diff --git a/electron/preload.ts b/electron/preload.ts
index 68e7d19..63dc8b7 100644
--- a/electron/preload.ts
+++ b/electron/preload.ts
@@ -29,6 +29,8 @@ import {
   AssistantFile,
   ListAssistantFilesFilter,
   UploadAssistantFileParams,
+  ChatStreamChunk,
+  ChatMessage,
 } from './types'
 
 console.log('Preload script is running!')
@@ -387,6 +389,31 @@ contextBridge.exposeInMainWorld('electronAPI', {
         }
       },
     },
+    // Chat streaming operations
+    chatStream: {
+      start: async (
+        profileId: string,
+        assistantName: string,
+        params: { messages: ChatMessage[]; model?: string; filter?: Record<string, unknown> }
+      ): Promise<string> => {
+        const result = await ipcRenderer.invoke('assistant:chat:stream:start', profileId, assistantName, params)
+        if (!result.success) {
+          throw new Error(result.error)
+        }
+        return result.data.streamId
+      },
+      cancel: async (streamId: string): Promise<void> => {
+        const result = await ipcRenderer.invoke('assistant:chat:stream:cancel', streamId)
+        if (!result.success) {
+          throw new Error(result.error)
+        }
+      },
+      onChunk: (callback: (streamId: string, chunk: ChatStreamChunk) => void): (() => void) => {
+        const handler = (_event: Electron.IpcRendererEvent, streamId: string, chunk: ChatStreamChunk) => callback(streamId, chunk)
+        ipcRenderer.on('assistant:chat:chunk', handler)
+        return () => ipcRenderer.removeListener('assistant:chat:chunk', handler)
+      },
+    },
   },
   window: {
     createConnection: async (profile: ConnectionProfile): Promise<{ windowId: string }> => {
@@ -469,6 +496,14 @@ contextBridge.exposeInMainWorld('electronAPI', {
       }
     },
   },
+  dialog: {
+    showOpenDialog: async (options: {
+      properties?: Array<'openFile' | 'openDirectory' | 'multiSelections'>
+      filters?: Array<{ name: string; extensions: string[] }>
+    }): Promise<{ canceled: boolean; filePaths: string[] }> => {
+      return await ipcRenderer.invoke('dialog:showOpenDialog', options)
+    },
+  },
   updater: {
     checkForUpdates: async (): Promise<any> => {
       const result = await ipcRenderer.invoke('updater:check')
diff --git a/electron/types.ts b/electron/types.ts
index 801a26d..82879c7 100644
--- a/electron/types.ts
+++ b/electron/types.ts
@@ -486,3 +486,88 @@ export interface UploadAssistantFileParams {
   multimodal?: boolean
 }
 
+// ============================================================================
+// Assistant Chat Types
+// ============================================================================
+
+/**
+ * Chat message structure
+ */
+export interface ChatMessage {
+  role: 'user' | 'assistant'
+  content: string
+}
+
+/**
+ * A single reference within a citation
+ */
+export interface CitationReference {
+  file: {
+    name: string
+    id: string
+    status?: string
+    signedUrl?: string | null
+  }
+  pages?: number[]
+}
+
+/**
+ * Citation reference in assistant responses
+ */
+export interface Citation {
+  position: number
+  references: CitationReference[]
+}
+
+/**
+ * Token usage statistics for chat
+ */
+export interface ChatUsage {
+  promptTokens: number
+  completionTokens: number
+  totalTokens: number
+}
+
+/**
+ * Context options for chat requests
+ */
+export interface ChatContextOptions {
+  topK?: number
+  snippetSize?: number
+}
+
+/**
+ * Parameters for chat requests
+ */
+export interface ChatParams {
+  messages: ChatMessage[]
+  model?: string
+  filter?: Record<string, unknown>
+  jsonResponse?: boolean
+  includeHighlights?: boolean
+  temperature?: number
+  contextOptions?: ChatContextOptions
+}
+
+/**
+ * Response from non-streaming chat
+ */
+export interface ChatResponse {
+  id: string
+  message: ChatMessage
+  citations?: Citation[]
+  usage?: ChatUsage
+  finishReason?: string
+  model?: string
+}
+
+/**
+ * Stream chunk types for streaming chat responses
+ */
+export type ChatStreamChunk =
+  | { type: 'message_start'; id: string; model: string; role: 'assistant' }
+  | { type: 'content'; content: string }
+  | { type: 'citation'; citation: Citation | undefined }
+  | { type: 'message_end'; usage?: ChatUsage; finishReason?: string }
+  | { type: 'error'; error: string }
+
diff --git a/src/components/mode/ModeSwitcher.tsx b/src/components/mode/ModeSwitcher.tsx
index ae1ebe0..647211b 100644
--- a/src/components/mode/ModeSwitcher.tsx
+++ b/src/components/mode/ModeSwitcher.tsx
@@ -9,7 +9,7 @@ interface ModeOption {
 }
 
