simplify and rewrite case-insensitive file path feature

13 files changed, 158 insertions, 182 deletions

diff --git a/docs/release-notes.md b/docs/release-notes.md
index e558a1bb..d9761a6d 100644
--- a/docs/release-notes.md
+++ b/docs/release-notes.md
@@ -2,6 +2,8 @@
 
 # Release notes
 ## Upcoming release
+* For players:
+  * Improved performance of case-insensitive file paths.
 * For mod authors:
   * Dynamic content packs created via `helper.ContentPacks.CreateTemporary` or `CreateFake` are now listed in the log file.
   * Fixed assets loaded through a fake content pack not working correctly since 3.14.0.
diff --git a/src/SMAPI.Tests/Core/ModResolverTests.cs b/src/SMAPI.Tests/Core/ModResolverTests.cs
index 3dfc9461..70c782ab 100644
--- a/src/SMAPI.Tests/Core/ModResolverTests.cs
+++ b/src/SMAPI.Tests/Core/ModResolverTests.cs
@@ -133,7 +133,7 @@ namespace SMAPI.Tests.Core
         [Test(Description = "Assert that validation doesn't fail if there are no mods installed.")]
         public void ValidateManifests_NoMods_DoesNothing()
         {
-            new ModResolver().ValidateManifests(Array.Empty<ModMetadata>(), apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFilePathLookup: _ => MinimalPathLookup.Instance, validateFilesExist: false);
+            new ModResolver().ValidateManifests(Array.Empty<ModMetadata>(), apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFileLookup: this.GetFileLookup, validateFilesExist: false);
         }
 
         [Test(Description = "Assert that validation skips manifests that have already failed without calling any other properties.")]
@@ -144,7 +144,7 @@ namespace SMAPI.Tests.Core
             mock.Setup(p => p.Status).Returns(ModMetadataStatus.Failed);
 
             // act
-            new ModResolver().ValidateManifests(new[] { mock.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFilePathLookup: _ => MinimalPathLookup.Instance, validateFilesExist: false);
+            new ModResolver().ValidateManifests(new[] { mock.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFileLookup: this.GetFileLookup, validateFilesExist: false);
 
             // assert
             mock.VerifyGet(p => p.Status, Times.Once, "The validation did not check the manifest status.");
@@ -161,7 +161,7 @@ namespace SMAPI.Tests.Core
             });
 
             // act
-            new ModResolver().ValidateManifests(new[] { mock.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFilePathLookup: _ => MinimalPathLookup.Instance, validateFilesExist: false);
+            new ModResolver().ValidateManifests(new[] { mock.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFileLookup: this.GetFileLookup, validateFilesExist: false);
 
             // assert
             mock.Verify(p => p.SetStatus(ModMetadataStatus.Failed, It.IsAny<ModFailReason>(), It.IsAny<string>(), It.IsAny<string>()), Times.Once, "The validation did not fail the metadata.");
@@ -175,7 +175,7 @@ namespace SMAPI.Tests.Core
             mock.Setup(p => p.Manifest).Returns(this.GetManifest(minimumApiVersion: "1.1"));
 
             // act
-            new ModResolver().ValidateManifests(new[] { mock.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFilePathLookup: _ => MinimalPathLookup.Instance, validateFilesExist: false);
+            new ModResolver().ValidateManifests(new[] { mock.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFileLookup: this.GetFileLookup, validateFilesExist: false);
 
             // assert
             mock.Verify(p => p.SetStatus(ModMetadataStatus.Failed, It.IsAny<ModFailReason>(), It.IsAny<string>(), It.IsAny<string>()), Times.Once, "The validation did not fail the metadata.");
@@ -190,7 +190,7 @@ namespace SMAPI.Tests.Core
             Directory.CreateDirectory(directoryPath);
 
             // act
-            new ModResolver().ValidateManifests(new[] { mock.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFilePathLookup: _ => MinimalPathLookup.Instance);
+            new ModResolver().ValidateManifests(new[] { mock.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFileLookup: this.GetFileLookup);
 
             // assert
             mock.Verify(p => p.SetStatus(ModMetadataStatus.Failed, It.IsAny<ModFailReason>(), It.IsAny<string>(), It.IsAny<string>()), Times.Once, "The validation did not fail the metadata.");
@@ -207,7 +207,7 @@ namespace SMAPI.Tests.Core
             Mock<IModMetadata> modB = this.GetMetadata(this.GetManifest(id: "Mod A", name: "Mod B", version: "1.0"), allowStatusChange: true);
 
             // act
-            new ModResolver().ValidateManifests(new[] { modA.Object, modB.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFilePathLookup: _ => MinimalPathLookup.Instance, validateFilesExist: false);
+            new ModResolver().ValidateManifests(new[] { modA.Object, modB.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFileLookup: this.GetFileLookup, validateFilesExist: false);
 
             // assert
             modA.Verify(p => p.SetStatus(ModMetadataStatus.Failed, ModFailReason.Duplicate, It.IsAny<string>(), It.IsAny<string>()), Times.AtLeastOnce, "The validation did not fail the first mod with a unique ID.");
@@ -233,7 +233,7 @@ namespace SMAPI.Tests.Core
             mock.Setup(p => p.DirectoryPath).Returns(modFolder);
 
             // act
-            new ModResolver().ValidateManifests(new[] { mock.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFilePathLookup: _ => MinimalPathLookup.Instance);
+            new ModResolver().ValidateManifests(new[] { mock.Object }, apiVersion: new SemanticVersion("1.0"), getUpdateUrl: _ => null, getFileLookup: this.GetFileLookup);
 
             // assert
             // if Moq doesn't throw a method-not-setup exception, the validation didn't override the status.
@@ -483,6 +483,13 @@ namespace SMAPI.Tests.Core
             return Path.Combine(Path.GetTempPath(), "smapi-unit-tests", Guid.NewGuid().ToString("N"));
         }
 
