diff --git a/B04_PreProcess/B04_PreProcess_Engine.py b/B04_PreProcess/B04_PreProcess_Engine.py
index 613cd2743..53f567821 100644
--- a/B04_PreProcess/B04_PreProcess_Engine.py
+++ b/B04_PreProcess/B04_PreProcess_Engine.py
@@ -22,6 +22,8 @@ from B04_PreProcess.B04_PreProcess_Engine_Ground import (
 from B04_PreProcess.B04_PreProcess_Engine_Pipeline import build_all_terrain_models
 from B04_PreProcess.B04_PreProcess_Engine_Structurize import structurize_las
 from common_util.common_util_atomic import atomic_write_npz
+from common_util.common_util_derived_store import file_stamp
+from common_util.common_util_derived_store import key_matches as _key_matches
 from common_util.common_util_json import atomic_write_json
 from config.config_system import (
     SHEET_SURFACE_AUTO_METHODS,
@@ -128,23 +130,6 @@ def _structured_stats(structured: Any, structured_path: Path) -> tuple[dict[str,
     return stats, xyz
 
 
-def file_stamp(path: Path | None) -> str | None:
-    """결과 파일 지문 = 수정시각 ns : 크기. 없으면 None."""
-    try:
-        stat = path.stat() if path is not None else None
-    except OSError:
-        return None
-    return f"{stat.st_mtime_ns}:{stat.st_size}" if stat else None
-
-
-def _key_matches(key_path: Path, key: Any) -> bool:
-    """결과 옆 열쇠 파일이 지금 입력과 같은지."""
-    try:
-        return json.loads(key_path.read_text(encoding="utf-8")) == key
-    except (OSError, ValueError):
-        return False
-
-
 def _relative_to_project(project_root: Path, path: Path) -> str:
     """프로젝트 루트 기준 posix 상대 경로 문자열."""
     return path.relative_to(project_root).as_posix()
diff --git a/B04_PreProcess/B04_PreProcess_Engine_SheetSurface.py b/B04_PreProcess/B04_PreProcess_Engine_SheetSurface.py
index 22ae99d4f..9b6335888 100644
--- a/B04_PreProcess/B04_PreProcess_Engine_SheetSurface.py
+++ b/B04_PreProcess/B04_PreProcess_Engine_SheetSurface.py
@@ -25,7 +25,6 @@ from typing import Any
 import numpy as np
 from pyproj import Transformer
 
-from B04_PreProcess.B04_PreProcess_Engine import file_stamp
 from B04_PreProcess.B04_PreProcess_Engine_ModelContext import (
     atomic_npz,
     clip_and_compact_mesh,
@@ -38,6 +37,7 @@ from B04_PreProcess.B04_PreProcess_Engine_SheetMethods import (
     SHEET_METHOD_LABELS,
 )
 from B04_PreProcess.B04_PreProcess_Engine_Watershed_Grid import grid_spec_from_bounds
+from common_util.common_util_derived_store import file_stamp
 from common_util.common_util_json import atomic_write_json
 from config.config_system import (
     SHEET_SURFACE_GRID_M,
diff --git a/B06_Section/B06_Section_Router_HaulPlan.py b/B06_Section/B06_Section_Router_HaulPlan.py
index b3643bad6..947de6450 100644
--- a/B06_Section/B06_Section_Router_HaulPlan.py
+++ b/B06_Section/B06_Section_Router_HaulPlan.py
@@ -19,12 +19,14 @@ import hashlib
 import json
 import logging
 from collections import OrderedDict
+from pathlib import Path
 from typing import Any
 from uuid import UUID
 
 from fastapi import APIRouter, Body
 from fastapi.responses import JSONResponse
 
+from B03_FileInput.B03_FileInput_Repository import get_project_storage_relative_path
 from B06_Section.B06_Section_Server_Calc_Prebuild import (
     BUNDLE,
     _mass_haul_context,
@@ -32,7 +34,10 @@ from B06_Section.B06_Section_Server_Calc_Prebuild import (
     haul_inputs_for,
     haul_limits_for,
 )
+from common_util.common_util_derived_store import read_derived, write_derived
 from common_util.common_util_node_bundle import run_bundle_json
+from common_util.common_util_storage import resolve_stored_project_path
+from config.config_db import run_with_connection
 
 logger = logging.getLogger(__name__)
 router = APIRouter(prefix="/api/projects", tags=["B06 Profile Cross"])
@@ -41,10 +46,11 @@ _NPM_SCRIPT = "build:server-calc"
