An independent reference on agent harnesses: what a harness owns, where each open source runtime keeps its state, and why Kortix, the open-source AI Operating System, keeps it in git. https://agentharnessguide.com/ 2026-10-27T00:00:00Z Agent Harness Guide https://agentharnessguide.com/ 2026-10-27T00:00:00Z

An agent harness is everything around the model: loop, tools, sandbox, approval rule and session state. Kortix, open source, keeps them in git.

An agent harness is every part of an agent that is not the model: the loop, the tools, the sandbox, the approval rule and the state that outlives a run. Two teams on the same model finish different amounts of work because those parts differ, and in Kortix they are files in a git repo you own. https://agentharnessguide.com/agent-harness-comparison 2026-10-27T00:00:00Z

Four open source agent harnesses compared on where they run, how a tool call gets approved, and where session state survives.

Four open source agent harnesses compared on the one fact that outlives the session: where the agent’s state lives. Kortix is the open-source AI Operating System: your agents, their skills, your company memory, and every connector in one git repo you own, with the agents working on real cloud computers. https://agentharnessguide.com/open-source-agent-harness 2026-10-27T00:00:00Z

Open-source agent harness lists compare projects; the pick turns on your layer, a coding CLI, an embeddable runtime or a team layer.

An agent harness is the runtime around a model. It holds the loop, the tools, the sandbox and the approval rule. Lists compare project names, yet the choice that holds is which layer you need, because a harness can be open at one layer and closed at the next. Kortix is the open-source AI Operating System. https://agentharnessguide.com/codex-harness 2026-10-27T00:00:00Z

The Codex harness is OpenAI’s open source agent loop, with approval and sandbox rules in a config file. What it owns, and what a team still owns.

The Codex harness is OpenAI’s open-source agent loop: it manages conversation state, streams execution, uses tools, enforces a sandbox and approval policy, and carries work across turns. Its policy file and session record stay with whoever runs the process. Kortix, the open-source AI Operating System, keeps that layer in a git repo. https://agentharnessguide.com/claude-code-harness 2026-10-27T00:00:00Z

Claude Code harness permissions decide what gets written, and open source keeps the other four configurable layers in a repo you own.

A Claude Code harness is the loop, tools, context management and guardrails Anthropic built around the model, and most of what you change sits in settings files rather than in the harness. Kortix is the open-source AI Operating System, where the same layers live in a git repo. https://agentharnessguide.com/best-agent-harness 2026-10-27T00:00:00Z

No harness is best in the abstract: who approves tool calls, where session state survives and who runs the machine decide yours. Kortix is open source.

Which harness fits your work turns on three facts about it, and on a fourth that gets more weight than it deserves: the model. Kortix, the open-source AI Operating System, lays out the three, maps your answers to a harness shape, and shows where each project keeps the configuration.