+        /// <summary>Get a file lookup for a given directory.</summary>
+        /// <param name="rootDirectory">The full path to the directory.</param>
+        private IFileLookup GetFileLookup(string rootDirectory)
+        {
+            return MinimalFileLookup.GetCachedFor(rootDirectory);
+        }
+
         /// <summary>Get a randomized basic manifest.</summary>
         /// <param name="id">The <see cref="IManifest.UniqueID"/> value, or <c>null</c> for a generated value.</param>
         /// <param name="name">The <see cref="IManifest.Name"/> value, or <c>null</c> for a generated value.</param>
diff --git a/src/SMAPI.Toolkit/Framework/ModScanning/ModScanner.cs b/src/SMAPI.Toolkit/Framework/ModScanning/ModScanner.cs
index aa4c3338..a85ef109 100644
--- a/src/SMAPI.Toolkit/Framework/ModScanning/ModScanner.cs
+++ b/src/SMAPI.Toolkit/Framework/ModScanning/ModScanner.cs
@@ -114,10 +114,11 @@ namespace StardewModdingAPI.Toolkit.Framework.ModScanning
         /// <summary>Extract information from a mod folder.</summary>
         /// <param name="root">The root folder containing mods.</param>
         /// <param name="searchFolder">The folder to search for a mod.</param>
-        public ModFolder ReadFolder(DirectoryInfo root, DirectoryInfo searchFolder)
+        /// <param name="useCaseInsensitiveFilePaths">Whether to match file paths case-insensitively, even on Linux.</param>
+        public ModFolder ReadFolder(DirectoryInfo root, DirectoryInfo searchFolder, bool useCaseInsensitiveFilePaths)
         {
             // find manifest.json
-            FileInfo? manifestFile = this.FindManifest(searchFolder);
+            FileInfo? manifestFile = this.FindManifest(searchFolder, useCaseInsensitiveFilePaths);
 
             // set appropriate invalid-mod error
             if (manifestFile == null)
@@ -225,7 +226,7 @@ namespace StardewModdingAPI.Toolkit.Framework.ModScanning
 
             // treat as mod folder
             else
-                yield return this.ReadFolder(root, folder);
+                yield return this.ReadFolder(root, folder, useCaseInsensitiveFilePaths);
         }
 
         /// <summary>Consolidate adjacent folders into one mod folder, if possible.</summary>
@@ -250,7 +251,8 @@ namespace StardewModdingAPI.Toolkit.Framework.ModScanning
 
         /// <summary>Find the manifest for a mod folder.</summary>
         /// <param name="folder">The folder to search.</param>
-        private FileInfo? FindManifest(DirectoryInfo folder)
+        /// <param name="useCaseInsensitiveFilePaths">Whether to match file paths case-insensitively, even on Linux.</param>
+        private FileInfo? FindManifest(DirectoryInfo folder, bool useCaseInsensitiveFilePaths)
         {
             // check for conventional manifest in current folder
             const string defaultName = "manifest.json";
@@ -259,14 +261,14 @@ namespace StardewModdingAPI.Toolkit.Framework.ModScanning
                 return file;
 
             // check for manifest with incorrect capitalization
+            if (useCaseInsensitiveFilePaths)
             {
-                CaseInsensitivePathLookup pathLookup = new(folder.FullName, SearchOption.TopDirectoryOnly); // don't use GetCachedFor, since we only need it temporarily
-                string realName = pathLookup.GetFilePath(defaultName);
-                if (realName != defaultName)
-                    file = new(Path.Combine(folder.FullName, realName));
+                CaseInsensitiveFileLookup fileLookup = new(folder.FullName, SearchOption.TopDirectoryOnly); // don't use GetCachedFor, since we only need it temporarily
+                file = fileLookup.GetFile(defaultName);
+                return file.Exists
+                    ? file
+                    : null;
             }
-            if (file.Exists)
-                return file;
 
             // not found
             return null;
diff --git a/src/SMAPI.Toolkit/Utilities/PathLookups/CaseInsensitivePathLookup.cs b/src/SMAPI.Toolkit/Utilities/PathLookups/CaseInsensitivePathLookup.cs
index 9cc00737..496d54c3 100644
--- a/src/SMAPI.Toolkit/Utilities/PathLookups/CaseInsensitivePathLookup.cs
+++ b/src/SMAPI.Toolkit/Utilities/PathLookups/CaseInsensitivePathLookup.cs
@@ -4,8 +4,8 @@ using System.IO;
 
 namespace StardewModdingAPI.Toolkit.Utilities.PathLookups
 {
-    /// <summary>An API for case-insensitive relative path lookups within a root directory.</summary>
-    internal class CaseInsensitivePathLookup : IFilePathLookup
+    /// <summary>An API for case-insensitive file lookups within a root directory.</summary>
+    internal class CaseInsensitiveFileLookup : IFileLookup
     {
         /*********
         ** Fields
@@ -16,8 +16,8 @@ namespace StardewModdingAPI.Toolkit.Utilities.PathLookups
         /// <summary>A case-insensitive lookup of file paths within the <see cref="RootPath"/>. Each path is listed in both file path and asset name format, so it's usable in both contexts without needing to re-parse paths.</summary>
         private readonly Lazy<Dictionary<string, string>> RelativePathCache;
 
-        /// <summary>The case-insensitive path caches by root path.</summary>
-        private static readonly Dictionary<string, CaseInsensitivePathLookup> CachedRoots = new(StringComparer.OrdinalIgnoreCase);
+        /// <summary>The case-insensitive file lookups by root path.</summary>
+        private static readonly Dictionary<string, CaseInsensitiveFileLookup> CachedRoots = new(StringComparer.OrdinalIgnoreCase);
 
 
         /*********
@@ -26,22 +26,28 @@ namespace StardewModdingAPI.Toolkit.Utilities.PathLookups
         /// <summary>Construct an instance.</summary>
         /// <param name="rootPath">The root directory path for relative paths.</param>
         /// <param name="searchOption">Which directories to scan from the root.</param>
-        public CaseInsensitivePathLookup(string rootPath, SearchOption searchOption = SearchOption.AllDirectories)
+        public CaseInsensitiveFileLookup(string rootPath, SearchOption searchOption = SearchOption.AllDirectories)
         {
-            this.RootPath = rootPath;
+            this.RootPath = PathUtilities.NormalizePath(rootPath);
             this.RelativePathCache = new(() => this.GetRelativePathCache(searchOption));
         }
 
         /// <inheritdoc />
-        public string GetFilePath(string relativePath)
+        public FileInfo GetFile(string relativePath)
         {
-            return this.GetImpl(PathUtilities.NormalizePath(relativePath));
-        }
+            // invalid path
+            if (string.IsNullOrWhiteSpace(relativePath))
+                throw new InvalidOperationException("Can't get a file from an empty relative path.");
 
-        /// <inheritdoc />
-        public string GetAssetName(string relativePath)
-        {
-            return this.GetImpl(PathUtilities.NormalizeAssetName(relativePath));
+            // already cached
+            if (this.RelativePathCache.Value.TryGetValue(relativePath, out string? resolved))
+                return new(Path.Combine(this.RootPath, resolved));
+
+            // keep capitalization as-is
+            FileInfo file = new(Path.Combine(this.RootPath, relativePath));
+            if (file.Exists)
+                this.RelativePathCache.Value[relativePath] = relativePath;
+            return file;
         }
 
