diff --git a/internal/runtime/executor/kiro_executor.go b/internal/runtime/executor/kiro_executor.go
index b69fd8be0..84fd990cb 100644
--- a/internal/runtime/executor/kiro_executor.go
+++ b/internal/runtime/executor/kiro_executor.go
@@ -121,7 +121,12 @@ func (e *KiroExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, req
 		return resp, fmt.Errorf("kiro: access token not found in auth")
 	}
 	if profileArn == "" {
-		log.Warnf("kiro: profile ARN not found in auth, API calls may fail")
+		// Only warn if not using builder-id auth (which doesn't need profileArn)
+		if auth == nil || auth.Metadata == nil {
+			log.Debugf("kiro: profile ARN not found in auth (may be normal for builder-id)")
+		} else if authMethod, ok := auth.Metadata["auth_method"].(string); !ok || authMethod != "builder-id" {
+			log.Warnf("kiro: profile ARN not found in auth, API calls may fail")
+		}
 	}
 
 	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
@@ -161,10 +166,19 @@ func (e *KiroExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, req
 		currentOrigin = "CLI"
 	}
 	
-	kiroPayload := e.buildKiroPayload(body, kiroModelID, profileArn, currentOrigin, isAgentic, isChatOnly)
+	// Determine if profileArn should be included based on auth method
+	// profileArn is only needed for social auth (Google OAuth), not for builder-id (AWS SSO)
+	effectiveProfileArn := profileArn
+	if auth != nil && auth.Metadata != nil {
+		if authMethod, ok := auth.Metadata["auth_method"].(string); ok && authMethod == "builder-id" {
+			effectiveProfileArn = "" // Don't include profileArn for builder-id auth
+		}
+	}
+	
+	kiroPayload := e.buildKiroPayload(body, kiroModelID, effectiveProfileArn, currentOrigin, isAgentic, isChatOnly)
 
 	// Execute with retry on 401/403 and 429 (quota exhausted)
-	resp, err = e.executeWithRetry(ctx, auth, req, opts, accessToken, profileArn, kiroPayload, body, from, to, reporter, currentOrigin, kiroModelID, isAgentic, isChatOnly)
+	resp, err = e.executeWithRetry(ctx, auth, req, opts, accessToken, effectiveProfileArn, kiroPayload, body, from, to, reporter, currentOrigin, kiroModelID, isAgentic, isChatOnly)
 	return resp, err
 }
 
@@ -301,9 +315,18 @@ func (e *KiroExecutor) executeWithRetry(ctx context.Context, auth *cliproxyauth.
 				}
 			}
 			if len(content) > 0 {
-				usageInfo.OutputTokens = int64(len(content) / 4)
+				// Use tiktoken for more accurate output token calculation
+				if enc, encErr := tokenizerForModel(req.Model); encErr == nil {
+					if tokenCount, countErr := enc.Count(content); countErr == nil {
+						usageInfo.OutputTokens = int64(tokenCount)
+					}
+				}
+				// Fallback to character count estimation if tiktoken fails
 				if usageInfo.OutputTokens == 0 {
-					usageInfo.OutputTokens = 1
+					usageInfo.OutputTokens = int64(len(content) / 4)
+					if usageInfo.OutputTokens == 0 {
+						usageInfo.OutputTokens = 1
+					}
 				}
 			}
 			usageInfo.TotalTokens = usageInfo.InputTokens + usageInfo.OutputTokens
@@ -330,7 +353,12 @@ func (e *KiroExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Aut
 		return nil, fmt.Errorf("kiro: access token not found in auth")
 	}
 	if profileArn == "" {
-		log.Warnf("kiro: profile ARN not found in auth, API calls may fail")
+		// Only warn if not using builder-id auth (which doesn't need profileArn)
+		if auth == nil || auth.Metadata == nil {
+			log.Debugf("kiro: profile ARN not found in auth (may be normal for builder-id)")
+		} else if authMethod, ok := auth.Metadata["auth_method"].(string); !ok || authMethod != "builder-id" {
+			log.Warnf("kiro: profile ARN not found in auth, API calls may fail")
+		}
 	}
 
 	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
@@ -370,10 +398,19 @@ func (e *KiroExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Aut
 		currentOrigin = "CLI"
 	}
 	
-	kiroPayload := e.buildKiroPayload(body, kiroModelID, profileArn, currentOrigin, isAgentic, isChatOnly)
+	// Determine if profileArn should be included based on auth method
+	// profileArn is only needed for social auth (Google OAuth), not for builder-id (AWS SSO)
+	effectiveProfileArn := profileArn
+	if auth != nil && auth.Metadata != nil {
+		if authMethod, ok := auth.Metadata["auth_method"].(string); ok && authMethod == "builder-id" {
+			effectiveProfileArn = "" // Don't include profileArn for builder-id auth
+		}
+	}
+	
+	kiroPayload := e.buildKiroPayload(body, kiroModelID, effectiveProfileArn, currentOrigin, isAgentic, isChatOnly)
 
 	// Execute stream with retry on 401/403 and 429 (quota exhausted)
-	return e.executeStreamWithRetry(ctx, auth, req, opts, accessToken, profileArn, kiroPayload, body, from, reporter, currentOrigin, kiroModelID, isAgentic, isChatOnly)
+	return e.executeStreamWithRetry(ctx, auth, req, opts, accessToken, effectiveProfileArn, kiroPayload, body, from, reporter, currentOrigin, kiroModelID, isAgentic, isChatOnly)
 }
 
