RULER scoring + training tightly coupled to Litellm/OpenAI, cannot cleanly use ChatOllama/ChatNVIDIA as judge/inference models

Description

In my setup, I want to:

• Use a local Ollama server (and potentially NVIDIA’s API in the future) as:

  • The main agent model (for rollouts).
  • The judge model (for RULER scoring).

However, the current ART stack makes this very difficult because:

• RULER scoring (ruler_score_group and related helpers) rely on Litellm in a way that expects OpenAI-style models.
• init_chat_model also wraps everything in a ChatOpenAI instance (see separate issue).
• This means I cannot simply pass ChatOllama or ChatNVIDIA (LangChain chat models) as the inference/judge model for training.

Practically:

• If I try to step away from OpenAI and use:

  • Local Ollama for inference
  • Non-OpenAI providers as judges

• I run into incompatibilities where:

  • RULER expects Litellm’s OpenAI-style model identifiers and behavior.
  • ART’s helpers are “too bound” to OpenAI semantics.

What I’d like

• A more provider-agnostic design for:

  • RULER scoring
  • Training
  • init_chat_model

• The ability to cleanly use:

  • ChatOllama (LangChain)
  • ChatNVIDIA
  • or other LangChain BaseChatModel implementations

• Without having to hack around Litellm / OpenAI assumptions.

Why this matters

• ART is otherwise a great framework for agent RL.

• Many users want to move to:

  • Local models (Ollama)
  • Different clouds (NVIDIA, etc.)

• Tight coupling to OpenAI via Litellm in the RULER path makes this significantly harder.

Request

• Please consider:

  • Abstracting RULER to accept any LangChain-compatible ChatModel for structured scoring.
  • Or providing a documented way to plug in non-OpenAI judgment models (e.g. a “judge_fn” that uses arbitrary models).

Start with ruler_score_group and its related helpers, then inspect init_chat_model and the separate issue it references. Trace where LiteLLM and OpenAI-style assumptions enter RULER and training; done means the project either supports LangChain BaseChatModel providers such as ChatOllama and ChatNVIDIA or documents an arbitrary judge_fn integration path.