Panorama of Agent V2
1. What is Agent & Harness?
First, the Large Language Model(LLM) is very mature now. Its essence is a prediction model:
- You input a string of token, and it outputs a string of token.
The LLM nowadays can answer our questions but it can not finish a job independently. For example, you can ask LLM how to create a new folder on PC and it can give you an answer. However, the LLM cannot create the folder directly because the only thing it can do is output tokens.
Now we have LLM to describe the workflow of a job. But we need to finish the workflow ourselves. ==Agent== is the software that can resolve problems independently.
==Agent== is usually composed two parts: ==LLM== and ==Harness==.
Agent ≈ LLM-based Policy + Harness
The LLM provides the main reasoning/policy capability, while the Harness provides orchestration, state/context management, tools, environment interaction, execution, and runtime controls. e.g. LLM thought it needs to read a file, then the Harness part will read the file and return the result to LLM.
In Agent, LLM is more likely a role of “Brain”, and the Harness is the “Limb”.
2. Agent’s Pursuit
Agent is designed to solve problem independently. Everything we do now is to improve Agent’s ability of solving problems.
We hope Agent can solve particular problems in daily life and complex problems in specific area like software engineering.
3. Agent Area Panorama
Agent is composed of LLM and Harness.
So it is obviously that we should enhance LLM’s performance in Agent area. And optimize the Harness part. Then we need benchmarks to judge the Agent’s performance.
For this research map, the main research areas are divided into four parts:
- LLM Tuning
- Harness Structure Optimization
- Benchmark-related work
- Multi-agent work
3.1 LLM Tuning
In Agent area, the most popular post-training methods are:
- Imitation Learning (SFT)
- Online RL
- Offline RL
- Preference Learning (DPO)
3.1.1 Imitation Learning (SFT)
ℒSFT = −∑tlog Pθ(tokent ∣ token < t) #### 3.1.1.1 Trajectory SFT
Core Process:
1 | Expert Agent Trajectory |
Trajectory (ReAct) :
1 | task |
Relative papers:
- SWE-Gym (ICML 2025), Rejection Sampling / Self-Improvement
- SWE-Lego (arXiv:2601.01426, 2026)
3.1.1.2 Critical-Step SFT
A trajectory includes many steps, but not all steps are necessary. There’s one way only to SFT the critical steps in trajectories.
- ATLaS — (Findings ACL 2025), only train critical steps
3.1.1.3 Synthetic Trajectory
One problem of SFT is that high-quality training data is few, so there’s a research direction is to compose Synthetic Trajectory.
- SWE-smith, Synthetic Trajectory
3.1.1.4 Distillation
Distillation is to extract ==reasoning trajectories== form different teachers and distill into a student model.
1 | Teacher A |
- Agentic-R1 (EMNLP 2025)
3.1.2 Online RL
3.1.2.1 Reward Design
The reward is a criterion to judge how good a trajectory is.
There are many ways to calculate reward:
1 | Reward |
RLVR (Reinforcement Learning Verifiable Reward) is an important type, because many engineering problems are verifiable.
- SWE-RL (NeurIPS 2025)
- WebAgent-R1 (EMNLP 2025)
Process Reward Model(PRM) is another research roadmap; There are many steps in a trajectory. The traditional reward is trajectory-level, which means that LLM cannot distinguish if one certain step in a trajectory is important.
1 | Step 1 |
- LLM cannot know if step 3 is really important.
1 | Outcome Reward |
- Rewarding Progress (ICLR 2025)
- PURE (NeurIPS 2025)
- ReasonFlux-PRM (NeurIPS 2025)
3.1.2.2 RL Optimization Algorithm
After calculating the reward of a trajectory, we need to update the weights of LLM.
There are three ways to update weights, but the PMD is not commonly used.
1 | Reward |
3.1.2.2.1 GRPO
GRPO has become one of the most widely used policy-optimization methods for reasoning-oriented LLM post-training. A key difference from standard PPO is that GRPO estimates relative advantages from a group of sampled responses instead of maintaining a separate value/critic model.
1 | Question x |
- SWE-RL
3.1.2.2.2 PPO
The core thought of PPO (Proximal Policy Optimization) is:
- Need to make LLM more inclined to generate high-reward responses, while ensuring that a single update does not deviate too far from the original model.
