diff --git a/M02_MasterTemplete/M02_Item_Copy.py b/M02_MasterTemplete/M02_Item_Copy.py
index 5f211bd52..597b5cbf7 100644
--- a/M02_MasterTemplete/M02_Item_Copy.py
+++ b/M02_MasterTemplete/M02_Item_Copy.py
@@ -95,12 +95,15 @@ def source_changed(manifest: dict[str, Any]) -> bool | None:
     return version_of(source) != manifest.get("원본판")
 
 
-def list_items(project_root: str | Path) -> list[dict[str, Any]]:
+def list_items(project_root: str | Path, only: str | None = None) -> list[dict[str, Any]]:
+    """복사본 목록 — `only` = 그 폴더 하나만(고르기 모달 · 원본 대조를 그 하나만 · 156-2)."""
     base = _migrated(project_root)
     out = []
     for child in sorted(base.iterdir()) if base.is_dir() else []:
         if not child.is_dir() or not FOLDER_PATTERN.match(child.name):
             continue
+        if only is not None and child.name != only:
+            continue
         if not (child / MANIFEST_NAME).is_file():
             continue
         complete_old(child)
diff --git a/M02_MasterTemplete/M02_Item_Prices.py b/M02_MasterTemplete/M02_Item_Prices.py
index 3b98e61b7..8094536f2 100644
--- a/M02_MasterTemplete/M02_Item_Prices.py
+++ b/M02_MasterTemplete/M02_Item_Prices.py
@@ -50,6 +50,24 @@ def _texts(row: dict) -> list[str]:
     return out
 
 
+#: 재료 후보 찾기 답 — (마스터 색인, {조건 글: 키}) · 색인이 바뀌면(마스터 저장) 새로 ·
+#: 복사본 목록이 복사본마다 단가 묶음을 다시 모아도 같은 조건은 한 번만 찾음(156-2)
+_FOUND: tuple[Any, dict[str, list[str]]] = (None, {})
+
+
+def _candidates(whole: Any, cond: dict) -> list[str]:
+    """`mf.candidates(whole, cond)` 를 마스터 색인 하나에 한 번만 — 답은 마스터와 조건만 따름."""
+    global _FOUND
+    seen, found = _FOUND
+    if seen is not whole:
+        found = {}
+        _FOUND = (whole, found)
+    key = json.dumps(cond, ensure_ascii=False, sort_keys=True, default=str)
+    if key not in found:
+        found[key] = list(mf.candidates(whole, cond, None, None))
+    return found[key]
+
+
 class _Collector:
     def __init__(self, whole: Any):
         self.whole = whole
@@ -125,7 +143,7 @@ class _Collector:
                 self.add(str(one["대표"]))
             if not one.get("구분") and not one.get("검색어"):
                 continue
-            for key in mf.candidates(self.whole, one, None, None):
+            for key in _candidates(self.whole, one):
                 self.add(key)
 
     def flow(self, row: dict) -> None:
diff --git a/M02_MasterTemplete/M02_Item_Source.py b/M02_MasterTemplete/M02_Item_Source.py
index 2688b5aa0..30d53ed22 100644
--- a/M02_MasterTemplete/M02_Item_Source.py
+++ b/M02_MasterTemplete/M02_Item_Source.py
@@ -107,10 +107,16 @@ def logic_rows(row: dict[str, Any]) -> dict[str, Any]:
     wanted = [str(entry.get("로직")) for entry in row.get("담은로직") or [] if entry.get("로직")]
     found: dict[str, dict[str, Any]] = {}
     raw: dict[str, Any] = {}  # M01 적재본은 수가 Decimal — 줄은 원본 파일 JSON 그대로 담음
+    # 로직 키 → 파일 이름만(`m01.logic` 은 검사 · 단가 미리보기까지 돌아 느림 · 156-2)
+    files, _ = m01.loaded()
+    where = {
+        str(one.get("키")): name
+        for name, data in m01._logic_files(files)
+        for one in data.get("줄") or []
+    }
     for key in wanted:
-        try:
-            file = m01.logic(key)["file"]
-        except m01.StoreError:
+        file = where.get(key)
+        if file is None:
             continue
         if file not in raw:
             raw[file] = read_json(Path(m01.FOLDER) / file)
diff --git a/M02_MasterTemplete/M02_Project_Items_Router.py b/M02_MasterTemplete/M02_Project_Items_Router.py
index d2b37c796..6f9f780d7 100644
--- a/M02_MasterTemplete/M02_Project_Items_Router.py
+++ b/M02_MasterTemplete/M02_Project_Items_Router.py
@@ -1,7 +1,8 @@
 """프로젝트 구조물 집계 항목 복사본 길 — `/api/projects/{id}/items…` (PLAN 25-1b · 26-1 · 26-2b).
 
