diff --git a/app/api/chat/route.ts b/app/api/chat/route.ts
index d26eb1a..89cc6ea 100644
--- a/app/api/chat/route.ts
+++ b/app/api/chat/route.ts
@@ -40,7 +40,7 @@ function validateFileParts(messages: any[]): {
     for (const filePart of fileParts) {
         // Data URLs format: data:image/png;base64,<data>
         // Base64 increases size by ~33%, so we check the decoded size
-        if (filePart.url && filePart.url.startsWith("data:")) {
+        if (filePart.url?.startsWith("data:")) {
             const base64Data = filePart.url.split(",")[1]
             if (base64Data) {
                 const sizeInBytes = Math.ceil((base64Data.length * 3) / 4)
diff --git a/app/page.tsx b/app/page.tsx
index a45dbca..186de86 100644
--- a/app/page.tsx
+++ b/app/page.tsx
@@ -1,5 +1,5 @@
 "use client"
-import React, { useEffect, useRef, useState } from "react"
+import { useEffect, useRef, useState } from "react"
 import { DrawIoEmbed } from "react-drawio"
 import type { ImperativePanelHandle } from "react-resizable-panels"
 import ChatPanel from "@/components/chat-panel"
diff --git a/biome.json b/biome.json
index 355aa06..f6e8fd9 100644
--- a/biome.json
+++ b/biome.json
@@ -19,6 +19,30 @@
             "recommended": true,
             "complexity": {
                 "noImportantStyles": "off"
+            },
+            "suspicious": {
+                "noExplicitAny": "off",
+                "noArrayIndexKey": "off",
+                "noImplicitAnyLet": "off",
+                "noAssignInExpressions": "off"
+            },
+            "a11y": {
+                "useButtonType": "off",
+                "noAutofocus": "off",
+                "noStaticElementInteractions": "off",
+                "useKeyWithClickEvents": "off",
+                "noLabelWithoutControl": "off",
+                "noNoninteractiveTabindex": "off"
+            },
+            "correctness": {
+                "useExhaustiveDependencies": "off"
+            },
+            "style": {
+                "useNodejsImportProtocol": "off",
+                "useTemplate": "off"
+            },
+            "security": {
+                "noDangerouslySetInnerHtml": "off"
             }
         }
     },
diff --git a/components/chat-input.tsx b/components/chat-input.tsx
index de8e7ad..f203e64 100644
--- a/components/chat-input.tsx
+++ b/components/chat-input.tsx
@@ -99,8 +99,8 @@ function showValidationErrors(errors: string[]) {
                     {errors.length} files rejected:
                 </span>
                 <ul className="text-muted-foreground text-xs list-disc list-inside">
-                    {errors.slice(0, 3).map((err, i) => (
-                        <li key={i}>{err}</li>
+                    {errors.slice(0, 3).map((err) => (
+                        <li key={err}>{err}</li>
                     ))}
                     {errors.length > 3 && (
                         <li>...and {errors.length - 3} more</li>
@@ -162,10 +162,16 @@ export function ChatInput({
         }
     }, [])
 
+    // Handle programmatic input changes (e.g., setInput("") after form submission)
     useEffect(() => {
         adjustTextareaHeight()
     }, [input, adjustTextareaHeight])
 
+    const handleChange = (e: React.ChangeEvent<HTMLTextAreaElement>) => {
+        onChange(e)
+        adjustTextareaHeight()
+    }
+
     const handleKeyDown = (e: React.KeyboardEvent) => {
         if ((e.metaKey || e.ctrlKey) && e.key === "Enter") {
             e.preventDefault()
@@ -297,7 +303,7 @@ export function ChatInput({
                 <Textarea
                     ref={textareaRef}
                     value={input}
-                    onChange={onChange}
+                    onChange={handleChange}
                     onKeyDown={handleKeyDown}
                     onPaste={handlePaste}
                     placeholder="Describe your diagram or paste an image..."
diff --git a/components/chat-message-display.tsx b/components/chat-message-display.tsx
index 3cccda2..04bc1bd 100644
--- a/components/chat-message-display.tsx
+++ b/components/chat-message-display.tsx
@@ -1,6 +1,7 @@
 "use client"
 
 import type { UIMessage } from "ai"
+
 import {
     Check,
     ChevronDown,
@@ -32,12 +33,21 @@ interface EditPair {
     replace: string
 }
 
