## Problem
Connecting the MCP connector from **ChatGPT on Android** fails. The
installed Whisper Money PWA is a Chrome **WebAPK** that auto-verifies as
an Android **App Link handler** for the whole app origin (manifest
`scope: "/"`), so `https://whisper.money/oauth/authorize` gets routed
**into the app**. Once inside the standalone app, the redirect back to
the OAuth client can't complete → the connection fails. (Claude works
because it opens OAuth in a Custom Tab.)
Confirmed on an Android emulator: the WebAPK shows `AutoVerify=true`,
`whisper.money: verified`. DB evidence: ChatGPT registers + reaches
consent (auth codes issued) but never exchanges a token.
## Why not `handle_links`
`handle_links: "not-preferred"` (tried in #707, reverted in #708) is
**origin-wide** — it would push *every* `whisper.money` link (bank-auth
callback, email verification, shared deep links) to the browser, not
just `/oauth`. We want links to keep opening the installed app.
## Fix (surgical)
Move the OAuth **authorization server** to a dedicated host outside the
PWA scope. `config('mcp.authorization_server')` becomes env-driven
(`MCP_AUTHORIZATION_SERVER`); in prod → `https://oauth.whisper.money`
(DNS already points at the same app).
Every endpoint derives from the request host (no forced root URL), so
pointing the auth server at the subdomain makes `issuer` +
`authorize`/`token`/`register` all resolve to `oauth.whisper.money` —
**same origin as each other**, no cross-origin metadata mismatch. The
protected resource (`/mcp/oauth`) and **all other app links stay on
`whisper.money`**, so deep-linking into the app is fully preserved. Only
the OAuth flow leaves the app — into the browser, where the round-trip
completes.
## Activation (after merge + deploy)
1. Set `MCP_AUTHORIZATION_SERVER=https://oauth.whisper.money` in prod
env, redeploy.
2. I'll curl the discovery chain to confirm it resolves to the
subdomain.
3. Test the ChatGPT connect on a real phone.
Safe until step 1: env unset → `authorization_server` stays `null` →
current behavior. No effect on local/dev.
## Tests
Added a Pest test: with `mcp.authorization_server` configured,
protected-resource metadata advertises the dedicated host and
auth-server metadata (fetched from that host) keeps `issuer` + all
endpoints on it. App has no `TrustHosts` restriction (already serves the
subdomain) and `SESSION_DOMAIN=null` (host-only cookies — subdomain gets
its own session, no security downgrade).