 폴더 = 구조물 id(`structure_id` · 관 지점은 `pipe@측점`) — 같은 항목을 고른 구조물도 복사본은 따로.
-    GET  …/items                           목록(원본 · 가져온날 · 마스터바뀜 · 원본없음)
+    GET  …/items[?folder=]                 목록(원본 · 가져온날 · 마스터바뀜 · 원본없음) ·
+        folder = 그 폴더 하나만(고르기 모달)
     POST …/items {structure, layer, owner, key}  미리 가져오기 → {폴더, 만듦, 가져온날}
     POST …/items/new {structure, 경로, 이름, 단위}  새 항목(개인 층에도) · 회사 없음 409
     GET  …/items/{폴더}/{종류}              {종류, 판, 내용}
@@ -104,9 +105,12 @@ async def _run(fn, *args):
 
 @router.get("/{project_id}/items")
 async def list_items(
-    project_id: str, session: dict[str, Any] = Depends(verify_session)
+    project_id: str,
+    folder: str | None = None,
+    session: dict[str, Any] = Depends(verify_session),
 ) -> dict[str, Any]:
-    return {"항목": await _run(copies.list_items, await _root(session, project_id))}
+    root = await _root(session, project_id)
+    return {"항목": await _run(copies.list_items, root, folder)}
 
