Lapras: Latent Reasoning for Time Series Language Models

Yuliang Chen, Yu Yvonne Wu, Arvind Pillai, Nicholas C. Jacobson, Andrew Campbell

arXiv 2610.11111· 2026
ECGIMUsleepOpen Weights

Summary

Post-training framework for time-series language models (TSLMs): instead of verbalising the signal in an explicit chain-of-thought, the model reasons through continuous "thoughts" in the joint time-series–language space and emits text only for the answer. Trained by teacher–student self-distillation: a CoT-SFT teacher reasons in text, and the student aligns its answer-stage hidden states to the teacher's. Evaluated on four TSLM backbones (ChatTS-7B, OpenTSLM-1B Flamingo variant, SLIP-1B, ITFormer-0.5B) and five QA tasks: ECG (ECG-Reasoning benchmark, Oh et al.

Key facts

Form Factor
other
License
Not stated

Reported benchmarks

Human activity recognition (IMU)

opentslm-har-cot · Macro-F1 ↑

#1 of 1
73.53 (%)

Multiple-choice HAR QA (OpenTSLM, Langer et al. 2026), 8,222 test items; same-backbone Explicit-CoT 67.27, No-CoT 63.41; OpenTSLM-1B+Lapras 68.20, SLIP-1B+Lapras 70.75.

Sleep staging

opentslm-sleep-cot · Macro-F1 ↑

#1 of 1
79.49 (%)

Multiple-choice sleep-stage QA (OpenTSLM, Langer et al. 2026), 923 test items, 1-ch 1500-step windows; same-backbone No-CoT 78.05, Explicit-CoT 65.48.

Updated: Oct 12, 2026