feat: support inserting current date into assistant prompt

extensions/assistant-extension/src/index.ts

@@ -75,7 +75,7 @@ export default class JanAssistantExtension extends AssistantExtension {
       'Jan is a helpful desktop assistant that can reason through complex tasks and use tools to complete them on the user’s behalf.',
     model: '*',
     instructions:
-      'You are a helpful AI assistant. Your primary goal is to assist users with their questions and tasks to the best of your abilities.\n\nWhen responding:\n- Answer directly from your knowledge when you can\n- Be concise, clear, and helpful\n- Admit when you’re unsure rather than making things up\n\nIf tools are available to you:\n- Only use tools when they add real value to your response\n- Use tools when the user explicitly asks (e.g., "search for...", "calculate...", "run this code")\n- Use tools for information you don’t know or that needs verification\n- Never use tools just because they’re available\n\nWhen using tools:\n- Use one tool at a time and wait for results\n- Use actual values as arguments, not variable names\n- Learn from each result before deciding next steps\n- Avoid repeating the same tool call with identical parameters\n\nRemember: Most questions can be answered without tools. Think first whether you need them.',
+      'You are a helpful AI assistant. Your primary goal is to assist users with their questions and tasks to the best of your abilities.\n\nWhen responding:\n- Answer directly from your knowledge when you can\n- Be concise, clear, and helpful\n- Admit when you’re unsure rather than making things up\n\nIf tools are available to you:\n- Only use tools when they add real value to your response\n- Use tools when the user explicitly asks (e.g., "search for...", "calculate...", "run this code")\n- Use tools for information you don’t know or that needs verification\n- Never use tools just because they’re available\n\nWhen using tools:\n- Use one tool at a time and wait for results\n- Use actual values as arguments, not variable names\n- Learn from each result before deciding next steps\n- Avoid repeating the same tool call with identical parameters\n\nRemember: Most questions can be answered without tools. Think first whether you need them.\n\nCurrent date: {{current_date}}',
     tools: [
       {
         type: 'retrieval',

web-app/src/containers/dialogs/AddEditAssistant.tsx

@@ -321,6 +321,9 @@ export default function AddEditAssistant({
               className="resize-none"
               rows={4}
             />
+            <div className="text-xs text-main-view-fg/60">
+              {t('assistants:instructionsDateHint')}
+            </div>
           </div>
 
