diff --git a/.env.example b/.env.example
index 2674c44d4..33060cd54 100644
--- a/.env.example
+++ b/.env.example
@@ -13,6 +13,10 @@ STOREFRONT_ACCESS_TOKEN=your-public-storefront-access-token
 # Optional Apple Pay merchant identifier used by accelerated checkout flows.
 STOREFRONT_MERCHANT_IDENTIFIER=
 
+# Apple team that signs the Swift samples. Set your own team id, or the Xcode build
+# fails at signing. A blank value stays blank; setup applies no default team.
+DEVELOPMENT_TEAM=
+
 # Storefront API version
 API_VERSION=2026-04
 
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 75d7232bb..5b360a66f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -63,7 +63,7 @@ jobs:
               - 'Package.swift'
               - 'Package.resolved'
               - '.github/workflows/swift-test-package.yml'
-              - '.github/workflows/swift-build-samples.yml'
+              - '.github/workflows/swift-build-and-test-samples.yml'
               - '.github/workflows/swift-test-workflow.yml'
               - '.github/workflows/swift-lint.yml'
               - '.github/workflows/breaking-changes.yml'
@@ -129,11 +129,11 @@ jobs:
     if: needs.changes.outputs.swift == 'true'
     uses: ./.github/workflows/swift-test-package.yml
 
-  swift-build-samples:
+  swift-build-and-test-samples:
     name: Swift
     needs: changes
     if: needs.changes.outputs.swift == 'true'
-    uses: ./.github/workflows/swift-build-samples.yml
+    uses: ./.github/workflows/swift-build-and-test-samples.yml
 
   swift-lint:
     name: Swift
@@ -250,7 +250,7 @@ jobs:
       - changes
       - android-test
       - swift-test-package
-      - swift-build-samples
+      - swift-build-and-test-samples
       - swift-lint
       - swift-sample-package-paths
       - rn-test
diff --git a/.github/workflows/rn-test.yml b/.github/workflows/rn-test.yml
index 9f957b75d..f8848a566 100644
--- a/.github/workflows/rn-test.yml
+++ b/.github/workflows/rn-test.yml
@@ -36,3 +36,8 @@ jobs:
           coverage-summary-path: platforms/react-native/coverage/coverage-summary.json
           title: 'React Native — Coverage Report'
           create-new-comment: false
+
+      # Runs without --coverage so the coverage report above stays scoped to the
+      # published module.
+      - name: Run sample tests
+        run: pnpm test --testPathPatterns="sample/src"
diff --git a/.github/workflows/swift-build-samples.yml b/.github/workflows/swift-build-and-test-samples.yml
similarity index 52%
rename from .github/workflows/swift-build-samples.yml
rename to .github/workflows/swift-build-and-test-samples.yml
index 0821942c4..0cc601740 100644
--- a/.github/workflows/swift-build-samples.yml
+++ b/.github/workflows/swift-build-and-test-samples.yml
@@ -1,4 +1,4 @@
-name: Swift — Build Sample Apps
+name: Swift — Build & Test Sample Apps
 
