LLM-based Intelligent Agents

• LLM-based intelligent agents are modular systems that integrate perception, reasoning, memory, and execution to autonomously perform complex tasks.
• They utilize advanced planning techniques, such as chain-of-thought and hierarchical decomposition, to achieve reliable multi-step reasoning.
• They employ robust multi-agent frameworks and adaptive memory systems to excel in diverse applications like trading, legal reasoning, manufacturing, and scheduling.

LLM-based intelligent agents are autonomous or semi-autonomous software entities that leverage LLMs as the core of their reasoning, planning, memory, and action modules to achieve complex tasks via natural language interaction and tool-use. These agents represent a significant evolution beyond traditional LLMs, integrating closed-loop environmental perception, dynamic reasoning, adaptive memory, and robust execution mechanisms—often organized in modular, multi-agent, or hierarchical frameworks—to approach human-level flexibility and competence in a growing range of real-world and simulated applications.

1. Architectural Foundations: Components and Integration

LLM-based intelligent agents are architected as modular systems unifying four essential subsystems:

1. Perception System: Translates environment signals—text, images, sensor data, UI structures—into LLM-ingestible representations. Techniques include direct text ingestion, multimodal encoders for vision or audio, structured parsing (e.g., HTML, accessibility trees), and tool-augmented wrappers for data retrieval or code execution. Multimodal integration is implemented via modality encoders, projectors, and cross-modal alignment with the LLM’s latent space (Castrillo et al., 10 Oct 2025).
2. Reasoning System: Implements planning, stepwise decomposition (e.g., Chain-of-Thought, Tree-of-Thought), multi-path sampling (self-consistency), and reflection loops for decision quality. Dynamic decomposition—using methods like DPPM (Decompose, Plan in Parallel, Merge)—enables incremental adjustment in non-stationary environments, while interleaved planning/execution (e.g., ReAct, GoalAct frameworks) supports robust failure recovery (Chen et al., 23 Apr 2025, Castrillo et al., 10 Oct 2025).
3. Memory System: Combines short-term memory (context window) with long-term, retrieval-augmented knowledge stores (vector DBs, SQL, log traces). External RAG frameworks, structured experience histories, skill repositories, or workflow memories supplement the LLM’s internal parameters, enabling both continuity and learning from experience (Zheng et al., 17 May 2025, Castrillo et al., 10 Oct 2025).
4. Execution System: Maps internal intent to environment actions through tool invocation (function calling, toolchains, API use), code generation/execution, GUI automation, and physical actuation (robotics). Coordination mechanisms monitor the effect of actions and resolve divergent states after each operation (Castrillo et al., 10 Oct 2025, Chen et al., 23 Apr 2025).

These components are composed in a closed-loop workflow, supporting continuous perception-reasoning-action-memory cycles, and may be deployed in both single-agent and multi-agent system (MAS) settings (Talebirad et al., 2023, Cheng et al., 7 Jan 2024).

2. Planning, Reasoning, and Hierarchical Control

LLM-based agents leverage advanced planning and reasoning techniques that support both single-path and multi-path compositional approaches:

• Global Planning and Hierarchical Execution: Agents like GoalAct dynamically maintain and refine an explicit global plan $G_t=\{(P_1\,A_1),\dots,(P_n\,A_n)\}$, selecting among high-level skills (e.g., searching, coding, writing) and invoking corresponding submodules for execution (Chen et al., 23 Apr 2025).
• Iterative Decomposition: Reasoning proceeds via chain-of-thought and tree-of-thought mechanisms, facilitating multi-step, branching, and self-consistent exploration. For complex workflows, agents may apply DPPM: decomposing tasks, planning for subtasks in parallel, and merging for execution.
• Reflection and Self-Improvement: Reflection experts (Reflexion, Self-Refine) operate as agent modules, analyzing outcomes, updating memory, and proposing corrections for subsequent iterations.

Hierarchical modularity (e.g., decomposition into skills, experts, or role-based agents) supports both tractable planning and dynamic adaptation, as empirically validated by superior performance on benchmarks requiring multi-hop reasoning, tool instantiation, and writing-intensive tasks (Chen et al., 23 Apr 2025).

