diff --git a/app/(docs)/@docs/[lang]/[pageId]/chatForm.tsx b/app/(docs)/@docs/[lang]/[pageId]/chatForm.tsx
index 349f07bb..f38ce7ee 100644
--- a/app/(docs)/@docs/[lang]/[pageId]/chatForm.tsx
+++ b/app/(docs)/@docs/[lang]/[pageId]/chatForm.tsx
@@ -7,9 +7,8 @@ import { useState, FormEvent, useEffect } from "react";
 //   QuestionExampleParams,
 // } from "../actions/questionExample";
 // import { getLanguageName } from "../pagesList";
-import { DynamicMarkdownSection } from "./pageContent";
 import { useEmbedContext } from "@/terminal/embedContext";
-import { PagePath } from "@/lib/docs";
+import { DynamicMarkdownSection, PagePath } from "@/lib/docs";
 import { useRouter } from "next/navigation";
 import { ChatStreamEvent } from "@/api/chat/route";
 import { useStreamingChatContext } from "@/(docs)/streamingChatContext";
diff --git a/app/(docs)/@docs/[lang]/[pageId]/pageContent.tsx b/app/(docs)/@docs/[lang]/[pageId]/pageContent.tsx
index 2e54858b..f2daec28 100644
--- a/app/(docs)/@docs/[lang]/[pageId]/pageContent.tsx
+++ b/app/(docs)/@docs/[lang]/[pageId]/pageContent.tsx
@@ -7,33 +7,18 @@ import { useSidebarMdContext } from "@/sidebar";
 import clsx from "clsx";
 import { PageTransition } from "./pageTransition";
 import {
+  DynamicMarkdownSection,
   LanguageEntry,
   MarkdownSection,
   PageEntry,
   PagePath,
   SectionId,
 } from "@/lib/docs";
-import { ReplacedRange } from "@/markdown/multiHighlight";
 import { Heading } from "@/markdown/heading";
 import Link from "next/link";
 import { useChatId } from "@/(docs)/chatAreaState";
 import { ChatWithMessages } from "@/lib/chatHistory";
 
-/**
- * MarkdownSectionに追加で、動的な情報を持たせる
- */
-export interface DynamicMarkdownSection extends MarkdownSection {
-  /**
-   * ユーザーが今そのセクションを読んでいるかどうか
-   */
-  inView: boolean;
-  /**
-   * チャットの会話を元にAIが書き換えた後の内容
-   */
-  replacedContent: string;
-  replacedRange: ReplacedRange[];
-}
-
 interface PageContentProps {
   splitMdContent: MarkdownSection[];
   langEntry: LanguageEntry;
diff --git a/app/actions/deleteChat.ts b/app/actions/deleteChat.ts
index 32ce131f..65ec9507 100644
--- a/app/actions/deleteChat.ts
+++ b/app/actions/deleteChat.ts
@@ -1,8 +1,10 @@
 "use server";
 
+import { z } from "zod";
 import { deleteChat, initContext } from "@/lib/chatHistory";
 
 export async function deleteChatAction(chatId: string) {
+  chatId = z.uuid().parse(chatId);
   const ctx = await initContext();
   await deleteChat(chatId, ctx);
 }
diff --git a/app/actions/getRedirectFromChat.ts b/app/actions/getRedirectFromChat.ts
index 7e9be601..57e69c8d 100644
--- a/app/actions/getRedirectFromChat.ts
+++ b/app/actions/getRedirectFromChat.ts
@@ -1,11 +1,14 @@
 "use server";
 
+import { z } from "zod";
 import { initContext } from "@/lib/chatHistory";
 import { LangId, PageSlug } from "@/lib/docs";
 import { chat, section } from "@/schema/chat";
 import { and, eq } from "drizzle-orm";
 
 export async function getRedirectFromChat(chatId: string): Promise<string> {
+  chatId = z.uuid().parse(chatId);
+  
   const { drizzle, userId } = await initContext();
   if (!userId) {
     throw new Error("Not authenticated");
diff --git a/app/api/chat/route.ts b/app/api/chat/route.ts
index e37708a1..dd0beca0 100644
--- a/app/api/chat/route.ts
+++ b/app/api/chat/route.ts
@@ -6,18 +6,27 @@ import {
   CreateChatDiff,
   initContext,
 } from "@/lib/chatHistory";
-import { getPagesList, introSectionId, PagePath, SectionId } from "@/lib/docs";
-import { DynamicMarkdownSection } from "@/(docs)/@docs/[lang]/[pageId]/pageContent";
-import { ReplCommand, ReplOutput } from "@my-code/runtime/interface";
+import {
+  DynamicMarkdownSectionSchema,
+  getPagesList,
+  introSectionId,
+  PagePathSchema,
+  SectionId,
+} from "@/lib/docs";
+import {
+  ReplCommandSchema,
+  ReplOutputSchema,
+} from "@my-code/runtime/interface";
+import { z } from "zod";
 
