diff --git a/crates/ui/e2e/pages/api.ts b/crates/ui/e2e/pages/api.ts
index 6f83e1dc2..916b3431c 100644
--- a/crates/ui/e2e/pages/api.ts
+++ b/crates/ui/e2e/pages/api.ts
@@ -45,6 +45,46 @@ export async function readResource(
   return res.json();
 }
 
+/**
+ * Wait until a just-created resource is visible to FHIR search.
+ *
+ * On composite backends (sqlite/s3 + Elasticsearch) create returns as soon as
+ * the write store acknowledges; the search index can lag a few hundred ms.
+ * Nightly ui-tests-matrix flakes when the next step searches immediately.
+ */
+export async function waitForSearchHit(
+  request: APIRequestContext,
+  type: string,
+  query: string,
+  opts: { timeoutMs?: number } = {},
+): Promise<void> {
+  const timeoutMs = opts.timeoutMs ?? 15_000;
+  const deadline = Date.now() + timeoutMs;
+  let lastStatus = 0;
+  let lastTotal = "n/a";
+  while (Date.now() < deadline) {
+    const res = await request.get(`/${type}?${query}`, {
+      headers: { Accept: FHIR_JSON },
+    });
+    lastStatus = res.status();
+    if (res.ok()) {
+      const bundle = await res.json();
+      const total =
+        typeof bundle.total === "number"
+          ? bundle.total
+          : Array.isArray(bundle.entry)
+            ? bundle.entry.length
+            : 0;
+      lastTotal = String(total);
+      if (total > 0) return;
+    }
+    await new Promise((r) => setTimeout(r, 200));
+  }
+  throw new Error(
+    `timed out waiting for ${type}?${query} (last status=${lastStatus}, total=${lastTotal})`,
+  );
+}
+
 /**
  * Create a resource and immediately update it, leaving two versions — the
  * minimum a history diff needs. Returns the id. `mutate` produces the second
diff --git a/crates/ui/e2e/tests/queries.spec.ts b/crates/ui/e2e/tests/queries.spec.ts
index 0ca55b34a..ccd4b7111 100644
--- a/crates/ui/e2e/tests/queries.spec.ts
+++ b/crates/ui/e2e/tests/queries.spec.ts
@@ -1,5 +1,5 @@
 import { test, expect } from "../pages/fixtures";
-import { createResource } from "../pages/api";
+import { createResource, waitForSearchHit } from "../pages/api";
 
 // The Saved Queries workspace (/ui/queries): the shared query builder and the
 // in-page results table — run a query, add builder rows, page through results,
@@ -68,12 +68,19 @@ test.describe("query builder", () => {
       subject: { reference: `Patient/${patient}` },
     });
 
+    // ES composite backends need the Observation (+ Practitioner name) indexed
+    // before chained/_has search can see them.
+    await waitForSearchHit(request, "Observation", `code=chain-94-${tag}`);
+    await waitForSearchHit(request, "Practitioner", `name=ChainSmith${tag}`);
+
     await queries.goto();
     await queries.builder.run(
       `Patient?_has:Observation:patient:code=chain-94-${tag}&general-practitioner.name=ChainSmith${tag}`,
     );
     await queries.results.waitShown();
-    await expect(queries.results.rows).toHaveCount(1);
+    await expect
+      .poll(async () => queries.results.rows.count(), { timeout: 15_000 })
+      .toBe(1);
     await expect(queries.results.rows.first()).toContainText(patient);
   });
 
diff --git a/crates/ui/e2e/tests/search-parameters.spec.ts b/crates/ui/e2e/tests/search-parameters.spec.ts
index 41be51a4a..fa07e85bc 100644
--- a/crates/ui/e2e/tests/search-parameters.spec.ts
+++ b/crates/ui/e2e/tests/search-parameters.spec.ts
@@ -1,5 +1,5 @@
 import { test, expect } from "../pages/fixtures";
-import { createResource } from "../pages/api";
+import { createResource, waitForSearchHit } from "../pages/api";
 
 // The SearchParameter registry viewer (/ui/search-parameters): the htmx filter
 // rail, the type/source facet chips, row selection into the detail panel, and
@@ -48,26 +48,32 @@ test("a stored parameter can be created, offers Edit, and deletes", async ({
 }) => {
   const stamp = Date.now();
   const url = `http://example.org/e2e/SearchParameter/crud-${stamp}`;
+  const code = `e2e-crud-${stamp}`;
   const id = await createResource(request, "SearchParameter", {
     url,
     name: "e2eCrud",
-    code: `e2e-crud-${stamp}`,
+    code,
     status: "active",
     type: "token",
     base: ["Patient"],
     expression: "Patient.identifier",
   });
 
+  // Composite ES backends index asynchronously; wait before UI refresh.
+  await waitForSearchHit(request, "SearchParameter", `url=${encodeURIComponent(url)}`);
+
   // refresh=1 drops the server's cached snapshot so the new parameter shows.
   await searchParameters.goto(`?refresh=1&sel=${encodeURIComponent(url)}`);
   await expect(page.locator(".page-head__actions a.btn--primary")).toHaveAttribute(
     "href",
     "/ui/editor?type=SearchParameter",
   );
-  await expect(page.locator(".detail__actions a.btn")).toHaveAttribute(
-    "href",
-    `/ui/editor?type=SearchParameter&id=${id}`,
-  );
+  // Detail actions can land a beat after the registry swap on slow backends.
+  await expect
+    .poll(async () => page.locator(".detail__actions a.btn").getAttribute("href"), {
+      timeout: 15_000,
+    })
+    .toBe(`/ui/editor?type=SearchParameter&id=${id}`);
 
   page.once("dialog", (d) => d.accept());
   await page.locator(".detail__actions [data-crud-delete]").click();