         /// <inheritdoc />
@@ -61,17 +67,17 @@ namespace StardewModdingAPI.Toolkit.Utilities.PathLookups
                 throw new InvalidOperationException($"Can't add relative path '{relativePath}' to the case-insensitive cache for '{this.RootPath}' because that file doesn't exist.");
 
             // cache path
-            this.CacheRawPath(this.RelativePathCache.Value, relativePath);
+            this.RelativePathCache.Value[relativePath] = relativePath;
         }
 
         /// <summary>Get a cached dictionary of relative paths within a root path, for case-insensitive file lookups.</summary>
         /// <param name="rootPath">The root path to scan.</param>
-        public static CaseInsensitivePathLookup GetCachedFor(string rootPath)
+        public static CaseInsensitiveFileLookup GetCachedFor(string rootPath)
         {
             rootPath = PathUtilities.NormalizePath(rootPath);
 
-            if (!CaseInsensitivePathLookup.CachedRoots.TryGetValue(rootPath, out CaseInsensitivePathLookup? cache))
-                CaseInsensitivePathLookup.CachedRoots[rootPath] = cache = new CaseInsensitivePathLookup(rootPath);
+            if (!CaseInsensitiveFileLookup.CachedRoots.TryGetValue(rootPath, out CaseInsensitiveFileLookup? cache))
+                CaseInsensitiveFileLookup.CachedRoots[rootPath] = cache = new CaseInsensitiveFileLookup(rootPath);
 
             return cache;
         }
@@ -80,29 +86,6 @@ namespace StardewModdingAPI.Toolkit.Utilities.PathLookups
         /*********
         ** Private methods
         *********/
-        /// <summary>Get the exact capitalization for a given relative path.</summary>
-        /// <param name="relativePath">The relative path. This must already be normalized into asset name or file path format (i.e. using <see cref="PathUtilities.NormalizeAssetName"/> or <see cref="PathUtilities.NormalizePath"/> respectively).</param>
-        /// <remarks>Returns the resolved path in the same format if found, else returns the path as-is.</remarks>
-        private string GetImpl(string relativePath)
-        {
-            // invalid path
-            if (string.IsNullOrWhiteSpace(relativePath))
-                return relativePath;
-
-            // already cached
-            if (this.RelativePathCache.Value.TryGetValue(relativePath, out string? resolved))
-                return resolved;
-
-            // keep capitalization as-is
-            if (File.Exists(Path.Combine(this.RootPath, relativePath)))
-            {
-                // file exists but isn't cached for some reason
-                // cache it now so any later references to it are case-insensitive
-                this.CacheRawPath(this.RelativePathCache.Value, relativePath);
-            }
-            return relativePath;
-        }
-
         /// <summary>Get a case-insensitive lookup of file paths (see <see cref="RelativePathCache"/>).</summary>
         /// <param name="searchOption">Which directories to scan from the root.</param>
         private Dictionary<string, string> GetRelativePathCache(SearchOption searchOption)
@@ -112,23 +95,10 @@ namespace StardewModdingAPI.Toolkit.Utilities.PathLookups
             foreach (string path in Directory.EnumerateFiles(this.RootPath, "*", searchOption))
             {
                 string relativePath = path.Substring(this.RootPath.Length + 1);
-
-                this.CacheRawPath(cache, relativePath);
+                cache[relativePath] = relativePath;
             }
 
             return cache;
         }
-
-        /// <summary>Add a raw relative path to the cache.</summary>
-        /// <param name="cache">The cache to update.</param>
-        /// <param name="relativePath">The relative path to cache, with its exact filesystem capitalization.</param>
-        private void CacheRawPath(IDictionary<string, string> cache, string relativePath)
-        {
-            string filePath = PathUtilities.NormalizePath(relativePath);
-            string assetName = PathUtilities.NormalizeAssetName(relativePath);
-
-            cache[filePath] = filePath;
-            cache[assetName] = assetName;
-        }
     }
 }
diff --git a/src/SMAPI.Toolkit/Utilities/PathLookups/IFilePathLookup.cs b/src/SMAPI.Toolkit/Utilities/PathLookups/IFilePathLookup.cs
index 678e1383..d43b5141 100644
--- a/src/SMAPI.Toolkit/Utilities/PathLookups/IFilePathLookup.cs
+++ b/src/SMAPI.Toolkit/Utilities/PathLookups/IFilePathLookup.cs
@@ -1,20 +1,16 @@
+using System.IO;
+
 namespace StardewModdingAPI.Toolkit.Utilities.PathLookups
 {
-    /// <summary>An API for relative path lookups within a root directory.</summary>
-    internal interface IFilePathLookup
+    /// <summary>An API for file lookups within a root directory.</summary>
+    internal interface IFileLookup
     {
-        /// <summary>Get the actual path for a given relative file path.</summary>
-        /// <param name="relativePath">The relative path.</param>
-        /// <remarks>Returns the resolved path in file path format, else the normalized <paramref name="relativePath"/>.</remarks>
-        string GetFilePath(string relativePath);
-
-        /// <summary>Get the actual path for a given asset name.</summary>
+        /// <summary>Get the file for a given relative file path, if it exists.</summary>
         /// <param name="relativePath">The relative path.</param>
-        /// <remarks>Returns the resolved path in asset name format, else the normalized <paramref name="relativePath"/>.</remarks>
-        string GetAssetName(string relativePath);
+        FileInfo GetFile(string relativePath);
 
         /// <summary>Add a relative path that was just created by a SMAPI API.</summary>
-        /// <param name="relativePath">The relative path. This must already be normalized in asset name or file path format.</param>
+        /// <param name="relativePath">The relative path.</param>
         void Add(string relativePath);
     }
 }
diff --git a/src/SMAPI.Toolkit/Utilities/PathLookups/MinimalPathLookup.cs b/src/SMAPI.Toolkit/Utilities/PathLookups/MinimalPathLookup.cs
index 2cf14704..414b569b 100644
--- a/src/SMAPI.Toolkit/Utilities/PathLookups/MinimalPathLookup.cs
+++ b/src/SMAPI.Toolkit/Utilities/PathLookups/MinimalPathLookup.cs
@@ -1,31 +1,52 @@
+using System.Collections.Generic;
+using System.IO;
+
 namespace StardewModdingAPI.Toolkit.Utilities.PathLookups
 {
-    /// <summary>An API for relative path lookups within a root directory with minimal preprocessing.</summary>
-    internal class MinimalPathLookup : IFilePathLookup
+    /// <summary>An API for file lookups within a root directory with minimal preprocessing.</summary>
+    internal class MinimalFileLookup : IFileLookup
     {
         /*********
         ** Accessors
         *********/
-        /// <summary>A singleton instance for reuse.</summary>
-        public static readonly MinimalPathLookup Instance = new();
+        /// <summary>The file lookups by root path.</summary>
+        private static readonly Dictionary<string, MinimalFileLookup> CachedRoots = new();
+
+        /// <summary>The root directory path for relative paths.</summary>
+        private readonly string RootPath;
 
