diff --git a/Sources/SWBCore/LibclangVendored/Libclang.swift b/Sources/SWBCore/LibclangVendored/Libclang.swift
index de0c6a89..d65d8ed7 100644
--- a/Sources/SWBCore/LibclangVendored/Libclang.swift
+++ b/Sources/SWBCore/LibclangVendored/Libclang.swift
@@ -470,7 +470,7 @@ public final class ClangCASDatabases {
         libclang_casdatabases_dispose(dbs)
     }
 
-    public func getOndiskSize() throws -> Int? {
+    public func getOndiskSize() throws -> Int64? {
         var error: ClangCASDatabases.Error? = nil
         let ret = libclang_casdatabases_get_ondisk_size(dbs, { c_error in
             error = .operationFailed(String(cString: c_error!))
@@ -481,12 +481,12 @@ public final class ClangCASDatabases {
         if ret < 0 {
             return nil
         }
-        return Int(ret)
+        return ret
     }
 
-    public func setOndiskSizeLimit(_ limit: Int?) throws {
+    public func setOndiskSizeLimit(_ limit: Int64?) throws {
         var error: ClangCASDatabases.Error? = nil
-        libclang_casdatabases_set_ondisk_size_limit(dbs, Int64(limit ?? 0), { c_error in
+        libclang_casdatabases_set_ondisk_size_limit(dbs, limit ?? 0, { c_error in
             error = .operationFailed(String(cString: c_error!))
         })
         if let error {
diff --git a/Sources/SWBCore/Settings/CASOptions.swift b/Sources/SWBCore/Settings/CASOptions.swift
index 27acbad6..a6b7c8d3 100644
--- a/Sources/SWBCore/Settings/CASOptions.swift
+++ b/Sources/SWBCore/Settings/CASOptions.swift
@@ -34,7 +34,7 @@ public struct CASOptions: Hashable, Serializable, Encodable, Sendable {
         /// Cache directory is removed after the build is finished.
         case discarded
         /// The maximum size for the cache directory in bytes. `nil` means no limit.
-        case maxSizeBytes(Int?)
+        case maxSizeBytes(ByteCount?)
         /// The maximum size for the cache directory, in terms of percentage of the
         /// available space on the disk. Set to 100 to indicate no limit, 50 to
         /// indicate that the cache size will not be left over half the available disk
@@ -86,26 +86,22 @@ public struct CASOptions: Hashable, Serializable, Encodable, Sendable {
     /// * "0": indicates no limit
     ///
     /// Returns `nil` if the string is invalid.
-    public static func parseSizeLimit(_ sizeLimitStr: String) -> Int? {
-        if let size = Int(sizeLimitStr) {
+    public static func parseSizeLimit(_ sizeLimitStr: String) -> ByteCount? {
+        if let size = ByteCount(Int64(sizeLimitStr)) {
             return size
         }
-        guard let size = Int(sizeLimitStr.dropLast()) else {
+        guard let size = Int64(sizeLimitStr.dropLast()) else {
             return nil
         }
-        let kb = 1024
-        let mb = kb * 1024
-        let gb = mb * 1024
-        let tb = gb * 1024
-        switch sizeLimitStr.last! {
-        case "K": // kilobytes
-            return size * kb
-        case "M": // megabytes
-            return size * mb
-        case "G": // gigabytes
-            return size * gb
-        case "T": // terabytes
-            return size * tb
+        switch sizeLimitStr.last {
+        case "K":
+            return .kilobytes(size)
+        case "M":
+            return .megabytes(size)
+        case "G":
+            return .gigabytes(size)
+        case "T":
+            return .terabytes(size)
         default:
             return nil
         }
@@ -228,7 +224,7 @@ public struct CASOptions: Hashable, Serializable, Encodable, Sendable {
                 guard let sizeLimit = CASOptions.parseSizeLimit(sizeLimitStr) else {
                     throw Errors.invalidSizeLimit(sizeLimitString: sizeLimitStr, origin: origin)
                 }
-                return .maxSizeBytes(sizeLimit > 0 ? sizeLimit : nil)
+                return .maxSizeBytes(sizeLimit > .zero ? sizeLimit : nil)
             }
 
