diff --git a/apps/desktop/src/store/connection-registry-state.ts b/apps/desktop/src/store/connection-registry-state.ts
new file mode 100644
index 0000000000..6b7071a134
--- /dev/null
+++ b/apps/desktop/src/store/connection-registry-state.ts
@@ -0,0 +1,11 @@
+import { atom } from 'nanostores'
+
+import type { DesktopConnectionsRegistry } from '@/global'
+
+/** Null only for the legacy profile-only Desktop topology. Once Electron has
+ * published a registry, profile names are source-local and are not owners. */
+export const $connectionsRegistry = atom<DesktopConnectionsRegistry | null>(null)
+
+export function hasRegistryTopology(): boolean {
+  return $connectionsRegistry.get() !== null
+}
diff --git a/apps/desktop/src/store/connections.ts b/apps/desktop/src/store/connections.ts
index 59e26cdda0..8a0e242ef2 100644
--- a/apps/desktop/src/store/connections.ts
+++ b/apps/desktop/src/store/connections.ts
@@ -3,6 +3,7 @@ import { atom, computed } from 'nanostores'
 import type { DesktopConnectionsRegistry } from '@/global'
 import { persistStringRecord, storedStringRecord } from '@/lib/storage'
 import { isTimeoutError, withTimeout } from '@/lib/with-timeout'
+import { $connectionsRegistry } from '@/store/connection-registry-state'
 import {
   beginGatewaySwitch,
   endGatewaySwitch,
@@ -32,7 +33,7 @@ const SWITCH_DIAL_TIMEOUT_MS = 20_000
 const SWITCH_COMMIT_TIMEOUT_MS = 20_000
 const SWITCH_REMEMBER_TIMEOUT_MS = 5_000
 
-export const $connectionsRegistry = atom<DesktopConnectionsRegistry | null>(null)
+export { $connectionsRegistry } from '@/store/connection-registry-state'
 
 // Use only the resolved descriptor identity Electron publishes. `primary`
 // means the registry default, not necessarily the source this window is using;
diff --git a/apps/desktop/src/store/session-owner-resolution.test.ts b/apps/desktop/src/store/session-owner-resolution.test.ts
new file mode 100644
index 0000000000..36e4198cfc
--- /dev/null
+++ b/apps/desktop/src/store/session-owner-resolution.test.ts
@@ -0,0 +1,64 @@
+import { beforeEach, describe, expect, it } from 'vitest'
+
+import { $connectionsRegistry } from './connections'
+import { $profiles } from './profile'
+import {
+  ambientGatewayOwnsEverySession,
+  assertSessionOwnerResolved,
+  sessionOwnerIsKnown
+} from './session-owner-resolution'
+
+const registry = (...ids: string[]) =>
+  ({
+    connections: ids.map(id => ({ id })),
+    lastUsed: ids[0] ?? null,
+    launchMode: 'primary',
+    primary: ids[0] ?? null
+  }) as never
+
+beforeEach(() => {
+  $connectionsRegistry.set(null)
+  $profiles.set([])
+})
+
+describe('session owner topology', () => {
+  it('fails closed on an unknown owner in registry topology while preserving legacy profile routes', () => {
+    // A connection registry means the ambient gateway is never provably the
+    // sole backend, even with one profile listed: an unknown owner fails
+    // closed. A bare profile still names a backend — the legacy profile door
+    // (a pick on the primary / explicit `local` source) mints sessions owned
+    // by that profile's pool socket in every topology.
+    $connectionsRegistry.set(registry('local'))
+    $profiles.set([{ name: 'default' }] as never)
+
+    expect(sessionOwnerIsKnown('default')).toBe(true)
+    expect(ambientGatewayOwnsEverySession()).toBe(false)
+    expect(() =>
+      assertSessionOwnerResolved('default', { method: 'session.resume', sessionId: 'registry-profile' })
+    ).not.toThrow()
+    expect(() => assertSessionOwnerResolved(null, { method: 'session.resume', sessionId: 'unknown-owner' })).toThrow(
+      /could not be resolved/i
+    )
+
+    $connectionsRegistry.set(registry('local', 'homelab'))
+    expect(sessionOwnerIsKnown(null)).toBe(false)
+    expect(ambientGatewayOwnsEverySession()).toBe(false)
+    expect(() => assertSessionOwnerResolved(null, { method: 'session.resume', sessionId: 'unknown-owner' })).toThrow(
+      /could not be resolved/i
+    )
+
+    $connectionsRegistry.set(null)
+    expect(sessionOwnerIsKnown('default')).toBe(true)
+    expect(ambientGatewayOwnsEverySession()).toBe(true)
+    expect(() =>
+      assertSessionOwnerResolved(null, { method: 'session.resume', sessionId: 'legacy-single-profile' })
+    ).not.toThrow()
+
+    $profiles.set([{ name: 'default' }, { name: 'loki' }] as never)
+    expect(sessionOwnerIsKnown('loki')).toBe(true)
+    expect(ambientGatewayOwnsEverySession()).toBe(false)
+    expect(() =>
+      assertSessionOwnerResolved('loki', { method: 'session.resume', sessionId: 'legacy-profile-owner' })
+    ).not.toThrow()
+  })
+})
diff --git a/apps/desktop/src/store/session-owner-resolution.ts b/apps/desktop/src/store/session-owner-resolution.ts
index ae280979ac..028428bd82 100644
--- a/apps/desktop/src/store/session-owner-resolution.ts
+++ b/apps/desktop/src/store/session-owner-resolution.ts
@@ -13,12 +13,12 @@
  * session is left untouched for the next correctly-routed attempt.
  *
  * The ONE case where the ambient gateway is not a fallback but the owner by
- * construction: no registry source is live (legacy v1 primary) AND at most
+ * construction: no registry topology exists (legacy v1 primary) AND at most
  * one profile exists — a single backend serves every session, so there is
  * nothing to misroute to. Older single-profile backends omit `profile` on
  * their rows entirely; those users keep working unchanged.
  */
-import { activeGatewayConnectionId } from './gateway'
+import { hasRegistryTopology } from './connection-registry-state'
 import { $profiles } from './profile'
 import { isSessionOwnerRoute, type SessionOwnerScope } from './session-request-router'
 
