feat(compose): add ResponseFormat type and WithResponseFormat model o…

components/model/option.go

@@ -42,6 +42,8 @@ type Options struct {
 	MaxTokens *int
 	// Stop is the stop words for the model, which controls the stopping condition of the model.
 	Stop []string
+	// ResponseFormat controls the structured output format of the model response.
+	ResponseFormat *schema.ResponseFormat
 
 	// Options only available for chat model.
 
@@ -173,6 +175,15 @@ func WithAgenticToolChoice(toolChoice *schema.AgenticToolChoice) Option {
 	}
 }
 
+// WithResponseFormat sets the response format for the model.
+func WithResponseFormat(rf *schema.ResponseFormat) Option {
+	return Option{
+		apply: func(opts *Options) {
+			opts.ResponseFormat = rf
+		},
+	}
+}
+
 // WrapImplSpecificOptFn is the option to wrap the implementation specific option function.
 // WrapImplSpecificOptFn wraps an implementation-specific option function into
 // an [Option] so it can be passed alongside standard options.

schema/response_format.go

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2026 CloudWeGo Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package schema
+
+import "github.com/eino-contrib/jsonschema"
+
+// ResponseFormatType specifies the format the model must output.
+type ResponseFormatType string
+
+const (
+	// ResponseFormatTypeJSONObject forces the model to output valid JSON.
+	ResponseFormatTypeJSONObject ResponseFormatType = "json_object"
+	// ResponseFormatTypeJSONSchema forces the model to output JSON conforming to a given schema.
+	ResponseFormatTypeJSONSchema ResponseFormatType = "json_schema"
+)
+
+// ResponseFormat controls the structured output format of the model response.
+type ResponseFormat struct {
+	// Type specifies the response format type.
+	Type ResponseFormatType
+	// JSONSchema specifies the schema when Type is ResponseFormatJSONSchema.
+	JSONSchema *ResponseFormatJSONSchema
+}
+
+// ResponseFormatJSONSchema defines the JSON Schema for structured output.
+type ResponseFormatJSONSchema struct {
+	// Schema is the JSON Schema definition.
+	Schema *jsonschema.Schema
+}