fix(timeline): surface reasoning streams as thinking rows

apps/mobile/src/lib/threadActivity.test.ts

@@ -373,6 +373,49 @@ describe("buildThreadFeed", () => {
     expect(nextRows.some((row) => row.type === "activity-group")).toBe(true);
   });
 
+  it("keeps thinking activities in their own feed group between tool calls", () => {
+    const turnId = TurnId.make("turn-1");
+    const thread = makeThread({
+      id: ThreadId.make("feed-thinking"),
+      projectId: ProjectId.make("project-1"),
+      title: "Feed thinking",
+      messages: [],
+      activities: [
+        makeActivity({
+          id: EventId.make("tool-1"),
+          kind: "tool.completed",
+          summary: "Ran command",
+          tone: "tool",
+          createdAt: "2026-04-01T00:00:01.000Z",
+          turnId,
+          payload: { itemType: "command_execution", status: "completed" },
+        }),
+        makeActivity({
+          id: EventId.make("thinking-1"),
+          kind: "thinking",
+          summary: "Thinking",
+          tone: "info",
+          createdAt: "2026-04-01T00:00:02.000Z",
+          turnId,
+          payload: { detail: "Checking the checklist first." },
+        }),
+        makeActivity({
+          id: EventId.make("tool-2"),
+          kind: "tool.completed",
+          summary: "Ran command",
+          tone: "tool",
+          createdAt: "2026-04-01T00:00:03.000Z",
+          turnId,
+          payload: { itemType: "command_execution", status: "completed" },
+        }),
+      ],
+    });
+
+    const feed = buildThreadFeed(thread);
+    expect(feed.map((row) => row.id)).toEqual(["tool-1", "thinking-1", "tool-2"]);
+    expect(feed[1]).toMatchObject({ type: "activity-group" });
+  });
+
   it("regroups cached activities for message changes and pagination", () => {
     const messages = [2, 4].map((second) => ({
       id: MessageId.make(`message-${second}`),

apps/mobile/src/lib/threadActivity.ts

@@ -4,7 +4,11 @@ import {
   requestKindFromRequestType,
   type PendingApproval,
 } from "@t3tools/client-runtime/pending-requests";
-import { UserInputAttachmentAnswerPayload, isToolLifecycleItemType } from "@t3tools/contracts";
+import {
+  THINKING_ACTIVITY_KIND,
+  UserInputAttachmentAnswerPayload,
+  isToolLifecycleItemType,
+} from "@t3tools/contracts";
 import type {
   OrchestrationLatestTurn,
   OrchestrationThread,
@@ -1555,12 +1559,16 @@ function groupAdjacentActivities(entries: ReadonlyArray<RawThreadFeedEntry>): Th
     }
 
     const isCompaction = entry.activity.workEntry.sourceActivityKind === "context-compaction";
-    if (isCompaction || firstActivityEntry?.turnId !== entry.turnId) {
+    // Thinking rows stay visible outside collapsed tool groups (mirrors web):
+    // they break the run on both sides so a reasoning-narrated turn keeps its
+    // narrative without expanding dozens of tool calls.
+    const isThinking = entry.activity.workEntry.sourceActivityKind === THINKING_ACTIVITY_KIND;
+    if (isCompaction || isThinking || firstActivityEntry?.turnId !== entry.turnId) {
       flushGroup();
     }
     firstActivityEntry ??= entry;
     openGroupActivities.push(entry.activity);
-    if (isCompaction) {
+    if (isCompaction || isThinking) {
       flushGroup();
     }
   }