diff --git a/packages/ui/src/components/layout/VSCodeLayout.tsx b/packages/ui/src/components/layout/VSCodeLayout.tsx
index 4467a453..bf4f1c7f 100644
--- a/packages/ui/src/components/layout/VSCodeLayout.tsx
+++ b/packages/ui/src/components/layout/VSCodeLayout.tsx
@@ -187,6 +187,19 @@ export const VSCodeLayout: React.FC = () => {
     void vscodeApi.executeCommand('openchamber.setActiveSession', currentSessionId, activeSessionTitle);
   }, [activeSessionTitle, currentSessionId, runtimeApis.vscode]);
 
+  React.useEffect(() => {
+    if (viewMode !== 'editor' || !currentSessionId || !activeSessionTitle) {
+      return;
+    }
+
+    const vscodeApi = runtimeApis.vscode;
+    if (!vscodeApi) {
+      return;
+    }
+
+    void vscodeApi.executeCommand('openchamber.updateSessionEditorTitle', currentSessionId, activeSessionTitle);
+  }, [activeSessionTitle, currentSessionId, runtimeApis.vscode, viewMode]);
+
   // If the active session disappears (e.g., deleted), go back to sessions list
   React.useEffect(() => {
     if (viewMode === 'editor') {
@@ -709,7 +722,7 @@ const VSCodeHeader: React.FC<VSCodeHeaderProps> = ({ title, showBack, onBack, on
           <button
             type="button"
             aria-label={t('sessions.switcher.openAria')}
-            className="flex min-w-0 flex-1 items-center rounded-md px-1 py-0.5 -my-0.5 text-left transition-colors hover:bg-interactive-hover/60 focus-visible:outline-none focus-visible:bg-interactive-hover/60"
+            className="inline-flex min-w-0 max-w-full items-center rounded-md px-1 py-0.5 -my-0.5 text-left transition-colors hover:bg-interactive-hover/60 focus-visible:outline-none focus-visible:bg-interactive-hover/60"
           >
             <span className="text-sm font-medium truncate" title={title}>{title}</span>
           </button>
@@ -717,6 +730,7 @@ const VSCodeHeader: React.FC<VSCodeHeaderProps> = ({ title, showBack, onBack, on
       ) : (
         <h1 className="text-sm font-medium truncate flex-1" title={title}>{title}</h1>
       )}
+      <div className="min-w-0 flex-1" />
       {onNewSession && (
         <button
           onClick={onNewSession}
diff --git a/packages/ui/src/components/session/sidebar/SessionNodeItem.tsx b/packages/ui/src/components/session/sidebar/SessionNodeItem.tsx
index 63895a2a..df4de3f5 100644
--- a/packages/ui/src/components/session/sidebar/SessionNodeItem.tsx
+++ b/packages/ui/src/components/session/sidebar/SessionNodeItem.tsx
@@ -32,6 +32,7 @@ import { useI18n } from '@/lib/i18n';
 import { parseMultiRunSessionTitle } from '@/lib/multirun/title';
 import { MultiRunFusionDialog } from '@/components/multirun/MultiRunFusionDialog';
 import { FusionIcon } from '@/components/icons/FusionIcon';
+import { RuntimeAPIContext } from '@/contexts/runtimeAPIContext';
 
 type Folder = { id: string; name: string; sessionIds: string[] };
 
