diff --git a/.github/skills/sil-library-reuse/SKILL.md b/.github/skills/sil-library-reuse/SKILL.md
new file mode 100644
index 0000000000..17a5c600b4
--- /dev/null
+++ b/.github/skills/sil-library-reuse/SKILL.md
@@ -0,0 +1,349 @@
+---
+name: sil-library-reuse
+description: >
+  Reuse lower-level SIL libraries before writing custom helpers in FieldWorks.
+  Use this whenever a task touches file or directory I/O, locked-file retries,
+  paths or URIs, writing systems, keyboards, LCM caches/project IDs/service
+  locators, linked files/media/config paths, localization, LIFT/import/export,
+  FLExBridge or Chorus sync/merge flows, analytics/telemetry, morphology or
+  NLP, scripture/Paratext integration, or SIL test helpers. Even for small
+   fixes, check the package families and repo patterns here first. If any
+   guidance here proves inaccurate or stale, revalidate against current
+   FieldWorks package references, local package metadata, and upstream repos,
+   then update this skill so it stays current.
+---
+
+# SIL Library Reuse
+
+FieldWorks already depends on SIL packages that solve many of the "small
+helper" problems agents are tempted to rebuild. Start here before adding new
+filesystem wrappers, cache bootstraps, writing-system plumbing, localization
+hooks, bridge calls, or parser code.
+
+## Staying Current
+
+If you find this to be inaccurate, treat that as a maintenance signal, not a
+reason to ignore the skill. SIL package versions, upstream repo layouts, and
+public API names change over time. Revalidate the claim against the current
+FieldWorks package references, installed package metadata, local usage, and
+upstream repos, then update this skill in the same change when practical. If
+you cannot update it, call out the stale item clearly in your final response.
+
+## Workflow
+
+1. Identify the package family from the touched namespace or project file. If
+   the package or version is unclear, check
+   [Directory.Packages.props](../../../Directory.Packages.props) and
+   [Build/SilVersions.props](../../../Build/SilVersions.props).
+2. Search FieldWorks first for the concrete helper or namespace and copy the
+   existing local pattern.
+3. If local usage is thin or the name is unfamiliar, open the upstream repo
+   links below. Do not assume Context7 covers these packages well.
+4. Prefer the library helper over custom code when it already handles retries,
+   path normalization, cache setup, localization metadata, sync boundaries, or
+   corpus parsing.
+5. Keep FieldWorks constraints intact: .NET Framework 4.8, C# 7.3, `.resx` for
+   user-facing strings, registration-free COM, and repo build/test scripts.
+
+## Good First Searches
+
+- `RobustIO|RobustFile|RetryUtility|Keyboard.Controller|FileLocationUtilities`
+- `LcmCache|TestProjectId|SimpleProjectId|ServiceLocator.GetInstance|LcmFileHelper|WritingSystemManager|FileUtils`
+- `LocalizationManagerWinforms|L10NExtender`
+- `Analytics.Track|Analytics.ReportException|FLExBridgeHelper`
+- `Paratext|IParatextHelper|Usfm|Usx|Morpher|SIL.Machine`
+
+## Package Family Map
+
+### `libpalaso`
+
+Packages:
+`SIL.Core`, `SIL.Core.Desktop`, `SIL.Archiving`, `SIL.Lexicon`, `SIL.Lift`,
+`SIL.Media`, `SIL.Scripture`, `SIL.TestUtilities`, `SIL.Windows.Forms*`,
+`SIL.WritingSystems`
+
+Use for:
+filesystem resilience, path helpers, retry loops, desktop file helpers,
+writing systems, keyboards, LIFT processing, archiving, and test temp-file
+helpers.
