diff --git a/components/model/ark/go.mod b/components/model/ark/go.mod
index 3e136ee9c..a9f195ce0 100644
--- a/components/model/ark/go.mod
+++ b/components/model/ark/go.mod
@@ -49,3 +49,5 @@ require (
 	gopkg.in/yaml.v2 v2.2.8 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
+
+replace github.com/volcengine/volcengine-go-sdk => github.com/jesse-engineer/volcengine-go-sdk v1.2.26-0.20260428152021-d3ac2bef0584
diff --git a/components/model/ark/go.sum b/components/model/ark/go.sum
index 96f141149..7560c9f6f 100644
--- a/components/model/ark/go.sum
+++ b/components/model/ark/go.sum
@@ -66,6 +66,8 @@ github.com/goph/emperror v0.17.2/go.mod h1:+ZbQ+fUNO/6FNiUo0ujtMjhgad9Xa6fQL9KhH
 github.com/gopherjs/gopherjs v1.17.2 h1:fQnZVsXk8uxXIStYb0N4bGk7jeyTalG/wsZjQ25dO0g=
 github.com/gopherjs/gopherjs v1.17.2/go.mod h1:pRRIvn/QzFLrKfvEz3qUuEhtE/zLCWfreZ6J5gM2i+k=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
+github.com/jesse-engineer/volcengine-go-sdk v1.2.26-0.20260428152021-d3ac2bef0584 h1:hdi/IU3ATB4ZSmG1r15rJignySbT2c14PLQ9I2Adddc=
+github.com/jesse-engineer/volcengine-go-sdk v1.2.26-0.20260428152021-d3ac2bef0584/go.mod h1:oxoVo+A17kvkwPkIeIHPVLjSw7EQAm+l/Vau1YGHN+A=
 github.com/jmespath/go-jmespath v0.4.0 h1:BEgLn5cpjn8UN1mAw4NjwDrS35OdebyEtFe+9YPoQUg=
 github.com/jmespath/go-jmespath v0.4.0/go.mod h1:T8mJZnbsbmF+m6zOOFylbeCJqk5+pHWvzYPziyZiYoo=
 github.com/jmespath/go-jmespath/internal/testify v1.5.1 h1:shLQSRRSCCPj3f2gpwzGwWFoC7ycTf1rcQZHOlsJ6N8=
@@ -137,8 +139,6 @@ github.com/twitchyliquid64/golang-asm v0.15.1 h1:SU5vSMR7hnwNxj24w34ZyCi/FmDZTkS
 github.com/twitchyliquid64/golang-asm v0.15.1/go.mod h1:a1lVb/DtPvCB8fslRZhAngC2+aY1QWCk3Cedj/Gdt08=
 github.com/volcengine/volc-sdk-golang v1.0.23 h1:anOslb2Qp6ywnsbyq9jqR0ljuO63kg9PY+4OehIk5R8=
 github.com/volcengine/volc-sdk-golang v1.0.23/go.mod h1:AfG/PZRUkHJ9inETvbjNifTDgut25Wbkm2QoYBTbvyU=
-github.com/volcengine/volcengine-go-sdk v1.2.9 h1:du2gnImtyWXKkQFnJW/GXCs+UBibGGOXIbP1Ams2pB8=
-github.com/volcengine/volcengine-go-sdk v1.2.9/go.mod h1:oxoVo+A17kvkwPkIeIHPVLjSw7EQAm+l/Vau1YGHN+A=
 github.com/wk8/go-ordered-map/v2 v2.1.8 h1:5h/BUHu93oj4gIdvHHHGsScSTMijfx5PeYkE/fJgbpc=
 github.com/wk8/go-ordered-map/v2 v2.1.8/go.mod h1:5nJHM5DyteebpVlHnWMV0rPz6Zp7+xBAnxjb1X5vnTw=
 github.com/x-cray/logrus-prefixed-formatter v0.5.2 h1:00txxvfBM9muc0jiLIEAkAcIMJzfthRT6usrui8uGmg=
diff --git a/components/model/ark/option.go b/components/model/ark/option.go
index d112effb4..3a725eee6 100644
--- a/components/model/ark/option.go
+++ b/components/model/ark/option.go
@@ -35,6 +35,9 @@ type arkOptions struct {
 	maxToolCalls *int64
 
 	enableReasoningContentPassback bool
+
+	// extraFields are shallow-merged into serialized Responses API JSON after multimodal preprocessing.
+	extraFields map[string]any
 }
 