 
         /*********
         ** Public methods
         *********/
-        /// <inheritdoc />
-        public string GetFilePath(string relativePath)
+        /// <summary>Construct an instance.</summary>
+        /// <param name="rootPath">The root directory path for relative paths.</param>
+        public MinimalFileLookup(string rootPath)
         {
-            return PathUtilities.NormalizePath(relativePath);
+            this.RootPath = rootPath;
         }
 
         /// <inheritdoc />
-        public string GetAssetName(string relativePath)
+        public FileInfo GetFile(string relativePath)
         {
-            return PathUtilities.NormalizeAssetName(relativePath);
+            return new(
+                Path.Combine(this.RootPath, PathUtilities.NormalizePath(relativePath))
+            );
         }
 
         /// <inheritdoc />
         public void Add(string relativePath) { }
+
+        /// <summary>Get a cached dictionary of relative paths within a root path, for case-insensitive file lookups.</summary>
+        /// <param name="rootPath">The root path to scan.</param>
+        public static MinimalFileLookup GetCachedFor(string rootPath)
+        {
+            rootPath = PathUtilities.NormalizePath(rootPath);
+
+            if (!MinimalFileLookup.CachedRoots.TryGetValue(rootPath, out MinimalFileLookup? lookup))
+                MinimalFileLookup.CachedRoots[rootPath] = lookup = new MinimalFileLookup(rootPath);
+
+            return lookup;
+        }
     }
 }
diff --git a/src/SMAPI/Framework/ContentCoordinator.cs b/src/SMAPI/Framework/ContentCoordinator.cs
index 4f52d57e..02b753ba 100644
--- a/src/SMAPI/Framework/ContentCoordinator.cs
+++ b/src/SMAPI/Framework/ContentCoordinator.cs
@@ -32,8 +32,8 @@ namespace StardewModdingAPI.Framework
         /// <summary>An asset key prefix for assets from SMAPI mod folders.</summary>
         private readonly string ManagedPrefix = "SMAPI";
 
-        /// <summary>Get a file path lookup for the given directory.</summary>
-        private readonly Func<string, IFilePathLookup> GetFilePathLookup;
+        /// <summary>Get a file lookup for the given directory.</summary>
+        private readonly Func<string, IFileLookup> GetFileLookup;
 
         /// <summary>Encapsulates monitoring and logging.</summary>
         private readonly IMonitor Monitor;
@@ -123,12 +123,12 @@ namespace StardewModdingAPI.Framework
         /// <param name="jsonHelper">Encapsulates SMAPI's JSON file parsing.</param>
         /// <param name="onLoadingFirstAsset">A callback to invoke the first time *any* game content manager loads an asset.</param>
         /// <param name="onAssetLoaded">A callback to invoke when an asset is fully loaded.</param>
-        /// <param name="getFilePathLookup">Get a file path lookup for the given directory.</param>
+        /// <param name="getFileLookup">Get a file lookup for the given directory.</param>
         /// <param name="onAssetsInvalidated">A callback to invoke when any asset names have been invalidated from the cache.</param>
         /// <param name="requestAssetOperations">Get the load/edit operations to apply to an asset by querying registered <see cref="IContentEvents.AssetRequested"/> event handlers.</param>
-        public ContentCoordinator(IServiceProvider serviceProvider, string rootDirectory, CultureInfo currentCulture, IMonitor monitor, Reflector reflection, JsonHelper jsonHelper, Action onLoadingFirstAsset, Action<BaseContentManager, IAssetName> onAssetLoaded, Func<string, IFilePathLookup> getFilePathLookup, Action<IList<IAssetName>> onAssetsInvalidated, Func<IAssetInfo, IList<AssetOperationGroup>> requestAssetOperations)
+        public ContentCoordinator(IServiceProvider serviceProvider, string rootDirectory, CultureInfo currentCulture, IMonitor monitor, Reflector reflection, JsonHelper jsonHelper, Action onLoadingFirstAsset, Action<BaseContentManager, IAssetName> onAssetLoaded, Func<string, IFileLookup> getFileLookup, Action<IList<IAssetName>> onAssetsInvalidated, Func<IAssetInfo, IList<AssetOperationGroup>> requestAssetOperations)
         {
-            this.GetFilePathLookup = getFilePathLookup;
+            this.GetFileLookup = getFileLookup;
             this.Monitor = monitor ?? throw new ArgumentNullException(nameof(monitor));
             this.Reflection = reflection;
             this.JsonHelper = jsonHelper;
@@ -200,7 +200,7 @@ namespace StardewModdingAPI.Framework
                     reflection: this.Reflection,
                     jsonHelper: this.JsonHelper,
                     onDisposing: this.OnDisposing,
-                    relativePathLookup: this.GetFilePathLookup(rootDirectory)
+                    fileLookup: this.GetFileLookup(rootDirectory)
                 );
                 this.ContentManagers.Add(manager);
                 return manager;
diff --git a/src/SMAPI/Framework/ContentManagers/ModContentManager.cs b/src/SMAPI/Framework/ContentManagers/ModContentManager.cs
index 65dffd8b..7cac8f36 100644
--- a/src/SMAPI/Framework/ContentManagers/ModContentManager.cs
+++ b/src/SMAPI/Framework/ContentManagers/ModContentManager.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
 using System.Linq;
@@ -33,11 +34,11 @@ namespace StardewModdingAPI.Framework.ContentManagers
         /// <summary>The game content manager used for map tilesheets not provided by the mod.</summary>
         private readonly IContentManager GameContentManager;
 
-        /// <summary>A lookup for relative paths within the <see cref="ContentManager.RootDirectory"/>.</summary>
-        private readonly IFilePathLookup RelativePathLookup;
+        /// <summary>A lookup for files within the <see cref="ContentManager.RootDirectory"/>.</summary>
+        private readonly IFileLookup FileLookup;
 
         /// <summary>If a map tilesheet's image source has no file extensions, the file extensions to check for in the local mod folder.</summary>
-        private readonly string[] LocalTilesheetExtensions = { ".png", ".xnb" };
+        private static readonly HashSet<string> LocalTilesheetExtensions = new(StringComparer.OrdinalIgnoreCase) { ".png", ".xnb" };
 
