fix(workspace): ensure default session on name collision and reject case-duplicate folder

src/web-ui/src/app/components/NewProjectDialog/NewProjectDialog.tsx

@@ -16,7 +16,8 @@ import { useTranslation } from 'react-i18next';
 import { createLogger } from '@/shared/utils/logger';
 import { Modal, Button, Input, Tooltip } from '@/component-library';
 import './NewProjectDialog.scss';
-import {workspaceAPI} from "@/infrastructure";
+import {workspaceAPI, systemAPI} from "@/infrastructure";
+import { isTauriCommandError } from '@/infrastructure/api/errors/TauriCommandError';
 import { notificationService } from '@/shared/notification-system';
 
 const log = createLogger('NewProjectDialog');
@@ -81,6 +82,25 @@ export const NewProjectDialog: React.FC<NewProjectDialogProps> = ({
       notificationService.warning(t('newProject.errorInvalidName'), { duration: 4500 });
       return;
     }
+    if (projectName.trim().length > 255) {
+      setError(t('newProject.errorNameTooLong'));
+      return;
+    }
+
+    // Pre-creation existence / case-collision check. On Windows/macOS the
+    // filesystem is case-insensitive, so "MyProject" and "myproject" resolve to
+    // the same folder; createDirectory is idempotent and would silently succeed
+    // without creating a new folder. Surface a clear error before attempting.
+    const trimmedName = projectName.trim();
+    const fullPath = `${parentPath.replace(/\\/g, '/')}/${trimmedName}`;
+    try {
+      if (await systemAPI.checkPathExists(fullPath)) {
+        setError(t('newProject.errorAlreadyExists'));
+        return;
+      }
+    } catch (error) {
+      log.error('Failed to check path existence', error);
+    }
 
     setIsCreating(true);
     setError('');
@@ -92,7 +112,14 @@ export const NewProjectDialog: React.FC<NewProjectDialogProps> = ({
       onClose();
     } catch (error) {
       log.error('Failed to create project', error);
-      const message = error instanceof Error && error.message ? error.message : t('newProject.errorCreateFailed');
+      let message: string;
+      if (isTauriCommandError(error) && error.isPermissionError()) {
+        message = t('newProject.errorParentNoAccess');
+      } else if (error instanceof Error && /does not exist|not a directory/i.test(error.message)) {
+        message = t('newProject.errorPathNotFound');
+      } else {
+        message = t('newProject.errorCreateFailed');
+      }
       setError(message);
       notificationService.error(message, { duration: 4500 });
     } finally {

src/web-ui/src/app/components/panels/review-platform/ReviewPlatformPanel.tsx

@@ -436,6 +436,9 @@ function reviewSessionLifecycle(session: Session): LinkedReviewSession['lifecycl
 }
 
 function getSessionTitle(session?: Session, fallback = 'Review session'): string {
+  if (session?.titleSource === 'i18n' && session.titleI18nKey) {
+    return i18nService.t(session.titleI18nKey, session.titleI18nParams ?? {}) || fallback;
+  }
   return session?.title?.trim() || fallback;
 }
 
@@ -1852,7 +1855,9 @@ export const ReviewPlatformPanel: React.FC<ReviewPlatformPanelProps> = ({
       workspacePath: linked.childSession.workspacePath,
       expand: true,
       sessionKind: linked.kind,
-      sessionTitle: linked.title,
+      sessionTitle: linked.childSession.titleSource === 'i18n' && linked.childSession.titleI18nKey
+        ? (i18nService.t(linked.childSession.titleI18nKey, linked.childSession.titleI18nParams ?? {}) || linked.title)
+        : linked.title,
       agentType: linked.childSession.config.agentType ?? (linked.kind === 'deep_review' ? 'DeepReview' : 'CodeReview'),
     });
   };

