diff --git a/apps/fabro-web/app/lib/ask-fabro-runtime.test.ts b/apps/fabro-web/app/lib/ask-fabro-runtime.test.ts
index 9b4f07788..fdb360045 100644
--- a/apps/fabro-web/app/lib/ask-fabro-runtime.test.ts
+++ b/apps/fabro-web/app/lib/ask-fabro-runtime.test.ts
@@ -13,7 +13,38 @@ function event(name: string, properties: Record<string, unknown>): SessionStream
   } as unknown as SessionStreamEvent;
 }
 
+function flattenedEvent(
+  name: string,
+  properties: Record<string, unknown>,
+): SessionStreamEvent {
+  return {
+    seq: 0,
+    id: "evt_1",
+    ts: "2026-05-22T16:25:34.940200Z",
+    run_id: "run_1",
+    event: name,
+    properties,
+  } as unknown as SessionStreamEvent;
+}
+
 describe("applyTurnEvent", () => {
+  test("appends assistant deltas from flattened SSE event envelopes", () => {
+    const acc = {
+      activeTextIndex: null,
+      parts: [],
+      toolCallIndex: new Map(),
+    } as Parameters<typeof applyTurnEvent>[0];
+
+    expect(
+      applyTurnEvent(
+        acc,
+        flattenedEvent("run.session.assistant_delta", { delta: "Hello" }),
+      ),
+    ).toBe(true);
+
+    expect(acc.parts).toEqual([{ type: "text", text: "Hello" }]);
+  });
+
   test("appends assistant deltas into a single streaming text part", () => {
     const acc = {
       activeTextIndex: null,
diff --git a/apps/fabro-web/app/lib/ask-fabro-runtime.ts b/apps/fabro-web/app/lib/ask-fabro-runtime.ts
index dce3d5795..17623ea79 100644
--- a/apps/fabro-web/app/lib/ask-fabro-runtime.ts
+++ b/apps/fabro-web/app/lib/ask-fabro-runtime.ts
@@ -100,17 +100,34 @@ interface NestedRunEvent {
   properties?: Record<string, unknown>;
 }
 
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null && !Array.isArray(value);
+}
+
+function eventPayload(envelope: SessionStreamEvent): {
+  eventName: string;
+  props: Record<string, unknown>;
+} {
+  const raw = envelope as unknown as Record<string, unknown>;
+  if (typeof raw.event === "string") {
+    return {
+      eventName: raw.event,
+      props: isRecord(raw.properties) ? raw.properties : {},
+    };
+  }
+
+  const nested = isRecord(raw.event) ? (raw.event as NestedRunEvent) : {};
+  return {
+    eventName: nested.event ?? "",
+    props: isRecord(nested.properties) ? nested.properties : {},
+  };
+}
+
 export function applyTurnEvent(
   acc: TurnAccumulator,
   envelope: SessionStreamEvent,
 ): boolean {
-  // The on-wire SSE envelope is `{ seq, event: { event: "...", properties } }`,
-  // but the generated OpenAPI `EventEnvelope` type flattens the inner event
-  // fields. Cast through `unknown` to read the nested runtime shape that the
-  // server actually emits (matches `session-stream.test.ts`).
-  const nested = (envelope as unknown as { event?: NestedRunEvent }).event ?? {};
-  const eventName = nested.event ?? "";
-  const props: Record<string, unknown> = nested.properties ?? {};
+  const { eventName, props } = eventPayload(envelope);
 
   if (eventName === "run.session.assistant_delta") {
     const delta = typeof props.delta === "string" ? props.delta : "";
diff --git a/apps/fabro-web/app/lib/session-stream.test.ts b/apps/fabro-web/app/lib/session-stream.test.ts
index 15b88a8db..168da8d3a 100644
--- a/apps/fabro-web/app/lib/session-stream.test.ts
+++ b/apps/fabro-web/app/lib/session-stream.test.ts
@@ -41,7 +41,7 @@ describe("session stream helpers", () => {
         streamResponse(
           [
             "id: 3\nevent: run.session.turn.started\n",
-            'data: {"seq":3,"event":{"event":"run.session.turn.started","properties":{"turn_id":"turn_1"}}}\n\n',
+            'data: {"seq":3,"id":"evt_1","ts":"2026-05-22T16:25:34.940200Z","run_id":"run_1","event":"run.session.turn.started","properties":{"turn_id":"turn_1"}}\n\n',
           ],
           200,
           { "x-fabro-turn-id": "turn_1" },
@@ -65,7 +65,7 @@ describe("session stream helpers", () => {
     });
     expect(events).toHaveLength(1);
     expect(events[0]?.seq).toBe(3);
-    expect(events[0]?.event.event).toBe("run.session.turn.started");
+    expect(events[0]?.event).toBe("run.session.turn.started");
   });
 
   test("attaches to session events from a run sequence", async () => {
@@ -73,7 +73,7 @@ describe("session stream helpers", () => {
     const fetchMock = mock(() =>
       Promise.resolve(
         streamResponse([
-          'data: {"seq":7,"event":{"event":"run.session.assistant_message","properties":{}}}\n\n',
+          'data: {"seq":7,"id":"evt_2","ts":"2026-05-22T16:25:34.940200Z","run_id":"run_1","event":"run.session.assistant_message","properties":{}}\n\n',
         ]),
       ),
     );
@@ -96,7 +96,7 @@ describe("session stream helpers", () => {
     const fetchMock = mock(() =>
       Promise.resolve(
         streamResponse([
-          'data: {"seq":8,"event":{"event":"run.session.assistant_message","properties":{}}}\r\n\r\n',
+          'data: {"seq":8,"id":"evt_3","ts":"2026-05-22T16:25:34.940200Z","run_id":"run_1","event":"run.session.assistant_message","properties":{}}\r\n\r\n',
         ]),
       ),
     );