feat: add minimal style mode toggle for faster diagram generation (#260)

* feat: add minimal style mode toggle for faster diagram generation

- Add Minimal/Styled toggle switch in chat input UI
- When enabled, removes color/style instructions from system prompt
- Faster generation with plain black/white diagrams
- Improves XML auto-fix: handle foreign tags, extra closing tags, trailing garbage
- Fix isMxCellXmlComplete to strip Anthropic function-calling wrappers
- Add debug logging for truncation detection diagnosis

* fix: prevent false XML parse errors during streaming

- Escape unescaped & characters in convertToLegalXml() before DOMParser validation
- Only log console.error for final output, not during streaming updates
- Prevents Next.js dev mode error overlay from showing for expected streaming states

components/chat-input.tsx

@@ -17,7 +17,13 @@ import { HistoryDialog } from "@/components/history-dialog"
 import { ResetWarningModal } from "@/components/reset-warning-modal"
 import { SaveDialog } from "@/components/save-dialog"
 import { Button } from "@/components/ui/button"
+import { Switch } from "@/components/ui/switch"
 import { Textarea } from "@/components/ui/textarea"
+import {
+    Tooltip,
+    TooltipContent,
+    TooltipTrigger,
+} from "@/components/ui/tooltip"
 import { useDiagram } from "@/contexts/diagram-context"
 import { isPdfFile, isTextFile } from "@/lib/pdf-utils"
 import { FilePreviewList } from "./file-preview-list"
@@ -129,6 +135,8 @@ interface ChatInputProps {
     onToggleHistory?: (show: boolean) => void
     sessionId?: string
     error?: Error | null
+    minimalStyle?: boolean
+    onMinimalStyleChange?: (value: boolean) => void
 }
 
 export function ChatInput({
@@ -144,6 +152,8 @@ export function ChatInput({
     onToggleHistory = () => {},
     sessionId,
     error = null,
+    minimalStyle = false,
+    onMinimalStyleChange = () => {},
 }: ChatInputProps) {
     const { diagramHistory, saveDiagramToFile } = useDiagram()
     const textareaRef = useRef<HTMLTextAreaElement>(null)
@@ -343,6 +353,32 @@ export function ChatInput({
                             showHistory={showHistory}
                             onToggleHistory={onToggleHistory}
                         />
+
+                        <Tooltip>
+                            <TooltipTrigger asChild>
+                                <div className="flex items-center gap-1.5">
+                                    <Switch
+                                        id="minimal-style"
+                                        checked={minimalStyle}
+                                        onCheckedChange={onMinimalStyleChange}
+                                        className="scale-75"
+                                    />
+                                    <label
+                                        htmlFor="minimal-style"
+                                        className={`text-xs cursor-pointer select-none ${
+                                            minimalStyle
+                                                ? "text-primary font-medium"
+                                                : "text-muted-foreground"
+                                        }`}
+                                    >
+                                        {minimalStyle ? "Minimal" : "Styled"}
+                                    </label>
+                                </div>
+                            </TooltipTrigger>
+                            <TooltipContent side="top">
+                                Use minimal for faster generation (no colors)
+                            </TooltipContent>
+                        </Tooltip>
                     </div>
 
                     {/* Right actions */}

components/chat-message-display.tsx

@@ -293,11 +293,14 @@ export function ChatMessageDisplay({
                 const parseError = testDoc.querySelector("parsererror")
 
                 if (parseError) {
-                    console.error(
-                        "[ChatMessageDisplay] Malformed XML detected - skipping update",
-                    )
-                    // Only show toast if this is the final XML (not during streaming)
+                    // Use console.warn instead of console.error to avoid triggering
+                    // Next.js dev mode error overlay for expected streaming states
+                    // (partial XML during streaming is normal and will be fixed by subsequent updates)
                     if (showToast) {
+                        // Only log as error and show toast if this is the final XML
+                        console.error(
+                            "[ChatMessageDisplay] Malformed XML detected in final output",
+                        )
                         toast.error(
                             "AI generated invalid diagram XML. Please try regenerating.",
                         )

components/chat-panel.tsx

@@ -145,6 +145,7 @@ export default function ChatPanel({
     const [dailyTokenLimit, setDailyTokenLimit] = useState(0)
     const [tpmLimit, setTpmLimit] = useState(0)
     const [showNewChatDialog, setShowNewChatDialog] = useState(false)
+    const [minimalStyle, setMinimalStyle] = useState(false)
 
     // Check config on mount
     useEffect(() => {
@@ -222,8 +223,16 @@ export default function ChatPanel({
             if (toolCall.toolName === "display_diagram") {
                 const { xml } = toolCall.input as { xml: string }
 
+                // DEBUG: Log raw input to diagnose false truncation detection
+                console.log(
+                    "[display_diagram] XML ending (last 100 chars):",
+                    xml.slice(-100),
+                )
+                console.log("[display_diagram] XML length:", xml.length)
+
                 // Check if XML is truncated (incomplete mxCell indicates truncated output)
                 const isTruncated = !isMxCellXmlComplete(xml)
+                console.log("[display_diagram] isTruncated:", isTruncated)
 
                 if (isTruncated) {
                     // Store the partial XML for continuation via append_diagram
@@ -504,6 +513,10 @@ Continue from EXACTLY where you stopped.`,
                 | Record<string, unknown>
                 | undefined
 
+            // DEBUG: Log finish reason to diagnose truncation
+            console.log("[onFinish] finishReason:", metadata?.finishReason)
+            console.log("[onFinish] metadata:", metadata)
+
             if (metadata) {
                 // Use Number.isFinite to guard against NaN (typeof NaN === 'number' is true)
                 const inputTokens = Number.isFinite(metadata.inputTokens)
@@ -935,6 +948,9 @@ Continue from EXACTLY where you stopped.`,
                         }),
                         ...(config.aiModel && { "x-ai-model": config.aiModel }),
                     }),
+                    ...(minimalStyle && {
+                        "x-minimal-style": "true",
+                    }),
                 },
             },
         )
@@ -1250,6 +1266,8 @@ Continue from EXACTLY where you stopped.`,
                     onToggleHistory={setShowHistory}
                     sessionId={sessionId}
                     error={error}
+                    minimalStyle={minimalStyle}
+                    onMinimalStyleChange={setMinimalStyle}
                 />
             </footer>