@@ -261,19 +262,25 @@ function SessionNodeItemComponent(props: Props): React.ReactNode {
   const isMinimalMode = displayMode === 'minimal';
   const isVSCode = React.useMemo(() => isVSCodeRuntime(), []);
   const isElectron = React.useMemo(() => canUseElectronDesktopIPC(), []);
+  const runtimeApis = React.useContext(RuntimeAPIContext);
   const revealOnHoverClass = isVSCode
     ? 'group-hover:opacity-100 group-hover:pointer-events-auto'
     : 'group-hover:opacity-100 group-hover:pointer-events-auto group-focus-within:opacity-100 group-focus-within:pointer-events-auto';
   const hideOnHoverClass = isVSCode
     ? 'group-hover:opacity-0'
     : 'group-hover:opacity-0 group-focus-within:opacity-0';
+  const showOpenInEditorAction = isVSCode;
   const showQuickArchiveAction = !archivedBucket && !mobileVariant;
   const revealPaddingClass = isMinimalMode
     ? (isVSCode
         ? 'group-hover:pr-2'
         : 'group-hover:pr-2 group-focus-within:pr-2')
     : (isVSCode
-        ? (showQuickArchiveAction ? 'group-hover:pr-12' : 'group-hover:pr-5')
+        ? (showQuickArchiveAction && showOpenInEditorAction
+            ? 'group-hover:pr-18'
+            : showQuickArchiveAction || showOpenInEditorAction
+              ? 'group-hover:pr-12'
+              : 'group-hover:pr-5')
         : (showQuickArchiveAction ? 'group-hover:pr-12 group-focus-within:pr-12' : 'group-hover:pr-5 group-focus-within:pr-5'));
   const alwaysActionPaddingClass = showQuickArchiveAction ? 'pr-13' : 'pr-7';
   const suppressNextSelectRef = React.useRef(false);
@@ -609,6 +616,22 @@ function SessionNodeItemComponent(props: Props): React.ReactNode {
     handleDeleteSession(session, { archivedBucket });
   };
 