-type ChatParams = {
-  path: PagePath;
-  userQuestion: string;
-  sectionContent: DynamicMarkdownSection[];
-  replOutputs: Record<string, ReplCommand[]>;
-  files: Record<string, string>;
-  execResults: Record<string, ReplOutput[]>;
-};
+const ChatParamsSchema = z.object({
+  path: PagePathSchema,
+  userQuestion: z.string().min(1),
+  sectionContent: z.array(DynamicMarkdownSectionSchema),
+  replOutputs: z.record(z.string(), z.array(ReplCommandSchema)),
+  files: z.record(z.string(), z.string()),
+  execResults: z.record(z.string(), z.array(ReplOutputSchema)),
+});
 
 export type ChatStreamEvent =
   | { type: "chat"; chatId: string; sectionId: string }
@@ -31,9 +40,18 @@ export async function POST(request: NextRequest) {
     return new Response("Unauthorized", { status: 401 });
   }
 
-  const params = (await request.json()) as ChatParams;
-  const { path, userQuestion, sectionContent, replOutputs, files, execResults } =
-    params;
+  const parseResult = ChatParamsSchema.safeParse(await request.json());
+  if (!parseResult.success) {
+    return new Response(JSON.stringify(parseResult.error), { status: 400 });
+  }
+  const {
+    path,
+    userQuestion,
+    sectionContent,
+    replOutputs,
+    files,
+    execResults,
+  } = parseResult.data;
 
   const pagesList = await getPagesList();
   const langName = pagesList.find((lang) => lang.id === path.lang)?.name;
@@ -202,7 +220,7 @@ export async function POST(request: NextRequest) {
           prompt.join("\n")
         )) {
           console.log("Received chunk:", [chunk]);
-        
+
           fullText += chunk;
 
           if (!headerParsed) {
@@ -294,9 +312,7 @@ export async function POST(request: NextRequest) {
         await addMessagesAndDiffs(
           chatId,
           path,
-          [
-            { role: "ai", content: cleanMessage },
-          ],
+          [{ role: "ai", content: cleanMessage }],
           diffRaw,
           context
         );
diff --git a/app/lib/docs.ts b/app/lib/docs.ts
index 4104a9b0..cbe8a367 100644
--- a/app/lib/docs.ts
+++ b/app/lib/docs.ts
@@ -5,6 +5,7 @@ import yaml from "js-yaml";
 import { isCloudflare } from "./detectCloudflare";
 import { notFound } from "next/navigation";
 import crypto from "node:crypto";
+import { z } from "zod";
 
 /*
 Branded Types
@@ -18,33 +19,61 @@ type Brand<K, T> = K & { readonly __brand: T };
 export type LangId = Brand<string, "LangId">;
 export type LangName = Brand<string, "LangName">;
 export type PageSlug = Brand<string, "PageSlug">;
+export type SectionId = Brand<string, "SectionId">;
+
+export const PagePathSchema = z.object({
+  lang: z.string().transform((s) => s as LangId),
+  page: z.string().transform((s) => s as PageSlug),
+});
 export interface PagePath {
   lang: LangId;
   page: PageSlug;
 }
-export type SectionId = Brand<string, "SectionId">;
 
-export interface MarkdownSection {
+export const MarkdownSectionSchema = z.object({
   /**
    * セクションのmdファイル名
    */
-  file: string;
+  file: z.string(),
   /**
    * frontmatterに書くセクションid
    * (データベース上の sectionId)
    */
-  id: SectionId;
-  level: number;
-  title: string;
+  id: z.string().transform((s) => s as SectionId),
+  level: z.number(),
+  title: z.string(),
   /**
    * frontmatterを除く、見出しも含めたもとのmarkdownの内容
    */
-  rawContent: string;
+  rawContent: z.string(),
   /**
    * rawContentのmd5ハッシュのbase64エンコード
    */
-  md5: string;
-}
+  md5: z.string(),
+});
+export type MarkdownSection = z.output<typeof MarkdownSectionSchema>;
+
+export const ReplacedRangeSchema = z.object({
+  start: z.number(),
+  end: z.number(),
+  id: z.string(),
+});
+export type ReplacedRange = z.output<typeof ReplacedRangeSchema>;
+
+export const DynamicMarkdownSectionSchema = MarkdownSectionSchema.extend({
+  /**
+   * ユーザーが今そのセクションを読んでいるかどうか
+   */
+  inView: z.boolean(),
+  /**
+   * チャットの会話を元にAIが書き換えた後の内容
+   */
+  replacedContent: z.string(),
+  replacedRange: z.array(ReplacedRangeSchema),
+});
+export type DynamicMarkdownSection = z.output<
+  typeof DynamicMarkdownSectionSchema
+>;
 
