Copilot review round 3 on #2100.
- MCP_APP_ORIGIN_PORT could equal CLIENT_PORT or MCP_SANDBOX_PORT. The
app-origin listener starts BEFORE the web server binds, so that is not a
race it loses — it wins the port and the Inspector dies with EADDRINUSE.
`CLIENT_PORT=6278` was a valid config before this feature existed. It now
resolves to a dynamic port with a warning: of the three listeners this is
the only one that can move, and refusing to boot would cost the user the
whole Inspector over a feature they may not be using.
- The proxy's same-origin refusal covered only its own origin. An app served
from the INSPECTOR's origin is no safer: same-origin with the top document
means direct access to window.top, its DOM and its storage, and the
cross-origin frame in between buys nothing. Both trusted origins are now
refused before allow-same-origin is granted.
- Replaced the `as unknown as number` on `server.address()` with a real
narrowing of the string/null members of its return type.
- MCP_APP_ORIGIN_PORT added to the v1→v2 migration guide's env table, its
Docker recipe, and a troubleshooting entry for the symptom this actually
produces (the app renders, but its own backend rejects `Origin: null`).
- clients/web/README.md now states which failure is outside the fallback
guarantee — a published document the browser cannot reach — and why there
is no honest signal to fall back on. Docs and code no longer disagree.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0177mPHAdECD18nLLCTwR5rh
Signed-off-by: cliffhall <cliff@futurescale.com>
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