fix: restore model activity reasoning stream

backend/src/bridge/session-bridge.ts

@@ -3,6 +3,7 @@ import type { RpcClient } from "../rpc/rpc-client.js";
 export type ClientEvent =
   | { type: "ui_request"; ui_request: any }
   | { type: "text_delta"; text: string }
+  | { type: "activity_delta"; text: string }
   | { type: "info"; [k: string]: any }
   | { type: "system_event"; [k: string]: any };
 
@@ -27,6 +28,8 @@ export class SessionBridge {
         this.fan({ type: "info", level: m.notifyType ?? "info", text: m.message ?? "" });
       } else if (m.type === "message_update" && m.assistantMessageEvent?.type === "text_delta") {
         this.fan({ type: "text_delta", text: m.assistantMessageEvent.delta ?? "" });
+      } else if (m.type === "message_update" && m.assistantMessageEvent?.type === "thinking_delta") {
+        this.fan({ type: "activity_delta", text: m.assistantMessageEvent.delta ?? "" });
       } else if (m.type === "text_delta") {
         this.fan({ type: "text_delta", text: m.text ?? "" });
       // tool_execution_* events are intentionally NOT forwarded: they clutter

backend/src/routes/sessions.ts

@@ -69,8 +69,7 @@ export function sessionRoutes(
     const options = {
       provider: s.provider,
       model: s.model,
-      // Keep the saved preference in the manifest; F1 starts tool-first.
-      thinking: "off",
+      thinking: s.thinking,
       author: getUser(req).id,
       question: b.question,
     };
@@ -117,9 +116,7 @@ export function sessionRoutes(
     const options = {
       provider: saved?.provider,
       model: saved?.model,
-      // Phase 1 must reach a widget instead of exposing a long reasoning trace.
-      // The session keeps its saved preference for later turns.
-      thinking: "off",
+      thinking: saved?.thinking ?? settings.thinking,
       author: getUser(req).id,
       mode: "resume" as const,
     };