 /**
  * 各言語のindex.ymlから読み込んだデータにid,index等を追加したデータ型
diff --git a/app/markdown/markdown.tsx b/app/markdown/markdown.tsx
index e55b51c5..2203c965 100644
--- a/app/markdown/markdown.tsx
+++ b/app/markdown/markdown.tsx
@@ -5,10 +5,10 @@ import remarkCjkFriendly from "remark-cjk-friendly";
 import {
   MultiHighlightTag,
   remarkMultiHighlight,
-  ReplacedRange,
 } from "./multiHighlight";
 import { Heading } from "./heading";
 import { AutoCodeBlock } from "./codeBlock";
+import { ReplacedRange } from "@/lib/docs";
 
 export function StyledMarkdown(props: {
   content: string;
diff --git a/app/markdown/multiHighlight.tsx b/app/markdown/multiHighlight.tsx
index aa5dd471..b118c0eb 100644
--- a/app/markdown/multiHighlight.tsx
+++ b/app/markdown/multiHighlight.tsx
@@ -6,12 +6,8 @@ import { ExtraProps } from "react-markdown";
 import clsx from "clsx";
 import { useChatId } from "@/(docs)/chatAreaState";
 import Link from "next/link";
+import type { ReplacedRange } from "@/lib/docs";
 
-export interface ReplacedRange {
-  start: number;
-  end: number;
-  id: string;
-}
 export const remarkMultiHighlight: Plugin<[ReplacedRange[]], Root> = (
   replacedRange?: ReplacedRange[]
 ) => {
diff --git a/app/sidebar.tsx b/app/sidebar.tsx
index 384074d1..eaf0034f 100644
--- a/app/sidebar.tsx
+++ b/app/sidebar.tsx
@@ -1,7 +1,7 @@
 "use client";
 import Link from "next/link";
 import { usePathname } from "next/navigation";
-import { LangId, LanguageEntry, PagePath, PageSlug } from "@/lib/docs";
+import { DynamicMarkdownSection, LangId, LanguageEntry, PagePath, PageSlug } from "@/lib/docs";
 import { AccountMenu } from "./accountMenu";
 import { ThemeToggle } from "./themeToggle";
 import {
@@ -15,7 +15,6 @@ import {
 import clsx from "clsx";
 import { LanguageIcon } from "@/terminal/icons";
 import { RuntimeLang } from "@my-code/runtime/languages";
-import { DynamicMarkdownSection } from "./(docs)/@docs/[lang]/[pageId]/pageContent";
 
 export interface ISidebarMdContext {
   loadedPath: PagePath | null;
diff --git a/package-lock.json b/package-lock.json
index e06b8298..ac4b7edb 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -22162,7 +22162,8 @@
         "react": "^19",
         "react-dom": "^19",
         "swr": "^2",
-        "typescript": "^5"
+        "typescript": "^5",
+        "zod": "^4.0.17"
       },
       "devDependencies": {
         "@testing-library/react": "^16.3.2",
diff --git a/packages/runtime/package.json b/packages/runtime/package.json
index 90edd5af..97bc1d5d 100644
--- a/packages/runtime/package.json
+++ b/packages/runtime/package.json
@@ -20,7 +20,8 @@
     "react": "^19",
     "react-dom": "^19",
     "swr": "^2",
-    "typescript": "^5"
+    "typescript": "^5",
+    "zod": "^4.0.17"
   },
   "devDependencies": {
     "@testing-library/react": "^16.3.2",
diff --git a/packages/runtime/src/interface.ts b/packages/runtime/src/interface.ts
index 07fb44e6..0d8b26ff 100644
--- a/packages/runtime/src/interface.ts
+++ b/packages/runtime/src/interface.ts
@@ -1,4 +1,5 @@
 import { MutexInterface } from "async-mutex";
+import { z } from "zod";
 
 /**
  * 各言語の実行環境のインタフェース
@@ -148,28 +149,33 @@ export interface RuntimeInfo {
   version?: string;
 }
 
-export type ReplOutputType =
-  | "stdout"
-  | "stderr"
-  | "error"
-  | "return"
-  | "trace"
-  | "system";
-export interface ReplOutput {
-  type: ReplOutputType; // 出力の種類
-  message: string; // 出力メッセージ
-}
-export interface UpdatedFile {
-  type: "file";
-  filename: string;
-  content: string;
-}
+export const ReplOutputTypeSchema = z.enum([
+  "stdout",
+  "stderr",
+  "error",
+  "return",
+  "trace",
+  "system",
+]);
+export type ReplOutputType = z.output<typeof ReplOutputTypeSchema>;
+export const ReplOutputSchema = z.object({
+  type: ReplOutputTypeSchema, // 出力の種類
+  message: z.string(), // 出力メッセージ
+});
+export type ReplOutput = z.output<typeof ReplOutputSchema>;
+export const UpdatedFileSchema = z.object({
+  type: z.literal("file"),
+  filename: z.string(),
+  content: z.string(),
+});
+export type UpdatedFile = z.output<typeof UpdatedFileSchema>;
 
-export interface ReplCommand {
-  command: string;
-  output: ReplOutput[];
-  commandId?: string; // Optional for backward compatibility
-}
+export const ReplCommandSchema = z.object({
+  command: z.string(),
+  output: z.array(ReplOutputSchema),
+  commandId: z.string().optional(), // Optional for backward compatibility
+});
+export type ReplCommand = z.output<typeof ReplCommandSchema>;
 export type SyntaxStatus = "complete" | "incomplete" | "invalid"; // 構文チェックの結果
 
 export const emptyMutex: MutexInterface = {