diff --git a/ui/tests/unit/ui/components/account/flow-viz/utils.test.ts b/ui/tests/unit/ui/components/account/flow-viz/utils.test.ts
new file mode 100644
index 00000000..4a7c1eac
--- /dev/null
+++ b/ui/tests/unit/ui/components/account/flow-viz/utils.test.ts
@@ -0,0 +1,184 @@
+/**
+ * Unit tests for generateConnectionEvents() in flow-viz/utils.ts
+ *
+ * Regression coverage for the timeline single-account dominance bug:
+ * accounts with more recent lastUsedAt were dominating the 100-event cap
+ * because per-account base time was used instead of a shared max.
+ */
+
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import { MAX_TIMELINE_EVENTS, generateConnectionEvents } from '@/components/account/flow-viz/utils';
+import type { AccountData } from '@/components/account/flow-viz/types';
+
+// Deterministic Math.random: cycles 0.1, 0.5, 0.9 repeatedly
+function mockRandom(): void {
+  const values = [0.1, 0.5, 0.9];
+  let idx = 0;
+  vi.spyOn(Math, 'random').mockImplementation(() => {
+    const val = values[idx % values.length];
+    idx++;
+    return val;
+  });
+}
+
+function makeAccount(overrides: Partial<AccountData> & Pick<AccountData, 'id' | 'email'>): AccountData {
+  return {
+    provider: 'agy',
+    successCount: 0,
+    failureCount: 0,
+    color: '#000000',
+    ...overrides,
+  };
+}
+
+describe('generateConnectionEvents()', () => {
+  beforeEach(() => {
+    mockRandom();
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  // -----------------------------------------------------------------------
+  // Core regression: multi-account interleaving
+  // -----------------------------------------------------------------------
+
+  it('includes events from more than one account when accounts have different lastUsedAt', () => {
+    const now = Date.now();
+
+    const accounts: AccountData[] = [
+      makeAccount({
+        id: 'a1',
+        email: 'recent@example.com',
+        successCount: 60,
+        // Most recent — was the bug trigger
+        lastUsedAt: new Date(now - 1_000).toISOString(),
+      }),
+      makeAccount({
+        id: 'a2',
+        email: 'older@example.com',
+        successCount: 60,
+        // 7 days older
+        lastUsedAt: new Date(now - 7 * 24 * 60 * 60 * 1000).toISOString(),
+      }),
+    ];
+
+    const events = generateConnectionEvents(accounts);
+
+    // Slice to cap
+    const displayed = events.slice(0, MAX_TIMELINE_EVENTS);
+    const emails = new Set(displayed.map((e) => e.accountEmail));
+
+    expect(emails.size).toBeGreaterThan(1);
+    expect(emails.has('recent@example.com')).toBe(true);
+    expect(emails.has('older@example.com')).toBe(true);
+  });
+
+  it('returns at most MAX_TIMELINE_EVENTS events (cap respected by caller slice)', () => {
+    // generateConnectionEvents returns all events unsorted-by-cap; cap is applied by caller.
+    // But we verify total output does not exceed successCount + failureCount across accounts.
+    const accounts: AccountData[] = [
+      makeAccount({ id: 'a1', email: 'a@x.com', successCount: 50, failureCount: 10 }),
+      makeAccount({ id: 'a2', email: 'b@x.com', successCount: 50, failureCount: 10 }),
+    ];
+
+    const events = generateConnectionEvents(accounts);
+
+    expect(events).toHaveLength(120); // 60 + 60 total before cap
+    expect(events.slice(0, MAX_TIMELINE_EVENTS)).toHaveLength(MAX_TIMELINE_EVENTS);
+  });
+
+  it('returns events sorted by timestamp descending', () => {
+    const accounts: AccountData[] = [
+      makeAccount({ id: 'a1', email: 'a@x.com', successCount: 10 }),
+      makeAccount({ id: 'a2', email: 'b@x.com', successCount: 10 }),
+    ];
+
+    const events = generateConnectionEvents(accounts);
+
+    for (let i = 1; i < events.length; i++) {
+      expect(events[i - 1].timestamp.getTime()).toBeGreaterThanOrEqual(
+        events[i].timestamp.getTime()
+      );
+    }
+  });
+
+  // -----------------------------------------------------------------------
+  // Edge cases
+  // -----------------------------------------------------------------------
+
+  it('returns empty array for empty accounts input', () => {
+    expect(generateConnectionEvents([])).toEqual([]);
+  });
+
+  it('returns empty array when all accounts have zero counts', () => {
+    const accounts: AccountData[] = [
+      makeAccount({ id: 'a1', email: 'a@x.com', successCount: 0, failureCount: 0 }),
+      makeAccount({ id: 'a2', email: 'b@x.com', successCount: 0, failureCount: 0 }),
+    ];
+
+    expect(generateConnectionEvents(accounts)).toEqual([]);
+  });
+
+  it('handles accounts with no lastUsedAt (falls back to now)', () => {
+    const accounts: AccountData[] = [
+      makeAccount({ id: 'a1', email: 'no-date@x.com', successCount: 5 }),
+    ];
+
+    const events = generateConnectionEvents(accounts);
+
+    expect(events).toHaveLength(5);
+    events.forEach((e) => expect(e.accountEmail).toBe('no-date@x.com'));
+  });
+
+  it('handles single account — all events belong to that account', () => {
+    const accounts: AccountData[] = [
+      makeAccount({
+        id: 'solo',
+        email: 'solo@x.com',
+        successCount: 3,
+        failureCount: 2,
+        lastUsedAt: new Date().toISOString(),
+      }),
+    ];
+
+    const events = generateConnectionEvents(accounts);
+
+    expect(events).toHaveLength(5);
+    events.forEach((e) => expect(e.accountEmail).toBe('solo@x.com'));
+  });
+
+  it('generates correct event ids and status labels', () => {
+    const accounts: AccountData[] = [
+      makeAccount({ id: 'acc1', email: 'x@x.com', successCount: 2, failureCount: 1 }),
+    ];
+
+    const events = generateConnectionEvents(accounts);
+
+    const successes = events.filter((e) => e.status === 'success');
+    const failures = events.filter((e) => e.status === 'failed');
+
+    expect(successes).toHaveLength(2);
+    expect(failures).toHaveLength(1);
+
+    // IDs follow pattern: {accountId}-{status}-{index}
+    expect(successes[0].id).toMatch(/^acc1-success-\d+$/);
+    expect(failures[0].id).toMatch(/^acc1-failed-\d+$/);
+  });
+
+  it('all generated timestamps are not in the future', () => {
+    const now = new Date();
+    const accounts: AccountData[] = [
+      makeAccount({ id: 'a1', email: 'a@x.com', successCount: 10 }),
+    ];
+
+    const events = generateConnectionEvents(accounts);
+
+    events.forEach((e) => {
+      // Allow 1s tolerance for test execution time
+      expect(e.timestamp.getTime()).toBeLessThanOrEqual(now.getTime() + 1000);
+    });
+  });
+});