+
+FieldWorks usage anchors:
+
+- [Src/Common/RootSite/RootSiteTests/RealDataTestsBase.cs](../../../Src/Common/RootSite/RootSiteTests/RealDataTestsBase.cs)
+- [Src/xWorks/FwXWindow.cs](../../../Src/xWorks/FwXWindow.cs)
+- [Src/Common/SimpleRootSite/EditingHelper.cs](../../../Src/Common/SimpleRootSite/EditingHelper.cs)
+
+Main APIs to look for first:
+
+- `RobustIO.DeleteDirectoryAndContents`
+- `RobustIO.MoveDirectory`
+- `RobustIO.RequireThatDirectoryExists`
+- `RobustFile.Copy`
+- `RobustFile.WriteAllBytes`
+- `RobustFile.ReplaceByCopyDelete`
+- `RetryUtility.Retry`
+- `PathHelper.NormalizePath`
+- `PathHelper.AreOnSameVolume`
+- `PathHelper.StripFilePrefix`
+- `FileLocationUtilities.LocateExecutable`
+- `FileLocationUtilities.LocateInProgramFiles`
+- `PathUtilities.SelectFileInExplorer`
+- `PathUtilities.OpenDirectoryInExplorer`
+- `WritingSystemDefinition`
+- `IWritingSystemRepository`
+- `Keyboard.Controller`
+- `KeyboardController`
+- `LiftSorter.SortLiftFile`
+- `LiftPreparer.MigrateLiftFile`
+- `WritingSystemsInLiftFileHelper`
+- `ArchivingFileSystem`
+
+Upstream repo:
+
+- [libpalaso](https://github.com/sillsdev/libpalaso)
+- [SIL.Core/IO](https://github.com/sillsdev/libpalaso/tree/master/SIL.Core/IO)
+- [SIL.Core.Desktop/IO](https://github.com/sillsdev/libpalaso/tree/master/SIL.Core.Desktop/IO)
+- [SIL.WritingSystems](https://github.com/sillsdev/libpalaso/tree/master/SIL.WritingSystems)
+- [SIL.Windows.Forms.Keyboarding](https://github.com/sillsdev/libpalaso/tree/master/SIL.Windows.Forms.Keyboarding)
+- [SIL.Windows.Forms.WritingSystems](https://github.com/sillsdev/libpalaso/tree/master/SIL.Windows.Forms.WritingSystems)
+- [SIL.Lift](https://github.com/sillsdev/libpalaso/tree/master/SIL.Lift)
+- [SIL.Archiving](https://github.com/sillsdev/libpalaso/tree/master/SIL.Archiving)
+- [SIL.TestUtilities](https://github.com/sillsdev/libpalaso/tree/master/SIL.TestUtilities)
+
+### `liblcm`
+
+Packages:
+`SIL.LCModel`, `SIL.LCModel.Core`, `SIL.LCModel.Utils`,
+`SIL.LCModel.FixData`, `SIL.LCModel.Tests`
+
+Use for:
+LCM cache creation, project IDs, service location, writing-system managers,
+linked/media/config paths, imports, migrations, and repository/factory access.
+
+FieldWorks usage anchors:
+
+- [Src/Common/RootSite/RootSiteTests/RealDataTestsBase.cs](../../../Src/Common/RootSite/RootSiteTests/RealDataTestsBase.cs)
+- [Src/xWorks/FwXWindow.cs](../../../Src/xWorks/FwXWindow.cs)
+- [Src/xWorks/xWorksTests/ExportDialogTests.cs](../../../Src/xWorks/xWorksTests/ExportDialogTests.cs)
+
+Main APIs to look for first:
+
+- `LcmCache.CreateCacheFromExistingData`
+- `LcmCache.CreateCacheWithNewBlankLangProj`
+- `ILcmServiceLocator`
+- `ServiceLocator.GetInstance<T>()`
+- `IProjectIdentifier`
+- `SimpleProjectId`
+- `TestProjectId`
+- `LcmFileHelper.GetConfigSettingsDir`
+- `LcmFileHelper.GetDefaultLinkedFilesDir`
+- `LcmFileHelper.GetDefaultMediaDir`
+- `LcmFileHelper.GetWritingSystemDir`
+- `LinkedFilesRelativePathHelper`
+- `FileUtils.FileExists`
+- `FileUtils.DirectoryExists`
+- `FileUtils.EnsureDirectoryExists`
+- `FileUtils.StripFilePrefix`
+- `FileUtils.ChangePathToPlatform`
+- `WritingSystemManager`
+- `UnitOfWorkService`
+
+Upstream repo:
+
+- [liblcm](https://github.com/sillsdev/liblcm)
+- [src/SIL.LCModel](https://github.com/sillsdev/liblcm/tree/master/src/SIL.LCModel)
+- [Infrastructure](https://github.com/sillsdev/liblcm/tree/master/src/SIL.LCModel/Infrastructure)
+- [DomainServices](https://github.com/sillsdev/liblcm/tree/master/src/SIL.LCModel/DomainServices)
+- [src/SIL.LCModel.Core](https://github.com/sillsdev/liblcm/tree/master/src/SIL.LCModel.Core)
+- [src/SIL.LCModel.Utils](https://github.com/sillsdev/liblcm/tree/master/src/SIL.LCModel.Utils)
+
+### `l10nsharp`
+
+Packages:
+`L10NSharp`, `L10NSharp.Windows.Forms`
+
+Use for:
+runtime WinForms localization, XLIFF-backed string management, control
+metadata, and language switching.
