mlsanityData to 7 Oct 2026

Hindsight Credit Assignment for Long-Horizon LLM Agents

arXiv 2603.08754 ↗First posted 7 Mar 2026cs.LG cs.AIcited by 51

On the map: LLM agents and tool use → Reinforcement learning for LLM agents

Abstract (arXiv)

Large Language Model (LLM) agents often face significant credit assignment challenges in long-horizon, multi-step tasks due to sparse rewards. Existing value-free methods, such as Group Relative Policy Optimization (GRPO), encounter two fundamental bottlenecks: inaccurate step-level Q-value estimation and misaligned value baselines for intermediate states. To address these limitations, we introduce HCAPO, the first framework to integrate hindsight credit assignment into LLM agents. HCAPO leverages the LLM itself as a post-hoc critic to refine step-level Q-values through hindsight reasoning. Furthermore, HCAPO's multi-scale advantage mechanism effectively supplements the inaccurate value baselines at critical decision states. Evaluations across three challenging benchmarks, including WebShop and ALFWorld, demonstrate that HCAPO consistently outperforms state-of-the-art RL methods. Notably, HCAPO achieves a 7.7% improvement in success rate on WebShop and a 13.8% on ALFWorld over GRPO using the Qwen2.5-7B-Instruct model. These results indicate that HCAPO significantly enhances exploration efficiency, promotes concise decision-making, and ensures scalability in complex, long-horizon tasks.

Key facts. Cited by 51 papers in the map (data through 7 Oct 2026). Placed in Reinforcement learning for LLM agents, one of 16 directions in LLM agents and tool use. Builds on 41 of its 51 references that are in the map. First posted on arXiv 7 Mar 2026.

Builds on

41 of 51 references.

Closest ancestors · 8

Same direction, newest first

  1. 2025AgentPRM: Process Reward Models for LLM Agents via Step-Wise Promise and Progress11 Nov
  2. 2025SALT: Step-level Advantage Assignment for Long-horizon Agents via Trajectory Graph22 Oct
  3. 2025Agentic Reinforcement Learning with Implicit Step Rewards23 Sep
  4. 2025Harnessing Uncertainty: Entropy-Modulated Policy Gradients for Long-Horizon LLM Agents11 Sep
  5. 2025Agentic Reinforced Policy Optimization26 Jul
  6. 2025Group-in-Group Policy Optimization for LLM Agent Training16 May
  7. 2024ArCHer: Training Language Model Agents via Hierarchical Multi-Turn RL29 Feb
  8. 2023Reflexion: Language Agents with Verbal Reinforcement Learning20 Mar

Other references · 33

  1. 2023GPT-4 Technical Reportcited by 18,132
  2. 2022Training language models to follow instructions with human feedbackcited by 15,712
  3. 2017Proximal Policy Optimization Algorithmscited by 14,441
  4. 2024DeepSeekMath: Pushing the Limits of Mathematical Reasoning in Open Language Modelscited by 8,851
  5. 2022ReAct: Synergizing Reasoning and Acting in Language Modelscited by 8,355
  6. 2023Direct Preference Optimization: Your Language Model is Secretly a Reward Modelcited by 7,916
  7. 2024Qwen2.5 Technical Reportcited by 4,713
  8. 2023Toolformer: Language Models Can Teach Themselves to Use Toolscited by 4,072
  9. 2018HotpotQA: A Dataset for Diverse, Explainable Multi-hop Question Answeringcited by 3,686
  10. 2023Let's Verify Step by Stepcited by 3,598
  11. 2017TriviaQA: A Large Scale Distantly Supervised Challenge Dataset for Reading Comprehensioncited by 2,895
  12. 2025DAPO: An Open-Source LLM Reinforcement Learning System at Scalecited by 2,678
21 more
  1. 2020Learning to summarize from human feedbackcited by 2,562
  2. 2019Fine-Tuning Language Models from Human Preferencescited by 2,124
  3. 2015High-Dimensional Continuous Control Using Generalized Advantage Estimationcited by 1,916
  4. 2025Search-R1: Training LLMs to Reason and Leverage Search Engines with Reinforcement Learningcited by 1,371
  5. 2025Understanding R1-Zero-Like Training: A Critical Perspectivecited by 1,276
  6. 2020Constructing A Multi-hop QA Dataset for Comprehensive Evaluation of Reasoning Stepscited by 1,259
  7. 2022WebShop: Towards Scalable Real-World Web Interaction with Grounded Language Agentscited by 1,197
  8. 2020ALFWorld: Aligning Text and Embodied Environments for Interactive Learningcited by 1,143
  9. 2022When Not to Trust Language Models: Investigating Effectiveness of Parametric and Non-Parametric Memoriescited by 1,103
  10. 2017Hindsight Experience Replaycited by 1,096
  11. 2022Measuring and Narrowing the Compositionality Gap in Language Modelscited by 1,054
  12. 2021MuSiQue: Multihop Questions via Single-hop Question Compositioncited by 893
  13. 2024TravelPlanner: A Benchmark for Real-World Planning with Language Agentscited by 385
  14. 2023A Real-World WebAgent with Planning, Long Context Understanding, and Program Synthesiscited by 350
  15. 2024CodeAgent: Enhancing Code Generation with Tool-Integrated Agent Systems for Real-World Repo-level Coding Challengescited by 278
  16. 2025ZeroSearch: Incentivize the Search Capability of LLMs without Searchingcited by 203
  17. 2023ReMax: A Simple, Effective, and Efficient Reinforcement Learning Method for Aligning Large Language Modelscited by 184
  18. 2024UFO: A UI-Focused Agent for Windows OS Interactioncited by 147
  19. 2025CPPO: Accelerating the Training of Group Relative Policy Optimization-Based Reasoning Modelscited by 93
  20. 2019Hindsight Credit Assignmentcited by 74
  21. 2025RLVMR: Reinforcement Learning with Verifiable Meta-Reasoning Rewards for Robust Long-Horizon Agentscited by 56

