diff --git a/src/lib/services/box/box-inbound-service.ts b/src/lib/services/box/box-inbound-service.ts
index 37caff7..78a77e5 100644
--- a/src/lib/services/box/box-inbound-service.ts
+++ b/src/lib/services/box/box-inbound-service.ts
@@ -6,10 +6,42 @@ import { ingestInboundFile, type IngestResult } from "@/lib/services/inbound-ing
  * the file's name from Box (so the matcher has something to parse) and
  * delegates everything else — regex resolution, project/deliverable
  * matching, holding-pen vs active branching, notifications.
+ *
+ * Loop guard: only accepts events whose file's parent folder matches
+ * BOX_WATCH_FOLDER_ID. Box webhooks are already folder-scoped on
+ * subscription, but a misconfigured subscription on the outbound folder
+ * would otherwise ingest our own uploads. Defence in depth.
  */
 export async function ingestBoxUpload(fileId: string): Promise<IngestResult> {
   try {
     const meta = await getBoxFileMetadata(fileId);
+
+    const watchFolderId = process.env.BOX_WATCH_FOLDER_ID;
+    const outFolderId = process.env.BOX_OUT_FOLDER_ID;
+    const parentId = meta.parent?.id;
+
+    // Reject anything from the outbound folder — that's our own writes.
+    if (outFolderId && parentId === outFolderId) {
+      return {
+        ok: true,
+        status: "UNMATCHED",
+        error: `Ignoring event from outbound folder ${outFolderId} (loop guard).`,
+      };
+    }
+
+    // When the watch folder is configured, require the file to be a direct
+    // child of it. (We don't walk up the parent chain — files dropped
+    // into nested sub-folders won't fire matching webhooks anyway because
+    // Box only fires on the subscribed folder's direct contents unless
+    // the subscription includes descendants.)
+    if (watchFolderId && parentId !== watchFolderId) {
+      return {
+        ok: true,
+        status: "UNMATCHED",
+        error: `File parent ${parentId} is not the watch folder ${watchFolderId}.`,
+      };
+    }
+
     return ingestInboundFile({
       source: "BOX",
       fileName: meta.name,