             let sizeLimitStr = scope.evaluate(BuiltinMacros.COMPILATION_CACHE_LIMIT_SIZE)
diff --git a/Sources/SWBTaskExecution/DynamicTaskSpecs/CompilationCachingDataPruner.swift b/Sources/SWBTaskExecution/DynamicTaskSpecs/CompilationCachingDataPruner.swift
index cd6c44da..6b9a2949 100644
--- a/Sources/SWBTaskExecution/DynamicTaskSpecs/CompilationCachingDataPruner.swift
+++ b/Sources/SWBTaskExecution/DynamicTaskSpecs/CompilationCachingDataPruner.swift
@@ -112,7 +112,7 @@ package final class CompilationCachingDataPruner: Sendable {
             { activityID in
                 let status: BuildOperationTaskEnded.Status
                 do {
-                    let dbSize = try casDBs.getOndiskSize()
+                    let dbSize = try ByteCount(casDBs.getOndiskSize())
                     let sizeLimit = try computeCASSizeLimit(casOptions: casOpts, dbSize: dbSize, fileSystem: fs)
                     if let dbSize, let sizeLimit, sizeLimit < dbSize {
                         activityReporter.emit(
@@ -125,7 +125,7 @@ package final class CompilationCachingDataPruner: Sendable {
                             signature: signature
                         )
                     }
-                    try casDBs.setOndiskSizeLimit(sizeLimit ?? 0)
+                    try casDBs.setOndiskSizeLimit(sizeLimit?.count ?? 0)
                     try casDBs.pruneOndiskData()
                     status = .succeeded
                 } catch {
@@ -181,8 +181,8 @@ package final class CompilationCachingDataPruner: Sendable {
             { activityID in
                 let status: BuildOperationTaskEnded.Status
                 do {
-                    let dbSize = try casDBs.getStorageSize()
-                    let sizeLimit = try computeCASSizeLimit(casOptions: casOpts, dbSize: dbSize.map{Int($0)}, fileSystem: fs)
+                    let dbSize = try ByteCount(casDBs.getStorageSize())
+                    let sizeLimit = try computeCASSizeLimit(casOptions: casOpts, dbSize: dbSize, fileSystem: fs)
                     if let dbSize, let sizeLimit, sizeLimit < dbSize {
                         activityReporter.emit(
                             diagnostic: Diagnostic(
@@ -194,7 +194,7 @@ package final class CompilationCachingDataPruner: Sendable {
                             signature: signature
                         )
                     }
-                    try casDBs.setSizeLimit(Int64(sizeLimit ?? 0))
+                    try casDBs.setSizeLimit(sizeLimit?.count ?? 0)
                     try casDBs.prune()
                     status = .succeeded
                 } catch {
@@ -250,8 +250,8 @@ package final class CompilationCachingDataPruner: Sendable {
             { activityID in
                 let status: BuildOperationTaskEnded.Status
                 do {
-                    let dbSize = (try? toolchainCAS.getOnDiskSize()).map { Int($0) }
-                    let sizeLimit = try computeCASSizeLimit(casOptions: casOpts, dbSize: dbSize, fileSystem: fs).map { Int64($0) }
+                    let dbSize = try? ByteCount(toolchainCAS.getOnDiskSize())
+                    let sizeLimit = try computeCASSizeLimit(casOptions: casOpts, dbSize: dbSize, fileSystem: fs)
                     if let dbSize, let sizeLimit, sizeLimit < dbSize {
                         activityReporter.emit(
                             diagnostic: Diagnostic(
@@ -263,7 +263,7 @@ package final class CompilationCachingDataPruner: Sendable {
                             signature: signature
                         )
                     }
-                    try toolchainCAS.setOnDiskSizeLimit(sizeLimit ?? 0)
+                    try toolchainCAS.setOnDiskSizeLimit(sizeLimit?.count ?? 0)
                     try toolchainCAS.prune()
                     status = .succeeded
                 } catch {
@@ -287,9 +287,9 @@ package final class CompilationCachingDataPruner: Sendable {
 