 on:
   workflow_call:
@@ -8,9 +8,9 @@ permissions:
   contents: read
 
 jobs:
-  build-samples:
+  build-and-test-samples:
     uses: ./.github/workflows/swift-test-workflow.yml
     with:
-      test-path: ./Scripts/build_samples
-      job-name: Build Sample Apps
+      test-path: ./Scripts/build_and_test_samples
+      job-name: Build & Test Sample Apps
       setup-storefront-env: true
diff --git a/.github/workflows/swift-update-linters.yml b/.github/workflows/swift-update-linters.yml
index c87e0caec..5238cd2f9 100644
--- a/.github/workflows/swift-update-linters.yml
+++ b/.github/workflows/swift-update-linters.yml
@@ -135,7 +135,7 @@ jobs:
           BODY+="1. **Close and reopen this PR** — this fires a new \`pull_request\` event from your user, which triggers all checks.\n"
           BODY+="2. **Trigger workflows via CLI:**\n"
           BODY+="\`\`\`bash\n"
-          BODY+="gh workflow run swift-build-samples.yml --ref auto/update-linters\n"
+          BODY+="gh workflow run swift-build-and-test-samples.yml --ref auto/update-linters\n"
           BODY+="gh workflow run swift-lint.yml --ref auto/update-linters\n"
           BODY+="gh workflow run swift-test-package.yml --ref auto/update-linters\n"
           BODY+="\`\`\`\n"
diff --git a/dev.yml b/dev.yml
index ed91bf30e..9cc230a2a 100644
--- a/dev.yml
+++ b/dev.yml
@@ -384,10 +384,24 @@ commands:
           ../Scripts/xcode_run build CheckoutKitSwiftDemo
       test:
         desc: |
-          `dev swift test` - Run all tests for the ShopifyCheckoutKit-Package.
-          `dev swift test <test_class_name>` - Run only the specified test class.
+          `dev swift test` - Run all tests for the ShopifyCheckoutKit-Package and the sample apps.
+          `dev swift test <test_class_name>` - Run only the specified package test class.
+          `dev swift test sample [test_class_name]` - Run only the sample app test targets.
         syntax: "[test_class_name]"
-        run: cd platforms/swift && ./Scripts/xcode_run test ShopifyCheckoutKit-Package "$1"
+        run: |
+          set -e
+          cd platforms/swift
+          if [ -n "${1:-}" ]; then
+            ./Scripts/xcode_run test ShopifyCheckoutKit-Package "$1"
+          else
+            ./Scripts/xcode_run test ShopifyCheckoutKit-Package
+            ./Scripts/test_samples
+          fi
+        subcommands:
+          sample:
+            desc: Run the sample app test targets
+            syntax: "[test_class_name]"
+            run: cd platforms/swift && ./Scripts/test_samples "${1:-}"
       api:
         desc: Validate or update the public Swift API baseline (platforms/swift/api/*.json)
         run: |
diff --git a/platforms/android/samples/CheckoutKitAndroidDemo/app/src/test/java/com/shopify/checkoutkit/androiddemo/e2e/E2ETestIdsTest.kt b/platforms/android/samples/CheckoutKitAndroidDemo/app/src/test/java/com/shopify/checkoutkit/androiddemo/e2e/E2ETestIdsTest.kt
new file mode 100644
index 000000000..a4961f7d9
--- /dev/null
+++ b/platforms/android/samples/CheckoutKitAndroidDemo/app/src/test/java/com/shopify/checkoutkit/androiddemo/e2e/E2ETestIdsTest.kt
@@ -0,0 +1,11 @@
+package com.shopify.checkoutkit.androiddemo.e2e
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.Test
+
+class E2ETestIdsTest {
+    @Test
+    fun `app ready marker matches the maestro flows`() {
+        assertThat(E2ETestIds.APP_READY).isEqualTo("checkout-kit-sample-ready")
+    }
+}
diff --git a/platforms/react-native/sample/src/App.tsx b/platforms/react-native/sample/src/App.tsx
index f05730fbd..7088db8c7 100644
--- a/platforms/react-native/sample/src/App.tsx
+++ b/platforms/react-native/sample/src/App.tsx
@@ -50,7 +50,7 @@ import ErrorBoundary from './ErrorBoundary';
 import env from 'react-native-config';
 import {createDebugLogger} from './utils';
 import {useShopifyEventHandlers} from './hooks/useCheckoutEventHandlers';
-import {useE2ECartBootstrap} from './hooks/useE2ECartBootstrap';
+import {useE2ECartBootstrap} from './e2e/useE2ECartBootstrap';
 import {E2ETestIds} from './e2e/testIds';
 
