fix: always send maxOutputTokens; default 16000

Unset does not mean the model's maximum — the provider fills in its own, and
Bedrock's is 4096 (measured: converse with no inferenceConfig on
us.anthropic.claude-opus-5 returns stopReason=max_tokens at exactly 4096).

A 30-cell diagram is ~3000 tokens of XML, so anything larger arrived as truncated
JSON and nothing reached the canvas. Small diagrams fitted, which made it look
intermittent.

app/api/chat/route.ts

@@ -493,9 +493,9 @@ IMPORTANT: The "Current diagram XML" is the SINGLE SOURCE OF TRUTH for what's on
     const result = streamText({
         model,
         abortSignal: req.signal,
-        ...(process.env.MAX_OUTPUT_TOKENS && {
-            maxOutputTokens: parseInt(process.env.MAX_OUTPUT_TOKENS, 10),
-        }),
+        // Must be sent: unset means the provider's own default, and Bedrock's is 4096 —
+        // enough for a small diagram, so larger ones were cut off mid-attribute.
+        maxOutputTokens: Number(process.env.MAX_OUTPUT_TOKENS) || 16000,
         stopWhen: stepCountIs(5),
         // Repair truncated tool calls when maxOutputTokens is reached mid-JSON
         experimental_repairToolCall: async ({ toolCall, error }) => {

components/chat-panel.tsx

@@ -830,10 +830,6 @@ export default function ChatPanel({
                 let chartXml = await onFetchChart()
                 chartXml = formatXML(chartXml)
 
-                // Update ref directly to avoid race condition with React's async state update
-                // This ensures edit_diagram has the correct XML before AI responds
-                chartXMLRef.current = chartXml
-
                 // Build user text by concatenating input with pre-extracted text
                 // (Backend only reads first text part, so we must combine them)
                 const parts: any[] = []

contexts/diagram-context.tsx

@@ -2,7 +2,7 @@
 
 import type React from "react"
 import { createContext, useContext, useEffect, useRef, useState } from "react"
-import type { DrawIoEmbedRef } from "react-drawio"
+import type { DrawIoEmbedRef, EventExport } from "react-drawio"
 import { toast } from "sonner"
 import type { ExportFormat } from "@/components/save-dialog"
 import { getApiEndpoint } from "@/lib/base-path"
@@ -22,7 +22,7 @@ interface DiagramContextType {
     handleExportWithoutHistory: () => void
     resolverRef: React.MutableRefObject<((value: string) => void) | null>
     drawioRef: React.MutableRefObject<DrawIoEmbedRef | null>
-    handleDiagramExport: (data: any) => void
+    handleDiagramExport: (data: EventExport) => void
     handleDiagramAutoSave: (data: { xml?: string }) => void
     clearDiagram: () => void
     saveDiagramToFile: (
@@ -83,7 +83,7 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
 
     // Track if we're expecting an export for file save (stores raw export data)
     const saveResolverRef = useRef<{
-        resolver: ((data: string) => void) | null
+        resolver: ((data: string, fullDiagramXML?: string) => void) | null
         format: ExportFormat | null
     }>({ resolver: null, format: null })
 
@@ -204,7 +204,7 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
         return null
     }
 
-    const handleDiagramExport = (data: any) => {
+    const handleDiagramExport = (data: EventExport) => {
         // Handle PNG export for VLM validation
         if (pngResolverRef.current && data.data?.startsWith("data:image/png")) {
             pngResolverRef.current(data.data)
@@ -215,7 +215,7 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
         // Handle save to file if requested (process raw data before extraction)
         if (saveResolverRef.current.resolver) {
             const format = saveResolverRef.current.format
-            saveResolverRef.current.resolver(data.data)
+            saveResolverRef.current.resolver(data.data, data.xml)
             saveResolverRef.current = { resolver: null, format: null }
             // For non-xmlsvg formats, skip XML extraction as it will fail
             // Only drawio (which uses xmlsvg internally) has the content attribute
@@ -225,8 +225,11 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
             }
         }
 
+        // Don't write chartXML here: exports don't change the diagram, and
+        // data.xml from xmlsvg exports has compressed <diagram> payloads that
+        // would break edit_diagram/display_diagram. Autosave keeps chartXML
+        // up to date with the full uncompressed multi-page document (#879).
         const extractedXML = extractDiagramXML(data.data)
-        setChartXML(extractedXML)
         setLatestSvg(data.data)
 
         // Only add to history if this was a user-initiated export
@@ -288,14 +291,16 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
 
         // Set up the resolver before triggering export
         saveResolverRef.current = {
-            resolver: (exportData: string) => {
+            resolver: (exportData: string, fullDiagramXML?: string) => {
                 let fileContent: string | Blob
                 let mimeType: string
                 let extension: string
 
                 if (format === "drawio") {
-                    // Extract XML from SVG for .drawio format
-                    const xml = extractDiagramXML(exportData)
+                    // Prefer the complete document from the export event so all pages are saved.
+                    const xml = fullDiagramXML?.trim()
+                        ? fullDiagramXML
+                        : extractDiagramXML(exportData)
                     let xmlContent = xml
                     if (!xml.includes("<mxfile")) {
                         xmlContent = `<mxfile><diagram name="Page-1" id="page-1">${xml}</diagram></mxfile>`

env.example

@@ -11,6 +11,9 @@ AI_PROVIDER=bedrock
 # Example: AI_MODEL=doubao-seed-1-8-251215,doubao-seed-1-6-flash,doubao-seed-1-6-pro
 AI_MODEL=global.anthropic.claude-sonnet-4-5-20250929-v1:0
 
+# Output limit, all providers (default: 16000). Raise it if large diagrams arrive cut off.
+# MAX_OUTPUT_TOKENS=16000
+
 # AWS Bedrock Configuration
 # AWS_REGION=us-east-1
 # AWS_ACCESS_KEY_ID=your-access-key-id