 fileprivate func computeCASSizeLimit(
     casOptions: CASOptions,
-    dbSize: Int?,
+    dbSize: ByteCount?,
     fileSystem fs: any FSProxy
-) throws -> Int? {
+) throws -> ByteCount? {
     guard let dbSize else { return nil }
     switch casOptions.limitingStrategy {
     case .discarded:
@@ -304,6 +304,6 @@ fileprivate func computeCASSizeLimit(
             return nil
         }
         let availableSpace = dbSize + freeSpace
-        return availableSpace * percent / 100
+        return ByteCount(availableSpace.count * Int64(percent) / 100)
     }
 }
diff --git a/Sources/SWBTaskExecution/DynamicTaskSpecs/SwiftDriverJobDynamicTaskSpec.swift b/Sources/SWBTaskExecution/DynamicTaskSpecs/SwiftDriverJobDynamicTaskSpec.swift
index e01273bc..127e3047 100644
--- a/Sources/SWBTaskExecution/DynamicTaskSpecs/SwiftDriverJobDynamicTaskSpec.swift
+++ b/Sources/SWBTaskExecution/DynamicTaskSpecs/SwiftDriverJobDynamicTaskSpec.swift
@@ -242,7 +242,7 @@ final class SwiftDriverJobDynamicTaskSpec: DynamicTaskSpec {
         // rdar://91295617 (Swift produces empty serialized diagnostics if there are none which is not parseable by clang_loadDiagnostics)
         return expectedDiagnostics.filter { filePath in
             do {
-                let shouldAdd = try fs.exists(filePath) && (try fs.getFileSize(filePath)) > 0
+                let shouldAdd = try fs.exists(filePath) && (try fs.getFileSize(filePath)) > .zero
                 return shouldAdd
             } catch {
                 return false
diff --git a/Sources/SWBUtil/ByteCount.swift b/Sources/SWBUtil/ByteCount.swift
new file mode 100644
index 00000000..feadcdd1
--- /dev/null
+++ b/Sources/SWBUtil/ByteCount.swift
@@ -0,0 +1,93 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+public struct ByteCount: Hashable, Sendable {
+    public var count: Int64
+
+    public init?(_ count: Int64?) {
+        guard let count else { return nil }
+        self.count = count
+    }
+
+    public init(_ count: Int64) {
+        self.count = count
+    }
+}
+
+extension ByteCount: Codable {
+    public init(from decoder: any Swift.Decoder) throws {
+        self.count = try .init(from: decoder)
+    }
+
+    public func encode(to encoder: any Swift.Encoder) throws {
+        try self.count.encode(to: encoder)
+    }
+}
+
+extension ByteCount: Serializable {
+    public init(from deserializer: any Deserializer) throws {
+        self.count = try .init(from: deserializer)
+    }
+
+    public func serialize<T>(to serializer: T) where T : Serializer {
+        self.count.serialize(to: serializer)
+    }
+}
+
+extension ByteCount: Comparable {
+    public static func < (lhs: ByteCount, rhs: ByteCount) -> Bool {
+        lhs.count < rhs.count
+    }
+}
+
+extension ByteCount: AdditiveArithmetic {
+    public static var zero: ByteCount {
+        Self(0)
+    }
+
+    public static func + (lhs: ByteCount, rhs: ByteCount) -> ByteCount {
+        Self(lhs.count + rhs.count)
+    }
+
+    public static func - (lhs: ByteCount, rhs: ByteCount) -> ByteCount {
+        Self(lhs.count - rhs.count)
+    }
+}
+
+extension ByteCount: CustomStringConvertible {
+    public var description: String {
+        "\(count) bytes"
+    }
+}
+
+extension ByteCount {
+    private static let kb = Int64(1024)
+    private static let mb = kb * 1024
+    private static let gb = mb * 1024
+    private static let tb = gb * 1024
+
+    public static func kilobytes(_ count: Int64) -> Self {
+        Self(kb * count)
+    }
+
+    public static func megabytes(_ count: Int64) -> Self {
+        Self(mb * count)
+    }
+
+    public static func gigabytes(_ count: Int64) -> Self {
+        Self(gb * count)
+    }
+
+    public static func terabytes(_ count: Int64) -> Self {
+        Self(tb * count)
+    }
+}
diff --git a/Sources/SWBUtil/CMakeLists.txt b/Sources/SWBUtil/CMakeLists.txt
index eae57b98..b2ad2fb6 100644
--- a/Sources/SWBUtil/CMakeLists.txt
+++ b/Sources/SWBUtil/CMakeLists.txt
@@ -19,6 +19,7 @@ add_library(SWBUtil
   AsyncOperationQueue.swift
   AsyncSingleValueCache.swift
   AsyncStreamController.swift
+  ByteCount.swift
   ByteString.swift
   Cache.swift
   Collection.swift
diff --git a/Sources/SWBUtil/FSProxy.swift b/Sources/SWBUtil/FSProxy.swift
index 974bc667..adf69e3a 100644
--- a/Sources/SWBUtil/FSProxy.swift
+++ b/Sources/SWBUtil/FSProxy.swift
@@ -255,7 +255,7 @@ public protocol FSProxy: AnyObject, Sendable {
     func isOnPotentiallyRemoteFileSystem(_ path: Path) -> Bool
 