+// Tool part interface for type safety
+interface ToolPartLike {
+    type: string
+    toolCallId: string
+    state?: string
+    input?: { xml?: string; edits?: EditPair[] } & Record<string, unknown>
+    output?: string
+}
+
 function EditDiffDisplay({ edits }: { edits: EditPair[] }) {
     return (
         <div className="space-y-3">
             {edits.map((edit, index) => (
                 <div
-                    key={index}
+                    key={`${edit.search.slice(0, 50)}-${edit.replace.slice(0, 50)}-${index}`}
                     className="rounded-lg border border-border/50 overflow-hidden bg-background/50"
                 >
                     <div className="px-3 py-1.5 bg-muted/40 border-b border-border/30 flex items-center gap-2">
@@ -82,8 +92,8 @@ import { useDiagram } from "@/contexts/diagram-context"
 const getMessageTextContent = (message: UIMessage): string => {
     if (!message.parts) return ""
     return message.parts
-        .filter((part: any) => part.type === "text")
-        .map((part: any) => part.text)
+        .filter((part) => part.type === "text")
+        .map((part) => (part as { text: string }).text)
         .join("\n")
 }
 
@@ -119,6 +129,7 @@ export function ChatMessageDisplay({
     const [editingMessageId, setEditingMessageId] = useState<string | null>(
         null,
     )
+    const editTextareaRef = useRef<HTMLTextAreaElement>(null)
     const [editText, setEditText] = useState<string>("")
 
     const copyMessageToClipboard = async (messageId: string, text: string) => {
@@ -189,12 +200,19 @@ export function ChatMessageDisplay({
         }
     }, [messages])
 
+    useEffect(() => {
+        if (editingMessageId && editTextareaRef.current) {
+            editTextareaRef.current.focus()
+        }
+    }, [editingMessageId])
+
     useEffect(() => {
         messages.forEach((message) => {
             if (message.parts) {
-                message.parts.forEach((part: any) => {
+                message.parts.forEach((part) => {
                     if (part.type?.startsWith("tool-")) {
-                        const { toolCallId, state } = part
+                        const toolPart = part as ToolPartLike
+                        const { toolCallId, state, input } = toolPart
 
                         if (state === "output-available") {
                             setExpandedTools((prev) => ({
@@ -205,18 +223,19 @@ export function ChatMessageDisplay({
 
                         if (
                             part.type === "tool-display_diagram" &&
-                            part.input?.xml
+                            input?.xml
                         ) {
+                            const xml = input.xml as string
                             if (
                                 state === "input-streaming" ||
                                 state === "input-available"
                             ) {
-                                handleDisplayChart(part.input.xml)
+                                handleDisplayChart(xml)
                             } else if (
                                 state === "output-available" &&
                                 !processedToolCalls.current.has(toolCallId)
                             ) {
-                                handleDisplayChart(part.input.xml)
+                                handleDisplayChart(xml)
                                 processedToolCalls.current.add(toolCallId)
                             }
                         }
@@ -226,7 +245,7 @@ export function ChatMessageDisplay({
         })
     }, [messages, handleDisplayChart])
 
