diff --git a/core/http/endpoints/openresponses/responses.go b/core/http/endpoints/openresponses/responses.go
index 09f3b82e8..28eb6433a 100644
--- a/core/http/endpoints/openresponses/responses.go
+++ b/core/http/endpoints/openresponses/responses.go
@@ -1332,6 +1332,7 @@ func handleBackgroundStream(ctx context.Context, store *ResponseStore, responseI
 
 // bufferEvent stores an SSE event in the response store for streaming resume
 func bufferEvent(store *ResponseStore, responseID string, event *schema.ORStreamEvent) {
+	normalizeORStreamEvent(event)
 	if err := store.AppendEvent(responseID, event); err != nil {
 		xlog.Error("Failed to buffer event", "response_id", responseID, "error", err)
 	}
@@ -2605,6 +2606,7 @@ func handleOpenResponsesStream(c echo.Context, responseID string, createdAt int6
 
 // sendSSEEvent sends a Server-Sent Event
 func sendSSEEvent(c echo.Context, event *schema.ORStreamEvent) {
+	normalizeORStreamEvent(event)
 	data, err := json.Marshal(event)
 	if err != nil {
 		xlog.Error("Failed to marshal SSE event", "error", err)
@@ -2613,6 +2615,13 @@ func sendSSEEvent(c echo.Context, event *schema.ORStreamEvent) {
 	fmt.Fprintf(c.Response().Writer, "event: %s\ndata: %s\n\n", event.Type, string(data))
 }
 
+// normalizeORStreamEvent ensures required fields like Summary are never null.
+func normalizeORStreamEvent(event *schema.ORStreamEvent) {
+	if event.Item != nil && event.Item.Summary == nil {
+		event.Item.Summary = []schema.ORContentPart{}
+	}
+}
+
 // getTopLogprobs returns the top_logprobs value, defaulting to 0 if nil
 func getTopLogprobs(topLogprobs *int) int {
 	if topLogprobs != nil {
@@ -2693,6 +2702,13 @@ func buildORResponse(responseID string, createdAt int64, completedAt *int64, sta
 		outputItems = []schema.ORItemField{}
 	}
 
+	// Ensure Summary is never null on any output item
+	for i := range outputItems {
+		if outputItems[i].Summary == nil {
+			outputItems[i].Summary = []schema.ORContentPart{}
+		}
+	}
+
 	// Ensure tools is never null - always an array
 	tools := input.Tools
 	if tools == nil {
diff --git a/core/schema/openresponses.go b/core/schema/openresponses.go
index be010f030..09f8360bd 100644
--- a/core/schema/openresponses.go
+++ b/core/schema/openresponses.go
@@ -86,7 +86,7 @@ type ORReasoningParam struct {
 // ORItemParam represents an input/output item (discriminated union by type)
 type ORItemParam struct {
 	Type   string `json:"type"`             // message|function_call|function_call_output|reasoning|item_reference
-	ID     string `json:"id,omitempty"`     // Present for all output items
+	ID     string `json:"id"`               // Present for all output items
 	Status string `json:"status,omitempty"` // in_progress|completed|incomplete
 
 	// Message fields
@@ -102,8 +102,8 @@ type ORItemParam struct {
 	Output interface{} `json:"output,omitempty"` // string or []ORContentPart
 
 	// Reasoning fields (for type == "reasoning")
-	Summary         []ORContentPart `json:"summary,omitempty"`          // Array of summary parts
-	EncryptedContent *string        `json:"encrypted_content,omitempty"` // Provider-specific encrypted content
+	Summary          []ORContentPart `json:"summary"`                     // Array of summary parts
+	EncryptedContent *string         `json:"encrypted_content,omitempty"` // Provider-specific encrypted content
 
 	// Note: For item_reference type, use the ID field above to reference the item
 	// Note: For reasoning type, Content field (from message fields) contains the raw reasoning content