diff --git a/Packages/BitMatchEngine/Tests/BitMatchEngineTests/Issue10ExFATHandoffTests.swift b/Packages/BitMatchEngine/Tests/BitMatchEngineTests/Issue10ExFATHandoffTests.swift
index 59cb9d0b..160417ec 100644
--- a/Packages/BitMatchEngine/Tests/BitMatchEngineTests/Issue10ExFATHandoffTests.swift
+++ b/Packages/BitMatchEngine/Tests/BitMatchEngineTests/Issue10ExFATHandoffTests.swift
@@ -66,8 +66,13 @@ final class Issue10ExFATHandoffTests: XCTestCase {
         // File output avoids pipe-buffer deadlocks while waiting for hdiutil.
         process.standardOutput = handle
         process.standardError = handle
+        let action = arguments.first ?? "unknown"
+        let started = ProcessInfo.processInfo.systemUptime
+        FileHandle.standardError.write(Data("Issue10 exFAT fixture: hdiutil \(action) started (\(scratch.lastPathComponent))\n".utf8))
         try process.run()
         process.waitUntilExit()
+        let elapsed = ProcessInfo.processInfo.systemUptime - started
+        FileHandle.standardError.write(Data("Issue10 exFAT fixture: hdiutil \(action) exited \(process.terminationStatus) after \(String(format: "%.1f", elapsed))s\n".utf8))
         guard process.terminationStatus == 0 else {
             let detail = (try? String(contentsOf: log, encoding: .utf8)) ?? "No output"
             throw NSError(domain: "Issue10Probe.hdiutil", code: Int(process.terminationStatus),
diff --git a/test.sh b/test.sh
index 73d8f582..e7fb36be 100755
--- a/test.sh
+++ b/test.sh
@@ -30,13 +30,18 @@ case "$JOB" in
   engine-test)
     # Keep independent disk fixtures from racing short setup deadlines. Each
     # test still exercises its own concurrent copy/verify workers.
-    # Match the Apple Silicon test host to the package's arm64 bundle. Newer
-    # Xcode hosts may otherwise choose arm64e and refuse to load XCTest.
-    if [[ "$(uname -m)" == arm64 ]]; then
-      arch -arm64 swift test --package-path "$ROOT/Packages/BitMatchEngine" --build-system native --no-parallel
-    else
-      swift test --package-path "$ROOT/Packages/BitMatchEngine" --build-system native --no-parallel
-    fi
+    # Xcode 27 can choose an arm64e host for a mixed SwiftPM test run and fail
+    # to load the package's arm64-only XCTest bundle, while Swift Testing still
+    # runs. Run each test framework explicitly so neither can be omitted.
+    run_engine_tests() {
+      if [[ "$(uname -m)" == arm64 ]]; then
+        arch -arm64 swift test --package-path "$ROOT/Packages/BitMatchEngine" --build-system native --no-parallel "$@"
+      else
+        swift test --package-path "$ROOT/Packages/BitMatchEngine" --build-system native --no-parallel "$@"
+      fi
+    }
+    run_engine_tests --disable-swift-testing
+    run_engine_tests --disable-xctest
     ;;
   release-builds)
     run_xcodebuild mac-release build -scheme BitMatch -configuration Release -destination 'platform=macOS'