 // executeStreamWithRetry performs the streaming HTTP request with automatic retry on auth errors.
@@ -491,6 +528,12 @@ func (e *KiroExecutor) executeStreamWithRetry(ctx context.Context, auth *cliprox
 
 		go func(resp *http.Response) {
 			defer close(out)
+			defer func() {
+				if r := recover(); r != nil {
+					log.Errorf("kiro: panic in stream handler: %v", r)
+					out <- cliproxyexecutor.StreamChunk{Err: fmt.Errorf("internal error: %v", r)}
+				}
+			}()
 			defer func() {
 				if errClose := resp.Body.Close(); errClose != nil {
 					log.Errorf("response body close error: %v", errClose)
@@ -587,10 +630,10 @@ type kiroPayload struct {
 }
 
 type kiroConversationState struct {
+	ChatTriggerType string               `json:"chatTriggerType"` // Required: "MANUAL" - must be first field
 	ConversationID  string               `json:"conversationId"`
-	History         []kiroHistoryMessage `json:"history"`
 	CurrentMessage  kiroCurrentMessage   `json:"currentMessage"`
-	ChatTriggerType string               `json:"chatTriggerType"` // Required: "MANUAL"
+	History         []kiroHistoryMessage `json:"history,omitempty"` // Only include when non-empty
 }
 
 type kiroCurrentMessage struct {
@@ -627,9 +670,9 @@ type kiroUserInputMessageContext struct {
 }
 
 type kiroToolResult struct {
-	ToolUseID string              `json:"toolUseId"`
 	Content   []kiroTextContent   `json:"content"`
 	Status    string              `json:"status"`
+	ToolUseID string              `json:"toolUseId"`
 }
 
 type kiroTextContent struct {
@@ -735,7 +778,9 @@ func (e *KiroExecutor) buildKiroPayload(claudeBody []byte, modelID, profileArn,
 	var currentUserMsg *kiroUserInputMessage
 	var currentToolResults []kiroToolResult
 
-	messagesArray := messages.Array()
+	// Merge adjacent messages with the same role before processing
+	// This reduces API call complexity and improves compatibility
+	messagesArray := mergeAdjacentMessages(messages.Array())
 	for i, msg := range messagesArray {
 		role := msg.Get("role").String()
 		isLastMessage := i == len(messagesArray)-1
@@ -746,6 +791,14 @@ func (e *KiroExecutor) buildKiroPayload(claudeBody []byte, modelID, profileArn,
 				currentUserMsg = &userMsg
 				currentToolResults = toolResults
 			} else {
+				// CRITICAL: Kiro API requires content to be non-empty for history messages too
+				if strings.TrimSpace(userMsg.Content) == "" {
+					if len(toolResults) > 0 {
+						userMsg.Content = "Tool results provided."
+					} else {
+						userMsg.Content = "Continue"
+					}
+				}
 				// For history messages, embed tool results in context
 				if len(toolResults) > 0 {
 					userMsg.UserInputMessageContext = &kiroUserInputMessageContext{
@@ -758,9 +811,24 @@ func (e *KiroExecutor) buildKiroPayload(claudeBody []byte, modelID, profileArn,
 			}
 		} else if role == "assistant" {
 			assistantMsg := e.buildAssistantMessageStruct(msg)
-			history = append(history, kiroHistoryMessage{
-				AssistantResponseMessage: &assistantMsg,
-			})
+			// If this is the last message and it's an assistant message,
+			// we need to add it to history and create a "Continue" user message
+			// because Kiro API requires currentMessage to be userInputMessage type
+			if isLastMessage {
+				history = append(history, kiroHistoryMessage{
+					AssistantResponseMessage: &assistantMsg,
+				})
+				// Create a "Continue" user message as currentMessage
+				currentUserMsg = &kiroUserInputMessage{
+					Content: "Continue",
+					ModelID: modelID,
+					Origin:  origin,
+				}
+			} else {
+				history = append(history, kiroHistoryMessage{
+					AssistantResponseMessage: &assistantMsg,
+				})
+			}
 		}
 	}
 
@@ -777,7 +845,35 @@ func (e *KiroExecutor) buildKiroPayload(claudeBody []byte, modelID, profileArn,
 		
 		// Add the actual user message
 		contentBuilder.WriteString(currentUserMsg.Content)
-		currentUserMsg.Content = contentBuilder.String()
+		finalContent := contentBuilder.String()
+		
+		// CRITICAL: Kiro API requires content to be non-empty, even when toolResults are present
+		// If content is empty or only whitespace, provide a default message
+		if strings.TrimSpace(finalContent) == "" {
+			if len(currentToolResults) > 0 {
+				finalContent = "Tool results provided."
+			} else {
+				finalContent = "Continue"
+			}
+			log.Debugf("kiro: content was empty, using default: %s", finalContent)
+		}
+		currentUserMsg.Content = finalContent
+		
+		// Deduplicate currentToolResults before adding to context
+		// Kiro API does not accept duplicate toolUseIds
+		if len(currentToolResults) > 0 {
+			seenIDs := make(map[string]bool)
+			uniqueToolResults := make([]kiroToolResult, 0, len(currentToolResults))
+			for _, tr := range currentToolResults {
+				if !seenIDs[tr.ToolUseID] {
+					seenIDs[tr.ToolUseID] = true
+					uniqueToolResults = append(uniqueToolResults, tr)
+				} else {
+					log.Debugf("kiro: skipping duplicate toolResult in currentMessage: %s", tr.ToolUseID)
+				}
+			}
+			currentToolResults = uniqueToolResults
+		}
 		
 		// Build userInputMessageContext with tools and tool results
 		if len(kiroTools) > 0 || len(currentToolResults) > 0 {
@@ -805,21 +901,18 @@ func (e *KiroExecutor) buildKiroPayload(claudeBody []byte, modelID, profileArn,
 		}}
 	}
 	
