Harness Engineering: What It Is and How It Works
Perplexity, Monday, October 19th, 2026
Perplexity explains harness engineering, the design of everything around an AI model that makes agents reliable.
Perplexity defines harness engineering as designing every component of an AI tool apart from the model, including how information reaches the model and how its work is checked.
Because a model alone handles only text and forgets earlier exchanges, the harness supplies history, tool access and oversight.
Harnesses matter most for agents performing multi-step tasks, where an early mistake can affect every later step.
Perplexity says agent harnesses typically include an agent loop, context management, tools, memory, permissions and verification.