+
+FieldWorks usage anchors:
+
+- [Src/Common/FieldWorks/FieldWorks.cs](../../../Src/Common/FieldWorks/FieldWorks.cs)
+
+Main APIs to look for first:
+
+- `LocalizationManagerWinforms.Create`
+- `LocalizationManagerWinforms.SetUILanguage`
+- `LocalizationManagerWinforms.ReapplyLocalizationsToAllObjects`
+- `L10NExtender`
+- `ILocalizableComponent`
+- `LocalizingInfoWinforms`
+- `LocalizationCategory`
+- `XliffLocalizationManagerWinforms`
+
+Upstream repo:
+
+- [l10nsharp](https://github.com/sillsdev/l10nsharp)
+- [src/L10NSharp](https://github.com/sillsdev/l10nsharp/tree/master/src/L10NSharp)
+- [src/L10NSharp.Windows.Forms](https://github.com/sillsdev/l10nsharp/tree/master/src/L10NSharp.Windows.Forms)
+- [UIComponents](https://github.com/sillsdev/l10nsharp/tree/master/src/L10NSharp.Windows.Forms/UIComponents)
+- [SampleApp](https://github.com/sillsdev/l10nsharp/tree/master/src/SampleApp)
+
+### `desktopanalytics.net`
+
+Packages:
+`SIL.DesktopAnalytics`
+
+Use for:
+telemetry, consent-aware tracking, exception reporting, and application-level
+analytics properties.
+
+FieldWorks usage anchors:
+
+- [Src/Common/FieldWorks/FieldWorks.cs](../../../Src/Common/FieldWorks/FieldWorks.cs)
+- [Src/Common/FwUtils/TrackingHelper.cs](../../../Src/Common/FwUtils/TrackingHelper.cs)
+- [Src/LexText/LexTextDll/AreaListener.cs](../../../Src/LexText/LexTextDll/AreaListener.cs)
+
+Main APIs to look for first:
+
+- `Analytics.Track`
+- `Analytics.ReportException`
+- `Analytics.AllowTracking`
+- `Analytics.IdentifyUpdate`
+- `Analytics.SetApplicationProperty`
+- `Analytics.FlushClient`
+- `UserInfo.CreateSanitized`
+
+Upstream repo:
+
+- [DesktopAnalytics.net](https://github.com/sillsdev/DesktopAnalytics.net)
+- [Analytics.cs](https://github.com/sillsdev/DesktopAnalytics.net/blob/master/src/DesktopAnalytics/Analytics.cs)
+- [UserInfo.cs](https://github.com/sillsdev/DesktopAnalytics.net/blob/master/src/DesktopAnalytics/UserInfo.cs)
+
+### `ipcframework` and `chorus`
+
+Packages:
+`SIL.FLExBridge.IPCFramework`, `SIL.Chorus.App`, `SIL.Chorus.LibChorus`,
+`SIL.Chorus.L10ns`
+
+Use for:
+FLExBridge launch/obtain/send-receive flows, IPC contracts, sync/merge
+orchestration, file-type handlers, and merge/conflict notes.
