What it measures

Embeds multi-step bAbI deductive reasoning chains inside massive PG19 book haystacks from 4k to 10M tokens.

Reading the measurement

Length is a test condition, not a capability score. Locate the relevant evidence, then examine whether the model resolves conflicts and combines details correctly. Keep document extraction, input length and answer grading fixed.

Published evaluation

Published accuracy on the source task and context length. The avg row is the author’s QA1–QA5 average; single tasks, context lengths and this historical v0 snapshot remain separate measures. Missing lengths are omitted. The leaderboard’s newer consolidated result file is not included in this historical extract.

Where this fits in an evaluation suite

A large context window is a capacity specification. Successful retrieval and cross-document reasoning are observed capabilities. Test both at the actual lengths your workflow needs.

Start with a capability hypothesis, then choose a second test with a different failure mode. Keep the checkpoint, reasoning effort, agent tools, sampling policy, and scoring procedure fixed when measuring a training intervention. Record failures and missing outputs in the denominator.

A reproducible comparison

Published accuracy on the source task and context length. The avg row is the author’s QA1–QA5 average; single tasks, context lengths and this historical v0 snapshot remain separate measures. Missing lengths are omitted. The leaderboard’s newer consolidated result file is not included in this historical extract.

Publish the exact run configuration, item coverage, score units, and available uncertainty. If a source supplies only an aggregate or a single run, preserve that limit. A new model name or a rounded score alone does not establish a capability improvement.

PRIMARY EVIDENCE & FURTHER READING

  1. BABILong: Testing the Limits of LLMs with Long Context Reasoning-in-a-Haystack — official v0 leaderboard — published result table ↗

    Kuratov, Yuri, Bulatov, Aydar, Anokhin, Petr, Rodkin, Ivan, Sorokin, Dmitry, Sorokin, Artyom et al. · 2024

    All 7 authors

    Kuratov, Yuri, Bulatov, Aydar, Anokhin, Petr, Rodkin, Ivan, Sorokin, Dmitry, Sorokin, Artyom, Burtsev, Mikhail

Reviewed 2026-10-27. Explanation and interpretation by RLTasks. Benchmark ownership remains with its original authors.