初始化提交

backend/app/modules/chat/policies.py

@@ -0,0 +1,11 @@
+"""聊天策略模块。"""
+
+from app.core.config import settings
+from app.core.errors import AppError
+
+
+def validate_text_message(*, modality: str, content: str) -> None:
+    if modality != "text":
+        raise AppError("unsupported_media_type", "当前阶段仅支持文本消息。")
+    if len(content.encode("utf-8")) > settings.max_text_message_bytes:
+        raise AppError("payload_too_large", "单条文本消息超过大小限制。")