feat(kiro): add multi-endpoint fallback & thinking mode support

internal/translator/kiro/openai/chat-completions/kiro_openai_request.go

@@ -10,9 +10,18 @@ import (
 	"github.com/tidwall/sjson"
 )
 
+// reasoningEffortToBudget maps OpenAI reasoning_effort values to Claude thinking budget_tokens.
+// OpenAI uses "low", "medium", "high" while Claude uses numeric budget_tokens.
+var reasoningEffortToBudget = map[string]int{
+	"low":    4000,
+	"medium": 16000,
+	"high":   32000,
+}
+
 // ConvertOpenAIRequestToKiro transforms an OpenAI Chat Completions API request into Kiro (Claude) format.
 // Kiro uses Claude-compatible format internally, so we primarily pass through to Claude format.
 // Supports tool calling: OpenAI tools -> Claude tools, tool_calls -> tool_use, tool messages -> tool_result.
+// Supports reasoning/thinking: OpenAI reasoning_effort -> Claude thinking parameter.
 func ConvertOpenAIRequestToKiro(modelName string, inputRawJSON []byte, stream bool) []byte {
 	rawJSON := bytes.Clone(inputRawJSON)
 	root := gjson.ParseBytes(rawJSON)
@@ -38,6 +47,26 @@ func ConvertOpenAIRequestToKiro(modelName string, inputRawJSON []byte, stream bo
 		out, _ = sjson.Set(out, "top_p", v.Float())
 	}
 
+	// Handle OpenAI reasoning_effort parameter -> Claude thinking parameter
+	// OpenAI format: {"reasoning_effort": "low"|"medium"|"high"}
+	// Claude format: {"thinking": {"type": "enabled", "budget_tokens": N}}
+	if v := root.Get("reasoning_effort"); v.Exists() {
+		effort := v.String()
+		if budget, ok := reasoningEffortToBudget[effort]; ok {
+			thinking := map[string]interface{}{
+				"type":          "enabled",
+				"budget_tokens": budget,
+			}
+			out, _ = sjson.Set(out, "thinking", thinking)
+		}
+	}
+
+	// Also support direct thinking parameter passthrough (for Claude API compatibility)
+	// Claude format: {"thinking": {"type": "enabled", "budget_tokens": N}}
+	if v := root.Get("thinking"); v.Exists() && v.IsObject() {
+		out, _ = sjson.Set(out, "thinking", v.Value())
+	}
+
 	// Convert OpenAI tools to Claude tools format
 	if tools := root.Get("tools"); tools.Exists() && tools.IsArray() {
 		claudeTools := make([]interface{}, 0)

internal/translator/kiro/openai/chat-completions/kiro_openai_response.go

@@ -134,6 +134,28 @@ func convertClaudeEventToOpenAI(jsonStr string, model string) []string {
 				result, _ := json.Marshal(response)
 				results = append(results, string(result))
 			}
+		} else if deltaType == "thinking_delta" {
+			// Thinking/reasoning content delta - convert to OpenAI reasoning_content format
+			thinkingDelta := root.Get("delta.thinking").String()
+			if thinkingDelta != "" {
+				response := map[string]interface{}{
+					"id":      "chatcmpl-" + uuid.New().String()[:24],
+					"object":  "chat.completion.chunk",
+					"created": time.Now().Unix(),
+					"model":   model,
+					"choices": []map[string]interface{}{
+						{
+							"index": 0,
+							"delta": map[string]interface{}{
+								"reasoning_content": thinkingDelta,
+							},
+							"finish_reason": nil,
+						},
+					},
+				}
+				result, _ := json.Marshal(response)
+				results = append(results, string(result))
+			}
 		} else if deltaType == "input_json_delta" {
 			// Tool input delta (streaming arguments)
 			partialJSON := root.Get("delta.partial_json").String()
@@ -298,6 +320,7 @@ func ConvertKiroResponseToOpenAINonStream(ctx context.Context, model string, ori
 	root := gjson.ParseBytes(rawResponse)
 
 	var content string
+	var reasoningContent string
 	var toolCalls []map[string]interface{}
 
 	contentArray := root.Get("content")
@@ -306,6 +329,9 @@ func ConvertKiroResponseToOpenAINonStream(ctx context.Context, model string, ori
 			itemType := item.Get("type").String()
 			if itemType == "text" {
 				content += item.Get("text").String()
+			} else if itemType == "thinking" {
+				// Extract thinking/reasoning content
+				reasoningContent += item.Get("thinking").String()
 			} else if itemType == "tool_use" {
 				// Convert Claude tool_use to OpenAI tool_calls format
 				inputJSON := item.Get("input").String()
@@ -339,6 +365,11 @@ func ConvertKiroResponseToOpenAINonStream(ctx context.Context, model string, ori
 		"content": content,
 	}
 
+	// Add reasoning_content if present (OpenAI reasoning format)
+	if reasoningContent != "" {
+		message["reasoning_content"] = reasoningContent
+	}
+
 	// Add tool_calls if present
 	if len(toolCalls) > 0 {
 		message["tool_calls"] = toolCalls