diff --git a/cmd/psql.go b/cmd/psql.go
index 3ff0ae7..c3fc918 100644
--- a/cmd/psql.go
+++ b/cmd/psql.go
@@ -100,7 +100,7 @@ func init() {
 				return fmt.Errorf("postgres ID or name is required in non-interactive mode")
 			}
 
-			result, err := views.ExecutePSQLNonInteractive(ctx, &input)
+			result, err := views.ExecutePSQLNonInteractive(ctx, &input, cmd.InOrStdin(), cmd.ErrOrStderr())
 			if err != nil {
 				return err
 			}
diff --git a/pkg/tui/views/psql.go b/pkg/tui/views/psql.go
index 0acd74d..ac9d333 100644
--- a/pkg/tui/views/psql.go
+++ b/pkg/tui/views/psql.go
@@ -42,7 +42,12 @@ type PSQLResult struct {
 	Output string `json:"output"`
 }
 
-func ExecutePSQLNonInteractive(ctx context.Context, input *PSQLInput) (*PSQLResult, error) {
+// ExecutePSQLNonInteractive runs input.Command and returns the tool's stdout.
+// The tool reads stdin, so data the caller pipes in reaches commands that
+// consume it, such as \copy ... FROM pstdin. Diagnostics the tool writes to
+// stderr on success (WARNING/NOTICE) are forwarded to diagnostics unchanged,
+// so they are not lost while the structured result stays stdout only.
+func ExecutePSQLNonInteractive(ctx context.Context, input *PSQLInput, stdin io.Reader, diagnostics io.Writer) (*PSQLResult, error) {
 	c, err := client.NewDefaultClient()
 	if err != nil {
 		return nil, err
@@ -77,13 +82,16 @@ func ExecutePSQLNonInteractive(ctx context.Context, input *PSQLInput) (*PSQLResu
 		args = append(args, arg)
 	}
 
-	cmd := exec.CommandContext(ctx, string(input.Tool), args...)
+	return runPSQLCommand(exec.CommandContext(ctx, string(input.Tool), args...), stdin, diagnostics)
+}
 
+func runPSQLCommand(cmd *exec.Cmd, stdin io.Reader, diagnostics io.Writer) (*PSQLResult, error) {
 	var stdout, stderr bytes.Buffer
+	cmd.Stdin = stdin
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr
 
-	err = cmd.Run()
+	err := cmd.Run()
 	if err != nil {
 		errMsg := stderr.String()
 		if errMsg != "" {
@@ -92,6 +100,11 @@ func ExecutePSQLNonInteractive(ctx context.Context, input *PSQLInput) (*PSQLResu
 		return nil, err
 	}
 
+	if stderr.Len() > 0 && diagnostics != nil {
+		if _, err := diagnostics.Write(stderr.Bytes()); err != nil {
+			return nil, err
+		}
+	}
 	return &PSQLResult{Output: stdout.String()}, nil
 }
 
diff --git a/pkg/tui/views/psql_test.go b/pkg/tui/views/psql_test.go
index 8d9ff6c..a67fa16 100644
--- a/pkg/tui/views/psql_test.go
+++ b/pkg/tui/views/psql_test.go
@@ -1,7 +1,10 @@
 package views
 
 import (
+	"bytes"
 	"encoding/json"
+	"os/exec"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -48,3 +51,69 @@ func TestPSQLResult_YAMLMarshal(t *testing.T) {
 	require.Contains(t, string(b), "output:")
 	require.Contains(t, string(b), "hello world")
 }
+
+func TestRunPSQLCommandForwardsSuccessfulDiagnostics(t *testing.T) {
+	if _, err := exec.LookPath("sh"); err != nil {
+		t.Skip("the subprocess fixture requires a POSIX shell")
+	}
+	tests := []struct {
+		name        string
+		script      string
+		output      string
+		diagnostics string
+		err         string
+	}{
+		{"stdout and warning", `printf 'DO\n'; printf 'WARNING:  careful\n' >&2`, "DO\n", "WARNING:  careful\n", ""},
+		{"notice only", `printf 'NOTICE:  fyi\n' >&2`, "", "NOTICE:  fyi\n", ""},
+		{"stdout only", `printf '1\n'`, "1\n", "", ""},
+		{"empty", `true`, "", "", ""},
+		{"error keeps stderr in the error", `printf 'ERROR:  boom\n' >&2; exit 3`, "", "", "exit status 3: ERROR:  boom"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var diagnostics bytes.Buffer
+			result, err := runPSQLCommand(exec.Command("sh", "-c", tt.script), nil, &diagnostics)
+			if tt.err != "" {
+				require.EqualError(t, err, tt.err)
+				require.Nil(t, result)
+			} else {
+				require.NoError(t, err)
+				require.Equal(t, tt.output, result.Output)
+			}
+			require.Equal(t, tt.diagnostics, diagnostics.String())
+		})
+	}
+}
+
+func TestRunPSQLCommandForwardsStdin(t *testing.T) {
+	if _, err := exec.LookPath("sh"); err != nil {
+		t.Skip("the subprocess fixture requires a POSIX shell")
+	}
+	csv := "id,body\n1,\"a, \"\"quoted\"\"\nline\"\n2,\"\u00e9\u6f22\"\n3,\"\"\n"
+	tests := []struct {
+		name   string
+		script string
+		stdin  string
+		output string
+		err    string
+	}{
+		{"exact bytes reach the child", `cat`, csv, csv, ""},
+		{"empty stdin", `cat`, "", "", ""},
+		{"a command that reads nothing", `printf 'SELECT 1\n'`, csv, "SELECT 1\n", ""},
+		{"child error keeps stderr in the error", `cat >/dev/null; printf 'ERROR:  bad input\n' >&2; exit 1`, csv, "", "exit status 1: ERROR:  bad input"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var diagnostics bytes.Buffer
+			result, err := runPSQLCommand(exec.Command("sh", "-c", tt.script), strings.NewReader(tt.stdin), &diagnostics)
+			if tt.err != "" {
+				require.EqualError(t, err, tt.err)
+				require.Nil(t, result)
+				return
+			}
+			require.NoError(t, err)
+			require.Equal(t, tt.output, result.Output)
+			require.Empty(t, diagnostics.String())
+		})
+	}
+}