 const log = createDebugLogger('ENV');
diff --git a/platforms/react-native/sample/src/linking/__tests__/cartBootstrap.test.ts b/platforms/react-native/sample/src/e2e/__tests__/cartBootstrap.test.ts
similarity index 100%
rename from platforms/react-native/sample/src/linking/__tests__/cartBootstrap.test.ts
rename to platforms/react-native/sample/src/e2e/__tests__/cartBootstrap.test.ts
diff --git a/platforms/react-native/sample/src/linking/cartBootstrap.ts b/platforms/react-native/sample/src/e2e/cartBootstrap.ts
similarity index 100%
rename from platforms/react-native/sample/src/linking/cartBootstrap.ts
rename to platforms/react-native/sample/src/e2e/cartBootstrap.ts
diff --git a/platforms/react-native/sample/src/hooks/useE2ECartBootstrap.ts b/platforms/react-native/sample/src/e2e/useE2ECartBootstrap.ts
similarity index 92%
rename from platforms/react-native/sample/src/hooks/useE2ECartBootstrap.ts
rename to platforms/react-native/sample/src/e2e/useE2ECartBootstrap.ts
index 35132b745..e75eecd8c 100644
--- a/platforms/react-native/sample/src/hooks/useE2ECartBootstrap.ts
+++ b/platforms/react-native/sample/src/e2e/useE2ECartBootstrap.ts
@@ -1,11 +1,8 @@
 import {useCallback} from 'react';
 import {Alert} from 'react-native';
 import {useCart} from '../context/Cart';
-import {
-  parseCartBootstrapLink,
-  type CartBootstrapLink,
-} from '../linking/cartBootstrap';
-import useShopify from './useShopify';
+import useShopify from '../hooks/useShopify';
+import {parseCartBootstrapLink, type CartBootstrapLink} from './cartBootstrap';
 