3. Memory and Lifelong Adaptation

Memory is paradigmatic for agentic competence, realized through multi-tiered strategies:

• Short-Term (Episodic) Memory: Captures recent perceptions, actions, and context within the LLM’s working window.
• Long-Term (Retriable) Memory: Utilizes external retrievers and databases (vector stores, SQL, log files) for storing documents, prior task traces, and world knowledge. Retrieval-Augmented Generation (RAG) is fundamental for scalable continuity and grounding (Castrillo et al., 10 Oct 2025, Shi et al., 8 Nov 2024).
• Workflow and Skill Memory: Explicit, structured logs of execution paths, skill libraries, and successful procedures enhance task transfer and automate subgoal composition.
• Lifelong Learning & Transfer: Benchmarks such as LifelongAgentBench expose challenges due to LLM statelessness and limited working memory—revealing that standard experience replay is insufficient due to context overflow and irrelevant history pollution. The group self-consistency mechanism (GSC) mitigates these issues by partitioning memory for stable, efficient replay and majority aggregation (Zheng et al., 17 May 2025).

Limiting factors include context bottlenecks, non-trivial memory management (consolidation, summarization), and the challenge of catastrophic forgetting in sequential, long-range tasks.

4. Multi-Agent Systems and Collaborative Architectures

The transition from single-agent to multi-agent architectures introduces new capabilities and complexities:

• Agent-Oriented Modeling: Systems are described as graphs $G(V,E)$ where vertices represent agents (parameterized tuples including LLMs, role, state, children, halting rights) and plugins/tools, and edges model communication channels (Talebirad et al., 2023).
• Role Assignment and Dynamic Behavior: Agents are assigned roles (e.g., planner, executor, analyst), with privileged agents (supervisors, oracles) able to halt or refine other agents. Dynamic creation and destruction, privilege delegation, and memory sharing are formalized in the IGA framework (Talebirad et al., 2023).
• Inter-Agent Communication: Natural language message passing, backed by formal protocols (e.g., FIPA-ACL, KQML), enables complex workflows such as automated software development, courtroom simulation, and adversarial learning (Cheng et al., 7 Jan 2024, Talebirad et al., 2023).
• Coordination and Conflict: Feedback loops, privilege scoping, mediation, and oracle oversight are implemented to handle deadlocks, infinite loops, and security/safety in extended collaborative systems.

Multi-agent modeling enables application to domains that intrinsically require heterogeneity, interaction, or negotiation (e.g., manufacturing, legal reasoning, urban planning, multi-group simulations), with empirical benchmarks confirming their efficacy (Zhao et al., 27 May 2024, Han et al., 1 Jul 2025, Zhang et al., 7 Apr 2025).

5. Application Domains and Empirical Performance

LLM-based intelligent agents are being deployed and analyzed in domains characterized by complex, high-dimensional, and dynamic task structures:

• Financial Trading: RL/LLM hybrid agents demonstrated emergent sentiment manipulation strategies by generating social media posts that steer market sentiment through learned reinforcement signals. Performance improved (mean daily profit increased ~50%), but with negative externalities for non-adaptive counterparties (Byrd, 22 Feb 2025).
• Legal Reasoning and Writing: GoalAct showed a 12.22% mean absolute improvement over baselines on LegalAgentBench, particularly excelling in complex (multi-hop) logical reasoning and creative drafting (Chen et al., 23 Apr 2025).
• Manufacturing and Shopfloor Scheduling: Multi-agent LLM frameworks offer superior flexibility, real-time responsiveness, and reduced makespan compared to traditional rule-based heuristics in scheduling and resource allocation, validated both in simulation and on physical equipment (Zhao et al., 27 May 2024).
• Cluster Diagnosis: LLM-agent systems with RAG and Diagram of Thought (DoT) achieved perfect scores (1.0) on specialized cluster diagnosis benchmarks and a >6x speedup over human experts, highlighting the value of closed-loop diagnosis, self-play, and knowledge base integration (Shi et al., 8 Nov 2024).
• Education: Multi-agent, adversarial collaboration between evaluator, optimizer, and analyst generated lesson plans in EduPlanner with significantly superior multidimensional assessment (CIDDP score 88 vs. 49–74 for baselines), enabled by fine-grained skill-tree modeling and iterative refinement (Zhang et al., 7 Apr 2025).
• Music Recommendation and Supply Chain Planning: Modular, multi-agent LLM integrations (e.g., CrewAI, JD SCPA) increased subjective approval and objective accuracy/supply fulfillment, though with computational trade-offs versus classical methods (Boadana et al., 7 Aug 2025, Qi et al., 4 Sep 2025).

Performance gains across applications derive from increased flexibility, continual adaptation, and principled task decomposition.

