VibeThinker-1.5B is a 1.5B parameter dense language model by WeiboAI, fine-tuned from Qwen2.5-Math-1.5B for competitive math and algorithm coding. Despite its small size, it achieves remarkable results:

Benchmark	VibeThinker-1.5B	DeepSeek R1 (671B)
AIME24	80.3	79.8
AIME25	74.4	70.0
HMMT25	50.4	41.7

Best results with English prompts on competitive-style math and coding problems.

Conversion Details

Parameter	Value
Architecture	Qwen 2.5
Context Length	2048
Batch Size	64
Chunks	4 (hybrid)
FFN Quantization	LUT6 (Apple Neural Engine), per-channel group size 4
LM Head Quantization	LUT6 (Apple Neural Engine), per-channel group size 4
Embeddings	Unquantized
Argmax in Model	No

Hybrid FP32 First Chunk

This model uses a hybrid precision layout. Chunk 1 of 4 (qwen25_FFN_PF_lut6_chunk_01of04.mlmodelc) runs the first transformer layer's attention in FP32 (unquantized), while chunks 2-4 use standard LUT6 quantization.

Why: VibeThinker has unusually high-magnitude Q/K projection biases in layer 0, causing FP16 attention logit overflow (+inf) before masking. This leads to softmax saturation and catastrophic output divergence. Running first-layer attention at full precision eliminates the overflow and recovers near-exact parity with the original Hugging Face model.

Chunk 1 is significantly smaller (~15 MB vs ~310-340 MB for the other chunks) since it only contains the first-layer attention residual path.

Recommended Sampling

yaml

temperature: 0.6
top_p: 0.95
top_k: 0
do_sample: true

Quick Start

bash

pip install coremltools transformers

# Basic chat
python chat.py --meta ./meta.yaml

# Full conversation mode with history
python chat_full.py --meta ./meta.yaml

Note: First load takes time as macOS places the model on the Neural Engine. Subsequent loads are fast.

iOS/macOS App

Try the ANEMLL Chat app on TestFlight:

Install TestFlight
Join beta: TestFlight Link
Add this model via its HuggingFace URL

License

MIT (ANEMLL conversion). The original model is also MIT licensed.

anemll/anemll-WeiboAI-VibeThinker-1.5B-ctx2048_0.3.5

anemll-WeiboAI-VibeThinker-1.5B-ctx2048

Original Model