fix(issues): keep pinned table cells opaque

Co-authored-by: multica-agent <github@multica.ai>

packages/ui/components/ui/data-table.tsx

@@ -223,7 +223,8 @@ export function DataTable<TData>({
               // content scrolling beneath them and follow row hover state.
               className={cn(
                 "overflow-hidden px-4 py-2",
-                isPinned && "bg-background group-hover:bg-muted/50",
+                isPinned &&
+                  "bg-background group-hover:bg-[color-mix(in_oklab,var(--muted)_50%,var(--background))]",
               )}
               style={getCellStyle(cell.column, {
                 withBorder: true,
@@ -293,12 +294,14 @@ export function DataTable<TData>({
                       // exceeds column.size. Tooltip / dropdown /
                       // hover-card bodies are portaled, so they are
                       // unaffected.
-                      // Pinned header cell uses muted/30 so it blends
-                      // into the header strip rather than appearing as
-                      // a white block under sticky scroll.
+                      // Pinned cells must be opaque: translucent backgrounds
+                      // reveal horizontally scrolled columns underneath. Mix
+                      // muted with background to preserve the same visual tone
+                      // as muted/30 without introducing alpha.
                       className={cn(
                         "relative h-8 overflow-hidden px-4 py-2 text-xs uppercase tracking-wider text-muted-foreground",
-                        isPinned && "bg-muted/30 backdrop-blur",
+                        isPinned &&
+                          "bg-[color-mix(in_oklab,var(--muted)_30%,var(--background))]",
                       )}
                       style={getCellStyle(header.column, {
                         withBorder: true,

packages/views/issues/components/data-table-sticky.test.tsx

@@ -0,0 +1,51 @@
+import { render, screen } from "@testing-library/react";
+import {
+  getCoreRowModel,
+  useReactTable,
+  type ColumnDef,
+} from "@tanstack/react-table";
+import { describe, expect, it } from "vitest";
+import { DataTable } from "@multica/ui/components/ui/data-table";
+
+type Row = {
+  title: string;
+  status: string;
+};
+
+const columns: ColumnDef<Row>[] = [
+  { accessorKey: "title", header: "Issue" },
+  { accessorKey: "status", header: "Status" },
+];
+
+function PinnedTable() {
+  const table = useReactTable({
+    data: [{ title: "Pinned title", status: "In progress" }],
+    columns,
+    getCoreRowModel: getCoreRowModel(),
+    state: { columnPinning: { left: ["title"], right: [] } },
+  });
+
+  return <DataTable table={table} />;
+}
+
+describe("DataTable pinned columns", () => {
+  it("uses opaque backgrounds so scrolled columns cannot show through", () => {
+    render(<PinnedTable />);
+
+    const titleHeader = screen.getByRole("columnheader", { name: /^Issue/ });
+    const titleCell = screen.getByRole("cell", { name: "Pinned title" });
+    const statusCell = screen.getByRole("cell", { name: "In progress" });
+
+    expect(titleHeader).toHaveClass(
+      "bg-[color-mix(in_oklab,var(--muted)_30%,var(--background))]",
+    );
+    expect(titleHeader).not.toHaveClass("bg-muted/30", "backdrop-blur");
+    expect(titleCell).toHaveClass(
+      "bg-background",
+      "group-hover:bg-[color-mix(in_oklab,var(--muted)_50%,var(--background))]",
+    );
+    expect(titleCell).not.toHaveClass("group-hover:bg-muted/50");
+    expect(titleCell).toHaveStyle({ position: "sticky", zIndex: 1 });
+    expect(statusCell).not.toHaveStyle({ position: "sticky" });
+  });
+});