fix: use relative paths in GraphiQL to support multiple domains

Without this patch, GraphiQL endpoints were configured with absolute
URLs constructed from ExternalBaseURL. This caused GraphiQL to fail
when the service was accessed through a different domain (e.g., via
proxy, load balancer, or alternate hostname) because it would always
try to connect to the configured base URL rather than the domain the
user was actually using.

This is a problem because it prevents GraphiQL from working in
multi-domain deployments and makes local development harder when
accessing the service through different hostnames.

This patch solves the problem by changing GraphiQLConfig to accept
relative paths (EndpointPath and SubscriptionPath) instead of absolute
URLs. The GraphiQL HTML template now uses JavaScript to dynamically
construct the full URLs from window.location at runtime, ensuring the
page always connects to the correct domain. The WebSocket protocol is
also derived dynamically (ws: for http:, wss: for https:).

Changes:
- Replace Endpoint/SubscriptionEndpoint with EndpointPath/SubscriptionPath
- Use window.location.origin to build full GraphQL URL at runtime
- Derive WebSocket protocol from page protocol dynamically
- Update tests to verify path-based configuration

Co-authored-by: Claude Code <claude-code@noreply.anthropic.com>

Author: aspiers

cmd/hypergoat/main.go

@@ -431,9 +431,9 @@ func setupAdmin(r *chi.Mux, cfg *config.Config, svc *services) *admin.Handler {
 
 	// GraphiQL playgrounds
 	r.Get("/graphiql", server.HandleGraphiQL(server.GraphiQLConfig{
-		Endpoint:             cfg.ExternalBaseURL + "/graphql",
-		SubscriptionEndpoint: strings.Replace(cfg.ExternalBaseURL, "http", "ws", 1) + "/graphql/ws",
-		Title:                "Hypergoat GraphQL",
+		EndpointPath:     "/graphql",
+		SubscriptionPath: "/graphql/ws",
+		Title:            "Hypergoat GraphQL",
 		DefaultQuery: `# Hypergoat GraphQL API
 # 
 # Explore the AT Protocol data indexed by this AppView.
@@ -451,8 +451,8 @@ func setupAdmin(r *chi.Mux, cfg *config.Config, svc *services) *admin.Handler {
 	}))
 
 	r.Get("/graphiql/admin", server.HandleGraphiQL(server.GraphiQLConfig{
-		Endpoint: cfg.ExternalBaseURL + "/admin/graphql",
-		Title:    "Hypergoat Admin",
+		EndpointPath: "/admin/graphql",
+		Title:        "Hypergoat Admin",
 		DefaultQuery: `# Hypergoat Admin API
 #
 # Administrative operations for managing the AppView.

internal/server/graphiql.go

@@ -9,10 +9,11 @@ import (
 
 // GraphiQLConfig contains configuration for the GraphiQL handler.
 type GraphiQLConfig struct {
-	// Endpoint is the GraphQL endpoint URL.
-	Endpoint string
-	// SubscriptionEndpoint is the WebSocket endpoint for subscriptions (optional).
-	SubscriptionEndpoint string
+	// EndpointPath is the path to the GraphQL endpoint (e.g. "/graphql").
+	// The full URL is derived at runtime from the browser's window.location.
+	EndpointPath string
+	// SubscriptionPath is the path for WebSocket subscriptions (optional, e.g. "/graphql/ws").
+	SubscriptionPath string
 	// Title is the page title.
 	Title string
 	// DefaultQuery is the initial query to display.
@@ -71,22 +72,14 @@ func generateGraphiQLHTML(cfg GraphiQLConfig) string {
 `
 	}
 
-	// Build fetcher config
-	fetcherConfig := `{
-      url: '` + cfg.Endpoint + `',
-      headers: {
-        'Content-Type': 'application/json',
-      },
-    }`
-
-	if cfg.SubscriptionEndpoint != "" {
-		fetcherConfig = `{
-      url: '` + cfg.Endpoint + `',
-      headers: {
-        'Content-Type': 'application/json',
-      },
-      subscriptionUrl: '` + cfg.SubscriptionEndpoint + `',
-    }`
+	// Build subscription URL JavaScript snippet.
+	// Uses window.location to derive the correct WebSocket URL at runtime,
+	// so the page works regardless of which domain it's accessed through.
+	subscriptionJS := ""
+	if cfg.SubscriptionPath != "" {
+		subscriptionJS = `
+      const wsProto = location.protocol === 'https:' ? 'wss:' : 'ws:';
+      fetcherOpts.subscriptionUrl = wsProto + '//' + location.host + '` + cfg.SubscriptionPath + `';`
 	}
 
 	return `<!DOCTYPE html>
@@ -114,8 +107,12 @@ func generateGraphiQLHTML(cfg GraphiQLConfig) string {
   <script crossorigin src="https://unpkg.com/react-dom@18/umd/react-dom.production.min.js"></script>
   <script crossorigin src="https://unpkg.com/graphiql@3/graphiql.min.js"></script>
   <script>
+    const fetcherOpts = {
+      url: location.origin + '` + cfg.EndpointPath + `',
+      headers: { 'Content-Type': 'application/json' },
+    };` + subscriptionJS + `
     const root = ReactDOM.createRoot(document.getElementById('graphiql'));
-    const fetcher = GraphiQL.createFetcher(` + fetcherConfig + `);
+    const fetcher = GraphiQL.createFetcher(fetcherOpts);
     root.render(
       React.createElement(GraphiQL, {
         fetcher: fetcher,

internal/server/handlers_test.go

@@ -314,8 +314,8 @@ func TestHandleClientMetadata(t *testing.T) {
 
 func TestHandleGraphiQL(t *testing.T) {
 	baseCfg := GraphiQLConfig{
-		Endpoint: "/graphql",
-		Title:    "Hypergoat GraphiQL",
+		EndpointPath: "/graphql",
+		Title:        "Hypergoat GraphiQL",
 	}
 
 	t.Run("GET returns 200 with text/html content type", func(t *testing.T) {
@@ -363,9 +363,9 @@ func TestHandleGraphiQL(t *testing.T) {
 
 	t.Run("subscription endpoint included when configured", func(t *testing.T) {
 		cfg := GraphiQLConfig{
-			Endpoint:             "/graphql",
-			SubscriptionEndpoint: "ws://localhost:8080/graphql/ws",
-			Title:                "Test",
+			EndpointPath:     "/graphql",
+			SubscriptionPath: "/graphql/ws",
+			Title:            "Test",
 		}
 		handler := HandleGraphiQL(cfg)
 		req := httptest.NewRequest(http.MethodGet, "/graphiql", nil)
@@ -374,8 +374,8 @@ func TestHandleGraphiQL(t *testing.T) {
 		handler.ServeHTTP(rec, req)
 
 		body := rec.Body.String()
-		if !strings.Contains(body, "ws://localhost:8080/graphql/ws") {
-			t.Error("response body does not contain subscription endpoint")
+		if !strings.Contains(body, "/graphql/ws") {
+			t.Error("response body does not contain subscription path")
 		}
 		if !strings.Contains(body, "subscriptionUrl") {
 			t.Error("response body does not contain subscriptionUrl config key")
@@ -409,7 +409,7 @@ func TestHandleGraphiQL(t *testing.T) {
 
 	t.Run("default title used when not configured", func(t *testing.T) {
 		cfg := GraphiQLConfig{
-			Endpoint: "/graphql",
+			EndpointPath: "/graphql",
 		}
 		handler := HandleGraphiQL(cfg)
 		req := httptest.NewRequest(http.MethodGet, "/graphiql", nil)