diff --git a/frontend/src/components/data-table/DataTable.jsx b/frontend/src/components/data-table/DataTable.jsx
index ddf6b17fad..da80224549 100644
--- a/frontend/src/components/data-table/DataTable.jsx
+++ b/frontend/src/components/data-table/DataTable.jsx
@@ -39,6 +39,24 @@ import { cn } from "@/lib/utils";
  * import it rather than build their own.
  */
 
+/**
+ * One cell's value, read the way antd reads it.
+ *
+ * `dataIndex` is either a key or a PATH: `["product", "name"]` is antd's
+ * documented nested form and means `record.product.name`. The flat lookup this
+ * replaces indexed the record with the array itself, and JavaScript stringifies
+ * that to the property name `"product,name"` — so the value was always
+ * undefined, and silently so, because a column with no `render` hands it
+ * straight to the cell. LLMWhisperer's API Keys table declares its Plan column
+ * exactly that way and lost the whole column to a blank strip.
+ */
+function cellValue(record, dataIndex) {
+  if (Array.isArray(dataIndex)) {
+    return dataIndex.reduce((v, k) => (v == null ? undefined : v[k]), record);
+  }
+  return record?.[dataIndex];
+}
+
 /**
  * One antd column → one TanStack column def.
  *
@@ -53,6 +71,14 @@ import { cn } from "@/lib/utils";
  * version used would collide across levels.
  */
 function toColumn(c, path) {
+  /*
+   * Three places spell this identity, and they must agree: here, `columnKey`
+   * (ColumnFilter.jsx) and `toSorterInfo` below, which matches on it to answer
+   * antd's `onChange`. A PATH `dataIndex` with no `key` coerces to
+   * `"product,name"` in all three, so they still agree — which is why this is
+   * deliberately NOT normalised to `dataIndex.join(".")`. Tidying it here alone
+   * would silently stop sorting and filtering reporting for a nested column.
+   */
   const id = String(c.key ?? c.dataIndex ?? path);
   // `column` rides along so the header can render antd's filter affordance,
   // which is declared on the antd def and has no TanStack equivalent.
@@ -76,7 +102,31 @@ function toColumn(c, path) {
 
   return {
     id,
-    accessorKey: c.dataIndex,
+    /*
+     * A path needs an accessor FUNCTION: TanStack's `accessorKey` is a single
+     * key, so handing it the array repeats the same stringified-`"product,name"`
+     * lookup one layer down.
+     *
+     * This is NOT inert. TanStack defaults every column to `sortUndefined: 1`,
+     * and `getSortedRowModel` reads `row.getValue()` to apply it BEFORE it ever
+     * consults `sortingFn` — so undefined-valued rows sort to the end even
+     * though `sortingFn` is `() => 0`. A nested column was accidentally exempt
+     * while every one of its values was undefined; with a real accessor it now
+     * behaves exactly as an equivalent string column already does (verified:
+     * both reorder identically on a sparse column). That quirk is pre-existing
+     * and cross-cutting, not introduced here, and no nested column declares a
+     * `sorter` today.
+     *
+     * The string case keeps `accessorKey` because it is unchanged, not because
+     * its behaviour is right: TanStack deep-reads a DOTTED string while the
+     * cell below reads it as a literal key, which is antd's own reading. Those
+     * two disagree for `dataIndex: "a.b"`. Pre-existing on both halves, no
+     * literal dotted `dataIndex` exists in either repo, and reconciling it is a
+     * behaviour change beyond this fix.
+     */
+    ...(Array.isArray(c.dataIndex)
+      ? { accessorFn: (record) => cellValue(record, c.dataIndex) }
+      : { accessorKey: c.dataIndex }),
     header: c.title,
     enableSorting: Boolean(c.sorter),
     /*
@@ -95,7 +145,9 @@ function toColumn(c, path) {
         : () => 0,
     meta,
     cell: ({ row }) => {
-      const value = c.dataIndex ? row.original?.[c.dataIndex] : undefined;
+      const value = c.dataIndex
+        ? cellValue(row.original, c.dataIndex)
+        : undefined;
       // antd's render(value, record, index) contract.
       return c.render ? c.render(value, row.original, row.index) : value;
     },
diff --git a/frontend/src/components/data-table/DataTable.test.jsx b/frontend/src/components/data-table/DataTable.test.jsx
index d305594ffc..f2faccdbbd 100644
--- a/frontend/src/components/data-table/DataTable.test.jsx
+++ b/frontend/src/components/data-table/DataTable.test.jsx
@@ -1521,3 +1521,128 @@ describe("DataTable controlled filters", () => {
     });
   });
 });
+
+/**
+ * antd's `dataIndex` is either a key or a PATH — `["product", "name"]` reads
+ * `record.product.name`. The flat lookup this guards indexed the record with
+ * the array itself, which JavaScript stringifies to the property name
+ * `"product,name"`, so the value was always undefined and — because a column
+ * with no `render` hands it straight to the cell — silently blank.
