The big gundown

The spec says: "An embedder may terminate an agent without any of the agent's cluster's other agents' prior knowledge or cooperation."

Can we define "embedder" more precisely here? Are we talking about the browser or the surrounding (in a browser context) JS application? Either? I've worked fairly hard for no-notification killing not to be allowed in the HTML/JS space, where the embedder/embeddee concept is easier, and although I'm not sure I've succeeded completely, I've at least succeeded in removing prose from the HTML spec that allows workers to be gunned down at random.

And while I'm here, "prior"? Is there any kind of post-hoc notification facility intended?

It might be interesting to have a discussion about why this prose is here. It is one thing for the agent itself to do something silly so that it traps (OOB); another thing for the embedding to remove an entire cluster; a third thing for an embedding to remove a single agent within the cluster, which IMO is bad.

(Also, what is "terminate"? The issue also comes up here, https://github.com/WebAssembly/exception-handling/issues/16)

No file or test is named in the issue. Start by locating the specification text containing the quoted “embedder” and “terminate” language, then compare its intended scope with the HTML/JS worker discussion and WebAssembly/exception-handling#16; done means the terminology and notification or termination behavior are explicitly resolved.