Greg Isenberg: Agent Harnesses Are the New GPT Wrappers, Targeting a $5T Market
gethackteam · x · 2026-09-14
Greg Isenberg argues that agent harnesses are the new GPT wrappers, breaking down what a harness does:
- Runs the model in a loop so it keeps working step after step instead of answering once
- Gives it hands to read files, call tools, and run code
- Manages memory so hour three of a job still knows what happened in hour one
- Enforces rules on what the agent can touch and when it must ask a human
He frames the opportunity as huge: wrappers sell software ($800B market) while harnesses sell the work itself ($5T+). Crucially, harnesses aren't tied to one model — the job knowledge lives in the harness, so you can run GPT today, Claude next month, and open models like Gemma, Qwen, or DeepSeek locally later, all without rebuilding.
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