perf: optimize memory layout

api_client.go

@@ -464,14 +464,14 @@ func iterateResponseStream[R any](rs *responseStream[R], responseConverter func(
 
 // APIError contains an error response from the server.
 type APIError struct {
-	// Code is the HTTP response status code.
-	Code int `json:"code,omitempty"`
 	// Message is the server response message.
 	Message string `json:"message,omitempty"`
 	// Status is the server response status.
 	Status string `json:"status,omitempty"`
 	// Details field provides more context to an error.
 	Details []map[string]any `json:"details,omitempty"`
+	// Code is the HTTP response status code.
+	Code int `json:"code,omitempty"`
 }
 
 type responseWithError struct {

client.go

@@ -29,7 +29,6 @@ import (
 
 // Client is the GenAI client. It provides access to the various GenAI services.
 type Client struct {
-	clientConfig ClientConfig
 	// Models provides access to the Models service.
 	Models *Models
 	// Live provides access to the Live service.
@@ -47,7 +46,8 @@ type Client struct {
 	// Batches provides access to the Batch service.
 	Batches *Batches
 	// Tunings provides access to the Tunings service.
-	Tunings *Tunings
+	Tunings      *Tunings
+	clientConfig ClientConfig
 }
 
 // Backend is the GenAI backend to use for the client.
@@ -80,15 +80,27 @@ func (t Backend) String() string {
 
 // ClientConfig is the configuration for the GenAI client.
 type ClientConfig struct {
+
+	// Optional HTTP options to override.
+	HTTPOptions HTTPOptions
+
+	// Optional. Google credentials.  If not specified, [Application Default Credentials] will be used.
+	//
+	// [Application Default Credentials]: https://developers.google.com/accounts/docs/application-default-credentials
+	Credentials *auth.Credentials
+
+	// Optional HTTP client to use. If nil, a default client will be created.
+	// For Vertex AI, this client must handle authentication appropriately.
+	// Otherwise, call [UseDefaultCredentials] convenience method to add default credentials to the
+	// client.
+	HTTPClient *http.Client
+
+	envVarProvider func() map[string]string
 	// Optional. API Key for GenAI. Required for BackendGeminiAPI.
 	// Can also be set via the GOOGLE_API_KEY or GEMINI_API_KEY environment variable.
 	// Get a Gemini API key: https://ai.google.dev/gemini-api/docs/api-key
 	APIKey string
 
-	// Optional. Backend for GenAI. See Backend constants. Defaults to BackendGeminiAPI unless explicitly set to BackendVertexAI,
-	// or the environment variable GOOGLE_GENAI_USE_VERTEXAI is set to "1" or "true".
-	Backend Backend
-
 	// Optional. GCP Project ID for Vertex AI. Required for BackendVertexAI.
 	// Can also be set via the GOOGLE_CLOUD_PROJECT environment variable.
 	// Find your Project ID: https://cloud.google.com/resource-manager/docs/creating-managing-projects#identifying_projects
@@ -99,21 +111,9 @@ type ClientConfig struct {
 	// Generative AI locations: https://cloud.google.com/vertex-ai/generative-ai/docs/learn/locations.
 	Location string
 
-	// Optional. Google credentials.  If not specified, [Application Default Credentials] will be used.
-	//
-	// [Application Default Credentials]: https://developers.google.com/accounts/docs/application-default-credentials
-	Credentials *auth.Credentials
-
-	// Optional HTTP client to use. If nil, a default client will be created.
-	// For Vertex AI, this client must handle authentication appropriately.
-	// Otherwise, call [UseDefaultCredentials] convenience method to add default credentials to the
-	// client.
-	HTTPClient *http.Client
-
-	// Optional HTTP options to override.
-	HTTPOptions HTTPOptions
-
-	envVarProvider func() map[string]string
+	// Optional. Backend for GenAI. See Backend constants. Defaults to BackendGeminiAPI unless explicitly set to BackendVertexAI,
+	// or the environment variable GOOGLE_GENAI_USE_VERTEXAI is set to "1" or "true".
+	Backend Backend
 }
 
 func defaultEnvVarProvider() map[string]string {

pages.go

@@ -26,13 +26,13 @@ var ErrPageDone = errors.New("no more pages")
 // Page represents a page of results from a paginated API call.
 // It contains a slice of items and information about the next page.
 type Page[T any] struct {
-	Name            string        // The name of the resource.
-	Items           []*T          // The items in the current page.
-	NextPageToken   string        // The token to use to retrieve the next page of results.
 	SDKHTTPResponse *HTTPResponse // The SDKHTTPResponse from the API call.
 
-	config   map[string]any                                                                        // The configuration used for the API call.
-	listFunc func(ctx context.Context, config map[string]any) ([]*T, string, *HTTPResponse, error) // The function used to retrieve the next page.
+	config        map[string]any                                                                        // The configuration used for the API call.
+	listFunc      func(ctx context.Context, config map[string]any) ([]*T, string, *HTTPResponse, error) // The function used to retrieve the next page.
+	Name          string                                                                                // The name of the resource.
+	NextPageToken string                                                                                // The token to use to retrieve the next page of results.
+	Items         []*T                                                                                  // The items in the current page.
 }
 
 func newPage[T any](ctx context.Context, name string, config map[string]any, listFunc func(ctx context.Context, config map[string]any) ([]*T, string, *HTTPResponse, error)) (Page[T], error) {

replay_api_client.go

@@ -38,10 +38,10 @@ import (
 // ReplayAPIClient is a client that reads responses from a replay session file.
 type replayAPIClient struct {
 	ReplayFile              *replayFile
-	ReplaysDirectory        string
-	currentInteractionIndex int
 	t                       *testing.T
 	server                  *httptest.Server
+	ReplaysDirectory        string
+	currentInteractionIndex int
 }
 
 // NewReplayAPIClient creates a new ReplayAPIClient from a replay session file.