feat(openai): add WebSocket mode for Responses API

providers/openai/openai.go

@@ -29,6 +29,7 @@ type options struct {
 	project              string
 	name                 string
 	useResponsesAPI      bool
+	useWebSocket         bool
 	headers              map[string]string
 	client               option.HTTPClient
 	sdkOptions           []option.RequestOption
@@ -132,6 +133,15 @@ func WithUseResponsesAPI() Option {
 	}
 }
 
+// WithWebSocket enables WebSocket mode for the Responses API, providing lower-latency
+// persistent connections for tool-call-heavy workflows. Requires WithUseResponsesAPI().
+// Falls back to HTTP if the WebSocket connection cannot be established.
+func WithWebSocket() Option {
+	return func(o *options) {
+		o.useWebSocket = true
+	}
+}
+
 // WithObjectMode sets the object generation mode.
 func WithObjectMode(om fantasy.ObjectMode) Option {
 	return func(o *options) {
@@ -173,7 +183,11 @@ func (o *provider) LanguageModel(_ context.Context, modelID string) (fantasy.Lan
 		if objectMode == fantasy.ObjectModeJSON {
 			objectMode = fantasy.ObjectModeAuto
 		}
-		return newResponsesLanguageModel(modelID, o.options.name, client, objectMode), nil
+		var ws *wsTransport
+		if o.options.useWebSocket {
+			ws = newWSTransport(o.options.baseURL, o.options.apiKey, o.options.headers)
+		}
+		return newResponsesLanguageModel(modelID, o.options.name, client, objectMode, ws), nil
 	}
 
 	o.options.languageModelOptions = append(o.options.languageModelOptions, WithLanguageModelObjectMode(o.options.objectMode))

providers/openai/responses_language_model.go

@@ -21,20 +21,22 @@ import (
 const topLogprobsMax = 20
 
 type responsesLanguageModel struct {
-	provider   string
-	modelID    string
-	client     openai.Client
-	objectMode fantasy.ObjectMode
+	provider    string
+	modelID     string
+	client      openai.Client
+	objectMode  fantasy.ObjectMode
+	wsTransport *wsTransport
 }
 
 // newResponsesLanguageModel implements a responses api model
 // INFO: (kujtim) currently we do not support stored parameter we default it to false.
-func newResponsesLanguageModel(modelID string, provider string, client openai.Client, objectMode fantasy.ObjectMode) responsesLanguageModel {
+func newResponsesLanguageModel(modelID string, provider string, client openai.Client, objectMode fantasy.ObjectMode, ws *wsTransport) responsesLanguageModel {
 	return responsesLanguageModel{
-		modelID:    modelID,
-		provider:   provider,
-		client:     client,
-		objectMode: objectMode,
+		modelID:     modelID,
+		provider:    provider,
+		client:      client,
+		objectMode:  objectMode,
+		wsTransport: ws,
 	}
 }
 
@@ -228,6 +230,9 @@ func (o responsesLanguageModel) prepareParams(call fantasy.Call) (*responses.Res
 		if openaiOptions.SafetyIdentifier != nil {
 			params.SafetyIdentifier = param.NewOpt(*openaiOptions.SafetyIdentifier)
 		}
+		if openaiOptions.PreviousResponseID != nil {
+			params.PreviousResponseID = param.NewOpt(*openaiOptions.PreviousResponseID)
+		}
 		if topLogprobs > 0 {
 			params.TopLogprobs = param.NewOpt(int64(topLogprobs))
 		}
@@ -668,6 +673,15 @@ func toResponsesTools(tools []fantasy.Tool, toolChoice *fantasy.ToolChoice, opti
 
 func (o responsesLanguageModel) Generate(ctx context.Context, call fantasy.Call) (*fantasy.Response, error) {
 	params, warnings := o.prepareParams(call)
+
+	if o.wsTransport != nil {
+		resp, err := o.generateViaWebSocket(ctx, params, warnings, call)
+		if err == nil {
+			return resp, nil
+		}
+		// Fall back to HTTP on WebSocket failure
+	}
+
 	response, err := o.client.Responses.New(ctx, *params)
 	if err != nil {
 		return nil, toProviderErr(err)
@@ -806,6 +820,14 @@ func mapResponsesFinishReason(reason string, hasFunctionCall bool) fantasy.Finis
 func (o responsesLanguageModel) Stream(ctx context.Context, call fantasy.Call) (fantasy.StreamResponse, error) {
 	params, warnings := o.prepareParams(call)
 
+	if o.wsTransport != nil {
+		resp, err := o.streamViaWebSocket(ctx, params, warnings, call)
+		if err == nil {
+			return resp, nil
+		}
+		// Fall back to HTTP on WebSocket failure
+	}
+
 	stream := o.client.Responses.NewStreaming(ctx, *params)
 
 	finishReason := fantasy.FinishReasonUnknown

providers/openai/responses_options.go

@@ -97,20 +97,23 @@ const (
 
 // ResponsesProviderOptions represents additional options for OpenAI Responses API.
 type ResponsesProviderOptions struct {
-	Include           []IncludeType    `json:"include"`
-	Instructions      *string          `json:"instructions"`
-	Logprobs          any              `json:"logprobs"`
-	MaxToolCalls      *int64           `json:"max_tool_calls"`
-	Metadata          map[string]any   `json:"metadata"`
-	ParallelToolCalls *bool            `json:"parallel_tool_calls"`
-	PromptCacheKey    *string          `json:"prompt_cache_key"`
-	ReasoningEffort   *ReasoningEffort `json:"reasoning_effort"`
-	ReasoningSummary  *string          `json:"reasoning_summary"`
-	SafetyIdentifier  *string          `json:"safety_identifier"`
-	ServiceTier       *ServiceTier     `json:"service_tier"`
-	StrictJSONSchema  *bool            `json:"strict_json_schema"`
-	TextVerbosity     *TextVerbosity   `json:"text_verbosity"`
-	User              *string          `json:"user"`
+	Include            []IncludeType    `json:"include"`
+	Instructions       *string          `json:"instructions"`
+	Logprobs           any              `json:"logprobs"`
+	MaxToolCalls       *int64           `json:"max_tool_calls"`
+	Metadata           map[string]any   `json:"metadata"`
+	ParallelToolCalls  *bool            `json:"parallel_tool_calls"`
+	PreviousResponseID *string          `json:"previous_response_id"`
+	PromptCacheKey     *string          `json:"prompt_cache_key"`
+	ReasoningEffort    *ReasoningEffort `json:"reasoning_effort"`
+	ReasoningSummary   *string          `json:"reasoning_summary"`
+	ResetChain         *bool            `json:"reset_chain"`
+	SafetyIdentifier   *string          `json:"safety_identifier"`
+	ServiceTier        *ServiceTier     `json:"service_tier"`
+	StrictJSONSchema   *bool            `json:"strict_json_schema"`
+	TextVerbosity      *TextVerbosity   `json:"text_verbosity"`
+	User               *string          `json:"user"`
+	GenerateWarmup     *bool            `json:"generate_warmup"`
 }
 
 // Options implements the ProviderOptions interface.