 
         /*********
@@ -55,12 +56,12 @@ namespace StardewModdingAPI.Framework.ContentManagers
         /// <param name="reflection">Simplifies access to private code.</param>
         /// <param name="jsonHelper">Encapsulates SMAPI's JSON file parsing.</param>
         /// <param name="onDisposing">A callback to invoke when the content manager is being disposed.</param>
-        /// <param name="relativePathLookup">A lookup for relative paths within the <paramref name="rootDirectory"/>.</param>
-        public ModContentManager(string name, IContentManager gameContentManager, IServiceProvider serviceProvider, string modName, string rootDirectory, CultureInfo currentCulture, ContentCoordinator coordinator, IMonitor monitor, Reflector reflection, JsonHelper jsonHelper, Action<BaseContentManager> onDisposing, IFilePathLookup relativePathLookup)
+        /// <param name="fileLookup">A lookup for files within the <paramref name="rootDirectory"/>.</param>
+        public ModContentManager(string name, IContentManager gameContentManager, IServiceProvider serviceProvider, string modName, string rootDirectory, CultureInfo currentCulture, ContentCoordinator coordinator, IMonitor monitor, Reflector reflection, JsonHelper jsonHelper, Action<BaseContentManager> onDisposing, IFileLookup fileLookup)
             : base(name, serviceProvider, rootDirectory, currentCulture, coordinator, monitor, reflection, onDisposing, isNamespaced: true)
         {
             this.GameContentManager = gameContentManager;
-            this.RelativePathLookup = relativePathLookup;
+            this.FileLookup = fileLookup;
             this.JsonHelper = jsonHelper;
             this.ModName = modName;
 
@@ -73,7 +74,7 @@ namespace StardewModdingAPI.Framework.ContentManagers
             if (base.DoesAssetExist<T>(assetName))
                 return true;
 
-            FileInfo file = this.GetModFile(assetName.Name);
+            FileInfo file = this.GetModFile<T>(assetName.Name);
             return file.Exists;
         }
 
@@ -103,7 +104,7 @@ namespace StardewModdingAPI.Framework.ContentManagers
             try
             {
                 // get file
-                FileInfo file = this.GetModFile(assetName.Name);
+                FileInfo file = this.GetModFile<T>(assetName.Name);
                 if (!file.Exists)
                     throw this.GetLoadError(assetName, "the specified path doesn't exist.");
 
@@ -139,9 +140,7 @@ namespace StardewModdingAPI.Framework.ContentManagers
         /// <exception cref="ArgumentException">The <paramref name="key"/> is empty or contains invalid characters.</exception>
         public IAssetName GetInternalAssetKey(string key)
         {
-            FileInfo file = this.GetModFile(key);
-            string relativePath = Path.GetRelativePath(this.RootDirectory, file.FullName);
-            string internalKey = Path.Combine(this.Name, relativePath);
+            string internalKey = Path.Combine(this.Name, PathUtilities.NormalizeAssetName(key));
 
             return this.Coordinator.ParseAssetName(internalKey, allowLocales: false);
         }
@@ -253,19 +252,17 @@ namespace StardewModdingAPI.Framework.ContentManagers
         }
 
         /// <summary>Get a file from the mod folder.</summary>
+        /// <typeparam name="T">The expected asset type.</typeparam>
         /// <param name="path">The asset path relative to the content folder.</param>
-        private FileInfo GetModFile(string path)
+        private FileInfo GetModFile<T>(string path)
         {
-            // map to case-insensitive path if needed
-            path = this.RelativePathLookup.GetFilePath(path);
+            // get exact file
+            FileInfo file = this.FileLookup.GetFile(path);
 
-            // try exact match
-            FileInfo file = new(Path.Combine(this.FullRootDirectory, path));
-
-            // try with default extension
-            if (!file.Exists)
+            // try with default image extensions
+            if (!file.Exists && typeof(Texture2D).IsAssignableFrom(typeof(T)) && !ModContentManager.LocalTilesheetExtensions.Contains(file.Extension))
             {
-                foreach (string extension in this.LocalTilesheetExtensions)
+                foreach (string extension in ModContentManager.LocalTilesheetExtensions)
                 {
                     FileInfo result = new(file.FullName + extension);
                     if (result.Exists)
@@ -385,7 +382,7 @@ namespace StardewModdingAPI.Framework.ContentManagers
             // get relative to map file
             {
                 string localKey = Path.Combine(modRelativeMapFolder, relativePath);
-                if (this.GetModFile(localKey).Exists)
+                if (this.GetModFile<Texture2D>(localKey).Exists)
                 {
                     assetName = this.GetInternalAssetKey(localKey);
                     return true;
diff --git a/src/SMAPI/Framework/ContentPack.cs b/src/SMAPI/Framework/ContentPack.cs
index 9503a0e6..5975fff6 100644
--- a/src/SMAPI/Framework/ContentPack.cs
+++ b/src/SMAPI/Framework/ContentPack.cs
@@ -16,8 +16,8 @@ namespace StardewModdingAPI.Framework
         /// <summary>Encapsulates SMAPI's JSON file parsing.</summary>
         private readonly JsonHelper JsonHelper;
 
-        /// <summary>A lookup for relative paths within the <see cref="DirectoryPath"/>.</summary>
-        private readonly IFilePathLookup RelativePathCache;
+        /// <summary>A lookup for files within the <see cref="DirectoryPath"/>.</summary>
+        private readonly IFileLookup FileLookup;
 
 
         /*********
@@ -48,15 +48,15 @@ namespace StardewModdingAPI.Framework
         /// <param name="content">Provides an API for loading content assets from the content pack's folder.</param>
         /// <param name="translation">Provides translations stored in the content pack's <c>i18n</c> folder.</param>
         /// <param name="jsonHelper">Encapsulates SMAPI's JSON file parsing.</param>
-        /// <param name="relativePathCache">A lookup for relative paths within the <paramref name="directoryPath"/>.</param>
-        public ContentPack(string directoryPath, IManifest manifest, IModContentHelper content, TranslationHelper translation, JsonHelper jsonHelper, IFilePathLookup relativePathCache)
+        /// <param name="fileLookup">A lookup for files within the <paramref name="directoryPath"/>.</param>
+        public ContentPack(string directoryPath, IManifest manifest, IModContentHelper content, TranslationHelper translation, JsonHelper jsonHelper, IFileLookup fileLookup)
         {
             this.DirectoryPath = directoryPath;
             this.Manifest = manifest;
             this.ModContent = content;
             this.TranslationImpl = translation;
             this.JsonHelper = jsonHelper;
-            this.RelativePathCache = relativePathCache;
+            this.FileLookup = fileLookup;
         }
 