 # 측점 수 상한 — 정상 노선은 수백 곳이다. 그보다 크면 비정상 요청으로 본다.
 _MAX_POINTS = 5000
 # 열쇠(누가토량 결과 + 계수 · 장비 경계) → 배분 — 같은 열쇠면 Node 를 다시 안 띄움
-# (342-1 · 부록 4 R25). ponytail: 프로세스 메모리 · 최근 몇 벌만 — 재시작 뒤 첫 열기는
-# 다시 셈(_derived 저장본은 343 틀 뒤).
+# (342-1 · 부록 4 R25). 프로세스 메모리 먼저 · 다음 = 프로젝트 `_derived/haul/<열쇠>.json`
+# (재시작 뒤 첫 열기도 셈 없음 · 종류당 최근 2벌).
 _KEPT: OrderedDict[str, Any] = OrderedDict()
 _KEPT_MAX = 32
+_DERIVED_KIND = "haul"
 
 
 def _plan_key(result: dict[str, Any], context: Any) -> str:
@@ -52,6 +58,12 @@ def _plan_key(result: dict[str, Any], context: Any) -> str:
     return hashlib.sha1(body.encode("utf-8")).hexdigest()
 
 
+def _keep(key: str, plan: Any) -> None:
+    _KEPT[key] = plan
+    if len(_KEPT) > _KEPT_MAX:
+        _KEPT.popitem(last=False)
+
+
 @router.post("/{project_id}/sections/{route_id}/haul-plan", response_model=None)
 async def compute_haul_plan(
     project_id: UUID,
@@ -87,6 +99,20 @@ async def compute_haul_plan(
     if key in _KEPT:
         _KEPT.move_to_end(key)
         return JSONResponse(content={"status": "success", "haul_plan": _KEPT[key]})
+    project_root: Path | None = None
+    try:
+        stored_path = await run_with_connection(get_project_storage_relative_path, project_id)
+        project_root = Path(resolve_stored_project_path(stored_path))
+    except Exception:  # noqa: BLE001 — 저장소를 못 찾아도 셈은 함(디스크 저장본만 건너뜀)
+        logger.warning("유토 배분 저장소 못 찾음: project_id=%s", project_id)
+    stored = (
+        None
+        if project_root is None
+        else await asyncio.to_thread(read_derived, project_root, _DERIVED_KIND, key)
+    )
+    if stored is not None:
+        _keep(key, stored["value"])
+        return JSONResponse(content={"status": "success", "haul_plan": stored["value"]})
     try:
         output = await asyncio.to_thread(
             run_bundle_json,
@@ -107,7 +133,10 @@ async def compute_haul_plan(
             content={"status": "error", "message": "유토 배분 계산에 실패했습니다."},
         )
     plan = output.get("haul_plan")
-    _KEPT[key] = plan
-    if len(_KEPT) > _KEPT_MAX:
-        _KEPT.popitem(last=False)
+    _keep(key, plan)
+    try:
+        if project_root is not None:
+            await asyncio.to_thread(write_derived, project_root, _DERIVED_KIND, key, plan)
+    except OSError:  # 못 적어도 응답은 그대로 — 다음에 다시 셈
+        logger.warning("유토 배분 저장본 쓰기 실패: project_id=%s", project_id, exc_info=True)
     return JSONResponse(content={"status": "success", "haul_plan": plan})
diff --git a/common_util/common_util_derived_store.py b/common_util/common_util_derived_store.py
new file mode 100644
index 000000000..9cc242a97
--- /dev/null
+++ b/common_util/common_util_derived_store.py
@@ -0,0 +1,78 @@
+"""파생 저장본 — 입력 지문 열쇠 + 결과 한 쌍(343 · 341 부록 4 2-1).
