diff --git a/src/lib/synced-state-location.ts b/src/lib/synced-state-location.ts
index 21b4bae24fb..1da04f759c7 100644
--- a/src/lib/synced-state-location.ts
+++ b/src/lib/synced-state-location.ts
@@ -1,6 +1,11 @@
 import { lstatSync, realpathSync } from "node:fs";
 import { homedir } from "node:os";
-import { join, resolve } from "node:path";
+// POSIX path operations on purpose: every path this module classifies is a macOS path. The
+// host's own path module would build backslash or drive-letter paths on Windows and make the
+// injected-platform tests compare different strings there (dev CI windows 5/9 after #6398).
+import { posix } from "node:path";
+
+const { join, resolve } = posix;
 
 /**
  * Where a state directory sits relative to the folders macOS keeps in sync with a cloud.
diff --git a/tests/lib/synced-state-location.test.ts b/tests/lib/synced-state-location.test.ts
index 6811249ef0d..5b157471d08 100644
--- a/tests/lib/synced-state-location.test.ts
+++ b/tests/lib/synced-state-location.test.ts
@@ -64,4 +64,17 @@ describe("synced state directory detection (#6314)", () => {
       expect(text).not.toContain("/Users/");
     }
   });
+
+  test("classification uses macOS path rules whatever host runs it", () => {
+    // The probe says darwin while this may run on Windows: no separator or drive-letter handling
+    // from the host may reach the paths being compared.
+    const seen: string[] = [];
+    const entryExists = (path: string): boolean => {
+      seen.push(path);
+      return desktopDocumentsSynced(path);
+    };
+    expect(syncedStateLocation(`${HOME}/Documents/state`, probe({ entryExists }))).toBe("icloud-desktop-documents");
+    expect(seen.length).toBeGreaterThan(0);
+    expect(seen.every((path) => path.startsWith(`${HOME}/`) && !path.includes("\\"))).toBe(true);
+  });
 });