harden state durability and disable destructive snapshot sync

test/server.test.js

@@ -11,6 +11,7 @@ const {
 
 function createRuntimeConfig() {
   return {
+    nodeEnv: "test",
     port: 3000,
     logLevel: "info",
     appBaseUrl: "http://localhost:3000",
@@ -60,6 +61,7 @@ function createRuntimeConfig() {
       stepCredits: 1,
       maxCharsPerArticle: 120000,
     },
+    allowInMemoryStateFallback: true,
   };
 }
 
@@ -153,3 +155,39 @@ test("createRuntime falls back to in-memory state when initial load fails", asyn
   assert.equal(response.status, 303);
   await runtime.persister.flush();
 });
+
+test("createRuntime fails startup when fallback is disabled", async () => {
+  const runtimeConfig = createRuntimeConfig();
+  runtimeConfig.allowInMemoryStateFallback = false;
+
+  await assert.rejects(
+    createRuntime({
+      runtimeConfig,
+      logger: { info() {}, warn() {}, error() {} },
+      stateStore: {
+        async load() {
+          throw new Error("state_load_failed");
+        },
+        async save() {},
+      },
+    }),
+    /state_store_unavailable_without_fallback/,
+  );
+});
+
+test("createMutationPersister surfaces save errors", async () => {
+  const persister = createMutationPersister({
+    stateStore: {
+      async save() {
+        throw new Error("persist_failed");
+      },
+    },
+    logger: { error() {} },
+  });
+
+  await assert.rejects(
+    persister.enqueue({}),
+    /persist_failed/,
+  );
+  assert.equal(persister.getLastError()?.message, "persist_failed");
+});