fix: align workspace diagnostic contracts

backend/test/workspaces-schema.test.ts

@@ -98,6 +98,7 @@ test("requires explicit vector database and schema identities with strict diagno
       + "      method: POST\n"
       + "      path: /rpc/diagnostic_vector_probe\n"
       + "      auth: bearer\n"
+      + "      response: { operation: operation }\n"
       + "  embedding:\n"
       + "    method: GET\n"
       + "    path: /models\n"
@@ -134,6 +135,24 @@ test("requires explicit vector database and schema identities with strict diagno
     .toThrow(/response field/i);
 });
 
+test("requires a reversible writer probe to declare the response operation it verifies", () => {
+  const writerProbe = validYaml.replace("llm_policy:\n", `diagnostics:
+  vector_rest:
+    metadata:
+      method: GET
+      path: /metadata
+      auth: bearer
+      response: { collection: collection, dimensions: dimensions, distance: distance }
+    reversible_probe:
+      method: POST
+      path: /diagnostic-probe
+      auth: bearer
+llm_policy:
+`);
+
+  expect(() => parseWorkspaceYaml(writerProbe)).toThrow(/response|operation/i);
+});
+
 test("keeps v1 descriptors readable but requires explicit migration before v2 operations", () => {
   const v1WithoutVectorIdentity = validYaml.replace("schema_version: 2", "schema_version: 1").replace(
     "    database: postgres\n    schema: vectors\n", "",