diff --git a/internal/translator/kiro/openai/kiro_openai_request.go b/internal/translator/kiro/openai/kiro_openai_request.go
index 93914c6d..a621eebc 100644
--- a/internal/translator/kiro/openai/kiro_openai_request.go
+++ b/internal/translator/kiro/openai/kiro_openai_request.go
@@ -576,9 +576,23 @@ func processOpenAIMessages(messages gjson.Result, modelID, origin string) ([]Kir
 		}
 	}
 
+	// Truncate history if too long to prevent Kiro API errors
+	history = truncateHistoryIfNeeded(history)
+
 	return history, currentUserMsg, currentToolResults
 }
 
+const kiroMaxHistoryMessages = 50
+
+func truncateHistoryIfNeeded(history []KiroHistoryMessage) []KiroHistoryMessage {
+	if len(history) <= kiroMaxHistoryMessages {
+		return history
+	}
+
+	log.Debugf("kiro-openai: truncating history from %d to %d messages", len(history), kiroMaxHistoryMessages)
+	return history[len(history)-kiroMaxHistoryMessages:]
+}
+
 // buildUserMessageFromOpenAI builds a user message from OpenAI format and extracts tool results
 func buildUserMessageFromOpenAI(msg gjson.Result, modelID, origin string) (KiroUserInputMessage, []KiroToolResult) {
 	content := msg.Get("content")
@@ -677,8 +691,20 @@ func buildAssistantMessageFromOpenAI(msg gjson.Result) KiroAssistantResponseMess
 		}
 	}
 
+	// CRITICAL FIX: Kiro API requires non-empty content for assistant messages
+	// This can happen with compaction requests or error recovery scenarios
+	finalContent := contentBuilder.String()
+	if strings.TrimSpace(finalContent) == "" {
+		if len(toolUses) > 0 {
+			finalContent = "I'll help you with that."
+		} else {
+			finalContent = "I understand."
+		}
+		log.Debugf("kiro-openai: assistant content was empty, using default: %s", finalContent)
+	}
+
 	return KiroAssistantResponseMessage{
-		Content:  contentBuilder.String(),
+		Content:  finalContent,
 		ToolUses: toolUses,
 	}
 }