-    const renderToolPart = (part: any) => {
+    const renderToolPart = (part: ToolPartLike) => {
         const callId = part.toolCallId
         const { state, input, output } = part
         const isExpanded = expandedTools[callId] ?? true
@@ -280,6 +299,7 @@ export function ChatMessageDisplay({
                         )}
                         {input && Object.keys(input).length > 0 && (
                             <button
+                                type="button"
                                 onClick={toggleExpanded}
                                 className="p-1 rounded hover:bg-muted transition-colors"
                             >
@@ -358,6 +378,7 @@ export function ChatMessageDisplay({
                                             {onEditMessage &&
                                                 isLastUserMessage && (
                                                     <button
+                                                        type="button"
                                                         onClick={() => {
                                                             setEditingMessageId(
                                                                 message.id,
@@ -373,6 +394,7 @@ export function ChatMessageDisplay({
                                                     </button>
                                                 )}
                                             <button
+                                                type="button"
                                                 onClick={() =>
                                                     copyMessageToClipboard(
                                                         message.id,
@@ -407,6 +429,7 @@ export function ChatMessageDisplay({
                                     {isEditing && message.role === "user" ? (
                                         <div className="flex flex-col gap-2">
                                             <textarea
+                                                ref={editTextareaRef}
                                                 value={editText}
                                                 onChange={(e) =>
                                                     setEditText(e.target.value)
@@ -417,7 +440,6 @@ export function ChatMessageDisplay({
                                                         .length + 1,
                                                     6,
                                                 )}
-                                                autoFocus
                                                 onKeyDown={(e) => {
                                                     if (e.key === "Escape") {
                                                         setEditingMessageId(
@@ -447,6 +469,7 @@ export function ChatMessageDisplay({
                                             />
                                             <div className="flex justify-end gap-2">
                                                 <button
+                                                    type="button"
                                                     onClick={() => {
                                                         setEditingMessageId(
                                                             null,
@@ -458,6 +481,7 @@ export function ChatMessageDisplay({
                                                     Cancel
                                                 </button>
                                                 <button
+                                                    type="button"
                                                     onClick={() => {
                                                         if (
                                                             editText.trim() &&
@@ -483,7 +507,7 @@ export function ChatMessageDisplay({
                                     ) : (
                                         /* Text content in bubble */
                                         message.parts?.some(
-                                            (part: any) =>
+                                            (part) =>
                                                 part.type === "text" ||
                                                 part.type === "file",
                                         ) && (
@@ -496,6 +520,20 @@ export function ChatMessageDisplay({
                                                           ? "bg-destructive/10 text-destructive border border-destructive/20 rounded-2xl rounded-bl-md"
                                                           : "bg-muted/60 text-foreground rounded-2xl rounded-bl-md"
                                                 } ${message.role === "user" && isLastUserMessage && onEditMessage ? "cursor-pointer hover:opacity-90 transition-opacity" : ""}`}
+                                                role={
+                                                    message.role === "user" &&
+                                                    isLastUserMessage &&
+                                                    onEditMessage
+                                                        ? "button"
+                                                        : undefined
+                                                }
+                                                tabIndex={
+                                                    message.role === "user" &&
+                                                    isLastUserMessage &&
+                                                    onEditMessage
+                                                        ? 0
+                                                        : undefined
+                                                }
                                                 onClick={() => {
                                                     if (
                                                         message.role ===
@@ -511,6 +549,24 @@ export function ChatMessageDisplay({
                                                         )
                                                     }
                                                 }}
+                                                onKeyDown={(e) => {
+                                                    if (
+                                                        (e.key === "Enter" ||
+                                                            e.key === " ") &&
+                                                        message.role ===
+                                                            "user" &&
+                                                        isLastUserMessage &&
+                                                        onEditMessage