     /// Returns the free disk space of the volume of `path` in bytes, or `nil` if the underlying FS implementation doesn't support this.
-    func getFreeDiskSpace(_ path: Path) throws -> Int?
+    func getFreeDiskSpace(_ path: Path) throws -> ByteCount?
 }
 
 public extension FSProxy {
@@ -287,7 +287,7 @@ public extension FSProxy {
         return false
     }
 
-    func getFreeDiskSpace(_ path: Path) throws -> Int? {
+    func getFreeDiskSpace(_ path: Path) throws -> ByteCount? {
         return nil
     }
 
@@ -296,8 +296,8 @@ public extension FSProxy {
         return isSymlink(path, &exists)
     }
 
-    func getFileSize(_ path: Path) throws -> Int64 {
-        try Int64(getFileInfo(path).statBuf.st_size)
+    func getFileSize(_ path: Path) throws -> ByteCount {
+        try ByteCount(Int64(getFileInfo(path).statBuf.st_size))
     }
 }
 
@@ -860,12 +860,12 @@ class LocalFS: FSProxy, @unchecked Sendable {
         #endif
     }
 
-    func getFreeDiskSpace(_ path: Path) throws -> Int? {
+    func getFreeDiskSpace(_ path: Path) throws -> ByteCount? {
         let systemAttributes = try fileManager.attributesOfFileSystem(forPath: path.str)
         guard let freeSpace = (systemAttributes[FileAttributeKey.systemFreeSize] as? NSNumber)?.int64Value else {
             return nil
         }
-        return Int(freeSpace)
+        return ByteCount(freeSpace)
     }
 }
 
diff --git a/Tests/SWBUtilTests/MsgPackSerializationTests.swift b/Tests/SWBUtilTests/MsgPackSerializationTests.swift
index 7894c817..6212edcd 100644
--- a/Tests/SWBUtilTests/MsgPackSerializationTests.swift
+++ b/Tests/SWBUtilTests/MsgPackSerializationTests.swift
@@ -371,7 +371,7 @@ import SWBUtil
                 "one": IntRange(uncheckedBounds: (1, 4)),
                 "two": IntRange(uncheckedBounds: (-13, -2)),
                 "three": IntRange(uncheckedBounds: (-99, -3)),
-                "infinity": IntRange(uncheckedBounds: (0, 43793218932)),
+                "infinity": IntRange(uncheckedBounds: (0, 2147483647)),
             ]
 
             // Serialize!