diff --git a/tests/live/live.test.ts b/tests/live/live.test.ts
index ca46a6f..5aa1a9c 100644
--- a/tests/live/live.test.ts
+++ b/tests/live/live.test.ts
@@ -281,7 +281,8 @@ d('live CLI (Twitter/X)', () => {
     const tweets = parseJson<Array<{ id?: string; author?: { username?: string } }>>(userTweets.stdout);
     expect(Array.isArray(tweets)).toBe(true);
     expect(tweets.length).toBeGreaterThan(0);
-    expect(tweets[0].author?.username?.toLowerCase()).toBe(testHandle.toLowerCase());
+    const handleLower = testHandle.toLowerCase();
+    expect(tweets.some((t) => t.author?.username?.toLowerCase() === handleLower)).toBe(true);
   });
 
   it('user-tweets paged JSON returns { tweets, nextCursor }', async () => {
diff --git a/tests/twitter-client.user-lookup.test.ts b/tests/twitter-client.user-lookup.test.ts
new file mode 100644
index 0000000..06683bf
--- /dev/null
+++ b/tests/twitter-client.user-lookup.test.ts
@@ -0,0 +1,166 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { TwitterClient } from '../src/lib/twitter-client.js';
+import { validCookies } from './twitter-client-fixtures.js';
+
+const originalFetch = global.fetch;
+
+afterEach(() => {
+  global.fetch = originalFetch;
+  vi.restoreAllMocks();
+});
+
+describe('TwitterClient getUserIdByUsername', () => {
+  let mockFetch: ReturnType<typeof vi.fn>;
+
+  beforeEach(() => {
+    mockFetch = vi.fn();
+    global.fetch = mockFetch as unknown as typeof fetch;
+  });
+
+  it('resolves username to userId via GraphQL', async () => {
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      status: 200,
+      json: async () => ({
+        data: {
+          user: {
+            result: {
+              __typename: 'User',
+              rest_id: '12345',
+              legacy: {
+                screen_name: 'testuser',
+                name: 'Test User',
+              },
+            },
+          },
+        },
+      }),
+    });
+
+    const client = new TwitterClient({ cookies: validCookies });
+    const result = await client.getUserIdByUsername('@testuser');
+
+    expect(result.success).toBe(true);
+    expect(result.userId).toBe('12345');
+    expect(result.username).toBe('testuser');
+    expect(result.name).toBe('Test User');
+  });
+
+  it('handles username without @ prefix', async () => {
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      status: 200,
+      json: async () => ({
+        data: {
+          user: {
+            result: {
+              __typename: 'User',
+              rest_id: '67890',
+              legacy: {
+                screen_name: 'anotheruser',
+                name: 'Another User',
+              },
+            },
+          },
+        },
+      }),
+    });
+
+    const client = new TwitterClient({ cookies: validCookies });
+    const result = await client.getUserIdByUsername('anotheruser');
+
+    expect(result.success).toBe(true);
+    expect(result.userId).toBe('67890');
+  });
+
+  it('returns error for invalid username format', async () => {
+    const client = new TwitterClient({ cookies: validCookies });
+
+    const result = await client.getUserIdByUsername('invalid handle with spaces');
+
+    expect(result.success).toBe(false);
+    expect(result.error).toContain('Invalid username');
+    expect(mockFetch).not.toHaveBeenCalled();
+  });
+
+  it('returns error for empty username', async () => {
+    const client = new TwitterClient({ cookies: validCookies });
+
+    const result = await client.getUserIdByUsername('');
+
+    expect(result.success).toBe(false);
+    expect(result.error).toContain('Invalid username');
+    expect(mockFetch).not.toHaveBeenCalled();
+  });
+
+  it('returns error for username exceeding 15 characters', async () => {
+    const client = new TwitterClient({ cookies: validCookies });
+
+    const result = await client.getUserIdByUsername('thisusernameiswaytoolong');
+
+    expect(result.success).toBe(false);
+    expect(result.error).toContain('Invalid username');
+    expect(mockFetch).not.toHaveBeenCalled();
+  });
+
+  it('returns error when user is unavailable', async () => {
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      status: 200,
+      json: async () => ({
+        data: {
+          user: {
+            result: {
+              __typename: 'UserUnavailable',
+            },
+          },
+        },
+      }),
+    });
+
+    const client = new TwitterClient({ cookies: validCookies });
+    const result = await client.getUserIdByUsername('suspended');
+
+    expect(result.success).toBe(false);
+    expect(result.error).toContain('not found or unavailable');
+  });
+
+  it('retries with fallback query IDs on 404', async () => {
+    mockFetch
+      .mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+        text: async () => 'Not found',
+      })
+      .mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+        text: async () => 'Not found',
+      })
+      .mockResolvedValueOnce({
+        ok: true,
+        status: 200,
+        json: async () => ({
+          data: {
+            user: {
+              result: {
+                __typename: 'User',
+                rest_id: '99999',
+                legacy: {
+                  screen_name: 'founduser',
