refactor(surface): drop the deprecated main-tab aliases and dead diagram surface

MainTab/activeMainTab/setActiveMainTab/setMainTabGuard were deprecated
mirrors of the surface names — every call site now uses
activeSurface/setActiveSurface/setSurfaceGuard directly and the aliases
are gone, including the persisted mirror field.

The 'diagram' surface had no way to open it (navigateToDiagram had no
callers except a .drawio attachment click that navigated to a surface
nothing rendered); the surface, DiagramView, and its store plumbing are
removed, and a .drawio attachment now opens in the file panel.

?tab= deep links map to the matching context-panel surface instead of
setting a main-area surface nothing renders, and a persisted non-chat
surface can no longer rehydrate into a blank main area.

packages/ui/src/components/views/ArchiveView.tsx

@@ -28,7 +28,7 @@ export function ArchiveView(): React.ReactNode {
   const { t } = useI18n();
   const open = useUIStore((state) => state.isArchivePageOpen);
   const setOpen = useUIStore((state) => state.setArchivePageOpen);
-  const setActiveMainTab = useUIStore((state) => state.setActiveMainTab);
+  const setActiveSurface = useUIStore((state) => state.setActiveSurface);
   const setCurrentSession = useSessionUIStore((state) => state.setCurrentSession);
   const unarchiveSession = useSessionUIStore((state) => state.unarchiveSession);
   const homeDirectory = useDirectoryStore((state) => state.homeDirectory);
@@ -86,9 +86,9 @@ export function ArchiveView(): React.ReactNode {
   const openSession = React.useCallback((session: Session) => {
     const directory = normalizePath(resolveGlobalSessionDirectory(session));
     setCurrentSession(session.id, directory ?? undefined);
-    setActiveMainTab('chat');
+    setActiveSurface('chat');
     setOpen(false);
-  }, [setActiveMainTab, setCurrentSession, setOpen]);
+  }, [setActiveSurface, setCurrentSession, setOpen]);
 
   const restoreSession = React.useCallback((session: Session) => {
     void unarchiveSession(session.id).then((success) => {

packages/ui/src/components/views/DiagramView.tsx

@@ -1,102 +0,0 @@
-import React from 'react';
-import { useUIStore } from '@/stores/useUIStore';
-import { useRuntimeAPIs } from '@/hooks/useRuntimeAPIs';
-import { useI18n } from '@/lib/i18n';
-import { DiagramEditor, type DiagramEditorHandle } from '@/components/diagram';
-import { Icon } from '@/components/icon/Icon';
-
-export function DiagramView() {
-  const { t } = useI18n();
-  const { files } = useRuntimeAPIs();
-
-  const [filePath, setFilePath] = React.useState<string | null>(null);
-  const [xml, setXml] = React.useState('');
-  const [loading, setLoading] = React.useState(true);
-  const editorRef = React.useRef<DiagramEditorHandle>(null);
-  const pendingDiagramFile = useUIStore((state) => state.pendingDiagramFile);
-
-  const loadFile = React.useCallback(async (path: string) => {
-    setLoading(true);
-    setFilePath(path);
-    try {
-      const result = await files?.readFile?.(path);
-      if (result) {
-        setXml(result.content);
-      }
-    } catch {
-      setXml('');
-    } finally {
-      setLoading(false);
-    }
-  }, [files]);
-
-  React.useEffect(() => {
-    if (!pendingDiagramFile) {
-      return;
-    }
-    const pending = useUIStore.getState().consumePendingDiagramFile();
-    if (pending) {
-      void loadFile(pending);
-    }
-  }, [loadFile, pendingDiagramFile]);
-
-  const saveDiagram = React.useCallback(async () => {
-    const newXml = editorRef.current?.getXml();
-    if (filePath && files?.writeFile && newXml && newXml !== xml) {
-      await files.writeFile(filePath, newXml);
-      setXml(newXml);
-    }
-  }, [filePath, files, xml]);
-
-  const fileName = filePath ? filePath.split('/').pop() || filePath : '';
-
-  if (!filePath) {
-    return (
-      <div className="flex h-full items-center justify-center p-3">
-        <div className="typography-ui text-muted-foreground">
-          {t('filesView.editor.pickFileFromTree')}
-        </div>
-      </div>
-    );
-  }
-
-  if (loading) {
-    return (
-      <div className="flex h-full items-center justify-center p-3">
-        <Icon name="loader-4" className="size-4 animate-spin" />
-      </div>
-    );
-  }
-
-  return (
-    <div className="flex h-full flex-col">
-      <div className="flex items-center gap-2 border-b border-border/30 px-3 py-1.5">
-        <Icon name="file" className="size-4 shrink-0 text-muted-foreground" />
-        <span className="typography-ui text-muted-foreground truncate flex-1">{fileName}</span>
-        <button
-          type="button"
-          onClick={() => void saveDiagram()}
-          className="size-6 flex items-center justify-center rounded-md text-foreground hover:bg-interactive-hover/50 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-primary"
-          title={t('filesView.diagram.saveDiagram')}
-        >
-          <Icon name="save-3" className="size-4" />
-        </button>
-        <button
-          type="button"
-          onClick={() => useUIStore.getState().setActiveMainTab('chat')}
-          className="size-6 flex items-center justify-center rounded-md text-muted-foreground hover:bg-interactive-hover/50 hover:text-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-primary"
-          title={t('filesView.diagram.closeDiagramView')}
-        >
-          <Icon name="close" className="size-4" />
-        </button>
-      </div>
-      <div className="flex-1 min-h-0">
-        <DiagramEditor
-          ref={editorRef}
-          xml={xml}
-          className="h-full"
-        />
-      </div>
-    </div>
-  );
-}