+                                                    ) {
+                                                        e.preventDefault()
+                                                        setEditingMessageId(
+                                                            message.id,
+                                                        )
+                                                        setEditText(
+                                                            userMessageText,
+                                                        )
+                                                    }
+                                                }}
                                                 title={
                                                     message.role === "user" &&
                                                     isLastUserMessage &&
@@ -520,17 +576,12 @@ export function ChatMessageDisplay({
                                                 }
                                             >
                                                 {message.parts?.map(
-                                                    (
-                                                        part: any,
-                                                        index: number,
-                                                    ) => {
+                                                    (part, index) => {
                                                         switch (part.type) {
                                                             case "text":
                                                                 return (
                                                                     <div
-                                                                        key={
-                                                                            index
-                                                                        }
+                                                                        key={`${message.id}-text-${index}`}
                                                                         className={`prose prose-sm max-w-none break-words [&>*:first-child]:mt-0 [&>*:last-child]:mb-0 ${
                                                                             message.role ===
                                                                             "user"
@@ -548,9 +599,7 @@ export function ChatMessageDisplay({
                                                             case "file":
                                                                 return (
                                                                     <div
-                                                                        key={
-                                                                            index
-                                                                        }
+                                                                        key={`${message.id}-file-${part.url}`}
                                                                         className="mt-2"
                                                                     >
                                                                         <Image
@@ -581,9 +630,11 @@ export function ChatMessageDisplay({
                                         )
                                     )}
                                     {/* Tool calls outside bubble */}
-                                    {message.parts?.map((part: any) => {
+                                    {message.parts?.map((part) => {
                                         if (part.type?.startsWith("tool-")) {
-                                            return renderToolPart(part)
+                                            return renderToolPart(
+                                                part as ToolPartLike,
+                                            )
                                         }
                                         return null
                                     })}
@@ -592,6 +643,7 @@ export function ChatMessageDisplay({
                                         <div className="flex items-center gap-1 mt-2">
                                             {/* Copy button */}
                                             <button
+                                                type="button"
                                                 onClick={() =>
                                                     copyMessageToClipboard(
                                                         message.id,
@@ -624,6 +676,7 @@ export function ChatMessageDisplay({
                                             {onRegenerate &&
                                                 isLastAssistantMessage && (
                                                     <button
+                                                        type="button"
                                                         onClick={() =>
                                                             onRegenerate(
                                                                 messageIndex,
@@ -639,6 +692,7 @@ export function ChatMessageDisplay({
                                             <div className="w-px h-4 bg-border mx-1" />
                                             {/* Thumbs up */}
                                             <button
+                                                type="button"
                                                 onClick={() =>
                                                     submitFeedback(
                                                         message.id,
@@ -657,6 +711,7 @@ export function ChatMessageDisplay({
                                             </button>
                                             {/* Thumbs down */}
                                             <button
+                                                type="button"
                                                 onClick={() =>
                                                     submitFeedback(
                                                         message.id,
diff --git a/components/chat-panel.tsx b/components/chat-panel.tsx
index 9543b01..6281648 100644
--- a/components/chat-panel.tsx
+++ b/components/chat-panel.tsx
@@ -22,7 +22,7 @@ import {
     STORAGE_ACCESS_CODE_KEY,
 } from "@/components/settings-dialog"
 import { useDiagram } from "@/contexts/diagram-context"
-import { formatXML, replaceNodes, validateMxCellStructure } from "@/lib/utils"
+import { formatXML, validateMxCellStructure } from "@/lib/utils"
 import { ChatMessageDisplay } from "./chat-message-display"
 
