FN-8275: clarify mission merge behavior

Clarify mission merge choices and surface shared branch status in mission detail.

- Explain auto-merge and single-pull-request behavior in mission forms
- Show mission-owned shared branch member and PR status
- Cover UI behavior and PostgreSQL triage auto-merge cascading

Files changed:
 .changeset/fn-8275-mission-merge-summary.md        |  7 ++
 docs/missions.md                                   |  2 +-
 .../dashboard/app/components/MissionManager.tsx    | 75 ++++++++++++++++++++++
 .../__tests__/MissionManager.auto-merge.test.tsx   | 64 ++++++++++++++++++
 .../mission-auto-merge-cascade.pg.test.ts          | 58 +++++++++++++++++
 5 files changed, 205 insertions(+), 1 deletion(-)

Fusion-Task-Id: FN-8275

Fusion-Task-Lineage: cd259293-b68e-4bc5-803e-40d2287d8438

Co-authored-by: Fusion (runfusion.ai) <noreply@runfusion.ai>

.changeset/fn-8275-mission-merge-summary.md

@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: Mission auto-merge controls now explain merge behavior and show shared branch PR status.
+category: feature
+dev: Mission detail resolves its group from linked task branchContext data and adds engine cascade coverage.

docs/missions.md

@@ -99,7 +99,7 @@ The Mission Manager create/edit form exposes this as **Branch strategy** plus a
 
 ### Mission auto-merge override
 
-The **Merge behavior** control can inherit the project default, explicitly enable auto-merge, or select **Single pull request**. The latter persists `autoMerge: false` on the mission and stamps newly triaged feature tasks with the same false override, while preserving the mission's shared branch group. Returning the control to inherited clears the mission override.
+The **Merge behavior** control can inherit the project default, explicitly enable auto-merge, or select **Single pull request**. In-context help explains that auto-merge lands each feature individually while a single pull request retains all features on a shared branch for joint review. The latter persists `autoMerge: false` on the mission and stamps newly triaged feature tasks with the same false override, while preserving the mission's shared branch group. Returning the control to inherited clears the mission override. Once a shared branch has members, Mission detail displays its branch name, member count, and PR state.
 
 ### Shared branch-group invariant across entry points
 

packages/dashboard/app/components/MissionManager.tsx

@@ -100,8 +100,11 @@ import {
   fetchAiSession,
   fetchMissionInterviewDrafts,
   discardMissionInterviewDraft,
+  fetchTaskDetail,
+  apiGetBranchGroup,
   api,
   type AiSessionSummary,
+  type BranchGroupSummary,
 } from "../api";
 import type { AutopilotState, MissionInterviewDraftSummary } from "./mission-types";
 import { readCache, SWR_CACHE_KEYS, writeCache } from "../utils/swrCache";
@@ -640,6 +643,7 @@ export function MissionManager({ isOpen, isInline = false, onClose, addToast, pr
   const initialMissions = readCache<MissionWithSummary[]>(missionsCacheKey);
   const [missions, setMissions] = useState<MissionWithSummary[]>(() => (Array.isArray(initialMissions) ? initialMissions : []));
   const [selectedMission, setSelectedMission] = useState<MissionWithHierarchy | null>(null);
+  const [selectedMissionBranchGroup, setSelectedMissionBranchGroup] = useState<BranchGroupSummary | null>(null);
   const [loading, setLoading] = useState(!(Array.isArray(initialMissions) && initialMissions.length > 0));
   const hasHydratedRef = useRef(Array.isArray(initialMissions) && initialMissions.length > 0);
   const [detailLoading, setDetailLoading] = useState(false);
@@ -1121,6 +1125,41 @@ export function MissionManager({ isOpen, isInline = false, onClose, addToast, pr
     }
   }, [addToast, loadAssertionsForMilestone, projectId]);
 