+ *
+ * LLMWhisperer's API Keys table declares its Plan column exactly this way and
+ * lost the whole column to an empty strip after the migration.
+ */
+describe("DataTable nested dataIndex", () => {
+  const nested = [
+    { id: 1, product: { id: "free", name: "LLM Whisperer Free" } },
+  ];
+
+  it("resolves an array dataIndex as a path into the record", () => {
+    render(
+      <DataTable
+        columns={[
+          {
+            title: "Plan",
+            dataIndex: ["product", "name"],
+            key: "product_name",
+          },
+        ]}
+        dataSource={nested}
+        rowKey="id"
+      />,
+    );
+    expect(screen.getByText("LLM Whisperer Free")).toBeInTheDocument();
+  });
+
+  it("renders an empty cell rather than throwing on a missing segment", () => {
+    expect(() =>
+      render(
+        <DataTable
+          columns={[
+            {
+              title: "Plan",
+              dataIndex: ["product", "name"],
+              key: "product_name",
+            },
+          ]}
+          dataSource={[{ id: 1, product: null }, { id: 2 }]}
+          rowKey="id"
+        />,
+      ),
+    ).not.toThrow();
+    // Two rows, both with an EMPTY Plan cell — not the empty state, and not a
+    // stand-in like "undefined" or "N/A" that a laxer resolver would print.
+    const cells = document.querySelectorAll("tbody td");
+    expect(cells).toHaveLength(2);
+    for (const cell of cells) {
+      expect(cell).toHaveTextContent("");
+    }
+  });
+
+  it("walks a path of any depth, including an array index", () => {
+    render(
+      <DataTable
+        columns={[
+          {
+            title: "Owner",
+            dataIndex: ["subscription", "owners", 0, "email"],
+            key: "owner",
+          },
+        ]}
+        dataSource={[
+          { id: 1, subscription: { owners: [{ email: "a@example.com" }] } },
+        ]}
+        rowKey="id"
+      />,
+    );
+    expect(screen.getByText("a@example.com")).toBeInTheDocument();
+  });
+
+  /*
+   * The identity a nested column reports back through antd's `onChange`.
+   *
+   * With no `key`, the column id and `toSorterInfo`'s lookup both coerce the
+   * array to `"product,name"` — agreeing only because NEITHER normalises it.
+   * Normalising the id alone (to `"product.name"`, say) is exactly the tidy-up
+   * a later reader would attempt, and it would silently stop a nested column
+   * reporting its sort, with every other test here still green.
+   */
+  it("reports a keyless nested column through onChange when sorted", async () => {
+    const onChange = vi.fn();
+    render(
+      <DataTable
+        columns={[
+          { title: "Plan", dataIndex: ["product", "name"], sorter: true },
+        ]}
+        dataSource={nested}
+        rowKey="id"
+        onChange={onChange}
+      />,
+    );
+    await userEvent.click(screen.getByText("Plan"));
+    expect(onChange).toHaveBeenCalled();
+    const sorter = onChange.mock.calls.at(-1)[2];
+    expect(sorter.field).toEqual(["product", "name"]);
+    expect(sorter.order).toBe("ascend");
+  });
+
+  it("hands the resolved nested value to render, as antd does", () => {
+    const renderCell = vi.fn((value) => `plan: ${value}`);
+    render(
+      <DataTable
+        columns={[
+          {
+            title: "Plan",
+            dataIndex: ["product", "name"],
+            key: "product_name",
+            render: renderCell,
+          },
+        ]}
+        dataSource={nested}
+        rowKey="id"
+      />,
+    );
+    expect(renderCell).toHaveBeenCalledWith("LLM Whisperer Free", nested[0], 0);
+    expect(screen.getByText("plan: LLM Whisperer Free")).toBeInTheDocument();
+  });
+});