           <div className="space-y-2 my-4">

web-app/src/hooks/__tests__/useChat.instructions.test.ts

@@ -0,0 +1,138 @@
+import { renderHook, act } from '@testing-library/react'
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { useChat } from '../useChat'
+
+// Use hoisted storage for our mock to avoid hoist errors
+const hoisted = vi.hoisted(() => ({
+  builderMock: vi.fn(() => ({
+    addUserMessage: vi.fn(),
+    addAssistantMessage: vi.fn(),
+    getMessages: vi.fn(() => []),
+  })),
+}))
+
+vi.mock('@/lib/messages', () => ({
+  CompletionMessagesBuilder: hoisted.builderMock,
+}))
+
+// Mock dependencies similar to existing tests, but customize assistant
+vi.mock('../../hooks/usePrompt', () => ({
+  usePrompt: vi.fn(() => ({ prompt: 'test prompt', setPrompt: vi.fn() })),
+}))
+
+vi.mock('../../hooks/useAppState', () => ({
+  useAppState: Object.assign(
+    vi.fn(() => ({
+      tools: [],
+      updateTokenSpeed: vi.fn(),
+      resetTokenSpeed: vi.fn(),
+      updateTools: vi.fn(),
+      updateStreamingContent: vi.fn(),
+      updateLoadingModel: vi.fn(),
+      setAbortController: vi.fn(),
+    })),
+    { getState: vi.fn(() => ({ tokenSpeed: { tokensPerSecond: 10 } })) }
+  ),
+}))
+
+vi.mock('../../hooks/useAssistant', () => ({
+  useAssistant: vi.fn(() => ({
+    assistants: [
+      {
+        id: 'test-assistant',
+        instructions: 'Today is {{current_date}}',
+        parameters: { stream: true },
+      },
+    ],
+    currentAssistant: {
+      id: 'test-assistant',
+      instructions: 'Today is {{current_date}}',
+      parameters: { stream: true },
+    },
+  })),
+}))
+
+vi.mock('../../hooks/useModelProvider', () => ({
+  useModelProvider: vi.fn(() => ({
+    getProviderByName: vi.fn(() => ({ provider: 'openai', models: [] })),
+    selectedModel: { id: 'test-model', capabilities: ['tools'] },
+    selectedProvider: 'openai',
+    updateProvider: vi.fn(),
+  })),
+}))
+
+vi.mock('../../hooks/useThreads', () => ({
+  useThreads: vi.fn(() => ({
+    getCurrentThread: vi.fn(() => ({ id: 'test-thread', model: { id: 'test-model', provider: 'openai' } })),
+    createThread: vi.fn(() => Promise.resolve({ id: 'test-thread', model: { id: 'test-model', provider: 'openai' } })),
+    updateThreadTimestamp: vi.fn(),
+  })),
+}))
+
+vi.mock('../../hooks/useMessages', () => ({
+  useMessages: vi.fn(() => ({ getMessages: vi.fn(() => []), addMessage: vi.fn() })),
+}))
+
+vi.mock('../../hooks/useToolApproval', () => ({
+  useToolApproval: vi.fn(() => ({ approvedTools: [], showApprovalModal: vi.fn(), allowAllMCPPermissions: false })),
+}))
+
+vi.mock('../../hooks/useModelContextApproval', () => ({
+  useContextSizeApproval: vi.fn(() => ({ showApprovalModal: vi.fn() })),
+}))
+
+vi.mock('../../hooks/useModelLoad', () => ({
+  useModelLoad: vi.fn(() => ({ setModelLoadError: vi.fn() })),
+}))
+
+vi.mock('@tanstack/react-router', () => ({
+  useRouter: vi.fn(() => ({ navigate: vi.fn() })),
+}))
+
+vi.mock('@/lib/completion', () => ({
+  emptyThreadContent: { thread_id: 'test-thread', content: '' },
+  extractToolCall: vi.fn(),
+  newUserThreadContent: vi.fn(() => ({ thread_id: 'test-thread', content: 'user message' })),
+  newAssistantThreadContent: vi.fn(() => ({ thread_id: 'test-thread', content: 'assistant message' })),
+  sendCompletion: vi.fn(() => Promise.resolve({ choices: [{ message: { content: '' } }] })),
+  postMessageProcessing: vi.fn(),
+  isCompletionResponse: vi.fn(() => true),
+}))
+
+vi.mock('@/services/mcp', () => ({ getTools: vi.fn(() => Promise.resolve([])) }))
+
+vi.mock('@/services/models', () => ({
+  startModel: vi.fn(() => Promise.resolve()),
+  stopModel: vi.fn(() => Promise.resolve()),
+  stopAllModels: vi.fn(() => Promise.resolve()),
+}))
+
+vi.mock('@/services/providers', () => ({ updateSettings: vi.fn(() => Promise.resolve()) }))
+
+vi.mock('@tauri-apps/api/event', () => ({ listen: vi.fn(() => Promise.resolve(vi.fn())) }))
+
+describe('useChat instruction rendering', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('renders assistant instructions by replacing {{current_date}} with today', async () => {
+    vi.useFakeTimers()
+    vi.setSystemTime(new Date('2025-08-16T00:00:00Z'))
+
+    const { result } = renderHook(() => useChat())
+
+    await act(async () => {
+      await result.current.sendMessage('Hello')
+    })
+
+    expect(hoisted.builderMock).toHaveBeenCalled()
+    const calls = (hoisted.builderMock as any).mock.calls as any[]
+    const call = calls[0]
+    expect(call[0]).toEqual([])
+    expect(call[1]).toMatch(/^Today is /)
+    expect(call[1]).not.toContain('{{current_date}}')
+
+    vi.useRealTimers()
+  })
+})

