diff --git a/pkg/providers/anthropic_messages/provider.go b/pkg/providers/anthropic_messages/provider.go
index 6a1c473dd..39b274ff2 100644
--- a/pkg/providers/anthropic_messages/provider.go
+++ b/pkg/providers/anthropic_messages/provider.go
@@ -162,7 +162,7 @@ func buildRequestBody(
 	}
 
 	result := map[string]any{
-		"model":      model,
+		"model":      strings.ReplaceAll(model, ".", "-"),
 		"max_tokens": int64(maxTokens),
 		"messages":   []any{},
 	}
diff --git a/pkg/providers/anthropic_messages/provider_test.go b/pkg/providers/anthropic_messages/provider_test.go
index 39bc48117..4c7b19568 100644
--- a/pkg/providers/anthropic_messages/provider_test.go
+++ b/pkg/providers/anthropic_messages/provider_test.go
@@ -117,6 +117,26 @@ func TestBuildRequestBody(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "normalizes dotted anthropic model ID",
+			messages: []Message{
+				{Role: "user", Content: "Hello"},
+			},
+			model: "claude-sonnet-4.6",
+			options: map[string]any{
+				"max_tokens": 8192,
+			},
+			want: map[string]any{
+				"model":      "claude-sonnet-4-6",
+				"max_tokens": int64(8192),
+				"messages": []any{
+					map[string]any{
+						"role":    "user",
+						"content": "Hello",
+					},
+				},
+			},
+		},
 		{
 			name: "missing max_tokens returns error",
 			messages: []Message{
diff --git a/pkg/providers/factory_provider.go b/pkg/providers/factory_provider.go
index 962e6ae19..7b249c315 100644
--- a/pkg/providers/factory_provider.go
+++ b/pkg/providers/factory_provider.go
@@ -218,6 +218,7 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 		if cfg.APIKey() == "" {
 			return nil, "", fmt.Errorf("api_key is required for anthropic protocol (model: %s)", cfg.Model)
 		}
+		modelID = strings.ReplaceAll(modelID, ".", "-")
 		return NewHTTPProviderWithMaxTokensFieldAndRequestTimeout(
 			cfg.APIKey(),
 			apiBase,
diff --git a/pkg/providers/factory_provider_test.go b/pkg/providers/factory_provider_test.go
index f1fe02cc2..6e271d4a6 100644
--- a/pkg/providers/factory_provider_test.go
+++ b/pkg/providers/factory_provider_test.go
@@ -282,7 +282,7 @@ func TestGetDefaultAPIBase_Mimo(t *testing.T) {
 	}
 }
 
-func TestCreateProviderFromConfig_Anthropic(t *testing.T) {
+func TestCreateProviderFromConfig_AnthropicAPIKeyNormalizesDottedModelID(t *testing.T) {
 	cfg := &config.ModelConfig{
 		ModelName: "test-anthropic",
 		Model:     "anthropic/claude-sonnet-4.6",
@@ -296,8 +296,8 @@ 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")
 	}
 }