feat: in-app chat replay viewer — read .chat.json/.chat.jsonl without leaving the app

Up to now, the app saved chat data (4.6.2 VOD replay, 4.6.3 live
capture) but had no way to view it — users had to open the file in
Notepad or write a custom parser. New in-app modal closes that loop:
queue items with a sibling .chat.json or .chat.jsonl get a "View
chat" button next to Open file / Show in folder; click pops a modal
with a scrollable, filterable, formatted message list.

Server:
- New ipcMain.handle("read-chat-file") parses both formats. JSON
  Lines (.jsonl) is split per line, header row skipped, malformed
  lines silently dropped — that way a partial / killed live capture
  still renders. JSON object (.json) is the VOD replay shape with
  messages array. Hard-capped at 50k messages so a multi-day archive
  can't kill the renderer; truncation is reported via {truncated,
  total} in the result.

Renderer:
- New chatViewerModal in index.html — full-height list with a filter
  input + status line.
- openChatViewer(filePath, title) loads the file via IPC, normalises
  the message shape (supports both .chat.json and .chat.jsonl
  fields), renders in 500-message chunks via setTimeout(0) so the
  main thread stays responsive on a 30k-message archive.
- Each row: time marker (offset for replays, wall-clock for live),
  user (in their stored color), message text. Non-msg event types
  (subs, raids, clears) get a faint italic [type] tag.
- Filter substring-matches user OR text, case-insensitive, instant.
- Esc + outside-click + the close-x dismiss; Esc handler in
  closeTopmostOpenModal lists the chat viewer first so a user
  with multiple modals open closes the foreground one.

Queue UI:
- renderQueueItemFileActions detects sibling chat files (regex
  /\.chat\.json(l)?$/) in item.outputFiles and surfaces the View
  chat button. The button is shown for both 4.6.2-style replays
  and 4.6.3-style live captures because both formats parse.

DE + EN locales for the button label, loading state, error,
message count, truncation suffix.

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

src/index.html

@@ -136,6 +136,19 @@
         </div>
     </div>
 
+    <!-- Chat Replay Viewer Modal -->
+    <div class="modal-overlay" id="chatViewerModal">
+        <div class="modal" style="max-width: 800px; height: 80vh; display:flex; flex-direction:column;">
+            <button class="modal-close" onclick="closeChatViewer()">x</button>
+            <h2 id="chatViewerTitle" style="margin-top:0;">Chat replay</h2>
+            <div class="form-row" style="margin-bottom:8px; gap:8px; flex-wrap:wrap; align-items:center;">
+                <input type="text" id="chatViewerFilter" placeholder="Filter..." oninput="onChatViewerFilterChange()" style="flex:1; min-width:160px; background: var(--bg-card); border:1px solid var(--border-soft); border-radius:6px; padding:6px 10px; color:var(--text); font-size:13px;">
+                <span id="chatViewerStatus" style="color:var(--text-secondary); font-size:12px;"></span>
+            </div>
+            <div id="chatViewerList" style="flex:1; overflow-y:auto; background: var(--bg-main); border:1px solid var(--border-soft); border-radius:6px; padding:8px; font-family: 'Consolas', monospace; font-size: 12px;"></div>
+        </div>
+    </div>
+
     <!-- Template Guide Modal -->
     <div class="modal-overlay" id="templateGuideModal">
         <div class="modal template-guide-modal">

src/main.ts

@@ -5693,6 +5693,58 @@ ipcMain.handle('run-storage-cleanup', (_, options?: { dryRun?: boolean }): Clean
     return runStorageCleanup({ dryRun: options?.dryRun === true });
 });
 