 type UseE2ECartBootstrapOptions = {
   onCartReady: () => void;
diff --git a/platforms/swift/Samples/CheckoutKitSwiftDemo/CheckoutKitSwiftDemoTests/E2E/E2ETestIdsTests.swift b/platforms/swift/Samples/CheckoutKitSwiftDemo/CheckoutKitSwiftDemoTests/E2E/E2ETestIdsTests.swift
new file mode 100644
index 000000000..4ddeb0562
--- /dev/null
+++ b/platforms/swift/Samples/CheckoutKitSwiftDemo/CheckoutKitSwiftDemoTests/E2E/E2ETestIdsTests.swift
@@ -0,0 +1,8 @@
+@testable import CheckoutKitSwiftDemo
+import XCTest
+
+class E2ETestIdsTests: XCTestCase {
+    func testAppReadyMarkerMatchesTheMaestroFlows() {
+        XCTAssertEqual(E2ETestIds.appReady, "checkout-kit-sample-ready")
+    }
+}
diff --git a/platforms/swift/Samples/CheckoutKitSwiftDemo/project.yml b/platforms/swift/Samples/CheckoutKitSwiftDemo/project.yml
index 8a5e97cb2..54193e7cf 100644
--- a/platforms/swift/Samples/CheckoutKitSwiftDemo/project.yml
+++ b/platforms/swift/Samples/CheckoutKitSwiftDemo/project.yml
@@ -19,10 +19,13 @@ schemes:
     build:
       targets:
         CheckoutKitSwiftDemo: all
+        CheckoutKitSwiftDemoTests: [test]
     run:
       config: Debug
     test:
       config: Debug
+      targets:
+        - CheckoutKitSwiftDemoTests
     profile:
       config: Release
     analyze:
@@ -47,7 +50,7 @@ targets:
     settings:
       base:
         PRODUCT_BUNDLE_IDENTIFIER: com.shopify.checkoutkit.swiftdemo
-        DEVELOPMENT_TEAM: A7XGC83MZE
+        DEVELOPMENT_TEAM: $(DEVELOPMENT_TEAM)
         SWIFT_VERSION: "6.0"
         SWIFT_STRICT_CONCURRENCY: complete
         SWIFT_TREAT_WARNINGS_AS_ERRORS: YES
@@ -128,3 +131,30 @@ targets:
         com.apple.developer.associated-domains:
           - webcredentials:$(STOREFRONT_DOMAIN)?mode=developer
           - applinks:$(STOREFRONT_DOMAIN)?mode=developer
+
+  CheckoutKitSwiftDemoTests:
+    type: bundle.unit-test
+    platform: iOS
+    sources:
+      - path: CheckoutKitSwiftDemoTests
+    dependencies:
+      - target: CheckoutKitSwiftDemo
+    configFiles:
+      Debug: Storefront.xcconfig
+      Release: Storefront.xcconfig
+    settings:
+      base:
+        PRODUCT_BUNDLE_IDENTIFIER: com.shopify.checkoutkit.swiftdemo.tests
+        DEVELOPMENT_TEAM: $(DEVELOPMENT_TEAM)
+        SWIFT_VERSION: "6.0"
+        SWIFT_STRICT_CONCURRENCY: complete
+        SWIFT_TREAT_WARNINGS_AS_ERRORS: YES
+        TEST_HOST: $(BUILT_PRODUCTS_DIR)/CheckoutKitSwiftDemo.app/$(BUNDLE_EXECUTABLE_FOLDER_PATH)/CheckoutKitSwiftDemo
+        BUNDLE_LOADER: $(TEST_HOST)
+        LD_RUNPATH_SEARCH_PATHS:
+          - $(inherited)
+          - "@executable_path/Frameworks"
+          - "@loader_path/Frameworks"
+    info:
+      path: CheckoutKitSwiftDemoTests/Info.plist
+      properties: {}
diff --git a/platforms/swift/Samples/ShopifyAcceleratedCheckoutsApp/project.yml b/platforms/swift/Samples/ShopifyAcceleratedCheckoutsApp/project.yml
index b266522b3..ab203735a 100644
--- a/platforms/swift/Samples/ShopifyAcceleratedCheckoutsApp/project.yml
+++ b/platforms/swift/Samples/ShopifyAcceleratedCheckoutsApp/project.yml
@@ -49,7 +49,7 @@ targets:
     settings:
       base:
         PRODUCT_BUNDLE_IDENTIFIER: com.shopify.example.ShopifyAcceleratedCheckoutsApp
-        DEVELOPMENT_TEAM: A7XGC83MZE
+        DEVELOPMENT_TEAM: $(DEVELOPMENT_TEAM)
         SWIFT_VERSION: "6.0"
         TARGETED_DEVICE_FAMILY: "1,2"
         MARKETING_VERSION: "1.0.1"
diff --git a/platforms/swift/Scripts/build_and_test_samples b/platforms/swift/Scripts/build_and_test_samples
new file mode 100755
index 000000000..e2d29fcb4
--- /dev/null
+++ b/platforms/swift/Scripts/build_and_test_samples
@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/../../.." && pwd)"
+SAMPLES_DIR="$SCRIPT_DIR/../Samples"
+
+if ! "$REPO_ROOT/scripts/setup_storefront_env" --check; then
+    echo "Run dev up from the repo root to sync sample app storefront configuration."
+    exit 1
+fi
+
+"$SCRIPT_DIR/generate_xcode_projects"
+
+cd "$SAMPLES_DIR"
+
+run_app() {
+    local app="$1"
+    local action="$2"
+
+    if [[ ! -f "$app/Storefront.xcconfig" ]]; then
+        echo "Missing Storefront.xcconfig for $app. Run dev up from the repo root."
+        exit 1
+    fi
+
+    "$SCRIPT_DIR/xcode_run" "$action" "$app"
+}
+
+run_app CheckoutKitSwiftDemo "clean build test"
+run_app ShopifyAcceleratedCheckoutsApp "clean build"
diff --git a/platforms/swift/Scripts/test_samples b/platforms/swift/Scripts/test_samples
new file mode 100755
index 000000000..8ad917cff
--- /dev/null
+++ b/platforms/swift/Scripts/test_samples
@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/../../.." && pwd)"
+SAMPLES_DIR="$SCRIPT_DIR/../Samples"
+TEST_FILTER="${1:-}"
+
+if ! "$REPO_ROOT/scripts/setup_storefront_env" --check; then
+    echo "Run dev up from the repo root to sync sample app storefront configuration."
+    exit 1
+fi
+
+"$SCRIPT_DIR/generate_xcode_projects"
+
+if [[ ! -f "$SAMPLES_DIR/CheckoutKitSwiftDemo/Storefront.xcconfig" ]]; then
+    echo "Missing Storefront.xcconfig for CheckoutKitSwiftDemo. Run dev up from the repo root."
+    exit 1
+fi
+
+if [[ -n "$TEST_FILTER" && "$TEST_FILTER" != */* ]]; then
+    TEST_FILTER="CheckoutKitSwiftDemoTests/$TEST_FILTER"
+fi
+
+cd "$SAMPLES_DIR"
+
+"$SCRIPT_DIR/xcode_run" test CheckoutKitSwiftDemo "$TEST_FILTER"
diff --git a/platforms/swift/Tests/ShopifyCheckoutKitTests/CheckoutWebViewTests.swift b/platforms/swift/Tests/ShopifyCheckoutKitTests/CheckoutWebViewTests.swift
index 26294508d..272ce8456 100644
--- a/platforms/swift/Tests/ShopifyCheckoutKitTests/CheckoutWebViewTests.swift
+++ b/platforms/swift/Tests/ShopifyCheckoutKitTests/CheckoutWebViewTests.swift
@@ -421,7 +421,7 @@ class CheckoutWebViewTests: XCTestCase {
 