web-app/src/hooks/useAssistant.ts

@@ -43,7 +43,7 @@ export const defaultAssistant: Assistant = {
   description:
     'Jan is a helpful desktop assistant that can reason through complex tasks and use tools to complete them on the user’s behalf.',
   instructions:
-    'You are a helpful AI assistant. Your primary goal is to assist users with their questions and tasks to the best of your abilities.\n\nWhen responding:\n- Answer directly from your knowledge when you can\n- Be concise, clear, and helpful\n- Admit when you’re unsure rather than making things up\n\nIf tools are available to you:\n- Only use tools when they add real value to your response\n- Use tools when the user explicitly asks (e.g., "search for...", "calculate...", "run this code")\n- Use tools for information you don’t know or that needs verification\n- Never use tools just because they’re available\n\nWhen using tools:\n- Use one tool at a time and wait for results\n- Use actual values as arguments, not variable names\n- Learn from each result before deciding next steps\n- Avoid repeating the same tool call with identical parameters\n\nRemember: Most questions can be answered without tools. Think first whether you need them.',
+    'You are a helpful AI assistant. Your primary goal is to assist users with their questions and tasks to the best of your abilities.\n\nWhen responding:\n- Answer directly from your knowledge when you can\n- Be concise, clear, and helpful\n- Admit when you’re unsure rather than making things up\n\nIf tools are available to you:\n- Only use tools when they add real value to your response\n- Use tools when the user explicitly asks (e.g., "search for...", "calculate...", "run this code")\n- Use tools for information you don’t know or that needs verification\n- Never use tools just because they’re available\n\nWhen using tools:\n- Use one tool at a time and wait for results\n- Use actual values as arguments, not variable names\n- Learn from each result before deciding next steps\n- Avoid repeating the same tool call with identical parameters\n\nRemember: Most questions can be answered without tools. Think first whether you need them.\n\nCurrent date: {{current_date}}',
 }
 
 export const useAssistant = create<AssistantState>()((set, get) => ({

web-app/src/hooks/useChat.ts

@@ -17,6 +17,7 @@ import {
   sendCompletion,
 } from '@/lib/completion'
 import { CompletionMessagesBuilder } from '@/lib/messages'
+import { renderInstructions } from '@/lib/instructionTemplate'
 import { ChatCompletionMessageToolCall } from 'openai/resources'
 import { useAssistant } from './useAssistant'
 
@@ -229,7 +230,7 @@ export const useChat = () => {
 
         const builder = new CompletionMessagesBuilder(
           messages,
-          currentAssistant?.instructions
+          renderInstructions(currentAssistant?.instructions)
         )
         if (troubleshooting) builder.addUserMessage(message)
 

web-app/src/lib/__tests__/instructionTemplate.test.ts

@@ -0,0 +1,27 @@
+import { describe, it, expect, vi } from 'vitest'
+import { renderInstructions } from '../instructionTemplate'
+
+describe('renderInstructions', () => {
+  it('replaces {{current_date}} with today when no params provided', () => {
+    vi.useFakeTimers()
+    vi.setSystemTime(new Date('2025-08-16T00:00:00Z'))
+
+    const input = 'Today is {{current_date}}.'
+    const out = renderInstructions(input)
+
+    expect(out).not.toBe(input)
+    expect(out).toMatch(/^Today is /)
+    expect(out).not.toContain('{{current_date}}')
+
+    vi.useRealTimers()
+  })
+
+  it('replaces multiple occurrences of {{current_date}}', () => {
+    const input = 'A {{current_date}} B {{current_date}} C'
+    const out = renderInstructions(input)
+    expect(out).not.toContain('{{current_date}}')
+    expect(out.startsWith('A ')).toBe(true)
+    expect(out.includes(' B ')).toBe(true)
+    expect(out.endsWith(' C')).toBe(true)
+  })
+})

web-app/src/lib/instructionTemplate.ts

@@ -0,0 +1,23 @@
+import { formatDate } from '@/utils/formatDate'
+
+/**
+ * Render assistant instructions by replacing supported placeholders.
+ * Supported placeholders:
+ * - {{current_date}}: Inserts today’s date (UTC, long month), e.g., August 16, 2025.
+ */
+export function renderInstructions(instructions: string): string
+export function renderInstructions(
+  instructions?: string
+): string | undefined
+export function renderInstructions(
+  instructions?: string
+): string | undefined {
+  if (!instructions) return instructions
+
+  const currentDateStr = formatDate(new Date(), { includeTime: false })
+
+  // Replace current_date (allow spaces inside braces).
+  let rendered = instructions
+  rendered = rendered.replace(/\{\{\s*current_date\s*\}\}/gi, currentDateStr)
+  return rendered
+}

web-app/src/locales/de-DE/assistants.json

@@ -29,5 +29,6 @@
   "save": "Speichern",
   "createNew": "Neuen Assistenten anlegen",
   "personality": "Persönlichkeit",
-  "capabilities": "Fähigkeiten"
+  "capabilities": "Fähigkeiten",
+  "instructionsDateHint": "Tipp: Verwenden Sie {{current_date}}, um das heutige Datum einzufügen."
 }

