diff --git a/src/__tests__/agent-server-contract-types.test.ts b/src/__tests__/agent-server-contract-types.test.ts
index bf3e54b..ace5bc6 100644
--- a/src/__tests__/agent-server-contract-types.test.ts
+++ b/src/__tests__/agent-server-contract-types.test.ts
@@ -1,4 +1,5 @@
 import type { MCPClient } from '../client/mcp-client';
+import type { CreateConversationPayload } from '../client/conversation-client';
 import type { SettingsClient } from '../client/settings-client';
 import type {
   McpConfigPatchWritable,
@@ -50,6 +51,10 @@ function assertType<Type extends true>(_value: Type): void {
 }
 
 describe('Agent Server generated contract aliases', () => {
+  it('types the optional custom title-generation prompt', () => {
+    assertType<Equal<CreateConversationPayload['prompt'], string | undefined>>(true);
+  });
+
   it('statically checks settings client request and response types', () => {
     assertType<
       Equal<Awaited<ReturnType<SettingsClient['getAgentSchema']>>, AgentServerSettingsSchema>
diff --git a/src/client/conversation-client.ts b/src/client/conversation-client.ts
index a636c7a..c9023bd 100644
--- a/src/client/conversation-client.ts
+++ b/src/client/conversation-client.ts
@@ -42,6 +42,8 @@ export interface CreateConversationPayload {
   agent_profile_id?: string;
   agent?: unknown;
   agent_settings?: unknown;
+  /** Optional prompt override used for automatic conversation titles. */
+  prompt?: string;
   [key: string]: unknown;
 }