 const modes: ModeOption[] = [
-  { value: 'index', icon: Database, label: 'Index Explorer', shortcut: '⌘1' },
+  { value: 'index', icon: Database, label: 'Database Explorer', shortcut: '⌘1' },
   { value: 'assistant', icon: Bot, label: 'Assistant Explorer', shortcut: '⌘2' },
 ]
 
@@ -43,7 +43,7 @@ export function ModeSwitcher() {
             data-testid={`mode-${value}`}
           >
             <Icon className="h-3.5 w-3.5" />
-            <span className="hidden sm:inline">{value === 'index' ? 'Index' : 'Assistant'}</span>
+            <span className="hidden sm:inline">{value === 'index' ? 'Database' : 'Assistant'}</span>
           </button>
         )
       })}
diff --git a/src/types/electron.d.ts b/src/types/electron.d.ts
index 8c1628d..1400d82 100644
--- a/src/types/electron.d.ts
+++ b/src/types/electron.d.ts
@@ -87,6 +87,40 @@ declare global {
     metadata?: Record<string, string | number>
   }
 
+  // Chat types for assistant streaming
+  interface ChatMessage {
+    role: 'user' | 'assistant'
+    content: string
+  }
+
+  interface CitationReference {
+    file: {
+      name: string
+      id: string
+      status?: string
+      signedUrl?: string | null
+    }
+    pages?: number[]
+  }
+
+  interface Citation {
+    position: number
+    references: CitationReference[]
+  }
+
+  interface ChatUsage {
+    promptTokens: number
+    completionTokens: number
+    totalTokens: number
+  }
+
+  type ChatStreamChunk =
+    | { type: 'message_start'; id: string; model: string; role: 'assistant' }
+    | { type: 'content'; content: string }
+    | { type: 'citation'; citation: Citation | undefined }
+    | { type: 'message_end'; usage?: ChatUsage; finishReason?: string }
+    | { type: 'error'; error: string }
+
   interface ConnectionProfile {
     id: string
     name: string
@@ -377,6 +411,15 @@ declare global {
         upload: (profileId: string, assistantName: string, params: UploadAssistantFileParams) => Promise<AssistantFile>
         delete: (profileId: string, assistantName: string, fileId: string) => Promise<void>
       }
+      chatStream: {
+        start: (profileId: string, assistantName: string, params: {
+          messages: Array<{ role: 'user' | 'assistant'; content: string }>;
+          model?: string;
+          filter?: Record<string, unknown>;
+        }) => Promise<string>
+        cancel: (streamId: string) => Promise<void>
+        onChunk: (callback: (streamId: string, chunk: ChatStreamChunk) => void) => () => void
+      }
     }
     window: {
       createConnection: (profile: ConnectionProfile) => Promise<{ windowId: string }>
@@ -396,6 +439,12 @@ declare global {
     shell: {
       openExternal: (url: string) => Promise<void>
     }
+    dialog: {
+      showOpenDialog: (options: {
+        properties?: Array<'openFile' | 'openDirectory' | 'multiSelections'>
+        filters?: Array<{ name: string; extensions: string[] }>
+      }) => Promise<{ canceled: boolean; filePaths: string[] }>
+    }
     updater: {
       checkForUpdates: () => Promise<UpdateInfo | undefined>
       downloadUpdate: () => Promise<void>