 // WithCustomHeader sets custom headers for a single request
@@ -153,3 +156,12 @@ func WithEnableReasoningContentPassback(enable bool) model.Option {
 		o.enableReasoningContentPassback = enable
 	})
 }
+
+// WithExtraFields sets extra top-level JSON fields on the Responses API request body.
+// Merged inside volcengine-go-sdk after the request is built and multimodal inputs are preprocessed;
+// keys in extraFields override existing keys. See arkruntime.WithResponsesExtraFields.
+func WithExtraFields(extraFields map[string]any) model.Option {
+	return model.WrapImplSpecificOptFn(func(o *arkOptions) {
+		o.extraFields = extraFields
+	})
+}
diff --git a/components/model/ark/option_test.go b/components/model/ark/option_test.go
index 0b11df7b7..7d5d0d168 100644
--- a/components/model/ark/option_test.go
+++ b/components/model/ark/option_test.go
@@ -46,3 +46,9 @@ func TestOptions(t *testing.T) {
 	assert.Equal(t, cacheOpt, *opt.cache)
 	assert.Equal(t, arkModel.ThinkingTypeEnabled, opt.thinking.Type)
 }
+
+func TestWithExtraFieldsOption(t *testing.T) {
+	fields := map[string]any{"k": "v"}
+	opt := model.GetImplSpecificOptions(&arkOptions{}, WithExtraFields(fields))
+	assert.Equal(t, fields, opt.extraFields)
+}
diff --git a/components/model/ark/responses_api.go b/components/model/ark/responses_api.go
index 2b9caf156..e5a0a0aa1 100644
--- a/components/model/ark/responses_api.go
+++ b/components/model/ark/responses_api.go
@@ -283,7 +283,7 @@ func (cm *ResponsesAPIChatModel) Generate(ctx context.Context, input []*schema.M
 		}
 	}()
 
-	responseObject, err := cm.client.CreateResponses(ctx, responseReq, arkruntime.WithCustomHeaders(specOptions.customHeaders))
+	responseObject, err := cm.invokeCreateResponses(ctx, responseReq, specOptions)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create responses: %w", err)
 	}
@@ -350,7 +350,7 @@ func (cm *ResponsesAPIChatModel) Stream(ctx context.Context, input []*schema.Mes
 		}
 	}()
 
-	responseStreamReader, err := cm.client.CreateResponsesStream(ctx, responseReq, arkruntime.WithCustomHeaders(specOptions.customHeaders))
+	responseStreamReader, err := cm.invokeCreateResponsesStream(ctx, responseReq, specOptions)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create responses: %w", err)
 	}
@@ -948,6 +948,33 @@ func (cm *ResponsesAPIChatModel) getOptions(opts []model.Option) (*model.Options
 	return options, arkOpts, nil
 }
 
+func extraFieldsToIface(m map[string]any) map[string]interface{} {
+	if len(m) == 0 {
+		return nil
+	}
+	out := make(map[string]interface{}, len(m))
+	for k, v := range m {
+		out[k] = v
+	}
+	return out
+}
+
+func (cm *ResponsesAPIChatModel) invokeCreateResponses(ctx context.Context, responseReq *responses.ResponsesRequest, spec *arkOptions) (*responses.ResponseObject, error) {
+	h := arkruntime.WithCustomHeaders(spec.customHeaders)
+	if len(spec.extraFields) == 0 {
+		return cm.client.CreateResponses(ctx, responseReq, h)
+	}
+	return cm.client.CreateResponses(ctx, responseReq, h, arkruntime.WithResponsesExtraFields(extraFieldsToIface(spec.extraFields)))
+}
+
+func (cm *ResponsesAPIChatModel) invokeCreateResponsesStream(ctx context.Context, responseReq *responses.ResponsesRequest, spec *arkOptions) (*utils.ResponsesStreamReader, error) {
+	h := arkruntime.WithCustomHeaders(spec.customHeaders)
+	if len(spec.extraFields) == 0 {
+		return cm.client.CreateResponsesStream(ctx, responseReq, h)
+	}
+	return cm.client.CreateResponsesStream(ctx, responseReq, h, arkruntime.WithResponsesExtraFields(extraFieldsToIface(spec.extraFields)))
+}
+
 func (cm *ResponsesAPIChatModel) toTools(tis []*schema.ToolInfo) ([]*responses.ResponsesTool, error) {
 	tools := make([]*responses.ResponsesTool, len(tis))
 	for i := range tis {
@@ -1712,7 +1739,7 @@ func (cm *ResponsesAPIChatModel) CreatePrefixCache(ctx context.Context, prefix [
 		return nil, err
 	}
 
-	responseObject, err := cm.client.CreateResponses(ctx, responseReq)
+	responseObject, err := cm.invokeCreateResponses(ctx, responseReq, specOptions)
 	if err != nil {
 		return nil, err
 	}