1 | Question x |
3.1.3 Offline RL
- OREO (ACL 2025): Offline Reinforcement Learning for LLM Multi-step Reasoning
- Reward-Weighted Fine-Tuning (NeurIPS 2025): Offline RL by Reward-Weighted Fine-Tuning for Conversation Optimization
3.1.4 Preference Learning (DPO)
DPO (Direct Preference Optimization) is widely used in LLM post-training, but in Agent-specific post-training it is generally less dominant than SFT and online RL.
SFT makes LLM realize what is right answer while Preference Learning just tells LLM: A is better than B.
1 | Task |
Train:
1 | πθ(A|x) ↑ |
Basic DPO process:
1 | Prompt |
The traditional DPO compare different trajectories. Nowadays the tendency is to research which certain step makes trajectory better.
1 | Trajectory-level |
- HPL (ICLR 2026): Solving the Granularity Mismatch: Hierarchical Preference Learning for Long-Horizon LLM Agents
- Online DPO (ICLR 2025)
- SDPO (ACL 2025)
3.2 Harness Structure
For this research map, the Harness is organized into seven engineering-oriented layers. This is a practical taxonomy rather than a universally accepted academic standard, and the layers can overlap in real systems.
| Part | Abstruct | Description |
|---|---|---|
| Orchestration Loop / Planning / ReAct / Reflection / Verification |
Control | How should the agent decide what to do? |
| Context & Memory Context Management / Retrieval / Compression / Memory |
State | What should the agent remember? |
| Tools & Actions Tool Calling / Discovery / Selection / Code / Browser / Computer |
Action | What can the agent do? |
| ACI & Environment State / Action Space / Observation / Error / Feedback |
Interface | What state, observations, actions, errors, and feedback does the environment expose to the agent? |
| Skills & Composition Skills / Workflow / Subagents / Agent-as-a-Tool |
Capability | How can reusable capabilities and workflows be represented, retrieved, composed, and reused? |
| Protocol & Interoperability MCP / A2A / Agent API / Session Protocol |
Interoperability | How do agents/tools/services communicate? |
| Runtime & Safety Sandbox / Execution / Permission / Guardrail / Reliability / Observability / Cost |
Runtime & Governance | Where and how are actions executed? How do we keep agents safe, reliable, observable, recoverable, and economical? |
1 | Agent |
3.2.1 Orchestration / Control
Q: How should the Agent decide what to do?
1 | Orchestration |
Earlier Agent(Classic ReAct):
1 | LLM → Tool → LLM → Tool |
Nowadays Agent:
1 | Plan → Act → Verify → Reflect → Re-plan → Act |
From simple ReAct Loop to a Loop with planning / verification / recovery.
PlanGEN (EMNLP 2025): This work combines
planninganditerative verificationReflAct (EMNLP 2025): The traditional ReAct sturcure will accumulate little errors which will make agent drift from correct path.(ALFWorld + 27.7% than ReAct)
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↕
Goal State
↓
Reflection
↓
ActionMetagent-P (ACL 2025)
3.2.2 Context & Memory / State
Q: What should the Agent know at the current moment, and what past information should be retained ?
1 | Orchestration |
The Context & Memory is not just ‘Chat Log’. It store the Agent State.
1 | Current Context |
The ==tradition memory system==:
1 | Memory |
Nowadays:
1 | Agent decides: |
Memory Management will be considered into Agent Policy.
Memory OS of AI Agent, (EMNLP 2025)
This work design the Memory System like operating system hierarchy.
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Mid-term
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Long-termCoarse-to-Fine Grounded Memory, (EMNLP 2025)
This work use memory to replan. Memory is used to store useful things.
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↓
Grounded Memory
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Current Situation
↓
PlanningAgentic Memory, ACL 2026
Memory-R1,ACL 2026
One problem:
How Memory Management Impacts LLM Agents, ACL 2026:
The agent will clearly exhibit “experience-following”: after retrieving historical experience from similar tasks, it is easy to reproduce similar behaviors. So if there exists wrong memory, the Agent are inclined to repeat the wrong operations.
3.2.3 Tools & Actions / Action
What can Agent do ?