+  const handleOpenInEditorPointerDown = (event: React.PointerEvent<HTMLButtonElement>) => {
+    event.preventDefault();
+    event.stopPropagation();
+  };
+
+  const handleOpenInEditorMouseDown = (event: React.MouseEvent<HTMLButtonElement>) => {
+    event.preventDefault();
+    event.stopPropagation();
+  };
+
+  const handleOpenInEditorClick = (event: React.MouseEvent<HTMLButtonElement>) => {
+    event.preventDefault();
+    event.stopPropagation();
+    void runtimeApis?.vscode?.executeCommand('openchamber.openSessionInEditor', session.id, sessionTitle);
+  };
+
   const handleRowSelect = (event?: React.MouseEvent<HTMLButtonElement>) => {
     if (suppressNextSelectRef.current) {
       suppressNextSelectRef.current = false;
@@ -936,6 +959,29 @@ function SessionNodeItemComponent(props: Props): React.ReactNode {
                 </TooltipContent>
               </Tooltip>
             ) : null}
+            {showOpenInEditorAction ? (
+              <Tooltip>
+                <TooltipTrigger asChild>
+                  <button
+                    type="button"
+                    className={cn(
+                      'inline-flex items-center justify-center rounded-md text-muted-foreground hover:text-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-primary/50 transition-opacity',
+                      isMinimalMode && !alwaysShowActions ? 'h-4 w-4' : 'h-6 w-6',
+                    )}
+                    aria-label={t('sessions.sidebar.session.actions.openInEditor')}
+                    onPointerDown={handleOpenInEditorPointerDown}
+                    onMouseDown={handleOpenInEditorMouseDown}
+                    onClick={handleOpenInEditorClick}
+                    onKeyDown={(event) => event.stopPropagation()}
+                  >
+                    <Icon name="external-link" className={cn(isMinimalMode && !alwaysShowActions ? 'h-2.5 w-2.5' : 'h-3.5 w-3.5')} />
+                  </button>
+                </TooltipTrigger>
+                <TooltipContent side="left" sideOffset={8}>
+                  {t('sessions.sidebar.session.actions.openInEditor')}
+                </TooltipContent>
+              </Tooltip>
+            ) : null}
             <DropdownMenu open={isMenuOpen} onOpenChange={handleMenuOpenChange}>
               <DropdownMenuTrigger asChild>
                 <button
diff --git a/packages/ui/src/lib/i18n/messages/en.ts b/packages/ui/src/lib/i18n/messages/en.ts
index db67aa71..5b08f74a 100644
--- a/packages/ui/src/lib/i18n/messages/en.ts
+++ b/packages/ui/src/lib/i18n/messages/en.ts
@@ -257,6 +257,7 @@ export const dict = {
   'sessions.sidebar.session.menu.exportMarkdown': 'Export Markdown',
   'sessions.sidebar.session.menu.runFusion': 'Run fusion',
   'sessions.sidebar.session.menu.openInSidePanel': 'Open in Side Panel',
+  'sessions.sidebar.session.actions.openInEditor': 'Open in Editor',
   'sessions.sidebar.session.menu.betaBadge': 'beta',
   'sessions.sidebar.session.menu.label': 'Session menu',
   'sessions.sidebar.session.untitled': 'Untitled Session',
diff --git a/packages/ui/src/lib/i18n/messages/es.ts b/packages/ui/src/lib/i18n/messages/es.ts
index 9ba61059..be3dd967 100644
--- a/packages/ui/src/lib/i18n/messages/es.ts
+++ b/packages/ui/src/lib/i18n/messages/es.ts
@@ -258,6 +258,7 @@ export const dict: Record<I18nKey, string> = {
   "sessions.sidebar.session.menu.exportMarkdown": "Exportar Markdown",
   "sessions.sidebar.session.menu.runFusion": "Ejecutar fusion",
   "sessions.sidebar.session.menu.openInSidePanel": "Abrir en panel lateral",
+  "sessions.sidebar.session.actions.openInEditor": "Abrir en el editor",
   "sessions.sidebar.session.menu.betaBadge": "beta",
   "sessions.sidebar.session.menu.label": "Menú de sesión",
   "sessions.sidebar.session.untitled": "Sesión sin título",
diff --git a/packages/ui/src/lib/i18n/messages/ko.ts b/packages/ui/src/lib/i18n/messages/ko.ts
index f53af199..ab1a9b87 100644
--- a/packages/ui/src/lib/i18n/messages/ko.ts
+++ b/packages/ui/src/lib/i18n/messages/ko.ts
@@ -258,6 +258,7 @@ export const dict: Record<I18nKey, string> = {
   'sessions.sidebar.session.menu.exportMarkdown': 'Markdown 내보내기',
   'sessions.sidebar.session.menu.runFusion': 'fusion 실행',
   'sessions.sidebar.session.menu.openInSidePanel': '사이드 패널에서 열기',
+  'sessions.sidebar.session.actions.openInEditor': '편집기에서 열기',
   'sessions.sidebar.session.menu.betaBadge': 'beta',
   'sessions.sidebar.session.menu.label': '세션 메뉴',
   'sessions.sidebar.session.untitled': '제목 없는 세션',
diff --git a/packages/ui/src/lib/i18n/messages/pl.ts b/packages/ui/src/lib/i18n/messages/pl.ts
index f2f55517..d3cef39b 100644
--- a/packages/ui/src/lib/i18n/messages/pl.ts
+++ b/packages/ui/src/lib/i18n/messages/pl.ts
@@ -89,6 +89,7 @@ export const dict: Record<I18nKey, string> = {
   'sessions.sidebar.session.menu.exportMarkdown': 'Eksportuj Markdown',
   'sessions.sidebar.session.menu.runFusion': 'Uruchom fusion',
   'sessions.sidebar.session.menu.openInSidePanel': 'Otwórz w panelu bocznym',
+  'sessions.sidebar.session.actions.openInEditor': 'Otwórz w edytorze',
   'sessions.sidebar.session.menu.betaBadge': 'beta',
   'sessions.sidebar.session.menu.label': 'Menu sesji',
   'sessions.sidebar.session.untitled': 'Nienazwana Sesja',
diff --git a/packages/ui/src/lib/i18n/messages/pt-BR.ts b/packages/ui/src/lib/i18n/messages/pt-BR.ts
index b2f1d977..3bcc5fc7 100644
--- a/packages/ui/src/lib/i18n/messages/pt-BR.ts
+++ b/packages/ui/src/lib/i18n/messages/pt-BR.ts
@@ -258,6 +258,7 @@ export const dict: Record<I18nKey, string> = {
   "sessions.sidebar.session.menu.exportMarkdown": "Exportar Markdown",
   "sessions.sidebar.session.menu.runFusion": "Executar fusion",
   "sessions.sidebar.session.menu.openInSidePanel": "Abrir no painel lateral",
+  "sessions.sidebar.session.actions.openInEditor": "Abrir no editor",
   "sessions.sidebar.session.menu.betaBadge": "beta",
   "sessions.sidebar.session.menu.label": "Menu da sessão",
   "sessions.sidebar.session.untitled": "Sessão sem título",
diff --git a/packages/ui/src/lib/i18n/messages/uk.ts b/packages/ui/src/lib/i18n/messages/uk.ts
index 070b6fad..a43bbeb9 100644
--- a/packages/ui/src/lib/i18n/messages/uk.ts
+++ b/packages/ui/src/lib/i18n/messages/uk.ts
@@ -258,6 +258,7 @@ export const dict: Record<I18nKey, string> = {
   "sessions.sidebar.session.menu.exportMarkdown": "Експорт Markdown",
   "sessions.sidebar.session.menu.runFusion": "Запустити fusion",
   "sessions.sidebar.session.menu.openInSidePanel": "Відкрити на бічній панелі",
+  "sessions.sidebar.session.actions.openInEditor": "Відкрити в редакторі",
   "sessions.sidebar.session.menu.betaBadge": "бета-версія",
   "sessions.sidebar.session.menu.label": "Меню сесії",
   "sessions.sidebar.session.untitled": "Сесія без назви",
diff --git a/packages/ui/src/lib/i18n/messages/zh-CN.ts b/packages/ui/src/lib/i18n/messages/zh-CN.ts
index 05be1577..f5c4759e 100644
--- a/packages/ui/src/lib/i18n/messages/zh-CN.ts
+++ b/packages/ui/src/lib/i18n/messages/zh-CN.ts
@@ -258,6 +258,7 @@ export const dict: Record<I18nKey, string> = {
   'sessions.sidebar.session.menu.exportMarkdown': '导出 Markdown',
   'sessions.sidebar.session.menu.runFusion': '运行 fusion',
   'sessions.sidebar.session.menu.openInSidePanel': '在侧边面板中打开',
+  'sessions.sidebar.session.actions.openInEditor': '在编辑器中打开',
   'sessions.sidebar.session.menu.betaBadge': 'beta',
   'sessions.sidebar.session.menu.label': '会话菜单',
   'sessions.sidebar.session.untitled': '未命名会话',
diff --git a/packages/vscode/src/ChatViewProvider.ts b/packages/vscode/src/ChatViewProvider.ts
index 5770d2f1..f112006f 100644
--- a/packages/vscode/src/ChatViewProvider.ts
+++ b/packages/vscode/src/ChatViewProvider.ts
@@ -199,6 +199,37 @@ export class ChatViewProvider implements vscode.WebviewViewProvider {
     }
   }
 
