diff --git a/pkg/providers/anthropic_messages/provider.go b/pkg/providers/anthropic_messages/provider.go
index 8a83a7058..e4afb853b 100644
--- a/pkg/providers/anthropic_messages/provider.go
+++ b/pkg/providers/anthropic_messages/provider.go
@@ -161,8 +161,11 @@ func buildRequestBody(
 		return nil, fmt.Errorf("max_tokens is required in options")
 	}
 
+	// Normalize model ID: Anthropic API uses hyphens (claude-sonnet-4-6),
+	// but config may use dots (claude-sonnet-4.6).
+	apiModel := strings.ReplaceAll(model, ".", "-")
 	result := map[string]any{
-		"model":      model,
+		"model":      apiModel,
 		"max_tokens": int64(maxTokens),
 		"messages":   []any{},
 	}
diff --git a/pkg/providers/factory_provider.go b/pkg/providers/factory_provider.go
index b7567f9fc..05cf87b26 100644
--- a/pkg/providers/factory_provider.go
+++ b/pkg/providers/factory_provider.go
@@ -134,6 +134,9 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 		), modelID, nil
 
 	case "anthropic":
+		// Normalize model ID: Anthropic API uses hyphens (claude-sonnet-4-6),
+		// but config may use dots (claude-sonnet-4.6).
+		modelID = strings.ReplaceAll(modelID, ".", "-")
 		if cfg.AuthMethod == "oauth" || cfg.AuthMethod == "token" {
 			// Use OAuth credentials from auth store
 			provider, err := createClaudeAuthProvider()
diff --git a/pkg/providers/factory_provider_test.go b/pkg/providers/factory_provider_test.go
index b678a7eb6..2771eda98 100644
--- a/pkg/providers/factory_provider_test.go
+++ b/pkg/providers/factory_provider_test.go
@@ -236,8 +236,8 @@ func TestCreateProviderFromConfig_Anthropic(t *testing.T) {
 	if provider == nil {
 		t.Fatal("CreateProviderFromConfig() returned nil provider")
 	}
-	if modelID != "claude-sonnet-4.6" {
-		t.Errorf("modelID = %q, want %q", modelID, "claude-sonnet-4.6")
+	if modelID != "claude-sonnet-4-6" {
+		t.Errorf("modelID = %q, want %q", modelID, "claude-sonnet-4-6")
 	}
 }