+
+FieldWorks usage anchors:
+
+- [Src/Common/FwUtils/FLExBridgeHelper.cs](../../../Src/Common/FwUtils/FLExBridgeHelper.cs)
+- [Src/LexText/Lexicon/FLExBridgeListener.cs](../../../Src/LexText/Lexicon/FLExBridgeListener.cs)
+- [Src/Common/Controls/FwControls/ObtainProjectMethod.cs](../../../Src/Common/Controls/FwControls/ObtainProjectMethod.cs)
+
+Start with the local wrapper first:
+
+- `FLExBridgeHelper.LaunchFieldworksBridge`
+- `FLExBridgeHelper.DoesProjectHaveFlexRepo`
+- `FLExBridgeHelper.DoesProjectHaveLiftRepo`
+- `FLExBridgeHelper.IsFlexBridgeInstalled`
+- `FLExBridgeHelper.FullFieldWorksBridgePath`
+
+Then inspect upstream helpers if the change crosses the boundary:
+
+- `IPCClientFactory.Create`
+- `IPCHostFactory.Create`
+- `IIPCClient.RemoteCall`
+- `IIPCHost.Initialize`
+- `Synchronizer`
+- `XmlMergeService.Do3WayMerge`
+- `MergeOrder`
+- `ElementStrategy`
+- `IChorusFileTypeHandler`
+- `ChorusNotesMergeEventListener`
+
+Upstream repos:
+
+- [ipcframework](https://github.com/sillsdev/ipcframework)
+- [IPCFramework/IPCInterfaces.cs](https://github.com/sillsdev/ipcframework/tree/master/IPCFramework/IPCInterfaces.cs)
+- [IPCClientFactory.cs](https://github.com/sillsdev/ipcframework/tree/master/IPCFramework/IPCClientFactory.cs)
+- [IPCHostFactory.cs](https://github.com/sillsdev/ipcframework/tree/master/IPCFramework/IPCHostFactory.cs)
+- [ServerProgram/FLExBridgeHelper.cs](https://github.com/sillsdev/ipcframework/tree/master/ServerProgram/FLExBridgeHelper.cs)
+- [ClientProgram/FLExConnectionHelper.cs](https://github.com/sillsdev/ipcframework/tree/master/ClientProgram/FLExConnectionHelper.cs)
+- [chorus](https://github.com/sillsdev/chorus)
+- [src/LibChorus/sync](https://github.com/sillsdev/chorus/tree/master/src/LibChorus/sync)
+- [src/LibChorus/merge/xml/generic](https://github.com/sillsdev/chorus/tree/master/src/LibChorus/merge/xml/generic)
+- [src/LibChorus/FileTypeHandlers](https://github.com/sillsdev/chorus/tree/master/src/LibChorus/FileTypeHandlers)
+- [src/LibChorus/VcsDrivers/Mercurial](https://github.com/sillsdev/chorus/tree/master/src/LibChorus/VcsDrivers/Mercurial)
+- [src/LibChorus/notes](https://github.com/sillsdev/chorus/tree/master/src/LibChorus/notes)
+
+### `machine`
+
+Packages:
+`SIL.Machine`, `SIL.Machine.Morphology.HermitCrab`
+
+Use for:
+morphology, feature-structure-based NLP, text corpora, USFM/USX parsing, and
+alignment. Direct FieldWorks usage is light today; consult this before
+inventing parser or analysis code.
+
+Main APIs to look for first:
+
+- `Morpher.ParseWord`
+- `Morpher.GenerateWords`
+- `XmlLanguageLoader`
+- `TraceManager`
+- `FeatureStruct`
+- `ParatextTextCorpus`
+- `UsxFileTextCorpus`
+- `UsfmParser`
+- `CorporaUtils`
+
+Upstream repo:
+
+- [machine](https://github.com/sillsdev/machine)
+- [src/SIL.Machine](https://github.com/sillsdev/machine/tree/master/src/SIL.Machine)
+- [src/SIL.Machine.Morphology.HermitCrab](https://github.com/sillsdev/machine/tree/master/src/SIL.Machine.Morphology.HermitCrab)
+- [src/SIL.Machine.Translation.Thot](https://github.com/sillsdev/machine/tree/master/src/SIL.Machine.Translation.Thot)
+
+### `Paratext`
+
+Packages:
+`SIL.ParatextShared`, `ParatextData`
+
+Use for:
+Scripture project access, verse references, plugin integration, USFM tokens,
+and Paratext interoperability.
