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Developer builds Perplexity-style web search agent, defines 'harness'

The author details the construction of a web search agent, inspired by Perplexity, which aims to decide when to search the web mid-answer and provide cited sources. The agent was built using a Bun backend, React 19 frontend, Tavily for search, and OpenRouter for the language model. After initial success, the author reflected on the definition of an "agent harness," distinguishing it from a simple script by the code that manages tool use and context, rather than the model itself. The implemented system features a looping mechanism where the model decides to use tools, context is managed by trimming messages, and output is a structured event stream, confirming it as a functional, albeit single-tool, harness. AI

IMPACT Provides a practical example of building an agentic harness, highlighting the distinction between a script and a true agent.

RANK_REASON Developer describes building a specific AI-powered tool and reflects on its technical definition.

Read on dev.to — LLM tag →

AI-generated summary · Google Gemini · from 1 sources. How we write summaries →

Developer builds Perplexity-style web search agent, defines 'harness'

COVERAGE [1]

  1. dev.to — LLM tag TIER_1 English(EN) · Saurabh Singh ·

    I Built a Web Search Agent Harness. Then I Checked If It Actually Deserved the Name.

    <h1> I Built a Web Search Agent Harness. Then I Checked If It Actually Deserved the Name. </h1> <p><em>Part 1 of my agent build series</em></p> <p>Let me set the scene.</p> <p>I wanted a Perplexity-style search assistant — type a question, watch it decide to go search the web mid…