Chain sometimes hangs when unable to decode JSON

[sgiath]

I have noticed, that occasionally my subagents get stuck in a loop where they print this logs over and over:

  [warning] Error applying delta message. Reason: "tool_calls: arguments: invalid json"
  [warning] Error applying delta message. Reason: "tool_calls: arguments: invalid json"
  [warning] Error applying delta message. Reason: "tool_calls: arguments: invalid json"
  [warning] Error applying delta message. Reason: "tool_calls: arguments: invalid json"
  [warning] Error applying delta message. Reason: "tool_calls: arguments: invalid json"
  [warning] Error applying delta message. Reason: "tool_calls: arguments: invalid json"
  [warning] Error applying delta message. Reason: "tool_calls: arguments: invalid json"

I have traced it down to this place:
https://github.com/brainlid/langchain/blob/v0.4.1/lib/chains/llm_chain.ex#L1074-L1078

And the error seems to originate here:
https://github.com/brainlid/langchain/blob/v0.4.1/lib/message/tool_call.ex#L119

I am sure this is an error on the LLM side sending malformed response but I don't think it should be stuck in a loop. It eventually reach some max number of iterations and ends itself but I would expect it to end immediately and maybe print some more information why it failed.

I am using LLMChian with LangChain.ChatModels.ChatOpenAI on OpenRouter, I experienced it with different models but currently I am on moonshotai/kimi-k2-0905

I have created PR with test that exposes the behavior I am describing, hopefully it is clear what I mean. I have also included debug.log file with the real scenario where that happened (I have extended what is actually logged in the library to capture this).