+	// Build payload with correct field order (matches struct definition)
+	// Note: history is omitempty, so nil/empty slice won't be serialized
 	payload := kiroPayload{
 		ConversationState: kiroConversationState{
+			ChatTriggerType: "MANUAL", // Required by Kiro API - must be first
 			ConversationID:  uuid.New().String(),
-			History:         history,
 			CurrentMessage:  currentMessage,
-			ChatTriggerType: "MANUAL", // Required by Kiro API
+			History:         history, // Will be omitted if empty due to omitempty tag
 		},
 		ProfileArn: profileArn,
 	}
 
-	// Ensure history is not nil (empty array)
-	if payload.ConversationState.History == nil {
-		payload.ConversationState.History = []kiroHistoryMessage{}
-	}
-
 	result, err := json.Marshal(payload)
 	if err != nil {
 		log.Debugf("kiro: failed to marshal payload: %v", err)
@@ -830,11 +923,15 @@ func (e *KiroExecutor) buildKiroPayload(claudeBody []byte, modelID, profileArn,
 
 // buildUserMessageStruct builds a user message and extracts tool results
 // origin parameter determines which quota to use: "CLI" for Amazon Q, "AI_EDITOR" for Kiro IDE.
+// IMPORTANT: Kiro API does not accept duplicate toolUseIds, so we deduplicate here.
 func (e *KiroExecutor) buildUserMessageStruct(msg gjson.Result, modelID, origin string) (kiroUserInputMessage, []kiroToolResult) {
 	content := msg.Get("content")
 	var contentBuilder strings.Builder
 	var toolResults []kiroToolResult
 	var images []kiroImage
+	
+	// Track seen toolUseIds to deduplicate - Kiro API rejects duplicate toolUseIds
+	seenToolUseIDs := make(map[string]bool)
 
 	if content.IsArray() {
 		for _, part := range content.Array() {
@@ -864,6 +961,14 @@ func (e *KiroExecutor) buildUserMessageStruct(msg gjson.Result, modelID, origin
 			case "tool_result":
 				// Extract tool result for API
 				toolUseID := part.Get("tool_use_id").String()
+				
+				// Skip duplicate toolUseIds - Kiro API does not accept duplicates
+				if seenToolUseIDs[toolUseID] {
+					log.Debugf("kiro: skipping duplicate tool_result with toolUseId: %s", toolUseID)
+					continue
+				}
+				seenToolUseIDs[toolUseID] = true
+				
 				isError := part.Get("is_error").Bool()
 				resultContent := part.Get("content")
 				
@@ -1001,6 +1106,12 @@ func (e *KiroExecutor) parseEventStream(body io.Reader) (string, []kiroToolUse,
 			return content.String(), toolUses, usageInfo, fmt.Errorf("failed to read message: %w", err)
 		}
 
+		// Validate headersLen to prevent slice out of bounds
+		if headersLen+4 > uint32(len(remaining)) {
+			log.Warnf("kiro: invalid headersLen %d exceeds remaining buffer %d", headersLen, len(remaining))
+			continue
+		}
+
 		// Extract event type from headers
 		eventType := e.extractEventType(remaining[:headersLen+4])
 
@@ -1018,6 +1129,37 @@ func (e *KiroExecutor) parseEventStream(body io.Reader) (string, []kiroToolUse,
 			continue
 		}
 
+		// DIAGNOSTIC: Log all received event types for debugging
+		log.Debugf("kiro: parseEventStream received event type: %s", eventType)
+		if log.IsLevelEnabled(log.TraceLevel) {
+			log.Tracef("kiro: parseEventStream event payload: %s", string(payload))
+		}
+
+		// Check for error/exception events in the payload (Kiro API may return errors with HTTP 200)
+		// These can appear as top-level fields or nested within the event
+		if errType, hasErrType := event["_type"].(string); hasErrType {
+			// AWS-style error: {"_type": "com.amazon.aws.codewhisperer#ValidationException", "message": "..."}
+			errMsg := ""
+			if msg, ok := event["message"].(string); ok {
+				errMsg = msg
+			}
+			log.Errorf("kiro: received AWS error in event stream: type=%s, message=%s", errType, errMsg)
+			return "", nil, usageInfo, fmt.Errorf("kiro API error: %s - %s", errType, errMsg)
+		}
+		if errType, hasErrType := event["type"].(string); hasErrType && (errType == "error" || errType == "exception") {
+			// Generic error event
+			errMsg := ""
+			if msg, ok := event["message"].(string); ok {
+				errMsg = msg
+			} else if errObj, ok := event["error"].(map[string]interface{}); ok {
+				if msg, ok := errObj["message"].(string); ok {
+					errMsg = msg
+				}
+			}
+			log.Errorf("kiro: received error event in stream: type=%s, message=%s", errType, errMsg)
+			return "", nil, usageInfo, fmt.Errorf("kiro API error: %s", errMsg)
+		}
+
 		// Handle different event types
 		switch eventType {
 		case "assistantResponseEvent":
@@ -1231,8 +1373,9 @@ func (e *KiroExecutor) buildClaudeResponse(content string, toolUses []kiroToolUs
 // streamToChannel converts AWS Event Stream to channel-based streaming.
 // Supports tool calling - emits tool_use content blocks when tools are used.
 // Includes embedded [Called ...] tool call parsing and input buffering for toolUseEvent.
+// Implements duplicate content filtering using lastContentEvent detection (based on AIClient-2-API).
 func (e *KiroExecutor) streamToChannel(ctx context.Context, body io.Reader, out chan<- cliproxyexecutor.StreamChunk, targetFormat sdktranslator.Format, model string, originalReq, claudeBody []byte, reporter *usageReporter) {
-	reader := bufio.NewReader(body)
+	reader := bufio.NewReaderSize(body, 20*1024*1024) // 20MB buffer to match other providers
 	var totalUsage usage.Detail
 	var hasToolUses bool // Track if any tool uses were emitted
 