web-app/src/locales/en/assistants.json

@@ -29,5 +29,6 @@
   "save": "Save",
   "createNew": "Create New Assistant",
   "personality": "Personality",
-  "capabilities": "Capabilities"
+  "capabilities": "Capabilities",
+  "instructionsDateHint": "Tip: Use {{current_date}} to insert today’s date."
 }

web-app/src/locales/id/assistants.json

@@ -29,5 +29,6 @@
   "save": "Simpan",
   "createNew": "Buat Asisten Baru",
   "personality": "Kepribadian",
-  "capabilities": "Kemampuan"
+  "capabilities": "Kemampuan",
+  "instructionsDateHint": "Tips: Gunakan {{current_date}} untuk menyisipkan tanggal hari ini."
 }

web-app/src/locales/vn/assistants.json

@@ -29,5 +29,6 @@
   "save": "Lưu",
   "createNew": "Tạo Trợ lý Mới",
   "personality": "Tính cách",
-  "capabilities": "Khả năng"
+  "capabilities": "Khả năng",
+  "instructionsDateHint": "Mẹo: Dùng {{current_date}} để chèn ngày hôm nay."
 }

web-app/src/locales/zh-CN/assistants.json

@@ -29,5 +29,6 @@
   "save": "保存",
   "createNew": "创建新助手",
   "personality": "个性",
-  "capabilities": "能力"
+  "capabilities": "能力",
+  "instructionsDateHint": "提示：使用 {{current_date}} 插入今天的日期。"
 }

web-app/src/locales/zh-TW/assistants.json

@@ -29,5 +29,6 @@
   "save": "儲存",
   "createNew": "建立新助理",
   "personality": "個性",
-  "capabilities": "能力"
+  "capabilities": "能力",
+  "instructionsDateHint": "提示：使用 {{current_date}} 插入今天的日期。"
 }

web-app/src/utils/__tests__/formatDate.test.ts

@@ -38,7 +38,7 @@ describe('formatDate', () => {
       '2023-12-01T12:00:00Z'
     ]
 
-    const formatted = dates.map(formatDate)
+    const formatted = dates.map((d) => formatDate(d))
 
     expect(formatted[0]).toMatch(/Jan.*1.*2023/i)
     expect(formatted[1]).toMatch(/Feb.*1.*2023/i)
@@ -81,4 +81,23 @@ describe('formatDate', () => {
     // Should include abbreviated month name
     expect(formatted).toMatch(/Jul/i)
   })
+
+  it('supports date-only formatting when includeTime=false', () => {
+    const date = '2023-07-04T12:00:00Z'
+    const formatted = formatDate(date, { includeTime: false })
+
+    // Long month, no time
+    expect(formatted).toMatch(/July.*4.*2023/i)
+    expect(formatted).not.toMatch(/\d{1,2}:\d{2}/i)
+    expect(formatted).not.toMatch(/(AM|PM)/i)
+  })
+
+  it('date-only formatting includes a year and omits time across edge cases', () => {
+    const oldDate = '1900-01-01T00:00:00Z'
+    const formatted = formatDate(oldDate, { includeTime: false })
+
+    expect(formatted).toMatch(/\d{4}/)
+    expect(formatted).not.toMatch(/\d{1,2}:\d{2}/i)
+    expect(formatted).not.toMatch(/(AM|PM)/i)
+  })
 })

web-app/src/utils/formatDate.ts

@@ -1,10 +1,34 @@
-export const formatDate = (date: string | number | Date): string => {
-  return new Date(date).toLocaleString('en-US', {
+type FormatDateOptions = {
+  includeTime?: boolean
+}
+
+export const formatDate = (
+  date: string | number | Date,
+  options?: FormatDateOptions
+): string => {
+  const includeTime = options?.includeTime ?? true
+
+  // Base options shared across both modes
+  const base: Intl.DateTimeFormatOptions = {
     year: 'numeric',
-    month: 'short',
     day: 'numeric',
-    hour: 'numeric',
-    minute: 'numeric',
-    hour12: true,
+  }
+
+  if (includeTime) {
+    // Time mode: short month + time, fixed UTC for stable output in tests
+    return new Date(date).toLocaleString('en-US', {
+      ...base,
+      month: 'short',
+      hour: 'numeric',
+      minute: 'numeric',
+      hour12: true,
+      timeZone: 'UTC',
+    })
+  }
+
+  // Date-only mode: long month, no timezone adjustment
+  return new Date(date).toLocaleDateString('en-US', {
+    ...base,
+    month: 'long',
   })
 }