packages/ui/src/components/views/FilesView.tsx

@@ -939,7 +939,7 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
 
   const [confirmDiscardOpen, setConfirmDiscardOpen] = React.useState(false);
   const pendingSelectFileRef = React.useRef<FileNode | null>(null);
-  const pendingTabRef = React.useRef<import('@/stores/useUIStore').MainTab | null>(null);
+  const pendingTabRef = React.useRef<import('@/stores/useUIStore').WorkspaceSurface | null>(null);
   const pendingClosePathRef = React.useRef<string | null>(null);
   const skipDirtyOnceRef = React.useRef(false);
   const copiedContentTimeoutRef = React.useRef<number | null>(null);
@@ -1029,7 +1029,7 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
   const [isDragging, setIsDragging] = React.useState(false);
 
   // Session/config for sending comments
-  const setMainTabGuard = useUIStore((state) => state.setMainTabGuard);
+  const setSurfaceGuard = useUIStore((state) => state.setSurfaceGuard);
   const pendingFileNavigation = useUIStore((state) => state.pendingFileNavigation);
   const setPendingFileNavigation = useUIStore((state) => state.setPendingFileNavigation);
   const pendingFileFocusPath = useUIStore((state) => state.pendingFileFocusPath);
@@ -1098,10 +1098,10 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
   React.useEffect(() => {
     setLineSelection(null);
     reset();
-    setMainTabGuard(null);
+    setSurfaceGuard(null);
     setDraftContent('');
     setIsSaving(false);
-  }, [selectedFile?.path, reset, setMainTabGuard]);
+  }, [selectedFile?.path, reset, setSurfaceGuard]);
 
   React.useEffect(() => {
     setCommentSelection(lineSelection);
@@ -1713,11 +1713,11 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
 
   React.useEffect(() => {
     if (!isDirty) {
-      setMainTabGuard(null);
+      setSurfaceGuard(null);
       return;
     }
 
-    const guard = (_nextTab: import('@/stores/useUIStore').MainTab) => {
+    const guard = (_nextTab: import('@/stores/useUIStore').WorkspaceSurface) => {
       if (skipDirtyOnceRef.current) {
         skipDirtyOnceRef.current = false;
         return true;
@@ -1727,15 +1727,15 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
       return false;
     };
 
-    setMainTabGuard(guard);
+    setSurfaceGuard(guard);
 
     return () => {
-      const currentGuard = useUIStore.getState().mainTabGuard;
+      const currentGuard = useUIStore.getState().surfaceGuard;
       if (currentGuard === guard) {
-        setMainTabGuard(null);
+        setSurfaceGuard(null);
       }
     };
-  }, [isDirty, setMainTabGuard]);
+  }, [isDirty, setSurfaceGuard]);
 