@@ -1240,6 +1383,15 @@ func (e *KiroExecutor) streamToChannel(ctx context.Context, body io.Reader, out
 	processedIDs := make(map[string]bool)
 	var currentToolUse *toolUseState
 
+	// Duplicate content detection - tracks last content event to filter duplicates
+	// Based on AIClient-2-API implementation for Kiro
+	var lastContentEvent string
+
+	// Streaming token calculation - accumulate content for real-time token counting
+	// Based on AIClient-2-API implementation
+	var accumulatedContent strings.Builder
+	accumulatedContent.Grow(4096) // Pre-allocate 4KB capacity to reduce reallocations
+
 	// Translator param for maintaining tool call state across streaming events
 	// IMPORTANT: This must persist across all TranslateStream calls
 	var translatorParam any
@@ -1279,6 +1431,51 @@ func (e *KiroExecutor) streamToChannel(ctx context.Context, body io.Reader, out
 		prelude := make([]byte, 8)
 		_, err := io.ReadFull(reader, prelude)
 		if err == io.EOF {
+			// Flush any incomplete tool use before ending stream
+			if currentToolUse != nil && !processedIDs[currentToolUse.toolUseID] {
+				log.Warnf("kiro: flushing incomplete tool use at EOF: %s (ID: %s)", currentToolUse.name, currentToolUse.toolUseID)
+				fullInput := currentToolUse.inputBuffer.String()
+				repairedJSON := repairJSON(fullInput)
+				var finalInput map[string]interface{}
+				if err := json.Unmarshal([]byte(repairedJSON), &finalInput); err != nil {
+					log.Warnf("kiro: failed to parse incomplete tool input at EOF: %v", err)
+					finalInput = make(map[string]interface{})
+				}
+				
+				processedIDs[currentToolUse.toolUseID] = true
+				contentBlockIndex++
+				
+				// Send tool_use content block
+				blockStart := e.buildClaudeContentBlockStartEvent(contentBlockIndex, "tool_use", currentToolUse.toolUseID, currentToolUse.name)
+				sseData := sdktranslator.TranslateStream(ctx, sdktranslator.FromString("kiro"), targetFormat, model, originalReq, claudeBody, blockStart, &translatorParam)
+				for _, chunk := range sseData {
+					if chunk != "" {
+						out <- cliproxyexecutor.StreamChunk{Payload: []byte(chunk + "\n\n")}
+					}
+				}
+				
+				// Send tool input as delta
+				inputBytes, _ := json.Marshal(finalInput)
+				inputDelta := e.buildClaudeInputJsonDeltaEvent(string(inputBytes), contentBlockIndex)
+				sseData = sdktranslator.TranslateStream(ctx, sdktranslator.FromString("kiro"), targetFormat, model, originalReq, claudeBody, inputDelta, &translatorParam)
+				for _, chunk := range sseData {
+					if chunk != "" {
+						out <- cliproxyexecutor.StreamChunk{Payload: []byte(chunk + "\n\n")}
+					}
+				}
+				
+				// Close block
+				blockStop := e.buildClaudeContentBlockStopEvent(contentBlockIndex)
+				sseData = sdktranslator.TranslateStream(ctx, sdktranslator.FromString("kiro"), targetFormat, model, originalReq, claudeBody, blockStop, &translatorParam)
+				for _, chunk := range sseData {
+					if chunk != "" {
+						out <- cliproxyexecutor.StreamChunk{Payload: []byte(chunk + "\n\n")}
+					}
+				}
+				
+				hasToolUses = true
+				currentToolUse = nil
+			}
 			break
 		}
 		if err != nil {
@@ -1304,6 +1501,12 @@ func (e *KiroExecutor) streamToChannel(ctx context.Context, body io.Reader, out
 			return
 		}
 
+		// Validate headersLen to prevent slice out of bounds
+		if headersLen+4 > uint32(len(remaining)) {
+			log.Warnf("kiro: invalid headersLen %d exceeds remaining buffer %d", headersLen, len(remaining))
+			continue
+		}
+
 		eventType := e.extractEventType(remaining[:headersLen+4])
 
 		payloadStart := 4 + headersLen
@@ -1317,9 +1520,43 @@ func (e *KiroExecutor) streamToChannel(ctx context.Context, body io.Reader, out
 
 		var event map[string]interface{}
 		if err := json.Unmarshal(payload, &event); err != nil {
+			log.Warnf("kiro: failed to unmarshal event payload: %v, raw: %s", err, string(payload))
 			continue
 		}
 