src/web-ui/src/flow_chat/components/ChatInput.tsx

@@ -9,6 +9,8 @@ import { useTranslation } from 'react-i18next';
 import { ArrowUp, BotMessageSquare, Image, RotateCcw, Plus, X, Sparkles, Loader2, ChevronRight, Files, MessageSquarePlus, Star } from 'lucide-react';
 import { ContextDropZone, useContextStore } from '../../shared/context-system';
 import { useActiveSessionState } from '@/flow_chat/hooks';
+import { i18nService } from '@/infrastructure/i18n';
+import { resolveSessionTitle } from '../utils/sessionTitle';
 import {
   RichTextInput,
   type InlineTriggerState,
@@ -476,7 +478,12 @@ export const ChatInput: React.FC<ChatInputProps> = ({
   const threadGoalController = useThreadGoalController(effectiveTargetSession, {
     isBtwSession,
   });
-  const currentSessionTitle = currentSession?.title?.trim() || t('session.untitled');
+  // Resolve via the i18n key (re-localizes on locale switch) instead of the
+  // persisted localized session.title string, so this tab stays in sync with
+  // the sidebar/header/toolbar instead of showing a stale old-locale name.
+  const currentSessionTitle = currentSession
+    ? resolveSessionTitle(currentSession, (key, options) => i18nService.t(key, options))
+    : t('session.untitled');
   const activeBtwSession = activeBtwSessionId
     ? flowChatState.sessions.get(activeBtwSessionId)
     : undefined;
@@ -492,10 +499,9 @@ export const ChatInput: React.FC<ChatInputProps> = ({
   const activeBtwTargetLabel = t(`childSession.kinds.${activeBtwKind}.short`, {
     defaultValue: t('chatInput.targetBtw'),
   });
+  const activeBtwFallbackKey = `childSession.kinds.${activeBtwKind}.title`;
   const activeBtwSessionTitle = activeBtwSession
-    ? activeBtwSession.title?.trim() || t(`childSession.kinds.${activeBtwKind}.title`, {
-        defaultValue: t('btw.threadLabel'),
-      })
+    ? resolveSessionTitle(activeBtwSession, (key, options) => i18nService.t(key, options), activeBtwFallbackKey) || t('btw.threadLabel')
     : '';
 
   const deferChatStripPassiveGitRefresh =

src/web-ui/src/flow_chat/components/btw/BtwSessionPanel.tsx

@@ -1,5 +1,6 @@
 import React, {useCallback, useEffect, useMemo, useRef, useState} from 'react';
 import {useTranslation} from 'react-i18next';
+import { i18nService } from '@/infrastructure/i18n';
 import path from 'path-browserify';
 import {CornerUpLeft, Link2, Square, Sparkles} from 'lucide-react';
 import {FlowChatContext} from '../modern/FlowChatContext';
@@ -83,8 +84,12 @@ const PANEL_CONFIG: FlowChatConfig = {
   theme: 'dark',
 };
 
-const resolveSessionTitle = (session?: Session | null, fallback = 'Side thread') =>
-  session?.title?.trim() || fallback;
+const resolveSessionTitle = (session?: Session | null, fallback = 'Side thread') => {
+  if (session?.titleSource === 'i18n' && session.titleI18nKey) {
+    return i18nService.t(session.titleI18nKey, session.titleI18nParams ?? {}) || fallback;
+  }
+  return session?.title?.trim() || fallback;
+};
 const log = createLogger('BtwSessionPanel');
 const REVIEW_ACTION_BOTTOM_BLANK_SPACE_PX = 96;
 const EMPTY_ACTION_ID_SET = new Set<string>();

src/web-ui/src/flow_chat/components/modern/ExportImageButton.tsx

@@ -182,7 +182,12 @@ export const ExportImageButton: React.FC<ExportImageButtonProps> = ({
 
     for (const [, session] of state.sessions) {
       const turn = session.dialogTurns.find((t: DialogTurn) => t.id === turnId);
-      if (turn) return { turn, sessionTitle: session.title?.trim() || '' };
+      if (turn) {
+        const sessionTitle = session.titleSource === 'i18n' && session.titleI18nKey
+          ? (i18nService.t(session.titleI18nKey, session.titleI18nParams ?? {}) || '')
+          : (session.title?.trim() || '');
+        return { turn, sessionTitle };
+      }
     }
     return null;
   }, [turnId]);

src/web-ui/src/flow_chat/services/FlowChatManager.ts

@@ -255,10 +255,12 @@ export class FlowChatManager {
           nextCursor = nextPage.nextCursor;
         }
       }
-      const hasHistoricalSessions =
-        workspaceSessions.length > 0 ||
-        initialMetadataPage.totalTopLevelCount > 0 ||
-        initialMetadataPage.sessions.length > 0;
+      // Count only sessions that belong to THIS workspace (already path-filtered
+      // above). Counting all sessions in the storage dir (totalTopLevelCount /
+      // initialMetadataPage.sessions.length) incorrectly reports "has history"
+      // when another workspace shares the slug-collided sessions/ dir, which
+      // suppresses default-session creation for a newly opened workspace.
+      const hasHistoricalSessions = workspaceSessions.length > 0;
       const isCurrentInitializationRequest = () =>
         this.latestInitializationRequestKey === requestKey;
       const activeSession = state.activeSessionId

