diff --git a/packages/desktop/src/common/adapter/apiModelMapper.ts b/packages/desktop/src/common/adapter/apiModelMapper.ts
index 020864f5e3..0167d70b02 100644
--- a/packages/desktop/src/common/adapter/apiModelMapper.ts
+++ b/packages/desktop/src/common/adapter/apiModelMapper.ts
@@ -54,13 +54,14 @@ export type CreateConversationBodyInput = {
  * agent types carry model info via `extra`.
  */
 export function buildCreateConversationBody(p: CreateConversationBodyInput): Record<string, unknown> {
-  const hasAssistant = p.assistant !== undefined && p.assistant !== null;
+  // aioncore >= v0.1.72 rejects create bodies without top-level `type` and
+  // `extra` ("Invalid JSON request body"), so both must always be present.
   const body: Record<string, unknown> = {
-    type: hasAssistant ? undefined : p.type,
+    type: p.type,
     id: p.id,
     name: p.name,
     assistant: p.assistant,
-    extra: p.extra,
+    extra: p.extra ?? {},
   };
   const model = p.type === 'acp' ? undefined : toApiModelOptional(p.model);
   if (model) body.model = model;
diff --git a/packages/desktop/src/renderer/pages/guid/hooks/useGuidSend.ts b/packages/desktop/src/renderer/pages/guid/hooks/useGuidSend.ts
index 710e988851..0a26143cb9 100644
--- a/packages/desktop/src/renderer/pages/guid/hooks/useGuidSend.ts
+++ b/packages/desktop/src/renderer/pages/guid/hooks/useGuidSend.ts
@@ -177,6 +177,7 @@ export const useGuidSend = (deps: GuidSendDeps): GuidSendResult => {
       }
       try {
         const conversation = await ipcBridge.conversation.create.invoke({
+          type: 'aionrs',
           name: input,
           model: current_model,
           assistant: {
@@ -232,6 +233,7 @@ export const useGuidSend = (deps: GuidSendDeps): GuidSendResult => {
 
     try {
       const conversation = await ipcBridge.conversation.create.invoke({
+        type: 'acp',
         name: input,
         assistant: {
           id: assistantConversationId,
diff --git a/tests/unit/common-adapter/apiModelMapper.test.ts b/tests/unit/common-adapter/apiModelMapper.test.ts
index 2e0d04baaf..563ec7372d 100644
--- a/tests/unit/common-adapter/apiModelMapper.test.ts
+++ b/tests/unit/common-adapter/apiModelMapper.test.ts
@@ -154,7 +154,7 @@ describe('apiModelMapper', () => {
       expect('model' in body).toBe(false);
     });
 
-    it('strips legacy type when assistant identity is present', () => {
+    it('passes type through when assistant identity is present', () => {
       const body = buildCreateConversationBody({
         type: 'acp',
         name: 'hello',
@@ -162,7 +162,7 @@ describe('apiModelMapper', () => {
         extra: {},
       });
 
-      expect(body.type).toBeUndefined();
+      expect(body.type).toBe('acp');
     });
 
     it('omits the top-level model for ACP creates that pass an empty placeholder', () => {
diff --git a/tests/unit/renderer/useGuidSend.dom.test.ts b/tests/unit/renderer/useGuidSend.dom.test.ts
index 8227698a02..db76a917ba 100644
--- a/tests/unit/renderer/useGuidSend.dom.test.ts
+++ b/tests/unit/renderer/useGuidSend.dom.test.ts
@@ -94,7 +94,7 @@ describe('useGuidSend', () => {
 
     expect(createConversationInvokeMock).toHaveBeenCalledTimes(1);
     const payload = createConversationInvokeMock.mock.calls[0][0];
-    expect(payload.type).toBeUndefined();
+    expect(payload.type).toBe('acp');
     expect('model' in payload).toBe(false);
     expect(payload.assistant?.conversation_overrides?.permission).toBe('bypassPermissions');
     expect(payload.assistant?.conversation_overrides?.model).toBe('claude-opus');
@@ -200,7 +200,7 @@ describe('useGuidSend', () => {
     });
 
     const payload = createConversationInvokeMock.mock.calls[0][0];
-    expect(payload.type).toBeUndefined();
+    expect(payload.type).toBe('aionrs');
     expect(payload.model).toBe(deps.current_model);
     expect(payload.assistant?.id).toBe('bare:aionrs');
     expect(payload.assistant?.conversation_overrides?.skill_ids).toEqual(['pdf-reader']);
@@ -239,7 +239,7 @@ describe('useGuidSend', () => {
 
     const payload = createConversationInvokeMock.mock.calls[0][0];
     expect(payload.assistant?.id).toBe('bare:claude');
-    expect(payload.type).toBeUndefined();
+    expect(payload.type).toBe('acp');
     expect('model' in payload).toBe(false);
     expect(payload.extra.preset_assistant_id).toBeUndefined();
     expect(payload.extra.backend).toBeUndefined();