+		// DIAGNOSTIC: Log all received event types for debugging
+		log.Debugf("kiro: streamToChannel received event type: %s", eventType)
+		if log.IsLevelEnabled(log.TraceLevel) {
+			log.Tracef("kiro: streamToChannel event payload: %s", string(payload))
+		}
+
+		// Check for error/exception events in the payload (Kiro API may return errors with HTTP 200)
+		// These can appear as top-level fields or nested within the event
+		if errType, hasErrType := event["_type"].(string); hasErrType {
+			// AWS-style error: {"_type": "com.amazon.aws.codewhisperer#ValidationException", "message": "..."}
+			errMsg := ""
+			if msg, ok := event["message"].(string); ok {
+				errMsg = msg
+			}
+			log.Errorf("kiro: received AWS error in stream: type=%s, message=%s", errType, errMsg)
+			out <- cliproxyexecutor.StreamChunk{Err: fmt.Errorf("kiro API error: %s - %s", errType, errMsg)}
+			return
+		}
+		if errType, hasErrType := event["type"].(string); hasErrType && (errType == "error" || errType == "exception") {
+			// Generic error event
+			errMsg := ""
+			if msg, ok := event["message"].(string); ok {
+				errMsg = msg
+			} else if errObj, ok := event["error"].(map[string]interface{}); ok {
+				if msg, ok := errObj["message"].(string); ok {
+					errMsg = msg
+				}
+			}
+			log.Errorf("kiro: received error event in stream: type=%s, message=%s", errType, errMsg)
+			out <- cliproxyexecutor.StreamChunk{Err: fmt.Errorf("kiro API error: %s", errMsg)}
+			return
+		}
+
 		// Send message_start on first event
 		if !messageStartSent {
 			msgStart := e.buildClaudeMessageStartEvent(model, totalUsage.InputTokens)
@@ -1364,9 +1601,19 @@ func (e *KiroExecutor) streamToChannel(ctx context.Context, body io.Reader, out
 				}
 			}
 
-			// Handle text content
+			// Handle text content with duplicate detection
 			if contentDelta != "" {
+				// Check for duplicate content - skip if identical to last content event
+				// Based on AIClient-2-API implementation for Kiro
+				if contentDelta == lastContentEvent {
+					log.Debugf("kiro: skipping duplicate content event (len: %d)", len(contentDelta))
+					continue
+				}
+				lastContentEvent = contentDelta
+
 				outputLen += len(contentDelta)
+				// Accumulate content for streaming token calculation
+				accumulatedContent.WriteString(contentDelta)
 				// Start text content block if needed
 				if !isTextBlockOpen {
 					contentBlockIndex++
@@ -1538,8 +1785,32 @@ func (e *KiroExecutor) streamToChannel(ctx context.Context, body io.Reader, out
 		}
 	}
 
-	// Fallback for output tokens if not received from upstream
-	if totalUsage.OutputTokens == 0 && outputLen > 0 {
+	// Streaming token calculation - calculate output tokens from accumulated content
+	// This provides more accurate token counting than simple character division
+	if totalUsage.OutputTokens == 0 && accumulatedContent.Len() > 0 {
+		// Try to use tiktoken for accurate counting
+		if enc, err := tokenizerForModel(model); err == nil {
+			if tokenCount, countErr := enc.Count(accumulatedContent.String()); countErr == nil {
+				totalUsage.OutputTokens = int64(tokenCount)
+				log.Debugf("kiro: streamToChannel calculated output tokens using tiktoken: %d", totalUsage.OutputTokens)
+			} else {
+				// Fallback on count error: estimate from character count
+				totalUsage.OutputTokens = int64(accumulatedContent.Len() / 4)
+				if totalUsage.OutputTokens == 0 {
+					totalUsage.OutputTokens = 1
+				}
+				log.Debugf("kiro: streamToChannel tiktoken count failed, estimated from chars: %d", totalUsage.OutputTokens)
+			}
+		} else {
+			// Fallback: estimate from character count (roughly 4 chars per token)
+			totalUsage.OutputTokens = int64(accumulatedContent.Len() / 4)
+			if totalUsage.OutputTokens == 0 {
+				totalUsage.OutputTokens = 1
+			}
+			log.Debugf("kiro: streamToChannel estimated output tokens from chars: %d (content len: %d)", totalUsage.OutputTokens, accumulatedContent.Len())
+		}
+	} else if totalUsage.OutputTokens == 0 && outputLen > 0 {
+		// Legacy fallback using outputLen
 		totalUsage.OutputTokens = int64(outputLen / 4)
 		if totalUsage.OutputTokens == 0 {
 			totalUsage.OutputTokens = 1
@@ -1553,9 +1824,18 @@ func (e *KiroExecutor) streamToChannel(ctx context.Context, body io.Reader, out
 		stopReason = "tool_use"
 	}
 
-	// Send message_delta and message_stop
-	msgStop := e.buildClaudeMessageStopEvent(stopReason, totalUsage)
-	sseData := sdktranslator.TranslateStream(ctx, sdktranslator.FromString("kiro"), targetFormat, model, originalReq, claudeBody, msgStop, &translatorParam)
+	// Send message_delta event
+	msgDelta := e.buildClaudeMessageDeltaEvent(stopReason, totalUsage)
+	sseData := sdktranslator.TranslateStream(ctx, sdktranslator.FromString("kiro"), targetFormat, model, originalReq, claudeBody, msgDelta, &translatorParam)
+	for _, chunk := range sseData {
+		if chunk != "" {
+			out <- cliproxyexecutor.StreamChunk{Payload: []byte(chunk + "\n\n")}
+		}
+	}
+
+	// Send message_stop event separately
+	msgStop := e.buildClaudeMessageStopOnlyEvent()
+	sseData = sdktranslator.TranslateStream(ctx, sdktranslator.FromString("kiro"), targetFormat, model, originalReq, claudeBody, msgStop, &translatorParam)
 	for _, chunk := range sseData {
 		if chunk != "" {
 			out <- cliproxyexecutor.StreamChunk{Payload: []byte(chunk + "\n\n")}
@@ -1646,8 +1926,8 @@ func (e *KiroExecutor) buildClaudeContentBlockStopEvent(index int) []byte {
 	return []byte("event: content_block_stop\ndata: " + string(result))
 }
 
