diff --git a/src/core/abut/edit.ts b/src/core/abut/edit.ts
index d39b04f..d859be6 100644
--- a/src/core/abut/edit.ts
+++ b/src/core/abut/edit.ts
@@ -12,6 +12,7 @@ import { footingRebarIssues, resolveFootingRebar, type AbutFootingRebarSettings
 import { resolveWallRebar, wallRebarIssues, type AbutWallRebarSettings } from './rebar/wall';
 import { parapetRebarIssues, resolveParapetRebar, type AbutParapetRebarSettings } from './rebar/parapet';
 import { resolveWingRebar, wingRebarIssues, type AbutWingRebarSettings } from './rebar/wing';
+import { resolveSlabRebar, slabRebarIssues, type AbutSlabRebarSettings } from './rebar/slab';
 import { abutBearingRuleIssues, resolveBearingRule, type AbutBearingRule } from './bearing-table';
 
 export type AbutEditKey = 'seatEl' | 'foundationBottomEl' | 'groundEl' | 'pileLengthMm' | 'skewDeg' | 'slopeI';
@@ -211,6 +212,16 @@ export function applyWingRebar(rec: AbutRecord, patch: Partial<AbutWingRebarSett
   return { ...rec, rebar: { ...(rec.rebar ?? {}), wing } };
 }
 
+/** Changes ③ 접속슬래브 배근 values (only the changed ones are kept; undefined clears one), refused with a Korean message. */
+export function applySlabRebar(rec: AbutRecord, patch: Partial<AbutSlabRebarSettings>): AbutRecord {
+  for (const v of Object.values(patch)) if (typeof v === 'number' && !Number.isFinite(v)) throw new Error('숫자를 입력하세요.');
+  const slab: Partial<AbutSlabRebarSettings> = { ...(rec.rebar?.slab ?? {}), ...patch };
+  for (const key of Object.keys(slab) as (keyof AbutSlabRebarSettings)[]) if (slab[key] === undefined) delete slab[key];
+  const issues = slabRebarIssues(resolveSlabRebar(slab));
+  if (issues.length > 0) throw new Error(issues[0]);
+  return { ...rec, rebar: { ...(rec.rebar ?? {}), slab } };
+}
+
 /** Changes one 접속슬래브 dim, refused with a Korean message when the slab would not build. */
 export function applySlabEdit(rec: AbutRecord, key: (typeof SLAB_EDIT_FIELDS)[number]['key'], value: number): AbutRecord {
   if (!Number.isFinite(value)) throw new Error('숫자를 입력하세요.');
diff --git a/src/core/abut/parse.ts b/src/core/abut/parse.ts
index c763728..7cd38d3 100644
--- a/src/core/abut/parse.ts
+++ b/src/core/abut/parse.ts
@@ -19,6 +19,7 @@ import type { AbutFootingRebarSettings } from './rebar/footing';
 import type { AbutWallRebarSettings } from './rebar/wall';
 import type { AbutParapetRebarSettings } from './rebar/parapet';
 import type { AbutWingRebarSettings } from './rebar/wing';
+import type { AbutSlabRebarSettings } from './rebar/slab';
 
 type Cell = string | number | null | undefined;
 type Grid = Cell[][];
@@ -70,7 +71,7 @@ export interface AbutRecord {
   /** 지반·지층 입력 (② 지반·지층 카드, 교각과 같은 필드). Absent = 육상, 지하수위 없음, 지층 행 없음. */
   ground?: AbutGround;
   /** ③ 배근 입력 (부재별, 바꾼 값만). Absent = 엑셀 Abut 시트 기본값. */
-  rebar?: { footing?: Partial<AbutFootingRebarSettings>; wall?: Partial<AbutWallRebarSettings>; parapet?: Partial<AbutParapetRebarSettings>; wing?: Partial<AbutWingRebarSettings> };
+  rebar?: { footing?: Partial<AbutFootingRebarSettings>; wall?: Partial<AbutWallRebarSettings>; parapet?: Partial<AbutParapetRebarSettings>; wing?: Partial<AbutWingRebarSettings>; slab?: Partial<AbutSlabRebarSettings> };
   /** 예전 "좌우 같게" 값 (2026-11-04 이전 파일). 지금은 읽기만 하고 쓰지 않는다. */
   wingsLinked?: boolean;
 }
diff --git a/src/core/project.ts b/src/core/project.ts
index e78f46f..1d6fb31 100644
--- a/src/core/project.ts
+++ b/src/core/project.ts
@@ -177,6 +177,9 @@ export function checkStoredAbutments(list: unknown): void {
       for (const [key, v] of Object.entries(a.rebar.wing ?? {})) {
         if (!finite(v)) throw new Error(`${who}: 날개벽 배근 값 ${key}이(가) 맞지 않습니다.`);
       }
+      for (const [key, v] of Object.entries(a.rebar.slab ?? {})) {
+        if (!finite(v)) throw new Error(`${who}: 접속슬래브 배근 값 ${key}이(가) 맞지 않습니다.`);
+      }
     }
     if (a.wingsLinked !== undefined && typeof a.wingsLinked !== 'boolean') throw new Error(`${who}: 좌우 같게 값이 맞지 않습니다.`);
     if (a.wings !== undefined) {
diff --git a/tests/abut-rebar-slab.test.ts b/tests/abut-rebar-slab.test.ts
index 8881ec0..dd6b87a 100644
--- a/tests/abut-rebar-slab.test.ts
+++ b/tests/abut-rebar-slab.test.ts
@@ -106,3 +106,21 @@ describe('교대 접속슬래브 배근 A1 (AD8, 교대접속슬래브철근.md
     expect(r3.pts.length).toBeGreaterThan(2); // 헌치 · 벽체 배면에서 꺾임
   });
 });
+
+import { applySlabRebar } from '../src/core/abut/edit';
+import { checkStoredAbutments } from '../src/core/project';
+
+describe('③ 접속슬래브 배근 입력 저장', () => {
+  it('stores only the changed values; undefined links a group back; refuses bad values', () => {
+    const a = applySlabRebar(rec, { sMain: 200, k8: 6 });
+    expect(a.rebar?.slab).toEqual({ sMain: 200, k8: 6 });
+    expect(applySlabRebar(a, { sMain: undefined }).rebar?.slab).toEqual({ k8: 6 });
+    expect(() => applySlabRebar(rec, { k8: 1.5 })).toThrow('R8 배수');
+    expect(() => applySlabRebar(rec, { cv: 0 })).toThrow();
+  });
+
+  it('the project file keeps the 접속슬래브 input and refuses a non-number', () => {
+    expect(() => checkStoredAbutments([applySlabRebar(rec, { c: 90 })])).not.toThrow();
+    expect(() => checkStoredAbutments([{ ...rec, rebar: { slab: { c: 'x' } } as never }])).toThrow('접속슬래브 배근');
+  });
+});