6. Challenges: Hallucination, Security, Evaluation, and Scalability

LLM-based intelligent agents face critical robustness challenges:

• Hallucination Taxonomy: Hallucinations span reasoning (plan generation errors), execution (wrong tool selection/calling), perception (input errors), memorization (faulty retrieval/update), and communication (intra-/inter-agent misinformation). Eighteen root causes have been identified, including ambiguous objectives, insufficient tool documentation, sensor encoding errors, and protocol misalignments (Lin et al., 23 Sep 2025).
• Detection and Mitigation: Mitigation employs knowledge integration (external/internal), paradigm enhancements (contrastive/curriculum/causal learning), and post-hoc verification (self-reflection, validator assistance). However, detection lags behind—especially for compounded, stage-crossing hallucinations—demanding advancements in mechanistic interpretability and unified benchmarking (Lin et al., 23 Sep 2025).
• Security and Privacy: Prompt injection, data leakage, and action-level vulnerabilities are acute due to the open-ended operation of agentic LLMs. Countermeasures involve modular security layers, guardrails, adversarial training, and differential privacy; however, many current agents lack integrated security modules (Li et al., 10 Jan 2024, Hassouna et al., 17 Sep 2024).
• Scalability and Efficiency: High inference latency, context limits, memory overflow, and synchronization bottlenecks in large-scale or real-time environments remain unresolved. Model compression, on-device small-model deployment, modular inference pipelines, and hybrid edge-cloud architectures are active areas of research (Li et al., 10 Jan 2024, Tzachristas, 17 Dec 2024).

Empirical studies highlight failure modes such as task incompletion, instruction/format violations, and context overflows as dominant error classes limiting agent reliability (Zheng et al., 17 May 2025).

7. Future Directions and Open Problems

Emergent research questions include:

• Robust self-evolving workflows: Developing agents capable of continual self-improvement, knowledge updating, and drift adaptation under dynamic, open-ended conditions (Zheng et al., 17 May 2025, Lin et al., 23 Sep 2025).
• Unified architectures and evaluation: Proposals such as LLM-Agent-UMF aim to harmonize software interfaces, terminology, and modularity across agent types (single, multi, active, passive), enabling compositional systems with plug-and-play security and domain modules (Hassouna et al., 17 Sep 2024).
• Urban, societal, and collaborative domains: Urban LLM agents operating in hybrid cyber-physical-social spaces require new models for spatio-temporal reasoning, collaborative negotiation under conflicting stakeholder values, and rigorous fairness/safety evaluation frameworks (Han et al., 1 Jul 2025).
• Memory and planning at scale: Lifelong learning, skill transfer, and planning in the presence of thousands of tasks or skills, underpinned by scalable, context-aware retrieval, remain open (Zheng et al., 17 May 2025, Castrillo et al., 10 Oct 2025).
• Continual reliability and trust: Interpretable, explainable agentic operation, meta-cognitive monitoring, and transparent, benchmarked performance under high-stakes, multi-agent deployments are essential for real-world impact (Lin et al., 23 Sep 2025, Castrillo et al., 10 Oct 2025).

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Summary Table: Core Features of LLM-Based Intelligent Agents

Dimension	State-of-the-Art Implementation	Key References
Perception	Multimodal, tool-augmented, structured	(Castrillo et al., 10 Oct 2025, Shi et al., 8 Nov 2024)
Reasoning	Hierarchical, reflective, multi-path	(Chen et al., 23 Apr 2025, Castrillo et al., 10 Oct 2025)
Memory	Episodic + retrieval, RAG, skill repo	(Zheng et al., 17 May 2025, Castrillo et al., 10 Oct 2025)
Execution	Tool/API, code, UI, physical action	(Castrillo et al., 10 Oct 2025, Zhao et al., 27 May 2024)
Multi-agent	Role-based, dynamic, collaborative	(Talebirad et al., 2023, Hassouna et al., 17 Sep 2024)
Hallucination	Multi-stage, taxonomy, mitigation	(Lin et al., 23 Sep 2025)
Domain Impact	Trading, law, education, industry, urban	(Byrd, 22 Feb 2025, Chen et al., 23 Apr 2025, Zhang et al., 7 Apr 2025, Zhao et al., 27 May 2024, Han et al., 1 Jul 2025)

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LLM-based intelligent agents constitute a modular, adaptive paradigm at the intersection of natural language, closed-loop cognition, and real-world tool-use, with demonstrated advantages and active challenges for robust, trustworthy deployment in complex environments. Ongoing research focuses on reliability, composability, explainability, memory management, and principled evaluation to fulfill the promise of general-purpose AI agency.