diff --git a/.changeset/fn-8780-activity-thinking-open.md b/.changeset/fn-8780-activity-thinking-open.md
new file mode 100644
index 0000000000..23e42e38ae
--- /dev/null
+++ b/.changeset/fn-8780-activity-thinking-open.md
@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: Expand Task Detail Activity thinking blocks by default.
+category: fix
+dev: Preserves per-block collapse state while streamed reasoning updates arrive.
diff --git a/packages/dashboard/app/components/TaskChatTab.tsx b/packages/dashboard/app/components/TaskChatTab.tsx
index 73c28e3605..701c6f5103 100644
--- a/packages/dashboard/app/components/TaskChatTab.tsx
+++ b/packages/dashboard/app/components/TaskChatTab.tsx
@@ -1,5 +1,5 @@
 import type { AgentLogEntry, AgentRole, SteeringComment, Task, TaskDetail } from "@fusion/core";
-import { isCompleteColumnRole, isReviewColumnRole, isWipColumnRole } from "../utils/columnRoles";
+import { isCompleteColumnRole, isWipColumnRole } from "../utils/columnRoles";
 import React, { useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState } from "react";
 import ReactMarkdown from "react-markdown";
 import remarkGfm from "remark-gfm";
@@ -586,13 +586,10 @@ function TaskChatToolGroup({ entries }: { entries: AgentLogEntry[] }) {
 }
 
 /*
- FNXC:Chat-Thinking 2026-07-15-10:33:
- Chat thinking (reasoning) blocks render collapsed by default so the response is scannable without manually closing each block; the summary remains an expand-on-click affordance. (FN-7974)
-
- FNXC:Chat-Thinking 2026-07-16-18:05:
- FN-8171 keeps the scannable collapsed default for idle task columns, but opens Live Activity thinking for in-progress and in-review tasks so operators can follow active or awaiting-review reasoning at a glance. The expanded block remains user-collapsible.
+FNXC:Chat-Thinking 2026-08-04-08:15:
+FN-8780 requires every newly mounted Task Detail Activity thinking segment to start expanded, regardless of workflow column, so operators can read reasoning immediately. State remains controlled after mount: the summary still lets operators collapse or reopen a segment, and stable segment identity preserves that choice during streaming.
 */
-function TaskChatThinking({ entries, defaultOpen = false }: { entries: AgentLogEntry[]; defaultOpen?: boolean }) {
+function TaskChatThinking({ entries, defaultOpen = true }: { entries: AgentLogEntry[]; defaultOpen?: boolean }) {
   const { t } = useTranslation("app");
   const [open, setOpen] = useState(defaultOpen);
   const combinedThinkingText = entries.map((entry) => entry.text).join("");
@@ -622,12 +619,12 @@ function TaskChatThinking({ entries, defaultOpen = false }: { entries: AgentLogE
   );
 }
 
-function TaskChatSegmentView({ segment, defaultOpen }: { segment: TaskChatSegment; defaultOpen?: boolean }) {
+function TaskChatSegmentView({ segment }: { segment: TaskChatSegment }) {
   if (segment.kind === "tool") {
     return <TaskChatToolGroup entries={segment.entries} />;
   }
   if (segment.kind === "thinking") {
-    return <TaskChatThinking entries={segment.entries} defaultOpen={defaultOpen} />;
+    return <TaskChatThinking entries={segment.entries} />;
   }
   return <TaskChatText entries={segment.entries} />;
 }
@@ -672,14 +669,6 @@ export function TaskChatTab({ task, columnFlags, projectId, active, addToast, on
   const [optimisticMessages, setOptimisticMessages] = useState<UserChatMessage[]>([]);
   const [isTranscriptAtBottom, setIsTranscriptAtBottom] = useState(true);
   const isTranscriptAtBottomRef = useRef(true);
-  /*
-  FNXC:WorkflowResolvedColumns 2026-07-30-02:10 (batch-dashboard-app):
-  WIP and REVIEW roles, resolved. This decides whether the thinking transcript is expanded by
-  default — open while work is live, collapsed once it is not. Keyed on the literals, a renamed
-  board collapsed it for every card, so an operator watching an active run had to expand it by hand
-  on every task, every time.
-  */
-  const thinkingDefaultOpen = isWipColumnRole(columnFlags, task.column) || isReviewColumnRole(columnFlags, task.column);
   const transcriptRef = useRef<HTMLDivElement>(null);
   const previousEntryCountRef = useRef(0);
   const previousScrollHeightRef = useRef(0);
@@ -1103,7 +1092,7 @@ export function TaskChatTab({ task, columnFlags, projectId, active, addToast, on
                     A genuinely new segment always has a different startIndex, so identity stays correct without the volatile suffix.
                     */
                     const segmentKey = `${segment.kind}-${segment.startIndex}`;
-                    return <TaskChatSegmentView key={segmentKey} segment={segment} defaultOpen={thinkingDefaultOpen} />;
+                    return <TaskChatSegmentView key={segmentKey} segment={segment} />;
                   })}
                 </div>
               </section>
diff --git a/packages/dashboard/app/components/__tests__/TaskChatTab.test.tsx b/packages/dashboard/app/components/__tests__/TaskChatTab.test.tsx
index 8037469f94..062cf7e563 100644
--- a/packages/dashboard/app/components/__tests__/TaskChatTab.test.tsx
+++ b/packages/dashboard/app/components/__tests__/TaskChatTab.test.tsx
@@ -1149,7 +1149,26 @@ describe("TaskChatTab", () => {
     expect(within(standaloneEntry).getByLabelText("Tool entry timestamp")).toHaveTextContent(expectedTime);
   });
 
