Instructions to use microsoft/FastContext-1.0-4B-SFT with libraries, inference providers, notebooks, and local apps. Follow these links to get started.

Libraries

How to use microsoft/FastContext-1.0-4B-SFT with Transformers:

# Use a pipeline as a high-level helper
from transformers import pipeline

pipe = pipeline("text-generation", model="microsoft/FastContext-1.0-4B-SFT")
messages = [
    {"role": "user", "content": "Who are you?"},
]
pipe(messages)

# Load model directly
from transformers import AutoTokenizer, AutoModelForMultimodalLM

tokenizer = AutoTokenizer.from_pretrained("microsoft/FastContext-1.0-4B-SFT")
model = AutoModelForMultimodalLM.from_pretrained("microsoft/FastContext-1.0-4B-SFT")
messages = [
    {"role": "user", "content": "Who are you?"},
]
inputs = tokenizer.apply_chat_template(
	messages,
	add_generation_prompt=True,
	tokenize=True,
	return_dict=True,
	return_tensors="pt",
).to(model.device)

outputs = model.generate(**inputs, max_new_tokens=40)
print(tokenizer.decode(outputs[0][inputs["input_ids"].shape[-1]:]))

Inference
Notebooks
Google Colab
Kaggle
Local Apps Settings

vLLM

How to use microsoft/FastContext-1.0-4B-SFT with vLLM:

Install from pip and serve model

# Install vLLM from pip:
pip install vllm
# Start the vLLM server:
vllm serve "microsoft/FastContext-1.0-4B-SFT"
# Call the server using curl (OpenAI-compatible API):
curl -X POST "http://localhost:8000/v1/chat/completions" \
	-H "Content-Type: application/json" \
	--data '{
		"model": "microsoft/FastContext-1.0-4B-SFT",
		"messages": [
			{
				"role": "user",
				"content": "What is the capital of France?"
			}
		]
	}'

Use Docker

docker model run hf.co/microsoft/FastContext-1.0-4B-SFT

SGLang

How to use microsoft/FastContext-1.0-4B-SFT with SGLang:

Install from pip and serve model

# Install SGLang from pip:
pip install sglang
# Start the SGLang server:
python3 -m sglang.launch_server \
    --model-path "microsoft/FastContext-1.0-4B-SFT" \
    --host 0.0.0.0 \
    --port 30000
# Call the server using curl (OpenAI-compatible API):
curl -X POST "http://localhost:30000/v1/chat/completions" \
	-H "Content-Type: application/json" \
	--data '{
		"model": "microsoft/FastContext-1.0-4B-SFT",
		"messages": [
			{
				"role": "user",
				"content": "What is the capital of France?"
			}
		]
	}'

Use Docker images

docker run --gpus all \
    --shm-size 32g \
    -p 30000:30000 \
    -v ~/.cache/huggingface:/root/.cache/huggingface \
    --env "HF_TOKEN=<secret>" \
    --ipc=host \
    lmsysorg/sglang:latest \
    python3 -m sglang.launch_server \
        --model-path "microsoft/FastContext-1.0-4B-SFT" \
        --host 0.0.0.0 \
        --port 30000
# Call the server using curl (OpenAI-compatible API):
curl -X POST "http://localhost:30000/v1/chat/completions" \
	-H "Content-Type: application/json" \
	--data '{
		"model": "microsoft/FastContext-1.0-4B-SFT",
		"messages": [
			{
				"role": "user",
				"content": "What is the capital of France?"
			}
		]
	}'

Docker Model Runner
How to use microsoft/FastContext-1.0-4B-SFT with Docker Model Runner:
```
docker model run hf.co/microsoft/FastContext-1.0-4B-SFT
```

FastContext-1.0-4B-SFT in production agent integration

by ghostwithahat - opened 3 days ago

Discussion

ghostwithahat

3 days ago

•

edited 3 days ago

Great Idea! Thank you!

I integrated FastContext-1.0-4B-SFT as an explore_repository subagent into a production Go-based coding agent (ahle). Served unquantized via llama.cpp on RTX 3090 (104K ctx, 80 GPU layers, temperature 0.0). Findings after ~30 real-world runs:

What works:

Tool selection is good — the model prefers grep first, then targeted reads
With a directory listing in the system prompt (as in system.md), path hallucination drops to near zero
The model finds the right files roughly 60% of the time

What doesn't:

<final_answer> tags are inconsistent — the model often writes correct citation text but omits the XML wrapper. I had to add a regex fallback to extract bare /path/file.go:42-58 (reason) lines.
Line ranges are too broad (file.go:1-500) even when the answer spans 20 lines. The main agent (DeepSeek v4) re-reads cited files manually because it cannot trust coarse ranges. Net token savings: ~0%.
A "last turn" reminder system message helped, but only partially.

I'm testing the 4B-RL variant next, hoping the format penalties and line-level F1 reward produce tighter citations. Happy to share comparison results.

maoquan-ms

Microsoft org about 21 hours ago

thanks for the feedback,
since this basic version of the model (4B) was only fine-tuned (SFT) on a 3k trajectory dataset, hallucinations regarding file paths are unfortunately expected. A much more robust version will be updated soon.
if you can share your specific bad cases here (repos), it would really help us improve.

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