+  useEffect(() => {
+    let cancelled = false;
+    setSelectedMissionBranchGroup(null);
+
+    const selectedMissionId = selectedMission?.id;
+    const taskIds = selectedMission?.milestones.flatMap((milestone) =>
+      milestone.slices.flatMap((slice) => slice.features.flatMap((feature) => feature.taskId ? [feature.taskId] : [])),
+    ) ?? [];
+    if (!selectedMissionId || taskIds.length === 0) return () => { cancelled = true; };
+
+    void (async () => {
+      for (const taskId of taskIds) {
+        try {
+          const task = await fetchTaskDetail(taskId, projectId);
+          const groupId = task.branchContext?.source === "mission" ? task.branchContext.groupId : undefined;
+          if (!groupId) continue;
+          const { group } = await apiGetBranchGroup(groupId, projectId);
+          /*
+          FNXC:MissionAutoMerge 2026-07-19-00:00:
+          A task can retain a stale or colliding branch-group id. Only show a group that
+          is owned by the selected mission so its detail pane never reports another
+          mission's branch or PR state.
+          */
+          if (group?.sourceType !== "mission" || group.sourceId !== selectedMissionId) continue;
+          if (!cancelled) setSelectedMissionBranchGroup(group);
+          return;
+        } catch {
+          // A stale/deleted linked task or unavailable group must not break mission detail rendering.
+        }
+      }
+    })();
+
+    return () => { cancelled = true; };
+  }, [projectId, selectedMission]);
+
   useEffect(() => {
     if (!isActive || !selectedMilestoneId) {
       setValidationTelemetry(null);
@@ -2739,6 +2778,29 @@ export function MissionManager({ isOpen, isInline = false, onClose, addToast, pr
                     )}
                   </div>
 
+                  {/*
+                  FNXC:MissionAutoMerge 2026-07-19-00:00:
+                  A mission detail must show its actual shared branch, member count, and PR state. Resolve the group through linked member tasks' branchContext.groupId rather than source ownership because branch-name collisions can reuse another mission's group.
+                  */}
+                  {selectedMissionBranchGroup && (
+                    <div className="mission-detail__autopilot" data-testid="mission-shared-branch-summary">
+                      <div className="mission-detail__autopilot-toggle">
+                        <span>{t("missions.sharedBranch", "Shared branch")}: {selectedMissionBranchGroup.branchName}</span>
+                        <span
+                          className="mission-status-badge mission-status-badge--sm"
+                          style={{ backgroundColor: "var(--surface-hover)", color: "var(--text-muted)" }}
+                        >
+                          {selectedMissionBranchGroup.prState === "none"
+                            ? t("missions.noPullRequest", "No PR")
+                            : t(`missions.prState.${selectedMissionBranchGroup.prState}`, selectedMissionBranchGroup.prState)}
+                        </span>
+                      </div>
+                      <span className="mission-detail__autopilot-description">
+                        {t("missions.sharedBranchMembers", "{{count}} member", { count: selectedMissionBranchGroup.completion.total })}
+                      </span>
+                    </div>
+                  )}
+
                   <div className="mission-detail__actions">
                     <div className="mission-detail__run-controls">
                     {selectedMission.status === "active" && (
@@ -2859,6 +2921,13 @@ export function MissionManager({ isOpen, isInline = false, onClose, addToast, pr
                       <option value="on">{t("missions.autoMergeOn", "Auto-merge")}</option>
                       <option value="off">{t("missions.singlePullRequest", "Single pull request")}</option>
                     </select>
+                    {/*
+                    FNXC:MissionAutoMerge 2026-07-19-00:00:
+                    Operators need in-context guidance for the per-mission merge choice: auto-merge lands each feature independently, while a single pull request keeps all features on one shared branch for joint review.
+                    */}
+                    <span className="mission-detail__autopilot-description">
+                      {t("missions.autoMergeOverrideDescription", "Auto-merge merges each feature as it passes. Single pull request keeps every feature on one shared branch to review and merge together.")}
+                    </span>
                   </label>
                   {(missionForm.branchStrategy.mode === "existing" || missionForm.branchStrategy.mode === "custom-new") && (
                     <label>
@@ -4596,6 +4665,9 @@ export function MissionManager({ isOpen, isInline = false, onClose, addToast, pr
                       <option value="on">{t("missions.autoMergeOn", "Auto-merge")}</option>
                       <option value="off">{t("missions.singlePullRequest", "Single pull request")}</option>
                     </select>
+                    <span className="mission-detail__autopilot-description">
+                      {t("missions.autoMergeOverrideDescription", "Auto-merge merges each feature as it passes. Single pull request keeps every feature on one shared branch to review and merge together.")}
+                    </span>
                   </label>
                   {(missionForm.branchStrategy.mode === "existing" || missionForm.branchStrategy.mode === "custom-new") && (
                     <label>
@@ -4702,6 +4774,9 @@ export function MissionManager({ isOpen, isInline = false, onClose, addToast, pr
                       <option value="on">{t("missions.autoMergeOn", "Auto-merge")}</option>
                       <option value="off">{t("missions.singlePullRequest", "Single pull request")}</option>
                     </select>
+                    <span className="mission-detail__autopilot-description">
+                      {t("missions.autoMergeOverrideDescription", "Auto-merge merges each feature as it passes. Single pull request keeps every feature on one shared branch to review and merge together.")}
+                    </span>
                   </label>
                   {(missionForm.branchStrategy.mode === "existing" || missionForm.branchStrategy.mode === "custom-new") && (
                     <label>

