refactor: remove Langfuse observability integration

- Delete lib/langfuse.ts, instrumentation.ts
- Remove API routes: log-save, log-feedback
- Remove feedback buttons (thumbs up/down) from chat
- Remove sessionId tracking throughout codebase
- Remove @langfuse/*, @opentelemetry dependencies
- Clean up env.example

components/chat-input.tsx

@@ -29,7 +29,6 @@ interface ChatInputProps {
     onFileChange?: (files: File[]) => void;
     showHistory?: boolean;
     onToggleHistory?: (show: boolean) => void;
-    sessionId?: string;
 }
 
 export function ChatInput({
@@ -42,7 +41,6 @@ export function ChatInput({
     onFileChange = () => {},
     showHistory = false,
     onToggleHistory = () => {},
-    sessionId,
 }: ChatInputProps) {
     const { diagramHistory, saveDiagramToFile } = useDiagram();
     const textareaRef = useRef<HTMLTextAreaElement>(null);
@@ -251,7 +249,7 @@ export function ChatInput({
                         <SaveDialog
                             open={showSaveDialog}
                             onOpenChange={setShowSaveDialog}
-                            onSave={(filename, format) => saveDiagramToFile(filename, format, sessionId)}
+                            onSave={(filename, format) => saveDiagramToFile(filename, format)}
                             defaultFilename={`diagram-${new Date().toISOString().slice(0, 10)}`}
                         />
 

components/chat-message-display.tsx

@@ -6,7 +6,7 @@ import { ScrollArea } from "@/components/ui/scroll-area";
 import ExamplePanel from "./chat-example-panel";
 import { UIMessage } from "ai";
 import { convertToLegalXml, replaceNodes, validateMxCellStructure } from "@/lib/utils";
-import { Copy, Check, X, ChevronDown, ChevronUp, Cpu, Minus, Plus, ThumbsUp, ThumbsDown, RotateCcw, Pencil } from "lucide-react";
+import { Copy, Check, X, ChevronDown, ChevronUp, Cpu, Minus, Plus, RotateCcw, Pencil } from "lucide-react";
 import { CodeBlock } from "./code-block";
 
 interface EditPair {
@@ -67,7 +67,6 @@ interface ChatMessageDisplayProps {
     error?: Error | null;
     setInput: (input: string) => void;
     setFiles: (files: File[]) => void;
-    sessionId?: string;
     onRegenerate?: (messageIndex: number) => void;
     onEditMessage?: (messageIndex: number, newText: string) => void;
 }
@@ -77,7 +76,6 @@ export function ChatMessageDisplay({
     error,
     setInput,
     setFiles,
-    sessionId,
     onRegenerate,
     onEditMessage,
 }: ChatMessageDisplayProps) {
@@ -90,7 +88,6 @@ export function ChatMessageDisplay({
     );
     const [copiedMessageId, setCopiedMessageId] = useState<string | null>(null);
     const [copyFailedMessageId, setCopyFailedMessageId] = useState<string | null>(null);
-    const [feedback, setFeedback] = useState<Record<string, "good" | "bad">>({});
     const [editingMessageId, setEditingMessageId] = useState<string | null>(null);
     const [editText, setEditText] = useState<string>("");
 
@@ -106,34 +103,6 @@ export function ChatMessageDisplay({
         }
     };
 
-    const submitFeedback = async (messageId: string, value: "good" | "bad") => {
-        // Toggle off if already selected
-        if (feedback[messageId] === value) {
-            setFeedback((prev) => {
-                const next = { ...prev };
-                delete next[messageId];
-                return next;
-            });
-            return;
-        }
-
-        setFeedback((prev) => ({ ...prev, [messageId]: value }));
-
-        try {
-            await fetch("/api/log-feedback", {
-                method: "POST",
-                headers: { "Content-Type": "application/json" },
-                body: JSON.stringify({
-                    messageId,
-                    feedback: value,
-                    sessionId,
-                }),
-            });
-        } catch (error) {
-            console.warn("Failed to log feedback:", error);
-        }
-    };
-
     const handleDisplayChart = useCallback(
         (xml: string) => {
             const currentXml = xml || "";
@@ -467,32 +436,6 @@ export function ChatMessageDisplay({
                                                     <RotateCcw className="h-3.5 w-3.5" />
                                                 </button>
                                             )}
-                                            {/* Divider */}
-                                            <div className="w-px h-4 bg-border mx-1" />
-                                            {/* Thumbs up */}
-                                            <button
-                                                onClick={() => submitFeedback(message.id, "good")}
-                                                className={`p-1.5 rounded-lg transition-colors ${
-                                                    feedback[message.id] === "good"
-                                                        ? "text-green-600 bg-green-100"
-                                                        : "text-muted-foreground/60 hover:text-green-600 hover:bg-green-50"
-                                                }`}
-                                                title="Good response"
-                                            >
-                                                <ThumbsUp className="h-3.5 w-3.5" />
-                                            </button>
-                                            {/* Thumbs down */}
-                                            <button
-                                                onClick={() => submitFeedback(message.id, "bad")}
-                                                className={`p-1.5 rounded-lg transition-colors ${
-                                                    feedback[message.id] === "bad"
-                                                        ? "text-red-600 bg-red-100"
-                                                        : "text-muted-foreground/60 hover:text-red-600 hover:bg-red-50"
-                                                }`}
-                                                title="Bad response"
-                                            >
-                                                <ThumbsDown className="h-3.5 w-3.5" />
-                                            </button>
                                         </div>
                                     )}
                                 </div>

components/chat-panel.tsx

@@ -62,9 +62,6 @@ export default function ChatPanel({
     const [showHistory, setShowHistory] = useState(false);
     const [input, setInput] = useState("");
 
-    // Generate a unique session ID for Langfuse tracing
-    const [sessionId, setSessionId] = useState(() => `session-${Date.now()}-${Math.random().toString(36).slice(2, 9)}`);
-
     // Store XML snapshots for each user message (keyed by message index)
     const xmlSnapshotsRef = useRef<Map<number, string>>(new Map());
 
@@ -208,7 +205,6 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
                     {
                         body: {
                             xml: chartXml,
-                            sessionId,
                         },
                     }
                 );
@@ -283,7 +279,6 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
             {
                 body: {
                     xml: savedXml,
-                    sessionId,
                 },
             }
         );
@@ -337,7 +332,6 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
             {
                 body: {
                     xml: savedXml,
-                    sessionId,
                 },
             }
         );
@@ -424,7 +418,6 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
                     error={error}
                     setInput={setInput}
                     setFiles={handleFileChange}
-                    sessionId={sessionId}
                     onRegenerate={handleRegenerate}
                     onEditMessage={handleEditMessage}
                 />
@@ -440,14 +433,12 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
                     onClearChat={() => {
                         setMessages([]);
                         clearDiagram();
-                        setSessionId(`session-${Date.now()}-${Math.random().toString(36).slice(2, 9)}`);
                         xmlSnapshotsRef.current.clear();
                     }}
                     files={files}
                     onFileChange={handleFileChange}
                     showHistory={showHistory}
                     onToggleHistory={setShowHistory}
-                    sessionId={sessionId}
                 />
             </footer>
         </div>