+                  name: 'Found User',
+                },
+              },
+            },
+          },
+        }),
+      });
+
+    const client = new TwitterClient({ cookies: validCookies });
+    const result = await client.getUserIdByUsername('founduser');
+
+    expect(result.success).toBe(true);
+    expect(result.userId).toBe('99999');
+    expect(mockFetch).toHaveBeenCalledTimes(3);
+  });
+});
diff --git a/tests/twitter-client.user-tweets.test.ts b/tests/twitter-client.user-tweets.test.ts
index a31ef15..57524c1 100644
--- a/tests/twitter-client.user-tweets.test.ts
+++ b/tests/twitter-client.user-tweets.test.ts
@@ -9,162 +9,6 @@ afterEach(() => {
   vi.restoreAllMocks();
 });
 
-describe('TwitterClient getUserIdByUsername', () => {
-  let mockFetch: ReturnType<typeof vi.fn>;
-
-  beforeEach(() => {
-    mockFetch = vi.fn();
-    global.fetch = mockFetch as unknown as typeof fetch;
-  });
-
-  it('resolves username to userId via GraphQL', async () => {
-    mockFetch.mockResolvedValueOnce({
-      ok: true,
-      status: 200,
-      json: async () => ({
-        data: {
-          user: {
-            result: {
-              __typename: 'User',
-              rest_id: '12345',
-              legacy: {
-                screen_name: 'testuser',
-                name: 'Test User',
-              },
-            },
-          },
-        },
-      }),
-    });
-
-    const client = new TwitterClient({ cookies: validCookies });
-    const result = await client.getUserIdByUsername('@testuser');
-
-    expect(result.success).toBe(true);
-    expect(result.userId).toBe('12345');
-    expect(result.username).toBe('testuser');
-    expect(result.name).toBe('Test User');
-  });
-
-  it('handles username without @ prefix', async () => {
-    mockFetch.mockResolvedValueOnce({
-      ok: true,
-      status: 200,
-      json: async () => ({
-        data: {
-          user: {
-            result: {
-              __typename: 'User',
-              rest_id: '67890',
-              legacy: {
-                screen_name: 'anotheruser',
-                name: 'Another User',
-              },
-            },
-          },
-        },
-      }),
-    });
-
-    const client = new TwitterClient({ cookies: validCookies });
-    const result = await client.getUserIdByUsername('anotheruser');
-
-    expect(result.success).toBe(true);
-    expect(result.userId).toBe('67890');
-  });
-
-  it('returns error for invalid username format', async () => {
-    const client = new TwitterClient({ cookies: validCookies });
-
-    const result = await client.getUserIdByUsername('invalid handle with spaces');
-
-    expect(result.success).toBe(false);
-    expect(result.error).toContain('Invalid username');
-    expect(mockFetch).not.toHaveBeenCalled();
-  });
-
-  it('returns error for empty username', async () => {
-    const client = new TwitterClient({ cookies: validCookies });
-
-    const result = await client.getUserIdByUsername('');
-
-    expect(result.success).toBe(false);
-    expect(result.error).toContain('Invalid username');
-    expect(mockFetch).not.toHaveBeenCalled();
-  });
-
-  it('returns error for username exceeding 15 characters', async () => {
-    const client = new TwitterClient({ cookies: validCookies });
-
-    const result = await client.getUserIdByUsername('thisusernameiswaytoolong');
-
-    expect(result.success).toBe(false);
-    expect(result.error).toContain('Invalid username');
-    expect(mockFetch).not.toHaveBeenCalled();
-  });
-
-  it('returns error when user is unavailable', async () => {
-    mockFetch.mockResolvedValueOnce({
-      ok: true,
-      status: 200,
-      json: async () => ({
-        data: {
-          user: {
-            result: {
-              __typename: 'UserUnavailable',
-            },
-          },
-        },
-      }),
-    });
-
-    const client = new TwitterClient({ cookies: validCookies });
-    const result = await client.getUserIdByUsername('suspended');
-
-    expect(result.success).toBe(false);
-    expect(result.error).toContain('not found or unavailable');
-  });
-
-  it('retries with fallback query IDs on 404', async () => {
-    mockFetch
-      .mockResolvedValueOnce({
-        ok: false,
-        status: 404,
-        text: async () => 'Not found',
-      })
-      .mockResolvedValueOnce({
-        ok: false,
-        status: 404,
-        text: async () => 'Not found',
-      })
-      .mockResolvedValueOnce({
-        ok: true,
-        status: 200,
-        json: async () => ({
-          data: {
-            user: {
-              result: {
-                __typename: 'User',
-                rest_id: '99999',
-                legacy: {
-                  screen_name: 'founduser',
-                  name: 'Found User',
-                },
-              },
-            },
-          },
-        }),
-      });
-
-    const client = new TwitterClient({ cookies: validCookies });
-    const result = await client.getUserIdByUsername('founduser');
-
-    expect(result.success).toBe(true);
-    expect(result.userId).toBe('99999');
-    expect(mockFetch).toHaveBeenCalledTimes(3);
-  });
-});
-
 describe('TwitterClient getUserTweets', () => {
   let mockFetch: ReturnType<typeof vi.fn>;