MTOB
Models learn to translate between English and Kalamang, a language with under 200 speakers, from one grammar book. Scored by chrF.
Cards report half-book or full-book context and either translation direction, so scores vary by setup.
In the authors’ words
Large language models (LLMs) can perform impressive feats with in-context learning or lightweight finetuning. It is natural to wonder how well these models adapt to genuinely new tasks, but how does one find tasks that are unseen in internet-scale training sets? We turn to a field that is explicitly motivated and bottlenecked by a scarcity of web data: low-resource languages. In this paper, we introduce MTOB (Machine Translation from One Book), a benchmark for learning to translate between English and Kalamang – a language with less than 200 speakers and therefore virtually no presence on the web – using several hundred pages of field linguistics reference materials. This task framing is novel in that it asks a model to learn a language from a single human-readable book of grammar explanations, rather than a large mined corpus of in-domain data, more akin to L2 learning than L1 acquisition. We demonstrate that baselines using current LLMs are promising but fall short of human performance, achieving 44.7 chrF on Kalamang to English translation and 45.8 chrF on English to Kalamang translation, compared to 51.6 and 57.0 chrF by a human who learned Kalamang from the same reference materials. We hope that MTOB will help measure LLM capabilities along a new dimension, and that the methods developed to solve it could help expand access to language technology for underserved communities by leveraging qualitatively different kinds of data than traditional machine translation.
- Level
- Expert Specialists with years of training, often over hours of work
- Scored
- Checked automatically A program checks the result against an answer key, unit tests or the expected final state.
- Answers
- Open-ended Free-form text, documents, designs or media judged as a whole.
Llama 4 Maverick leads with 54.0 among models released by Apr 2025
Best score per model as labs report them in their own cards. Labs pick their own settings, so these compare less cleanly than independent runs.
The newest model with a score here came out in Apr 2025, and nobody has reported a newer one. Among the 20 highest-ranked models on the capability index, these have no score yet:
- GPT-6 Astra
- Claude Opus 5.5
- GPT-6.1 Terra
- GPT-6.1 Sol
- and 16 more
- 1
Llama 4 Maverick 54.0
- 2
MiniMax-Text-01 51.7
- 3
Llama 4 Scout 42.2
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | | 54.0 | Apr 2025 | Model card | |
| 2 | | 51.7 | Jan 2025 | Model card | |
| 3 | | 42.2 | Apr 2025 | Model card |
2 models have held number one since its release in Sep 2023
Lab claims count from the day the card came out, independent runs from the model’s release.
Scores over time
All the scores we have, one dot each, so a model tested at several settings appears more than once.
No launch post has listed it since Apr 2025
Launch posts from every lab that has listed it, one tick per post. Tall colored ticks include it, and short gray ones leave it out.
| Date | Launch post | Score | As the post writes it |
|---|---|---|---|
| 5 Apr 2025 | 42.2 | Best of MTOB (half book) eng->kgv/kgv->eng = 42.2/36.6 / MTOB (full book) = 39.7/36.3 | |
| 5 Apr 2025 | 54 | Best of MTOB (half book) eng->kgv/kgv->eng = 54.0/46.4 / MTOB (full book) eng->kgv/kgv->eng = 50.8/46.7 | |
| 15 Jan 2025 | 51.7 | MTOB eng → kalam (ChrF), half book |
5 system cards report it, from 3 labs
Besides launch posts, we read the system cards, model cards and technical reports labs publish with a release. They report far more, including safety and frontier-risk tests.
| Date | Document | Score | As the document writes it | Section |
|---|---|---|---|---|
| 24 Jul 2026 | | MTOB chrF, two directions and two context sizes with no overall score: eng to kgv half book 52.9, full book 54.3; kgv to eng half book 48.6, full book 46.2 (Table 9) | Capabilities | |
| 24 Jul 2026 | | MTOB chrF, two directions and two context sizes with no overall score: eng to kgv half book 50.0, full book 48.9; kgv to eng half book 45.0, full book 42.7 (Table 9) | Capabilities | |
| 5 Apr 2025 | | 42.2 | MTOB (half book) eng->kgv, chrF, instruction tuned. Half book eng->kgv/kgv->eng = 42.2/36.6, full book = 39.7/36.3 (Instruction tuned models table) | Capabilities |
| 5 Apr 2025 | | 54 | MTOB (half book) eng->kgv, chrF, instruction tuned. Half book eng->kgv/kgv->eng = 54.0/46.4, full book = 50.8/46.7 (Instruction tuned models table) | Capabilities |
| 14 Jan 2025 | | 51.7 | MTOB eng → kalam (ChrF), half book (Table 11). Full book 51.60. kalam → eng (BLEURT) half book 57.10 | Capabilities |
More in Long context
- MRCR v2 In use Multi-round coreference: retrieve the n-th of several similar requests hidden in a long synthetic conversation, up to 1M tokens.
Muse Spark 1.3 98.5%
- LongBench v2 In use 503 multiple-choice questions over 8K-2M-word contexts (QA, dialogue, code repos, structured data). Accuracy. Beam 1.0 66.9%
- GraphWalks In use A graph is given as an edge list in long context. The model answers BFS or parent queries, scored by F1. Claude Fable 5 100%
- OpenAI MRCR v2 In use Models read a long synthetic chat that hides 2, 4 or 8 identical writing requests and must reproduce the response to the i-th one. Scored by mean string match ratio per context bin.
K-EXAONE 2.0 94.4%
- CL-bench In use Model must learn new knowledge from a supplied long context (rules, procedures, data) and solve tasks. Strict LLM-verified rubrics. GPT-5.4 27.9%
- AA-LCR 1.1 In use Models answer 100 questions that need reasoning across sets of real documents of about 100K tokens. An LLM equality checker with a fixed system prompt compares each answer with the key.
Step 5 Preview 88.3%