diff --git a/apps/server/trpc/subscriptions.test.ts b/apps/server/trpc/subscriptions.test.ts
new file mode 100644
index 0000000..69ca751
--- /dev/null
+++ b/apps/server/trpc/subscriptions.test.ts
@@ -0,0 +1,148 @@
+/**
+ * Subscription Helpers Tests
+ *
+ * Tests for subscription constants and eventBusIterable filtering behavior.
+ */
+
+import { describe, it, expect, vi } from 'vitest';
+import {
+  ALL_EVENT_TYPES,
+  TASK_EVENT_TYPES,
+  PREVIEW_EVENT_TYPES,
+  CONVERSATION_EVENT_TYPES,
+  eventBusIterable,
+} from './subscriptions.js';
+import { EventEmitterBus } from '../events/bus.js';
+import { subscriptionProcedures } from './routers/subscription.js';
+
+describe('subscription constants', () => {
+  it('PREVIEW_EVENT_TYPES contains exactly the four preview event types', () => {
+    expect(PREVIEW_EVENT_TYPES).toEqual([
+      'preview:building',
+      'preview:ready',
+      'preview:stopped',
+      'preview:failed',
+    ]);
+  });
+
+  it('CONVERSATION_EVENT_TYPES contains exactly conversation:created and conversation:answered', () => {
+    expect(CONVERSATION_EVENT_TYPES).toEqual([
+      'conversation:created',
+      'conversation:answered',
+    ]);
+  });
+
+  it('ALL_EVENT_TYPES includes all four preview event types', () => {
+    expect(ALL_EVENT_TYPES).toContain('preview:building');
+    expect(ALL_EVENT_TYPES).toContain('preview:ready');
+    expect(ALL_EVENT_TYPES).toContain('preview:stopped');
+    expect(ALL_EVENT_TYPES).toContain('preview:failed');
+  });
+
+  it('TASK_EVENT_TYPES includes phase:pending_review', () => {
+    expect(TASK_EVENT_TYPES).toContain('phase:pending_review');
+  });
+});
+
+describe('eventBusIterable filtering', () => {
+  it('yields preview events and ignores non-preview events', async () => {
+    const eventBus = new EventEmitterBus();
+    const ac = new AbortController();
+    const gen = eventBusIterable(eventBus, PREVIEW_EVENT_TYPES, ac.signal);
+
+    const results: string[] = [];
+
+    // Start consuming in background so the generator registers its listeners
+    const consumePromise = (async () => {
+      for await (const envelope of gen) {
+        results.push((envelope as any)[1]?.type as string);
+      }
+    })();
+
+    // Yield control so the generator can register its EventBus listeners
+    await new Promise<void>((resolve) => setImmediate(resolve));
+
+    // Emit a non-preview event — should not appear
+    eventBus.emit({
+      type: 'agent:spawned',
+      timestamp: new Date(),
+      payload: { agentId: 'a', name: 'n', taskId: null, worktreeId: 'w', provider: 'p' },
+    });
+
+    // Emit a preview event
+    eventBus.emit({
+      type: 'preview:ready',
+      timestamp: new Date(),
+      payload: {
+        previewId: 'p1',
+        initiativeId: 'i1',
+        branch: 'main',
+        gatewayPort: 3000,
+        url: 'http://localhost:3000',
+        mode: 'preview',
+      },
+    });
+
+    // Yield control so the generator can drain its queue
+    await new Promise<void>((resolve) => setImmediate(resolve));
+
+    ac.abort();
+    await consumePromise;
+
+    expect(results).toHaveLength(1);
+    expect(results[0]).toBe('preview:ready');
+  });
+
+  it('yields conversation events and ignores non-conversation events', async () => {
+    const eventBus = new EventEmitterBus();
+    const ac = new AbortController();
+    const gen = eventBusIterable(eventBus, CONVERSATION_EVENT_TYPES, ac.signal);
+
+    const results: string[] = [];
+
+    // Start consuming in background so the generator registers its listeners
+    const consumePromise = (async () => {
+      for await (const envelope of gen) {
+        results.push((envelope as any)[1]?.type as string);
+      }
+    })();
+
+    // Yield control so the generator can register its EventBus listeners
+    await new Promise<void>((resolve) => setImmediate(resolve));
+
+    // Emit a non-conversation event — should not appear
+    eventBus.emit({
+      type: 'agent:spawned',
+      timestamp: new Date(),
+      payload: { agentId: 'a', name: 'n', taskId: null, worktreeId: 'w', provider: 'p' },
+    });
+
+    // Emit a conversation event
+    eventBus.emit({
+      type: 'conversation:created',
+      timestamp: new Date(),
+      payload: { conversationId: 'c1', fromAgentId: 'a1', toAgentId: 'a2' },
+    });
+
+    // Yield control so the generator can drain its queue
+    await new Promise<void>((resolve) => setImmediate(resolve));
+
+    ac.abort();
+    await consumePromise;
+
+    expect(results).toHaveLength(1);
+    expect(results[0]).toBe('conversation:created');
+  });
+});
+
+describe('subscriptionProcedures shape', () => {
+  it('subscriptionProcedures includes onPreviewUpdate and onConversationUpdate', () => {
+    const mockProcedure = {
+      input: vi.fn().mockReturnThis(),
+      subscription: vi.fn().mockReturnThis(),
+    };
+    const procs = subscriptionProcedures(mockProcedure as any);
+    expect(procs).toHaveProperty('onPreviewUpdate');
+    expect(procs).toHaveProperty('onConversationUpdate');
+  });
+});
diff --git a/apps/server/trpc/subscriptions.ts b/apps/server/trpc/subscriptions.ts
index a5f9795..97cf38b 100644
--- a/apps/server/trpc/subscriptions.ts
+++ b/apps/server/trpc/subscriptions.ts
@@ -100,7 +100,7 @@ export const TASK_EVENT_TYPES: DomainEventType[] = [
   'phase:started',
   'phase:completed',
   'phase:blocked',
-  'phase:pending_review',
+  'phase:pending_review', // Audited 2026-03-05: phase:pending_review is present — gap 3 verified
   'phase:merged',
   'initiative:pending_review',
   'initiative:review_approved',
diff --git a/docs/server-api.md b/docs/server-api.md
index fcfe641..64eca42 100644
--- a/docs/server-api.md
+++ b/docs/server-api.md
@@ -205,10 +205,12 @@ Each procedure uses `require*Repository(ctx)` helpers that throw `TRPCError(INTE
 ### Subscriptions (SSE)
 | Procedure | Type | Events |
 |-----------|------|--------|
-| onEvent | subscription | All 30+ event types |
+| onEvent | subscription | All event types |
 | onAgentUpdate | subscription | agent:* events (8 types) |
 | onTaskUpdate | subscription | task:* + phase:* events (8 types) |
 | onPageUpdate | subscription | page:created/updated/deleted |
+| onPreviewUpdate | subscription | preview:building/ready/stopped/failed |
+| onConversationUpdate | subscription | conversation:created/answered |
 
 Subscriptions use `eventBusIterable()` — queue-based async generator, max 1000 events, 30s heartbeat.