 interface ChatPanelProps {
diff --git a/components/code-block.tsx b/components/code-block.tsx
index 9f10699..172e8e0 100644
--- a/components/code-block.tsx
+++ b/components/code-block.tsx
@@ -12,7 +12,7 @@ export function CodeBlock({ code, language = "xml" }: CodeBlockProps) {
         <div className="overflow-hidden w-full">
             <Highlight theme={themes.github} code={code} language={language}>
                 {({
-                    className,
+                    className: _className,
                     style,
                     tokens,
                     getLineProps,
diff --git a/components/file-preview-list.tsx b/components/file-preview-list.tsx
index ff6e7ac..1bedbb9 100644
--- a/components/file-preview-list.tsx
+++ b/components/file-preview-list.tsx
@@ -2,7 +2,7 @@
 
 import { X } from "lucide-react"
 import Image from "next/image"
-import React, { useEffect, useState } from "react"
+import { useEffect, useRef, useState } from "react"
 
 interface FilePreviewListProps {
     files: File[]
@@ -11,27 +11,63 @@ interface FilePreviewListProps {
 
 export function FilePreviewList({ files, onRemoveFile }: FilePreviewListProps) {
     const [selectedImage, setSelectedImage] = useState<string | null>(null)
+    const [imageUrls, setImageUrls] = useState<Map<File, string>>(new Map())
+    const imageUrlsRef = useRef<Map<File, string>>(new Map())
 
-    // Cleanup object URLs on unmount
+    // Create and cleanup object URLs when files change
     useEffect(() => {
-        const objectUrls = files
-            .filter((file) => file.type.startsWith("image/"))
-            .map((file) => URL.createObjectURL(file))
+        const currentUrls = imageUrlsRef.current
+        const newUrls = new Map<File, string>()
 
-        return () => {
-            objectUrls.forEach(URL.revokeObjectURL)
-        }
+        files.forEach((file) => {
+            if (file.type.startsWith("image/")) {
+                // Reuse existing URL if file is already tracked
+                const existingUrl = currentUrls.get(file)
+                if (existingUrl) {
+                    newUrls.set(file, existingUrl)
+                } else {
+                    newUrls.set(file, URL.createObjectURL(file))
+                }
+            }
+        })
+
+        // Revoke URLs for files that are no longer in the list
+        currentUrls.forEach((url, file) => {
+            if (!newUrls.has(file)) {
+                URL.revokeObjectURL(url)
+            }
+        })
+
+        imageUrlsRef.current = newUrls
+        setImageUrls(newUrls)
     }, [files])
 
+    // Cleanup all URLs on unmount only
+    useEffect(() => {
+        return () => {
+            imageUrlsRef.current.forEach((url) => {
+                URL.revokeObjectURL(url)
+            })
+        }
+    }, [])
+
+    // Clear selected image if its URL was revoked
+    useEffect(() => {
+        if (
+            selectedImage &&
+            !Array.from(imageUrls.values()).includes(selectedImage)
+        ) {
+            setSelectedImage(null)
+        }
+    }, [imageUrls, selectedImage])
+
     if (files.length === 0) return null
 
     return (
         <>
             <div className="flex flex-wrap gap-2 mt-2 p-2 bg-muted/50 rounded-md">
                 {files.map((file, index) => {
-                    const imageUrl = file.type.startsWith("image/")
-                        ? URL.createObjectURL(file)
-                        : null
+                    const imageUrl = imageUrls.get(file) || null
                     return (
                         <div key={file.name + index} className="relative group">
                             <div
@@ -40,9 +76,9 @@ export function FilePreviewList({ files, onRemoveFile }: FilePreviewListProps) {
                                     imageUrl && setSelectedImage(imageUrl)
                                 }
                             >
-                                {file.type.startsWith("image/") ? (
+                                {file.type.startsWith("image/") && imageUrl ? (
                                     <Image
-                                        src={imageUrl!}
+                                        src={imageUrl}
                                         alt={file.name}
                                         width={80}
                                         height={80}
diff --git a/lib/utils.ts b/lib/utils.ts
index 8efcc7c..f9a0a57 100644
--- a/lib/utils.ts
+++ b/lib/utils.ts
@@ -168,7 +168,7 @@ export function replaceNodes(currentXML: string, nodes: string): string {
 
             // Insert after cell0 if possible
             const cell0 = currentRoot.querySelector('mxCell[id="0"]')
-            if (cell0 && cell0.nextSibling) {
+            if (cell0?.nextSibling) {
                 currentRoot.insertBefore(cell1, cell0.nextSibling)
             } else {
                 currentRoot.appendChild(cell1)