         /// <inheritdoc />
@@ -83,10 +83,17 @@ namespace StardewModdingAPI.Framework
         {
             path = PathUtilities.NormalizePath(path);
 
-            FileInfo file = this.GetFile(path, out path);
+            FileInfo file = this.GetFile(path);
+            bool didExist = file.Exists;
+
             this.JsonHelper.WriteJsonFile(file.FullName, data);
 
-            this.RelativePathCache.Add(path);
+            if (!didExist)
+            {
+                this.FileLookup.Add(
+                    Path.GetRelativePath(this.DirectoryPath, file.FullName)
+                );
+            }
         }
 
         /// <inheritdoc />
@@ -112,20 +119,10 @@ namespace StardewModdingAPI.Framework
         /// <param name="relativePath">The normalized file path relative to the content pack directory.</param>
         private FileInfo GetFile(string relativePath)
         {
-            return this.GetFile(relativePath, out _);
-        }
-
-        /// <summary>Get the underlying file info.</summary>
-        /// <param name="relativePath">The normalized file path relative to the content pack directory.</param>
-        /// <param name="actualRelativePath">The relative path after case-insensitive matching.</param>
-        private FileInfo GetFile(string relativePath, out string actualRelativePath)
-        {
             if (!PathUtilities.IsSafeRelativePath(relativePath))
                 throw new InvalidOperationException($"You must call {nameof(IContentPack)} methods with a relative path.");
 
-            actualRelativePath = this.RelativePathCache.GetFilePath(relativePath);
-
-            return new FileInfo(Path.Combine(this.DirectoryPath, actualRelativePath));
+            return this.FileLookup.GetFile(relativePath);
         }
     }
 }
diff --git a/src/SMAPI/Framework/ModHelpers/ModContentHelper.cs b/src/SMAPI/Framework/ModHelpers/ModContentHelper.cs
index 74ea73de..6429f9bf 100644
--- a/src/SMAPI/Framework/ModHelpers/ModContentHelper.cs
+++ b/src/SMAPI/Framework/ModHelpers/ModContentHelper.cs
@@ -1,10 +1,8 @@
 using System;
-using Microsoft.Xna.Framework.Content;
 using StardewModdingAPI.Framework.Content;
 using StardewModdingAPI.Framework.ContentManagers;
 using StardewModdingAPI.Framework.Exceptions;
 using StardewModdingAPI.Framework.Reflection;
-using StardewModdingAPI.Toolkit.Utilities.PathLookups;
 
 namespace StardewModdingAPI.Framework.ModHelpers
 {
@@ -23,9 +21,6 @@ namespace StardewModdingAPI.Framework.ModHelpers
         /// <summary>The friendly mod name for use in errors.</summary>
         private readonly string ModName;
 
-        /// <summary>A lookup for relative paths within the <see cref="ContentManager.RootDirectory"/>.</summary>
-        private readonly IFilePathLookup RelativePathLookup;
-
         /// <summary>Simplifies access to private code.</summary>
         private readonly Reflector Reflection;
 
@@ -39,9 +34,8 @@ namespace StardewModdingAPI.Framework.ModHelpers
         /// <param name="mod">The mod using this instance.</param>
         /// <param name="modName">The friendly mod name for use in errors.</param>
         /// <param name="gameContentManager">The game content manager used for map tilesheets not provided by the mod.</param>
-        /// <param name="relativePathLookup">A lookup for relative paths within the <paramref name="relativePathLookup"/>.</param>
         /// <param name="reflection">Simplifies access to private code.</param>
-        public ModContentHelper(ContentCoordinator contentCore, string modFolderPath, IModMetadata mod, string modName, IContentManager gameContentManager, IFilePathLookup relativePathLookup, Reflector reflection)
+        public ModContentHelper(ContentCoordinator contentCore, string modFolderPath, IModMetadata mod, string modName, IContentManager gameContentManager, Reflector reflection)
             : base(mod)
         {
             string managedAssetPrefix = contentCore.GetManagedAssetPrefix(mod.Manifest.UniqueID);
@@ -49,7 +43,6 @@ namespace StardewModdingAPI.Framework.ModHelpers
             this.ContentCore = contentCore;
             this.ModContentManager = contentCore.CreateModContentManager(managedAssetPrefix, modName, modFolderPath, gameContentManager);
             this.ModName = modName;
-            this.RelativePathLookup = relativePathLookup;
             this.Reflection = reflection;
         }
 
@@ -57,8 +50,6 @@ namespace StardewModdingAPI.Framework.ModHelpers
         public T Load<T>(string relativePath)
             where T : notnull
         {
-            relativePath = this.RelativePathLookup.GetAssetName(relativePath);
-
             IAssetName assetName = this.ContentCore.ParseAssetName(relativePath, allowLocales: false);
 
             try
@@ -74,7 +65,6 @@ namespace StardewModdingAPI.Framework.ModHelpers
         /// <inheritdoc />
         public IAssetName GetInternalAssetName(string relativePath)
         {
-            relativePath = this.RelativePathLookup.GetAssetName(relativePath);
             return this.ModContentManager.GetInternalAssetKey(relativePath);
         }
 
@@ -85,9 +75,7 @@ namespace StardewModdingAPI.Framework.ModHelpers
             if (data == null)
                 throw new ArgumentNullException(nameof(data), "Can't get a patch helper for a null value.");
 
-            relativePath = relativePath != null
-                ? this.RelativePathLookup.GetAssetName(relativePath)
-                : $"temp/{Guid.NewGuid():N}";
+            relativePath ??= $"temp/{Guid.NewGuid():N}";
 
             return new AssetDataForObject(
                 locale: this.ContentCore.GetLocale(),
diff --git a/src/SMAPI/Framework/ModLoading/AssemblyLoader.cs b/src/SMAPI/Framework/ModLoading/AssemblyLoader.cs
index 72b547b1..a6756e0e 100644
--- a/src/SMAPI/Framework/ModLoading/AssemblyLoader.cs
+++ b/src/SMAPI/Framework/ModLoading/AssemblyLoader.cs
@@ -85,11 +85,11 @@ namespace StardewModdingAPI.Framework.ModLoading
 
