diff --git a/client/src/components/Web/Sources.tsx b/client/src/components/Web/Sources.tsx
index fa0ad75e996..8d0a1c9d741 100644
--- a/client/src/components/Web/Sources.tsx
+++ b/client/src/components/Web/Sources.tsx
@@ -408,7 +408,7 @@ const SourcesGroup = React.memo(function SourcesGroup({
   }, [sources, limit]);
 
   return (
-    <div className="grid w-full grid-cols-4 gap-2 overflow-x-auto">
+    <div className="hide-scrollbar grid w-full grid-cols-4 gap-2 overflow-x-auto">
       <OGDialog>
         {visibleSources.map((source, i) => (
           <div key={`source-${i}`} className="w-full min-w-[7.5rem]">
@@ -497,7 +497,7 @@ function FilesGroup({ files, messageId, conversationId, limit = 3 }: FilesGroupP
   const hasMoreFiles = remainingFiles.length > 0;
 
   return (
-    <div className="grid w-full grid-cols-4 gap-2 overflow-x-auto">
+    <div className="hide-scrollbar grid w-full grid-cols-4 gap-2 overflow-x-auto">
       <OGDialog>
         {visibleFiles.map((file, i) => (
           <div key={`file-${i}`} className="w-full min-w-[7.5rem]">
diff --git a/e2e/specs/mock/db.ts b/e2e/specs/mock/db.ts
index 4a0492eb7a0..be9d8b6ec46 100644
--- a/e2e/specs/mock/db.ts
+++ b/e2e/specs/mock/db.ts
@@ -127,6 +127,8 @@ export interface SeedMessage {
   model?: string;
   /** Attachments on the turn, as the client renders them (an image opens the lightbox). */
   files?: Record<string, unknown>[];
+  /** Tool attachments on the turn, such as the web search results behind its sources. */
+  attachments?: Record<string, unknown>[];
 }
 
 /**
diff --git a/e2e/specs/mock/scenarios/source-rails.spec.ts b/e2e/specs/mock/scenarios/source-rails.spec.ts
new file mode 100644
index 00000000000..84fbe22bce0
--- /dev/null
+++ b/e2e/specs/mock/scenarios/source-rails.spec.ts
@@ -0,0 +1,112 @@
+import { randomUUID } from 'crypto';
+import { expect, test } from '@playwright/test';
+import { deleteConversations, seedConversations, seedMessages } from '../db';
+import { getE2EUser } from '../../../setup/user';
+
+/**
+ * The web search source rails scroll sideways when the sources outgrow the row. They hide
+ * their scrollbar the way the other carousels do, and their links stay reachable by keyboard.
+ */
+
+const SOURCE_COUNT = 8;
+const REGION_NAME = 'Search results and sources';
+
+test.use({ viewport: { width: 360, height: 800 } });
+
+/** A two-lane assistant turn, the shape that renders the sources region, with web search results. */
+async function seedSourcesChat(title: string): Promise<string> {
+  const conversationId = randomUUID();
+  const { email } = getE2EUser();
+  await seedConversations(email, [{ conversationId, title, updatedAt: new Date() }]);
+  const userMessageId = randomUUID();
+  const assistantMessageId = randomUUID();
+  const organic = Array.from({ length: SOURCE_COUNT }, (_, index) => ({
+    title: `Source ${index + 1}`,
+    link: `https://source-${index + 1}.e2e.invalid/page`,
+    snippet: `Snippet ${index + 1}`,
+    attribution: `source-${index + 1}.e2e.invalid`,
+  }));
+  await seedMessages(email, conversationId, [
+    {
+      messageId: userMessageId,
+      parentMessageId: '00000000-0000-0000-0000-000000000000',
+      text: 'Search the web.',
+      isCreatedByUser: true,
+      sender: 'User',
+    },
+    {
+      messageId: assistantMessageId,
+      parentMessageId: userMessageId,
+      text: 'Two lanes answered.',
+      isCreatedByUser: false,
+      sender: 'Mock Provider A',
+      content: [
+        { type: 'text', text: 'Lane one answered.', groupId: 1, agentId: 'agent_lane_one' },
+        { type: 'text', text: 'Lane two answered.', groupId: 1, agentId: 'agent_lane_two' },
+      ],
+      attachments: [
+        {
+          type: 'web_search',
+          messageId: assistantMessageId,
+          toolCallId: randomUUID(),
+          conversationId,
+          web_search: { turn: 0, organic, topStories: [], images: [], references: [] },
+        },
+      ],
+    },
+  ]);
+  return conversationId;
+}
+
+test.describe('web search source rails', () => {
+  test('the source rail scrolls sideways without drawing a scrollbar @scenario:source-rails-hide-scrollbar', async ({
+    page,
+  }) => {
+    test.setTimeout(90000);
+    const conversationId = await seedSourcesChat('Source rails scrollbar');
+    try {
+      await page.goto(`/c/${conversationId}`);
+      const region = page.getByRole('region', { name: REGION_NAME });
+      await expect(region).toBeVisible({ timeout: 20000 });
+      const rail = region
+        .getByRole('link')
+        .first()
+        .locator('xpath=ancestor::div[contains(@class, "overflow-x-auto")][1]');
+      const metrics = await rail.evaluate((node) => {
+        node.style.width = '200px';
+        return {
+          overflowX: getComputedStyle(node).overflowX,
+          scrollbarWidth: getComputedStyle(node).scrollbarWidth,
+          overflowing: node.scrollWidth > node.clientWidth,
+        };
+      });
+      expect(metrics).toEqual({ overflowX: 'auto', scrollbarWidth: 'none', overflowing: true });
+    } finally {
+      await deleteConversations([conversationId]);
+    }
+  });
+
+  test('links in an overflowing source rail stay reachable by keyboard @scenario:source-rails-stay-keyboard-reachable', async ({
+    page,
+  }) => {
+    test.setTimeout(90000);
+    const conversationId = await seedSourcesChat('Source rails keyboard');
+    try {
+      await page.goto(`/c/${conversationId}`);
+      const region = page.getByRole('region', { name: REGION_NAME });
+      await expect(region).toBeVisible({ timeout: 20000 });
+      const last = region.getByRole('link', { name: /Source 3/ }).first();
+      await region.getByRole('link').first().focus();
+      for (let step = 0; step < 12; step++) {
+        if (await last.evaluate((node) => node === document.activeElement)) {
+          break;
+        }
+        await page.keyboard.press('Tab');
+      }
+      await expect(last).toBeFocused();
+      await expect(last).toBeInViewport();
+    } finally {
+      await deleteConversations([conversationId]);
+    }
+  });
+});