Gating this behind an opt-in was the wrong call. A dev server already
executes arbitrary local JS — vite's module graph, every postinstall in
node_modules — so a loopback debugging port does not meaningfully widen
what a `npm run dev` session can already do, and `perf:serve` has opened
one unconditionally all along.
Requiring the variable also defeated the point: the tooling exists to be
reached for mid-task, and a capability you must remember to enable before
launching is one you don't have when you need it.
So the port opens on 9222 — the same port scripts/eval.mjs and
scripts/perf/lib/cdp.mjs already default to — for any dev-server run.
HERMES_DESKTOP_CDP_PORT stops being an on-switch and becomes an
override: a different port, or `off` to disable.
The hard gate is unchanged and still checked first: a packaged build
never opens the port, and no env value talks it into it. Neither does an
unpackaged `electron .` against dist/, which is how the packaged app
gets smoke tested.
Refusals only log when they contradict something the developer asked for
(a typo'd port, an explicit `off`). Packaged and dist runs are closed by
design and stay quiet.
The renderer is a Chromium page, and apps/desktop already carries a whole
CDP toolkit for it — scripts/eval.mjs, scripts/perf/lib/cdp.mjs with its
shared SELECTORS map, and the diag-*/probe-* family. None of it can
attach to `hgui` or `npm run dev`, because neither passes
--remote-debugging-port. The only launcher that opens one is
`npm run perf:serve`, which is a separate isolated instance rather than
the app you're looking at.
Add HERMES_DESKTOP_CDP_PORT. When set, the shell opens a CDP port on
loopback so that existing tooling can read the live DOM: computed
styles, geometry, which rule actually won.
Three independent gates, all required, resolved by a pure function in
electron/dev-cdp.ts so the policy is testable without an Electron app:
1. not packaged — a shipped build never opens the port, and this is
checked first so no env combination can talk it into doing so;
2. HERMES_DESKTOP_DEV_SERVER present — an unpackaged `electron .`
against dist/ is how the packaged app gets smoke tested, so it
behaves like the packaged app here;
3. the port explicitly requested and a valid integer.
Default `npm run dev` is unchanged and silent: no port, no nag. An
opt-in that gets refused always logs why, so nobody loses an hour
wondering what isn't listening.
The address is pinned to 127.0.0.1 rather than left to Chromium's
default, and is deliberately not configurable — there's no reason to
expose a renderer debugger off-host and offering the knob invites
someone to try.
scripts/eval.mjs hardcoded :9222 and threw a raw ECONNREFUSED stack when
nothing was there. It now honours the same variable and explains itself.
