fix(desktop): stop message age falling back to the 1970 epoch ("20663d ago")

apps/desktop/src/lib/chat-runtime.test.ts

@@ -6,6 +6,7 @@ import {
   attachmentDisplayText,
   attachmentId,
   coerceThinkingText,
+  messageCreatedAt,
   optimisticAttachmentRef,
   parseCommandDispatch,
   parseSlashCommand
@@ -178,3 +179,24 @@ describe('attachmentId', () => {
     expect(attachmentId('url', 'https://example.com/a')).not.toBe(attachmentId('url', 'https://example.com/b'))
   })
 })
+
+describe('messageCreatedAt', () => {
+  const NOW = Date.UTC(2026, 6, 28, 18, 0, 0)
+
+  it('reads the authoritative Unix-seconds timestamp (not ms)', () => {
+    // 1785282262s → July 2026, not the 1970 epoch a *1000-less read would give.
+    expect(messageCreatedAt({ timestamp: 1785282262 }, NOW).getFullYear()).toBe(2026)
+  })
+
+  it('falls back to now — never digs digits out of the id → "20663d ago" (1970)', () => {
+    // The old fallback did `new Date(Number(id.match(/\d+/)))`, so a session-style
+    // id like 20260728_184420_05e697 parsed to 20260728 *ms* = Jan 1970, showing
+    // as an absurd 20663-day age. A timestamp-less message is freshly created.
+    expect(messageCreatedAt({ timestamp: undefined }, NOW).getTime()).toBe(NOW)
+  })
+
+  it('treats a zero / non-finite timestamp as absent', () => {
+    expect(messageCreatedAt({ timestamp: 0 }, NOW).getTime()).toBe(NOW)
+    expect(messageCreatedAt({ timestamp: Number.NaN }, NOW).getTime()).toBe(NOW)
+  })
+})

apps/desktop/src/lib/chat-runtime.ts

@@ -368,13 +368,24 @@ export function quickModelOptions(
   return options.slice(0, 8)
 }
 
+// A message's display time. `timestamp` (Unix seconds) is authoritative when
+// present. Without it we fall back to *now* rather than digging digits out of
+// the id: message ids come in incompatible shapes — `assistant-<ms>`,
+// `<seconds>-<i>-<role>`, session-style `20260728_184420_…` — and feeding any
+// of them to `new Date()` (which reads ms) lands on the 1970 epoch, rendering
+// as an absurd "20663d ago". A timestamp-less message is a freshly created
+// optimistic/streaming one, so *now* is the right age anyway.
+export function messageCreatedAt(message: Pick<ChatMessage, 'timestamp'>, nowMs = Date.now()): Date {
+  return typeof message.timestamp === 'number' && Number.isFinite(message.timestamp) && message.timestamp > 0
+    ? new Date(message.timestamp * 1000)
+    : new Date(nowMs)
+}
+
 export function toRuntimeMessage(message: ChatMessage): ThreadMessage {
   const role =
     message.role === 'user' || message.role === 'assistant' || message.role === 'system' ? message.role : 'assistant'
 
-  const createdAt = message.timestamp
-    ? new Date(message.timestamp * 1000)
-    : new Date(Number(message.id.match(/\d+/)?.[0]) || Date.now())
+  const createdAt = messageCreatedAt(message)
 
   if (role === 'user') {
     return {