Fix GraphQL forwarding path rewrite for github.com proxy requests

Agent-Logs-Url: https://github.com/github/gh-aw-mcpg/sessions/704c283d-fc05-4f02-bd25-3574eec4f332

Co-authored-by: lpcox <15877973+lpcox@users.noreply.github.com>

Author: Copilot

internal/proxy/handler_test.go

@@ -195,7 +195,7 @@ func TestServeHTTP_GraphQLPreservesQueryString(t *testing.T) {
 		wantPath string
 	}{
 		{name: "graphql path", path: "/graphql?foo=bar", wantPath: "/graphql?foo=bar"},
-		{name: "ghes api graphql path", path: "/api/graphql?foo=bar", wantPath: "/api/graphql?foo=bar"},
+		{name: "ghes api graphql path", path: "/api/graphql?foo=bar", wantPath: "/graphql?foo=bar"},
 		{name: "gh host prefixed graphql path", path: "/api/v3/graphql?foo=bar", wantPath: "/graphql?foo=bar"},
 	}
 

internal/proxy/proxy.go

@@ -344,8 +344,12 @@ func (r *restBackendCaller) CallTool(ctx context.Context, toolName string, args
 func (s *Server) forwardToGitHub(ctx context.Context, method, path string, body io.Reader, contentType string, clientAuth string) (*http.Response, error) {
 	url := s.githubAPIURL + path
 	pathOnly, query, hasQuery := strings.Cut(path, "?")
-	if strings.HasSuffix(s.githubAPIURL, "/api/v3") && IsGraphQLPath(pathOnly) {
-		url = strings.TrimSuffix(s.githubAPIURL, "/api/v3") + "/api/graphql"
+	if IsGraphQLPath(pathOnly) {
+		graphqlURL := s.githubAPIURL + "/graphql"
+		if strings.HasSuffix(s.githubAPIURL, "/api/v3") {
+			graphqlURL = strings.TrimSuffix(s.githubAPIURL, "/api/v3") + "/api/graphql"
+		}
+		url = graphqlURL
 		if hasQuery {
 			url += "?" + query
 		}

internal/proxy/proxy_test.go

@@ -887,3 +887,46 @@ func TestForwardToGitHub_RewritesGraphQLPathForGHESAPIBase(t *testing.T) {
 		})
 	}
 }
+
+func TestForwardToGitHub_RewritesGraphQLPathForDotComAPIBase(t *testing.T) {
+	var receivedPath string
+	var receivedQuery string
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		receivedPath = r.URL.Path
+		receivedQuery = r.URL.RawQuery
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer upstream.Close()
+
+	s := &Server{
+		githubAPIURL: upstream.URL,
+		httpClient:   upstream.Client(),
+	}
+
+	tests := []struct {
+		name      string
+		path      string
+		wantPath  string
+		wantQuery string
+	}{
+		{name: "plain graphql endpoint", path: "/graphql", wantPath: "/graphql"},
+		{name: "ghes api graphql endpoint", path: "/api/graphql", wantPath: "/graphql"},
+		{name: "gh host prefixed graphql endpoint", path: "/api/v3/graphql", wantPath: "/graphql"},
+		{name: "graphql endpoint with query string", path: "/api/graphql?foo=bar", wantPath: "/graphql", wantQuery: "foo=bar"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			receivedPath = ""
+			receivedQuery = ""
+
+			resp, err := s.forwardToGitHub(context.Background(), http.MethodPost, tt.path, nil, "application/json", "")
+			require.NoError(t, err)
+			require.NotNil(t, resp)
+			defer resp.Body.Close()
+
+			assert.Equal(t, tt.wantPath, receivedPath)
+			assert.Equal(t, tt.wantQuery, receivedQuery)
+		})
+	}
+}