diff --git a/backend-spring/src/main/java/com/erp/migration/StartupSchemaMigrator.java b/backend-spring/src/main/java/com/erp/migration/StartupSchemaMigrator.java
index 44ec7040..195f1b4e 100644
--- a/backend-spring/src/main/java/com/erp/migration/StartupSchemaMigrator.java
+++ b/backend-spring/src/main/java/com/erp/migration/StartupSchemaMigrator.java
@@ -89,7 +89,80 @@ public class StartupSchemaMigrator {
             "ALTER TABLE DEPT_INFO DROP COLUMN IF EXISTS SALES_YN",
             "ALTER TABLE DEPT_INFO DROP COLUMN IF EXISTS SHOW_IN_CHART",
             "ALTER TABLE DEPT_INFO DROP COLUMN IF EXISTS ERP_MANAGED",
-            "ALTER TABLE DEPT_INFO DROP COLUMN IF EXISTS DATA_TYPE"
+            "ALTER TABLE DEPT_INFO DROP COLUMN IF EXISTS DATA_TYPE",
+
+            // RUN_086 (1) btree_gist 확장 — USER_SUBSTITUTES 의 EXCLUDE 제약 의존성
+            "CREATE EXTENSION IF NOT EXISTS btree_gist",
+
+            // RUN_086 (2) 대무자(代務者) 관리 테이블
+            //   self-위임 차단 (CHECK), 같은 쌍 활성 기간 겹침 차단 (EXCLUDE).
+            //   재실행 시 IF NOT EXISTS 로 안전. EXCLUDE/CHECK 제약은 첫 생성 때만 적용.
+            """
+            CREATE TABLE IF NOT EXISTS USER_SUBSTITUTES (
+                SUBSTITUTE_ID     BIGSERIAL    PRIMARY KEY,
+                COMPANY_CODE      VARCHAR(50)  NOT NULL,
+                ORIGINAL_USER_ID  VARCHAR(50)  NOT NULL,
+                PROXY_USER_ID     VARCHAR(50)  NOT NULL,
+                START_DATE        DATE         NULL,
+                END_DATE          DATE         NOT NULL,
+                REASON            VARCHAR(500),
+                IS_ACTIVE         BOOLEAN      NOT NULL DEFAULT TRUE,
+                CREATED_BY        VARCHAR(50),
+                CREATED_DATE      TIMESTAMP    NOT NULL DEFAULT NOW(),
+                UPDATED_BY        VARCHAR(50),
+                UPDATED_DATE      TIMESTAMP    NOT NULL DEFAULT NOW(),
+                CONSTRAINT chk_user_substitutes_self
+                    CHECK (ORIGINAL_USER_ID <> PROXY_USER_ID),
+                CONSTRAINT chk_user_substitutes_date
+                    CHECK (START_DATE IS NULL OR START_DATE <= END_DATE),
+                CONSTRAINT excl_user_substitutes_overlap
+                    EXCLUDE USING gist (
+                        COMPANY_CODE WITH =,
+                        ORIGINAL_USER_ID WITH =,
+                        PROXY_USER_ID WITH =,
+                        daterange(START_DATE, END_DATE, '[]') WITH &&
+                    ) WHERE (IS_ACTIVE = TRUE)
+            )
+            """,
+
+            // RUN_086 (3) USER_SUBSTITUTES 인덱스 — Filter 핫패스 + 조회 가속
+            "CREATE INDEX IF NOT EXISTS idx_user_substitutes_original ON USER_SUBSTITUTES (COMPANY_CODE, ORIGINAL_USER_ID, IS_ACTIVE)",
+            "CREATE INDEX IF NOT EXISTS idx_user_substitutes_proxy    ON USER_SUBSTITUTES (COMPANY_CODE, PROXY_USER_ID, IS_ACTIVE)",
+
+            // RUN_086 (4) SYSTEM_AUDIT_LOG — 처리자(actual processor) 분리 기록 컬럼
+            "ALTER TABLE SYSTEM_AUDIT_LOG ADD COLUMN IF NOT EXISTS PROCESSOR_ID   VARCHAR(50)",
+            "ALTER TABLE SYSTEM_AUDIT_LOG ADD COLUMN IF NOT EXISTS PROCESSOR_NAME VARCHAR(100)",
+
+            // RUN_086 (5) APPROVAL_PROXY_SETTINGS → USER_SUBSTITUTES 1회 데이터 복사 (idempotent)
+            //   기존 운영 데이터 보존 + 어댑터 read 경로가 즉시 동작하도록.