+  public addContextSelection(selection: { filePath: string; filename: string; text: string }) {
+    if (!this._view) {
+      return;
+    }
+
+    this._view.show(true);
+    this._view.webview.postMessage({
+      type: 'command',
+      command: 'addContextSelection',
+      payload: selection,
+    });
+  }
+
+  public addFileAttachments(files: Array<{ filePath: string; fileName: string; fileSize: number | null }>) {
+    if (!this._view) {
+      return;
+    }
+
+    const cleanedFiles = files.filter((entry) => entry.filePath.trim().length > 0 && entry.fileName.trim().length > 0);
+    if (cleanedFiles.length === 0) {
+      return;
+    }
+
+    this._view.show(true);
+    this._view.webview.postMessage({
+      type: 'command',
+      command: 'addFileAttachments',
+      payload: { files: cleanedFiles },
+    });
+  }
+
   public addFileMentions(paths: string[]) {
     if (!this._view) {
       return;
diff --git a/packages/vscode/src/SessionEditorPanelProvider.ts b/packages/vscode/src/SessionEditorPanelProvider.ts
index 476ffcac..7fe7de55 100644
--- a/packages/vscode/src/SessionEditorPanelProvider.ts
+++ b/packages/vscode/src/SessionEditorPanelProvider.ts
@@ -13,6 +13,26 @@ type SessionPanelState = {
   sseStreams: Map<string, AbortController>;
 };
 
+type ActiveEditorFilePayload = {
+  filePath: string;
+  fileName: string;
+  relativePath: string;
+  fileSize: number | null;
+  selection: { startLine: number; endLine: number; text: string } | null;
+};
+
+const isSameActiveEditorFilePayload = (a: ActiveEditorFilePayload | null, b: ActiveEditorFilePayload | null): boolean => {
+  if (a === b) return true;
+  if (!a || !b) return false;
+  return a.filePath === b.filePath
+    && a.fileName === b.fileName
+    && a.relativePath === b.relativePath
+    && a.fileSize === b.fileSize
+    && a.selection?.startLine === b.selection?.startLine
+    && a.selection?.endLine === b.selection?.endLine
+    && a.selection?.text === b.selection?.text;
+};
+
 export class SessionEditorPanelProvider {
   public static readonly viewType = 'openchamber.sessionEditor';
 
