three.dev helps teams detect failures in AI agents running in production. Instead of waiting for users to report subtle problems like incorrect policies or fabricated responses, it analyzes live traffic to surface and rank failures by severity. Setup is designed around coding agents: one prompt to Claude Code, Cursor, or Codex gives the agent the context needed to write a fix.
three.dev
Find out how your AI agent fails. Before your users do.
three.dev Introduction
Key Features
- Automatically detects AI agent failures in live production traffic
- Ranks detected failures by severity
- One-prompt setup with Claude Code, Cursor, or Codex
- Provides coding agents with the context needed to write fixes
Use Cases
- Monitoring AI agents in production for silent behavioral failures
- Detecting incorrect or fabricated agent responses before users report them
- Prioritizing fixes for AI agent issues by severity
Why Startups Use It
Startups shipping AI agents often learn about failures only when users complain, since these errors don't crash anything. three.dev surfaces quiet production failures automatically and ranks them by severity, helping small teams catch and fix agent issues early without building custom monitoring.
Alternative Options
LangSmith, Langfuse, Braintrust
Frequently Asked Questions
What does three.dev do?
It finds failures in AI agent behavior from live production traffic and ranks them by severity so teams can fix issues before users report them.
How is three.dev set up?
Setup is a single prompt to coding agents such as Claude Code, Cursor, or Codex, which then receive the context needed to write fixes.
More About three.dev
PricingPaid
Listed DateNov 13, 2026
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