@@ -44,13 +44,19 @@ export function isSessionOwnerResolutionError(error: unknown): error is SessionO
 }
 
 /** True when the ambient gateway is provably the only backend any session
- *  can live on (legacy single-backend Desktop): no registry source is active
- *  and there is at most one profile. Everything else has somewhere to misroute. */
+ *  can live on (legacy single-backend Desktop): Electron has published no
+ *  connection registry and there is at most one profile. The active route is
+ *  presentation state; a null active connection does not prove sole topology. */
 export function ambientGatewayOwnsEverySession(): boolean {
-  return activeGatewayConnectionId() === null && $profiles.get().length <= 1
+  return !hasRegistryTopology() && $profiles.get().length <= 1
 }
 
-/** True when `owner` names a backend (an exact route or a profile). */
+/** True when `owner` names a backend: an exact connection route, or a bare
+ *  profile. A bare profile stays an owner in registry topology too — a profile
+ *  pick on the primary or the explicit `local` source takes the legacy
+ *  profile-only door (store/profile activateOnCurrentSource, so a per-profile
+ *  remote override resolves), and a session minted there is owned by that
+ *  profile's pool socket, which requestForSessionProfile dials by name. */
 export function sessionOwnerIsKnown(owner: SessionOwnerScope): boolean {
   if (isSessionOwnerRoute(owner)) {
     return Boolean(owner.connectionId.trim())
diff --git a/apps/desktop/src/store/session-request-router.test.ts b/apps/desktop/src/store/session-request-router.test.ts
index 913d1930ab..3ec852e284 100644
--- a/apps/desktop/src/store/session-request-router.test.ts
+++ b/apps/desktop/src/store/session-request-router.test.ts
@@ -78,6 +78,7 @@ const {
 } = await import('./gateway')
 
 const { requestForSessionProfile, sessionRpcNeedsProfileRoute } = await import('./session-request-router')
+const { $connectionsRegistry } = await import('./connection-registry-state')
 
 function installDesktop(): void {
   ;(window as unknown as { hermesDesktop: unknown }).hermesDesktop = {
@@ -103,6 +104,7 @@ function makePrimary() {
 beforeEach(() => {
   secondaryGateways.length = 0
   promptAckStatus = null
+  $connectionsRegistry.set(null)
   configureGatewayRegistry({ onEvent: vi.fn() })
   closeSecondaryGateways()
 })
@@ -177,6 +179,26 @@ describe('sessionRpcNeedsProfileRoute', () => {
 })
 
 describe('requestForSessionProfile', () => {
+  it('keeps routing a bare profile owner through its legacy profile pool when a connection registry exists', async () => {
+    // A profile pick on the primary or the explicit `local` source takes the
+    // legacy profile-only door (store/profile activateOnCurrentSource), so a
+    // session minted there is owned by that profile's pool socket in every
+    // topology — a registry does not turn the bare profile into a guess.
+    const primary = makePrimary()
+    setPrimaryGateway(primary as never, 'default')
+    installDesktop()
+    $connectionsRegistry.set({ connections: [{ id: 'local' }] } as never)
+    const ambient = vi.fn(async () => ({ ambient: true }))
+
+    await expect(
+      requestForSessionProfile('loki', ambient as never, 'session.resume', { session_id: 'stored-a' })
+    ).resolves.toEqual({ method: 'session.resume', params: { session_id: 'stored-a' } })
+    expect(window.hermesDesktop!.getConnection).toHaveBeenCalledWith('loki')
+    expect(secondaryGateways).toHaveLength(1)
+    expect(primary.request).not.toHaveBeenCalled()
+    expect(ambient).not.toHaveBeenCalled()
+  })
+
   it('keeps concurrent same-name requests pinned while foreground activation changes', async () => {
     const primary = makePrimary()
     setPrimaryGateway(primary as never, 'default')
diff --git a/apps/desktop/src/store/session-request-router.ts b/apps/desktop/src/store/session-request-router.ts
index 65649fd034..3cb1993c33 100644
--- a/apps/desktop/src/store/session-request-router.ts
+++ b/apps/desktop/src/store/session-request-router.ts
@@ -131,6 +131,8 @@ async function withRoutedTurnLease<T>(
  *
  * A KNOWN owner (route or profile name) always needs its own socket: the
  * session belongs to that profile regardless of what the window is showing.
+ * A bare profile names the legacy profile door's pool socket in every
+ * topology (a pick on the primary / explicit `local` source dials it).
  * There is deliberately NO comparison against the active profile — "active" is
  * presentation state, never a routing authority. Only a null/empty owner (a
  * fresh draft with no session, or global chrome) routes ambient.