packages/dashboard/app/components/__tests__/MissionManager.auto-merge.test.tsx

@@ -14,6 +14,8 @@ const mockFetchMissionsHealth = vi.fn();
 const mockFetchAiSessions = vi.fn();
 const mockFetchMissionInterviewDrafts = vi.fn();
 const mockUpdateMission = vi.fn();
+const mockFetchTaskDetail = vi.fn();
+const mockGetBranchGroup = vi.fn();
 
 vi.mock("../../hooks/useNavigationHistory", async (importOriginal) => {
   const actual = await importOriginal<typeof import("../../hooks/useNavigationHistory")>();
@@ -33,6 +35,8 @@ vi.mock("../../api", async (importOriginal) => {
     fetchAiSessions: (...args: unknown[]) => mockFetchAiSessions(...args),
     fetchMissionInterviewDrafts: (...args: unknown[]) => mockFetchMissionInterviewDrafts(...args),
     updateMission: (...args: unknown[]) => mockUpdateMission(...args),
+    fetchTaskDetail: (...args: unknown[]) => mockFetchTaskDetail(...args),
+    apiGetBranchGroup: (...args: unknown[]) => mockGetBranchGroup(...args),
   };
 });
 
@@ -88,6 +92,18 @@ describe("MissionManager auto-merge override", () => {
     mockFetchAiSessions.mockResolvedValue([]);
     mockFetchMissionInterviewDrafts.mockResolvedValue([]);
     mockUpdateMission.mockResolvedValue(mission());
+    mockFetchTaskDetail.mockResolvedValue({});
+    mockGetBranchGroup.mockResolvedValue({ group: null });
+  });
+
+  it("renders merge behavior guidance in both mission edit forms", async () => {
+    await openEditForm();
+    expect(screen.getByText(/Single pull request keeps every feature/i)).toBeInTheDocument();
+
+    fireEvent.click(screen.getByRole("button", { name: "Cancel" }));
+    const editButtons = screen.getAllByRole("button", { name: "Edit mission" });
+    fireEvent.click(editButtons.at(-1)!);
+    expect(screen.getByText(/Single pull request keeps every feature/i)).toBeInTheDocument();
   });
 
   it.each([
@@ -113,6 +129,54 @@ describe("MissionManager auto-merge override", () => {
     });
   });
 
+  it("rejects a reused branch group owned by a different mission", async () => {
+    const first = {
+      ...mission(false),
+      milestones: [{ id: "MS-001", title: "Milestone", status: "planning", createdAt: now, updatedAt: now, slices: [{ id: "SL-001", title: "Slice", status: "pending", createdAt: now, updatedAt: now, features: [{ id: "F-001", title: "Feature", taskId: "FN-001", status: "triaged", createdAt: now, updatedAt: now }] }] }],
+    };
+    const second = {
+      ...mission(false), id: "M-002", title: "Collision Mission",
+      milestones: [{ id: "MS-002", title: "Milestone", status: "planning", createdAt: now, updatedAt: now, slices: [{ id: "SL-002", title: "Slice", status: "pending", createdAt: now, updatedAt: now, features: [{ id: "F-002", title: "Feature", taskId: "FN-002", status: "triaged", createdAt: now, updatedAt: now }] }] }],
+    };
+    mockFetchMissions.mockResolvedValue([first, second]);
+    mockFetchMission.mockImplementation((id: string) => Promise.resolve(id === "M-001" ? first : second));
+    mockFetchTaskDetail.mockImplementation((id: string) => Promise.resolve({
+      id,
+      branchContext: { source: "mission", groupId: "BG-001", assignmentMode: "shared" },
+    }));
+    mockGetBranchGroup.mockResolvedValue({ group: {
+      id: "BG-001", sourceType: "mission", sourceId: "M-001", branchName: "main", autoMerge: false,
+      prState: "open", status: "open", createdAt: 0, updatedAt: 0, members: [], completion: { landed: 0, total: 2, complete: false },
+    } });
+
+    render(<MissionManager isInline isOpen onClose={() => {}} addToast={() => {}} projectId="project-1" />);
+    fireEvent.click(await screen.findByText("Collision Mission"));
+    await waitFor(() => expect(mockGetBranchGroup).toHaveBeenCalledWith("BG-001", "project-1"));
+    expect(screen.queryByTestId("mission-shared-branch-summary")).toBeNull();
+  });
+
+  it("shows the selected mission's owned branch group without an action button", async () => {
+    const detail = {
+      ...mission(false),
+      milestones: [{ id: "MS-001", title: "Milestone", status: "planning", createdAt: now, updatedAt: now, slices: [{ id: "SL-001", title: "Slice", status: "pending", createdAt: now, updatedAt: now, features: [{ id: "F-001", title: "Feature", taskId: "FN-001", status: "triaged", createdAt: now, updatedAt: now }] }] }],
+    };
+    mockFetchMissions.mockResolvedValue([detail]);
+    mockFetchMission.mockResolvedValue(detail);
+    mockFetchTaskDetail.mockResolvedValue({ id: "FN-001", branchContext: { source: "mission", groupId: "BG-001", assignmentMode: "shared" } });
+    mockGetBranchGroup.mockResolvedValue({ group: {
+      id: "BG-001", sourceType: "mission", sourceId: "M-001", branchName: "main", autoMerge: false,
+      prState: "open", status: "open", createdAt: 0, updatedAt: 0, members: [], completion: { landed: 0, total: 2, complete: false },
+    } });
+
+    render(<MissionManager isInline isOpen onClose={() => {}} addToast={() => {}} projectId="project-1" />);
+    fireEvent.click(await screen.findByText("Single PR Mission"));
+    const summary = await screen.findByTestId("mission-shared-branch-summary");
+    expect(summary).toHaveTextContent("main");
+    expect(summary).toHaveTextContent("2 member");
+    expect(summary).toHaveTextContent("open");
+    expect(summary.querySelector("button")).toBeNull();
+  });
+
   it.each([
     ["on", true],
     ["off", false],