The tradition actions system is simply call tools like:
1 | Search |
The new tendency of actions area is:
1 | Tool Discovery |
LLM Agents Making Agent Tools,ACL 2025
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↓
Agent
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Install dependencies
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Generate tool
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Execute
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Debug / Self-correctThis paper makes Agent generate create tools itself.
Adaptive Tool Use,ACL 2025
More tools do not necessarily mean a better Agent. If one tool frequently returns errors, the Agent should realize that.
ToolScope,ACL 2026
In large tool ecosystem, there exists a problem:
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Repeated Tools
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Tedious Schema
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Trouble ChoosingSolution:
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Tool Retrieval
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Context-aware Filtering
3.2.4 ACI & Environment / Interface
This part is to solve the problem: What form should the external world take for the agent, and how should the agent act upon it?
A common API-agent interface takes a form like:
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search(query)
A computer-use agent instead exposes a human-like interaction loop:
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↓
LLM
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click(x,y)
↓
Screenshot
↓
...
Advantage: Developer need no more to design tools for each job.
OS Agents Survey,ACL 2025:
The paper defines OS Agent that interact with:
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CLI
Web
Mobile
DesktopOSWorld-Human, ICML 2025:
To finish a certain task, the Agent takes more steps/operations than human. This work
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↓
Can you finish?
+
Can you finish efficiently?
3.2.5 Skills & Composition / Capability
How can we extract complex, repeatable capabilities from a specific agent and turn them into reusable, composable capabilities?
1 | Tool = an executable capability or interface for an action |
1 | Tools → Atomic Capability |
Tendency: Skill are changing to software artifact from prompt.
The traditional Skill is a text:
1 | To finish ... task, you should: |
It’s a stable text describing a fixed workflow.
Agent Skills,Anthropic 2025
Skill is no more a huge text file. It’s new structure:
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├── instructions
├── scripts
└── resourcese.g:
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├── SKILL.md
├── scripts/
│ ├── extract_table.py
│ ├── clean_data.py
│ └── validate.py
└── resources/
├── excel_template.xlsx
└── examples/There’s a small Skill metadata like tool definitions will be read by Agent when system starts:
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Name:
pdf-to-excel
Description:
Extract structured tables from PDFs and produce validated Excel files.When handling a certain task:
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Skill Retrieval
↓
Load Relative Skill, e.g. pdf-to-excel/SKILL.mdIn Skill.md, there may exists content like:
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Run:
python scripts/extract_table.py report.pdf
...In fact the scripts are tools for skills.
GitHub - anthropics/skills: Public repository for Agent Skills · GitHub
SkillWeaver, arXiv:2504.07079
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↓
Agent Exploration
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Successful Trajectory
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Skill Discovery
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Skill Synthesis
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Skill Practice / Debugging
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Reusable Skill API
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Skill Library
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Future TasksSkillRL (arXiv:2602.08234)
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Skill Distillation
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Hierarchical SkillBank
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Retrieval
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RL Training
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Policy Improvement
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New Experience
↓
SkillBank EvolutionSkillCraft, (arXiv:2603.00718)
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Learn Skill
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Task B
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Reuse Skill
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Task C
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Reuse / Compose SkillGenerative Skill Composition for LLM Agents, (arXiv:2606.32025)
How to compose skills.
Agent Skills for Large Language Models: Architecture, Acquisition, Security, and the Path Forward, (arXiv:2602.12430)
3.2.6 Protocol & Interoperability / Interoperability
Solve the problems of communication between Agents, Tools, Data Source and Services.
MCP (Model Context Protocol):
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↕
Tools / Data / ServicesA2A (Agent to Agent):
Different Agents should have the capability to work together.
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Agent A ↔ Agent B
3.2.7 Runtime & Safety —— Runtime & Governance
Make the Agent actually run in a controlled, secure, observable, and recoverable environment.
Traditional safety check:
1 | Prompt |
Agent workflow:
1 | Prompt |
So we should check safety of not only prompt and output but also Action, Tool Call, State Transition and Permission.
Task Shield,ACL 2025
Does this Action is really relative to User’s task ?
IPIGuard,EMNLP 2025
Create a
Tool Dependency Graph, and limit the tool call by the dependency graph.
