diff --git a/packages/stack-cli/src/lib/dev-env-state.test.ts b/packages/stack-cli/src/lib/dev-env-state.test.ts
index cfd1e2553..dcc54fcce 100644
--- a/packages/stack-cli/src/lib/dev-env-state.test.ts
+++ b/packages/stack-cli/src/lib/dev-env-state.test.ts
@@ -158,6 +158,38 @@ describe("dev env state", () => {
     expect(state.localDashboard?.version).toBeUndefined();
   });
 
+  it("drops a localDashboard whose version is a non-string", () => {
+    useTempStateFile();
+    const statePath = process.env.STACK_DEV_ENVS_PATH;
+    if (statePath == null) {
+      throw new Error("STACK_DEV_ENVS_PATH should be set by useTempStateFile().");
+    }
+    // A hand-edited / cross-version file with a non-string version would
+    // otherwise reach parseVersionCore (version.trim()) and throw, crashing
+    // `stack dev` outside the auto-update fail-open guard. Treat as no record.
+    writeFileSync(statePath, JSON.stringify({
+      version: 1,
+      localDashboard: { port: 26700, secret: "s", pid: 999, startedAtMillis: 1, version: 2 },
+      projectsByConfigPath: {},
+    }), { mode: 0o600 });
+    expect(readDevEnvState().localDashboard).toBeUndefined();
+  });
+
+  it("drops a structurally malformed localDashboard on read", () => {
+    useTempStateFile();
+    const statePath = process.env.STACK_DEV_ENVS_PATH;
+    if (statePath == null) {
+      throw new Error("STACK_DEV_ENVS_PATH should be set by useTempStateFile().");
+    }
+    // Missing secret + non-numeric pid: not a usable dashboard record.
+    writeFileSync(statePath, JSON.stringify({
+      version: 1,
+      localDashboard: { port: 26700, pid: "nope", startedAtMillis: 1 },
+      projectsByConfigPath: {},
+    }), { mode: 0o600 });
+    expect(readDevEnvState().localDashboard).toBeUndefined();
+  });
+
   it("writes state as owner-readable JSON", () => {
     useTempStateFile();
     writeDevEnvState({
diff --git a/packages/stack-cli/src/lib/dev-env-state.ts b/packages/stack-cli/src/lib/dev-env-state.ts
index ee655b055..7bf46c8af 100644
--- a/packages/stack-cli/src/lib/dev-env-state.ts
+++ b/packages/stack-cli/src/lib/dev-env-state.ts
@@ -54,6 +54,31 @@ function isCliUpdateCheckCache(value: unknown): value is CliUpdateCheckCache {
   );
 }
 
+type LocalDashboardState = NonNullable<DevEnvState["localDashboard"]>;
+
+// Validate the on-disk dashboard record, mirroring isCliUpdateCheckCache: a
+// hand-edited or cross-version state file could carry wrong-typed fields. In
+// particular a non-string `version` flows into shouldRestartDashboard ->
+// isVersionNewer -> parseVersionCore (version.trim()) inside
+// startDashboardIfNeeded, which is not behind the auto-update fail-open guard,
+// so it would throw and crash `stack dev`. Treat anything malformed as "no
+// dashboard recorded" (a fresh one is then started).
+function isLocalDashboardState(value: unknown): value is LocalDashboardState {
+  if (value == null || typeof value !== "object") return false;
+  const candidate = value as Record<string, unknown>;
+  return (
+    typeof candidate.port === "number" &&
+    Number.isFinite(candidate.port) &&
+    typeof candidate.secret === "string" &&
+    typeof candidate.pid === "number" &&
+    Number.isFinite(candidate.pid) &&
+    typeof candidate.startedAtMillis === "number" &&
+    Number.isFinite(candidate.startedAtMillis) &&
+    (candidate.logPath === undefined || typeof candidate.logPath === "string") &&
+    (candidate.version === undefined || typeof candidate.version === "string")
+  );
+}
+
 export function readDevEnvState(): DevEnvState {
   const path = devEnvStatePath();
   if (!existsSync(path)) {
@@ -70,7 +95,7 @@ export function readDevEnvState(): DevEnvState {
     version: 1,
     anonymousRefreshToken: typeof parsed.anonymousRefreshToken === "string" ? parsed.anonymousRefreshToken : undefined,
     anonymousApiBaseUrl: typeof parsed.anonymousApiBaseUrl === "string" ? parsed.anonymousApiBaseUrl : undefined,
-    localDashboard: parsed.localDashboard,
+    localDashboard: isLocalDashboardState(parsed.localDashboard) ? parsed.localDashboard : undefined,
     cliUpdateCheck: isCliUpdateCheckCache(parsed.cliUpdateCheck) ? parsed.cliUpdateCheck : undefined,
     projectsByConfigPath: parsed.projectsByConfigPath ?? {},
   };
diff --git a/packages/stack-cli/src/lib/self-update.test.ts b/packages/stack-cli/src/lib/self-update.test.ts
index 3feac44f6..dc90f8cee 100644
--- a/packages/stack-cli/src/lib/self-update.test.ts
+++ b/packages/stack-cli/src/lib/self-update.test.ts
@@ -156,12 +156,27 @@ describe("buildNpxInvocation", () => {
     ]);
   });
 
