update

backend/models.py

@@ -75,3 +75,18 @@ class TopicSuggestRequest(BaseModel):
 class TopicSuggestion(BaseModel):
     title: str
     reason: str
+
+
+class ChatMessage(BaseModel):
+    role: Literal["user", "assistant"]
+    content: str = Field(min_length=1, max_length=8000)
+
+
+class GuideChatRequest(BaseModel):
+    section: str = Field(default="", max_length=20000)
+    outline: str = Field(default="", max_length=8000)
+    messages: list[ChatMessage] = Field(min_length=1)
+
+
+class GuideChatResponse(BaseModel):
+    reply: str