3.2.8 Conclusion
| Field | 2025 | Tendency in 2026 |
|---|---|---|
| Orchestration | ReAct、Planning、Reflection | Adaptive / verified / long-horizon control |
| Context & Memory | RAG、hierarchical memory、context compression | Agentic memory、learned memory management |
| Tools & Actions | Tool calling、tool selection | Tool discovery、tool management、tool creation、computer use |
| ACI & Environment | Browser / GUI agents | Efficient action spaces、long-horizon computer interaction、安全 ACI |
| Skills & Composition | Skills、workflows、multi-agent | Reusable capability、skill lifecycle、agent composition |
| Protocol & Interoperability | MCP、A2A | large ecosystem、discovery、identity、security、task protocols |
| Runtime & Safety | Sandbox、guardrails、tracing | Durable runtime、containment、permission、agent security、cost/reliability |
3.3 Benchmark
3.3.1 What Does an Agent Benchmark Evaluate?
Agent benchmarks evaluate more than final-answer correctness. Depending on the benchmark, they may measure task success, long-horizon execution, tool use, environment interaction, efficiency, reliability, safety, and generalization.
1 | Agent Evaluation |
3.3.2 Popular Categories
| Category | What it Evaluates | Representative Benchmarks | Typical Agent Capability |
|---|---|---|---|
| Generalist Agent | General-purpose agents that combine reasoning, search, tools, files, and multimodal capabilities | GAIA | General reasoning, tool use, information gathering, multi-step problem solving |
| Long-Horizon / Real-World Agent | Agents performing complex, multi-step tasks in realistic environments | TheAgentCompany, AgencyBench | Planning, sustained interaction, task decomposition, long-horizon execution |
| Computer-Use Agent | Agents operating computers through GUI, applications, filesystem, and terminal | OSWorld, OSWorld-Human | GUI grounding, computer control, application usage, visual interaction |
| Web / Browser Agent | Agents interacting with websites and browser-based environments | WebArena, Mind2Web | Web navigation, search, clicking, form filling, browser interaction |
| Software Engineering Agent | Agents solving real-world software engineering tasks in repositories | SWE-bench, SWE-bench Verified | Code understanding, debugging, code editing, testing, repository-level reasoning |
| Tool-Using Agent | Agents that select, invoke, and coordinate external tools/APIs | BFCL, τ-bench / τ²-bench | Tool selection, function calling, argument generation, multi-step tool use |
| Deep Research / Research Agent | Agents conducting open-ended research over external information sources | BrowseComp, BrowseComp-Plus, MLR-Bench | Web search, information synthesis, source verification, long-horizon research |
| Multi-Agent | Multiple agents coordinating to solve tasks collaboratively | MultiAgentBench, AgentVerse-related benchmarks | Communication, coordination, delegation, negotiation, collaboration |
| Agent Safety / Security | Agents operating under safety, permission, security, and adversarial constraints | Agent safety / tool-use security benchmarks | Policy compliance, permission management, robustness, safe tool use |
| Classic Agent Environments | Foundational controlled environments for interactive agent research | ALFWorld, WebShop, Mind2Web | Planning, instruction following, environment interaction, action execution |
| Benchmark Methodology | Reliability and validity of agent evaluation itself | BrowseComp-Plus and related benchmark methodology work | Contamination resistance, reproducibility, verifier quality, efficiency, cost, generalization |
3.3.2.1 Generalist Agent Benchmark
Generalist benchmarks evaluate whether an agent can combine reasoning, tool use, information gathering, and multi-step execution across heterogeneous tasks. ==GAIA== is a representative benchmark in this category.
The agent workflow nowadays can look like:
1 | Goal |
Traditional benchmarks often judge if the final answer is correct.
This research direction is about:
1 | Can the Agent still complete the task after taking dozens, hundreds, or even thousands of actions? |
3.3.2.2 Long-Horizon / Real-World Agent Benchmark
These benchmarks emphasize sustained execution over many interacting steps, often across realistic workplace or application environments.
TheAgentCompany, NeurIPS 2025
This benchmark builds a company system:
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│
├── Browser
├── Code repository
├── Terminal
├── Internal websites
├── Communication
└── CoworkersAgencyBench, ACL 2026
3.3.2.3 Computer-Use / GUI Agent Benchmark
1 | Can an Agent really operate a computer instead of merely describing the operations? |
OSWorld, NeurIPS 2024.