@@ -20,6 +40,10 @@ export class SessionEditorPanelProvider {
   private _cachedError?: string;
   private _sseCounter = 0;
   private _panels = new Map<string, SessionPanelState>();
+  private _lastActivePanelId: string | null = null;
+  private _broadcastSelectionDebounce: ReturnType<typeof setTimeout> | undefined;
+  private _clearActiveEditorFileTimer: ReturnType<typeof setTimeout> | undefined;
+  private _lastActiveEditorFilePayload: ActiveEditorFilePayload | null = null;
   private readonly _webviewDevServerUrl: string | null;
 
   constructor(
@@ -28,6 +52,11 @@ export class SessionEditorPanelProvider {
     private readonly _openCodeManager?: OpenCodeManager
   ) {
     this._webviewDevServerUrl = resolveWebviewDevServerUrl(this._context);
+
+    this._context.subscriptions.push(
+      vscode.window.onDidChangeActiveTextEditor(() => void this._broadcastActiveEditorFile()),
+      vscode.window.onDidChangeTextEditorSelection(() => this._scheduleBroadcast()),
+    );
   }
 
   public createOrShowNewSession(): void {
@@ -78,22 +107,40 @@ export class SessionEditorPanelProvider {
     };
 
     this._panels.set(panelId, state);
+    this._lastActivePanelId = panelId;
 
     panel.webview.html = this._getHtmlForWebview(panel.webview, initialSessionId);
 
     void this.updateTheme(vscode.window.activeColorTheme.kind);
     this._sendCachedStateToPanel(state);
+    void this._broadcastActiveEditorFile();
 
     panel.onDidDispose(() => {
       this._disposePanel(panelId);
     }, null, this._context.subscriptions);
 
+    panel.onDidChangeViewState((event) => {
+      if (event.webviewPanel.active) {
+        this._lastActivePanelId = panelId;
+      }
+    }, null, this._context.subscriptions);
+
     panel.webview.onDidReceiveMessage(async (message: BridgeRequest) => {
       if (message.type === 'restartApi') {
         await this._openCodeManager?.restart();
         return;
       }
 
+      if (message.type === 'vscode:command') {
+        const { command, args } = (message.payload || {}) as { command?: unknown; args?: unknown[] };
+        if (command === 'openchamber.updateSessionEditorTitle') {
+          const title = typeof args?.[1] === 'string' && args[1].trim().length > 0 ? args[1].trim() : 'Session';
+          state.panel.title = title;
+          state.panel.webview.postMessage({ id: message.id, type: message.type, success: true, data: { result: true } });
+          return;
+        }
+      }
+
       if (message.type === 'api:sse:start') {
         const response = await this._startSseProxy(message, state);
         state.panel.webview.postMessage(response);
@@ -159,6 +206,75 @@ export class SessionEditorPanelProvider {
     }
   }
 
+  private _getActivePanelEntry(): SessionPanelState | null {
+    const activeEntry = Array.from(this._panels.entries()).find(([, entry]) => entry.panel.active);
+    const panelId = activeEntry?.[0] ?? this._lastActivePanelId;
+    if (!panelId) {
+      return null;
+    }
+
+    return this._panels.get(panelId) ?? null;
+  }
+
+  public addContextSelectionToActivePanel(selection: { filePath: string; filename: string; text: string }): boolean {
+    if (!selection.filePath.trim() || !selection.filename.trim() || !selection.text.trim()) {
+      return false;
+    }
+
+    const entry = this._getActivePanelEntry();
+    if (!entry) {
+      return false;
+    }
+
+    entry.panel.reveal(entry.panel.viewColumn ?? vscode.ViewColumn.Active, true);
+    void entry.panel.webview.postMessage({
+      type: 'command',
+      command: 'addContextSelection',
+      payload: selection,
+    });
+    return true;
+  }
+
+  public createSessionWithPromptInActivePanel(prompt: string): boolean {
+    if (!prompt.trim()) {
+      return false;
+    }
+
+    const entry = this._getActivePanelEntry();
+    if (!entry) {
+      return false;
+    }
+
+    entry.panel.reveal(entry.panel.viewColumn ?? vscode.ViewColumn.Active, true);
+    void entry.panel.webview.postMessage({
+      type: 'command',
+      command: 'createSessionWithPrompt',
+      payload: { prompt },
+    });
+    return true;
+  }
+
+  public addFileAttachmentsToActivePanel(files: Array<{ filePath: string; fileName: string; fileSize: number | null }>): boolean {
+    const cleanedFiles = files.filter((entry) => entry.filePath.trim().length > 0 && entry.fileName.trim().length > 0);
+
+    if (cleanedFiles.length === 0) {
+      return false;
+    }
+
+    const entry = this._getActivePanelEntry();
+    if (!entry) {
+      return false;
+    }
+
+    entry.panel.reveal(entry.panel.viewColumn ?? vscode.ViewColumn.Active, true);
+    void entry.panel.webview.postMessage({
+      type: 'command',
+      command: 'addFileAttachments',
+      payload: { files: cleanedFiles },
+    });
+    return true;
+  }
+
   private _sendCachedStateToPanel(entry: SessionPanelState) {
     entry.panel.webview.postMessage({
       type: 'connectionStatus',
@@ -172,6 +288,93 @@ export class SessionEditorPanelProvider {
     });
   }
 