 
 @router.post("/{project_id}/items")
diff --git a/resources/tester/test_156_2_picker_speed.py b/resources/tester/test_156_2_picker_speed.py
new file mode 100644
index 000000000..297323367
--- /dev/null
+++ b/resources/tester/test_156_2_picker_speed.py
@@ -0,0 +1,128 @@
+"""구조물 조합 고르기 모달 로딩 속도 (PLAN 156-2 · 임시 저장소 · 임시 마스터 사본).
+
+- 목록 `?folder=` = 그 복사본 하나만(원본 대조도 그 하나만) · 값은 통째 목록의 그 줄과 같음
+- 원본 대조(`build_source`)는 재료 후보 찾기를 같은 조건마다 한 번만 ·
+  `m01.logic`(검사 · 단가 미리보기) 안 부름
+- 값은 그대로 — 기억을 비우고 다시 모아도 단가 묶음 · 원본판이 같음
+- 모달 쪽 — 목록은 그 폴더만 · 복사본 부분 · 셈은 한 번 보이는 동안 한 번만
+"""
+
+from __future__ import annotations
+
+import time
+from pathlib import Path
+from typing import Any
+
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+from common_util.common_util_auth import verify_session
+from M01_MasterData import M01_MasterData_Store as m01
+from M02_MasterTemplete import M02_Item_Copy as copies
+from M02_MasterTemplete import M02_Item_Prices as prices
+from M02_MasterTemplete import M02_MasterTemplete_Router_Layers as layer_routes
+from M02_MasterTemplete import M02_Project_Items_Router as items_router
+from M02_MasterTemplete.M02_Item_Source import build_source, version_of
+from resources.tester.test_item_copy_complete import (  # noqa: F401 — 고정물
+    PIPE,
+    _save,
+    master_copy,
+    world,
+)
+
+UI = Path(__file__).resolve().parents[2] / "ui_template"
+WALL = {"layer": "system", "owner": None, "key": "SS000022", "name": "돌쌓기"}
+
+
+def _two(root: Path) -> None:
+    """관 지점 둘 — 같은 항목 하나 · 다른 항목 하나."""
+    _save(
+        root,
+        [
+            {"chainage_m": 40.0, "source": "user", "summary_item": PIPE},
+            {"chainage_m": 80.0, "source": "user", "summary_item": WALL},
+        ],
+    )
+
+
+def test_목록_folder_는_그_하나만_값은_통째와_같음(world, monkeypatch):  # noqa: F811
+    root = world["root"]
+    _two(root)
+    whole = {row["폴더"]: row for row in copies.list_items(root)}
+    assert set(whole) == {"pipe@40.0", "pipe@80.0"}
+    calls: list[Any] = []
+    real = copies.source_changed
+    monkeypatch.setattr(copies, "source_changed", lambda m: calls.append(m) or real(m))
+    assert copies.list_items(root, "pipe@80.0") == [whole["pipe@80.0"]]
+    assert len(calls) == 1  # 원본 대조 = 그 하나만
+    assert copies.list_items(root, "없음") == []
+
+
+def test_길_folder_거름(world, monkeypatch):  # noqa: F811
+    root = world["root"]
+    _two(root)
+
+    async def fake_row(project_id: str) -> dict[str, Any]:
+        return {"company_id": 3, "storage_path": str(root)}
+
+    monkeypatch.setattr(layer_routes, "_project_row", fake_row)
+    monkeypatch.setattr(layer_routes, "resolve_stored_project_path", lambda path: path)
+    app = FastAPI()
+    app.include_router(items_router.router)
+    app.dependency_overrides[verify_session] = lambda: {"role": "USER", "company_id": 3}
+    client = TestClient(app)
+    base = "/api/projects/p1/items"
+    assert len(client.get(base).json()["항목"]) == 2
+    got = client.get(base, params={"folder": "pipe@40.0"}).json()["항목"]
+    assert [row["폴더"] for row in got] == ["pipe@40.0"]
+
+
+def test_원본_대조는_같은_후보_찾기를_한_번만(world, monkeypatch):  # noqa: F811
+    found: list[str] = []
+    real = prices.mf.candidates
+    monkeypatch.setattr(
+        prices.mf, "candidates", lambda w, c, *a: found.append(repr(c)) or real(w, c, *a)
+    )
+    monkeypatch.setattr(prices, "_FOUND", (None, {}))
+
+    def no_logic(key: str) -> dict:
+        raise AssertionError("m01.logic 은 검사 · 단가 미리보기까지 돌아 느림 — 파일 이름만 찾음")
+
+    monkeypatch.setattr(m01, "logic", no_logic)
+    first = build_source(PIPE)
+    once = len(found)
+    assert once and len(set(found)) == once  # 같은 조건은 한 번만
+    again = build_source(PIPE)
+    assert len(found) == once  # 두 번째 대조 = 후보 찾기 안 함
+    assert version_of(again) == version_of(first)
+
+
+def test_기억을_비워도_단가_묶음_원본판_같음(world, monkeypatch):  # noqa: F811
+    root = world["root"]
+    _two(root)
+    before = {row["폴더"]: row["원본판"] for row in copies.list_items(root)}
+    monkeypatch.setattr(prices, "_FOUND", (None, {}))
+    for folder, item in (("pipe@40.0", PIPE), ("pipe@80.0", WALL)):
+        assert version_of(build_source(item)) == before[folder]
+    assert not any(row["마스터바뀜"] for row in copies.list_items(root))
+
+
+def test_목록_시간_상한(world):  # noqa: F811
+    """복사본 둘 · 두 번째 목록(기억 있음)은 0.5초 안 — 옛 길은 항목마다 2~5초."""
+    root = world["root"]
+    _two(root)
+    copies.list_items(root)
+    start = time.perf_counter()
+    copies.list_items(root)
+    assert time.perf_counter() - start < 0.5
+
+
+def test_모달은_그_폴더만_읽고_부분_셈은_한_번():
+    detail = (UI / "ui_template_item_picker_detail.ts").read_text(encoding="utf-8")
+    assert "infos ??= await items.list(folder);" in detail
+    assert "copyReads.set(part" in detail and "(copyCalc ??= " in detail
+    assert "items.read(" not in detail and "items?.calc(" not in detail  # 다 한 번 부름 길로
+    show = detail[detail.index("function show(") :]
+    assert "copyReads = new Map();" in show and "copyCalc = null;" in show  # 보일 때마다 새로
+    project = (UI / "ui_template_item_picker_project.ts").read_text(encoding="utf-8")
+    assert "folder ? `${base}?folder=${enc(folder)}` : base" in project
diff --git a/resources/tester/test_item_picker_detail.py b/resources/tester/test_item_picker_detail.py
index a6e00779f..91320af14 100644
--- a/resources/tester/test_item_picker_detail.py
+++ b/resources/tester/test_item_picker_detail.py
@@ -176,7 +176,8 @@ def test_모달_일위대가_카드_읽기_전용():
     """142-1 — 모달 자료 자리엔 쓰는 길(`write`)이 없고 카드는 그때 보기만(원본 층 [저장]을 안 엶)."""
     detail = (UI / "ui_template_item_picker_detail.ts").read_text(encoding="utf-8")
     body = detail[detail.index("const makeSource") : detail.index("const badge")]
-    assert "write" not in body and "labor: {" in body and "items.calcLabor(at)" in body
+    assert "write" not in body and "labor: {" in body and "calc: () => calcCopy(at)," in body
+    assert "(copyCalc ??= (items as ProjectItems).calcLabor(at))" in detail  # 한 번 셈(156-2)
     cards = (M02 / "M02_MasterTemplete_ItemCards.ts").read_text(encoding="utf-8")
     assert "const laborWritable = (): boolean => opts.editable() && !!opts.source().write;" in cards
     assert "readOnly: !laborWritable()," in cards
diff --git a/ui_template/ui_template_item_picker_detail.ts b/ui_template/ui_template_item_picker_detail.ts
index 7e4389ef6..bdea143d2 100644
--- a/ui_template/ui_template_item_picker_detail.ts
+++ b/ui_template/ui_template_item_picker_detail.ts
@@ -33,9 +33,12 @@ import {
   projectItems,
   sameItem,
   structureFolder,
+  summarize,
+  type CopyCalc,
   type CreatedItem,
   type ProjectItemInfo,
   type ProjectItems,
+  type ProjectPart,
   withCopyValues,
 } from "./ui_template_item_picker_project";
 