   React.useEffect(() => {
     if (autoSaveEnabled) {
@@ -2180,10 +2180,10 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
     }
 
     if (nextTab) {
-      setMainTabGuard(null);
-      useUIStore.getState().setActiveMainTab(nextTab);
+      setSurfaceGuard(null);
+      useUIStore.getState().setActiveSurface(nextTab);
     }
-  }, [displayedContent, handleSelectFile, isMobile, removeOpenPath, root, selectedFile?.path, setMainTabGuard, setSelectedPath]);
+  }, [displayedContent, handleSelectFile, isMobile, removeOpenPath, root, selectedFile?.path, setSurfaceGuard, setSelectedPath]);
 
   const saveAndContinue = React.useCallback(async () => {
     const nextFile = pendingSelectFileRef.current;
@@ -2234,10 +2234,10 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
     }
 
     if (nextTab) {
-      setMainTabGuard(null);
-      useUIStore.getState().setActiveMainTab(nextTab);
+      setSurfaceGuard(null);
+      useUIStore.getState().setActiveSurface(nextTab);
     }
-  }, [handleSelectFile, isMobile, removeOpenPath, root, saveDraft, selectedFile?.path, setMainTabGuard, setSelectedPath]);
+  }, [handleSelectFile, isMobile, removeOpenPath, root, saveDraft, selectedFile?.path, setSurfaceGuard, setSelectedPath]);
 
   const handleCloseFile = React.useCallback((path: string) => {
     const isActive = selectedFile?.path === path;

packages/ui/src/components/views/PlanView.tsx

@@ -168,7 +168,7 @@ export const PlanView: React.FC<PlanViewProps> = ({ targetPath = null, projectPl
   const activeProjectId = useProjectsStore((state) => state.activeProjectId);
   const gitDirectories = useGitStore((state) => state.directories);
   const effectiveDirectory = useEffectiveDirectory() ?? '';
-  const setActiveMainTab = useUIStore((state) => state.setActiveMainTab);
+  const setActiveSurface = useUIStore((state) => state.setActiveSurface);
   const setSessionSwitcherOpen = useUIStore((state) => state.setSessionSwitcherOpen);
   const runtimeApis = useRuntimeAPIs();
   const { isMobile } = useDeviceInfo();
@@ -579,10 +579,10 @@ export const PlanView: React.FC<PlanViewProps> = ({ targetPath = null, projectPl
   }, []);
 
   const routeToChat = React.useCallback(() => {
-    setActiveMainTab('chat');
+    setActiveSurface('chat');
     setSessionSwitcherOpen(false);
     onNavigatedToChat?.();
-  }, [onNavigatedToChat, setActiveMainTab, setSessionSwitcherOpen]);
+  }, [onNavigatedToChat, setActiveSurface, setSessionSwitcherOpen]);
 
   const handleConfirmPlanSend = React.useCallback(
     async (execution: TodoSendExecution) => {

packages/ui/src/components/views/git/ConflictDialog.tsx

@@ -41,7 +41,7 @@ export const ConflictDialog: React.FC<ConflictDialogProps> = ({
   const currentSessionId = useSessionUIStore((state) => state.currentSessionId);
   const setPendingInputText = useInputStore((state) => state.setPendingInputText);
   const setPendingSyntheticParts = useInputStore((state) => state.setPendingSyntheticParts);
-  const setActiveMainTab = useUIStore((state) => state.setActiveMainTab);
+  const setActiveSurface = useUIStore((state) => state.setActiveSurface);
 
   const [isLoading, setIsLoading] = React.useState(false);
   const [conflictDetails, setConflictDetails] = React.useState<MergeConflictDetails | null>(null);
@@ -137,7 +137,7 @@ export const ConflictDialog: React.FC<ConflictDialogProps> = ({
       { text: context.payloadText, synthetic: true },
     ]);
 
-    setActiveMainTab('chat');
+    setActiveSurface('chat');
     onClearState?.();
     onOpenChange(false);
   };
@@ -159,7 +159,7 @@ export const ConflictDialog: React.FC<ConflictDialogProps> = ({
       ],
     });
     // Navigate to chat tab so user sees the new session
-    setActiveMainTab('chat');
+    setActiveSurface('chat');
     onClearState?.();
     onOpenChange(false);
   };

packages/ui/src/components/views/git/IntegrateCommitsSection.tsx

@@ -65,7 +65,7 @@ export const IntegrateCommitsSection: React.FC<{
 }) => {
   const { t } = useI18n();
   const currentSessionId = useSessionUIStore((s) => s.currentSessionId);
-  const setActiveMainTab = useUIStore((s) => s.setActiveMainTab);
+  const setActiveSurface = useUIStore((s) => s.setActiveSurface);
   const [branchDropdownOpen, setBranchDropdownOpen] = React.useState(false);
   const [branchSearch, setBranchSearch] = React.useState('');
   const searchInputRef = React.useRef<HTMLInputElement>(null);
@@ -236,7 +236,7 @@ export const IntegrateCommitsSection: React.FC<{
         ],
       });
       // Navigate to chat tab so user sees the new session
-      setActiveMainTab('chat');
+      setActiveSurface('chat');
       return;
     }
 