+
+자리 = 프로젝트 `_derived/<종류>/<열쇠>.json` · 작업본에서 다시 셀 수 있는 값만(정본 아님) ·
+통째로 지워도 다시 셈으로 돌아옴 · 종류마다 최근 `KEEP` 벌(꺼내면 최근으로).
+결과 옆 열쇠(`<이름>.key.json` — 결과가 곧 산출물인 도엽 3D 면 등)는 `key_matches` · `file_stamp`.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import json
+from pathlib import Path
+from typing import Any
+
+from common_util.common_util_json import atomic_write_json
+
+DERIVED_DIR = "_derived"
+KEEP = 2
+
+
+def derived_key(*parts: Any) -> str:
+    """입력 지문 — 작은 입력은 내용 그대로 · 파일은 `file_stamp` 를 넣는다."""
+    body = json.dumps(parts, sort_keys=True, ensure_ascii=False, default=str)
+    return hashlib.sha1(body.encode("utf-8")).hexdigest()
+
+
+def file_stamp(path: Path | None) -> str | None:
+    """파일 지문 = 수정시각 ns : 크기. 없으면 None."""
+    try:
+        stat = path.stat() if path is not None else None
+    except OSError:
+        return None
+    return f"{stat.st_mtime_ns}:{stat.st_size}" if stat else None
+
+
+def key_matches(key_path: Path, key: Any) -> bool:
+    """결과 옆 열쇠 파일이 지금 입력과 같은지."""
+    try:
+        return json.loads(key_path.read_text(encoding="utf-8")) == key
+    except (OSError, ValueError):
+        return False
+
+
+def derived_dir(project_root: Path, kind: str) -> Path:
+    return Path(project_root) / DERIVED_DIR / kind
+
+
+def read_derived(project_root: Path, kind: str, key: str) -> dict[str, Any] | None:
+    """저장본 `{"value": …}` — 없거나 못 읽으면 None(값이 null 이어도 맞음과 구별)."""
+    path = derived_dir(project_root, kind) / f"{key}.json"
+    try:
+        data = json.loads(path.read_text(encoding="utf-8"))
+    except (OSError, ValueError):
+        return None
+    if not isinstance(data, dict) or data.get("key") != key or "value" not in data:
+        return None
+    try:
+        path.touch()  # 최근에 쓴 것 = 정리 때 남김
+    except OSError:
+        pass
+    return data
+
+
+def write_derived(project_root: Path, kind: str, key: str, value: Any, keep: int = KEEP) -> None:
+    """원자 쓰기 뒤 같은 종류 옛 열쇠를 정리한다."""
+    atomic_write_json(derived_dir(project_root, kind) / f"{key}.json", {"key": key, "value": value})
+    prune_derived(project_root, kind, keep)
+
+
+def prune_derived(project_root: Path, kind: str, keep: int = KEEP) -> int:
+    """종류 하나를 최근 `keep` 벌만 남기고 지운다. 지운 수."""
+    folder = derived_dir(project_root, kind)
+    files = sorted(
+        ((path.stat().st_mtime_ns, path) for path in folder.glob("*.json")), reverse=True
+    )
+    for _, path in files[keep:]:
+        path.unlink(missing_ok=True)
+    return max(0, len(files) - keep)
diff --git a/resources/tester/test_343_4_derived.py b/resources/tester/test_343_4_derived.py
new file mode 100644
index 000000000..a5a799835
--- /dev/null
+++ b/resources/tester/test_343_4_derived.py
@@ -0,0 +1,170 @@
+"""343 덧 — 파생 저장본 도우미 · 유토 배분 저장본 · B07 읽기 안 지움 · 묶음 낡음 검사 기억."""