+
+FieldWorks usage anchors:
+
+- [Src/Common/ScriptureUtils/ScriptureUtilsTests/ParatextHelperTests.cs](../../../Src/Common/ScriptureUtils/ScriptureUtilsTests/ParatextHelperTests.cs)
+- `Paratext8Plugin` projects and helpers
+
+Important caveat:
+`SIL.ParatextShared` source for the legacy package used by FieldWorks is not
+publicly available. Use the public docs and demo plugins instead of hunting
+for a missing source tree.
+
+Public docs and references:
+
+- [Paratext demo plugins](https://github.com/ubsicap/paratext_demo_plugins)
+- [Full API documentation wiki](https://github.com/ubsicap/paratext_demo_plugins/wiki/Full-API-Documentation)
+- [SIL.ParatextShared 7.4.0.1](https://www.nuget.org/packages/SIL.ParatextShared/7.4.0.1)
+
+Useful API names in the public docs:
+
+- `IProject`
+- `IReadOnlyProject`
+- `IVerseRef`
+- `IUSFMToken`
+- `IUSFMMarkerToken`
+- `IScriptureTextSelection`
+- `IBiblicalTerm`
+- `IProjectNote`
+
+## Biases To Keep
+
+- Prefer `RobustIO` or `RobustFile` over ad hoc delete/retry loops.
+- Prefer `LcmCache`, `TestProjectId`, `ServiceLocator.GetInstance<T>()`, and
+  `LcmFileHelper` over custom LCM bootstrapping or path math.
+- Prefer `LocalizationManagerWinforms` over ad hoc runtime localization state.
+- Prefer `FLExBridgeHelper` over direct IPC calls from new UI code.
+- Prefer existing analytics calls or wrappers over one-off telemetry clients.
+- When a repo search comes up empty, switch from keyword search to
+  symbol/reference navigation before deciding the helper does not exist.
\ No newline at end of file
diff --git a/Src/Common/RootSite/RootSiteTests/RealDataTestsBase.cs b/Src/Common/RootSite/RootSiteTests/RealDataTestsBase.cs
index d3327eaeda..8475864706 100644
--- a/Src/Common/RootSite/RootSiteTests/RealDataTestsBase.cs
+++ b/Src/Common/RootSite/RootSiteTests/RealDataTestsBase.cs
@@ -1,8 +1,10 @@
 using System;
 using System.IO;
+using System.Threading;
 using NUnit.Framework;
-using SIL.FieldWorks.FwCoreDlgs;
 using SIL.FieldWorks.Common.FwUtils;
+using SIL.FieldWorks.FwCoreDlgs;
+using SIL.IO;
 using SIL.LCModel;
 using SIL.LCModel.Core.KernelInterfaces;
 using SIL.LCModel.Infrastructure;
@@ -18,64 +20,93 @@ namespace SIL.FieldWorks.Common.RootSites.RootSiteTests
 	[TestFixture]
 	public abstract class RealDataTestsBase
 	{
+		private const string ReusableProjectName = "integration_test_data";
+		private const string ProjectMutexName =
+			@"Local\FieldWorks.RealDataTests.integration_test_data";
+		private const string TestProjectSentinelFileName = ".fieldworks-real-data-test-project";
+
 		protected FwNewLangProjectModel m_model;
 		protected LcmCache Cache;
 		protected string m_dbName;
+		private string m_projectDirectory;
+		private Mutex m_projectMutex;
 
 		[SetUp]
 		public virtual void TestSetup()
 		{
-			m_dbName = "RealDataTest_" + Guid.NewGuid().ToString("N");
-			var dbPath = DbFilename(m_dbName);
-			if (File.Exists(dbPath))
-				File.Delete(dbPath);
+			m_dbName = ReusableProjectName;
+			m_projectDirectory = DbDirectory(m_dbName);
+			AcquireProjectMutex();
 
-			// Init New Lang Project Model (headless)
-			m_model = new FwNewLangProjectModel(true)
+			try
 			{
-				LoadProjectNameSetup = () => { },
-				LoadVernacularSetup = () => { },
-				LoadAnalysisSetup = () => { },
