diff --git a/Documentation/Contributing/Debugging.md b/Documentation/Contributing/Debugging.md
index 710dbcd5..5e77d0d5 100644
--- a/Documentation/Contributing/Debugging.md
+++ b/Documentation/Contributing/Debugging.md
@@ -11,7 +11,7 @@ Some environment variables that help with debugging. Use these as e.g. `XTL_FOO=
 ### Disk
 
 - `XTL_DEBUG_TMP`: Set to `1` to log details when xtool creates/destroys temporary directories.
-- `XTL_TMPDIR`: Control the location where xtool stores temporary directories. We also respect `TMPDIR` and (on Linux) `XDG_CACHE_HOME`.
+- `XTL_TMPDIR`: Control the location where xtool stores temporary directories. We also respect `XDG_CACHE_HOME` on Linux.
 
 ### Networking
 
diff --git a/Sources/XUtils/XToolCache.swift b/Sources/XUtils/XToolCache.swift
index 3687ad70..cb8d807d 100644
--- a/Sources/XUtils/XToolCache.swift
+++ b/Sources/XUtils/XToolCache.swift
@@ -3,20 +3,20 @@ import Foundation
 package enum XToolCache {
     package static var directory: URL {
         let env = ProcessInfo.processInfo.environment
-        if let tmpdir = env["XTL_TMPDIR"] ?? env["TMPDIR"] {
+        if let tmpdir = env["XTL_TMPDIR"], !tmpdir.isEmpty {
             return URL(fileURLWithPath: tmpdir).appendingPathComponent("sh.xtool")
         }
         #if os(Linux)
-        // On Linux, /tmp is commonly a tmpfs mount while ~/.swiftpm lives on ext4.
-        // Foundation's FileManager.copyItem uses sendfile(2) internally, which returns
-        // EINVAL when copying between different filesystem types (e.g. tmpfs → ext4).
-        // This causes `swift sdk install` to fail on distros like Linux Mint (#181).
-        // Using a cache dir on the home filesystem avoids the cross-fs copy entirely.
-        let xdgCache = env["XDG_CACHE_HOME"].map { URL(fileURLWithPath: $0) }
-            ?? FileManager.default.homeDirectoryForCurrentUser.appendingPathComponent(".cache")
-        return xdgCache.appendingPathComponent("xtool")
+        let xdgCache: URL
+        if let xdgCachePath = env["XDG_CACHE_HOME"],
+           (xdgCachePath as NSString).isAbsolutePath {
+            xdgCache = URL(filePath: xdgCachePath)
+        } else {
+            xdgCache = FileManager.default.homeDirectoryForCurrentUser.appendingPathComponent(".cache")
+        }
+        return xdgCache.appending(component: "xtool")
         #else
-        return FileManager.default.temporaryDirectory.appendingPathComponent("sh.xtool")
+        return URL.cachesDirectory.appending(component: "sh.xtool")
         #endif
     }
 }