packages/engine/src/__tests__/mission-auto-merge-cascade.pg.test.ts

@@ -0,0 +1,58 @@
+/*
+FNXC:MissionAutoMerge 2026-07-19-00:00:
+Engine coverage must prove the production PostgreSQL MissionStore path stamps only
+single-pull-request mission tasks and puts every member in the same lazy branch group.
+*/
+import { expect, it } from "vitest";
+import type { AsyncMissionStore } from "@fusion/core";
+import { createTaskStoreForTest, pgDescribe } from "../../../core/src/__test-utils__/pg-test-harness.js";
+
+pgDescribe("mission auto-merge cascade PostgreSQL", () => {
+  it("stamps false missions and preserves inherited true or undefined missions", async () => {
+    const harness = await createTaskStoreForTest({ prefix: "fusion_mission_auto_merge_cascade" });
+    try {
+      const missions = harness.store.getMissionStore() as AsyncMissionStore;
+      const singlePr = await missions.createMission({ title: "Single PR", autoMerge: false });
+      const milestone = await missions.addMilestone(singlePr.id, { title: "Milestone" });
+      const slice = await missions.addSlice(milestone.id, { title: "Slice" });
+      const first = await missions.addFeature(slice.id, { title: "First feature" });
+      const second = await missions.addFeature(slice.id, { title: "Second feature" });
+      await missions.triageFeature(first.id);
+      await missions.triageFeature(second.id);
+
+      const tasks = (await harness.store.listTasks()).filter((task) =>
+        ["First feature", "Second feature"].includes(task.title),
+      );
+      expect(tasks).toHaveLength(2);
+      expect(tasks.map((task) => task.autoMerge)).toEqual([false, false]);
+      const groupIds = new Set(tasks.map((task) => task.branchContext?.groupId));
+      expect(groupIds.size).toBe(1);
+      const groupId = tasks[0]?.branchContext?.groupId;
+      expect(groupId).toBeDefined();
+
+      // FNXC:MissionAutoMerge 2026-07-19-16:35:
+      // A shared task context is useful only when it points to the lazily materialized
+      // group that owns this mission and contains every triaged member. Assert the
+      // persisted group rather than accepting a matching but dangling group id.
+      const group = await harness.store.getBranchGroup(groupId!);
+      expect(group).toMatchObject({
+        id: groupId,
+        sourceType: "mission",
+        sourceId: singlePr.id,
+      });
+      expect(await harness.store.listTasksByBranchGroup(groupId!)).toHaveLength(2);
+
+      for (const autoMerge of [true, undefined] as const) {
+        const mission = await missions.createMission({ title: `Inherited ${String(autoMerge)}`, autoMerge });
+        const inheritedMilestone = await missions.addMilestone(mission.id, { title: "Milestone" });
+        const inheritedSlice = await missions.addSlice(inheritedMilestone.id, { title: "Slice" });
+        const feature = await missions.addFeature(inheritedSlice.id, { title: `Feature ${String(autoMerge)}` });
+        await missions.triageFeature(feature.id);
+        const task = (await harness.store.listTasks()).find((candidate) => candidate.title === `Feature ${String(autoMerge)}`);
+        expect(task?.autoMerge).toBeUndefined();
+      }
+    } finally {
+      await harness.teardown();
+    }
+  });
+});