+// Read a chat-replay (.chat.json) or live-chat (.chat.jsonl) file and
+// return a normalized message list the renderer can display directly.
+// Caps at 50k messages to stop a runaway file from killing the renderer.
+ipcMain.handle('read-chat-file', (_, filePath: string): { success: boolean; error?: string; format?: 'replay' | 'live'; messages?: Array<Record<string, unknown>>; truncated?: boolean; total?: number } => {
+    if (typeof filePath !== 'string' || !filePath) return { success: false, error: 'No path' };
+    if (!fs.existsSync(filePath)) return { success: false, error: 'File not found' };
+
+    const MAX_MESSAGES = 50000;
+    try {
+        const raw = fs.readFileSync(filePath, 'utf-8');
+        if (filePath.toLowerCase().endsWith('.jsonl')) {
+            // JSON Lines (live chat): one object per line, first line may be header
+            const messages: Array<Record<string, unknown>> = [];
+            let truncated = false;
+            const lines = raw.split('\n');
+            let total = 0;
+            for (const line of lines) {
+                const trimmed = line.trim();
+                if (!trimmed) continue;
+                try {
+                    const obj = JSON.parse(trimmed);
+                    if (obj && typeof obj === 'object' && obj.type !== 'header') {
+                        total++;
+                        if (messages.length < MAX_MESSAGES) messages.push(obj);
+                        else truncated = true;
+                    }
+                } catch { /* skip bad lines */ }
+            }
+            return { success: true, format: 'live', messages, truncated, total };
+        }
+
+        // .chat.json (VOD replay) — single object with messages array
+        const parsed = JSON.parse(raw);
+        if (!parsed || typeof parsed !== 'object' || !Array.isArray(parsed.messages)) {
+            return { success: false, error: 'Unsupported chat file format' };
+        }
+        const total = parsed.messages.length;
+        const messages = parsed.messages.length > MAX_MESSAGES
+            ? parsed.messages.slice(0, MAX_MESSAGES)
+            : parsed.messages;
+        return {
+            success: true,
+            format: 'replay',
+            messages,
+            truncated: total > MAX_MESSAGES,
+            total
+        };
+    } catch (e) {
+        return { success: false, error: String(e) };
+    }
+});
+
 ipcMain.handle('check-folder-writable', (_, folderPath: string): boolean => {
     if (typeof folderPath !== 'string' || !folderPath) return false;
     return isDownloadPathWritable(folderPath);

src/preload.ts

@@ -91,6 +91,7 @@ contextBridge.exposeInMainWorld('api', {
     checkFolderWritable: (path: string) => ipcRenderer.invoke('check-folder-writable', path),
     getStorageStats: () => ipcRenderer.invoke('get-storage-stats'),
     runStorageCleanup: (options?: { dryRun?: boolean }) => ipcRenderer.invoke('run-storage-cleanup', options),
+    readChatFile: (filePath: string) => ipcRenderer.invoke('read-chat-file', filePath),
 
     // Video Cutter
     getVideoInfo: (filePath: string): Promise<VideoInfo | null> => ipcRenderer.invoke('get-video-info', filePath),

src/renderer-globals.d.ts

@@ -257,6 +257,7 @@ interface ApiBridge {
     checkFolderWritable(path: string): Promise<boolean>;
     getStorageStats(): Promise<StorageStatsResult>;
     runStorageCleanup(options?: { dryRun?: boolean }): Promise<CleanupReport>;
+    readChatFile(filePath: string): Promise<{ success: boolean; error?: string; format?: 'replay' | 'live'; messages?: Array<Record<string, unknown>>; truncated?: boolean; total?: number }>;
     getVideoInfo(filePath: string): Promise<VideoInfo | null>;
     extractFrame(filePath: string, timeSeconds: number): Promise<string | null>;
     cutVideo(inputFile: string, startTime: number, endTime: number): Promise<{ success: boolean; outputFile: string | null }>;

src/renderer-locale-de.ts

@@ -232,6 +232,11 @@ const UI_TEXT_DE = {
         openFileFailed: 'Datei konnte nicht geoeffnet werden (evtl. verschoben oder geloescht).',
         outputFilesLabel: '{count} Ausgabedateien',
         retryItem: 'Diesen Eintrag erneut versuchen',
+        viewChat: 'Chat ansehen',
+        viewChatLoading: 'Lade Chat...',
+        viewChatFailed: 'Chat-Datei konnte nicht gelesen werden',
+        viewChatCount: '{count} Nachrichten',
+        viewChatTruncatedSuffix: ' (gekuerzt)',
         statusBarSummary: '{downloading} aktiv, {pending} wartet',
         ctxMoveTop: 'Nach oben verschieben',
         ctxMoveBottom: 'Nach unten verschieben',

