@inproceedings{qiu-etal-2026-bag,
title = "Bag-of-Tokens Tuning: Calibrating {LLM} Logits with Contextual Probabilities",
author = "Qiu, Chen-Meng and
Wang, Ze-Hao and
Wang, Deng-Bao and
Yue, Linan and
Zhang, Min-Ling",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.emnlp-main.1592/",
pages = "36198--36215",
ISBN = "979-8-89176-459-0",
abstract = "Token probabilities play a central role in large language models. However, these probabilities often fail to reflect either answer correctness or probability distributions explicitly specified in the context. We attribute this failure to the **Context-Logit Probability Gap**: contextual probabilities are not reliably reflected in the model{'}s next-token logits. We show that post-hoc temperature scaling has a limited effect on addressing this gap, because it rescales logits without correcting erroneous probability rankings. Motivated by this, we propose Bag-of-Tokens (BoT) tuning, a very simple fine-tuning approach that directly calibrates the logits with the probability distribution conveyed by synthetic contexts. More specifically, we construct BoT examples by forming a bag of candidate tokens with an explicitly assigned probability distribution. This distribution is expressed in the context and used as soft supervision to align the model{'}s logit probabilities via KL-divergence minimization. Experiments show that BoT tuning generalizes to LLM-based sampling tasks, such as random-number generation, and improves downstream QA accuracy and calibration. These results suggest that calibrating LLM logits with contextual probabilities provides a lightweight and effective way to enhance their uncertainty awareness."
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<abstract>Token probabilities play a central role in large language models. However, these probabilities often fail to reflect either answer correctness or probability distributions explicitly specified in the context. We attribute this failure to the **Context-Logit Probability Gap**: contextual probabilities are not reliably reflected in the model’s next-token logits. We show that post-hoc temperature scaling has a limited effect on addressing this gap, because it rescales logits without correcting erroneous probability rankings. Motivated by this, we propose Bag-of-Tokens (BoT) tuning, a very simple fine-tuning approach that directly calibrates the logits with the probability distribution conveyed by synthetic contexts. More specifically, we construct BoT examples by forming a bag of candidate tokens with an explicitly assigned probability distribution. This distribution is expressed in the context and used as soft supervision to align the model’s logit probabilities via KL-divergence minimization. Experiments show that BoT tuning generalizes to LLM-based sampling tasks, such as random-number generation, and improves downstream QA accuracy and calibration. These results suggest that calibrating LLM logits with contextual probabilities provides a lightweight and effective way to enhance their uncertainty awareness.</abstract>
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%0 Conference Proceedings
%T Bag-of-Tokens Tuning: Calibrating LLM Logits with Contextual Probabilities
%A Qiu, Chen-Meng
%A Wang, Ze-Hao
%A Wang, Deng-Bao
%A Yue, Linan
%A Zhang, Min-Ling
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-459-0
%F qiu-etal-2026-bag
%X Token probabilities play a central role in large language models. However, these probabilities often fail to reflect either answer correctness or probability distributions explicitly specified in the context. We attribute this failure to the **Context-Logit Probability Gap**: contextual probabilities are not reliably reflected in the model’s next-token logits. We show that post-hoc temperature scaling has a limited effect on addressing this gap, because it rescales logits without correcting erroneous probability rankings. Motivated by this, we propose Bag-of-Tokens (BoT) tuning, a very simple fine-tuning approach that directly calibrates the logits with the probability distribution conveyed by synthetic contexts. More specifically, we construct BoT examples by forming a bag of candidate tokens with an explicitly assigned probability distribution. This distribution is expressed in the context and used as soft supervision to align the model’s logit probabilities via KL-divergence minimization. Experiments show that BoT tuning generalizes to LLM-based sampling tasks, such as random-number generation, and improves downstream QA accuracy and calibration. These results suggest that calibrating LLM logits with contextual probabilities provides a lightweight and effective way to enhance their uncertainty awareness.
%U https://aclanthology.org/2026.emnlp-main.1592/
%P 36198-36215
Markdown (Informal)
[Bag-of-Tokens Tuning: Calibrating LLM Logits with Contextual Probabilities](https://aclanthology.org/2026.emnlp-main.1592/) (Qiu et al., EMNLP 2026)
ACL