-				AnthroModel = new FwChooseAnthroListModel { CurrentList = FwChooseAnthroListModel.ListChoice.UserDef }
-			};
+				DeleteProjectDirectory(m_projectDirectory);
 
-			string createdPath;
-			using (var threadHelper = new ThreadHelper())
-			{
-				m_model.ProjectName = m_dbName;
-				m_model.Next(); // To Vernacular WS Setup
-				m_model.SetDefaultWs(new LanguageInfo { LanguageTag = "qaa", DesiredName = "Vernacular" });
-				m_model.Next(); // To Analysis WS Setup
-				m_model.SetDefaultWs(new LanguageInfo { LanguageTag = "en", DesiredName = "English" });
-				createdPath = m_model.CreateNewLangProj(new DummyProgressDlg(), threadHelper);
-			}
+				m_model = new FwNewLangProjectModel(true)
+				{
+					LoadProjectNameSetup = () => { },
+					LoadVernacularSetup = () => { },
+					LoadAnalysisSetup = () => { },
+					AnthroModel = new FwChooseAnthroListModel
+					{
+						CurrentList = FwChooseAnthroListModel.ListChoice.UserDef,
+					},
+				};
 
-			// Load the cache from the newly created .fwdata file
-			Cache = LcmCache.CreateCacheFromExistingData(
-				new TestProjectId(BackendProviderType.kXMLWithMemoryOnlyWsMgr, createdPath),
-				"en",
-				new DummyLcmUI(),
-				FwDirectoryFinder.LcmDirectories,
-				new LcmSettings(),
-				new DummyProgressDlg());
+				string createdPath;
+				using (var threadHelper = new ThreadHelper())
+				{
+					m_model.ProjectName = m_dbName;
+					m_model.Next(); // To Vernacular WS Setup
+					m_model.SetDefaultWs(
+						new LanguageInfo { LanguageTag = "qaa", DesiredName = "Vernacular" }
+					);
+					m_model.Next(); // To Analysis WS Setup
+					m_model.SetDefaultWs(
+						new LanguageInfo { LanguageTag = "en", DesiredName = "English" }
+					);
+					createdPath = m_model.CreateNewLangProj(new DummyProgressDlg(), threadHelper);
+					m_projectDirectory = GetProjectDirectory(createdPath);
+					WriteTestProjectSentinel(m_projectDirectory);
+				}
 
-			try
-			{
-				using (var undoWatcher = new UndoableUnitOfWorkHelper(Cache.ActionHandlerAccessor, "Test Setup", "Undo Test Setup"))
+				Cache = LcmCache.CreateCacheFromExistingData(
+					new TestProjectId(BackendProviderType.kXMLWithMemoryOnlyWsMgr, createdPath),
+					"en",
+					new DummyLcmUI(),
+					FwDirectoryFinder.LcmDirectories,
+					new LcmSettings(),
+					new DummyProgressDlg()
+				);
+
+				try
 				{
-					InitializeProjectData();
-					CreateTestData();
-					undoWatcher.RollBack = false;
+					using (
+						var undoWatcher = new UndoableUnitOfWorkHelper(
+							Cache.ActionHandlerAccessor,
+							"Test Setup",
+							"Undo Test Setup"
+						)
+					)
+					{
+						InitializeProjectData();
+						CreateTestData();
+						undoWatcher.RollBack = false;
+					}
+				}
+				catch (Exception)
+				{
+					DisposeCache();
+					throw;
 				}
 			}
 			catch (Exception)
 			{
-				// If setup fails, ensure we don't leave a locked DB
-				if (Cache != null)
-				{
-					Cache.Dispose();
-					Cache = null;
-				}
+				RunSetupFailureCleanup(
+					TryDisposeCacheAfterSetupFailure,
+					TryDeleteProjectDirectoryAfterSetupFailure,
+					ReleaseProjectMutex
+				);
 				throw;
 			}
 		}
@@ -93,21 +124,245 @@ protected virtual void CreateTestData()
 		[TearDown]
 		public virtual void TestTearDown()
 		{
-			if (Cache != null)
+			try
+			{
+				DisposeCache();
