Training Sep 2025 · #35 most cited · 139 citations

SimpleTIR: End-to-End Reinforcement Learning for Multi-Turn Tool-Integrated Reasoning

Zhenghai Xue et al.

arXiv:2509.02479

In short

Training LLMs with RL to reason while calling tools over many turns tends to collapse. SimpleTIR traces this to low-probability tokens after tool feedback causing gradient explosions, and fixes it by filtering out trajectories with “void” turns, lifting a 7B model’s AIME24 score from 22 to 50.

Why it matters

A one-idea fix that makes multi-turn tool-using RL trainable.

Read first

The 3 Field Guide ideas this paper leans on.

Starting from scratch? The full route 24 ideas · basics first
  1. Machine Learning ✓ understood

    Building systems that learn patterns from data instead of following hand-written rules, getting better at a task as they see more examples.

  2. Reinforcement Learning · read first ✓ understood

    Learning through interaction with an environment, receiving rewards or penalties to learn optimal behavior policies.

  3. Natural Language Processing ✓ understood

    The field of AI that lets computers read, interpret, translate and generate human language, from spam filters and search to chatbots.

  4. Token ✓ understood

    The basic unit of text that a language model processes, typically representing a word, subword, or character. Tokens are the fundamental building blocks for LLM input and output.

  5. Tokenization ✓ understood

    Splitting text into tokens, usually subword pieces, and mapping each to an integer ID so a language model can process it.

  6. Language Modeling ✓ understood

    Learning probability distributions over sequences of words to predict what comes next.

  7. Dataset ✓ understood

    A collection of data examples used for training, validating, or testing machine learning models.

  8. Training ✓ understood

    The process of fitting a model to data by repeatedly measuring how wrong its outputs are and adjusting its parameters to reduce that error.

  9. Unsupervised Learning ✓ understood

    Learning from unlabeled data to discover hidden patterns, structures, or relationships without explicit target outputs.

  10. Self-Supervised Learning ✓ understood

    Learning representations from unlabeled data by creating supervised tasks from the data itself (masked prediction, contrastive learning).

  11. Pre-training ✓ understood

    Training a model on a large dataset (often self-supervised) before fine-tuning on specific tasks, enabling transfer learning.

  12. Feature ✓ understood

    A single measurable property of an example, such as a house's floor area or how many links an email contains, used as an input to a model.

  13. Neural Network ✓ understood

    A computational model inspired by biological neural networks, consisting of interconnected nodes (neurons) organized in layers that process information through weighted connections.

  14. Deep Learning ✓ understood

    A subset of machine learning that uses neural networks with multiple layers (deep neural networks) to learn hierarchical representations of data.

  15. Representation Learning ✓ understood

    Learning useful features or representations of data automatically, rather than hand-crafting them.

  16. Embedding ✓ understood

    A list of numbers (a vector) that represents a word, sentence, image or other item, learned so that similar items end up close together.

  17. Attention Mechanism ✓ understood

    A technique that lets a neural network weigh every part of its input when producing each output, focusing on the parts most relevant at that step.

  18. Transformer ✓ understood

    A neural network architecture, introduced in 2017, built from stacked self-attention and feed-forward layers; the basis of nearly every modern large language model.

  19. Large Language Model ✓ understood

    A neural network, almost always a transformer, trained on vast amounts of text to predict the next token, which lets it write, answer, summarize and follow instructions.

  20. Tool Use · read first ✓ understood

    LLMs learning to call external tools, APIs, or functions to extend capabilities beyond text generation (calculators, search, code execution).

  21. Loss Function ✓ understood

    A function that scores how wrong a model's prediction is as a single number, which training then works to make as small as possible.

  22. Gradient Descent ✓ understood

    An optimization method that repeatedly moves a model's parameters a small step in the direction that most reduces the loss.

  23. Backpropagation ✓ understood

    The algorithm for computing gradients of the loss with respect to network weights, enabling training through gradient descent.

  24. Exploding Gradient · read first ✓ understood

    A problem where gradients become extremely large during backpropagation, causing unstable training and NaN values.

In the frontier

Rank
#35 of 100
Citations
139
as of Aug 9, 2026
Published
Sep 2025

Topics: RL for reasoning , Agent training and self-evolution , Reasoning methods

Selection: 1kpapers.com by Together AI, most-cited as of Aug 9, 2026

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