anthropicllm: Allow env var ANTHROPIC_MODEL for setting Claude model

llms/anthropic/anthropicllm.go

@@ -49,6 +49,7 @@ func New(opts ...Option) (*LLM, error) {
 func newClient(opts ...Option) (*anthropicclient.Client, error) {
 	options := &options{
 		token:      os.Getenv(tokenEnvVarName),
+		model:      os.Getenv(modelEnvVarName),
 		baseURL:    anthropicclient.DefaultBaseURL,
 		httpClient: http.DefaultClient,
 	}

llms/anthropic/anthropicllm_option.go

@@ -6,6 +6,7 @@ import (
 
 const (
 	tokenEnvVarName = "ANTHROPIC_API_KEY" //nolint:gosec
+	modelEnvVarName = "ANTHROPIC_MODEL"   //nolint:gosec
 )
 
 // MaxTokensAnthropicSonnet35 is the header value for specifying the maximum number of tokens
@@ -34,7 +35,9 @@ func WithToken(token string) Option {
 	}
 }
 
-// WithModel passes the Anthropic model to the client.
+// WithModel passes the Anthropic model to the client. If not set, the model
+// is read from the ANTHROPIC_MODEL environment variable. If that is not set,
+// `defaultModel` in the anthropicclient package is used.
 func WithModel(model string) Option {
 	return func(opts *options) {
 		opts.model = model

llms/anthropic/internal/anthropicclient/anthropicclient.go

@@ -22,8 +22,8 @@ var ErrEmptyResponse = errors.New("empty response")
 // Client is a client for the Anthropic API.
 type Client struct {
 	token   string
-	Model   string
 	baseURL string
+	model   string
 
 	httpClient Doer
 
@@ -69,9 +69,9 @@ func WithAnthropicBetaHeader(val string) Option {
 // New returns a new Anthropic client.
 func New(token string, model string, baseURL string, opts ...Option) (*Client, error) {
 	c := &Client{
-		Model:   model,
 		token:   token,
 		baseURL: strings.TrimSuffix(baseURL, "/"),
+		model:   model,
 	}
 
 	for _, opt := range opts {

llms/anthropic/internal/anthropicclient/completions.go

@@ -46,8 +46,8 @@ func (c *Client) setCompletionDefaults(payload *completionPayload) {
 	case payload.Model != "":
 
 	// If no model is set in the payload, take the one specified in the client.
-	case c.Model != "":
-		payload.Model = c.Model
+	case c.model != "":
+		payload.Model = c.model
 	// Fallback: use the default model
 	default:
 		payload.Model = defaultModel

llms/anthropic/internal/anthropicclient/messages.go

@@ -157,8 +157,8 @@ func (c *Client) setMessageDefaults(payload *messagePayload) {
 	case payload.Model != "":
 
 	// If no model is set in the payload, take the one specified in the client.
-	case c.Model != "":
-		payload.Model = c.Model
+	case c.model != "":
+		payload.Model = c.model
 	// Fallback: use the default model
 	default:
 		payload.Model = defaultModel