+  private _postCommandToPanels(command: string, payload: unknown): void {
+    for (const entry of this._panels.values()) {
+      entry.panel.webview.postMessage({
+        type: 'command',
+        command,
+        payload,
+      });
+    }
+  }
+
+  private _scheduleBroadcast(): void {
+    if (this._broadcastSelectionDebounce !== undefined) {
+      clearTimeout(this._broadcastSelectionDebounce);
+    }
+    this._broadcastSelectionDebounce = setTimeout(() => {
+      this._broadcastSelectionDebounce = undefined;
+      void this._broadcastActiveEditorFile();
+    }, 150);
+  }
+
+  private _scheduleClearActiveEditorFile(): void {
+    if (this._clearActiveEditorFileTimer !== undefined) {
+      clearTimeout(this._clearActiveEditorFileTimer);
+    }
+    this._clearActiveEditorFileTimer = setTimeout(() => {
+      this._clearActiveEditorFileTimer = undefined;
+      if (this._panels.size === 0 || this._lastActiveEditorFilePayload === null) {
+        return;
+      }
+      this._lastActiveEditorFilePayload = null;
+      this._postCommandToPanels('activeEditorFile', null);
+    }, 200);
+  }
+
+  private async _broadcastActiveEditorFile(): Promise<void> {
+    if (this._panels.size === 0) {
+      return;
+    }
+
+    const editor = vscode.window.activeTextEditor;
+    if (!editor || editor.document.uri.scheme !== 'file') {
+      this._scheduleClearActiveEditorFile();
+      return;
+    }
+
+    const editorUri = editor.document.uri;
+    const editorUriKey = editorUri.toString();
+
+    if (this._clearActiveEditorFileTimer !== undefined) {
+      clearTimeout(this._clearActiveEditorFileTimer);
+      this._clearActiveEditorFileTimer = undefined;
+    }
+
+    const filePath = normalizeWindowsDriveLetter(editorUri.fsPath);
+    const fileName = editorUri.fsPath.replace(/\\/g, '/').split('/').pop() || '';
+    const relativePath = vscode.workspace.asRelativePath(editorUri, false);
+
+    let fileSize: number | null = null;
+    try {
+      const stat = await vscode.workspace.fs.stat(editorUri);
+      fileSize = stat.size;
+    } catch {
+      // File may not be saved yet or inaccessible.
+    }
+
+    if (vscode.window.activeTextEditor?.document.uri.toString() !== editorUriKey) {
+      return;
+    }
+
+    let selection: ActiveEditorFilePayload['selection'] = null;
+    if (!editor.selection.isEmpty) {
+      selection = {
+        startLine: editor.selection.start.line + 1,
+        endLine: editor.selection.end.line + 1,
+        text: editor.document.getText(editor.selection),
+      };
+    }
+
+    const payload: ActiveEditorFilePayload = { filePath, fileName, relativePath, fileSize, selection };
+    if (isSameActiveEditorFilePayload(this._lastActiveEditorFilePayload, payload)) {
+      return;
+    }
+
+    this._lastActiveEditorFilePayload = payload;
+    this._postCommandToPanels('activeEditorFile', payload);
+  }
+
   private _disposePanel(sessionId: string) {
     const entry = this._panels.get(sessionId);
     if (!entry) return;
@@ -182,6 +385,9 @@ export class SessionEditorPanelProvider {
     entry.sseStreams.clear();
 
     this._panels.delete(sessionId);
+    if (this._lastActivePanelId === sessionId) {
+      this._lastActivePanelId = null;
+    }
   }
 
   private _buildSseHeaders(extra?: Record<string, string>): Record<string, string> {
diff --git a/packages/vscode/src/extension.ts b/packages/vscode/src/extension.ts
index bbae2aab..aa351e66 100644
--- a/packages/vscode/src/extension.ts
+++ b/packages/vscode/src/extension.ts
@@ -288,20 +288,24 @@ export async function activate(context: vscode.ExtensionContext) {
 
