AREX-2 Advances Self-Improving Agents via Long-Horizon Reflective Tasks: Scoring 81.8 on MLE-bench and 92.2 on GAIA
Test-time self-improvement—the ability of an agent to iteratively refine solutions during inference—relies on high-fidelity reflection to surpass current proposals and long-horizon execution to maintain coherent multi-round exploration. Researchers from Renmin University of China, Microsoft Research, and USTC introduce AREX-2, establishing that these capabilities are domain-agnostic and learnable from verifiable environments. Synthesizing long-horizon reflective trajectories across machine learning and algorithmic programming, an AREX-2 agent built on Qwen3.8-27B achieves 81.8 on MLE-bench Lite and 70.7 on Frontier-CS, transferring seamlessly to deep research with 84.0 on BrowseComp, 92.2 on GAIA, and 93.8 on DeepSearchQA while monotonically scaling with compute budget.
Key Takeaways
- Identifies reflection and long-horizon execution as domain-agnostic foundations for test-time self-improving agents
- Achieves 81.8 on MLE-bench Lite and 70.7 on Frontier-CS using an AREX-2 Qwen3.8-27B model
- Transfers zero-shot to deep research benchmarks, scoring 92.2 on GAIA, 93.8 on DeepSearchQA, and 84.0 on BrowseComp