diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000..119d9f4
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,4 @@
+## 2024-05-24 - [Command Injection] Replace execSync with spawnSync
+**Vulnerability:** Found `execSync` being used with string concatenation in `reconcile.ts` and `loop.test.ts`. This poses a command injection risk, especially if variables like `tempFile` contain spaces or malicious shell characters.
+**Learning:** Avoid using shell execution functions like `execSync` with dynamically constructed strings. Even with careful escaping, it's error-prone.
+**Prevention:** Always use `spawnSync` (or `spawn`) with an array of arguments, which bypasses the shell and prevents command injection. Also prefer using `process.execPath` instead of relying on `"node"` being in the `PATH`.
diff --git a/packages/core/src/loop.test.ts b/packages/core/src/loop.test.ts
index f9d430f..379f772 100644
--- a/packages/core/src/loop.test.ts
+++ b/packages/core/src/loop.test.ts
@@ -1,4 +1,4 @@
-import { execSync } from "node:child_process";
+import { spawnSync } from "node:child_process";
 import fs from "node:fs";
 import os from "node:os";
 import path from "node:path";
@@ -173,12 +173,12 @@ describe("ledger benchmark e2e", () => {
   it("reconcile passes validator for correct ledger implementation", () => {
     const dir = setupWorkspace();
     const mergeTarget = path.join(dir, "auth_service.js");
-    execSync(`node "${fixturePath("mock-dev-ledger.mjs")}" "${path.join(dir, "developer_output.json")}"`, {
-      stdio: "pipe",
-    });
-    execSync(`node "${fixturePath("mock-audit-pass.mjs")}" "${path.join(dir, "auditor_output.json")}"`, {
-      stdio: "pipe",
-    });
+
+    let res = spawnSync(process.execPath, [fixturePath("mock-dev-ledger.mjs"), path.join(dir, "developer_output.json")], { stdio: "pipe" });
+    if (res.status !== 0) throw new Error("Mock dev ledger failed");
+
+    res = spawnSync(process.execPath, [fixturePath("mock-audit-pass.mjs"), path.join(dir, "auditor_output.json")], { stdio: "pipe" });
+    if (res.status !== 0) throw new Error("Mock audit pass failed");
 
     const result = reconcile({
       workspace: dir,
diff --git a/packages/core/src/reconcile.ts b/packages/core/src/reconcile.ts
index b0285bc..2a95f89 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";
@@ -139,7 +139,13 @@ export function reconcile(options: ReconcileOptions): ReconcileResult {
   fs.writeFileSync(tempFile, extractedCode, "utf8");
 
   try {
-    execSync(`node --check "${tempFile}"`, { stdio: "pipe" });
+    const result = spawnSync(process.execPath, ["--check", tempFile], { stdio: "pipe" });
+    if (result.error) throw result.error;
+    if (result.status !== 0) {
+      const err = new Error("Command failed");
+      (err as any).stderr = result.stderr;
+      throw err;
+    }
     log.audit("Syntax check passed");
   } catch (err) {
     const stderr =