The most important Computer-Use Benchmark.
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│
├── Desktop OS Environment
├── Browser
├── Office Applications
├── File System
├── Terminal
└── Desktop ApplicationsOSWorld-Human, ICML 2025 Workshop on Computer-Use Agents
Calculate efficiency of Agent.
Even when they successfully complete the task, top agents still require 1.4–2.7× as many steps as humans.
OSWorld 2.0
CRAB, ACL 2025
Cross-Environment Agent Benchmark for Multimodal Language Model
Thought: Benchmark should not be bound by certain environment.
3.3.2.4 Tool Use / Function Calling / MCP Benchmark
Tools Evaluation Process:
1 | Function Calling |
BFCL, ICML 2025
It judges:
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Multiple functions
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Parallel calls
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Multi-turn
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Memory
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Dynamic decision making
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Long-horizon agentic behaviorToolSandbox, NAACL 2025 Findings
τ-bench, ICLR 2025
MCP-Bench, ICLR 2026
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Tool Selection
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Parameter Control
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Multi-hop Planning
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Cross-tool Coordination
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Task Completion
3.3.2.5 Software Engineering Agent Benchmark
SWE-bench, ICLR 2024 Oral
SWE-bench Multimodal, ICLR 2025
SWE-Bench Pro, ICLR 2026 submission.
For Long-Horizon software engineering.
There’s a problem: ==Contamination==.
The paper finds that some models’ performance on SWE-bench Verified may be affected by training data contamination:
Does SWE-Bench-Verified Test Agent Ability or Model Memory?
3.3.2.6 Web / Browser Agent Benchmark
The core of Web Agent is not ‘Search’ but:
The Agent observes webpages, plans, clicks, types, navigates, calls APIs, and ultimately completes tasks in real-world web environments.
Classic workflow:
1 | User Goal |
- WebArena, ACL 2024
- TurkingBench, NAACL 2025
- X-WebAgentBench, ACL 2025 Findings
3.3.2.7 Deep Research / Research Agent Benchmark
Normal Web Research:
1 | Web Agent |
Deep Research:
1 | Research Question |
BrowseComp
BrowseComp-Plus, ACL 2026
MLR-Bench, NeurIPS 2025:
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Deep Research
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Scientific Research AgentCan AI do research itself?
3.3.2.8 Multi-Agent Benchmark
Multi-agent benchmarks evaluate coordination, communication, task decomposition, role assignment, negotiation, and collaborative problem solving among multiple agents. This is a distinct evaluation axis from single-agent capability.
3.3.2.9 Agent Safety / Security Benchmark
Agent safety benchmarks evaluate whether agents remain within task, permission, and security constraints while interacting with tools, external data, and stateful environments. Important dimensions include prompt injection, unsafe tool use, excessive permissions, policy violations, and recovery from adversarial conditions.
3.3.3 Benchmark Methodology
Benchmark design itself is an important research direction. A useful benchmark should measure the intended capability without being dominated by contamination, brittle verifiers, uncontrolled environment changes, or hidden implementation details.
Important questions include:
1 | Benchmark Quality |
BrowseComp-Plus is a representative example of this direction, emphasizing controlled and reproducible evaluation for deep-research agents.
3.3.4 Popular Benchmarks
3.3.4.1 SWE-bench / SWE-bench Verified
3.3.4.2 GAIA
3.3.4.3 WebArena
3.3.4.4 OSWorld Verified / OSWorld 2.0
3.3.4.5 AgentBench
AgentBench is a multi-environment benchmark suite, rather than a single environment-specific benchmark. It includes:
1 | AgentBench |
Classic Agent Environments
ALFWorld, WebShop, and Mind2Web have an important historical role in LLM-agent research and should not be treated as merely implementation details of AgentBench. They are independently used environments/benchmarks that also appear within the AgentBench suite.
- ALFWorld — interactive household tasks in a text-based embodied environment.
- WebShop — simulated e-commerce tasks involving search, browsing, product selection, and purchase.
- Mind2Web — web-agent tasks grounded in real-world websites and interaction trajectories.
This distinction avoids mixing a benchmark suite (AgentBench) with individual environments (ALFWorld/WebShop/Mind2Web) at the same conceptual level.