fix(windows): preserve drive-root private runtime paths

Join the admitted parent and generated child name without duplicating a drive-root separator. Reuse that name for handle-relative creation and path provenance.

Add native snapshot, readback, and cleanup coverage through the Ghidra dot-prefixed temp fallback, plus a session-root contract regression.

Fixes #1690

native/windows/src/filesystem.cc

@@ -219,9 +219,10 @@ std::unique_ptr<Runtime> createRuntime(const std::wstring& parentPath, const std
   require(BCryptGenRandom(nullptr, random.data(), random.size(), BCRYPT_USE_SYSTEM_PREFERRED_RNG) == 0,
           "Generate runtime identity failed", parentPath, ERROR_GEN_FAILURE);
   auto result = std::make_unique<Runtime>();
-  result->path = parent->path + L"\\" + prefix + hex(random.data(), random.size());
+  const auto name = prefix + hex(random.data(), random.size());
+  result->path = parent->path + (parent->path.back() == L'\\' ? L"" : L"\\") + name;
   Security security;
-  result->directory = createRelative(parent->get(), prefix + hex(random.data(), random.size()),
+  result->directory = createRelative(parent->get(), name,
                                      DELETE | FILE_LIST_DIRECTORY | FILE_READ_ATTRIBUTES | READ_CONTROL,
                                      true, security, result->path);
   try {

scripts/verify-windows-native.mjs

@@ -17,7 +17,7 @@ import {
   open,
 } from "node:fs/promises";
 import { tmpdir } from "node:os";
-import { join, resolve } from "node:path";
+import { dirname, join, parse, resolve } from "node:path";
 import { pathToFileURL } from "node:url";
 import { verifyWindowsProtocolInput } from "./lib/windows-protocol-input.mjs";
 
@@ -33,6 +33,9 @@ const native = requireWindowsNativeAuthority();
 const { WindowsPrivateRuntime, windowsPrivateRuntime } = await import(
   pathToFileURL(join(packageRoot, "dist/windows/WindowsPrivateRuntime.js"))
 );
+const { ghidraSessionRoot } = await import(
+  pathToFileURL(join(packageRoot, "dist/ghidra/GhidraSessionRoot.js"))
+);
 const workspace = await mkdtemp(join(tmpdir(), "rea-native-conformance-"));
 const environment = Object.entries(process.env)
   .filter(([, value]) => value !== undefined)
@@ -136,6 +139,47 @@ process.stdout.write(JSON.stringify({executable:basename(process.execPath),abiVe
   ])
     assert.throws(() => native.call("open", [rejected]));
   report.controls.ordinaryDriveSeparatorsAndRequestedIdentity = true;
+  const driveRoot = parse(workspace).root;
+  const runtimeParent = ghidraSessionRoot({
+    base: join(driveRoot, ".Tmp", "scratch"),
+  });
+  assert.equal(runtimeParent, driveRoot);
+  const driveRootRuntime = native.call("runtime_create", [
+    runtimeParent,
+    "rea-drive-root-",
+  ]);
+  try {
+    assert.equal(driveRootRuntime.path.startsWith(`${driveRoot}\\`), false);
+    assert.equal(dirname(driveRootRuntime.path), driveRoot);
+    const snapshot = await native.call("runtime_snapshot", [
+      driveRootRuntime.handle,
+      source,
+      "probe.bin",
+    ]);
+    const sourceBytes = await readFile(source);
+    assert.equal(
+      snapshot.sha256,
+      createHash("sha256").update(sourceBytes).digest("hex"),
+    );
+    assert.equal(snapshot.source.requestedPath, source);
+    const readback = native.call("runtime_open", [
+      driveRootRuntime.handle,
+      "probe.bin",
+    ]);
+    try {
+      assert.equal(readback.size, sourceBytes.byteLength);
+      assert.deepEqual(
+        native.call("read", [readback.handle, 0, 65536]),
+        sourceBytes.subarray(0, 65536),
+      );
+    } finally {
+      native.call("close", [readback.handle]);
+    }
+  } finally {
+    native.call("runtime_close", [driveRootRuntime.handle]);
+  }
+  assert.equal(await exists(driveRootRuntime.path), false);
+  report.controls.driveRootRuntimeParent = true;
   const snapshotOwner = WindowsPrivateRuntime.create(
     workspace.replace(/\\/u, "/"),
     "single-flight-",

src/ghidra/GhidraSessionRoot.test.ts

@@ -44,6 +44,15 @@ describe("ghidraSessionRoot", () => {
     ).toBe(posixBase("Users", "operator"));
   });
 
+  it("can select a filesystem root when the inherited temp starts with a dot-prefixed element", () => {
+    expect(
+      ghidraSessionRoot({
+        base: posixBase(".Tmp", "scratch"),
+        platform: "win32",
+      }),
+    ).toBe(resolve(sep));
+  });
+
   it.skipIf(!POSIX)("prefers the platform temp directory by default", () => {
     expect(
       ghidraSessionRoot({ base: posixBase("home", "operator", ".cache") }),