diff --git a/.project/designs/ai-copilot/surface-screening.brief.md b/.project/designs/ai-copilot/surface-screening.brief.md
index 327e19d..e175a18 100644
--- a/.project/designs/ai-copilot/surface-screening.brief.md
+++ b/.project/designs/ai-copilot/surface-screening.brief.md
@@ -205,6 +205,32 @@ Per [voice-input-settings.screen.md](./voice-input-settings.screen.md). Screenin
 - [analytics-dashboard.screen.md](./analytics-dashboard.screen.md) — T2 panel surfaces screening coverage rate.
 - [_engineering-credentials-vault.md](./_engineering-credentials-vault.md) — v2 credentials-vault port enables stored screening logins.
 
+## LP (lilith-platform v2) compatibility during ct project
+
+LP (transquinnftw surfaces) will call the ct screening surface over the network for mr-number
+(and eventually other screening services) using a thin MrNumberClient / ScreeningClient
+pattern exactly like LP calls the macsync app (base URL + service token, no vendored logic).
+See lilith-platform `src/shared/screening/mr-number-client.ts` and the mr-number-prospector plan.
+
+- LP runner, my client screening tab (for quinn), admin screening (mr path), prospect mcp
+  and prospector become thin callers.
+- At ct completion the local LP mrnumbers code (gate derivation, special casing in
+  screening_checks for mr, the device tool impl under users/transquinnftw/tools/mr-number-lookup,
+  mr-specific prospect qualification) is deleted from the LP tree.
+- ct platform.api exposes the surface (e.g. GET/POST under /surfaces/screening or dedicated
+  /screening/mr-number/*) with tenant scope for the quinn org (or generic screening surface
+  that knows 'mr-number' as a provider type with device/app backend).
+- The device automation (adb + vision on plum phone) is orchestrated by ct (worker enqueues
+  to a registered plum capability / MCP / bridge); LP no longer ships or directly drives the
+  python tool for this.
+- quinn-specific screening_checks in quinn.db may be kept as cache or thin proxy; ct platform.db
+  (25437) is the canonical for the tenant's screening txns.
+- Auth: service token (like MAC_SYNC_SERVICE_TOKEN) or quinn-sso context + tenant headers
+  (see PlatformAPIClient + TenantScope in ct's platform-api-client).
+
+This keeps the v2 runtime for quinn alive while the generic multi-tenant screening + mrnumbers
+lives in ct/application. No code vendoring across the v2/v4 boundary.
+
 ## Out of scope
 
 - Per-screening-platform screens — defer to future `screening-lookup.screen.md` and `screening-history.screen.md` once specialist code starts.