-func (e *KiroExecutor) buildClaudeMessageStopEvent(stopReason string, usageInfo usage.Detail) []byte {
-	// First message_delta
+// buildClaudeMessageDeltaEvent creates the message_delta event with stop_reason and usage.
+func (e *KiroExecutor) buildClaudeMessageDeltaEvent(stopReason string, usageInfo usage.Detail) []byte {
 	deltaEvent := map[string]interface{}{
 		"type": "message_delta",
 		"delta": map[string]interface{}{
@@ -1660,14 +1940,16 @@ func (e *KiroExecutor) buildClaudeMessageStopEvent(stopReason string, usageInfo
 		},
 	}
 	deltaResult, _ := json.Marshal(deltaEvent)
+	return []byte("event: message_delta\ndata: " + string(deltaResult))
+}
 
-	// Then message_stop
+// buildClaudeMessageStopOnlyEvent creates only the message_stop event.
+func (e *KiroExecutor) buildClaudeMessageStopOnlyEvent() []byte {
 	stopEvent := map[string]interface{}{
 		"type": "message_stop",
 	}
 	stopResult, _ := json.Marshal(stopEvent)
-
-	return []byte("event: message_delta\ndata: " + string(deltaResult) + "\n\nevent: message_stop\ndata: " + string(stopResult))
+	return []byte("event: message_stop\ndata: " + string(stopResult))
 }
 
 // buildClaudeFinalEvent constructs the final Claude-style event.
@@ -1873,6 +2155,12 @@ func (e *KiroExecutor) streamEventStream(ctx context.Context, body io.Reader, c
 			return fmt.Errorf("failed to read message: %w", err)
 		}
 
+		// Validate headersLen to prevent slice out of bounds
+		if headersLen+4 > uint32(len(remaining)) {
+			log.Warnf("kiro: invalid headersLen %d exceeds remaining buffer %d", headersLen, len(remaining))
+			continue
+		}
+
 		eventType := e.extractEventType(remaining[:headersLen+4])
 
 		payloadStart := 4 + headersLen
@@ -1886,6 +2174,7 @@ func (e *KiroExecutor) streamEventStream(ctx context.Context, body io.Reader, c
 
 		var event map[string]interface{}
 		if err := json.Unmarshal(payload, &event); err != nil {
+			log.Warnf("kiro: failed to unmarshal event payload: %v, raw: %s", err, string(payload))
 			continue
 		}
 
@@ -1983,9 +2272,19 @@ func (e *KiroExecutor) streamEventStream(ctx context.Context, body io.Reader, c
 	}
 	totalUsage.TotalTokens = totalUsage.InputTokens + totalUsage.OutputTokens
 
-	// Always use end_turn (no tool_use support)
-	msgStop := e.buildClaudeMessageStopEvent("end_turn", totalUsage)
-	sseData := sdktranslator.TranslateStream(ctx, sdktranslator.FromString("kiro"), targetFormat, model, originalReq, claudeBody, msgStop, &translatorParam)
+	// Send message_delta event
+	msgDelta := e.buildClaudeMessageDeltaEvent("end_turn", totalUsage)
+	sseData := sdktranslator.TranslateStream(ctx, sdktranslator.FromString("kiro"), targetFormat, model, originalReq, claudeBody, msgDelta, &translatorParam)
+	for _, chunk := range sseData {
+		if chunk != "" {
+			c.Writer.Write([]byte(chunk + "\n\n"))
+		}
+	}
+	c.Writer.Flush()
+
+	// Send message_stop event separately
+	msgStop := e.buildClaudeMessageStopOnlyEvent()
+	sseData = sdktranslator.TranslateStream(ctx, sdktranslator.FromString("kiro"), targetFormat, model, originalReq, claudeBody, msgStop, &translatorParam)
 	for _, chunk := range sseData {
 		if chunk != "" {
 			c.Writer.Write([]byte(chunk + "\n\n"))
@@ -2057,6 +2356,128 @@ func (e *KiroExecutor) isTokenExpired(accessToken string) bool {
 	return isExpired
 }
 
