diff --git a/src/infra/wsl.test.ts b/src/infra/wsl.test.ts
index 63b7b9544b0..d026cf4bbb1 100644
--- a/src/infra/wsl.test.ts
+++ b/src/infra/wsl.test.ts
@@ -59,6 +59,13 @@ describe("wsl detection", () => {
     expect(readFileSyncMock).toHaveBeenCalledWith("/proc/version", "utf8");
   });
 
+  it("returns false when sync detection cannot read /proc/version", () => {
+    readFileSyncMock.mockImplementationOnce(() => {
+      throw new Error("ENOENT");
+    });
+    expect(isWSLSync()).toBe(false);
+  });
+
   it.each(["Linux version 6.6.0-1-microsoft-standard-WSL2", "Linux version 6.6.0-1-wsl2"])(
     "detects WSL2 sync from kernel version: %s",
     (kernelVersion) => {
@@ -68,6 +75,12 @@ describe("wsl detection", () => {
     },
   );
 
+  it("returns false for WSL2 sync when WSL is detected but no WSL2 markers exist", () => {
+    readFileSyncMock.mockReturnValueOnce("Linux version 4.4.0-19041-Microsoft");
+    readFileSyncMock.mockReturnValueOnce("Linux version 4.4.0-19041-Microsoft");
+    expect(isWSL2Sync()).toBe(false);
+  });
+
   it("returns false for sync detection on non-linux platforms", () => {
     setPlatform("darwin");
     expect(isWSLSync()).toBe(false);
@@ -88,6 +101,13 @@ describe("wsl detection", () => {
     expect(readFileMock).toHaveBeenCalledTimes(2);
   });
 
+  it("short-circuits async detection from WSL env vars without reading osrelease", async () => {
+    process.env.WSL_DISTRO_NAME = "Ubuntu";
+
+    await expect(isWSL()).resolves.toBe(true);
+    expect(readFileMock).not.toHaveBeenCalled();
+  });
+
   it("returns false when async WSL detection cannot read osrelease", async () => {
     readFileMock.mockRejectedValueOnce(new Error("ENOENT"));
     await expect(isWSL()).resolves.toBe(false);