@@ -13,10 +13,17 @@ const onboardingScheduler = createAtomCommandScheduler();
 export const connectPairingUrl = createRuntimeCommand(connectionAtomRuntime, {
   label: "mobile:connection:connect-pairing-url",
   scheduler: onboardingScheduler,
-  concurrency: { mode: "singleFlight", key: (pairingUrl: string) => pairingUrl },
-  execute: (pairingUrl: string) =>
+  concurrency: {
+    mode: "singleFlight",
+    key: (input: { readonly pairingUrl: string }) => input.pairingUrl,
+  },
+  execute: (input: {
+    readonly pairingUrl: string;
+    /** Set when adding a route to this saved machine. */
+    readonly expectedEnvironmentId?: EnvironmentId;
+  }) =>
     ConnectionOnboarding.ConnectionOnboarding.pipe(
-      Effect.flatMap((onboarding) => onboarding.registerPairing({ pairingUrl })),
+      Effect.flatMap((onboarding) => onboarding.registerPairing(input)),
     ),
 });
 
 
@@ -6,6 +6,7 @@ import {
   useRoute,
   type StaticScreenProps,
 } from "@react-navigation/native";
+import type { EnvironmentId } from "@t3tools/contracts";
 import { AsyncResult } from "effect/unstable/reactivity";
 import { useCallback, useEffect, useRef, useState } from "react";
 import { Alert, Linking, Platform, View } from "react-native";
@@ -23,6 +24,8 @@ type ConnectionsNewRouteParams = {
   readonly mode?: string;
   readonly pairingUrl?: string;
   readonly autoConnect?: string;
+  /** Adds a route to this saved machine instead of a new environment. */
+  readonly routeFor?: EnvironmentId;
 };
 
 export function ConnectionsNewRouteScreen({
@@ -158,7 +161,7 @@ export function ConnectionsNewRouteScreen({
       setIsSubmitting(true);
       onChangeConnectionPairingUrl(pairingUrl);
       try {
-        const result = await onConnectPress(pairingUrl);
+        const result = await onConnectPress(pairingUrl, params.routeFor);
         if (AsyncResult.isSuccess(result)) {
           if (replaceWithHome || !navigation.canGoBack()) {
             navigation.dispatch(StackActions.replace("Home"));
@@ -170,7 +173,7 @@ export function ConnectionsNewRouteScreen({
         setIsSubmitting(false);
       }
     },
-    [navigation, onChangeConnectionPairingUrl, onConnectPress],
+    [navigation, onChangeConnectionPairingUrl, onConnectPress, params.routeFor],
   );
 
   const handleSubmit = useCallback(async () => {
 
@@ -69,7 +69,11 @@ export function useConnectionController() {
   );
 
   const connectPairingUrl = useCallback(
-    (pairingUrl: string) => connectPairingUrlMutation(pairingUrl),
+    (pairingUrl: string, expectedEnvironmentId?: EnvironmentId) =>
+      connectPairingUrlMutation({
+        pairingUrl,
+        ...(expectedEnvironmentId === undefined ? {} : { expectedEnvironmentId }),
+      }),
     [connectPairingUrlMutation],
   );
   const connectRelayEnvironment = useCallback(