diff --git a/src/app/boards/[id]/page.tsx b/src/app/boards/[id]/page.tsx
index e098736..2dd8501 100644
--- a/src/app/boards/[id]/page.tsx
+++ b/src/app/boards/[id]/page.tsx
@@ -1,6 +1,7 @@
 import { PostList } from "@/app/components/PostList";
 import { headers } from "next/headers";
 
+// Next 15: params/searchParams가 Promise가 될 수 있어 안전 언랩 처리합니다.
 export default async function BoardDetail({ params, searchParams }: { params: any; searchParams: any }) {
   const p = params?.then ? await params : params;
   const sp = searchParams?.then ? await searchParams : searchParams;
diff --git a/src/app/boards/page.tsx b/src/app/boards/page.tsx
index 41edc89..b29b30a 100644
--- a/src/app/boards/page.tsx
+++ b/src/app/boards/page.tsx
@@ -1,6 +1,7 @@
 import { headers } from "next/headers";
 
 export default async function BoardsPage() {
+  // 서버에서 상대경로 fetch가 실패하므로 요청 헤더로 절대 URL을 구성합니다.
   const h = await headers();
   const host = h.get("host") ?? "localhost:3000";
   const proto = h.get("x-forwarded-proto") ?? "http";
diff --git a/src/app/components/AppHeader.tsx b/src/app/components/AppHeader.tsx
index 1dc42c8..99c686f 100644
--- a/src/app/components/AppHeader.tsx
+++ b/src/app/components/AppHeader.tsx
@@ -1,4 +1,5 @@
 "use client";
+// 클라이언트 훅(useState/useEffect)을 사용하여 세션 표시/로그아웃을 처리합니다.
 import { ThemeToggle } from "@/app/components/ThemeToggle";
 import { SearchBar } from "@/app/components/SearchBar";
 import { Button } from "@/app/components/ui/Button";
@@ -6,6 +7,7 @@ import React from "react";
 
 export function AppHeader() {
   const [user, setUser] = React.useState<{ nickname: string } | null>(null);
+  // 헤더 마운트 시 세션 존재 여부를 조회해 로그인/로그아웃 UI를 제어합니다.
   React.useEffect(() => {
     fetch("/api/auth/session")
       .then((r) => r.json())
diff --git a/src/app/posts/[id]/page.tsx b/src/app/posts/[id]/page.tsx
index a850382..7bf78cf 100644
--- a/src/app/posts/[id]/page.tsx
+++ b/src/app/posts/[id]/page.tsx
@@ -1,9 +1,10 @@
 import { notFound } from "next/navigation";
 import { headers } from "next/headers";
-import React, { use } from "react";
 
-export default async function PostDetail({ params }: { params: Promise<{ id: string }> }) {
-  const { id } = use(params);
+// 서버 전용 페이지: params가 Promise일 수 있어 안전 언랩 후 절대 URL로 fetch합니다.
+export default async function PostDetail({ params }: { params: any }) {
+  const p = params?.then ? await params : params;
+  const id = p.id as string;
   const h = await headers();
   const host = h.get("host") ?? "localhost:3000";
   const proto = h.get("x-forwarded-proto") ?? "http";
diff --git a/src/app/posts/new/page.tsx b/src/app/posts/new/page.tsx
index 89bd7ea..e6faf0d 100644
--- a/src/app/posts/new/page.tsx
+++ b/src/app/posts/new/page.tsx
@@ -1,17 +1,33 @@
 "use client";
+// 클라이언트 라우터/검색파라미터 훅으로 새 글 작성 폼을 제어합니다.
 import { useState } from "react";
-import { useRouter } from "next/navigation";
+import { useRouter, useSearchParams } from "next/navigation";
 import { useToast } from "@/app/components/ui/ToastProvider";
 import { UploadButton } from "@/app/components/UploadButton";
 import { Editor } from "@/app/components/Editor";
 
-export default function NewPostPage({ searchParams }: { searchParams?: { boardId?: string; boardSlug?: string } }) {
+export default function NewPostPage() {
   const router = useRouter();
   const { show } = useToast();
-  const [form, setForm] = useState({ boardId: searchParams?.boardId ?? "", title: "", content: "" });
+  const sp = useSearchParams();
+  const initialBoardId = sp.get("boardId") ?? "";
+  const boardSlug = sp.get("boardSlug") ?? undefined;
+  const [form, setForm] = useState({ boardId: initialBoardId, title: "", content: "" });
   const [loading, setLoading] = useState(false);
   async function submit() {
     try {
+      if (!form.boardId.trim()) {
+        show("boardId가 비어 있습니다");
+        return;
+      }
+      if (!form.title.trim()) {
+        show("제목을 입력하세요");
+        return;
+      }
+      if (!form.content.trim()) {
+        show("내용을 입력하세요");
+        return;
+      }
       setLoading(true);
       const r = await fetch("/api/posts", {
         method: "POST",
@@ -19,11 +35,15 @@ export default function NewPostPage({ searchParams }: { searchParams?: { boardId
         body: JSON.stringify({ ...form }),
       });
       const data = await r.json();
-      if (!r.ok) throw new Error(JSON.stringify(data));
+      if (!r.ok) {
+        const fe = (data?.error?.fieldErrors ?? {}) as Record<string, string[]>;
+        const msg = data?.error?.message || Object.values(fe)[0]?.[0] || "작성 실패";
+        throw new Error(msg);
+      }
       show("작성되었습니다");
       router.push(`/posts/${data.post.id}`);
     } catch (e) {
-      show("작성 실패");
+      show(e instanceof Error ? e.message : "작성 실패");
     } finally {
       setLoading(false);
     }
@@ -37,7 +57,7 @@ export default function NewPostPage({ searchParams }: { searchParams?: { boardId
       <UploadButton
         multiple
         onUploaded={(url) => setForm((f) => ({ ...f, content: `${f.content}\n![image](${url})` }))}
-        {...(searchParams?.boardSlug ? require("@/lib/photoPresets").getPhotoPresetBySlug(searchParams.boardSlug) : {})}
+        {...(boardSlug ? require("@/lib/photoPresets").getPhotoPresetBySlug(boardSlug) : {})}
       />
       <button disabled={loading} onClick={submit}>{loading ? "저장 중..." : "등록"}</button>
     </div>