Built on by

Cited by year (2026 to 7 Oct)

Citing papers per year: 2026: 51.

51 papers.

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  1. 2026From Reasoning to Agentic: Credit Assignment in Reinforcement Learning for Large Language Modelscited by 19
  2. 2026TRACE: Turn-level Reward Assignment via Credit Estimation for Long-Horizon Agentscited by 11
  3. 2026Adaptive Teacher Exposure for Self-Distillation in LLM Reasoningcited by 9
  4. 2026Where Hindsight Credit Can Reside: A Signed-Capacity View of Token Updates in RLVRcited by 8
  5. 2026Shepherd: Enabling Programmable Meta-Agents via Reversible Agentic Execution Tracescited by 8
  6. 2026HINT-SD: Targeted Hindsight Self-Distillation for Long-Horizon Agentscited by 7
  7. 2026SkillFlow: Flow-Driven Recursive Skill Evolution for Agentic Orchestrationcited by 6
  8. 2026SIRI: Self-Internalizing Reinforcement Learning with Intrinsic Skills for LLM Agent Trainingcited by 5
  9. 2026Credit Without Ground Truth: Auditing Step-Level Credit Assignment in LLM Agents Against Executed Replaycited by 5
  10. 2026When Denser Credit Is Not Enough: Evidence-Calibrated Policy Optimization for Long-Horizon LLM Agent Trainingcited by 4
  11. 2026HiMPO: Hindsight-Informed Memory Policy Optimization for Less-Entangled Credit in Long-Horizon Agentscited by 4
  12. 2026BiPACE: Bisimulation-Guided Policy Optimization with Action Counterfactual Estimation for LLM Agentscited by 4
38 more
  1. 2026Group-Reflective Self-Distillation for Agentic Reinforcement Learningcited by 4
  2. 2026TRACER: Verifiable Generative Provenance for Multimodal Tool-Using Agentscited by 3
  3. 2026Organize then Retrieve: Hierarchical Memory Navigation for Efficient Agentscited by 3
  4. 2026ECHO: Prune To Act, Trace To Learn With Selective Turn Memory In Agentic RLcited by 3
  5. 2026AttriMem: Attribution-Guided Process Feedback for Agent Memory Constructioncited by 3
  6. 2026PiCA: Pivot-Based Credit Assignment for Search Agentic Reinforcement Learningcited by 2
  7. 2026BiCAA: Bidirectional Credit Assignment for Search-Augmented Agentcited by 2
  8. 2026TRCA: Transition-wise Rubric Credit Assignment for Long-horizon LLM Agentscited by 2
  9. 2026Co-Evolution of Policy and Internal Reward for Language Agentscited by 1
  10. 2026COSAC: Counterfactual Credit Assignment in Sequential Cooperative Teamscited by 1
  11. 2026SaliMory: Orchestrating Cognitive Memory for Conversational Agentscited by 1
  12. 2026TAPO: Tool-Aware Policy Optimization via Credit Transfer for Multimodal Search Agentscited by 1
  13. 2026Semantic Consistency Policy Optimization for Reinforcement Learning of LLM Agentscited by 1
  14. 2026Crayotter: Learning Long-Horizon Video Editing Agents via Group-Relative Preference Backpropagationcited by 1
  15. 2026Learning from Environmental Feedback: Credit Assignment across Multiple Timescales for Agentic Reinforcement Learningcited by 1
  16. 2026FailForge: Distilling Procedural Competence from Persistent Failures into Code Agentscited by 1
  17. 2026IAPO: Influence-Aware Policy Optimization for Credit Assignment in Multi-Turn Service Agentscited by 1