+				DeleteProjectDirectory(m_projectDirectory);
+			}
+			finally
+			{
+				m_projectDirectory = null;
+				ReleaseProjectMutex();
+			}
+		}
+
+		protected string DbDirectory(string name)
+		{
+			return Path.Combine(FwDirectoryFinder.ProjectsDirectory, name);
+		}
+
+		private void AcquireProjectMutex()
+		{
+			m_projectMutex = new Mutex(false, ProjectMutexName);
+			try
+			{
+				m_projectMutex.WaitOne();
+			}
+			catch (AbandonedMutexException) { }
+		}
+
+		private void ReleaseProjectMutex()
+		{
+			if (m_projectMutex == null)
+				return;
+
+			try
+			{
+				m_projectMutex.ReleaseMutex();
+			}
+			catch (ApplicationException) { }
+			finally
+			{
+				m_projectMutex.Dispose();
+				m_projectMutex = null;
+			}
+		}
+
+		private void DisposeCache()
+		{
+			if (Cache == null)
+				return;
+
+			Cache.Dispose();
+			Cache = null;
+		}
+
+		private void TryDisposeCacheAfterSetupFailure()
+		{
+			if (Cache == null)
+				return;
+
+			try
+			{
+				DisposeCache();
+			}
+			catch (Exception e)
 			{
-				Cache.Dispose();
 				Cache = null;
+				TestContext.Error.WriteLine(
+					"Could not dispose test cache after setup failure for '{0}': {1}",
+					m_dbName,
+					e.Message
+				);
 			}
-			var dbPath = DbFilename(m_dbName);
-			if (File.Exists(dbPath))
+		}
+
+		private void TryDeleteProjectDirectoryAfterSetupFailure()
+		{
+			try
 			{
-				try { File.Delete(dbPath); } catch { }
+				DeleteProjectDirectory(m_projectDirectory);
 			}
+			catch (Exception e)
+			{
+				TestContext.Error.WriteLine(
+					"Could not clean up test project directory '{0}' after setup failure: {1}",
+					m_projectDirectory,
+					e.Message
+				);
+			}
+		}
+
+		private static void RunSetupFailureCleanup(
+			Action disposeCache,
+			Action deleteProjectDirectory,
+			Action releaseProjectMutex
+		)
+		{
+			Exception firstException = null;
+
+			try
+			{
+				disposeCache();
+			}
+			catch (Exception e)
+			{
+				firstException = e;
+			}
+
+			try
+			{
+				deleteProjectDirectory();
+			}
+			catch (Exception e)
+			{
+				if (firstException == null)
+					firstException = e;
+			}
+
+			try
+			{
+				releaseProjectMutex();
+			}
+			catch (Exception e)
+			{
+				if (firstException == null)
+					firstException = e;
+			}
+
+			if (firstException != null)
+				throw firstException;
+		}
+
+		private static string GetProjectDirectory(string createdPath)
+		{
+			if (string.IsNullOrEmpty(createdPath))
+			{
+				throw new InvalidOperationException(
+					"CreateNewLangProj did not return a project path."
+				);
+			}
+
+			var fullPath = NormalizePath(createdPath);
+			if (Directory.Exists(fullPath))
+			{
+				EnsureSafeProjectDirectory(fullPath);
+				return fullPath;
+			}
+
+			if (!File.Exists(fullPath))
+			{
+				throw new FileNotFoundException(
+					"CreateNewLangProj returned a path that does not exist.",
+					fullPath
+				);
+			}
+
+			var projectDirectory = Path.GetDirectoryName(fullPath);
+			EnsureSafeProjectDirectory(projectDirectory);
+			return projectDirectory;
+		}
+
+		private static void WriteTestProjectSentinel(string projectDirectory)
+		{
+			EnsureSafeProjectDirectory(projectDirectory);
+			File.WriteAllText(
+				GetSentinelFilePath(projectDirectory),
+				"Created by FieldWorks RootSiteTests. This directory is safe for tests to delete."
