refactor: extract diagram tool handlers to dedicated hook

- Create useDiagramToolHandlers hook for display_diagram, edit_diagram, append_diagram
- Remove ~300 lines from chat-panel.tsx
- Remove unused stopRef
- Gate debug console.log statements with DEBUG constant

components/model-config-dialog.tsx

@@ -504,7 +504,7 @@ export function ModelConfigDialog({
                     </div>
 
                     {/* Provider Details (Right Panel) */}
-                    <div className="flex-1 min-w-0 flex flex-col overflow-auto [&::-webkit-scrollbar]:hidden ">
+                    <div className="flex-1 min-w-0 flex flex-col overflow-hidden">
                         {selectedProvider ? (
                             <>
                                 <ScrollArea className="flex-1" ref={scrollRef}>

instrumentation.ts

@@ -14,14 +14,22 @@ export function register() {
         publicKey: process.env.LANGFUSE_PUBLIC_KEY,
         secretKey: process.env.LANGFUSE_SECRET_KEY,
         baseUrl: process.env.LANGFUSE_BASEURL,
-        // Whitelist approach: only export AI-related spans
+        // Filter out Next.js HTTP request spans so AI SDK spans become root traces
         shouldExportSpan: ({ otelSpan }) => {
             const spanName = otelSpan.name
-            // Only export AI SDK spans (ai.*) and our explicit "chat" wrapper
-            if (spanName === "chat" || spanName.startsWith("ai.")) {
-                return true
+            // Skip Next.js HTTP infrastructure spans
+            if (
+                spanName.startsWith("POST") ||
+                spanName.startsWith("GET") ||
+                spanName.startsWith("RSC") ||
+                spanName.includes("BaseServer") ||
+                spanName.includes("handleRequest") ||
+                spanName.includes("resolve page") ||
+                spanName.includes("start response")
+            ) {
+                return false
             }
-            return false
+            return true
         },
     })
 

lib/dynamo-quota-manager.ts

@@ -9,30 +9,6 @@ import {
 // OSS users who don't need quota tracking can simply not set this env var
 const TABLE = process.env.DYNAMODB_QUOTA_TABLE
 const DYNAMODB_REGION = process.env.DYNAMODB_REGION || "ap-northeast-1"
-// Timezone for daily quota reset (e.g., "Asia/Tokyo" for JST midnight reset)
-// Defaults to UTC if not set
-let QUOTA_TIMEZONE = process.env.QUOTA_TIMEZONE || "UTC"
-
-// Validate timezone at module load
-try {
-    new Intl.DateTimeFormat("en-CA", { timeZone: QUOTA_TIMEZONE }).format(
-        new Date(),
-    )
-} catch {
-    console.warn(
-        `[quota] Invalid QUOTA_TIMEZONE "${QUOTA_TIMEZONE}", using UTC`,
-    )
-    QUOTA_TIMEZONE = "UTC"
-}
-
-/**
- * Get today's date string in the configured timezone (YYYY-MM-DD format)
- */
-function getTodayInTimezone(): string {
-    return new Intl.DateTimeFormat("en-CA", {
-        timeZone: QUOTA_TIMEZONE,
-    }).format(new Date())
-}
 
 // Only create client if quota is enabled
 const client = TABLE ? new DynamoDBClient({ region: DYNAMODB_REGION }) : null
@@ -73,67 +49,32 @@ export async function checkAndIncrementRequest(
         return { allowed: true }
     }
 
-    const today = getTodayInTimezone()
+    const today = new Date().toISOString().split("T")[0]
     const currentMinute = Math.floor(Date.now() / 60000).toString()
     const ttl = Math.floor(Date.now() / 1000) + 7 * 24 * 60 * 60
 
     try {
-        // First, try to reset counts if it's a new day (atomic day reset)
-        // This will succeed only if lastResetDate < today or doesn't exist
-        try {
-            await client.send(
-                new UpdateItemCommand({
-                    TableName: TABLE,
-                    Key: { PK: { S: `IP#${ip}` } },
-                    // Reset all counts to 1/0 for the new day
-                    UpdateExpression: `
-                        SET lastResetDate = :today,
-                            dailyReqCount = :one,
-                            dailyTokenCount = :zero,
-                            lastMinute = :minute,
-                            tpmCount = :zero,
-                            #ttl = :ttl
-                    `,
-                    // Only succeed if it's a new day (or new item)
-                    ConditionExpression: `
-                        attribute_not_exists(lastResetDate) OR lastResetDate < :today
-                    `,
-                    ExpressionAttributeNames: { "#ttl": "ttl" },
-                    ExpressionAttributeValues: {
-                        ":today": { S: today },
-                        ":zero": { N: "0" },
-                        ":one": { N: "1" },
-                        ":minute": { S: currentMinute },
-                        ":ttl": { N: String(ttl) },
-                    },
-                }),
-            )
-            // New day reset successful
-            return { allowed: true }
-        } catch (resetError: any) {
-            // If condition failed, it's the same day - continue to increment logic
-            if (!(resetError instanceof ConditionalCheckFailedException)) {
-                throw resetError // Re-throw unexpected errors
-            }
-        }
-
-        // Same day - increment request count with limit checks
+        // Atomic check-and-increment with ConditionExpression
+        // This prevents race conditions by failing if limits are exceeded
         await client.send(
             new UpdateItemCommand({
                 TableName: TABLE,
                 Key: { PK: { S: `IP#${ip}` } },
-                // Increment request count, handle minute boundary for TPM
+                // Reset counts if new day/minute, then increment request count
                 UpdateExpression: `
-                    SET lastMinute = :minute,
+                    SET lastResetDate = :today,
+                        dailyReqCount = if_not_exists(dailyReqCount, :zero) + :one,
+                        dailyTokenCount = if_not_exists(dailyTokenCount, :zero),
+                        lastMinute = :minute,
                         tpmCount = if_not_exists(tpmCount, :zero),
                         #ttl = :ttl
-                    ADD dailyReqCount :one
                 `,
-                // Check all limits before allowing increment
+                // Atomic condition: only succeed if ALL limits pass
+                // Uses attribute_not_exists for new items, then checks limits for existing items
                 ConditionExpression: `
-                    lastResetDate = :today AND
-                    (attribute_not_exists(dailyReqCount) OR dailyReqCount < :reqLimit) AND
-                    (attribute_not_exists(dailyTokenCount) OR dailyTokenCount < :tokenLimit) AND
+                    (attribute_not_exists(lastResetDate) OR lastResetDate < :today OR
+                     ((attribute_not_exists(dailyReqCount) OR dailyReqCount < :reqLimit) AND
+                      (attribute_not_exists(dailyTokenCount) OR dailyTokenCount < :tokenLimit))) AND
                     (attribute_not_exists(lastMinute) OR lastMinute <> :minute OR
                      attribute_not_exists(tpmCount) OR tpmCount < :tpmLimit)
                 `,