fix(jsonview): keep single-column stream tables column-shaped

internal/jsonview/explorer.go

@@ -181,7 +181,10 @@ func (tv *TableView) loadMoreData() tea.Cmd {
 func (tv *TableView) appendItem(result gjson.Result, raw bool) {
 	tv.rowData = append(tv.rowData, result)
 	newRow := table.Row{formatValue(result, raw)}
-	if len(tv.columns) > 1 && result.IsObject() {
+	// columnKeys is only populated by the array-of-objects constructor, so it — not
+	// the column count — says whether this table is column-shaped. A stream whose
+	// items share a single key still has exactly one column.
+	if len(tv.columnKeys) > 0 && result.IsObject() {
 		newRow = make(table.Row, len(tv.columns))
 		values := result.Map()
 		for i, col := range tv.columns {

internal/jsonview/explorer_single_key_test.go

@@ -0,0 +1,84 @@
+package jsonview
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+
+	"github.com/charmbracelet/bubbles/help"
+	"github.com/stretchr/testify/require"
+	"github.com/tidwall/gjson"
+)
+
+// A streamed array whose items all share a single key keeps a one-column table.
+// Rows appended by the lazy loader must go through the same column mapping as the
+// preloaded rows, otherwise the table silently changes shape mid-scroll.
+func TestExplorerLazyLoadSingleKeyRowsStayColumnShaped(t *testing.T) {
+	for _, raw := range []bool{false, true} {
+		t.Run(fmt.Sprintf("raw=%v", raw), func(t *testing.T) {
+			view, err := newTableView("", gjson.Parse(`[{"id":"first"}]`), raw)
+			require.NoError(t, err)
+			require.Len(t, view.columns, 1)
+			require.Equal(t, "id", view.columns[0].Title)
+
+			view.iterator = &explorerIterator{items: []any{json.RawMessage(`{"id":"second"}`)}}
+			v := &JSONViewer{stack: []JSONView{view}, root: "test", help: help.New(), rawMode: raw}
+			v.resize(80, 24)
+
+			preloaded := view.table.Rows()[0]
+
+			cmd := explorerKey(v, "j")
+			require.NotNil(t, cmd)
+			v.Update(cmd())
+
+			require.Len(t, view.rowData, 2)
+			rows := view.table.Rows()
+			require.Len(t, rows, 2)
+			require.Len(t, rows[1], len(view.columns), "appended row must match the column count")
+			require.Equal(t, len(preloaded), len(rows[1]), "appended row must render like the preloaded rows")
+			if raw {
+				require.Equal(t, []string{`"second"`}, []string(rows[1]))
+			} else {
+				require.Equal(t, []string{"second"}, []string(rows[1]))
+			}
+		})
+	}
+}
+
+// A column-shaped table keeps its shape when a streamed item carries keys the
+// preloaded items never showed.
+func TestExplorerLazyLoadSingleKeyIgnoresUnknownKeys(t *testing.T) {
+	view, err := newTableView("", gjson.Parse(`[{"id":"first"}]`), false)
+	require.NoError(t, err)
+	view.iterator = &explorerIterator{items: []any{json.RawMessage(`{"id":"second","extra":"dropped"}`)}}
+	v := &JSONViewer{stack: []JSONView{view}, root: "test", help: help.New()}
+	v.resize(80, 24)
+
+	cmd := explorerKey(v, "j")
+	require.NotNil(t, cmd)
+	v.Update(cmd())
+
+	rows := view.table.Rows()
+	require.Len(t, rows, 2)
+	require.Equal(t, []string{"second"}, []string(rows[1]))
+	require.Equal(t, `{"id":"second","extra":"dropped"}`, view.rowData[1].Raw,
+		"the full item must stay reachable even though only known columns render")
+}
+
+// A plain (non-object) array keeps the single "Items" column rendering.
+func TestExplorerLazyLoadScalarArrayKeepsItemColumn(t *testing.T) {
+	view, err := newTableView("", gjson.Parse(`["one"]`), false)
+	require.NoError(t, err)
+	require.Nil(t, view.columnKeys)
+	view.iterator = &explorerIterator{items: []any{json.RawMessage(`"two"`)}}
+	v := &JSONViewer{stack: []JSONView{view}, root: "test", help: help.New()}
+	v.resize(80, 24)
+
+	cmd := explorerKey(v, "j")
+	require.NotNil(t, cmd)
+	v.Update(cmd())
+
+	rows := view.table.Rows()
+	require.Len(t, rows, 2)
+	require.Equal(t, []string{"two"}, []string(rows[1]))
+}