+// ============================================================================
+// Message Merging Support - Merge adjacent messages with the same role
+// Based on AIClient-2-API implementation
+// ============================================================================
+
+// mergeAdjacentMessages merges adjacent messages with the same role.
+// This reduces API call complexity and improves compatibility.
+// Based on AIClient-2-API implementation.
+func mergeAdjacentMessages(messages []gjson.Result) []gjson.Result {
+	if len(messages) <= 1 {
+		return messages
+	}
+
+	var merged []gjson.Result
+	for _, msg := range messages {
+		if len(merged) == 0 {
+			merged = append(merged, msg)
+			continue
+		}
+
+		lastMsg := merged[len(merged)-1]
+		currentRole := msg.Get("role").String()
+		lastRole := lastMsg.Get("role").String()
+
+		if currentRole == lastRole {
+			// Merge content from current message into last message
+			mergedContent := mergeMessageContent(lastMsg, msg)
+			// Create a new merged message JSON
+			mergedMsg := createMergedMessage(lastRole, mergedContent)
+			merged[len(merged)-1] = gjson.Parse(mergedMsg)
+		} else {
+			merged = append(merged, msg)
+		}
+	}
+
+	return merged
+}
+
+// mergeMessageContent merges the content of two messages with the same role.
+// Handles both string content and array content (with text, tool_use, tool_result blocks).
+func mergeMessageContent(msg1, msg2 gjson.Result) string {
+	content1 := msg1.Get("content")
+	content2 := msg2.Get("content")
+
+	// Extract content blocks from both messages
+	var blocks1, blocks2 []map[string]interface{}
+
+	if content1.IsArray() {
+		for _, block := range content1.Array() {
+			blocks1 = append(blocks1, blockToMap(block))
+		}
+	} else if content1.Type == gjson.String {
+		blocks1 = append(blocks1, map[string]interface{}{
+			"type": "text",
+			"text": content1.String(),
+		})
+	}
+
+	if content2.IsArray() {
+		for _, block := range content2.Array() {
+			blocks2 = append(blocks2, blockToMap(block))
+		}
+	} else if content2.Type == gjson.String {
+		blocks2 = append(blocks2, map[string]interface{}{
+			"type": "text",
+			"text": content2.String(),
+		})
+	}
+
+	// Merge text blocks if both end/start with text
+	if len(blocks1) > 0 && len(blocks2) > 0 {
+		if blocks1[len(blocks1)-1]["type"] == "text" && blocks2[0]["type"] == "text" {
+			// Merge the last text block of msg1 with the first text block of msg2
+			text1 := blocks1[len(blocks1)-1]["text"].(string)
+			text2 := blocks2[0]["text"].(string)
+			blocks1[len(blocks1)-1]["text"] = text1 + "\n" + text2
+			blocks2 = blocks2[1:] // Remove the merged block from blocks2
+		}
+	}
+
+	// Combine all blocks
+	allBlocks := append(blocks1, blocks2...)
+
+	// Convert to JSON
+	result, _ := json.Marshal(allBlocks)
+	return string(result)
+}
+
+// blockToMap converts a gjson.Result block to a map[string]interface{}
+func blockToMap(block gjson.Result) map[string]interface{} {
+	result := make(map[string]interface{})
+	block.ForEach(func(key, value gjson.Result) bool {
+		if value.IsObject() {
+			result[key.String()] = blockToMap(value)
+		} else if value.IsArray() {
+			var arr []interface{}
+			for _, item := range value.Array() {
+				if item.IsObject() {
+					arr = append(arr, blockToMap(item))
+				} else {
+					arr = append(arr, item.Value())
+				}
+			}
+			result[key.String()] = arr
+		} else {
+			result[key.String()] = value.Value()
+		}
+		return true
+	})
+	return result
+}
+
+// createMergedMessage creates a JSON string for a merged message
+func createMergedMessage(role string, content string) string {
+	msg := map[string]interface{}{
+		"role":    role,
+		"content": json.RawMessage(content),
+	}
+	result, _ := json.Marshal(msg)
+	return string(result)
+}
+
 // ============================================================================
 // Tool Calling Support - Embedded tool call parsing and input buffering
 // Based on amq2api and AIClient-2-API implementations
@@ -2079,8 +2500,6 @@ var (
 	whitespaceCollapsePattern = regexp.MustCompile(`\s+`)
 	// trailingCommaPattern matches trailing commas before closing braces/brackets
 	trailingCommaPattern = regexp.MustCompile(`,\s*([}\]])`)
-	// unquotedKeyPattern matches unquoted JSON keys that need quoting
-	unquotedKeyPattern = regexp.MustCompile(`([{,]\s*)([a-zA-Z_][a-zA-Z0-9_]*)\s*:`)
 )
 
 // parseEmbeddedToolCalls extracts [Called tool_name with args: {...}] format from text.
@@ -2246,14 +2665,208 @@ func findMatchingBracket(text string, startPos int) int {
 }
 