-  it("renders thinking in a collapsed-by-default expandable block for inactive tasks", async () => {
+  it.each([
+    ["WIP", "in-progress"],
+    ["review", "in-review"],
+    ["idle", "todo"],
+    ["planning", "triage"],
+    ["terminal", "done"],
+    ["archived", "archived"],
+  ] as const)("defaults thinking blocks open for %s tasks", (_state, column) => {
+    mockLogs([
+      makeEntry({ agent: "executor", type: "thinking", text: "Immediately readable reasoning" }),
+    ]);
+
+    render(<TaskChatTab task={makeTask({ column })} active addToast={vi.fn()} />);
+
+    const thinking = screen.getByTestId("task-chat-thinking");
+    expect(thinking).toHaveAttribute("open");
+    expect(screen.getByText("Immediately readable reasoning")).toBeVisible();
+  });
+
+  it("lets users collapse and reopen initially expanded thinking blocks", async () => {
     const user = userEvent.setup();
     mockLogs([
       makeEntry({ agent: "triage", type: "thinking", text: "I am considering options" }),
@@ -1158,57 +1177,20 @@ describe("TaskChatTab", () => {
     render(<TaskChatTab task={makeTask({ column: "done" })} active addToast={vi.fn()} />);
 
     const thinking = screen.getByTestId("task-chat-thinking");
-    expect(thinking).not.toHaveAttribute("open");
+    expect(thinking).toHaveAttribute("open");
     expect(within(thinking).getByText("Thinking")).toBeVisible();
-    expect(screen.getByText("I am considering options")).not.toBeVisible();
+    expect(screen.getByText("I am considering options")).toBeVisible();
     expect(within(thinking).getAllByTestId("task-chat-entry-thinking")).toHaveLength(1);
 
     await user.click(within(thinking).getByText("Thinking"));
 
+    expect(thinking).not.toHaveAttribute("open");
+    expect(screen.getByText("I am considering options")).not.toBeVisible();
+
+    await user.click(within(thinking).getByText("Thinking"));
+
     expect(thinking).toHaveAttribute("open");
     expect(screen.getByText("I am considering options")).toBeVisible();
-
-    await user.click(within(thinking).getByText("Thinking"));
-
-    expect(thinking).not.toHaveAttribute("open");
-    expect(screen.getByText("I am considering options")).not.toBeVisible();
-  });
-
-  it.each(["in-progress", "in-review"] as const)("defaults thinking blocks open for %s tasks", (column) => {
-    mockLogs([
-      makeEntry({ agent: "executor", type: "thinking", text: "Live reasoning" }),
-    ]);
-
-    render(<TaskChatTab task={makeTask({ column })} active addToast={vi.fn()} />);
-
-    expect(screen.getByTestId("task-chat-thinking")).toHaveAttribute("open");
-  });
-
-  it.each(["todo", "done", "triage", "archived"] as const)("keeps thinking blocks collapsed for %s tasks", (column) => {
-    mockLogs([
-      makeEntry({ agent: "executor", type: "thinking", text: "Historical reasoning" }),
-    ]);
-
-    render(<TaskChatTab task={makeTask({ column })} active addToast={vi.fn()} />);
-
-    expect(screen.getByTestId("task-chat-thinking")).not.toHaveAttribute("open");
-  });
-
-  it("lets users collapse auto-expanded thinking blocks", async () => {
-    const user = userEvent.setup();
-    mockLogs([
-      makeEntry({ agent: "executor", type: "thinking", text: "Active reasoning" }),
-    ]);
-
-    render(<TaskChatTab task={makeTask({ column: "in-progress" })} active addToast={vi.fn()} />);
-
-    const thinking = screen.getByTestId("task-chat-thinking");
-    expect(thinking).toHaveAttribute("open");
-
-    await user.click(within(thinking).getByText("Thinking"));
-
-    expect(thinking).not.toHaveAttribute("open");
-    expect(screen.getByText("Active reasoning")).not.toBeVisible();
   });
 
