feat: add structured X-Client-Info header

client.go

@@ -60,6 +60,8 @@ func NewClient(url, key string, options *ClientOptions) (*Client, error) {
 		}
 	}
 
+	applyXClientInfoHeader(headers)
+
 	client := &Client{}
 	client.options.url = url
 	// map is pass by reference, so this gets updated by rest of function

client_info.go

@@ -0,0 +1,45 @@
+package supabase
+
+import (
+	"fmt"
+	"runtime"
+	"strings"
+)
+
+const (
+	clientInfoHeader = "X-Client-Info"
+	// Version is the supabase-go library version sent in X-Client-Info.
+	Version = "0.0.5"
+)
+
+func buildXClientInfo() string {
+	parts := []string{fmt.Sprintf("supabase-go/%s", Version)}
+
+	if platform := runtime.GOOS; platform != "" {
+		parts = append(parts, "platform="+platform)
+	}
+
+	parts = append(parts, "runtime=go")
+
+	if v := strings.TrimPrefix(runtime.Version(), "go"); v != "" {
+		parts = append(parts, "runtime-version="+v)
+	}
+
+	return strings.Join(parts, "; ")
+}
+
+func applyXClientInfoHeader(headers map[string]string) {
+	if hasClientInfoHeader(headers) {
+		return
+	}
+	headers[clientInfoHeader] = buildXClientInfo()
+}
+
+func hasClientInfoHeader(headers map[string]string) bool {
+	for k := range headers {
+		if strings.EqualFold(k, clientInfoHeader) {
+			return true
+		}
+	}
+	return false
+}

client_info_test.go

@@ -0,0 +1,57 @@
+package supabase
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestBuildXClientInfo(t *testing.T) {
+	info := buildXClientInfo()
+
+	if !strings.HasPrefix(info, "supabase-go/"+Version) {
+		t.Fatalf("expected library token supabase-go/%s, got %q", Version, info)
+	}
+
+	required := []string{"platform=", "runtime=go", "runtime-version="}
+	for _, fragment := range required {
+		if !strings.Contains(info, fragment) {
+			t.Errorf("expected %q in X-Client-Info, got %q", fragment, info)
+		}
+	}
+}
+
+func TestApplyXClientInfoHeaderSetsDefault(t *testing.T) {
+	headers := map[string]string{}
+	applyXClientInfoHeader(headers)
+
+	got := headers[clientInfoHeader]
+	if got == "" {
+		t.Fatal("expected X-Client-Info to be set")
+	}
+	if !strings.HasPrefix(got, "supabase-go/") {
+		t.Fatalf("unexpected header value: %q", got)
+	}
+}
+
+func TestApplyXClientInfoHeaderPreservesUserValue(t *testing.T) {
+	custom := "my-app/1.0; platform=edge"
+	headers := map[string]string{clientInfoHeader: custom}
+	applyXClientInfoHeader(headers)
+
+	if headers[clientInfoHeader] != custom {
+		t.Fatalf("expected user header to be preserved, got %q", headers[clientInfoHeader])
+	}
+}
+
+func TestApplyXClientInfoHeaderPreservesUserValueCaseInsensitive(t *testing.T) {
+	custom := "my-app/1.0"
+	headers := map[string]string{"x-client-info": custom}
+	applyXClientInfoHeader(headers)
+
+	if headers["x-client-info"] != custom {
+		t.Fatalf("expected user header to be preserved, got %q", headers["x-client-info"])
+	}
+	if _, ok := headers[clientInfoHeader]; ok {
+		t.Fatal("expected canonical header key not to be added when user header exists")
+	}
+}