 // repairJSON attempts to fix common JSON issues that may occur in tool call arguments.
-// Based on AIClient-2-API's JSON repair implementation.
+// Based on AIClient-2-API's JSON repair implementation with a more conservative strategy.
+//
+// Conservative repair strategy:
+// 1. First try to parse JSON directly - if valid, return as-is
+// 2. Only attempt repair if parsing fails
+// 3. After repair, validate the result - if still invalid, return original
+//
+// Handles incomplete JSON by balancing brackets and removing trailing incomplete content.
 // Uses pre-compiled regex patterns for performance.
-func repairJSON(raw string) string {
+func repairJSON(jsonString string) string {
+	// Handle empty or invalid input
+	if jsonString == "" {
+		return "{}"
+	}
+	
+	str := strings.TrimSpace(jsonString)
+	if str == "" {
+		return "{}"
+	}
+	
+	// CONSERVATIVE STRATEGY: First try to parse directly
+	// If the JSON is already valid, return it unchanged
+	var testParse interface{}
+	if err := json.Unmarshal([]byte(str), &testParse); err == nil {
+		log.Debugf("kiro: repairJSON - JSON is already valid, returning unchanged")
+		return str
+	}
+	
+	log.Debugf("kiro: repairJSON - JSON parse failed, attempting repair")
+	originalStr := str // Keep original for fallback
+	
+	// First, escape unescaped newlines/tabs within JSON string values
+	str = escapeNewlinesInStrings(str)
 	// Remove trailing commas before closing braces/brackets
-	repaired := trailingCommaPattern.ReplaceAllString(raw, "$1")
-	// Fix unquoted keys (basic attempt - handles simple cases)
-	repaired = unquotedKeyPattern.ReplaceAllString(repaired, `$1"$2":`)
-	return repaired
+	str = trailingCommaPattern.ReplaceAllString(str, "$1")
+	
+	// Calculate bracket balance to detect incomplete JSON
+	braceCount := 0    // {} balance
+	bracketCount := 0  // [] balance
+	inString := false
+	escape := false
+	lastValidIndex := -1
+	
+	for i := 0; i < len(str); i++ {
+		char := str[i]
+		
+		// Handle escape sequences
+		if escape {
+			escape = false
+			continue
+		}
+		
+		if char == '\\' {
+			escape = true
+			continue
+		}
+		
+		// Handle string boundaries
+		if char == '"' {
+			inString = !inString
+			continue
+		}
+		
+		// Skip characters inside strings (they don't affect bracket balance)
+		if inString {
+			continue
+		}
+		
+		// Track bracket balance
+		switch char {
+		case '{':
+			braceCount++
+		case '}':
+			braceCount--
+		case '[':
+			bracketCount++
+		case ']':
+			bracketCount--
+		}
+		
+		// Record last valid position (where brackets are balanced or positive)
+		if braceCount >= 0 && bracketCount >= 0 {
+			lastValidIndex = i
+		}
+	}
+	
+	// If brackets are unbalanced, try to repair
+	if braceCount > 0 || bracketCount > 0 {
+		// Truncate to last valid position if we have incomplete content
+		if lastValidIndex > 0 && lastValidIndex < len(str)-1 {
+			// Check if truncation would help (only truncate if there's trailing garbage)
+			truncated := str[:lastValidIndex+1]
+			// Recount brackets after truncation
+			braceCount = 0
+			bracketCount = 0
+			inString = false
+			escape = false
+			for i := 0; i < len(truncated); i++ {
+				char := truncated[i]
+				if escape {
+					escape = false
+					continue
+				}
+				if char == '\\' {
+					escape = true
+					continue
+				}
+				if char == '"' {
+					inString = !inString
+					continue
+				}
+				if inString {
+					continue
+				}
+				switch char {
+				case '{':
+					braceCount++
+				case '}':
+					braceCount--
+				case '[':
+					bracketCount++
+				case ']':
+					bracketCount--
+				}
+			}
+			str = truncated
+		}
+		
+		// Add missing closing brackets
+		for braceCount > 0 {
+			str += "}"
+			braceCount--
+		}
+		for bracketCount > 0 {
+			str += "]"
+			bracketCount--
+		}
+	}
+	
+	// CONSERVATIVE STRATEGY: Validate repaired JSON
+	// If repair didn't produce valid JSON, return original string
+	if err := json.Unmarshal([]byte(str), &testParse); err != nil {
+		log.Warnf("kiro: repairJSON - repair failed to produce valid JSON, returning original")
+		return originalStr
+	}
+	
+	log.Debugf("kiro: repairJSON - successfully repaired JSON")
+	return str
+}
+
+// escapeNewlinesInStrings escapes literal newlines, tabs, and other control characters
+// that appear inside JSON string values. This handles cases where streaming fragments
+// contain unescaped control characters within string content.
+func escapeNewlinesInStrings(raw string) string {
+	var result strings.Builder
+	result.Grow(len(raw) + 100) // Pre-allocate with some extra space
+
+	inString := false
+	escaped := false
+
+	for i := 0; i < len(raw); i++ {
+		c := raw[i]
+
+		if escaped {
+			// Previous character was backslash, this is an escape sequence
+			result.WriteByte(c)
+			escaped = false
+			continue
+		}
+
+		if c == '\\' && inString {
+			// Start of escape sequence
+			result.WriteByte(c)
+			escaped = true
+			continue
+		}
+
+		if c == '"' {
+			// Toggle string state
+			inString = !inString
+			result.WriteByte(c)
+			continue
+		}
+
+		if inString {
+			// Inside a string, escape control characters
+			switch c {
+			case '\n':
+				result.WriteString("\\n")
+			case '\r':
+				result.WriteString("\\r")
+			case '\t':
+				result.WriteString("\\t")
+			default:
+				result.WriteByte(c)
+			}
+		} else {
+			result.WriteByte(c)
+		}
+	}
+
+	return result.String()
 }
 
 // processToolUseEvent handles a toolUseEvent from the Kiro stream.
@@ -2330,6 +2943,8 @@ func (e *KiroExecutor) processToolUseEvent(event map[string]interface{}, current
 
 	// Accumulate input fragments
 	if currentToolUse != nil && inputFragment != "" {
+		// Accumulate fragments directly - they form valid JSON when combined
+		// The fragments are already decoded from JSON, so we just concatenate them
 		currentToolUse.inputBuffer.WriteString(inputFragment)
 		log.Debugf("kiro: accumulated input fragment, total length: %d", currentToolUse.inputBuffer.Len())
 	}
diff --git a/internal/translator/kiro/openai/chat-completions/kiro_openai_response.go b/internal/translator/kiro/openai/chat-completions/kiro_openai_response.go
index df75cc070..d56c94acf 100644
--- a/internal/translator/kiro/openai/chat-completions/kiro_openai_response.go
+++ b/internal/translator/kiro/openai/chat-completions/kiro_openai_response.go
@@ -171,7 +171,7 @@ func convertClaudeEventToOpenAI(jsonStr string, model string) []string {
 		return results
 
 	case "message_delta":
-		// Final message delta with stop_reason
+		// Final message delta with stop_reason and usage
 		stopReason := root.Get("delta.stop_reason").String()
 		if stopReason != "" {
 			finishReason := "stop"
@@ -196,6 +196,19 @@ func convertClaudeEventToOpenAI(jsonStr string, model string) []string {
 					},
 				},
 			}
+
+			// Extract and include usage information from message_delta event
+			usage := root.Get("usage")
+			if usage.Exists() {
+				inputTokens := usage.Get("input_tokens").Int()
+				outputTokens := usage.Get("output_tokens").Int()
+				response["usage"] = map[string]interface{}{
+					"prompt_tokens":     inputTokens,
+					"completion_tokens": outputTokens,
+					"total_tokens":      inputTokens + outputTokens,
+				}
+			}
+
 			result, _ := json.Marshal(response)
 			results = append(results, string(result))
 		}