+
+from __future__ import annotations
+
+import asyncio
+import json
+import os
+import time
+from pathlib import Path
+from uuid import uuid4
+
+import pytest
+
+from B06_Section import B06_Section_Router_HaulPlan as haul
+from common_util import common_util_derived_store as store
+from common_util import common_util_node_bundle as nb
+
+# ── 도우미 ──────────────────────────────────────────────────────────────────────
+
+
+def test_열쇠_같은_입력_같은_값() -> None:
+    assert store.derived_key({"a": 1, "b": 2}, 3) == store.derived_key({"b": 2, "a": 1}, 3)
+    assert store.derived_key({"a": 1}) != store.derived_key({"a": 2})
+
+
+def test_읽기_쓰기_null_도_맞음(tmp_path: Path) -> None:
+    assert store.read_derived(tmp_path, "haul", "k") is None
+    store.write_derived(tmp_path, "haul", "k", None)
+    assert store.read_derived(tmp_path, "haul", "k") == {"key": "k", "value": None}
+    assert (tmp_path / "_derived" / "haul" / "k.json").is_file()
+
+
+def test_종류마다_최근_두_벌_꺼내면_최근(tmp_path: Path) -> None:
+    store.write_derived(tmp_path, "haul", "a", 1)
+    time.sleep(0.02)
+    store.write_derived(tmp_path, "haul", "b", 2)
+    store.write_derived(tmp_path, "other", "x", 0)
+    time.sleep(0.02)
+    assert store.read_derived(tmp_path, "haul", "a")["value"] == 1
+    time.sleep(0.02)
+    store.write_derived(tmp_path, "haul", "c", 3)
+    names = sorted(path.stem for path in (tmp_path / "_derived" / "haul").glob("*.json"))
+    assert names == ["a", "c"]
+    assert (tmp_path / "_derived" / "other" / "x.json").is_file()
+
+
+def test_결과_옆_열쇠와_파일_지문(tmp_path: Path) -> None:
+    path = tmp_path / "m.key.json"
+    assert not store.key_matches(path, {"a": 1})
+    path.write_text(json.dumps({"a": 1}), encoding="utf-8")
+    assert store.key_matches(path, {"a": 1}) and not store.key_matches(path, {"a": 2})
+    assert store.file_stamp(tmp_path / "없음") is None and store.file_stamp(path)
+
+
+# ── 유토 배분 디스크 저장본 ─────────────────────────────────────────────────────────
+
+
+def _wire(monkeypatch: pytest.MonkeyPatch, root: Path, outputs: list) -> list:
+    calls: list = []
+
+    async def _none(_project_id):  # type: ignore[no-untyped-def]
+        return {}
+
+    async def _stored(_fn, _project_id):  # type: ignore[no-untyped-def]
+        return "p"
+
+    def _run(_bundle, _script, payload):  # type: ignore[no-untyped-def]
+        calls.append(payload)
+        return outputs.pop(0)
+
+    monkeypatch.setattr(haul, "haul_inputs_for", _none)
+    monkeypatch.setattr(haul, "conversion_factors_for", _none)
+    monkeypatch.setattr(haul, "haul_limits_for", _none)
+    monkeypatch.setattr(haul, "_mass_haul_context", lambda *_: {"limits": []})
+    monkeypatch.setattr(haul, "run_bundle_json", _run)
+    monkeypatch.setattr(haul, "run_with_connection", _stored)
+    monkeypatch.setattr(haul, "resolve_stored_project_path", lambda _p: str(root))
+    haul._KEPT.clear()
+    return calls
+
+
+def _post(result: dict) -> dict:
+    response = asyncio.run(haul.compute_haul_plan(uuid4(), 7, {"result": result}))
+    return json.loads(response.body)
+
+
+def test_유토_배분_재시작_뒤에도_셈_없음(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+    calls = _wire(monkeypatch, tmp_path, [{"haul_plan": {"tag": "a"}}, {"haul_plan": {"tag": "b"}}])
+    a = {"points": [{"cumulative_volume_m3": 1.0}]}
