Teams building AI agents can stand up stateful clones of the apps those agents call, including Gmail, Slack, Salesforce, Notion, and Quickbooks, and test changes against realistic tools, data, and state before a live account is touched. Agents now send email, update records, and issue refunds, but a production failure is hard to reproduce, and mocked APIs or empty sandbox tenants leave out the history and business detail a real run depends on. Hue, launching from Y Combinator's Fall 2026 batch, records each agent run and rebuilds the world it happened in, so teams can replay the same apps, context, and moment, and simulate new edge cases, before a change ships. A world can be generated from a short description or rebuilt from a real run. Describe the apps of a 40-person software company that just raised a Series B, and Hue populates them with months of realistic history in a couple of minutes. Import traces through the Hue SDK or OpenTelemetry, and Hue recreates the state of that run so a failure can be reproduced and a fix checked from the same starting point as many times as needed. The agent stays in the team's own process while Hue hosts the simulated apps, reached the same way as production tools, through APIs, MCP, or connectors such as Composio and Pipedream. Each run gets its own world that records every change, so versions can be scored and compared before anything ships. Hue is a two-person company in San Francisco founded by Aneesh Kethini and Josh Le. Kethini, CEO, was the second AI product manager at Datadog, where he built and launched Datadog's AI SRE agent, and before that a quantitative trader at Susquehanna International Group. Le, CTO, previously built legal agents at August and worked as an engineer at Apple, Gusto, Wayfair, and SendBlue. In earlier roles they were responsible for testing environments and systems that turn production usage into replayable scenarios.