OpenAI: transform strict response schemas at request boundary

provider/openaiprovider/chat.go

@@ -246,10 +246,18 @@ func buildCompletionParams(model string, messages []*message.Message, opts []age
 		switch frmt.Kind {
 		case "json":
 			if schema := frmt.Schema; schema != nil {
+				wireSchema := schema
+				if frmt.Strict {
+					var err error
+					wireSchema, err = strictSchemaToMap(schema)
+					if err != nil {
+						return openai.ChatCompletionNewParams{}, fmt.Errorf("failed to convert response format schema (type %T) to JSON format: %w", schema, err)
+					}
+				}
 				params.ResponseFormat.OfJSONSchema = &shared.ResponseFormatJSONSchemaParam{
 					JSONSchema: shared.ResponseFormatJSONSchemaJSONSchemaParam{
 						Name:   frmt.Name,
-						Schema: schema,
+						Schema: wireSchema,
 					},
 				}
 				if desc := frmt.Description; desc != "" {

provider/openaiprovider/chat_test.go

@@ -14,6 +14,7 @@ import (
 	"time"
 
 	"github.com/microsoft/agent-framework-go/agent"
+	"github.com/microsoft/agent-framework-go/agent/format/jsonformat"
 	"github.com/microsoft/agent-framework-go/internal/agenttest"
 	"github.com/microsoft/agent-framework-go/internal/messagetest"
 	"github.com/microsoft/agent-framework-go/message"
@@ -109,6 +110,42 @@ func TestChatRequestIncludesAgentFrameworkUserAgent(t *testing.T) {
 	}
 }
 
+func TestChatResponseFormatSchemaConvertsJSONSchema(t *testing.T) {
+	type payload struct {
+		Name     string `json:"name"`
+		Nickname string `json:"nickname,omitempty"`
+	}
+	format, err := jsonformat.For[payload]()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	const input = `
+            {
+                "messages":[{"role":"user","content":"hello"}],
+                "model":"gpt-4o-mini",
+                "response_format":{"type":"json_schema","json_schema":{"name":"payload","schema":{"properties":{"name":{"type":"string"},"nickname":{"type":"string"}},"type":"object","required":["name","nickname"],"additionalProperties":false},"strict":true}}
+            }
+            `
+	const output = `
+            {
+                "id":"chatcmpl-test",
+                "object":"chat.completion",
+                "created":1727888631,
+                "model":"gpt-4o-mini",
+                "choices":[{"index":0,"message":{"role":"assistant","content":"{\"name\":\"Ada\",\"nickname\":\"A\"}"},"finish_reason":"stop"}]
+            }
+            `
+
+	server := newTestServer(t, input, output)
+	defer server.Close()
+
+	a := newTestClient(server)
+	if _, err := a.RunText(t.Context(), "hello", agent.WithResponseFormat(format)).Collect(); err != nil {
+		t.Fatalf("error = %v", err)
+	}
+}
+
 func TestChatConfigInstructions_NonStreaming(t *testing.T) {
 	const input = `
 						{

provider/openaiprovider/responses.go

@@ -262,7 +262,13 @@ func responsesBuildCompletionParams(config AgentConfig, messages []*message.Mess
 		switch frmt.Kind {
 		case "json":
 			if schema := frmt.Schema; schema != nil {
-				schemaMap, err := schemaToMap(schema)
+				var schemaMap map[string]any
+				var err error
+				if frmt.Strict {
+					schemaMap, err = strictSchemaToMap(schema)
+				} else {
+					schemaMap, err = schemaToMap(schema)
+				}
 				if err != nil {
 					return responses.ResponseNewParams{}, fmt.Errorf("failed to convert response format schema (type %T) to JSON format: %w", schema, err)
 				}

provider/openaiprovider/responses_test.go

@@ -2643,7 +2643,8 @@ data: {"type":"response.completed","sequence_number":2,"response":{"id":"resp_00
 
 func TestResponsesResponseFormatSchemaConvertsJSONSchema(t *testing.T) {
 	type payload struct {
-		Name string `json:"name"`
+		Name     string `json:"name"`
+		Nickname string `json:"nickname,omitempty"`
 	}
 	format, err := jsonformat.For[payload]()
 	if err != nil {
@@ -2654,7 +2655,7 @@ func TestResponsesResponseFormatSchemaConvertsJSONSchema(t *testing.T) {
             {
                 "model":"gpt-4o-mini",
                 "input":[{"type":"message","role":"user","content":[{"type":"input_text","text":"hello"}]}],
-                "text":{"format":{"type":"json_schema","name":"payload","schema":{"properties":{"name":{"type":"string"}},"type":"object","required":["name"],"additionalProperties":false},"strict":true}}
+				"text":{"format":{"type":"json_schema","name":"payload","schema":{"properties":{"name":{"type":"string"},"nickname":{"type":"string"}},"type":"object","required":["name","nickname"],"additionalProperties":false},"strict":true}}
             }
             `
 
@@ -2676,6 +2677,18 @@ func TestResponsesResponseFormatSchemaConvertsJSONSchema(t *testing.T) {
 	if _, err := a.RunText(t.Context(), "hello", agent.WithResponseFormat(format)).Collect(); err != nil {
 		t.Fatalf("error = %v", err)
 	}
+
+	localFormat, err := jsonformat.FromResponseFormat(format)
+	if err != nil {
+		t.Fatal(err)
+	}
+	data, err := localFormat.Marshal(payload{Name: "Ada"})
+	if err != nil {
+		t.Fatalf("local Marshal() rejected omitted optional property: %v", err)
+	}
+	if got, want := string(data), `{"name":"Ada"}`; got != want {
+		t.Fatalf("local Marshal() = %s, want %s", got, want)
+	}
 }
 
 func TestResponsesStreamingResponseWithQueuedUpdate_HandlesCorrectly(t *testing.T) {