diff --git a/web/src/chat/presentation.test.ts b/web/src/chat/presentation.test.ts
index ecf47134..6918fde4 100644
--- a/web/src/chat/presentation.test.ts
+++ b/web/src/chat/presentation.test.ts
@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest'
-import { getEventPresentation, formatResetTime } from './presentation'
+import { getEventPresentation, formatMessageTimestamp, formatResetTime } from './presentation'
 
 describe('getEventPresentation — limit-warning', () => {
     it('formats five_hour warning', () => {
@@ -139,3 +139,18 @@ describe('formatResetTime', () => {
         expect(result).toBeTruthy()
     })
 })
+
+describe('formatMessageTimestamp', () => {
+    it('formats today without requiring a date prefix', () => {
+        const now = new Date(2026, 4, 22, 14, 30)
+        const result = formatMessageTimestamp(new Date(2026, 4, 22, 9, 5), now)
+        expect(result).toBeTruthy()
+        expect(result).not.toContain('2026')
+    })
+
+    it('includes a year for messages outside the current year', () => {
+        const now = new Date(2026, 4, 22, 14, 30)
+        const result = formatMessageTimestamp(new Date(2025, 11, 31, 23, 59), now)
+        expect(result).toContain('2025')
+    })
+})
diff --git a/web/src/chat/presentation.ts b/web/src/chat/presentation.ts
index 6058c82d..676c6bcc 100644
--- a/web/src/chat/presentation.ts
+++ b/web/src/chat/presentation.ts
@@ -26,6 +26,34 @@ export function formatResetTime(value: number): string {
     return date.toLocaleString(undefined, { month: 'short', day: 'numeric', hour: 'numeric', minute: '2-digit' })
 }
 
+export function formatMessageTimestamp(date: Date, now: Date = new Date()): string {
+    const sameDay = date.getFullYear() === now.getFullYear()
+        && date.getMonth() === now.getMonth()
+        && date.getDate() === now.getDate()
+
+    if (sameDay) {
+        return date.toLocaleTimeString(undefined, { hour: 'numeric', minute: '2-digit' })
+    }
+
+    const sameYear = date.getFullYear() === now.getFullYear()
+    if (sameYear) {
+        return date.toLocaleString(undefined, { month: 'short', day: 'numeric', hour: 'numeric', minute: '2-digit' })
+    }
+
+    return date.toLocaleString(undefined, { year: 'numeric', month: 'short', day: 'numeric', hour: 'numeric', minute: '2-digit' })
+}
+
+export function formatMessageTimestampTitle(date: Date): string {
+    return date.toLocaleString(undefined, {
+        year: 'numeric',
+        month: 'short',
+        day: 'numeric',
+        hour: 'numeric',
+        minute: '2-digit',
+        second: '2-digit'
+    })
+}
+
 // Known types: five_hour → "5-hour", seven_day → "7-day".
 // Unknown types use underscore-to-space fallback (e.g. thirty_day → "thirty day").
 function formatLimitType(limitType: string | undefined): string {
diff --git a/web/src/components/AssistantChat/messages/AssistantMessage.tsx b/web/src/components/AssistantChat/messages/AssistantMessage.tsx
index ce922111..b04bc998 100644
--- a/web/src/components/AssistantChat/messages/AssistantMessage.tsx
+++ b/web/src/components/AssistantChat/messages/AssistantMessage.tsx
@@ -12,6 +12,7 @@ import { getConversationMessageAnchorId } from '@/chat/outline'
 import { MessageMetadata } from '@/components/AssistantChat/messages/MessageMetadata'
 import { isNestedInteractiveEvent } from '@/components/AssistantChat/messages/metadataToggle'
 import { CodexReviewCard } from '@/components/AssistantChat/messages/CodexReviewCard'
+import { MessageTimestamp } from '@/components/AssistantChat/messages/MessageTimestamp'
 