         /// <summary>Preprocess and load an assembly.</summary>
         /// <param name="mod">The mod for which the assembly is being loaded.</param>
-        /// <param name="assemblyPath">The assembly file path.</param>
+        /// <param name="assemblyFile">The assembly file.</param>
         /// <param name="assumeCompatible">Assume the mod is compatible, even if incompatible code is detected.</param>
         /// <returns>Returns the rewrite metadata for the preprocessed assembly.</returns>
         /// <exception cref="IncompatibleInstructionException">An incompatible CIL instruction was found while rewriting the assembly.</exception>
-        public Assembly Load(IModMetadata mod, string assemblyPath, bool assumeCompatible)
+        public Assembly Load(IModMetadata mod, FileInfo assemblyFile, bool assumeCompatible)
         {
             // get referenced local assemblies
             AssemblyParseResult[] assemblies;
@@ -100,19 +100,19 @@ namespace StardewModdingAPI.Framework.ModLoading
                     where name != null
                     select name
                 );
-                assemblies = this.GetReferencedLocalAssemblies(new FileInfo(assemblyPath), visitedAssemblyNames, this.AssemblyDefinitionResolver).ToArray();
+                assemblies = this.GetReferencedLocalAssemblies(assemblyFile, visitedAssemblyNames, this.AssemblyDefinitionResolver).ToArray();
             }
 
             // validate load
             if (!assemblies.Any() || assemblies[0].Status == AssemblyLoadStatus.Failed)
             {
-                throw new SAssemblyLoadFailedException(!File.Exists(assemblyPath)
-                    ? $"Could not load '{assemblyPath}' because it doesn't exist."
-                    : $"Could not load '{assemblyPath}'."
+                throw new SAssemblyLoadFailedException(!assemblyFile.Exists
+                    ? $"Could not load '{assemblyFile.FullName}' because it doesn't exist."
+                    : $"Could not load '{assemblyFile.FullName}'."
                 );
             }
             if (assemblies.Last().Status == AssemblyLoadStatus.AlreadyLoaded) // mod assembly is last in dependency order
-                throw new SAssemblyLoadFailedException($"Could not load '{assemblyPath}' because it was already loaded. Do you have two copies of this mod?");
+                throw new SAssemblyLoadFailedException($"Could not load '{assemblyFile.FullName}' because it was already loaded. Do you have two copies of this mod?");
 
             // rewrite & load assemblies in leaf-to-root order
             bool oneAssembly = assemblies.Length == 1;
diff --git a/src/SMAPI/Framework/ModLoading/ModResolver.cs b/src/SMAPI/Framework/ModLoading/ModResolver.cs
index 1b1fa04e..3e7144f9 100644
--- a/src/SMAPI/Framework/ModLoading/ModResolver.cs
+++ b/src/SMAPI/Framework/ModLoading/ModResolver.cs
@@ -58,11 +58,11 @@ namespace StardewModdingAPI.Framework.ModLoading
         /// <param name="mods">The mod manifests to validate.</param>
         /// <param name="apiVersion">The current SMAPI version.</param>
         /// <param name="getUpdateUrl">Get an update URL for an update key (if valid).</param>
-        /// <param name="getFilePathLookup">Get a file path lookup for the given directory.</param>
+        /// <param name="getFileLookup">Get a file lookup for the given directory.</param>
         /// <param name="validateFilesExist">Whether to validate that files referenced in the manifest (like <see cref="IManifest.EntryDll"/>) exist on disk. This can be disabled to only validate the manifest itself.</param>
         [SuppressMessage("ReSharper", "ConstantConditionalAccessQualifier", Justification = "Manifest values may be null before they're validated.")]
         [SuppressMessage("ReSharper", "ConditionIsAlwaysTrueOrFalse", Justification = "Manifest values may be null before they're validated.")]
-        public void ValidateManifests(IEnumerable<IModMetadata> mods, ISemanticVersion apiVersion, Func<string, string?> getUpdateUrl, Func<string, IFilePathLookup> getFilePathLookup, bool validateFilesExist = true)
+        public void ValidateManifests(IEnumerable<IModMetadata> mods, ISemanticVersion apiVersion, Func<string, string?> getUpdateUrl, Func<string, IFileLookup> getFileLookup, bool validateFilesExist = true)
         {
             mods = mods.ToArray();
 
@@ -147,9 +147,9 @@ namespace StardewModdingAPI.Framework.ModLoading
                         // file doesn't exist
                         if (validateFilesExist)
                         {
-                            IFilePathLookup pathLookup = getFilePathLookup(mod.DirectoryPath);
-                            string fileName = pathLookup.GetFilePath(mod.Manifest.EntryDll!);
-                            if (!File.Exists(Path.Combine(mod.DirectoryPath, fileName)))
+                            IFileLookup pathLookup = getFileLookup(mod.DirectoryPath);
+                            FileInfo file = pathLookup.GetFile(mod.Manifest.EntryDll!);
+                            if (!file.Exists)
                             {
                                 mod.SetStatus(ModMetadataStatus.Failed, ModFailReason.InvalidManifest, $"its DLL '{mod.Manifest.EntryDll}' doesn't exist.");
                                 continue;
diff --git a/src/SMAPI/Framework/SCore.cs b/src/SMAPI/Framework/SCore.cs
index 0465b6f1..3c6e1b6c 100644
--- a/src/SMAPI/Framework/SCore.cs
+++ b/src/SMAPI/Framework/SCore.cs
@@ -405,7 +405,7 @@ namespace StardewModdingAPI.Framework
                 mods = mods.Where(p => !p.IsIgnored).ToArray();
 
                 // load mods
-                resolver.ValidateManifests(mods, Constants.ApiVersion, toolkit.GetUpdateUrl, getFilePathLookup: this.GetFilePathLookup);
+                resolver.ValidateManifests(mods, Constants.ApiVersion, toolkit.GetUpdateUrl, getFileLookup: this.GetFileLookup);
                 mods = resolver.ProcessDependencies(mods, modDatabase).ToArray();
                 this.LoadMods(mods, this.Toolkit.JsonHelper, this.ContentCore, modDatabase);
 
