feat(executor): promote additional_tools to top-level tools in XAI requests

- Added `promoteXAIAdditionalTools` to normalize and migrate `additional_tools` to the top-level `tools` array in XAI request bodies.
- Updated test cases to validate the promotion logic and ensure unsupported `additional_tools` items are excluded from input payloads.

Closes: #4434

internal/runtime/executor/xai_executor.go

@@ -915,6 +915,7 @@ func (e *XAIExecutor) prepareResponsesRequestTo(ctx context.Context, req cliprox
 	// the post-restore (namespace, short-name) shape used by the response filter.
 	clientDeclaredTools := collectXAIClientDeclaredToolKeys(body)
 	body = normalizeXAITools(body)
+	body = promoteXAIAdditionalTools(body)
 	// Drop choices that point at tools removed by normalizeXAITools before we
 	// inject native x_search, so a surviving allowed_tools / forced choice is not
 	// left pointing at a deleted tool once only x_search remains.
@@ -1537,6 +1538,64 @@ func normalizeXAITools(body []byte) []byte {
 	return body
 }
 
+// promoteXAIAdditionalTools moves Responses Lite tool declarations to the
+// top-level tools array because xAI does not accept additional_tools input items.
+func promoteXAIAdditionalTools(body []byte) []byte {
+	if !gjson.ValidBytes(body) {
+		return body
+	}
+	input := gjson.GetBytes(body, "input")
+	if !input.IsArray() {
+		return body
+	}
+
+	inputItems := input.Array()
+	remainingInput := make([]json.RawMessage, 0, len(inputItems))
+	promotedTools := make([]json.RawMessage, 0)
+	for _, item := range inputItems {
+		if item.Get("type").String() != "additional_tools" {
+			remainingInput = append(remainingInput, json.RawMessage(item.Raw))
+			continue
+		}
+		for _, tool := range item.Get("tools").Array() {
+			promotedTools = append(promotedTools, json.RawMessage(tool.Raw))
+		}
+	}
+	if len(remainingInput) == len(inputItems) {
+		return body
+	}
+
+	rawInput, errMarshalInput := json.Marshal(remainingInput)
+	if errMarshalInput != nil {
+		return body
+	}
+	updated, errSetInput := sjson.SetRawBytes(body, "input", rawInput)
+	if errSetInput != nil {
+		return body
+	}
+	if len(promotedTools) == 0 {
+		return updated
+	}
+
+	topLevelTools := gjson.GetBytes(updated, "tools")
+	tools := make([]json.RawMessage, 0, len(topLevelTools.Array())+len(promotedTools))
+	if topLevelTools.IsArray() {
+		for _, tool := range topLevelTools.Array() {
+			tools = append(tools, json.RawMessage(tool.Raw))
+		}
+	}
+	tools = append(tools, promotedTools...)
+	rawTools, errMarshalTools := json.Marshal(tools)
+	if errMarshalTools != nil {
+		return body
+	}
+	updated, errSetTools := sjson.SetRawBytes(updated, "tools", rawTools)
+	if errSetTools != nil {
+		return body
+	}
+	return updated
+}
+
 func normalizeXAIToolArray(tools gjson.Result) ([]byte, bool, bool) {
 	changed := false
 	filtered := []byte(`[]`)

internal/runtime/executor/xai_executor_test.go

@@ -253,15 +253,23 @@ func TestXAIExecutorExecuteRestoresAdditionalToolsNamespaceCalls(t *testing.T) {
 		t.Fatalf("Execute() error = %v", err)
 	}
 
-	tool := gjson.GetBytes(gotBody, "input.0.tools.0")
+	for _, item := range gjson.GetBytes(gotBody, "input").Array() {
+		if got := item.Get("type").String(); got == "additional_tools" {
+			t.Fatalf("upstream input contains unsupported additional_tools item: %s", gotBody)
+		}
+	}
+	if got := gjson.GetBytes(gotBody, "input.0.role").String(); got != "user" {
+		t.Fatalf("input.0.role = %q, want user; body=%s", got, gotBody)
+	}
+	tool := gjson.GetBytes(gotBody, "tools.0")
 	if got := tool.Get("name").String(); got != "mcp__exa__web_search_exa" {
-		t.Fatalf("upstream additional tool name = %q, want qualified name; body=%s", got, gotBody)
+		t.Fatalf("upstream tool name = %q, want qualified name; body=%s", got, gotBody)
 	}
 	if got := tool.Get("type").String(); got != "function" {
-		t.Fatalf("upstream additional tool type = %q, want function; body=%s", got, gotBody)
+		t.Fatalf("upstream tool type = %q, want function; body=%s", got, gotBody)
 	}
 	if tool.Get("tools").Exists() {
-		t.Fatalf("upstream additional tool should not contain namespace children: %s", gotBody)
+		t.Fatalf("upstream tool should not contain namespace children: %s", gotBody)
 	}
 	output := gjson.GetBytes(resp.Payload, "output.0")
 	if got := output.Get("name").String(); got != "web_search_exa" {
@@ -2907,24 +2915,39 @@ func TestNormalizeXAITools_QualifiesSameNamedNamespaceTools(t *testing.T) {
 	}
 }
 
