Benchmark Almanac

FlenQA

Phi-4-Reasoning-plus 97.9% leads since April 2025
Dropped

Models answer reasoning questions whose key facts are padded with filler text to different lengths. Accuracy shows how input length affects reasoning.

Phi model cards report only a 3K-token subset, so scores depend on the padding length used.

Released
February 2024
Kind
Reasoning over long documents
Level
Everyday
Scored
Checked automatically
Answers
Multiple choice
Tasks
All public
Last in a launch post
April 2025, dropped after it saturated
Last model added
April 2025

In the authors’ words

This paper explores the impact of extending input lengths on the capabilities of Large Language Models (LLMs). Despite LLMs advancements in recent times, their performance consistency across different input lengths is not well understood. We investigate this aspect by introducing a novel QA reasoning framework, specifically designed to assess the impact of input length. We isolate the effect of input length using multiple versions of the same sample, each being extended with padding of different lengths, types and locations. Our findings show a notable degradation in LLMs' reasoning performance at much shorter input lengths than their technical maximum. We show that the degradation trend appears in every version of our dataset, although at different intensities. Additionally, our study reveals that the traditional metric of next word prediction correlates negatively with performance of LLMs' on our reasoning dataset. We analyse our results and identify failure modes that can serve as useful guides for future research, potentially informing strategies to address the limitations observed in LLMs.

Abstract of Same Task, More Tokens: the Impact of Input Length on the Reasoning Performance of Large Language Models (arXiv:2402.14848, CC0)
2
Models scored in lab cards
2
Launch posts list it, from 1 lab
2
System cards report it, from 1 lab

Phi-4-Reasoning-plus leads with 97.9%

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.

  1. 1 Phi-4-Reasoning-plus 97.9%
  2. 2 Phi-4-reasoning 97.7%

Source: Labs’ model cards

#ModelScoreSettingDateSource
1 Phi-4-Reasoning-plus 97.9% Apr 2025 Lab model card
2 Phi-4-reasoning 97.7% Apr 2025 Lab model card

Number one over time

Lab claims count from the day the card came out, independent runs from the model’s release.

Microsoft
Lab claims Passed 85% in Apr 2025, by Phi-4-Reasoning-plus

Source: Labs’ model cards

Microsoft’s own number for Phi-4-Reasoning-plus passed 85% in April 2025

All the scores we have, one dot each, so a model tested at several settings appears more than once.

Reported by the lab in its model card
0% 20% 40% 60% 80% 100% 2025 Near the ceiling (85%) Phi-4-Reasoning-plus 0% 20% 40% 60% 80% 100% 2025 Near the ceiling (85%) Phi-4-Reasoning-plus

Source: Labs’ model cards

Labs dropped it from launch posts once the best score passed 85%

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.

Microsoft
DateLaunch postScoreAs the post writes it
Apr 30, 2025 Phi-4-reasoning 97.7 FlenQA [3K-token subset]
Apr 30, 2025 Phi-4-Reasoning-plus 97.9 FlenQA [3K-token subset]

2 system cards report it, from 1 lab

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.

DateDocumentScoreAs the document writes itSection
Apr 30, 2025 Phi-4-reasoning technical report 97.7 FlenQA [3K-token subset] (Table 2) Capabilities
Apr 30, 2025 Phi-4-Reasoning-plus technical report 97.9 FlenQA [3K-token subset] (Table 2) Capabilities

More in Long context

All 79 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. Inkling 2 Small 70.6%
  • 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 99.96%
  • 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. Gemini 3.7 Flash 89%
  • 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%