@@ -251,8 +251,8 @@ export const IntegrateCommitsSection: React.FC<{
       { text: context.instructionsText, synthetic: true },
       { text: context.payloadText, synthetic: true },
     ]);
-    setActiveMainTab('chat');
-  }, [currentSessionId, setActiveMainTab, buildConflictContext, openNewSessionDraft, setPendingInputText, setPendingSyntheticParts, t]);
+    setActiveSurface('chat');
+  }, [currentSessionId, setActiveSurface, buildConflictContext, openNewSessionDraft, setPendingInputText, setPendingSyntheticParts, t]);
 
   const handleMove = React.useCallback(async () => {
     if (ui.kind !== 'ready') return;

packages/ui/src/components/views/git/PullRequestSection.tsx

@@ -327,7 +327,7 @@ export const PullRequestSection: React.FC<{
   const githubAuthChecked = useGitHubAuthStore((state) => state.hasChecked);
   const setSettingsDialogOpen = useUIStore((state) => state.setSettingsDialogOpen);
   const setSettingsPage = useUIStore((state) => state.setSettingsPage);
-  const setActiveMainTab = useUIStore((state) => state.setActiveMainTab);
+  const setActiveSurface = useUIStore((state) => state.setActiveSurface);
   const currentSessionId = useSessionUIStore((state) => state.currentSessionId);
   const newSessionDraftOpen = useSessionUIStore((state) => Boolean(state.newSessionDraft?.open));
   const { isMobile, hasTouchInput, screenWidth } = useDeviceInfo();
@@ -986,14 +986,14 @@ export const PullRequestSection: React.FC<{
           text: '',
         });
       }
-      setActiveMainTab('chat');
+      setActiveSurface('chat');
     } catch (e) {
       const message = e instanceof Error ? e.message : String(e);
       toast.error(t('gitView.pr.toast.loadChecksFailed'), { description: message });
     } finally {
       setIsAttachingChecks(false);
     }
-  }, [directory, ensurePrContext, github, pr, resolveDraftTarget, setActiveMainTab, status?.repo, t]);
+  }, [directory, ensurePrContext, github, pr, resolveDraftTarget, setActiveSurface, status?.repo, t]);
 
   const sendCommentsToChat = React.useCallback(async () => {
     if (!github?.prContext) {
@@ -1021,14 +1021,14 @@ export const PullRequestSection: React.FC<{
       for (const comment of timelineComments) {
         attachCommentDraft(target, comment);
       }
-      setActiveMainTab('chat');
+      setActiveSurface('chat');
     } catch (e) {
       const message = e instanceof Error ? e.message : String(e);
       toast.error(t('gitView.pr.toast.loadPrCommentsFailed'), { description: message });
     } finally {
       setIsAttachingComments(false);
     }
-  }, [attachCommentDraft, directory, ensurePrContext, github, pr, resolveDraftTarget, setActiveMainTab, status?.repo, t, timelineComments]);
+  }, [attachCommentDraft, directory, ensurePrContext, github, pr, resolveDraftTarget, setActiveSurface, status?.repo, t, timelineComments]);
 
   const sendSingleCommentToChat = React.useCallback(async (comment: TimelineCommentItem) => {
     const target = resolveDraftTarget();
@@ -1037,8 +1037,8 @@ export const PullRequestSection: React.FC<{
     }
 
     attachCommentDraft(target, comment);
-    setActiveMainTab('chat');
-  }, [attachCommentDraft, resolveDraftTarget, setActiveMainTab]);
+    setActiveSurface('chat');
+  }, [attachCommentDraft, resolveDraftTarget, setActiveSurface]);
 
   const refresh = React.useCallback(async (options?: { force?: boolean; onlyExistingPr?: boolean; silent?: boolean; markInitialResolved?: boolean }) => {
     await refreshPrStatus(prStatusKey, options);