src/web-ui/src/flow_chat/services/flow-chat-manager/MessageModule.ts

@@ -8,6 +8,7 @@ import { ACPClientAPI } from '@/infrastructure/api/service-api/ACPClientAPI';
 import { configManager } from '@/infrastructure/config/services/ConfigManager';
 import type { AIModelConfig, AgentModelDefaultsConfig, DefaultModelsConfig } from '@/infrastructure/config/types';
 import { notificationService } from '../../../shared/notification-system';
+import { i18nService } from '@/infrastructure/i18n';
 import { stateMachineManager } from '../../state-machine';
 import { SessionExecutionEvent, SessionExecutionState } from '../../state-machine/types';
 import { generateTempTitle } from '../../utils/titleUtils';
@@ -358,30 +359,36 @@ export async function sendMessage(
 
   } catch (error) {
     log.error('Failed to send message', { sessionId: sessionId, error });
-
-    const errorMessage = error instanceof Error ? error.message : 'Failed to send message';
-
+
+    // Map the "workspace folder deleted/moved" backend error to a localized
+    // message; other errors pass through verbatim for diagnostics. The
+    // "Thinking process error" notification title was also hardcoded English.
+    const rawErrorMessage = error instanceof Error ? error.message : '';
+    const errorMessage = /does not resolve to a local workspace/i.test(rawErrorMessage)
+      ? i18nService.t('flow-chat:errors.workspaceNotResolvable')
+      : (rawErrorMessage || i18nService.t('flow-chat:errors.sendFailed'));
+
     const currentState = stateMachineManager.getCurrentState(sessionId);
     if (currentState === SessionExecutionState.PROCESSING) {
       await stateMachineManager.transition(sessionId, SessionExecutionEvent.ERROR_OCCURRED, {
         error: errorMessage
       });
       await stateMachineManager.transition(sessionId, SessionExecutionEvent.RESET);
     }
-    
+
     const state = context.flowChatStore.getState();
     const currentSession = state.sessions.get(sessionId);
     if (createdLocalTurnId && currentSession && !options?.preserveTurnOnStartError) {
       context.flowChatStore.deleteDialogTurn(sessionId, createdLocalTurnId);
     }
-    
+
     if (!options?.preserveTurnOnStartError) {
       notificationService.error(errorMessage, {
-        title: 'Thinking process error',
+        title: i18nService.t('flow-chat:errors.thinkingProcessError'),
         duration: 5000
       });
     }
-    
+
     throw error;
   }
 }

src/web-ui/src/flow_chat/services/flow-chat-manager/SessionModule.ts

@@ -18,7 +18,7 @@ import { WorkspaceKind, type WorkspaceInfo } from '@/shared/types';
 import type { AIModelConfig, AgentModelDefaultsConfig, DefaultModelsConfig } from '@/infrastructure/config/types';
 import type { FlowChatContext, SessionConfig } from './types';
 import type { Session } from '../../types/flow-chat';
-import { touchSessionActivity, cleanupSaveState } from './PersistenceModule';
+import { touchSessionActivity, cleanupSaveState, updateSessionMetadata } from './PersistenceModule';
 import { cleanupSessionBuffers } from './TextChunkModule';
 import {
   createTextSessionTitleDescriptor,
@@ -643,6 +643,12 @@ export async function createChatSession(
         titleDescriptor,
       );
 
+      // Persist the title metadata (incl. the i18n title key/params) at creation
+      // so an empty session can re-localize its default name on a later reload +
+      // locale switch. createSession only stored the localized sessionName string;
+      // without this, empty sessions have no title key on disk and can't re-localize.
+      await updateSessionMetadata(context, response.sessionId);
+
       return response.sessionId;
     });
 

src/web-ui/src/infrastructure/api/errors/TauriCommandError.ts

@@ -58,10 +58,12 @@ export class TauriCommandError extends Error {
 
   public isPermissionError(): boolean {
     const message = this.message.toLowerCase();
-    return message.includes('permission') || 
-           message.includes('access') || 
+    return message.includes('permission') ||
+           message.includes('permitted') ||
+           message.includes('access') ||
            message.includes('unauthorized') ||
-           message.includes('forbidden');
+           message.includes('forbidden') ||
+           message.includes('eperm');
   }
 
 

src/web-ui/src/infrastructure/services/business/workspaceManager.ts

@@ -14,6 +14,7 @@ import { createLogger } from '@/shared/utils/logger';
 import { startupTrace } from '@/shared/utils/startupTrace';
 import { elapsedMs, nowMs } from '@/shared/utils/timing';
 import { listen } from '@tauri-apps/api/event';
+import { i18nService } from '@/infrastructure/i18n';
 
 const log = createLogger('WorkspaceManager');
 