-  it("uses npx.cmd on Windows", () => {
+  it("uses npx.cmd and requests a shell on Windows (needed to spawn a .cmd post-CVE-2024-27980)", () => {
     const spy = vi.spyOn(process, "platform", "get").mockReturnValue("win32");
     try {
-      expect(buildNpxInvocation({
+      const invocation = buildNpxInvocation({
         packageName: "@hexclave/cli", version: "1.0.0", binName: "stack", forwardArgs: [],
-      }).command).toBe("npx.cmd");
+      });
+      expect(invocation.command).toBe("npx.cmd");
+      expect(invocation.shell).toBe(true);
+    } finally {
+      spy.mockRestore();
+    }
+  });
+
+  it("spawns npx directly without a shell off Windows", () => {
+    const spy = vi.spyOn(process, "platform", "get").mockReturnValue("linux");
+    try {
+      const invocation = buildNpxInvocation({
+        packageName: "@hexclave/cli", version: "1.0.0", binName: "stack", forwardArgs: [],
+      });
+      expect(invocation.command).toBe("npx");
+      expect(invocation.shell).toBe(false);
     } finally {
       spy.mockRestore();
     }
diff --git a/packages/stack-cli/src/lib/self-update.ts b/packages/stack-cli/src/lib/self-update.ts
index 7abce0824..aca6cc160 100644
--- a/packages/stack-cli/src/lib/self-update.ts
+++ b/packages/stack-cli/src/lib/self-update.ts
@@ -142,6 +142,11 @@ export async function resolveLatestVersion(
 export type NpxInvocation = {
   command: string,
   args: string[],
+  // Windows' launcher is `npx.cmd`; after CVE-2024-27980 Node refuses to spawn
+  // a .cmd/.bat directly (EINVAL) unless `shell` is set, so the re-exec has to
+  // go through the shell there. `args` stays a clean argv array — runReexec
+  // quotes it for the shell at spawn time.
+  shell: boolean,
 };
 
 export function buildNpxInvocation(opts: {
@@ -150,9 +155,11 @@ export function buildNpxInvocation(opts: {
   binName: string,
   forwardArgs: string[],
 }): NpxInvocation {
-  const command = process.platform === "win32" ? "npx.cmd" : "npx";
+  const isWindows = process.platform === "win32";
+  const command = isWindows ? "npx.cmd" : "npx";
   return {
     command,
+    shell: isWindows,
     args: [
       "--yes",
       // Override any global npm "cooldown" for this call only — we always want
@@ -201,11 +208,23 @@ type ReexecResult =
   | { exited: true, code: number }
   | { exited: false, error: string };
 
+// Quote an argument for the single cmd.exe command line that Node builds when
+// `spawn` runs with `shell: true` on Windows — it joins argv with spaces and
+// does not quote, so an unquoted path/arg with a space would be split. Wrap
+// anything that isn't a plain token (and the empty string) in double quotes,
+// escaping embedded quotes. A no-op on the non-shell (POSIX) path.
+function quoteShellArg(arg: string): string {
+  if (arg !== "" && !/[\s"&|<>^()]/.test(arg)) return arg;
+  return `"${arg.replace(/"/g, '\\"')}"`;
+}
+
 function runReexec(invocation: NpxInvocation): Promise<ReexecResult> {
   return new Promise((resolvePromise) => {
-    const child = spawn(invocation.command, invocation.args, {
+    const args = invocation.shell ? invocation.args.map(quoteShellArg) : invocation.args;
+    const child = spawn(invocation.command, args, {
       stdio: "inherit",
       env: { ...process.env, [SKIP_AUTO_UPDATE_ENV]: "1" },
+      shell: invocation.shell,
     });
     const cleanup = forwardSignals(child);