The bench timed two of the six RPCs the fix touches. Extend it to
image.attach, pdf.attach, clipboard.paste and image.detach so every changed
handler carries a number rather than an inference.
Also report which surfaces reach these RPCs at all, since "why was the GUI
special" is the first question the fix invites. CLI attaches inline in its
own turn path with the agent already built, so it cannot reach the stall;
the TUI calls the same RPCs and was equally exposed. The difference was hit
rate, not code path.
gateway_attach_bench.py drives the real dispatcher with a session whose agent
build is still running and times each attach RPC against prompt.submit as the
control — the harness that located the stall and measures it.
image-attach-bench.mjs times the renderer-side transforms (file read, base64,
RPC frame, embedded-image extraction, render-weight walk) across image sizes.
It is what ruled the renderer out: ~26ms total at 3MB.
Brooklyn Nicholson