@@ -131,6 +134,17 @@ export function createItemDetail(opts: ItemDetailOptions): ItemDetail {
   /** 이 구조물에 있는 복사본 — 고른 항목의 것일 때만(다른 항목의 것이면 `other`) */
   let info: ProjectItemInfo | null = null;
   let other: ProjectItemInfo | null = null;
+  /** 한 번 보이는 동안 복사본 부분 · 셈은 한 번만 부름(카드 · 일위대가 · 상태 줄이 같은 것을 씀 · 156-2) —
+   * 새로 보일 때(`show`) 비움 */
+  let copyReads = new Map<ProjectPart, Promise<unknown | null>>();
+  let copyCalc: Promise<CopyCalc> | null = null;
+  const readCopy = (at: string, part: ProjectPart): Promise<unknown | null> => {
+    let got = copyReads.get(part);
+    if (!got) copyReads.set(part, (got = (items as ProjectItems).read(at, part)));
+    return got;
+  };
+  const calcCopy = (at: string): Promise<CopyCalc> =>
+    (copyCalc ??= (items as ProjectItems).calcLabor(at));
   const items: ProjectItems | null = opts.projectId ? projectItems(opts.projectId) : null;
   const folder = opts.structureId ? structureFolder(opts.structureId) : null;
   /** 복사본을 고칠 수 있나 — 프로젝트 안 · 구조물이 있을 때 */
@@ -163,20 +177,20 @@ export function createItemDetail(opts: ItemDetailOptions): ItemDetail {
         layer: "project",
         projectId: opts.projectId,
         read: async (part) => {
-          const doc = await items.read(at, PART_OF[part]);
+          const doc = await readCopy(at, PART_OF[part]);
           if (doc == null) throw new Error(TEXT.noCopy);
           return { 문서: doc };
         },
         labor: {
           read: async () => {
             const [labor, values, picks] = await Promise.all([
-              items.read(at, "일위대가") as Promise<{ 줄?: LaborDoc } | null>,
-              items.read(at, "입력값") as Promise<ValueDoc | null>,
-              items.read(at, "고른자재") as Promise<Record<string, unknown> | null>,
+              readCopy(at, "일위대가") as Promise<{ 줄?: LaborDoc } | null>,
+              readCopy(at, "입력값") as Promise<ValueDoc | null>,
+              readCopy(at, "고른자재") as Promise<Record<string, unknown> | null>,
             ]);
             return { 문서: labor?.줄 ? withCopyValues(labor.줄, values, picks) : {} };
           },
-          calc: () => items.calcLabor(at),
+          calc: () => calcCopy(at),
         },
       };
     }
@@ -222,7 +236,7 @@ export function createItemDetail(opts: ItemDetailOptions): ItemDetail {
 