-func TestNormalizeXAITools_AdditionalToolsNamespace(t *testing.T) {
+func TestPromoteXAIAdditionalTools(t *testing.T) {
 	body := []byte(`{
+		"tools":[{"type":"function","name":"lookup","parameters":{"type":"object"}}],
 		"input":[
 			{"type":"additional_tools","role":"developer","tools":[{"type":"namespace","name":"mcp__exa","tools":[{"type":"function","name":"search","parameters":{"type":"object"}}]}]},
-			{"role":"user","content":"hello"}
+			{"role":"user","content":"hello"},
+			{"type":"additional_tools","role":"developer","tools":[{"type":"custom","name":"custom_lookup"}]}
 		]
 	}`)
-	out := normalizeXAITools(body)
+	out := promoteXAIAdditionalTools(normalizeXAITools(body))
 
-	tools := gjson.GetBytes(out, "input.0.tools").Array()
-	if len(tools) != 1 {
-		t.Fatalf("additional tools length = %d, want 1; body=%s", len(tools), string(out))
+	input := gjson.GetBytes(out, "input").Array()
+	if len(input) != 1 || input[0].Get("role").String() != "user" {
+		t.Fatalf("input should contain only the user message: %s", string(out))
 	}
-	if got := tools[0].Get("name").String(); got != "mcp__exa__search" {
-		t.Fatalf("additional tool name = %q, want mcp__exa__search; body=%s", got, string(out))
+	tools := gjson.GetBytes(out, "tools").Array()
+	if len(tools) != 3 {
+		t.Fatalf("tools length = %d, want 3; body=%s", len(tools), string(out))
 	}
-	if got := tools[0].Get("type").String(); got != "function" {
-		t.Fatalf("additional tool type = %q, want function; body=%s", got, string(out))
+	if got := tools[0].Get("name").String(); got != "lookup" {
+		t.Fatalf("tools.0.name = %q, want lookup; body=%s", got, string(out))
+	}
+	if got := tools[1].Get("name").String(); got != "mcp__exa__search" {
+		t.Fatalf("tools.1.name = %q, want mcp__exa__search; body=%s", got, string(out))
+	}
+	if got := tools[2].Get("name").String(); got != "custom_lookup" {
+		t.Fatalf("tools.2.name = %q, want custom_lookup; body=%s", got, string(out))
+	}
+	if got := tools[2].Get("type").String(); got != "function" {
+		t.Fatalf("tools.2.type = %q, want function; body=%s", got, string(out))
+	}
+	if !tools[2].Get("parameters").Exists() {
+		t.Fatalf("tools.2.parameters missing: %s", string(out))
 	}
 }
 

internal/runtime/executor/xai_websockets_executor_test.go

@@ -202,7 +202,15 @@ func TestXAIWebsocketsExecuteStreamRestoresNamespaceToolCalls(t *testing.T) {
 
 	select {
 	case payload := <-capturedPayload:
-		tool := gjson.GetBytes(payload, "input.0.tools.0")
+		for _, item := range gjson.GetBytes(payload, "input").Array() {
+			if got := item.Get("type").String(); got == "additional_tools" {
+				t.Fatalf("upstream input contains unsupported additional_tools item: %s", payload)
+			}
+		}
+		if got := gjson.GetBytes(payload, "input.0.role").String(); got != "user" {
+			t.Fatalf("input.0.role = %q, want user; payload=%s", got, payload)
+		}
+		tool := gjson.GetBytes(payload, "tools.0")
 		if got := tool.Get("name").String(); got != "mcp__exa__web_search_exa" {
 			t.Fatalf("upstream tool name = %q, want qualified name; payload=%s", got, payload)
 		}