diff --git a/frontend/src/features/agents/CustomAgentChatView.test.tsx b/frontend/src/features/agents/CustomAgentChatView.test.tsx
index 18e15003..554811d6 100644
--- a/frontend/src/features/agents/CustomAgentChatView.test.tsx
+++ b/frontend/src/features/agents/CustomAgentChatView.test.tsx
@@ -288,6 +288,66 @@ describe("CustomAgentChatView", () => {
     }
   });
 
+  it("replays scrollback with the current reception time instead of the reduce index", async () => {
+    const replayReceivedAtMs = new Date("2026-08-15T13:08:00.000Z").getTime();
+    const indexOneTime = expectedChatTime(1);
+    const nowSpy = vi.spyOn(Date, "now").mockReturnValue(replayReceivedAtMs);
+    const agent = {
+      launchAgentChat: vi.fn(),
+      reattachAgentChat: vi.fn(async (sessionId: string) => ({
+        sessionId,
+        scrollback: [
+          { kind: "userPrompt" as const, text: "Replay prompt" },
+          { kind: "textDelta" as const, text: "Replay answer" },
+          { kind: "final" as const, content: "Replay completed" },
+        ],
+      })),
+      sendAgentChat: vi.fn(async () => {}),
+      cancelAgentChat: vi.fn(async () => {}),
+      closeAgentChat: vi.fn(async () => {}),
+    };
+
+    try {
+      render(
+        <DIProvider
+          gateways={{
+            agent,
+            system: { pickFile: vi.fn(async () => null) },
+          } as unknown as Gateways}
+        >
+          <CustomAgentChatView
+            projectId="project-1"
+            agentId="agent-1"
+            agentName="Worker"
+            profile={profile}
+            cwd="/repo"
+            nodeId="node-1"
+            sessionId="chat-session-1"
+            conversationId="conversation-1"
+            onSessionId={vi.fn()}
+            onConversationId={vi.fn()}
+          />
+        </DIProvider>,
+      );
+
+      const agentBubble = (await screen.findByText("Replay answer")).closest("div");
+      const finalBubble = screen.getByText("Replay completed").closest("div");
+
+      expect(agentBubble).toBeTruthy();
+      expect(finalBubble).toBeTruthy();
+      expect(
+        within(agentBubble!).getByText(expectedChatTime(replayReceivedAtMs)),
+      ).toBeTruthy();
+      expect(
+        within(finalBubble!).getByText(expectedChatTime(replayReceivedAtMs)),
+      ).toBeTruthy();
+      expect(within(agentBubble!).queryByText(indexOneTime)).toBeNull();
+      expect(within(finalBubble!).queryByText(indexOneTime)).toBeNull();
+    } finally {
+      nowSpy.mockRestore();
+    }
+  });
+
   it("resizes the composer vertically with mouse, keyboard, and double-click reset", async () => {
     const rectSpy = vi
       .spyOn(HTMLElement.prototype, "getBoundingClientRect")
diff --git a/frontend/src/features/agents/CustomAgentChatView.tsx b/frontend/src/features/agents/CustomAgentChatView.tsx
index 6439ac46..3b4837d9 100644
--- a/frontend/src/features/agents/CustomAgentChatView.tsx
+++ b/frontend/src/features/agents/CustomAgentChatView.tsx
@@ -75,6 +75,14 @@ const chatConversationViewCache = new Map<string, CachedChatView>();
 const EMPTY_MODEL_RESPONSE_MESSAGE = "Le modèle n'a renvoyé aucune réponse.";
 const COMPOSER_RESIZE_STEP = 12;
 const FALLBACK_COMPOSER_HEIGHT = 64;
+const MIN_REASONABLE_CHAT_TIMESTAMP_MS = Date.UTC(2020, 0, 1);
+const MAX_REASONABLE_CHAT_TIMESTAMP_MS = Date.UTC(2100, 0, 1);
+const MIN_REASONABLE_CHAT_TIMESTAMP_SECONDS = Math.floor(
+  MIN_REASONABLE_CHAT_TIMESTAMP_MS / 1000,
+);
+const MAX_REASONABLE_CHAT_TIMESTAMP_SECONDS = Math.floor(
+  MAX_REASONABLE_CHAT_TIMESTAMP_MS / 1000,
+);
 
 export function __clearCustomAgentChatViewCacheForTests() {
   chatSessionViewCache.clear();
@@ -1120,7 +1128,10 @@ export function CustomAgentChatView({
       setCurrentSession(reattached.sessionId);
       if (options.applyScrollback) {
         scrollbackChunkCountRef.current = reattached.scrollback.length;
-        const replayed = reattached.scrollback.reduce(foldChunk, emptyChatViewState());
+        const replayed = reattached.scrollback.reduce(
+          (state, chunk) => foldChunk(state, chunk),
+          emptyChatViewState(),
+        );
         applyChatViewState(replayed);
         setBusy(turnsIndicateBusy(replayed));
       }
@@ -2175,14 +2186,34 @@ function ChatBubble({
   );
 }
 
+function normalizeChatReceivedAtMs(receivedAtMs: number | undefined): number | undefined {
+  if (!Number.isFinite(receivedAtMs) || receivedAtMs === undefined || receivedAtMs <= 0) {
+    return undefined;
+  }
+  if (
+    receivedAtMs >= MIN_REASONABLE_CHAT_TIMESTAMP_SECONDS &&
+    receivedAtMs < MAX_REASONABLE_CHAT_TIMESTAMP_SECONDS
+  ) {
+    return receivedAtMs * 1000;
+  }
+  if (
+    receivedAtMs < MIN_REASONABLE_CHAT_TIMESTAMP_MS ||
+    receivedAtMs >= MAX_REASONABLE_CHAT_TIMESTAMP_MS
+  ) {
+    return undefined;
+  }
+  return receivedAtMs;
+}
+
 function formatChatReceivedTime(receivedAtMs: number | undefined): string {
-  if (!Number.isFinite(receivedAtMs) || !receivedAtMs) return "";
+  const normalizedAtMs = normalizeChatReceivedAtMs(receivedAtMs);
+  if (!normalizedAtMs) return "";
   try {
     const parts = new Intl.DateTimeFormat(undefined, {
       hour: "2-digit",
       minute: "2-digit",
       hourCycle: "h23",
-    }).formatToParts(new Date(receivedAtMs));
+    }).formatToParts(new Date(normalizedAtMs));
     const hour = parts.find((part) => part.type === "hour")?.value;
     const minute = parts.find((part) => part.type === "minute")?.value;
     return hour && minute ? `${hour}:${minute}` : "";
@@ -2201,7 +2232,8 @@ function ChatMessageMeta({
   labelClassName?: string;
 }) {
   const time = formatChatReceivedTime(receivedAtMs);
-  const dateTime = time && receivedAtMs ? new Date(receivedAtMs).toISOString() : undefined;
+  const normalizedAtMs = normalizeChatReceivedAtMs(receivedAtMs);
+  const dateTime = time && normalizedAtMs ? new Date(normalizedAtMs).toISOString() : undefined;
   return (
     <div className="mb-1 flex min-w-0 flex-col gap-0.5 text-xs sm:flex-row sm:items-baseline sm:justify-between sm:gap-3">
       <span className={cn("min-w-0 truncate font-medium text-muted", labelClassName)}>