diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000..ba2daab
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,7 @@
+## 2025-05-18 - Fix Command Injection in Reconciler
+
+**Vulnerability:** Found a command injection vulnerability in `packages/core/src/reconcile.ts` where `execSync` was used to execute a shell command constructed with a file path directly from the workspace. This means if a path contains shell metacharacters (e.g. `$`, \`, quotes), it could allow arbitrary command execution during the reconcile syntax check step.
+
+**Learning:** When executing a process using Node.js, relying on shell execution functions like `execSync` with strings that contain dynamic or user-controlled input can lead to command injection.
+
+**Prevention:** Use array-based argument passing functions like `spawnSync` along with `process.execPath` (to prevent executing arbitrary executables in `$PATH`) instead of string-based execution functions like `execSync`.
diff --git a/packages/core/src/reconcile.ts b/packages/core/src/reconcile.ts
index b0285bc..65c0a8f 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 +139,8 @@ export function reconcile(options: ReconcileOptions): ReconcileResult {
   fs.writeFileSync(tempFile, extractedCode, "utf8");
 
   try {
-    execSync(`node --check "${tempFile}"`, { stdio: "pipe" });
+    const checkResult = spawnSync(process.execPath, ["--check", tempFile], { stdio: "pipe" });
+    if (checkResult.error || checkResult.status !== 0) { throw checkResult.error || new Error((checkResult.stderr || "").toString()); }
     log.audit("Syntax check passed");
   } catch (err) {
     const stderr =