   it("renders consecutive thinking entries as one continuous section", () => {
@@ -1220,6 +1202,7 @@ describe("TaskChatTab", () => {
     render(<TaskChatTab task={makeTask()} active addToast={vi.fn()} />);
 
     const thinking = screen.getByTestId("task-chat-thinking");
+    expect(thinking).toHaveAttribute("open");
     const summary = thinking.querySelector("summary");
     expect(summary).toBeTruthy();
     expect(within(summary as HTMLElement).getByText("Thinking")).toBeVisible();
@@ -1234,7 +1217,7 @@ describe("TaskChatTab", () => {
   FNXC:TaskChatSegmentKey 2026-07-22-12:00:
   Segment keys must be kind + startIndex only. Embedding entries.length remounted the actively streaming segment on every appended entry, collapsing an expanded thinking block mid-stream.
   */
-  it("keeps an expanded thinking block expanded while entries stream into the same segment", async () => {
+  it("keeps a user-collapsed thinking block collapsed while entries stream into the same segment", async () => {
     const user = userEvent.setup();
     mockLogs([
       makeEntry({ agent: "executor", type: "thinking", text: "First streamed thought" }),
@@ -1243,9 +1226,9 @@ describe("TaskChatTab", () => {
     const { rerender } = render(<TaskChatTab task={makeTask({ column: "todo" })} active addToast={vi.fn()} />);
 
     const thinking = screen.getByTestId("task-chat-thinking");
-    expect(thinking).not.toHaveAttribute("open");
-    await user.click(within(thinking).getByText("Thinking"));
     expect(thinking).toHaveAttribute("open");
+    await user.click(within(thinking).getByText("Thinking"));
+    expect(thinking).not.toHaveAttribute("open");
 
     mockLogs([
       makeEntry({ agent: "executor", type: "thinking", text: "First streamed thought" }),
@@ -1253,8 +1236,8 @@ describe("TaskChatTab", () => {
     ]);
     rerender(<TaskChatTab task={makeTask({ column: "todo" })} active addToast={vi.fn()} />);
 
-    expect(screen.getByTestId("task-chat-thinking")).toHaveAttribute("open");
-    expect(screen.getByText(/Second streamed thought/)).toBeVisible();
+    expect(screen.getByTestId("task-chat-thinking")).not.toHaveAttribute("open");
+    expect(screen.getByText(/Second streamed thought/)).not.toBeVisible();
   });
 
   it("gives a genuinely new segment a fresh instance with defaultOpen applied", async () => {
@@ -1302,7 +1285,7 @@ describe("TaskChatTab", () => {
     expect(within(toolGroups[1]).getByLabelText("Tool names")).toHaveTextContent("second tool");
     expect(screen.getAllByTestId("task-chat-entry-text")).toHaveLength(1);
     expect(screen.getByText("plain response")).toBeVisible();
-    expect(screen.getByText("thinking between tools")).not.toBeVisible();
+    expect(screen.getByText("thinking between tools")).toBeVisible();
   });
 
   it("appends newly streamed entries from the hook without auto-opening tool groups", () => {
@@ -2962,7 +2945,7 @@ describe("TaskChatTab", () => {
     const source = readFileSync(resolve(__dirname, "../TaskDetailModal.tsx"), "utf8");
     const taskChatMounts = source.match(/<TaskChatTab\b/g) ?? [];
 
-    expect(source).toContain('import { TaskChatTab } from "../TaskChatTab"');
+    expect(source).toContain('import { TaskChatTab } from "./TaskChatTab"');
     expect(taskChatMounts).toHaveLength(1);
     expect(source).toContain("const isActivityExpanded = activityExpanded && activeTab === \"chat\" && !isEditing");
     expect(source).toContain("task-detail-content--chat-expanded");