focus from inside an input field
+        if (e.key === 'Escape') {
+            if (closeTopmostOpenModal()) {
+                e.preventDefault();
+                return;
+            }
+        }
+
+        // Skip rest if user is typing in an input field
         if (e.target instanceof HTMLInputElement || e.target instanceof HTMLTextAreaElement || e.target instanceof HTMLSelectElement) return;
 
+        // Ctrl+1..5 jumps directly to a tab (Cmd on macOS via metaKey)
+        if ((e.ctrlKey || e.metaKey) && !e.altKey && !e.shiftKey && e.key >= '1' && e.key <= '5') {
+            const tabIndex = parseInt(e.key, 10) - 1;
+            if (tabIndex >= 0 && tabIndex < TAB_IDS.length) {
+                e.preventDefault();
+                showTab(TAB_IDS[tabIndex]);
+                return;
+            }
+        }
+
         if (e.key === 'Delete' && selectedQueueIds.length > 0) {
             // Delete selected queue items
             const idsToRemove = [...selectedQueueIds];
@@ -150,6 +172,29 @@ async function init(): Promise<void> {
     scheduleQueueSync(QUEUE_SYNC_DEFAULT_MS);
 }
 
+function closeTopmostOpenModal(): boolean {
+    // Try each known modal in priority order: clip dialog, template guide, update modal
+    const clipModal = document.getElementById('clipModal');
+    if (clipModal?.classList.contains('show')) {
+        closeClipDialog();
+        return true;
+    }
+
+    const templateGuideModal = document.getElementById('templateGuideModal');
+    if (templateGuideModal?.classList.contains('show')) {
+        closeTemplateGuide();
+        return true;
+    }
+
+    const updateModal = document.getElementById('updateModal');
+    if (updateModal?.classList.contains('show')) {
+        dismissUpdateModal();
+        return true;
+    }
+
+    return false;
+}
+
 function formatBytesRenderer(bytes: number): string {
     if (bytes < 1024) return `${bytes} B`;
     if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
@@ -330,16 +375,48 @@ async function syncQueueAndDownloadState(): Promise<void> {
     }
 }
 
+const TAB_IDS = ['vods', 'clips', 'cutter', 'merge', 'settings'] as const;
+const ACTIVE_TAB_STORAGE_KEY = 'twitch-vod-manager:active-tab';
+
+function isKnownTab(value: string): value is typeof TAB_IDS[number] {
+    return (TAB_IDS as readonly string[]).includes(value);
+}
+
+function loadPersistedActiveTab(): string {
+    try {
+        const stored = localStorage.getItem(ACTIVE_TAB_STORAGE_KEY);
+        if (stored && isKnownTab(stored)) return stored;
+    } catch { /* localStorage may be unavailable in privacy modes */ }
+    return 'vods';
+}
+
+function persistActiveTab(tab: string): void {
+    if (!isKnownTab(tab)) return;
+    try { localStorage.setItem(ACTIVE_TAB_STORAGE_KEY, tab); } catch { }
+}
+
 function showTab(tab: string): void {
     queryAll('.nav-item').forEach((i) => i.classList.remove('active'));
     queryAll('.tab-content').forEach((c) => c.classList.remove('active'));
 
-    query(`.nav-item[data-tab="${tab}"]`).classList.add('active');
+    const navItem = query(`.nav-item[data-tab="${tab}"]`);
+    if (!navItem) {
+        // Unknown tab — fall back to vods so the user is never stuck on an empty screen
+        showTab('vods');
+        return;
+    }
+    navItem.classList.add('active');
     byId(tab + 'Tab').classList.add('active');
 
     const titles: Record<string, string> = UI_TEXT.tabs;
 
-    byId('pageTitle').textContent = currentStreamer || titles[tab] || UI_TEXT.appName;
+    // Only show the streamer name on the VODs tab — otherwise the title would
+    // mismatch the tab content (e.g. "streamer X" while on Settings)
+    byId('pageTitle').textContent = (tab === 'vods' && currentStreamer)
+        ? currentStreamer
+        : (titles[tab] || UI_TEXT.appName);
+
+    persistActiveTab(tab);
 }
 
 function parseDurationToSeconds(durStr: string): number {