+    assert _post(a)["haul_plan"] == {"tag": "a"} and len(calls) == 1
+    key = haul._plan_key(a, {"limits": []})  # 화면 · 서버 메모리와 같은 열쇠
+    assert (tmp_path / "_derived" / "haul" / f"{key}.json").is_file()
+    haul._KEPT.clear()  # 재시작
+    assert _post(a)["haul_plan"] == {"tag": "a"} and len(calls) == 1
+    b = {"points": [{"cumulative_volume_m3": 2.0}]}
+    assert _post(b)["haul_plan"] == {"tag": "b"} and len(calls) == 2
+
+
+def test_유토_배분_저장소_못_찾아도_셈(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+    calls = _wire(monkeypatch, tmp_path, [{"haul_plan": {"tag": "a"}}])
+
+    async def _missing(_fn, _project_id):  # type: ignore[no-untyped-def]
+        raise LookupError("없음")
+
+    monkeypatch.setattr(haul, "run_with_connection", _missing)
+    assert _post({"points": [{"cumulative_volume_m3": 1.0}]})["haul_plan"] == {"tag": "a"}
+    assert len(calls) == 1 and not (tmp_path / "_derived").exists()
+
+
+# ── B07 읽기는 측점 파일을 안 지움 ─────────────────────────────────────────────────
+
+
+def test_B07_읽기는_잔재를_걸러만_읽음(tmp_path: Path) -> None:
+    from B07_DesignDetail.B07_DesignDetail_Router_Support_Io import _cross_files
+
+    cross_dir = tmp_path / "B05_Profile" / "cross_sections"
+    cross_dir.mkdir(parents=True)
+    for name in ("cross_00000m.json", "cross_00020m.json", "cross_00040m.json"):
+        (cross_dir / name).write_text("{}", encoding="utf-8")
+    longitudinal_path = tmp_path / "B05_Profile" / "longitudinal" / "longitudinal.json"
+    files = _cross_files(longitudinal_path, {"stations": [{"chainage_m": 0}, {"chainage_m": 20}]})
+    assert [path.name for path in files] == ["cross_00000m.json", "cross_00020m.json"]
+    assert (cross_dir / "cross_00040m.json").is_file()
+
+
+# ── 묶음 낡음 검사 기억 ─────────────────────────────────────────────────────────
+
+
+@pytest.fixture
+def bundle(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> Path:
+    monkeypatch.setattr(nb, "ROOT", tmp_path)
+    monkeypatch.setattr(nb, "_FRESH", {})
+    path = tmp_path / "dist" / "bundle.mjs"
+    path.parent.mkdir()
+    path.write_text("", encoding="utf-8")
+    os.utime(path, (1_000_000_000, 1_000_000_000))
+    return path
+
+
+def _counting(monkeypatch: pytest.MonkeyPatch) -> list:
+    scans: list = []
+    real = nb._sources_newer
+
+    def counting(built_at: float) -> bool:
+        scans.append(built_at)
+        return real(built_at)
+
+    monkeypatch.setattr(nb, "_sources_newer", counting)
+    return scans
+
+
+def test_낡지_않음은_잠시_기억(bundle: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+    scans = _counting(monkeypatch)
+    assert not nb.bundle_stale(bundle) and not nb.bundle_stale(bundle)
+    assert len(scans) == 1
+    # 묶음을 새로 지으면(mtime 바뀜) 다시 잼
+    os.utime(bundle, (1_000_000_100, 1_000_000_100))
+    assert not nb.bundle_stale(bundle) and len(scans) == 2
+    # 기억 시간이 지나면 다시 잼
+    monkeypatch.setattr(nb, "RECHECK_S", 0.0)
+    assert not nb.bundle_stale(bundle) and len(scans) == 3
+
+
+def test_낡음은_기억하지_않음(bundle: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+    source = nb.ROOT / "B05_Profile" / "x.ts"
+    source.parent.mkdir()
+    source.write_text("", encoding="utf-8")
+    scans = _counting(monkeypatch)
+    assert nb.bundle_stale(bundle) and nb.bundle_stale(bundle)
+    assert len(scans) == 2 and str(bundle) not in nb._FRESH