   /** 복사본만으로 계산한 계 · 빠진 입력을 한 줄로(값을 넣고 돌아오면 달라짐) */
   async function paintCalc(from: ProjectItemInfo, mine: number): Promise<void> {
-    const got = await items?.calc(from.폴더).catch(() => null);
+    const got = await calcCopy(from.폴더).then(summarize, () => null);
     if (!got || mine !== seq) return;
     const total = Math.round(got.total).toLocaleString();
     status.append(
@@ -319,6 +333,8 @@ export function createItemDetail(opts: ItemDetailOptions): ItemDetail {
   function show(row: PickerRow | null): void {
     const mine = ++seq;
     current = row;
+    copyReads = new Map();
+    copyCalc = null;
     if (!row) {
       head.replaceChildren(el("p", { className: "ui-item-picker__hint", text: opts.hint }));
       status.hidden = true;
@@ -329,7 +345,7 @@ export function createItemDetail(opts: ItemDetailOptions): ItemDetail {
     paintHead(row);
     void (async () => {
       try {
-        if (items && folder) infos ??= await items.list();
+        if (items && folder) infos ??= await items.list(folder);
       } catch (error) {
         if (mine === seq) showToast(fill(TEXT.listFailed, why(error)), "error");
         infos = [];
diff --git a/ui_template/ui_template_item_picker_project.ts b/ui_template/ui_template_item_picker_project.ts
index bcf7b5cf0..0b800712d 100644
--- a/ui_template/ui_template_item_picker_project.ts
+++ b/ui_template/ui_template_item_picker_project.ts
@@ -3,7 +3,7 @@
  * 항목 고르기 모달의 **자료 창구**(계획서 25-2d) — 프로젝트 복사본 · 입력 목록 · 계산을 한 곳에서 부름.
  *
  *   구조물 복사본(sub6 · 26-1 · 26-2b) — 폴더 = 구조물 id(같은 항목을 고른 구조물도 복사본은 따로)
- *     GET  /api/projects/{id}/items                     → {항목: [{폴더, 이름, 원본, 원본판, 가져온날, 마스터바뀜, 원본없음, …}]}
+ *     GET  /api/projects/{id}/items[?folder=]           → {항목: [{폴더, 이름, 원본, 원본판, 가져온날, 마스터바뀜, 원본없음, …}]} · folder = 그 하나만
  *     POST /api/projects/{id}/items {structure, layer, owner, key} 미리 가져오기 → {폴더, 만듦, 가져온날}
  *     POST /api/projects/{id}/items/new {structure, 경로, 이름, 단위} 새 항목(개인 층에도) → {…, summary_item}
  *     GET|PUT /api/projects/{id}/items/{폴더}/{부분}    → {종류, 판, 내용} · 고침은 {판, 내용}(판이 다르면 409)
@@ -112,8 +112,8 @@ async function call(path: string, init: RequestInit = {}): Promise<Reply> {
 const post = (body: unknown): RequestInit => ({ method: "POST", body: JSON.stringify(body) });
 
