diff --git a/src/components/AgentChatView.client.test.tsx b/src/components/AgentChatView.client.test.tsx
index f9f3bde9..bb782a8f 100644
--- a/src/components/AgentChatView.client.test.tsx
+++ b/src/components/AgentChatView.client.test.tsx
@@ -123,6 +123,9 @@ afterEach(() => {
   container.remove();
 });
 
+// Exact counts are formatted in the host's locale, so the expected text is too.
+const n = (value: number) => value.toLocaleString();
+
 describe('Codex chat view', () => {
   it('shows context capacity, remaining tokens, and over-limit usage independently of session totals', async () => {
     dispose = render(() => <AgentChatView task={task()} agentId="agent-1" active />, container);
@@ -132,7 +135,7 @@ describe('Codex chat view', () => {
     expect(container.querySelector('.codex-chat-context')?.textContent).toContain('Context —');
     mocks.channel?.onmessage?.(state({ contextUsage: { usedTokens: 50000, maxTokens: 200000 } }));
     expect(meter()?.textContent).toContain('Context 25% · 150K left');
-    expect(meter()?.title).toContain('50,000 of 200,000');
+    expect(meter()?.title).toContain(`${n(50_000)} of ${n(200_000)}`);
     expect(meter()?.getAttribute('aria-valuenow')).toBe('50000');
     mocks.channel?.onmessage?.(state({ contextUsage: { usedTokens: 190000, maxTokens: 200000 } }));
     expect(meter()?.dataset.level).toBe('high');
@@ -140,7 +143,7 @@ describe('Codex chat view', () => {
     expect(meter()?.textContent).toContain('Context 105% · 0 left');
     expect(meter()?.dataset.level).toBe('full');
     expect(meter()?.getAttribute('aria-valuenow')).toBe('200000');
-    expect(meter()?.getAttribute('aria-valuetext')).toContain('210,000 of 200,000');
+    expect(meter()?.getAttribute('aria-valuetext')).toContain(`${n(210_000)} of ${n(200_000)}`);
     mocks.channel?.onmessage?.(state({ contextUsage: { usedTokens: 0, maxTokens: 200000 } }));
     expect(meter()?.textContent).toContain('Context 0% · 200K left');
     mocks.channel?.onmessage?.(state({ threadId: 'new-session' }));
@@ -163,8 +166,8 @@ describe('Codex chat view', () => {
       }),
     );
     expect(counter()?.textContent).toContain('12.5K tokens');
-    expect(counter()?.title).toContain('12,500 tokens');
-    expect(counter()?.title).toContain('12,000 input');
+    expect(counter()?.title).toContain(`${n(12_500)} tokens`);
+    expect(counter()?.title).toContain(`${n(12_000)} input`);
     mocks.channel?.onmessage?.(
       state({
         tokenUsage: { totalTokens: 0, inputTokens: 0, outputTokens: 0, scope: 'connection' },
diff --git a/src/components/SessionPicker.client.test.tsx b/src/components/SessionPicker.client.test.tsx
index c6cba8f6..e58fc56b 100644
--- a/src/components/SessionPicker.client.test.tsx
+++ b/src/components/SessionPicker.client.test.tsx
@@ -151,14 +151,16 @@ describe('SessionPicker', () => {
 
 describe('relativeTime', () => {
   const now = Date.parse('2026-09-17T12:00:00Z');
+  // The assertions match English wording.
+  const ago = (iso: string) => relativeTime(Date.parse(iso), now, 'en');
 
   it('picks the largest fitting unit', () => {
-    expect(relativeTime(Date.parse('2026-09-15T12:00:00Z'), now)).toMatch(/day/);
-    expect(relativeTime(Date.parse('2026-09-17T09:00:00Z'), now)).toMatch(/hour/);
-    expect(relativeTime(Date.parse('2026-09-17T11:30:00Z'), now)).toMatch(/minute/);
+    expect(ago('2026-09-15T12:00:00Z')).toMatch(/day/);
+    expect(ago('2026-09-17T09:00:00Z')).toMatch(/hour/);
+    expect(ago('2026-09-17T11:30:00Z')).toMatch(/minute/);
   });
 
   it('falls through to seconds for a very recent session', () => {
-    expect(relativeTime(Date.parse('2026-09-17T11:59:50Z'), now)).toMatch(/second/);
+    expect(ago('2026-09-17T11:59:50Z')).toMatch(/second/);
   });
 });
diff --git a/src/components/SessionPicker.tsx b/src/components/SessionPicker.tsx
index ffb350a4..3968a235 100644
--- a/src/components/SessionPicker.tsx
+++ b/src/components/SessionPicker.tsx
@@ -6,9 +6,10 @@ import { canResumeSessionId } from '../../electron/shared/session-resume';
 import type { SessionRecord } from '../../electron/shared/session-record';
 
 /** Relative age of a session, via the platform formatter rather than a table
- *  of thresholds. Exported for its test. */
-export function relativeTime(epochMs: number, now = Date.now()): string {
-  const format = new Intl.RelativeTimeFormat(undefined, { numeric: 'auto' });
+ *  of thresholds. Exported for its test, which pins `locale` so the wording it
+ *  checks does not depend on the host's default. */
+export function relativeTime(epochMs: number, now = Date.now(), locale?: string): string {
+  const format = new Intl.RelativeTimeFormat(locale, { numeric: 'auto' });
   const seconds = Math.round((epochMs - now) / 1000);
   const units: [Intl.RelativeTimeFormatUnit, number][] = [
     ['day', 86_400],