Posted on September 28, 2026 by Craig McLuckie, Stacklok Coding agents became useful when they stopped being a chat box. Four things changed the shape of the problem: capable tools, a shared repository and filesystem, subagents, and skills that capture what the system learned from prior work. Together, those let an agent operate in an environment instead of merely answering questions about one. These patterns grew up on developer laptops because developers already live in terminals, repos, and toolchains. They will not stay there.
The same capabilities are heading toward people who will never open a terminal, and toward long-running workloads that no one is sitting in front of. That is where the usual harness shape starts to creak. Most harnesses assume a desktop: one person, one machine, one local filesystem, one interactive process that is simultaneously the UI, the agent loop, the sandbox, the credential store, the tool host, and the session database. That design serves a single developer well.
It fits poorly when an organization wants to run hundreds of sessions, govern which tools each one may call, survive a node dying mid-task, or let someone start a session from a laptop and pick it up from a phone. The tempting fix is to put the desktop harness in a container and call it done. That moves where the process runs and leaves how the process is built untouched. Every concern is still coupled to one long-lived machine. Kubernetes taught this industry that a monolith in a container is still a monolith. The lesson applies to agents too.
A harness for this next phase should be designed as a distributed application from the start, with the agent loop separated from everything around it, so that hosting, exposure, and security fall out of the architecture rather than getting bolted on afterward. At Stacklok, we have been calling this a cloud-native harness. We recently open sourced our cloud-native harness, Mecatl, and I want to walk through what the shape looks like in practice. The name, pronounced "meh-kah-tl," is classical Nahuatl for cord, rope, or string. Ozz, the principal engineer who started the project, picked it.