+            //   IS_ACTIVE 매핑: APPROVAL_PROXY_SETTINGS 의 CHAR('Y'/'N') → BOOLEAN.
+            //   메타데이터(created/updated) 는 원본 컬럼 의존 없이 'migration_086' + NOW() 로 고정
+            //   (APPROVAL_PROXY_SETTINGS 의 timestamp 컬럼명이 환경별로 다를 수 있어 안전한 default 채택).
+            """
+            INSERT INTO USER_SUBSTITUTES (
+                COMPANY_CODE, ORIGINAL_USER_ID, PROXY_USER_ID,
+                START_DATE, END_DATE, REASON, IS_ACTIVE,
+                CREATED_BY, CREATED_DATE, UPDATED_BY, UPDATED_DATE
+            )
+            SELECT
+                p.COMPANY_CODE, p.ORIGINAL_USER_ID, p.PROXY_USER_ID,
+                CAST(NULLIF(p.START_DATE, '') AS DATE),
+                CAST(NULLIF(p.END_DATE,   '') AS DATE),
+                p.REASON,
+                CASE WHEN p.IS_ACTIVE = 'Y' THEN TRUE ELSE FALSE END,
+                'migration_086', NOW(),
+                'migration_086', NOW()
+            FROM APPROVAL_PROXY_SETTINGS p
+            WHERE NULLIF(p.END_DATE, '') IS NOT NULL
+              AND NOT EXISTS (
+                SELECT 1 FROM USER_SUBSTITUTES s
+                WHERE s.COMPANY_CODE = p.COMPANY_CODE
+                  AND s.ORIGINAL_USER_ID = p.ORIGINAL_USER_ID
+                  AND s.PROXY_USER_ID = p.PROXY_USER_ID
+                  AND s.START_DATE IS NOT DISTINCT FROM CAST(NULLIF(p.START_DATE, '') AS DATE)
+                  AND s.END_DATE = CAST(NULLIF(p.END_DATE, '') AS DATE)
+            )
+            """
     );
 
     @EventListener(ApplicationReadyEvent.class)
diff --git a/db/migrations/RUN_086_MIGRATION.md b/db/migrations/RUN_086_MIGRATION.md
index 0d509abb..82ec4545 100644
--- a/db/migrations/RUN_086_MIGRATION.md
+++ b/db/migrations/RUN_086_MIGRATION.md
@@ -92,8 +92,11 @@ CREATE TABLE IF NOT EXISTS USER_SUBSTITUTES (
             COMPANY_CODE WITH =,
             ORIGINAL_USER_ID WITH =,
             PROXY_USER_ID WITH =,
-            daterange(COALESCE(START_DATE, CURRENT_DATE), END_DATE, '[]') WITH &&
+            daterange(START_DATE, END_DATE, '[]') WITH &&
         ) WHERE (IS_ACTIVE = TRUE)
+    -- daterange 의 lower bound 가 NULL 이면 -infinity. EXCLUDE 인덱스는
+    -- IMMUTABLE 함수만 허용하므로 COALESCE(.., CURRENT_DATE) 같은 STABLE 함수 사용 불가.
+    -- START_DATE NULL 인 같은 쌍 활성 row 들은 어쨌든 겹침으로 자연 차단됨.
 );
 
 -- 2. 인덱스
@@ -119,10 +122,8 @@ SELECT
     p.COMPANY_CODE, p.ORIGINAL_USER_ID, p.PROXY_USER_ID,
     p.START_DATE, p.END_DATE, p.REASON,
     CASE WHEN p.IS_ACTIVE = 'Y' THEN TRUE ELSE FALSE END,
-    COALESCE(p.CREATED_BY, 'migration_086'),
-    COALESCE(p.CREATED_DATE, NOW()),
-    COALESCE(p.UPDATED_BY, 'migration_086'),
-    COALESCE(p.UPDATED_DATE, NOW())
+    'migration_086', NOW(),
+    'migration_086', NOW()
 FROM APPROVAL_PROXY_SETTINGS p
 WHERE NOT EXISTS (
     SELECT 1 FROM USER_SUBSTITUTES s