@@ -1253,7 +1253,7 @@ namespace StardewModdingAPI.Framework
                     onLoadingFirstAsset: this.InitializeBeforeFirstAssetLoaded,
                     onAssetLoaded: this.OnAssetLoaded,
                     onAssetsInvalidated: this.OnAssetsInvalidated,
-                    getFilePathLookup: this.GetFilePathLookup,
+                    getFileLookup: this.GetFileLookup,
                     requestAssetOperations: this.RequestAssetOperations
                 );
                 if (this.ContentCore.Language != this.Translator.LocaleEnum)
@@ -1754,11 +1754,11 @@ namespace StardewModdingAPI.Framework
             if (mod.IsContentPack)
             {
                 IMonitor monitor = this.LogManager.GetMonitor(mod.DisplayName);
-                IFilePathLookup relativePathCache = this.GetFilePathLookup(mod.DirectoryPath);
+                IFileLookup fileLookup = this.GetFileLookup(mod.DirectoryPath);
                 GameContentHelper gameContentHelper = new(this.ContentCore, mod, mod.DisplayName, monitor, this.Reflection);
-                IModContentHelper modContentHelper = new ModContentHelper(this.ContentCore, mod.DirectoryPath, mod, mod.DisplayName, gameContentHelper.GetUnderlyingContentManager(), relativePathCache, this.Reflection);
+                IModContentHelper modContentHelper = new ModContentHelper(this.ContentCore, mod.DirectoryPath, mod, mod.DisplayName, gameContentHelper.GetUnderlyingContentManager(), this.Reflection);
                 TranslationHelper translationHelper = new(mod, contentCore.GetLocale(), contentCore.Language);
-                IContentPack contentPack = new ContentPack(mod.DirectoryPath, manifest, modContentHelper, translationHelper, jsonHelper, relativePathCache);
+                IContentPack contentPack = new ContentPack(mod.DirectoryPath, manifest, modContentHelper, translationHelper, jsonHelper, fileLookup);
                 mod.SetMod(contentPack, monitor, translationHelper);
                 this.ModRegistry.Add(mod);
 
@@ -1771,16 +1771,13 @@ namespace StardewModdingAPI.Framework
             else
             {
                 // get mod info
-                string assemblyPath = Path.Combine(
-                    mod.DirectoryPath,
-                    this.GetFilePathLookup(mod.DirectoryPath).GetFilePath(manifest.EntryDll!)
-                );
+                FileInfo assemblyFile = this.GetFileLookup(mod.DirectoryPath).GetFile(manifest.EntryDll!);
 
                 // load mod
                 Assembly modAssembly;
                 try
                 {
-                    modAssembly = assemblyLoader.Load(mod, assemblyPath, assumeCompatible: mod.DataRecord?.Status == ModStatus.AssumeCompatible);
+                    modAssembly = assemblyLoader.Load(mod, assemblyFile, assumeCompatible: mod.DataRecord?.Status == ModStatus.AssumeCompatible);
                     this.ModRegistry.TrackAssemblies(mod, modAssembly);
                 }
                 catch (IncompatibleInstructionException) // details already in trace logs
@@ -1799,7 +1796,7 @@ namespace StardewModdingAPI.Framework
                 catch (Exception ex)
                 {
                     errorReasonPhrase = "its DLL couldn't be loaded.";
-                    if (ex is BadImageFormatException && !EnvironmentUtility.Is64BitAssembly(assemblyPath))
+                    if (ex is BadImageFormatException && !EnvironmentUtility.Is64BitAssembly(assemblyFile.FullName))
                         errorReasonPhrase = "it needs to be updated for 64-bit mode.";
 
                     errorDetails = $"Error: {ex.GetLogSummary()}";
@@ -1837,12 +1834,11 @@ namespace StardewModdingAPI.Framework
                     {
                         IModEvents events = new ModEvents(mod, this.EventManager);
                         ICommandHelper commandHelper = new CommandHelper(mod, this.CommandManager);
-                        IFilePathLookup relativePathLookup = this.GetFilePathLookup(mod.DirectoryPath);
 #pragma warning disable CS0612 // deprecated code
                         ContentHelper contentHelper = new(contentCore, mod.DirectoryPath, mod, monitor, this.Reflection);
 #pragma warning restore CS0612
                         GameContentHelper gameContentHelper = new(contentCore, mod, mod.DisplayName, monitor, this.Reflection);
-                        IModContentHelper modContentHelper = new ModContentHelper(contentCore, mod.DirectoryPath, mod, mod.DisplayName, gameContentHelper.GetUnderlyingContentManager(), relativePathLookup, this.Reflection);
+                        IModContentHelper modContentHelper = new ModContentHelper(contentCore, mod.DirectoryPath, mod, mod.DisplayName, gameContentHelper.GetUnderlyingContentManager(), this.Reflection);
                         IContentPackHelper contentPackHelper = new ContentPackHelper(
                             mod: mod,
                             contentPacks: new Lazy<IContentPack[]>(GetContentPacks),
@@ -1896,13 +1892,13 @@ namespace StardewModdingAPI.Framework
 
             // create mod helpers
             IMonitor packMonitor = this.LogManager.GetMonitor(packManifest.Name);
-            IFilePathLookup relativePathCache = this.GetFilePathLookup(packDirPath);
             GameContentHelper gameContentHelper = new(contentCore, fakeMod, packManifest.Name, packMonitor, this.Reflection);
-            IModContentHelper packContentHelper = new ModContentHelper(contentCore, packDirPath, fakeMod, packManifest.Name, gameContentHelper.GetUnderlyingContentManager(), relativePathCache, this.Reflection);
+            IModContentHelper packContentHelper = new ModContentHelper(contentCore, packDirPath, fakeMod, packManifest.Name, gameContentHelper.GetUnderlyingContentManager(), this.Reflection);
             TranslationHelper packTranslationHelper = new(fakeMod, contentCore.GetLocale(), contentCore.Language);
 
             // add content pack
-            ContentPack contentPack = new(packDirPath, packManifest, packContentHelper, packTranslationHelper, this.Toolkit.JsonHelper, relativePathCache);
+            IFileLookup fileLookup = this.GetFileLookup(packDirPath);
+            ContentPack contentPack = new(packDirPath, packManifest, packContentHelper, packTranslationHelper, this.Toolkit.JsonHelper, fileLookup);
             this.ReloadTranslationsForTemporaryContentPack(parentMod, contentPack);
             parentMod.FakeContentPacks.Add(new WeakReference<ContentPack>(contentPack));
 
@@ -2061,13 +2057,13 @@ namespace StardewModdingAPI.Framework
             return translations;
         }
 
-        /// <summary>Get a file path lookup for the given directory.</summary>
+        /// <summary>Get a file lookup for the given directory.</summary>
         /// <param name="rootDirectory">The root path to scan.</param>
-        private IFilePathLookup GetFilePathLookup(string rootDirectory)
+        private IFileLookup GetFileLookup(string rootDirectory)
         {
             return this.Settings.UseCaseInsensitivePaths
-                ? CaseInsensitivePathLookup.GetCachedFor(rootDirectory)
-                : MinimalPathLookup.Instance;
+                ? CaseInsensitiveFileLookup.GetCachedFor(rootDirectory)
+                : MinimalFileLookup.GetCachedFor(rootDirectory);
         }
 
         /// <summary>Get the map display device which applies SMAPI features like tile rotation to loaded maps.</summary>