@@ -625,7 +626,12 @@ class WorkspaceManager {
       return workspace;
     } catch (error) {
       log.error('Failed to open workspace', { path, error });
-      const errorMessage = error instanceof Error ? error.message : String(error);
+      const rawMessage = error instanceof Error ? error.message : String(error);
+      // Map the common "folder moved/deleted" backend error to a localized
+      // message; other errors pass through verbatim (callers log the raw error).
+      const errorMessage = /does not exist|not a directory/i.test(rawMessage)
+        ? i18nService.t('common:newProject.errorPathNotFound')
+        : rawMessage;
       this.updateState({ loading: false, error: errorMessage }, { type: 'workspace:error', error: errorMessage });
       throw error;
     }

src/web-ui/src/locales/en-US/common.json

@@ -637,7 +637,11 @@
     "errorSelectParent": "Please select a parent directory",
     "errorEnterName": "Please enter a project name",
     "errorCreateFailed": "Failed to create project",
-    "errorInvalidName": "Project name cannot contain these characters: / \\ : * ? \" < > |"
+    "errorInvalidName": "Project name cannot contain these characters: / \\ : * ? \" < > |",
+    "errorAlreadyExists": "A workspace with this name already exists at the selected location",
+    "errorParentNoAccess": "No access permission for the selected parent directory",
+    "errorNameTooLong": "Project name is too long (max 255 characters)",
+    "errorPathNotFound": "The workspace folder does not exist or has been moved"
   },
   "peerDirectoryPicker": {
     "loading": "Loading remote directories…",

src/web-ui/src/locales/en-US/flow-chat.json

@@ -2356,7 +2356,9 @@
     }
   },
   "errors": {
-    "sendFailed": "Failed to send message"
+    "sendFailed": "Failed to send message",
+    "thinkingProcessError": "Thinking process error",
+    "workspaceNotResolvable": "The workspace folder does not exist or has been moved"
   },
   "actions": {
     "send": "Send"

src/web-ui/src/locales/zh-CN/common.json

@@ -637,7 +637,11 @@
     "errorSelectParent": "请选择父目录",
     "errorEnterName": "请输入工作区名称",
     "errorCreateFailed": "创建工作区失败",
-    "errorInvalidName": "工作区名称不能包含以下字符：/ \\ : * ? \" < > |"
+    "errorInvalidName": "工作区名称不能包含以下字符：/ \\ : * ? \" < > |",
+    "errorAlreadyExists": "所选位置已存在同名工作区",
+    "errorParentNoAccess": "没有所选父目录的访问权限",
+    "errorNameTooLong": "工作区名称过长（最多 255 个字符）",
+    "errorPathNotFound": "工作区文件夹不存在或已被移动"
   },
   "peerDirectoryPicker": {
     "loading": "正在加载远程目录…",

src/web-ui/src/locales/zh-CN/flow-chat.json

@@ -2356,7 +2356,9 @@
     }
   },
   "errors": {
-    "sendFailed": "发送消息失败"
+    "sendFailed": "发送消息失败",
+    "thinkingProcessError": "思考过程错误",
+    "workspaceNotResolvable": "工作区文件夹不存在或已被移动"
   },
   "actions": {
     "send": "发送"

src/web-ui/src/locales/zh-TW/common.json

@@ -637,7 +637,11 @@
     "errorSelectParent": "請選擇父目錄",
     "errorEnterName": "請輸入工作區名稱",
     "errorCreateFailed": "建立工作區失敗",
-    "errorInvalidName": "工作區名稱不能包含以下字符：/ \\ : * ? \" < > |"
+    "errorInvalidName": "工作區名稱不能包含以下字符：/ \\ : * ? \" < > |",
+    "errorAlreadyExists": "所選位置已存在同名工作區",
+    "errorParentNoAccess": "沒有所選父目錄的存取權限",
+    "errorNameTooLong": "工作區名稱過長（最多 255 個字元）",
+    "errorPathNotFound": "工作區資料夾不存在或已被移動"
   },
   "peerDirectoryPicker": {
     "loading": "正在載入遠端目錄…",

src/web-ui/src/locales/zh-TW/flow-chat.json

@@ -2356,7 +2356,9 @@
     }
   },
   "errors": {
-    "sendFailed": "傳送訊息失敗"
+    "sendFailed": "傳送訊息失敗",
+    "thinkingProcessError": "思考過程錯誤",
+    "workspaceNotResolvable": "工作區資料夾不存在或已被移動"
   },
   "actions": {
     "send": "傳送"