LangSmith Enhances Debugging for Complex AI Agents

Zach Anderson
Dec 10, 2025 18:37

LangSmith introduces advanced debugging tools for deep agents, including AI assistant Polly and LangSmith Fetch CLI, to enhance LLM application development.

LangSmith, a prominent tool in the landscape of large language model (LLM) applications, has unveiled new features aimed at refining the debugging process for complex AI agents, known as deep agents. These enhancements are designed to address the unique challenges posed by deep agents, which differ significantly from simpler LLM applications, according to the LangChain Blog.

Understanding Deep Agents

Deep agents are characterized by their extensive runtime, often involving numerous steps and interactions with users. Unlike simple LLM workflows, these agents can run for several minutes, generating vast amounts of trace data that pose a challenge for developers to analyze manually. This complexity necessitates advanced debugging tools, which LangSmith aims to provide.

New Tools for Enhanced Debugging

LangSmith’s latest offerings include an AI assistant named Polly and a command-line interface (CLI) tool called LangSmith Fetch. Polly assists developers by analyzing trace data and suggesting improvements to prompts. This AI-driven approach allows developers to efficiently identify inefficiencies or errors in the agent’s behavior, especially useful given the lengthy and complex nature of deep agent traces.

LangSmith Fetch, the CLI tool, is designed for developers who prefer working within integrated development environments (IDEs) or coding agents such as Claude Code. It enables quick access to trace data, allowing developers to fetch, analyze, and process agent execution data efficiently. This tool supports various output formats, catering to different developer needs, whether for terminal inspection or feeding results into other analytical tools.

Tracing and Analysis

Tracing is a core feature of LangSmith, providing visibility into the execution of AI agents. The platform records runs, traces, and threads, offering a comprehensive view of agent behavior. This data is crucial for debugging, as it helps developers pinpoint which part of the process may have led to unexpected outcomes.

With LangSmith, tracing is straightforward to set up, enabling developers to quickly integrate it into their workflows. Once set up, developers can leverage AI to gain insights into agent trajectories and refine agent prompts accordingly.

Polly: The AI Assistant

Polly, the AI assistant, is integrated within LangSmith to facilitate interactive debugging. By engaging with Polly, developers can query specific aspects of the trace, such as identifying inefficiencies or errors. This interactive approach is particularly beneficial for managing the complexity inherent in deep agents, where failures might be distributed across numerous steps.

Additionally, Polly aids in prompt engineering, a critical component of deep agent development. By interpreting natural language descriptions, Polly can refine prompts to ensure the desired agent behavior, enhancing the overall efficiency and effectiveness of the AI.

Conclusion

LangSmith’s new features represent a significant advancement in the debugging of deep agents. By providing tools like Polly and LangSmith Fetch, the platform empowers developers to navigate the complexities of AI agent development with greater ease and precision. These innovations underscore LangSmith’s commitment to enhancing the capabilities of LLM applications and supporting the development of more sophisticated AI solutions.

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