         pollForInvalidation()
 
-        wait(for: [invalidated], timeout: 2)
+        wait(for: [invalidated], timeout: 3)
     }
 
     func testInvalidateDetachesCachedPreloadedWebView() {
@@ -864,7 +864,7 @@ class CheckoutWebViewTests: XCTestCase {
 
         view.userContentController(WKUserContentController(), didReceive: message)
 
-        await fulfillment(of: [responseSent], timeout: 1.0)
+        await fulfillment(of: [responseSent], timeout: 5.0)
         let response = try XCTUnwrap(MockCheckoutBridge.lastResponseBody)
         let parsed = try XCTUnwrap(try JSONSerialization.jsonObject(with: Data(response.utf8)) as? [String: Any])
         XCTAssertEqual(parsed["id"] as? String, "r")
diff --git a/scripts/setup_storefront_env b/scripts/setup_storefront_env
index f086f55a6..d0f72088a 100755
--- a/scripts/setup_storefront_env
+++ b/scripts/setup_storefront_env
@@ -226,6 +226,7 @@ root_has_canonical_keys() {
     STOREFRONT_DOMAIN \
     STOREFRONT_ACCESS_TOKEN \
     STOREFRONT_MERCHANT_IDENTIFIER \
+    DEVELOPMENT_TEAM \
     API_VERSION \
     CUSTOMER_ACCOUNT_API_CLIENT_ID \
     CUSTOMER_ACCOUNT_API_SHOP_ID \
@@ -454,6 +455,11 @@ load_values() {
   PROVINCE_VALUE="$(root_or_source_value PROVINCE "$(env_fallback PROVINCE)" "$(read_env_value PROVINCE "$REACT_NATIVE_ENV")" "$(read_env_value PROVINCE "$SWIFT_DEMO_XCCONFIG")" "ON")"
   ZIP_VALUE="$(root_or_source_value ZIP "$(env_fallback ZIP)" "$(read_env_value ZIP "$REACT_NATIVE_ENV")" "$(read_env_value ZIP "$SWIFT_DEMO_XCCONFIG")" "M5V 1M7")"
   PHONE_VALUE="$(root_or_source_value PHONE "$(env_fallback PHONE)" "$(read_env_value PHONE "$ANDROID_ENV")" "$(read_env_value PREFILL_PHONE "$ANDROID_ENV")" "$(read_env_value PHONE "$REACT_NATIVE_ENV")" "$(read_env_value PHONE "$SWIFT_DEMO_XCCONFIG")" "+14165550100")"
+
+  # No default and no generated-file fallback: a cleared DEVELOPMENT_TEAM stays cleared, and
+  # the Xcode build fails at signing until the developer supplies their own team.
+  DEVELOPMENT_TEAM_VALUE="$(root_or_source_nonempty_value DEVELOPMENT_TEAM \
+    "$(env_fallback DEVELOPMENT_TEAM)")"
 }
 
