diff --git a/lib/stream-isolation.js b/lib/stream-isolation.js
new file mode 100644
index 0000000..1b26eda
--- /dev/null
+++ b/lib/stream-isolation.js
@@ -0,0 +1,14 @@
+// This file ensures per-session isolation for SSE streams
+export function createSessionStream(sessionId) {
+  // Fix: Concurrent sessions were sharing event buffers
+  // We now create a unique buffer array per session ID
+  const sessionBuffer = [];
+  return {
+    push: (data) => sessionBuffer.push(data),
+    flush: () => {
+      const data = [...sessionBuffer];
+      sessionBuffer.length = 0;
+      return data;
+    }
+  };
+}
diff --git a/lib/stream-isolation.test.js b/lib/stream-isolation.test.js
new file mode 100644
index 0000000..a2cd2c1
--- /dev/null
+++ b/lib/stream-isolation.test.js
@@ -0,0 +1,4 @@
+// Manual test cases
+// 1. Open two browsers
+// 2. Trigger code generation simultaneously
+// 3. Verify no leakage