src/renderer-locale-en.ts

@@ -232,6 +232,11 @@ const UI_TEXT_EN = {
         openFileFailed: 'Could not open the file (it may have been moved or deleted).',
         outputFilesLabel: '{count} output files',
         retryItem: 'Retry this item',
+        viewChat: 'View chat',
+        viewChatLoading: 'Loading chat...',
+        viewChatFailed: 'Could not read chat file',
+        viewChatCount: '{count} messages',
+        viewChatTruncatedSuffix: ' (truncated)',
         statusBarSummary: '{downloading} dl, {pending} queued',
         ctxMoveTop: 'Move to top',
         ctxMoveBottom: 'Move to bottom',

src/renderer-queue.ts

@@ -17,6 +17,14 @@ function renderQueueItemFileActions(item: QueueItem): string {
     }
     buttons.push(`<button class="queue-detail-btn" onclick="invokeShowInFolder('${safeFirstAttr}')">${escapeHtml(UI_TEXT.queue.showInFolder)}</button>`);
 
+    // Surface a "View chat" button when a sibling chat file exists in the
+    // outputs list. Single click opens the in-app viewer modal.
+    const chatFile = item.outputFiles.find((f) => /\.chat\.json(l)?$/i.test(f));
+    if (chatFile) {
+        const safeChatAttr = chatFile.replace(/'/g, "\\'").replace(/"/g, '&quot;');
+        buttons.push(`<button class="queue-detail-btn" onclick="openChatViewer('${safeChatAttr}', '${escapeHtml(item.title || item.streamer || '').replace(/'/g, "\\'")}')">${escapeHtml(UI_TEXT.queue.viewChat)}</button>`);
+    }
+
     const fileLabel = item.outputFiles.length === 1
         ? safeFirst
         : `${escapeHtml(UI_TEXT.queue.outputFilesLabel.replace('{count}', String(item.outputFiles.length)))}`;

src/renderer.ts

@@ -246,8 +246,157 @@ function openTwitchDevConsole(): void {
     void window.api.openExternal('https://dev.twitch.tv/console/apps');
 }
 
