diff --git a/packages/ui/src/features/tasks/taskKeys.ts b/packages/ui/src/features/tasks/taskKeys.ts
index 894907235..d805aec7f 100644
--- a/packages/ui/src/features/tasks/taskKeys.ts
+++ b/packages/ui/src/features/tasks/taskKeys.ts
@@ -1,12 +1,19 @@
+export interface TaskListFilters {
+  repository?: string;
+  createdBy?: number;
+  originProduct?: string;
+  internal?: boolean;
+}
+
 export const taskKeys = {
   all: ["tasks"] as const,
   lists: () => [...taskKeys.all, "list"] as const,
-  list: (filters?: {
-    repository?: string;
-    createdBy?: number;
-    originProduct?: string;
-    internal?: boolean;
-  }) => [...taskKeys.lists(), filters] as const,
+  list: (filters?: TaskListFilters) => [...taskKeys.lists(), filters] as const,
+  // Extract the filters object from a `list` query key. Keeps knowledge of the
+  // key's shape (filters live in the last slot) here, next to `list`, instead
+  // of letting consumers reach in by positional index.
+  filtersOf: (queryKey: readonly unknown[]): TaskListFilters | undefined =>
+    queryKey[queryKey.length - 1] as TaskListFilters | undefined,
   allSummaries: () => [...taskKeys.all, "summaries"] as const,
   summaries: (ids: string[]) =>
     [...taskKeys.allSummaries(), [...ids].sort()] as const,
diff --git a/packages/ui/src/features/tasks/useTaskCrudMutations.test.tsx b/packages/ui/src/features/tasks/useTaskCrudMutations.test.tsx
index 0bb0397a8..c63b4c9c6 100644
--- a/packages/ui/src/features/tasks/useTaskCrudMutations.test.tsx
+++ b/packages/ui/src/features/tasks/useTaskCrudMutations.test.tsx
@@ -1,3 +1,4 @@
+import type { Task } from "@posthog/shared/domain-types";
 import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
 import { renderHook } from "@testing-library/react";
 import type { ReactNode } from "react";
@@ -27,7 +28,8 @@ vi.mock("@posthog/di/react", () => ({
   useService: () => deletionService,
 }));
 
-import { useDeleteTask } from "./useTaskCrudMutations";
+import { taskKeys } from "./taskKeys";
+import { useCreateTask, useDeleteTask } from "./useTaskCrudMutations";
 
 function wrapper({ children }: { children: ReactNode }) {
   const queryClient = new QueryClient();
@@ -36,6 +38,20 @@ function wrapper({ children }: { children: ReactNode }) {
   );
 }
 
+function createTask(overrides: Partial<Task> = {}): Task {
+  return {
+    id: "new-task",
+    task_number: 1,
+    slug: "new-task",
+    title: "New task",
+    description: "New task",
+    created_at: "2026-06-15T00:00:00.000Z",
+    updated_at: "2026-06-15T00:00:00.000Z",
+    origin_product: "user_created",
+    ...overrides,
+  };
+}
+
 describe("useDeleteTask.deleteWithConfirm", () => {
   beforeEach(() => {
     vi.clearAllMocks();
@@ -71,3 +87,66 @@ describe("useDeleteTask.deleteWithConfirm", () => {
     expect(ok).toBe(false);
   });
 });
+
+describe("useCreateTask.invalidateTasks", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it.each([
+    { name: "plain list", filters: undefined, expectedLength: 1 },
+    {
+      name: "repository-scoped list",
+      filters: { repository: "owner/repo" },
+      expectedLength: 1,
+    },
+    {
+      name: "slack-origin list",
+      filters: { originProduct: "slack" },
+      expectedLength: 0,
+    },
+  ])(
+    "seeds the $name with the new task ($expectedLength entr(y/ies))",
+    ({ filters, expectedLength }) => {
+      const queryClient = new QueryClient();
+      const key = taskKeys.list(filters);
+      queryClient.setQueryData<Task[]>(key, []);
+
+      const localWrapper = ({ children }: { children: ReactNode }) => (
+        <QueryClientProvider client={queryClient}>
+          {children}
+        </QueryClientProvider>
+      );
+      const { result } = renderHook(() => useCreateTask(), {
+        wrapper: localWrapper,
+      });
+
+      result.current.invalidateTasks(createTask());
+
+      // Origin-less lists mirror the new task; origin-scoped lists (read by the
+      // sidebar to brand icons by id membership) must not be seeded.
+      expect(queryClient.getQueryData<Task[]>(key)).toHaveLength(
+        expectedLength,
+      );
+    },
+  );
+
+  it("still invalidates every list, including the slack-origin one", () => {
+    const queryClient = new QueryClient();
+    const invalidateSpy = vi.spyOn(queryClient, "invalidateQueries");
+
+    const localWrapper = ({ children }: { children: ReactNode }) => (
+      <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>
+    );
+    const { result } = renderHook(() => useCreateTask(), {
+      wrapper: localWrapper,
+    });
+
+    result.current.invalidateTasks(createTask());
+
+    // Seeding is scoped, but the refetch is not: all lists (slack included) are
+    // invalidated so they reconcile with the server. A future refactor must not
+    // "fix" the no-seed expectation above by dropping a list from refetch.
+    expect(invalidateSpy).toHaveBeenCalledWith({ queryKey: taskKeys.lists() });
+  });
+});
diff --git a/packages/ui/src/features/tasks/useTaskCrudMutations.ts b/packages/ui/src/features/tasks/useTaskCrudMutations.ts
index 8e977f03f..70111964e 100644
--- a/packages/ui/src/features/tasks/useTaskCrudMutations.ts
+++ b/packages/ui/src/features/tasks/useTaskCrudMutations.ts
@@ -18,8 +18,22 @@ export function useCreateTask() {
 
   const invalidateTasks = (newTask?: Task) => {
     if (newTask) {
+      // Only seed list caches that aren't scoped to a specific origin_product.
+      // An origin-scoped list (e.g. the slack-origin list behind useSlackTasks)
+      // is read by the sidebar to brand a task's icon by id membership, so
+      // seeding a freshly created, non-slack task into it would make that task
+      // briefly render as a Slack task until the list refetches. Origin-less
+      // lists, by contrast, should mirror every new task.
       queryClient.setQueriesData<Task[]>(
-        { queryKey: taskKeys.lists() },
+        {
+          queryKey: taskKeys.lists(),
+          predicate: (query) => {
+            const isOriginScopedList = Boolean(
+              taskKeys.filtersOf(query.queryKey)?.originProduct,
+            );
+            return !isOriginScopedList;
+          },
+        },
         (old) => insertTaskDedup(old, newTask),
       );
     }