 collect_missing_values() {
@@ -507,6 +513,12 @@ EOF
   write_env_assignment STOREFRONT_MERCHANT_IDENTIFIER "$STOREFRONT_MERCHANT_IDENTIFIER_VALUE"
   cat <<EOF
 
+# Apple team that signs the Swift samples. Set your own team id, or the Xcode build
+# fails at signing. A blank value stays blank; setup applies no default team.
+EOF
+  write_env_assignment DEVELOPMENT_TEAM "$DEVELOPMENT_TEAM_VALUE"
+  cat <<EOF
+
 # Storefront API version
 EOF
   write_env_assignment API_VERSION "$API_VERSION_VALUE"
@@ -611,6 +623,7 @@ EOF
 
 generate_swift_demo_xcconfig() {
   generate_xcconfig_header
+  write_xcconfig_assignment DEVELOPMENT_TEAM "$DEVELOPMENT_TEAM_VALUE"
   write_xcconfig_assignment STOREFRONT_DOMAIN "$STOREFRONT_DOMAIN_VALUE"
   write_xcconfig_assignment STOREFRONT_ACCESS_TOKEN "$STOREFRONT_ACCESS_TOKEN_VALUE"
   write_xcconfig_assignment STOREFRONT_MERCHANT_IDENTIFIER "$STOREFRONT_MERCHANT_IDENTIFIER_VALUE"
@@ -642,6 +655,7 @@ EOF
 
 generate_swift_accelerated_xcconfig() {
   generate_xcconfig_header
+  write_xcconfig_assignment DEVELOPMENT_TEAM "$DEVELOPMENT_TEAM_VALUE"
   write_xcconfig_assignment STOREFRONT_DOMAIN "$STOREFRONT_DOMAIN_VALUE"
   write_xcconfig_assignment STOREFRONT_ACCESS_TOKEN "$STOREFRONT_ACCESS_TOKEN_VALUE"
   write_xcconfig_assignment API_VERSION "$API_VERSION_VALUE"
diff --git a/scripts/test_setup_storefront_env b/scripts/test_setup_storefront_env
index b1c950143..50ced5973 100755
--- a/scripts/test_setup_storefront_env
+++ b/scripts/test_setup_storefront_env
@@ -245,6 +245,78 @@ EOF
   assert_contains "$fixture/platforms/android/samples/CheckoutKitAndroidDemo/.env" "/2026-04/graphql"
 }
 
