diff --git a/frontend/components/pro/running-footer.tsx b/frontend/components/pro/running-footer.tsx
index 58525503..69ad2816 100644
--- a/frontend/components/pro/running-footer.tsx
+++ b/frontend/components/pro/running-footer.tsx
@@ -11,7 +11,7 @@ import { RiArrowDownSLine, RiStopFill } from "@remixicon/react";
 import { Dropdown, DropdownPopover, DropdownTrigger } from "@/components/base/dropdown/dropdown";
 import { StatusRow } from "@/components/pro/composer-status-bar";
 import type { RunningStatus } from "@/components/pro/running-phase";
-import { ElapsedTimer } from "@/components/session-ui/background-status-pill";
+import { ElapsedTimer } from "@/components/session-ui/elapsed-timer";
 
 export function RunningFooter({
   status,
diff --git a/frontend/components/session-ui/background-status-pill.tsx b/frontend/components/session-ui/background-status-pill.tsx
index e7a556e2..6380a10c 100644
--- a/frontend/components/session-ui/background-status-pill.tsx
+++ b/frontend/components/session-ui/background-status-pill.tsx
@@ -11,36 +11,12 @@
 // this port is the standalone slim pill. The label is a plain prop (upstream
 // derives it from backgroundLiveness + fleet liveCount), the elapsed timer is
 // added from their MessagesTimeline WorkingTimer pattern (self-ticking text
-// node, no React commits - that component is private to working-indicator.tsx),
+// node, no React commits - that component now lives in elapsed-timer.tsx),
 // and Stop accepts the EXISTING cancel handler as a prop (session-view
 // handleStop posts the durable /cancel; no new API call here). Their
 // animate-status-pulse -> our ai-loading-pixel; tokens are our semantic tokens.
 
-import { useEffect, useRef } from "react";
-import { formatWorkingTimerNow } from "./work-entry";
-
-/** Self-ticking elapsed label; updates its own text node outside React commits. */
-export function ElapsedTimer({ startedAt }: { startedAt: string }) {
-  const textRef = useRef<HTMLSpanElement>(null);
-  const initialText = formatWorkingTimerNow(startedAt);
-
-  useEffect(() => {
-    const updateText = () => {
-      if (textRef.current) {
-        textRef.current.textContent = formatWorkingTimerNow(startedAt);
-      }
-    };
-    updateText();
-    const id = setInterval(updateText, 1000);
-    return () => clearInterval(id);
-  }, [startedAt]);
-
-  return (
-    <span ref={textRef} className="tabular-nums">
-      {initialText}
-    </span>
-  );
-}
+import { ElapsedTimer } from "./elapsed-timer";
 
 /**
  * Slim persistent status pill for a thread with live work: pulsing dot + status
diff --git a/frontend/components/session-ui/elapsed-timer.test.tsx b/frontend/components/session-ui/elapsed-timer.test.tsx
new file mode 100644
index 00000000..45ca71e8
--- /dev/null
+++ b/frontend/components/session-ui/elapsed-timer.test.tsx
@@ -0,0 +1,9 @@
+import { expect, test } from "bun:test";
+import { renderToStaticMarkup } from "react-dom/server";
+import { ElapsedTimer } from "./elapsed-timer";
+
+test("the timer renders the current elapsed text in tabular figures", () => {
+  const html = renderToStaticMarkup(<ElapsedTimer startedAt={new Date().toISOString()} />);
+  expect(html).toContain("tabular-nums");
+  expect(html).toContain("0s");
+});
diff --git a/frontend/components/session-ui/elapsed-timer.tsx b/frontend/components/session-ui/elapsed-timer.tsx
new file mode 100644
index 00000000..d073e9a3
--- /dev/null
+++ b/frontend/components/session-ui/elapsed-timer.tsx
@@ -0,0 +1,32 @@
+"use client";
+
+// The thread's one self-ticking elapsed label (shared by the working line and
+// the background status pill): renders the current elapsed text, then updates
+// its own text node every second outside React commits, from the
+// MessagesTimeline WorkingTimer pattern vendored with working-indicator.tsx.
+
+import { useEffect, useRef } from "react";
+import { formatWorkingTimerNow } from "./work-entry";
+
+/** Self-ticking elapsed label; updates its own text node outside React commits. */
+export function ElapsedTimer({ startedAt }: { startedAt: string }) {
+  const textRef = useRef<HTMLSpanElement>(null);
+  const initialText = formatWorkingTimerNow(startedAt);
+
+  useEffect(() => {
+    const updateText = () => {
+      if (textRef.current) {
+        textRef.current.textContent = formatWorkingTimerNow(startedAt);
+      }
+    };
+    updateText();
+    const id = setInterval(updateText, 1000);
+    return () => clearInterval(id);
+  }, [startedAt]);
+
+  return (
+    <span ref={textRef} className="tabular-nums">
+      {initialText}
+    </span>
+  );
+}
diff --git a/frontend/components/session-ui/working-indicator.tsx b/frontend/components/session-ui/working-indicator.tsx
index 71d35e3b..ec95faec 100644
--- a/frontend/components/session-ui/working-indicator.tsx
+++ b/frontend/components/session-ui/working-indicator.tsx
@@ -6,36 +6,13 @@
 // Source: apps/web/src/components/chat/MessagesTimeline.tsx (WorkingTimelineRow +
 // WorkingTimer): three staggered pulse dots, a SELF-TICKING "Working for Xs" label
 // (writes its own text node every second so elapsed time never causes a React
-// commit while streaming), and an optional current-step suffix.
+// commit while streaming), and an optional current-step suffix. The timer itself
+// now lives in elapsed-timer.tsx, shared with the background status pill.
 //
 // Port notes: their `animate-status-pulse` utility -> our `ai-loading-pixel`
 // stagger (globals.css, reduced-motion aware); tokens are our semantic tokens.
 
-import { useEffect, useRef } from "react";
-import { formatWorkingTimerNow } from "./work-entry";
-
-/** Live "Working for Xs" label; updates its own text node outside React commits. */
-function WorkingTimer({ createdAt }: { createdAt: string }) {
-  const textRef = useRef<HTMLSpanElement>(null);
-  const initialText = formatWorkingTimerNow(createdAt);
-
-  useEffect(() => {
-    const updateText = () => {
-      if (textRef.current) {
-        textRef.current.textContent = formatWorkingTimerNow(createdAt);
-      }
-    };
-    updateText();
-    const id = setInterval(updateText, 1000);
-    return () => clearInterval(id);
-  }, [createdAt]);
-
-  return (
-    <span ref={textRef} className="tabular-nums">
-      {initialText}
-    </span>
-  );
-}
+import { ElapsedTimer } from "./elapsed-timer";
 
 export function WorkingIndicator({
   createdAt,
@@ -59,7 +36,7 @@ export function WorkingIndicator({
         <span className="shrink-0">
           {createdAt ? (
             <>
-              Working for <WorkingTimer createdAt={createdAt} />
+              Working for <ElapsedTimer startedAt={createdAt} />
             </>
           ) : (
             "Working…"