diff --git a/packages/ui/src/components/sections/openchamber/PasskeySettings.tsx b/packages/ui/src/components/sections/openchamber/PasskeySettings.tsx
index 5dcbc15c..450410d6 100644
--- a/packages/ui/src/components/sections/openchamber/PasskeySettings.tsx
+++ b/packages/ui/src/components/sections/openchamber/PasskeySettings.tsx
@@ -219,7 +219,7 @@ export const PasskeySettings: React.FC = () => {
             {passkeys.map((passkey) => (
               <SettingsFieldRow
                 key={passkey.id}
-                label={<span className="truncate">{passkey.label}</span>}
+                label={<span className="truncate" title={passkey.label}>{passkey.label}</span>}
                 alignEnd={false}
                 controlClassName="justify-between sm:flex-1"
               >
diff --git a/packages/ui/src/components/sections/shared/SettingsSection.tsx b/packages/ui/src/components/sections/shared/SettingsSection.tsx
index 7672b8a2..5cc520f9 100644
--- a/packages/ui/src/components/sections/shared/SettingsSection.tsx
+++ b/packages/ui/src/components/sections/shared/SettingsSection.tsx
@@ -310,8 +310,8 @@ export const SettingsFieldRow: React.FC<SettingsFieldRowProps> = ({
       )}
     >
       <div className="min-w-0 @xl:w-56 @xl:shrink-0">
-        <div className="flex items-center gap-1.5">
-          <div className={SETTINGS_FIELD_LABEL_CLASS}>{label}</div>
+        <div className="flex min-w-0 items-center gap-1.5">
+          <div className={cn('min-w-0 truncate', SETTINGS_FIELD_LABEL_CLASS)}>{label}</div>
           {info != null ? <SettingsInfoHint>{info}</SettingsInfoHint> : null}
         </div>
         {description != null ? (
diff --git a/packages/ui/src/components/sections/shared/fieldrow.repro.test.tsx b/packages/ui/src/components/sections/shared/fieldrow.repro.test.tsx
new file mode 100644
index 00000000..a13820db
--- /dev/null
+++ b/packages/ui/src/components/sections/shared/fieldrow.repro.test.tsx
@@ -0,0 +1,71 @@
+import { afterEach, describe, expect, test } from 'bun:test';
+import { Window } from 'happy-dom';
+import React, { act } from 'react';
+import { createRoot, type Root } from 'react-dom/client';
+import { SettingsFieldRow } from '@/components/sections/shared/SettingsSection';
+
+// Browser-generated passkeys (e.g. Edge on Windows) use the full user-agent
+// string as the device label, so it is very long.
+const longLabel =
+  'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36 Edg/125.0.0.0';
+
+let windowInstance: Window;
+let host: HTMLDivElement;
+let root: Root;
+
+afterEach(() => {
+  root?.unmount();
+});
+
+describe('PasskeySettings long device-name label (issue #3181)', () => {
+  test('label truncation requires min-w-0 on every flex ancestor', async () => {
+    windowInstance = new Window({ width: 1000, height: 800 });
+    Object.assign(globalThis, {
+      window: windowInstance,
+      document: windowInstance.document,
+      HTMLElement: windowInstance.HTMLElement,
+      Element: windowInstance.Element,
+      Node: windowInstance.Node,
+      IS_REACT_ACT_ENVIRONMENT: true,
+    });
+
+    host = document.createElement('div');
+    document.body.appendChild(host);
+    root = createRoot(host);
+
+    await act(async () => {
+      root.render(
+        // Mirrors the PasskeySettings row (label = passkey.label with `truncate`).
+        <SettingsFieldRow
+          label={<span className="truncate">{longLabel}</span>}
+          alignEnd={false}
+          controlClassName="justify-between sm:flex-1"
+        >
+          <span className="typography-meta text-muted-foreground truncate">Added Aug 27, 2026</span>
+          <button>Delete</button>
+        </SettingsFieldRow>,
+      );
+    });
+
+    // For `truncate` (overflow:hidden + text-overflow:ellipsis + white-space:nowrap)
+    // to constrain a flex child, every flex ancestor between the row and the
+    // truncated element must carry min-w-0. Without it, the flex item's default
+    // min-width:auto stops it shrinking, and the long text overflows the 224px
+    // label column, overlaying the date and delete button in the control column.
+    const row = host.firstElementChild as HTMLElement;
+    const labelColumn = row?.firstElementChild as HTMLElement;
+    const innerFlex = labelColumn?.firstElementChild as HTMLElement;
+    const labelDiv = innerFlex?.firstElementChild as HTMLElement;
+    const labelSpan = labelDiv?.firstElementChild as HTMLElement;
+
+    const flexAncestors = [labelColumn, innerFlex, labelDiv].filter(Boolean);
+    const missingMinW0 = flexAncestors.filter(
+      (el) => !String(el.className).split(/\s+/).includes('min-w-0'),
+    );
+
+    expect(labelSpan?.className.split(/\s+/)).toContain('truncate');
+    // Repro: two intermediate flex containers lack min-w-0, so the ellipsis is
+    // inert and the long label overflows its column.
+    expect(missingMinW0.length).toBe(0);
+  });
+});