 export interface ProjectItems {
-  /** 프로젝트에 가져온 항목 목록 — 서버가 항목당 0.5초쯤 걸려 모달이 열 때 한 번만 부르고 들고 있음 */
-  list: () => Promise<ProjectItemInfo[]>;
+  /** 프로젝트에 가져온 항목 목록 — 서버가 항목마다 원본을 다시 모아 대조 · `folder` = 그 폴더 하나만(고르기 모달 · 156-2) */
+  list: (folder?: string) => Promise<ProjectItemInfo[]>;
   /** 복사본 부분 하나(`내용`) — 없으면 null · 판은 고칠 때를 위해 들고 있음 */
   read: (folder: string, part: ProjectPart) => Promise<unknown | null>;
   /** 복사본 고침 — 못 하면 서버 까닭 그대로 던짐(권한 · 판이 다름 …) */
@@ -142,6 +142,15 @@ export interface ProjectItems {
 
 const clients = new Map<string, ProjectItems>();
 
+/** 복사본 셈 답 → 모달이 보이는 것(계 · 빈 입력 수 · 못 돈 줄 수) */
+export const summarize = (got: CopyCalc): ProjectCalc => ({
+  total: Number(got.반영합?.계 ?? got.기준합?.계 ?? 0),
+  gaps: got.빠진입력?.length ?? 0,
+  stuck: (got.줄 ?? []).filter((line) => line.까닭).length,
+  base: got.기준합?.계 ?? null,
+  reflected: got.반영합?.계 ?? null,
+});
+
 /** 프로젝트 하나의 창구 — 같은 프로젝트는 한 벌(고칠 때 쓸 판을 들고 있음) */
 export function projectItems(projectId: string): ProjectItems {
   const kept = clients.get(projectId);
@@ -161,8 +170,8 @@ export function projectItems(projectId: string): ProjectItems {
   };
 
   const client: ProjectItems = {
-    list: async () => {
-      const reply = await call(base);
+    list: async (folder) => {
+      const reply = await call(folder ? `${base}?folder=${enc(folder)}` : base);
       const rows = (reply.body as { 항목?: ProjectItemInfo[] } | null)?.항목;
       if (reply.status !== 200 || !Array.isArray(rows)) throw new Error(reasonOf(reply));
       return rows;
@@ -231,14 +240,7 @@ export function projectItems(projectId: string): ProjectItems {
     },
     calc: async (folder) => {
       const got = await calcCopy(folder).catch(() => null);
-      if (!got) return null;
-      return {
-        total: Number(got.반영합?.계 ?? got.기준합?.계 ?? 0),
-        gaps: got.빠진입력?.length ?? 0,
-        stuck: (got.줄 ?? []).filter((line) => line.까닭).length,
-        base: got.기준합?.계 ?? null,
-        reflected: got.반영합?.계 ?? null,
-      };
+      return got ? summarize(got) : null;
     },
     calcLabor: (folder) => calcCopy(folder),
     link: async (copy, facility, item) => {