some cleanup

template/devenv.nix

@@ -1,6 +1,11 @@
 { pkgs, lib, config, inputs, ... }:
 <@if(eq(context.project.mobile,"expo"))>
 let
+  avdName = "Pixel_5_API36";
+  # Fixed console port, so scripts can address this emulator as emulator-5554 even when others run.
+  emulatorSerial = "emulator-5554";
+  # Apple's xcrun, for tools that need `xcrun simctl`, which the Nix SDK's xcrun lacks.
+  systemXcrun = pkgs.runCommand "system-xcrun" { } "mkdir -p $out/bin && ln -s /usr/bin/xcrun $out/bin/xcrun";
   # Sets dev_dir to Xcode's developer dir. devenv points DEVELOPER_DIR at the Nix SDK,
   # which xcode-select would echo back, so it is unset for the lookup.
   xcodeDevDir = ''
@@ -22,14 +27,14 @@ in
      pkgs.protoc-gen-connect-go
      pkgs.protoc-gen-es
      pkgs.cobra-cli
-  ];
+  ]<@if(eq(context.project.mobile,"expo"))> ++ lib.optionals pkgs.stdenv.isDarwin [ pkgs.cocoapods ]<@endif>;
   <@if(eq(context.project.mobile,"expo"))>
   android = {
     enable = true;
     emulator = {
       enable = true;
     };
-    buildTools.version = ["34.0.0" "35.0.0" "36.0.0" ];  # add 36.0.0
+    buildTools.version = [ "34.0.0" "35.0.0" "36.0.0" ];
     reactNative.enable = true;
     android-studio = {
       enable = false;
@@ -43,12 +48,16 @@ in
   enterShell = lib.optionalString pkgs.stdenv.isLinux ''
     export LD_LIBRARY_PATH=$ANDROID_HOME/emulator/lib64:$LD_LIBRARY_PATH
   '' + lib.optionalString pkgs.stdenv.isDarwin ''
-    ios-check || true
+    # Re-check at most daily once the iOS requirements are met. SKIP_IOS_CHECK=1 turns this off.
+    ios_check_ok="$DEVENV_STATE/ios-check-ok"
+    if [ -z "''${SKIP_IOS_CHECK:-}" ] && [ -z "$(find "$ios_check_ok" -mtime -1 2>/dev/null)" ]; then
+      if ios-check; then touch "$ios_check_ok"; else echo "Set SKIP_IOS_CHECK=1 to hide this." >&2; fi
+    fi
   '';
   # Use a system image matching the host CPU (arm64 on Apple Silicon, x86_64 elsewhere).
   scripts.create-avd.exec = ''
-    if ! avdmanager list avd -c | grep -qx "Pixel_5_API34"; then
-      echo no | avdmanager create avd -n "Pixel_5_API34" -k "system-images;android-34;google_apis_playstore;${if pkgs.stdenv.hostPlatform.isAarch64 then "arm64-v8a" else "x86_64"}" -d "pixel_5"
+    if ! avdmanager list avd -c | grep -qx "${avdName}"; then
+      echo no | avdmanager create avd -n "${avdName}" -k "system-images;android-36;google_apis_playstore;${if pkgs.stdenv.hostPlatform.isAarch64 then "arm64-v8a" else "x86_64"}" -d "pixel_5"
     fi
   '';
   # macOS only: Nix can't provide Xcode, so report what the iOS build still needs.
@@ -140,27 +149,42 @@ in
       exec = "create-avd";
     };
     emulator = {
-      exec = "emulator -avd Pixel_5_API34";
+      exec = "emulator -avd ${avdName} -port 5554";
       after = ["devenv:processes:createavd@completed"];
     };
+    # One Metro bundler serves both apps, so iOS doesn't depend on the Android build.
+    metro = {
+      exec = lib.optionalString pkgs.stdenv.isDarwin ''
+        # Expo's CLI calls `xcrun simctl` to talk to the iOS simulator.
+        ${xcodeDevDir}
+        export DEVELOPER_DIR="$dev_dir" PATH="${systemXcrun}/bin:$PATH"
+      '' + "exec bunx expo start --dev-client";
+      cwd = "./apps/mobile";
+      ready.http.get = { port = 8081; path = "/status"; };
+    };
     expodev = {
-      # Wait for the emulator to finish booting, otherwise expo tries to start a second copy of the AVD.
       exec = ''
-        adb -e wait-for-device
-        until [ "$(adb -e shell getprop sys.boot_completed 2>/dev/null | tr -d '\r')" = 1 ]; do sleep 2; done
-        bunx expo run:android
+        # Wait for the emulator to boot, otherwise expo tries to start a second copy of the AVD.
+        for _ in $(seq 150); do
+          if [ "$(adb -s ${emulatorSerial} shell getprop sys.boot_completed 2>/dev/null | tr -d '\r')" = 1 ]; then
+            # Lets the emulator and USB-connected devices reach the API on the host at 127.0.0.1:8080.
+            for device in $(adb devices | awk 'NR > 1 && $2 == "device" { print $1 }'); do
+              adb -s "$device" reverse tcp:8080 tcp:8080
+            done
+            exec bunx expo run:android --no-bundler --device ${avdName}
+          fi
+          sleep 2
+        done
+        echo "The Android emulator didn't finish booting within 5 minutes, see the emulator log." >&2
+        exit 1
       '';
       cwd = "./apps/mobile";
-      after= ["devenv:processes:emulator@started"];
-      restart = {
-        on = "always";
-      };
+      after = [ "devenv:processes:emulator@started" "devenv:processes:metro" ];
     };
-    # Reuses the Metro bundler started by expodev.
     expoios = lib.mkIf pkgs.stdenv.isDarwin {
       exec = "run-ios";
       cwd = "./apps/mobile";
-      after = ["devenv:processes:expodev@started"];
+      after = [ "devenv:processes:metro" ];
     };
     <@endif>
     sqlwatcher = {