       // Get file info for context
       const filePath = vscode.workspace.asRelativePath(editor.document.uri);
-      const languageId = editor.document.languageId;
-      
       // Get line numbers (1-based for display)
       const startLine = selection.start.line + 1;
       const endLine = selection.end.line + 1;
       const lineRange = startLine === endLine ? `${startLine}` : `${startLine}-${endLine}`;
 
-      // Format as file path with line numbers, followed by markdown code block
-      const contextText = `${filePath}:${lineRange}\n\`\`\`${languageId}\n${selectedText}\n\`\`\``;
+      const filename = `${editor.document.fileName.split(/[\\/]/).pop() || filePath}:${lineRange}`;
+      const contextSelection = {
+        filePath: editor.document.uri.fsPath,
+        filename,
+        text: selectedText,
+      };
 
-      if (!(await revealChatViewForPayload())) {
-        return;
+      if (!sessionEditorProvider?.addContextSelectionToActivePanel(contextSelection)) {
+        if (!(await revealChatViewForPayload())) {
+          return;
+        }
+        chatViewProvider?.addContextSelection(contextSelection);
       }
-      chatViewProvider?.addTextToInput(contextText);
     })
   );
 
@@ -322,7 +326,7 @@ export async function activate(context: vscode.ExtensionContext) {
       }
 
       const uniqueUris = Array.from(new Map(uriCandidates.map((uri) => [uri.toString(), uri])).values());
-      const mentionPaths: string[] = [];
+      const attachedFiles: Array<{ filePath: string; fileName: string; fileSize: number | null }> = [];
       const skippedEntries: string[] = [];
 
       for (const uri of uniqueUris) {
@@ -342,23 +346,33 @@ export async function activate(context: vscode.ExtensionContext) {
           continue;
         }
 
-        const relativePath = vscode.workspace.asRelativePath(uri, false).replace(/\\/g, '/').trim();
-        if (!relativePath) {
+        const filePath = uri.fsPath.trim();
+        const fileName = uri.fsPath.replace(/\\/g, '/').split('/').pop() || vscode.workspace.asRelativePath(uri, false).replace(/\\/g, '/').trim();
+        if (!filePath || !fileName) {
           skippedEntries.push(uri.fsPath || uri.toString());
           continue;
         }
-        mentionPaths.push(relativePath);
+        let fileSize: number | null = null;
+        try {
+          const stat = await vscode.workspace.fs.stat(uri);
+          fileSize = stat.size;
+        } catch {
+          fileSize = null;
+        }
+        attachedFiles.push({ filePath, fileName, fileSize });
       }
 
-      if (mentionPaths.length === 0) {
+      if (attachedFiles.length === 0) {
         vscode.window.showWarningMessage('OpenChamber: No file selected to mention');
         return;
       }
 
-      if (!(await revealChatViewForPayload())) {
-        return;
+      if (!sessionEditorProvider?.addFileAttachmentsToActivePanel(attachedFiles)) {
+        if (!(await revealChatViewForPayload())) {
+          return;
+        }
+        chatViewProvider?.addFileAttachments(attachedFiles);
       }
-      chatViewProvider?.addFileMentions(mentionPaths);
 
       if (skippedEntries.length > 0) {
         vscode.window.showInformationMessage('OpenChamber: Some selected entries were skipped (folders or unsupported resources)');
@@ -392,10 +406,12 @@ export async function activate(context: vscode.ExtensionContext) {
         prompt = `Explain the following Code / Text:\n\n${filePath}`;
       }
 
-      if (!(await revealChatViewForPayload())) {
-        return;
+      if (!sessionEditorProvider?.createSessionWithPromptInActivePanel(prompt)) {
+        if (!(await revealChatViewForPayload())) {
+          return;
+        }
+        chatViewProvider?.createNewSessionWithPrompt(prompt);
       }
-      chatViewProvider?.createNewSessionWithPrompt(prompt);
     })
   );
 
