LemonHarness Technical Report

LemonHarness is a newly announced integrated execution framework designed for long-horizon language model agents, establishing explicit execution boundaries to manage state changes during multi-step tasks. It constrains operations like file writes and artifact generation within a defined workspace, enhancing tracking and execution stability. Benchmark results show that LemonHarness_GPT-5.3-CodeX achieved 84.49% accuracy on Terminal-Bench 2.0, while the framework paired with the more powerful GPT-5.5 increased accuracy to 86.52%, highlighting its potential for improving the reliability of AI agents in complex workflows.