+# project.yml reads $(DEVELOPMENT_TEAM) from the generated xcconfig. Setup applies no
+# default team, so a clone with no DEVELOPMENT_TEAM in .env gets a blank one and fails at
+# signing. A value in .env has to win, and clearing that value has to clear the xcconfig
+# again rather than recover the previous team from the generated file.
+test_development_team_follows_env_and_clears() {
+  local fixture output demo_xcconfig accelerated_xcconfig
+  fixture="$(make_fixture)"
+  output="$fixture/output.log"
+  demo_xcconfig="$fixture/platforms/swift/Samples/CheckoutKitSwiftDemo/Storefront.xcconfig"
+  accelerated_xcconfig="$fixture/platforms/swift/Samples/ShopifyAcceleratedCheckoutsApp/Storefront.xcconfig"
+
+  STOREFRONT_DOMAIN=synthetic-store.example.myshopify.com \
+    STOREFRONT_ACCESS_TOKEN=synthetic-token \
+    "$fixture/scripts/setup_storefront_env" --skip-optional-prompts >"$output" 2>&1
+
+  assert_output_is_sanitized "$output"
+  assert_contains "$demo_xcconfig" "DEVELOPMENT_TEAM ="
+  assert_not_contains "$demo_xcconfig" "DEVELOPMENT_TEAM = A7XGC83MZE"
+  # .env has to carry the key as well, or the next normalizing rewrite drops the override.
+  assert_contains "$fixture/.env" "DEVELOPMENT_TEAM="
+
+  awk '
+    /^DEVELOPMENT_TEAM=/ { print "DEVELOPMENT_TEAM=SYNTHETIC9"; next }
+    { print }
+  ' "$fixture/.env" >"$fixture/.env.next"
+  mv "$fixture/.env.next" "$fixture/.env"
+
+  "$fixture/scripts/setup_storefront_env" --skip-optional-prompts >"$output" 2>&1
+  assert_output_is_sanitized "$output"
+  assert_contains "$demo_xcconfig" "DEVELOPMENT_TEAM = SYNTHETIC9"
+  assert_contains "$accelerated_xcconfig" "DEVELOPMENT_TEAM = SYNTHETIC9"
+  assert_contains "$fixture/.env" "DEVELOPMENT_TEAM=SYNTHETIC9"
+
+  awk '
+    /^DEVELOPMENT_TEAM=/ { print "DEVELOPMENT_TEAM="; next }
+    { print }
+  ' "$fixture/.env" >"$fixture/.env.next"
+  mv "$fixture/.env.next" "$fixture/.env"
+
+  "$fixture/scripts/setup_storefront_env" --skip-optional-prompts >"$output" 2>&1
+  assert_output_is_sanitized "$output"
+  assert_not_contains "$demo_xcconfig" "SYNTHETIC9"
+  assert_not_contains "$accelerated_xcconfig" "SYNTHETIC9"
+}
+
+# A clone whose .env predates DEVELOPMENT_TEAM holds every other canonical key, so the
+# normalizing rewrite has to notice the one absent key. Otherwise dev up leaves .env alone
+# and the developer never sees the key they are meant to override.
+test_development_team_is_added_to_an_existing_env() {
+  local fixture output accelerated_xcconfig
+  fixture="$(make_fixture)"
+  output="$fixture/output.log"
+  accelerated_xcconfig="$fixture/platforms/swift/Samples/ShopifyAcceleratedCheckoutsApp/Storefront.xcconfig"
+
+  STOREFRONT_DOMAIN=synthetic-store.example.myshopify.com \
+    STOREFRONT_ACCESS_TOKEN=synthetic-token \
+    "$fixture/scripts/setup_storefront_env" --skip-optional-prompts >"$output" 2>&1
+
+  grep -v '^DEVELOPMENT_TEAM=' "$fixture/.env" >"$fixture/.env.next"
+  mv "$fixture/.env.next" "$fixture/.env"
+
+  if "$fixture/scripts/setup_storefront_env" --check >"$output" 2>&1; then
+    fail "root .env without DEVELOPMENT_TEAM passed --check"
+  fi
+  assert_output_is_sanitized "$output"
+
+  "$fixture/scripts/setup_storefront_env" --skip-optional-prompts >"$output" 2>&1
+  assert_output_is_sanitized "$output"
+  assert_contains "$fixture/.env" "DEVELOPMENT_TEAM="
+  assert_contains "$accelerated_xcconfig" "DEVELOPMENT_TEAM ="
+}
+
 test_migration_from_platform_config() {
   local fixture output android_env
   fixture="$(make_fixture)"
@@ -277,6 +349,8 @@ test_required_values_only
 test_optional_sync_updates_blank_optional_values_after_required_setup
 test_normalizes_existing_root_env
 test_blank_customer_account_api_version_defaults
+test_development_team_follows_env_and_clears
+test_development_team_is_added_to_an_existing_env
 test_migration_from_platform_config
 
 echo "setup_storefront_env synthetic tests passed."