@@ -423,10 +439,12 @@ export async function activate(context: vscode.ExtensionContext) {
 
       const prompt = `Improve the following Code:\n\n${filePath}:${lineRange}\n\`\`\`${languageId}\n${selectedText}\n\`\`\``;
 
-      if (!(await revealChatViewForPayload())) {
-        return;
+      if (!sessionEditorProvider?.createSessionWithPromptInActivePanel(prompt)) {
+        if (!(await revealChatViewForPayload())) {
+          return;
+        }
+        chatViewProvider?.createNewSessionWithPrompt(prompt);
       }
-      chatViewProvider?.createNewSessionWithPrompt(prompt);
     })
   );
 
diff --git a/packages/vscode/webview/main.tsx b/packages/vscode/webview/main.tsx
index b0ccd8f4..c87c7295 100644
--- a/packages/vscode/webview/main.tsx
+++ b/packages/vscode/webview/main.tsx
@@ -1159,12 +1159,21 @@ window.fetch = async (input: RequestInfo | URL, init?: RequestInit) => {
   return originalFetch(input as RequestInfo, init);
 };
 
-// Listen for addToContext command from extension
-onCommand('addToContext', (payload) => {
-  const { text } = payload as { text: string };
+onCommand('addContextSelection', (payload) => {
+  const { filePath, filename, text } = payload as { filePath?: unknown; filename?: unknown; text?: unknown };
+  if (typeof filePath !== 'string' || typeof filename !== 'string' || typeof text !== 'string') {
+    return;
+  }
+
+  const trimmedPath = filePath.trim();
+  const trimmedFilename = filename.trim();
+  if (!trimmedPath || !trimmedFilename || !text.trim()) {
+    return;
+  }
 
   import('@/sync/input-store').then(({ useInputStore }) => {
-    useInputStore.getState().setPendingInputText(text, 'append');
+    const file = new File([new Blob([text], { type: 'text/plain' })], trimmedFilename, { type: 'text/plain' });
+    void useInputStore.getState().addVSCodeSelectionAttachment(trimmedPath, file);
   });
 });
 
@@ -1188,6 +1197,33 @@ onCommand('addFileMentions', (payload) => {
   });
 });
 
+onCommand('addFileAttachments', (payload) => {
+  const rawFiles = Array.isArray((payload as { files?: unknown[] })?.files)
+    ? (payload as { files: unknown[] }).files
+    : [];
+
+  const files = rawFiles
+    .map((entry) => {
+      const record = entry as { filePath?: unknown; fileName?: unknown; fileSize?: unknown };
+      const filePath = typeof record.filePath === 'string' ? record.filePath.trim() : '';
+      const fileName = typeof record.fileName === 'string' ? record.fileName.trim() : '';
+      const fileSize = typeof record.fileSize === 'number' && Number.isFinite(record.fileSize) ? record.fileSize : null;
+      return filePath && fileName ? { filePath, fileName, fileSize } : null;
+    })
+    .filter((entry): entry is { filePath: string; fileName: string; fileSize: number | null } => entry !== null);
+
+  if (files.length === 0) {
+    return;
+  }
+
+  import('@/sync/input-store').then(({ useInputStore }) => {
+    const inputStore = useInputStore.getState();
+    for (const file of files) {
+      inputStore.addVSCodeFileAttachment(file.filePath, file.fileName, file.fileSize);
+    }
+  });
+});
+
 // Listen for createSessionWithPrompt command from extension (Explain, Improve Code)
 onCommand('createSessionWithPrompt', (payload) => {
   const { prompt } = payload as { prompt: string };
@@ -1200,13 +1236,14 @@ onCommand('createSessionWithPrompt', (payload) => {
     const sessionStore = useSessionUIStore.getState();
     const configStore = useConfigStore.getState();
 
-    // Open a new session draft first
-    sessionStore.openNewSessionDraft();
-
     // Get current provider/model/agent configuration
     const { currentProviderId, currentModelId, currentAgentName } = configStore;
 
     if (currentProviderId && currentModelId) {
+      if (!sessionStore.currentSessionId) {
+        sessionStore.openNewSessionDraft();
+      }
+
       // Send the message - this will create the session from the draft and send
       sessionStore.sendMessage(
         prompt,