Stacklok's Mecatl trades the coding agent's unrestricted shell for a governed tool catalog

A coding agent is partway through a long refactor with no one watching when Kubernetes evicts its pod. In Mecatl, a replacement process picks the session up from the last persisted turn boundary. Session state and event history sit in durable storage under a single-writer model ^[10]. The replacement does not resume the operation that was in flight, and work after the last successful save can be lost ^[11]. Stacklok calls this turn-level durability and says it is not a distributed transaction ^[11]. "It is enough that a pod eviction stops being a conversation-ending event," the company wrote ^[16].

A laptop harness packed into a container handles that eviction worse. In Stacklok's account, every concern in it is still coupled to one long-lived machine ^[4]. "Kubernetes taught this industry that a monolith in a container is still a monolith," the post on the CNCF blog says ^[5][15].

The bigger cost is in the tool layer, and Stacklok spells it out. A desktop harness is useful in large part because it has an unrestricted shell, the company says, and a cloud-native harness does not need one ^[12]. Mecatl instead exposes purpose-built tools, skills and application integrations through an explicit catalog. Each one sits inside permission, audit and execution-environment boundaries ^[12]. A hosted agent starts from a catalog of things it is allowed to do ^[12].

Stacklok is specific about who this is for. It says the desktop design serves a single developer well ^[14]. The organizations it has in mind want to govern which tools each session may call, survive a node dying mid-task, or start a session on a laptop and pick it up on a phone ^[3]. It also expects these agent capabilities to reach people who will never open a terminal, and long-running workloads no one sits in front of ^[13]. The post does not include deployment counts, session volumes or failure rates from a running install. The case rests on design reasoning from the company that wrote the code ^[1].

Two questions sort the decision for any given workload. The first is whether a person watches the session while it runs. The second is whether every tool it needs can be written down as a list. I'd keep a watched session that needs an open shell on the laptop harness, which is the case Stacklok concedes the desktop design handles well ^[14]. An unwatched session whose tools fit on a list is the case Mecatl was built for ^[12][13]. When someone is watching and the tools fit on a list, a container can do the job until session counts or the laptop-to-phone handoff force the split ^[3]. The hard case is the unwatched session that still wants an unrestricted shell. Cut its tool list down before moving it. A replacement worker restores only the last saved turn, and nobody is at the keyboard to see what happened after it ^[11].