fix: handle empty reasoning content for DeepSeek v4 models (#7823)

Co-authored-by: Copilot <copilot@github.com>

Author: Soulter

astrbot/core/provider/sources/openai_source.py

@@ -982,6 +982,11 @@ def _finally_convert_payload(self, payloads: dict) -> None:
         """Finally convert the payload. Such as think part conversion, tool inject."""
         model = payloads.get("model", "").lower()
         is_gemini = "gemini" in model
+        deepseek_reasoning_models = {"deepseek-v4-pro", "deepseek-v4-flash"}
+        is_deepseek_v4_reasoning = (
+            model in deepseek_reasoning_models
+            or "api.deepseek.com" in self.client.base_url.host
+        )
 
         for message in payloads.get("messages", []):
             if message.get("role") == "assistant" and isinstance(
@@ -997,7 +1002,14 @@ def _finally_convert_payload(self, payloads: dict) -> None:
                 # Some providers (Grok, etc.) reject empty content lists.
                 # When all parts were think blocks, fall back to None.
                 message["content"] = new_content or None
-                if reasoning_content:
+                if is_deepseek_v4_reasoning and not reasoning_content:
+                    logger.info(
+                        "Deepseek v4 model requires non-empty reasoning content, but got empty. Setting to 'none' to satisfy the requirement."
+                    )
+                    # Deepseek models require the field on assistant
+                    # history messages, even when the reasoning content is empty.
+                    message["reasoning_content"] = "none"
+                elif reasoning_content:
                     message["reasoning_content"] = reasoning_content
 
             # Gemini 的 function_response 要求 google.protobuf.Struct（即 JSON 对象），