 const TOOL_COMPONENTS = {
     Fallback: HappyToolMessage
@@ -85,16 +86,19 @@ export function HappyAssistantMessage() {
                 className="scroll-mt-4 px-1 min-w-0 max-w-full overflow-x-hidden"
             >
                 <CliOutputBlock text={cliText} />
-                {hasMetadata && (
-                    <button
-                        type="button"
-                        onClick={() => setShowMetadata((open) => !open)}
-                        aria-expanded={showMetadata}
-                        className="mt-1 text-[10px] text-[var(--app-hint)] underline-offset-2 hover:text-[var(--app-fg)] hover:underline"
-                    >
-                        {showMetadata ? 'Hide metadata' : 'Show metadata'}
-                    </button>
-                )}
+                <div className="mt-1 flex items-center gap-2">
+                    <MessageTimestamp className="text-[10px] leading-none text-[var(--app-hint)]" />
+                    {hasMetadata && (
+                        <button
+                            type="button"
+                            onClick={() => setShowMetadata((open) => !open)}
+                            aria-expanded={showMetadata}
+                            className="text-[10px] text-[var(--app-hint)] underline-offset-2 hover:text-[var(--app-fg)] hover:underline"
+                        >
+                            {showMetadata ? 'Hide metadata' : 'Show metadata'}
+                        </button>
+                    )}
+                </div>
                 {showMetadata && (
                     <MessageMetadata
                         invokedAt={invokedAt}
@@ -125,6 +129,9 @@ export function HappyAssistantMessage() {
                         aria-expanded={hasMetadata ? showMetadata : undefined}
                     >
                         <CodexReviewCard review={codexReview} />
+                        <div className="mt-1 flex justify-start">
+                            <MessageTimestamp className="text-[10px] leading-none text-[var(--app-hint)]" />
+                        </div>
                         {showMetadata && (
                             <MessageMetadata
                                 invokedAt={invokedAt}
@@ -169,6 +176,9 @@ export function HappyAssistantMessage() {
                     aria-expanded={hasMetadata ? showMetadata : undefined}
                 >
                     <MessagePrimitive.Content components={MESSAGE_PART_COMPONENTS} />
+                    <div className="mt-1 flex justify-start">
+                        <MessageTimestamp className="text-[10px] leading-none text-[var(--app-hint)]" />
+                    </div>
                     {showMetadata && (
                         <MessageMetadata
                             invokedAt={invokedAt}
@@ -199,6 +209,9 @@ export function HappyAssistantMessage() {
                     aria-expanded={hasMetadata ? showMetadata : undefined}
                 >
                     <MessagePrimitive.Content components={MESSAGE_PART_COMPONENTS} />
+                    <div className="mt-1 flex justify-start">
+                        <MessageTimestamp className="text-[10px] leading-none text-[var(--app-hint)]" />
+                    </div>
                     {showMetadata && (
                         <MessageMetadata
                             invokedAt={invokedAt}
diff --git a/web/src/components/AssistantChat/messages/MessageTimestamp.tsx b/web/src/components/AssistantChat/messages/MessageTimestamp.tsx
new file mode 100644
index 00000000..650bd51e
--- /dev/null
+++ b/web/src/components/AssistantChat/messages/MessageTimestamp.tsx
@@ -0,0 +1,20 @@
+import { useAssistantState } from '@assistant-ui/react'
+import { formatMessageTimestamp, formatMessageTimestampTitle } from '@/chat/presentation'
+
+type MessageTimestampProps = {
+    className?: string
+}
+
+export function MessageTimestamp(props: MessageTimestampProps) {
+    const createdAt = useAssistantState(({ message }) => message.createdAt)
+
+    return (
+        <time
+            dateTime={createdAt.toISOString()}
+            title={formatMessageTimestampTitle(createdAt)}
+            className={props.className}
+        >
+            {formatMessageTimestamp(createdAt)}
+        </time>
+    )
+}
diff --git a/web/src/components/AssistantChat/messages/SystemMessage.tsx b/web/src/components/AssistantChat/messages/SystemMessage.tsx
index f5ec95c6..ed058095 100644
--- a/web/src/components/AssistantChat/messages/SystemMessage.tsx
+++ b/web/src/components/AssistantChat/messages/SystemMessage.tsx
@@ -2,6 +2,7 @@ import { MessagePrimitive, useAssistantState } from '@assistant-ui/react'
 import { getEventPresentation } from '@/chat/presentation'
 import type { HappyChatMessageMetadata } from '@/lib/assistant-runtime'
 import { getConversationMessageAnchorId } from '@/chat/outline'
+import { MessageTimestamp } from '@/components/AssistantChat/messages/MessageTimestamp'
 
 export function HappySystemMessage() {
     const role = useAssistantState(({ message }) => message.role)
@@ -25,6 +26,7 @@ export function HappySystemMessage() {
                 <span className="inline-flex items-center gap-1">
                     {icon ? <span aria-hidden="true">{icon}</span> : null}
                     <span>{text}</span>
+                    <MessageTimestamp className="text-[10px]" />
                 </span>
             </div>
         </MessagePrimitive.Root>
diff --git a/web/src/components/AssistantChat/messages/UserMessage.tsx b/web/src/components/AssistantChat/messages/UserMessage.tsx
index 3b458b78..605370cf 100644
--- a/web/src/components/AssistantChat/messages/UserMessage.tsx
+++ b/web/src/components/AssistantChat/messages/UserMessage.tsx
@@ -11,6 +11,7 @@ import { useCopyToClipboard } from '@/hooks/useCopyToClipboard'
 import { getConversationMessageAnchorId } from '@/chat/outline'
 import { MessageMetadata } from '@/components/AssistantChat/messages/MessageMetadata'
 import { isNestedInteractiveEvent } from '@/components/AssistantChat/messages/metadataToggle'
+import { MessageTimestamp } from '@/components/AssistantChat/messages/MessageTimestamp'
 
 export function HappyUserMessage() {
     const ctx = useHappyChatContext()
@@ -75,8 +76,9 @@ export function HappyUserMessage() {
             >
                 <div className="ml-auto w-full max-w-[92%]">
                     <CliOutputBlock text={cliText} />
-                    {hasMetadata && (
-                        <div className="mt-1 flex justify-end">
+                    <div className="mt-1 flex items-center justify-end gap-2">
+                        <MessageTimestamp className="text-[10px] leading-none text-[var(--app-hint)]" />
+                        {hasMetadata && (
                             <button
                                 type="button"
                                 onClick={() => setShowMetadata((open) => !open)}
@@ -85,8 +87,8 @@ export function HappyUserMessage() {
                             >
                                 {showMetadata ? 'Hide metadata' : 'Show metadata'}
                             </button>
-                        </div>
-                    )}
+                        )}
+                    </div>
                     {showMetadata && invokedAt != null && (
                         <MessageMetadata invokedAt={invokedAt} className="mt-1 justify-end" />
                     )}
@@ -135,6 +137,9 @@ export function HappyUserMessage() {
                         </div>
                     )}
                 </div>
+                <div className="flex justify-end">
+                    <MessageTimestamp className="text-[10px] leading-none text-[var(--app-hint)]" />
+                </div>
                 {showMetadata && invokedAt != null && (
                     <MessageMetadata invokedAt={invokedAt} className="justify-end opacity-60" />
                 )}