+			);
+		}
+
+		private static void DeleteProjectDirectory(string projectDirectory)
+		{
+			if (string.IsNullOrEmpty(projectDirectory) || !Directory.Exists(projectDirectory))
+				return;
+
+			var safeProjectDirectory = NormalizePath(projectDirectory);
+			EnsureSafeProjectDirectory(safeProjectDirectory);
+
+			if (!File.Exists(GetSentinelFilePath(safeProjectDirectory)))
+			{
+				throw new InvalidOperationException(
+					string.Format(
+						"Refusing to delete '{0}' because the test sentinel file '{1}' is missing.",
+						safeProjectDirectory,
+						TestProjectSentinelFileName
+					)
+				);
+			}
+
+			if (!RobustIO.DeleteDirectoryAndContents(safeProjectDirectory))
+			{
+				TestContext.Error.WriteLine(
+					"Could not delete test project directory '{0}' via RobustIO.DeleteDirectoryAndContents.",
+					safeProjectDirectory
+				);
+				throw new IOException(
+					string.Format(
+						"Could not delete test project directory '{0}'.",
+						safeProjectDirectory
+					)
+				);
+			}
+		}
+
+		private static void EnsureSafeProjectDirectory(string projectDirectory)
+		{
+			if (string.IsNullOrEmpty(projectDirectory))
+				throw new InvalidOperationException("The test project directory path is empty.");
+
+			var safeProjectDirectory = NormalizePath(projectDirectory);
+			var expectedProjectDirectory = NormalizePath(
+				Path.Combine(FwDirectoryFinder.ProjectsDirectory, ReusableProjectName)
+			);
+
+			if (
+				!string.Equals(
+					safeProjectDirectory,
+					expectedProjectDirectory,
+					StringComparison.OrdinalIgnoreCase
+				)
+			)
+			{
+				throw new InvalidOperationException(
+					string.Format(
+						"Refusing to use test project directory '{0}'; expected '{1}'.",
+						safeProjectDirectory,
+						expectedProjectDirectory
+					)
+				);
+			}
+		}
+
+		private static string GetSentinelFilePath(string projectDirectory)
+		{
+			return Path.Combine(projectDirectory, TestProjectSentinelFileName);
 		}
 
-		protected string DbFilename(string name)
+		private static string NormalizePath(string path)
 		{
-			return Path.Combine(Path.GetTempPath(), name + ".fwdata");
+			return Path.GetFullPath(path)
+				.TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
 		}
 	}
 }
diff --git a/Src/Common/RootSite/RootSiteTests/RealDataTestsBaseCleanupTests.cs b/Src/Common/RootSite/RootSiteTests/RealDataTestsBaseCleanupTests.cs
new file mode 100644
index 0000000000..be97bca107
--- /dev/null
+++ b/Src/Common/RootSite/RootSiteTests/RealDataTestsBaseCleanupTests.cs
@@ -0,0 +1,64 @@
+using System;
+using System.Reflection;
+using NUnit.Framework;
+
+namespace SIL.FieldWorks.Common.RootSites.RootSiteTests
+{
+	[TestFixture]
+	public class RealDataTestsBaseCleanupTests
+	{
+		[Test]
+		public void RunSetupFailureCleanup_ReleasesMutexEvenWhenDisposeFails()
+		{
+			var deleteCalled = false;
+			var releaseCalled = false;
+			var method = GetRunSetupFailureCleanupMethod();
+
+			var exception = Assert.Catch<InvalidOperationException>(
+				() => InvokeRunSetupFailureCleanup(
+					method,
+					() => { throw new InvalidOperationException("dispose failed"); },
+					() => deleteCalled = true,
+					() => releaseCalled = true
+				)
+			);
+
+			Assert.That(exception.Message, Is.EqualTo("dispose failed"));
+			Assert.That(deleteCalled, Is.True, "delete cleanup should still run");
+			Assert.That(releaseCalled, Is.True, "mutex release should be guaranteed");
+		}
+
+		private static MethodInfo GetRunSetupFailureCleanupMethod()
+		{
+			var method = typeof(RealDataTestsBase).GetMethod(
+				"RunSetupFailureCleanup",
+				BindingFlags.Static | BindingFlags.NonPublic
+			);
+
+			Assert.That(
+				method,
+				Is.Not.Null,
+				"Expected RealDataTestsBase to expose a setup-failure cleanup helper."
+			);
+
+			return method;
+		}
+
+		private static void InvokeRunSetupFailureCleanup(
+			MethodInfo method,
+			Action disposeCache,
+			Action deleteProjectDirectory,
+			Action releaseProjectMutex
+		)
+		{
+			try
+			{
+				method.Invoke(null, new object[] { disposeCache, deleteProjectDirectory, releaseProjectMutex });
+			}
+			catch (TargetInvocationException e) when (e.InnerException != null)
+			{
+				throw e.InnerException;
+			}
+		}
+	}
+}
\ No newline at end of file