diff --git a/A00_Common/design/design_structure_form.ts b/A00_Common/design/design_structure_form.ts
index 1448cc72e..fac7319a8 100644
--- a/A00_Common/design/design_structure_form.ts
+++ b/A00_Common/design/design_structure_form.ts
@@ -124,6 +124,10 @@ export function createSpecForm(links: SpecLinks | null, hooks: SpecFormHooks = {
     return slot;
   };
 
+  /** 관경 빈칸 = 빈 보기 그대로 — 기본값 1000 을 몰래 채우지 않음(505-4 · 295). */
+  const blankKept = (c: SpecContainer, item: SpecItem): boolean =>
+    spec?.typeId === "pipe" && c.id === "pipe" && item.id === "diameter";
+
   const control = (
     c: SpecContainer,
     item: SpecItem,
@@ -140,7 +144,7 @@ export function createSpecForm(links: SpecLinks | null, hooks: SpecFormHooks = {
       const blank = !tag ? "" : name ? `${name} (${tag})` : tag;
       // 필수 상자 = 빈 보기 없음(54-43) · 선택 상자 빈 보기 = 빈 글
       select.replaceChildren(
-        ...(c.required && !tag ? [] : [new Option(blank, "")]),
+        ...(c.required && !tag && !blankKept(c, item) ? [] : [new Option(blank, "")]),
         ...choices.map((ch) => new Option(choiceLabel(c, item, ch, names), ch.value)),
       );
       // 선택지 밖 옛 값은 그 값만 남겨 보임(지운 값을 몰래 바꾸지 않음)
@@ -223,6 +227,7 @@ export function createSpecForm(links: SpecLinks | null, hooks: SpecFormHooks = {
       for (const item of c.items) {
         if (item.kind !== "select" || values[item.id] || (item.by && !branchOf(item, values)))
           continue;
+        if (blankKept(c, item)) continue;
         const choices = choicesOf(item, values);
         const key = branchOf(item, values)?.key;
         const wanted = String((key ? defaults[key] : undefined) ?? item.default ?? "");
diff --git a/B05_Profile/B05_Profile_UI_RouteEdit.ts b/B05_Profile/B05_Profile_UI_RouteEdit.ts
index 520474528..f3a802301 100644
--- a/B05_Profile/B05_Profile_UI_RouteEdit.ts
+++ b/B05_Profile/B05_Profile_UI_RouteEdit.ts
@@ -191,7 +191,8 @@ export async function mountRouteEditor(
       station_interval_m: stationIntervalM,
       station_snap: stationSnap,
     }),
-    onShown: () => draw(), // 횡단이 뜨면 그 측점 반폭 선을 그린다.
+    // 횡단이 뜨면 그 측점 반폭 선을 그린다 — 새로 고침 뒤 고른 측점은 만드는 도중 불려 아래 선언이 아직이라 한 박자 뒤에(505-4).
+    onShown: () => queueMicrotask(draw),
   });
   /** 구간 재기 — 계획·예상 노선 위 두 점. 셈·서버 묻기는 `_Measure` 몫(계획서 0-9 ⑤). */
   const measure = createMeasureTool({
diff --git a/resources/tester/test_505_4_refresh_blank_pipe.py b/resources/tester/test_505_4_refresh_blank_pipe.py
new file mode 100644
index 000000000..7921a19da
--- /dev/null
+++ b/resources/tester/test_505_4_refresh_blank_pipe.py
@@ -0,0 +1,102 @@
+"""PLAN 505-4 — 구조물 고른 채 새로 고침 = 평면 편집기 뜸 · 빈 관경 = 빈 선택지(값 안 채움).
+
+글 시험 = 소스 순서 · 화면 시험 = 자기 포트(5179) Playwright 머리 없는 브라우저 · 서버가 떠 있을 때만 · 검증_sub4.
