diff --git a/resources/tester/test_241_1_input_cell_border.py b/resources/tester/test_241_1_input_cell_border.py
new file mode 100644
index 000000000..b40553c34
--- /dev/null
+++ b/resources/tester/test_241_1_input_cell_border.py
@@ -0,0 +1,36 @@
+"""PLAN 241-1 · 123 — B08 · B09 표 입력 칸 = 채움 색 대신 칸 안쪽 테두리."""
+
+import re
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[2]
+CSS = ROOT / "ui_template" / "ui_template_data_table.css"
+
+
+def _rule(css: str, selector: str) -> str:
+    m = re.search(re.escape(selector) + r" \{([^}]*)\}", css)
+    assert m, selector
+    return m.group(1)
+
+
+def test_입력_칸_채움_색_없고_안쪽_테두리():
+    body = _rule(CSS.read_text(encoding="utf-8"), ".ui-data-table__input")
+    assert "background: transparent;" in body
+    assert "color-mix" not in body  # 옛 accent 5% 채움 없음
+    assert "box-shadow: inset 0 0 0 1px var(--color-accent);" in body
+    assert "border: 0;" in body  # 테두리는 inset — 칸 크기 · 줄 높이 불변
+    assert "height: var(--dt-row-h);" in body
+
+
+def test_초점_테두리_그대로():
+    body = _rule(CSS.read_text(encoding="utf-8"), ".ui-data-table__input:focus")
+    assert "outline: 2px solid var(--color-focus-ring);" in body
+    assert "outline-offset: -2px;" in body
+
+
+def test_고친_값_색_칸_그대로():
+    css = (ROOT / "B09_Estimation" / "B09_Estimation_UI_Page.css").read_text(encoding="utf-8")
+    body = _rule(css, ".b09-estimation .ui-data-table__table tbody td.is-edited")
+    assert "color-mix(in srgb, var(--color-warning) 22%, var(--color-canvas))" in body
+    ts = (ROOT / "B09_Estimation" / "B09_Estimation_UI_Tabs_Bill.ts").read_text(encoding="utf-8")
+    assert '"is-edited"' in ts
diff --git a/ui_template/ui_template_data_table.css b/ui_template/ui_template_data_table.css
index f726d0827..0d20ed184 100644
--- a/ui_template/ui_template_data_table.css
+++ b/ui_template/ui_template_data_table.css
@@ -158,7 +158,7 @@
   box-shadow: inset 0 -2px 0 var(--color-accent);
 }
 
-/* 고칠 칸(PLAN 121) — 칸 가득 글 상자 · 숫자 오른쪽 맞춤 */
+/* 고칠 칸(PLAN 121 · 241-1) — 칸 가득 글 상자 · 숫자 오른쪽 맞춤 · 입력 칸 표시 = 채움 색 없이 칸 안쪽 테두리(칸 크기 불변) */
 .ui-data-table__table td.is-edit {
   padding: 0;
 }
@@ -168,7 +168,8 @@
   height: var(--dt-row-h);
   padding: 0 var(--spacing-8);
   border: 0;
-  background: color-mix(in srgb, var(--color-accent) 5%, var(--color-canvas));
+  background: transparent;
+  box-shadow: inset 0 0 0 1px var(--color-accent);
   color: inherit;
   font: inherit;
   font-variant-numeric: tabular-nums;