feat: export conversation as Markdown download

src/components/Chat.tsx

@@ -3,12 +3,13 @@ import { ChatMessageComponent } from './ChatMessage';
 import { ChatInput } from './ChatInput';
 import { TypingIndicator } from './TypingIndicator';
 import type { ChatMessage, ConnectionStatus } from '../types';
-import { Bot, ArrowDown, Loader2, ChevronsDownUp, ChevronsUpDown, Sparkles, Bookmark } from 'lucide-react';
+import { Bot, ArrowDown, Loader2, ChevronsDownUp, ChevronsUpDown, Sparkles, Bookmark, Download } from 'lucide-react';
 import { MessageSearch } from './MessageSearch';
 import { useT } from '../hooks/useLocale';
 import { getLocale, type TranslationKey } from '../lib/i18n';
 import { useToolCollapse } from '../hooks/useToolCollapse';
 import { useBookmarks } from '../hooks/useBookmarks';
+import { exportAsMarkdown, downloadFile } from '../lib/exportConversation';
 
 interface Props {
   messages: ChatMessage[];
@@ -208,6 +209,13 @@ export function Chat({ messages, isGenerating, isLoadingHistory, status, session
   const [showBookmarks, setShowBookmarks] = useState(false);
   const hasToolCalls = useMemo(() => messages.some(m => m.blocks.some(b => b.type === 'tool_use' || b.type === 'tool_result')), [messages]);
 
+  const handleExport = useCallback(() => {
+    const label = sessionKey?.replace(/^agent:[^:]+:/, '') || 'conversation';
+    const md = exportAsMarkdown(messages, label);
+    const safeLabel = label.replace(/[^a-zA-Z0-9_-]/g, '_').slice(0, 40);
+    downloadFile(md, `${safeLabel}-${new Date().toISOString().slice(0, 10)}.md`);
+  }, [messages, sessionKey]);
+
   // Message search
   const [searchOpen, setSearchOpen] = useState(false);
   const [searchQuery, setSearchQuery] = useState('');
@@ -358,7 +366,7 @@ export function Chat({ messages, isGenerating, isLoadingHistory, status, session
           </div>
         )}
         {/* Floating action buttons — sticky to bottom of scroll area */}
-        {(hasToolCalls || showScrollBtn || newMessageCount > 0) && (
+        {(hasToolCalls || messages.length > 0 || showScrollBtn || newMessageCount > 0) && (
           <div className="sticky bottom-3 z-10 flex justify-center pointer-events-none pb-1">
             <div className="flex items-center gap-2 pointer-events-auto">
               {hasToolCalls && (
@@ -382,6 +390,16 @@ export function Chat({ messages, isGenerating, isLoadingHistory, status, session
                   <span className="text-[10px] tabular-nums text-pc-text-muted">{sessionBookmarks.length}</span>
                 </button>
               )}
+              {messages.length > 0 && (
+                <button
+                  onClick={handleExport}
+                  aria-label={t('chat.export')}
+                  title={t('chat.export')}
+                  className="flex items-center gap-1.5 rounded-full border border-pc-border-strong bg-pc-elevated/90 backdrop-blur-lg px-3 py-2 text-xs text-pc-text shadow-lg hover:bg-pc-elevated/90 transition-all hover:shadow-cyan-500/10"
+                >
+                  <Download size={14} className="text-pc-accent-light" />
+                </button>
+              )}
               {(showScrollBtn || newMessageCount > 0) && (
                 <button
                   onClick={() => { scrollToBottom('smooth'); setNewMessageCount(0); }}

src/lib/exportConversation.ts

@@ -0,0 +1,79 @@
+import type { ChatMessage } from '../types';
+
+/**
+ * Export conversation messages as a Markdown string.
+ */
+export function exportAsMarkdown(messages: ChatMessage[], sessionLabel?: string): string {
+  const lines: string[] = [];
+  const title = sessionLabel || 'Conversation';
+  lines.push(`# ${title}`);
+  lines.push(`> Exported from PinchChat on ${new Date().toLocaleString()}`);
+  lines.push('');
+
+  for (const msg of messages) {
+    if (msg.isCompactionSeparator) {
+      lines.push('---');
+      lines.push('*Context compacted*');
+      lines.push('---');
+      lines.push('');
+      continue;
+    }
+
+    const ts = msg.timestamp ? new Date(msg.timestamp).toLocaleString() : '';
+    const roleLabel = msg.role === 'user' ? '👤 User' : msg.role === 'assistant' ? '🤖 Assistant' : '⚙️ System';
+    const header = ts ? `### ${roleLabel} — ${ts}` : `### ${roleLabel}`;
+    lines.push(header);
+    lines.push('');
+
+    // Render blocks
+    for (const block of msg.blocks) {
+      if (block.type === 'text') {
+        lines.push(block.text);
+        lines.push('');
+      } else if (block.type === 'thinking') {
+        lines.push('<details>');
+        lines.push('<summary>💭 Thinking</summary>');
+        lines.push('');
+        lines.push(block.text);
+        lines.push('</details>');
+        lines.push('');
+      } else if (block.type === 'tool_use') {
+        const input = typeof block.input === 'string' ? block.input : JSON.stringify(block.input, null, 2);
+        lines.push(`**🔧 Tool: \`${block.name}\`**`);
+        lines.push('```json');
+        lines.push(input);
+        lines.push('```');
+        lines.push('');
+      } else if (block.type === 'tool_result') {
+        lines.push('**📋 Result:**');
+        lines.push('```');
+        lines.push(block.content.slice(0, 2000) + (block.content.length > 2000 ? '\n...(truncated)' : ''));
+        lines.push('```');
+        lines.push('');
+      }
+    }
+
+    // Fallback to content if no blocks
+    if (msg.blocks.length === 0 && msg.content) {
+      lines.push(msg.content);
+      lines.push('');
+    }
+  }
+
+  return lines.join('\n');
+}
+
+/**
+ * Download text as a file.
+ */
+export function downloadFile(content: string, filename: string, mimeType = 'text/markdown') {
+  const blob = new Blob([content], { type: mimeType });
+  const url = URL.createObjectURL(blob);
+  const a = document.createElement('a');
+  a.href = url;
+  a.download = filename;
+  document.body.appendChild(a);
+  a.click();
+  document.body.removeChild(a);
+  URL.revokeObjectURL(url);
+}

src/lib/i18n.ts

@@ -147,6 +147,7 @@ const en = {
   'message.bookmark': 'Bookmark message',
   'message.removeBookmark': 'Remove bookmark',
   'chat.bookmarks': 'Bookmarks',
+  'chat.export': 'Export conversation',
   'chat.contextCompacted': 'Context compacted — older messages cached locally',
 } as const;
 
@@ -274,6 +275,7 @@ const fr: Record<keyof typeof en, string> = {
   'message.bookmark': 'Marquer le message',
   'message.removeBookmark': 'Retirer le marque-page',
   'chat.bookmarks': 'Marque-pages',
+  'chat.export': 'Exporter la conversation',
   'chat.contextCompacted': 'Contexte compacté — anciens messages en cache local',
 };