Meta trains 140M to 950M reasoning models on 4.2T tokens
Meta released MobileLLM-R1 on September 12, 2025, a family of reasoning models at 140M, 360M and 950M parameters that write out a chain of intermediate steps before giving an answer instead of replying directly. Meta reports the 950M model scoring 74.0 on the MATH500 maths benchmark and 19.9 on LiveCodeBench v6, against 73.0 and 14.9 for Qwen3-0.6B. The technical report followed on September 29, 2025.
The three models saw 4.2T training tokens, which Meta puts at 11.7% of the 36T tokens behind Qwen3-0.6B. Pre-training ran in two phases of 2T tokens each, resampled from a curated pool of roughly 2T tokens of open datasets, followed by two mid-training phases of 100B tokens that distil from Llama-3.1-8B-Instruct as a teacher, then supervised fine-tuning on reasoning traces. Meta uses the result to argue that reasoning does not require the corpora above 10T tokens that recent models have been trained on.
For the post-trained models Meta’s table puts MobileLLM-R1-950M at 74.0 on MATH500, 67.5 on GSM8K, 15.5 on AIME 2024 and 19.9 on LiveCodeBench v6, where Qwen3-0.6B reaches 73.0, 79.2, 11.3 and 14.9 and DeepSeek-R1-Distill-Qwen-1.5B reaches 83.2, 77.3, 29.1 and 19.9. Among the models whose weights, data and recipe are all public, the same AIME figure compares with 0.6 for OLMo-2 1.48B and 0.3 for SmolLM2-1.7B. On code the 950M base model scores 46.3 on HumanEval against 30.5 for Qwen3-0.6B-Base, and the 140M base model reaches 15.9 where SmolLM2-135M scores 0.0.
Meta profiled the models through ExecuTorch on a Samsung Galaxy S22 with 8 GB of RAM, quantised to 4-bit weights with 8-bit dynamic activations. The 140M model generated 129.67 tok/s at a 1k context and 79.71 tok/s at 32k, the 950M model 31.05 tok/s at 1k before running out of memory at 16k, and Llama-3.2-1B 28.71 tok/s at 1k with the same memory failure. The architecture follows Meta’s earlier MobileLLM work and Llama 3.2, sharing one weight matrix between the input embedding and the output layer, and the post-trained models take a 32k context.
Meta released the weights on Hugging Face together with the training code, the data sources and the data mixing ratios on GitHub, under the FAIR Noncommercial Research License, which covers research, education and analysis but not commercial use. Access to the model repositories is gated behind a form.
Update, November 24, 2025. Meta released MobileLLM-R1.5 at the same three sizes, fine-tuned from the R1 models with one further round of on-policy distillation, where the student answers first and the teacher, here Llama-3.1-Nemotron-Nano-4B-v1.1, grades its own words back to it token by token. Meta reports the 950M version at 86.6 on MATH500, 82.6 on GSM8K, 39.9 on AIME 2024 and 29.1 on LiveCodeBench v6, up from 74.0, 67.5, 15.5 and 19.9 for MobileLLM-R1-950M, and says it beats DeepSeek-R1-Distill-Qwen-1.5B on every maths and coding benchmark it ran. At 360M Meta puts MATH500 at 63.4 against 28.4 and GSM8K at 52.8 against 24.5.