diff --git a/scripts/patch-ap-accounts-id-cache-fallback.mjs b/scripts/patch-ap-accounts-id-cache-fallback.mjs
new file mode 100644
index 00000000..4aa263e0
--- /dev/null
+++ b/scripts/patch-ap-accounts-id-cache-fallback.mjs
@@ -0,0 +1,62 @@
+/**
+ * patch-ap-accounts-id-cache-fallback.mjs
+ *
+ * Fixes 404 on /api/v1/accounts/:id for actors resolved via /lookup but not
+ * in followers/following/timeline. After resolveActorData() returns null,
+ * checks in-memory idToUrl cache and ap_actor_cache MongoDB collection for
+ * the actor URL, then calls resolveRemoteAccount() if found.
+ */
+import { readFileSync, writeFileSync } from "node:fs";
+
+const MARKER = "// [patch] ap-accounts-id-cache-fallback";
+const TARGET = "/usr/local/indiekit/node_modules/@rmdes/indiekit-endpoint-activitypub/lib/mastodon/routes/accounts.js";
+
+const src = readFileSync(TARGET, "utf8");
+
+if (src.includes(MARKER)) {
+  console.log("[postinstall] ap-accounts-id-cache-fallback: already applied");
+  process.exit(0);
+}
+
+// Find the 404 return in the GET /accounts/:id handler.
+// We need to insert a cache-fallback block BEFORE the 404 return.
+// The pattern: after the resolveActorData block, before `return res.status(404)`
+// in the :id handler.
+
+const needle = `    return res.status(404).json({ error: "Record not found" });
+  } catch (error) {
+    next(error);
+  }
+});
+
+// ─── GET /api/v1/accounts/:id/statuses`;
+
+if (!src.includes(needle)) {
+  console.error("[postinstall] ap-accounts-id-cache-fallback: cannot find insertion point");
+  process.exit(1);
+}
+
+const replacement = `    // Cache fallback: actor not in followers/following/timeline, ${MARKER}
+    // but may have been resolved via /lookup and cached in ap_actor_cache
+    let cachedActorUrl = getActorUrlFromId(id); ${MARKER}
+    if (!cachedActorUrl && collections.ap_actor_cache) { ${MARKER}
+      const cached = await collections.ap_actor_cache.findOne({ _id: id }); ${MARKER}
+      if (cached?.actorUrl) cachedActorUrl = cached.actorUrl; ${MARKER}
+    } ${MARKER}
+    if (cachedActorUrl) { ${MARKER}
+      const cachedAccount = await resolveRemoteAccount( ${MARKER}
+        cachedActorUrl, pluginOptions, baseUrl, collections, ${MARKER}
+      ); ${MARKER}
+      if (cachedAccount) return res.json(cachedAccount); ${MARKER}
+    } ${MARKER}
+
+    return res.status(404).json({ error: "Record not found" });
+  } catch (error) {
+    next(error);
+  }
+});
+
+// ─── GET /api/v1/accounts/:id/statuses`;
+
+writeFileSync(TARGET, src.replace(needle, replacement));
+console.log("[postinstall] ap-accounts-id-cache-fallback: applied successfully");