Solar Open

Solar Open#

Solar Open is a large-scale open-weight language model developed by Upstage. It is an auto-regressive Mixture-of-Experts (MoE) transformer that supports English and Korean, and it handles both reasoning and non-reasoning chat as well as tool (function) calling.

Furiosa-LLM runs Solar Open in NVFP4A16 (NVFP4 weights with 16-bit activations and KV cache). FuriosaAI publishes pre-compiled NVFP4A16 builds under the furiosa-ai organization on the Hugging Face Hub, each shipping a Furiosa Executable Bundle (FXB) for running it on FuriosaAI RNGD with Furiosa-LLM. The upstream weights also run on other frameworks (such as vLLM, SGLang, and Transformers); for usage with those, see the upstream model card linked below.

Variants#

Model

Quantization

RNGD cards

Notes

furiosa-ai/Solar-Open-100B-NVFP4A16

NVFP4A16

4

100B MoE; reasoning / non-reasoning

  • Architecture: SolarOpen (Mixture-of-Experts), SolarOpenForCausalLM

  • Input / Output: Text / Text

  • Quantization: The weights are quantized to NVFP4 (4-bit floating point), while activations and the KV cache remain in 16-bit precision (NVFP4A16).

Usage#

To run this model with Furiosa-LLM, follow the example commands below after installing Furiosa-LLM and its prerequisites.

Launch the server#

The simplest way to serve the model is:

# Launch the server, listening on port 8000 by default
furiosa-llm serve furiosa-ai/Solar-Open-100B-NVFP4A16 \
  --reasoning-parser solar_open

The --reasoning-parser solar_open flag separates the model’s chain of thought from the final answer (see Reasoning below).

When the server is ready, you will see:

INFO:     Started server process [27507]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://0.0.0.0:8000 (Press CTRL+C to quit)

Launch the server with tool calling#

To enable tool (function) calling, start the server with the solar_open tool-call parser:

furiosa-llm serve furiosa-ai/Solar-Open-100B-NVFP4A16 \
  --reasoning-parser solar_open \
  --enable-auto-tool-choice \
  --tool-call-parser solar_open

Query the server#

The server exposes an OpenAI-compatible API. You can send a request with curl:

curl http://localhost:8000/v1/chat/completions \
    -H "Content-Type: application/json" \
    -d '{
    "model": "furiosa-ai/Solar-Open-100B-NVFP4A16",
    "messages": [{"role": "user", "content": "What is the capital of France?"}]
    }' \
    | python -m json.tool

Reasoning#

With --reasoning-parser solar_open, Solar Open returns its reasoning separately from the final answer:

  • response.choices[].message.reasoning (non-streaming)

  • response.choices[].delta.reasoning (streaming)

Note: The reasoning field is not part of the OpenAI API specification, but it is the convention OpenAI recommends for returning the chain-of-thought (CoT) in Chat Completions-compatible APIs. The OpenAI Agents SDK uses reasoning as its primary property for the CoT, and many LLM serving frameworks (such as vLLM) follow the same convention. It appears only in responses that contain reasoning content; accessing it on a response without reasoning content raises an AttributeError.

Tool calling#

With the server launched using --enable-auto-tool-choice --tool-call-parser solar_open, you can pass tools and let the model decide when to call them. See the Tool Calling guide for a complete client example and details on tool-choice options.

Learn more#