diff --git a/proto_roundtrip_test.go b/proto_roundtrip_test.go
new file mode 100644
index 0000000..77f6e5e
--- /dev/null
+++ b/proto_roundtrip_test.go
@@ -0,0 +1,249 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"testing"
+
+	sppb "cloud.google.com/go/spanner/apiv1/spannerpb"
+	"github.com/apstndb/execspansql/jqresult"
+	"github.com/goccy/go-yaml"
+	"github.com/google/go-cmp/cmp"
+	"google.golang.org/protobuf/encoding/protojson"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/testing/protocmp"
+)
+
+func encodeResultSetFormat(filter string, rs *sppb.ResultSet, format string) ([]byte, error) {
+	code, err := jqresult.Compile(filter, jqresult.InputEager)
+	if err != nil {
+		return nil, err
+	}
+	iter, cleanup, err := jqresult.Execute(code, jqresult.InputEager, nil, rs, false)
+	if err != nil {
+		return nil, err
+	}
+	defer cleanup()
+
+	var buf bytes.Buffer
+	enc, err := newEncoder(&buf, format, false, false)
+	if err != nil {
+		return nil, err
+	}
+	if err := jqresult.Print(enc, iter); err != nil {
+		return nil, err
+	}
+	if err := closeEncoder(enc); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+func jqFilterToMap(filter string, rs *sppb.ResultSet) (map[string]any, error) {
+	code, err := jqresult.Compile(filter, jqresult.InputEager)
+	if err != nil {
+		return nil, err
+	}
+	iter, cleanup, err := jqresult.Execute(code, jqresult.InputEager, nil, rs, false)
+	if err != nil {
+		return nil, err
+	}
+	defer cleanup()
+	v, ok := iter.Next()
+	if !ok {
+		return nil, nil
+	}
+	if err, isErr := v.(error); isErr {
+		return nil, err
+	}
+	n, err := jqresult.NormalizeForEncode(v)
+	if err != nil {
+		return nil, err
+	}
+	m, ok := n.(map[string]any)
+	if !ok {
+		return map[string]any{"value": n}, nil
+	}
+	return m, nil
+}
+
+func mapToProtoMessage(m map[string]any, msg proto.Message) error {
+	b, err := json.Marshal(m)
+	if err != nil {
+		return err
+	}
+	return protojson.Unmarshal(b, msg)
+}
+
+func decodeFormatToMap(b []byte, format string) (map[string]any, error) {
+	switch format {
+	case "yaml":
+		var m map[string]any
+		if err := yaml.Unmarshal(b, &m); err != nil {
+			return nil, err
+		}
+		return m, nil
+	case "json":
+		dec := json.NewDecoder(bytes.NewReader(b))
+		dec.UseNumber()
+		var m map[string]any
+		if err := dec.Decode(&m); err != nil {
+			return nil, err
+		}
+		return m, nil
+	default:
+		return nil, nil
+	}
+}
+
+func assertProtoFormatRoundtrip(
+	t *testing.T,
+	rs *sppb.ResultSet,
+	filter string,
+	want proto.Message,
+	format string,
+) {
+	t.Helper()
+
+	encoded, err := encodeResultSetFormat(filter, rs, format)
+	if err != nil {
+		t.Fatalf("encodeResultSetFormat(%q) error = %v", format, err)
+	}
+
+	decoded, err := decodeFormatToMap(encoded, format)
+	if err != nil {
+		t.Fatalf("decode %q output error = %v", format, err)
+	}
+
+	got := proto.Clone(want)
+	proto.Reset(got)
+	if err := mapToProtoMessage(decoded, got); err != nil {
+		t.Fatalf("mapToProtoMessage after %q decode error = %v", format, err)
+	}
+	if diff := cmp.Diff(want, got, protocmp.Transform()); diff != "" {
+		t.Fatalf("%s roundtrip mismatch (-want +got):\n%s", format, diff)
+	}
+}
+
+type protoRoundtripCase struct {
+	name   string
+	rs     *sppb.ResultSet
+	filter string
+	want   func(*sppb.ResultSet) proto.Message
+}
+
+func protoRoundtripCases() []protoRoundtripCase {
+	cases := []protoRoundtripCase{
+		{
+			name:   "all_types_dot",
+			rs:     csvFixtures()["bytes_date_timestamp_numeric"],
+			filter: ".",
+			want:   func(rs *sppb.ResultSet) proto.Message { return rs },
+		},
+		{
+			name:   "dca_albums",
+			rs:     yamlGoldenCases()["dca_albums_rowtype_rows"].rs,
+			filter: ".",
+			want:   func(rs *sppb.ResultSet) proto.Message { return rs },
+		},
+	}
+	for _, tc := range profileYAMLGoldenCases() {
+		if tc.filter != "." {
+			continue
+		}
+		rs, err := loadProfileJSONFixture(tc.jsonFile)
+		if err != nil {
+			panic(err)
+		}
+		cases = append(cases, protoRoundtripCase{
+			name:   tc.golden,
+			rs:     rs,
+			filter: ".",
+			want:   func(rs *sppb.ResultSet) proto.Message { return rs },
+		})
+	}
+	return cases
+}
+
+func TestResultSetProtoJSONRoundtrip(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range protoRoundtripCases() {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			m, err := jqFilterToMap(tc.filter, tc.rs)
+			if err != nil {
+				t.Fatal(err)
+			}
+			got := &sppb.ResultSet{}
+			if err := mapToProtoMessage(m, got); err != nil {
+				t.Fatal(err)
+			}
+			want := tc.want(tc.rs)
+			if diff := cmp.Diff(want, got, protocmp.Transform()); diff != "" {
+				t.Fatalf("protojson roundtrip mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}
+
+func TestResultSetYAMLProtoRoundtrip(t *testing.T) {
+	for _, tc := range protoRoundtripCases() {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			assertProtoFormatRoundtrip(t, tc.rs, tc.filter, tc.want(tc.rs), "yaml")
+		})
+	}
+}
+
+func TestResultSetJSONProtoRoundtrip(t *testing.T) {
+	for _, tc := range protoRoundtripCases() {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			assertProtoFormatRoundtrip(t, tc.rs, tc.filter, tc.want(tc.rs), "json")
+		})
+	}
+}
+
+func TestResultSetSubmessageYAMLProtoRoundtrip(t *testing.T) {
+	rs, err := loadProfileJSONFixture("testdata/profile/singers_limit3.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tests := []struct {
+		name   string
+		filter string
+		want   proto.Message
+	}{
+		{"metadata", ".metadata", rs.GetMetadata()},
+		{"stats", ".stats", rs.GetStats()},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			assertProtoFormatRoundtrip(t, rs, tc.filter, tc.want, "yaml")
+		})
+	}
+}
+
+func TestResultSetSubmessageJSONProtoRoundtrip(t *testing.T) {
+	rs, err := loadProfileJSONFixture("testdata/profile/singers_limit3.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tests := []struct {
+		name   string
+		filter string
+		want   proto.Message
+	}{
+		{"metadata", ".metadata", rs.GetMetadata()},
+		{"stats", ".stats", rs.GetStats()},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			assertProtoFormatRoundtrip(t, rs, tc.filter, tc.want, "json")
+		})
+	}
+}