diff --git a/apps/desktop/src/api/sessions.ts b/apps/desktop/src/api/sessions.ts
index c89ce10756..3e51132d06 100644
--- a/apps/desktop/src/api/sessions.ts
+++ b/apps/desktop/src/api/sessions.ts
@@ -1,4 +1,5 @@
 import { isMissingRestEndpoint } from '@/lib/gateway-rpc'
+import { stampRowsWithOwningConnection } from '@/lib/session-owner-stamp'
 import { recordTranscriptTail } from '@/store/transcript-tail'
 import type {
   PaginatedSessions,
@@ -37,16 +38,11 @@ function sessionScopeQuery(scope?: ProfileScope): string {
  * correctly know nothing about this Desktop-local registry id. Preserve an
  * explicit owner from a multi-source response; otherwise stamp the active
  * non-local source so a later resume cannot fall back to a same-named local
- * profile.
+ * profile. Delegates to the canonical row-stamp helper so this stays the ONE
+ * write shape for connection_id on backend-returned rows.
  */
 function stampActiveConnectionOwner(sessions: SessionInfo[]): SessionInfo[] {
-  const connectionId = getApiRequestConnection()?.trim()
-
-  if (!connectionId || connectionId === 'local') {
-    return sessions
-  }
-
-  return sessions.map(session => (session.connection_id ? session : { ...session, connection_id: connectionId }))
+  return stampRowsWithOwningConnection(sessions, getApiRequestConnection())
 }
 
 /**
diff --git a/apps/desktop/src/lib/session-owner-stamp.ts b/apps/desktop/src/lib/session-owner-stamp.ts
new file mode 100644
index 0000000000..09a6b8a58d
--- /dev/null
+++ b/apps/desktop/src/lib/session-owner-stamp.ts
@@ -0,0 +1,28 @@
+import type { SessionInfo } from '@/types/hermes'
+
+/**
+ * THE canonical write path for tagging backend-returned session rows with the
+ * registry connection that owns them (the read counterpart is
+ * `sessionOwnerRouteFromRow` in store/session-request-router).
+ *
+ * Every other `connection_id` writer works from an EXACT captured owner route
+ * (the optimistic row in upsertOptimisticSession, the cache patch in
+ * use-session-actions/utils, the mergeSessionPage carry) — those are
+ * authoritative and this helper must never clobber them, so a row that
+ * already names an owner is returned untouched. Only untagged rows served by
+ * an active NON-local source get stamped: the gateway's HTTP APIs correctly
+ * know nothing about Desktop-local registry ids, and an untagged remote row
+ * would let a later resume fall back to a same-named local profile
+ * ("session not found" on turn two). `local` is never stamped — a bare local
+ * row already routes correctly and a `local` tag would only pin it against
+ * the fail-closed owner resolution for no benefit.
+ */
+export function stampRowsWithOwningConnection(sessions: SessionInfo[], connectionId: null | string | undefined): SessionInfo[] {
+  const owner = String(connectionId ?? '').trim()
+
+  if (!owner || owner === 'local') {
+    return sessions
+  }
+
+  return sessions.map(session => (session.connection_id?.trim() ? session : { ...session, connection_id: owner }))
+}