  18. 2026DRACO: Fine-Grained Credit Assignment with Dynamic Rubrics for Long-Horizon Agent Trainingcited by 1
  19. 2026What Does Multi-Harness RL Learn? Credit Assignment and Portability in Coding Agentscited by 1
  20. 2026DeliveryGym: An RL Environment for Long-Horizon Embodied Agent Planning with Adaptive Curriculumcited by 1
  21. 2026Multi-Modal Agents for Power Distribution Defect Detection: An Evaluation of Foundation Modelscited by 0
  22. 2026From Agent Failures to Text Policies: What Works and What Breakscited by 0
  23. 2026CoRT: Counterfactual Replay for Token-Level Rubric-Guided Policy Optimizationcited by 0
  24. 2026VICT: Verifier-Instrumented Credit Tracing for Long-Horizon LLM Agent Reinforcement Learningcited by 0
  25. 2026MAGMA-GEN: Validated Recovery Supervision from Ambiguous Failures via Counterfactual Re-Executioncited by 0
  26. 2026ProCredit: From Outcome Rewards to Progress Credit in Agentic Reinforcement Learningcited by 0
  27. 2026Back to the Definition: Estimating Step-Level Advantages via Trajectory Graphs for Agentic Reinforcement Learningcited by 0
  28. 2026From Self-Distillation to Self-Practice: Privileged Information for Multi-Turn Agentscited by 0
  29. 2026Beyond Timestamps: Decision-Aligned On-Policy Distillation for Long-Horizon Agentscited by 0
  30. 2026R2 Flow: Recursive Self-Improvement via Recursive Skill Evolutioncited by 0
  31. 2026Counterfactual Rollout Replay: Forkable Environments as Free Process Rewards for Software Engineering Agentscited by 0
  32. 2026Dr.Credit: Rubric-Grounded Process Credit Assignment for Deep Research Agentscited by 0
  33. 2026SIPO: Selective-Inference Policy Optimization for Tree-Structured Agentic RLcited by 0
  34. 2026UniOPSD: Unifying Outcome and Hindsight Feedback for Agentic Reinforcement Learningcited by 0
  35. 2026Cross-Rollout Bellman Closure for Long-Horizon Agentic Reinforcement Learningcited by 0
  36. 2026GraphHCA: Closed-Form Hindsight Credit Assignment for Long-Horizon LLM Agentscited by 0
  37. 2026MLToolBench: Learning Tool-Augmented Agents for Machine Learning Developmentcited by 0
  38. 2026World Potential Model: Pretrained World Knowledge as Progress Potentialscited by 0

50 most cited of 51 All 51 (JSON)

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  1. 2025Speaking the Language of Teamwork: LLM-Guided Credit Assignment in Multi-Agent Reinforcement Learning
  2. 2024VinePPO: Refining Credit Assignment in RL Training of LLMs
  3. 2026Unifying Temporal and Structural Credit Assignment in LLM-Based Multi-Agent Prompt Optimization
  4. 2026Enhancing LLM-based Search Agents via Contribution Weighted Group Relative Policy Optimization
  5. 2024Latent Reward: LLM-Empowered Credit Assignment in Episodic Reinforcement Learning
  6. 2025CAPO: Towards Enhancing LLM Reasoning through Generative Credit Assignment
  7. 2026From Outcomes to Actions: Leveraging Hindsight for Long-Horizon Language Agent Training
  8. 2024Enhancing Decision-Making for LLM Agents via Step-Level Q-Value Models