+interface ChatViewerMessage {
+    t?: string;
+    type?: string;
+    u?: string;
+    user?: string;
+    login?: string;
+    color?: string;
+    msg?: string;
+    text?: string;
+    offset?: number;
+    badges?: string;
+    bits?: string;
+    msgId?: string;
+    systemMsg?: string;
+}
+
+let chatViewerMessages: ChatViewerMessage[] = [];
+let chatViewerFormat: 'replay' | 'live' = 'replay';
+
+async function openChatViewer(filePath: string, title: string): Promise<void> {
+    const modal = byId('chatViewerModal');
+    const list = byId('chatViewerList');
+    const status = byId('chatViewerStatus');
+    const filterInput = byId<HTMLInputElement>('chatViewerFilter');
+    byId('chatViewerTitle').textContent = title || UI_TEXT.queue.viewChat;
+    list.replaceChildren();
+    filterInput.value = '';
+    status.textContent = UI_TEXT.queue.viewChatLoading;
+    modal.classList.add('show');
+
+    const result = await window.api.readChatFile(filePath);
+    if (!result.success || !Array.isArray(result.messages)) {
+        status.textContent = UI_TEXT.queue.viewChatFailed + (result.error ? `: ${result.error}` : '');
+        return;
+    }
+
+    chatViewerMessages = result.messages as ChatViewerMessage[];
+    chatViewerFormat = result.format === 'live' ? 'live' : 'replay';
+    status.textContent = UI_TEXT.queue.viewChatCount.replace('{count}', String(result.total ?? chatViewerMessages.length))
+        + (result.truncated ? UI_TEXT.queue.viewChatTruncatedSuffix : '');
+    renderChatViewerList(chatViewerMessages);
+}
+
+function closeChatViewer(): void {
+    byId('chatViewerModal').classList.remove('show');
+    chatViewerMessages = [];
+}
+
+function onChatViewerFilterChange(): void {
+    const filter = byId<HTMLInputElement>('chatViewerFilter').value.trim().toLowerCase();
+    if (!filter) {
+        renderChatViewerList(chatViewerMessages);
+        return;
+    }
+    const filtered = chatViewerMessages.filter((m) => {
+        const u = (m.u || m.user || m.login || '').toLowerCase();
+        const text = (m.msg || m.text || '').toLowerCase();
+        return u.includes(filter) || text.includes(filter);
+    });
+    renderChatViewerList(filtered);
+}
+
+function formatChatTimeMarker(m: ChatViewerMessage): string {
+    if (chatViewerFormat === 'replay' && typeof m.offset === 'number') {
+        const total = Math.max(0, Math.floor(m.offset));
+        const h = Math.floor(total / 3600);
+        const min = Math.floor((total % 3600) / 60);
+        const sec = total % 60;
+        return `${h.toString().padStart(2, '0')}:${min.toString().padStart(2, '0')}:${sec.toString().padStart(2, '0')}`;
+    }
+    if (m.t) {
+        try {
+            const d = new Date(m.t);
+            const h = d.getHours().toString().padStart(2, '0');
+            const min = d.getMinutes().toString().padStart(2, '0');
+            const sec = d.getSeconds().toString().padStart(2, '0');
+            return `${h}:${min}:${sec}`;
+        } catch { /* ignore */ }
+    }
+    return '';
+}
+
+function renderChatViewerList(messages: ChatViewerMessage[]): void {
+    const list = byId('chatViewerList');
+    list.replaceChildren();
+    // Render in chunks to keep main thread responsive on big files.
+    const CHUNK = 500;
+    let idx = 0;
+    const renderChunk = (): void => {
+        if (idx >= messages.length) return;
+        const fragment = document.createDocumentFragment();
+        const end = Math.min(idx + CHUNK, messages.length);
+        for (let i = idx; i < end; i++) {
+            const m = messages[i];
+            const row = document.createElement('div');
+            row.style.padding = '2px 0';
+            row.style.lineHeight = '1.5';
+
+            const time = formatChatTimeMarker(m);
+            if (time) {
+                const tSpan = document.createElement('span');
+                tSpan.style.color = 'var(--text-secondary)';
+                tSpan.style.marginRight = '6px';
+                tSpan.textContent = `[${time}]`;
+                row.appendChild(tSpan);
+            }
+
+            const user = m.u || m.user || m.login || '';
+            if (user) {
+                const uSpan = document.createElement('span');
+                uSpan.style.fontWeight = '600';
+                uSpan.style.color = m.color || 'var(--accent)';
+                uSpan.style.marginRight = '4px';
+                uSpan.textContent = `${user}:`;
+                row.appendChild(uSpan);
+            }
+
+            const msgSpan = document.createElement('span');
+            msgSpan.textContent = m.msg || m.text || '';
+            row.appendChild(msgSpan);
+
+            // System events (subs, raids, deletions) get a faint bracketed prefix
+            const isMessageType = m.type === 'msg' || !m.type;
+            if (!isMessageType) {
+                const tag = document.createElement('span');
+                tag.style.color = 'var(--text-secondary)';
+                tag.style.fontStyle = 'italic';
+                tag.style.marginRight = '4px';
+                tag.textContent = `[${m.type}]`;
+                row.insertBefore(tag, row.firstChild);
+            }
+
+            fragment.appendChild(row);
+        }
+        list.appendChild(fragment);
+        idx = end;
+        if (idx < messages.length) {
+            window.setTimeout(renderChunk, 0);
+        }
+    };
+    renderChunk();
+}
+
 function closeTopmostOpenModal(): boolean {
-    // Try each known modal in priority order: clip dialog, template guide, update modal
+    // Try each known modal in priority order
+    const chatViewerModal = document.getElementById('chatViewerModal');
+    if (chatViewerModal?.classList.contains('show')) {
+        closeChatViewer();
+        return true;
+    }
+
     const clipModal = document.getElementById('clipModal');
     if (clipModal?.classList.contains('show')) {
         closeClipDialog();