diff --git a/runtime/storage.js b/runtime/storage.js
index 090cd16ad..f0684f257 100644
--- a/runtime/storage.js
+++ b/runtime/storage.js
@@ -116,7 +116,10 @@ export async function acquireLock(lockPath, options = {}) {
   const staleMs = options.staleMs ?? 120_000;
   const platform = options.platform ?? process.platform;
   const mkdir = options.mkdir ?? fs.mkdir;
+  const remove = options.rm ?? fs.rm;
+  const transientPermissionMs = options.transientPermissionMs ?? 1_000;
   const started = Date.now();
+  let firstUnconfirmedEpermAt = null;
   const token = randomUUID();
   await mkdir(path.dirname(lockPath), { recursive: true, mode: 0o700 });
 
@@ -128,10 +131,27 @@ export async function acquireLock(lockPath, options = {}) {
       mkdirError = error;
     }
     if (mkdirError) {
-      const contended = mkdirError?.code === "EEXIST";
-      const windowsDeleteRace = platform === "win32" && mkdirError?.code === "EPERM";
-      if (!contended && !windowsDeleteRace) throw mkdirError;
-      if (contended) await reapStaleLock(lockPath, staleMs, platform);
+      let contended = mkdirError?.code === "EEXIST";
+      const windowsEperm = platform === "win32" && mkdirError?.code === "EPERM";
+      if (windowsEperm) {
+        let observed = "unknown";
+        try {
+          observed = (await fs.lstat(lockPath)).isDirectory() ? "directory" : "other";
+        } catch (probeError) {
+          if (probeError?.code !== "ENOENT" && !WINDOWS_TRANSIENT_FS_ERRORS.has(probeError?.code)) throw mkdirError;
+        }
+        if (observed === "other") throw mkdirError;
+        contended = observed === "directory";
+        if (!contended) {
+          firstUnconfirmedEpermAt ??= Date.now();
+          if (Date.now() - firstUnconfirmedEpermAt >= transientPermissionMs) throw mkdirError;
+        }
+      }
+      if (!contended && !windowsEperm) throw mkdirError;
+      if (contended) {
+        firstUnconfirmedEpermAt = null;
+        await reapStaleLock(lockPath, staleMs, platform);
+      }
       if (Date.now() - started >= timeoutMs) {
         const timeout = new Error(`Timed out waiting for lock ${lockPath}`);
         timeout.code = "LOCK_TIMEOUT";
@@ -159,10 +179,12 @@ export async function acquireLock(lockPath, options = {}) {
         // Locks are leases. A stale-lock reaper may already have removed it,
         // which readJson represents as null; other failures remain actionable.
         const current = await readJson(path.join(lockPath, "owner.json"), null);
-        if (current?.token === token) await fs.rm(lockPath, { recursive: true, force: true });
+        if (current?.token === token) {
+          await remove(lockPath, { recursive: true, force: true, maxRetries: 5, retryDelay: 50 });
+        }
       };
     } catch (error) {
-      await fs.rm(lockPath, { recursive: true, force: true }).catch(() => {});
+      await remove(lockPath, { recursive: true, force: true, maxRetries: 5, retryDelay: 50 }).catch(() => {});
       throw error;
     }
   }
diff --git a/test/gstack2-runtime-cleanup-boundary.test.ts b/test/gstack2-runtime-cleanup-boundary.test.ts
index 0b60bfecd..df1e0ac2b 100644
--- a/test/gstack2-runtime-cleanup-boundary.test.ts
+++ b/test/gstack2-runtime-cleanup-boundary.test.ts
@@ -37,6 +37,7 @@ describe("runtime cleanup boundary", () => {
     const home = await temporaryHome();
     const lockPath = path.join(home, "locks", "windows-race.lock");
     let mkdirAttempts = 0;
+    let releaseOptions: Record<string, unknown> | undefined;
     const release = await acquireLock(lockPath, {
       platform: "win32",
       mkdir: async (target: string, options: Record<string, unknown>) => {
@@ -45,9 +46,25 @@ describe("runtime cleanup boundary", () => {
         }
         return fs.mkdir(target, options);
       },
+      rm: async (target: string, options: Record<string, unknown>) => {
+        releaseOptions = options;
+        return fs.rm(target, options);
+      },
     });
     expect(mkdirAttempts).toBe(2);
     await release();
+    expect(releaseOptions).toMatchObject({ recursive: true, force: true, maxRetries: 5, retryDelay: 50 });
+
+    await expect(acquireLock(path.join(home, "locks", "permanently-denied.lock"), {
+      platform: "win32",
+      transientPermissionMs: 20,
+      mkdir: async (target: string, options: Record<string, unknown>) => {
+        if (target.endsWith("permanently-denied.lock")) {
+          throw Object.assign(new Error("permanent permission denial"), { code: "EPERM" });
+        }
+        return fs.mkdir(target, options);
+      },
+    })).rejects.toMatchObject({ code: "EPERM" });
 
     let renameAttempts = 0;
     await renameWithRetry("source", "destination", {
diff --git a/test/gstack2-runtime-install.test.ts b/test/gstack2-runtime-install.test.ts
index d8cb3c49f..d62d605a0 100644
--- a/test/gstack2-runtime-install.test.ts
+++ b/test/gstack2-runtime-install.test.ts
@@ -390,7 +390,7 @@ describe("GStack 2 managed runtime installer", () => {
         const originalMode = (await fs.stat(cli)).mode & 0o777;
         await fs.chmod(cli, originalMode === 0o600 ? 0o644 : 0o600);
         await expect(validateRuntimeBundle(result.path, { version: "2.0.0", platform: "win32" })).resolves.toBe(true);
-        await expect(validateRuntimeBundle(result.path, { version: "2.0.0" })).rejects.toMatchObject({
+        await expect(validateRuntimeBundle(result.path, { version: "2.0.0", platform: "linux" })).rejects.toMatchObject({
           code: "INSTALL_VALIDATION_FAILED",
         });
         await fs.chmod(cli, originalMode);