The word "plugin" in Devin Desktop is dangerous because it sounds like one thing and means three. Which of the three you have in mind decides both what exactly is extended and whose trust chain you are connecting. Until the type is named, any talk of installing goes on blind.
The naive model is "a plugin is a plugin": you found the capability you need, installed it, and use it, as in any editor. From it grows the habit of installing without looking and the expectation that everything from the VS Code world will install and work here the same way. Behind this habit stands a generalization that looks right at first: in all editors plugins really do install similarly. Here it breaks not on the mechanics of installing but on what exactly the installed thing gets its hands on.
It breaks at once on three fronts, because three independent things stand behind the word. Editor extensions are installed inside Desktop and extend the IDE; in stable 3.7.16 the former Plugins section was indeed renamed to Extensions, and the catalog is based on Open VSX, with the marketplace configurable. Windsurf Plugins are different: they bring Cognition's capabilities into JetBrains, VS Code and other editors, that is, they live outside Desktop. Devin agent plugins are the third: they are installable bundles that contribute skills, rules, hooks, MCP servers and subagents to the agent, that is, they extend not the editor but the executor itself.
Hence the first consequence for extensions. A catalog based on Open VSX is not the same index as VS Code's proprietary marketplace, so not every proprietary VS Code extension is available or compatible here. The expectation "I will install the same plugin as in VS Code" sometimes comes true and sometimes does not, and that is not a breakage but a different catalog source. That the marketplace is configurable adds one more variable: the index you install from may not be the default one. It is worth understanding this in advance, so as not to read incompatibility as a breakage and go looking for the extension on the side, outside the vetted catalog.
The second consequence matters more and is common to all three types: installing an extension or a plugin is the execution of someone else's code in your environment. So before installing you check the publisher, the requested permissions, the update source and the scope. This is not bureaucracy but a recognition that the installed package gets access to the same things you do - to files, and in the case of an agent plugin to the agent's tools as well.
An agent plugin requires a separate, deeper review, because it extends the executor itself. Before enabling it, you look at what exactly it brings: which rules become durable instructions, which hooks stand around tool calls, which MCP servers receive grants, which subagents appear with their own context. An editor extension at worst gets in the editor's way; an agent plugin changes the behavior and permissions of an autonomous agent, and the cost of a mistake here is an order higher.
The cost of mixing the types is concrete. Taking an agent plugin for an ordinary extension, you skip the review of the agent's permissions and hand an autonomous executor tools and rules you never read. Taking a Windsurf Plugin for an editor extension, you look for it in the wrong place and configure the wrong environment. These are three independent trust chains, and trust granted in one does not carry over to the others.
You should verify by the type, named in full. For an editor extension - the publisher, the permissions, the update source and which marketplace it came from. For a Windsurf Plugin - which external editor it extends and on what terms. For an agent plugin - line by line, what it contributes to rules, hooks, MCP and subagents, and whether that matches what you are ready to give the agent. One question under each type: whose environment and whose permissions are you extending right now.
The engineering conclusion: "plugin" in Devin Desktop is not one thing but three, and the first step of any installation is to name the type in full. The type decides what is extended - the IDE, an external editor or the agent, where the code comes from - Open VSX, a third-party editor's ecosystem or an agent bundle, and which review is needed - compatibility, terms or the agent's permissions. Keeping these three questions apart is the whole discipline: the type sets the place, the source and the depth of the check, and none of the answers carries from one type to another.
The typical failures grow from a single substitution. An agent plugin is installed as "just an extension" and then people are surprised the agent behaved differently - though it was the plugin that overrode its rules and hooks. A Cognition capability is sought in the Extensions catalog, though it comes as a Windsurf Plugin in another editor. It is assumed that since an extension exists in VS Code it will install here too - and one runs into the Open VSX boundary. The sign is the same: the plugin type was not named before installing. Name it first, and the trust chain you are connecting becomes visible in advance.