openbmb/MiniCPM5-2B

Overview

MiniCPM5-2B is the 2B checkpoint in OpenBMB's MiniCPM5 series — a dense model built for on-device and resource-constrained deployment, with strong performance on agentic tool use, code generation, and reasoning tasks. It uses the standard LlamaForCausalLM architecture, so vLLM loads it natively with no custom kernels or model-code fork.

Its headline feature is hybrid reasoning: a single checkpoint serves as both a fast assistant (No-Think) and a deliberate reasoner (Think), toggled by the chat template's enable_thinking flag.

Prerequisites

• vLLM ≥ 0.21.0 — MiniCPM5-2B is supported natively as of the v0.21.0 release.

Launch command

Use the command builder above. The baseline is simply:

vllm serve openbmb/MiniCPM5-2B --port 8000

At ~2B params the model fits on a single GPU (TP=1). It supports the full native 128K context; drop --max-model-len to 8192 / 32768 to free KV cache on small GPUs.

Reasoning modes

Toggle the Reasoning feature to serve with deep-thinking on by default (--default-chat-template-kwargs '{"enable_thinking": true}'). You can also flip it per request via chat_template_kwargs:

curl http://localhost:8000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openbmb/MiniCPM5-2B",
    "messages": [{"role": "user", "content": "Explain GQA in one sentence."}],
    "temperature": 0.9, "top_p": 0.95, "max_tokens": 1024,
    "chat_template_kwargs": {"enable_thinking": true}
  }'

Mode	enable_thinking	temperature	top_p
Think	true	0.9	0.95
No-Think	false	1.0	0.95

Tool calling

MiniCPM5-2B emits XML-style tool calls. The minicpm5 parser (PR #43175) is natively supported in vLLM. Enable it with:

vllm serve openbmb/MiniCPM5-2B --port 8000 \
  --enable-auto-tool-choice \
  --tool-call-parser minicpm5

References

• Model card
• vLLM deployment cookbook
• MiniCPM Tech Report