Bug: LangChain Serialization Protocol for Custom Model Providers

[xunliu]

Problem

Two custom model providers were missing the LangChain serialization protocol, causing to receive {"type": "not_implemented"} instead of the actual model kwargs.

Affected classes

Class	File	Parent
PatchedChatDeepSeek	deerflow/models/patched_deepseek.py	ChatDeepSeek
CodexChatModel	deerflow/models/openai_codex_provider.py	BaseChatModel

Root cause

ChatDeepSeek does not implement is_lc_serializable(), so it returns False (the Serializable base class default). When a subclass inherits this, to_json() short-circuits to {"type": "not_implemented", "repr": "..."} with no kwargs field.

CodexChatModel inherits directly from BaseChatModel, which also does not override is_lc_serializable().

The other patched providers (PatchedChatOpenAI, PatchedChatMiniMax, VllmChatModel, ClaudeChatModel) are unaffected because their parent classes (ChatOpenAI, ChatAnthropic) already return True.