diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000..ed0e8c6
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,4 @@
+## 2025-02-09 - Avoid execSync for paths controlled by workspace inputs
+**Vulnerability:** Command injection vulnerability via `execSync` when executing dynamically generated workspace files. The `tempFile` was generated dynamically in `.shieldedshell/state/temp_check.js` which depended on `options.workspace`, allowing command injection.
+**Learning:** `execSync` runs in a shell by default or executes a string as a command, opening the possibility for command injection even for paths that look safe but are controlled by external inputs or environment locations.
+**Prevention:** Use `spawnSync` from `node:child_process` with an array-based argument list and `process.execPath` to launch node, removing the shell execution risk.
diff --git a/packages/core/src/reconcile.ts b/packages/core/src/reconcile.ts
index b0285bc..1c00261 100644
--- a/packages/core/src/reconcile.ts
+++ b/packages/core/src/reconcile.ts
@@ -1,4 +1,4 @@
-import { execSync } from "node:child_process";
+import { spawnSync } from "node:child_process";
 import crypto from "node:crypto";
 import fs from "node:fs";
 import path from "node:path";
@@ -138,20 +138,14 @@ export function reconcile(options: ReconcileOptions): ReconcileResult {
   fs.mkdirSync(path.dirname(tempFile), { recursive: true });
   fs.writeFileSync(tempFile, extractedCode, "utf8");
 
-  try {
-    execSync(`node --check "${tempFile}"`, { stdio: "pipe" });
-    log.audit("Syntax check passed");
-  } catch (err) {
-    const stderr =
-      err && typeof err === "object" && "stderr" in err
-        ? String((err as { stderr?: Buffer }).stderr ?? "")
-        : err instanceof Error
-          ? err.message
-          : String(err);
+  const check = spawnSync(process.execPath, ["--check", tempFile], { stdio: "pipe", encoding: "utf8" });
+  if (check.status !== 0) {
+    const stderr = check.stderr || (check.error ? check.error.message : "Unknown syntax error");
     consolidateSharedContext(sharedContext, `Syntax Error:\n${stderr}`);
     if (fs.existsSync(tempFile)) fs.unlinkSync(tempFile);
     return { success: false, reason: "Syntax check failed" };
   }
+  log.audit("Syntax check passed");
 
   if (options.benchmark) {
     const staticResult = runBenchmarkStaticVerification(options.workspace, options.benchmark);