+
+  ./venv/Scripts/python.exe -m pytest resources/tester/test_505_4_refresh_blank_pipe.py -q
+"""
+
+from __future__ import annotations
+
+import json
+import urllib.request
+from pathlib import Path
+
+import pytest
+
+ROOT = Path(__file__).resolve().parents[2]
+BASE = "http://localhost:5179"
+PROJECT = "c725d747-50ae-46b0-87ce-4d4e56a53cf3"  # 검증_sub4(OWNERS.md)
+LIST_URL = f"{BASE}/api/projects/{PROJECT}/route/structures"
+
+
+def _read(*parts: str) -> str:
+    return ROOT.joinpath(*parts).read_text(encoding="utf-8")
+
+
+def test_횡단_뜸_콜백은_만드는_도중_안_그림() -> None:
+    edit = _read("B05_Profile", "B05_Profile_UI_RouteEdit.ts")
+    # createCrossPreview 가 고른 측점을 만들며 곧바로 부름 — draw 는 아래 선언(closed · view)이 선 뒤에
+    assert "onShown: () => queueMicrotask(draw)," in edit
+    assert "onShown: () => draw()" not in edit
+    assert edit.index("const crossPreview = createCrossPreview(") < edit.index(
+        "let closed = false;"
+    )
+
+
+def test_관경_빈칸은_빈_보기_채움_없음() -> None:
+    form = _read("A00_Common", "design", "design_structure_form.ts")
+    assert 'spec?.typeId === "pipe" && c.id === "pipe" && item.id === "diameter"' in form
+    assert "c.required && !tag && !blankKept(c, item) ? [] : [new Option(blank," in form
+    fill = form.index("필수 상자 빈 고르기 칸 = 정의 기본값")
+    assert form.index("if (blankKept(c, item)) continue;", fill) < form.index(
+        "values[item.id] =", fill
+    )
+
+
+def _up() -> bool:
+    try:
+        urllib.request.urlopen(BASE, timeout=3)
+        return True
+    except Exception:
+        return False
+
+
+JS_DIAMETER = """() => [...document.querySelectorAll('select')]
+  .filter((s) => s.offsetParent && [...s.options].some((o) => o.value === '800'))
+  .map((s) => ({ value: s.value, first: s.options[0].value, count: s.options.length }))"""
+JS_CANVAS = """() => {
+  const c = document.querySelector('.b05-routeedit__canvas');
+  const d = c.getContext('2d').getImageData(0, 0, c.width, c.height).data;
+  let n = 0;
+  for (let i = 3; i < d.length; i += 4) if (d[i] > 0) n += 1;
+  return { visible: !!c.offsetParent, painted: n };
+}"""
+
+
+@pytest.mark.skipif(not _up(), reason="5179 서버 없음")
+def test_화면_새로_고침_편집기_뜸_빈_관경_빈_선택지() -> None:
+    sync = pytest.importorskip("playwright.sync_api")
+    cred = json.loads((ROOT / "tmp" / "aislo_cred.json").read_text(encoding="utf-8"))
+    with sync.sync_playwright() as play:
+        chrome = play.chromium.launch(channel="msedge", headless=True)
+        try:
+            ctx = chrome.new_context(viewport={"width": 1600, "height": 1000})
+            login = {k: cred[k] for k in ("email", "password")}
+            assert ctx.request.post(f"{BASE}/api/auth/login/request", data=login, timeout=60000).ok
+            tab = ctx.new_page()
+            errors: list[str] = []
+            tab.on("pageerror", lambda e: errors.append(str(e)))
+            tab.add_init_script(f"localStorage.setItem('frd_current_project_id', '{PROJECT}')")
+            tab.goto(f"{BASE}/#/b05-profile", wait_until="domcontentloaded")
+            tab.wait_for_function("() => !!window.__aisloPipeline", timeout=90000)
+            tab.wait_for_timeout(8000)
+            before = ctx.request.get(LIST_URL).text()
+            # 관경 빈칸 관(19+8) — 빈 선택지 · 값 안 채움
+            tab.locator(".b05-route__irregular-item", has_text="19+8").first.click()
+            tab.wait_for_timeout(3000)
+            if not tab.evaluate(JS_DIAMETER):
+                tab.get_by_text("구조물 배치", exact=True).click()
+                tab.wait_for_timeout(1500)
+            assert tab.evaluate(JS_DIAMETER) == [{"value": "", "first": "", "count": 5}]
+            assert ctx.request.get(LIST_URL).text() == before  # 열기만 — 저장 값 그대로
+            # 고른 채 새로 고침 — 편집기가 뜸(전엔 `closed` 선언 전 씀으로 멈춤)
+            errors.clear()
+            tab.reload(wait_until="domcontentloaded")
+            tab.wait_for_function("() => !!window.__aisloPipeline", timeout=90000)
+            tab.wait_for_timeout(9000)
+            assert not [e for e in errors if "before initialization" in e], errors
+            canvas = tab.evaluate(JS_CANVAS)
+            assert canvas["visible"] and canvas["painted"] > 0
+            assert ctx.request.get(LIST_URL).text() == before
+        finally:
+            chrome.close()