diff --git a/app/game-api/src/router/tournament/index.ts b/app/game-api/src/router/tournament/index.ts
index 745513c7..810a7daf 100644
--- a/app/game-api/src/router/tournament/index.ts
+++ b/app/game-api/src/router/tournament/index.ts
@@ -103,6 +103,9 @@ const withTournamentBetClockMutation = async <T>(
 const tournamentBetCommandRequestId = (requestId: string | undefined, step: string): string | undefined =>
     requestId ? `${requestId}:tournamentBet:${step}` : undefined;
 
+const tournamentJoinCommandRequestId = (requestId: string | undefined, step: string): string | undefined =>
+    requestId ? `${requestId}:tournamentJoin:${step}` : undefined;
+
 const zTournamentState = z.object({
     stage: z.number().int().min(0),
     phase: z.number().int().min(0),
@@ -453,7 +456,9 @@ export const tournamentRouter = router({
 
         return { state, totals, myTotals, totalAmount, myAmount };
     }),
-    join: authedProcedure.mutation(async ({ ctx }) => {
+    // 참가비는 ENGINE transaction이 차감한다. API input-event transaction으로
+    // 감싸면 clock advisory lock을 쥔 채 child ENGINE event를 기다리게 된다.
+    join: engineAuthedProcedure.mutation(async ({ ctx }) => {
         const general = await getMyGeneral(ctx);
         const store = new TournamentStore(ctx.redis, buildTournamentKeys(ctx.profile.name));
         return withTournamentClockMutation(ctx, store, async () => {
@@ -476,6 +481,7 @@ export const tournamentRouter = router({
             const develCost = resolveCurrentDevelCost(worldState);
             const feeResult = await ctx.turnDaemon.requestCommand({
                 type: 'adjustGeneralResources',
+                requestId: tournamentJoinCommandRequestId(ctx.requestId, 'resources'),
                 reason: 'tournamentJoin',
                 adjustments: [{ generalId: general.id, goldDelta: -develCost, minGoldAfter: 0 }],
             });
@@ -511,6 +517,7 @@ export const tournamentRouter = router({
             } catch (error) {
                 await ctx.turnDaemon.requestCommand({
                     type: 'adjustGeneralResources',
+                    requestId: tournamentJoinCommandRequestId(ctx.requestId, 'projection-rollback-resources'),
                     reason: 'tournamentJoinRollback',
                     adjustments: [{ generalId: general.id, goldDelta: develCost }],
                 });
diff --git a/app/game-api/test/tournamentRouter.test.ts b/app/game-api/test/tournamentRouter.test.ts
index bd1845fa..c9639d1e 100644
--- a/app/game-api/test/tournamentRouter.test.ts
+++ b/app/game-api/test/tournamentRouter.test.ts
@@ -277,15 +277,33 @@ describe('tournament router permissions and mutations', () => {
             nextAt: '2026-07-26T01:00:00.000Z',
         });
         await redis.set('sammo:che:default:tournament:participants', '[]');
-        const caller = appRouter.createCaller(
-            buildContext({ redis, transport, generals: [general], userId: 'user-1', develCost: 200 })
-        );
+        const context = buildContext({
+            redis,
+            transport,
+            generals: [general],
+            userId: 'user-1',
+            develCost: 200,
+            requestId: 'http:tournament-join',
+        });
+        const outerApiTransaction = vi.fn(async () => {
+            throw new Error('tournament join must not hold an API transaction while waiting for the daemon');
+        });
+        Object.assign(context.db, { $transaction: outerApiTransaction });
+        const caller = appRouter.createCaller(context);
 
         await expect(caller.tournament.join()).resolves.toEqual({ ok: true, count: 1 });
         await expect(caller.tournament.join()).resolves.toEqual({ ok: true, count: 1 });
 
         expect(transport.gold.get(general.id)).toBe(1_800);
         expect(transport.commands.filter((command) => command.type === 'adjustGeneralResources')).toHaveLength(1);
+        expect(transport.commands).toContainEqual(
+            expect.objectContaining({
+                type: 'adjustGeneralResources',
+                requestId: 'http:tournament-join:tournamentJoin:resources',
+                reason: 'tournamentJoin',
+            })
+        );
+        expect(outerApiTransaction).not.toHaveBeenCalled();
         expect(transport.commands.filter((command) => command.type === 'setMySetting')).toHaveLength(0);
         const snapshot = await caller.tournament.getSnapshot();
         expect(snapshot.participants).toHaveLength(1);
diff --git a/docs/architecture/game-api-daemon-procedure-inventory.md b/docs/architecture/game-api-daemon-procedure-inventory.md
index 5e0353fe..cd0f5c55 100644
--- a/docs/architecture/game-api-daemon-procedure-inventory.md
+++ b/docs/architecture/game-api-daemon-procedure-inventory.md
@@ -17,7 +17,8 @@ transaction을 만든다. `engineAuthedProcedure`, `accessEngineAuthedProcedure`
 - **ENGINE 전환**: API는 actor/입력과 조기 오류를 읽을 뿐 durable DB 변경은 ENGINE
   transaction이 소유하고, ENGINE handler가 mutation 직전 mutable state를 다시 검증한다.
 - **혼합/saga 필요**: API DB write, Redis 원본 상태, 보상 명령 또는 API snapshot에서만
-  수행하는 권한/값 합성이 ENGINE 변경과 결합한다. procedure만 바꾸지 않는다.
+  수행하는 권한/값 합성이 ENGINE 변경과 결합한다. durable saga 없이는 단일 transaction으로
+  오인하지 않으며, ENGINE 완료를 기다리는 route는 API outer transaction을 열지 않는다.
 - **기존 ENGINE**: 이 inventory의 기존 기준선에서 이미 ENGINE procedure였고 API
   outer input event가 없었다.
 - **ENGINE 소유 + 불필요한 API outer**: gameplay durable mutation은 ENGINE이 전부
@@ -55,7 +56,7 @@ selection-pool create/reselect는 client request ID가 있을 때
 | route | 현재 procedure / outer transaction | 보류 근거 |
 | --- | --- | --- |
 | `messages.respond` | `authedProcedure`, action별 분기 (`app/game-api/src/router/messages/index.ts:318-372`) | `scout`/`raiseInvader`는 `messageRespond` ENGINE command가 처리하지만 `noAggression`/`cancelNA`/`stopWar`는 API transaction의 `respondToDiplomaticMessage` 경로가 처리한다. route 전체를 ENGINE-owned로 보지 않는다. |
-| `tournament.join`, `tournament.placeBet` | `authedProcedure`, outer 있음 (`app/game-api/src/router/tournament/index.ts:393-458`, `:515-620`) | PostgreSQL ENGINE resource/meta 명령과 Redis-owned participants/bets를 결합하고 실패 시 보상 ENGINE 명령을 보낸다. 하나의 DB transaction이 아니며 durable saga/Redis atomic revision이 필요하다. |
+| `tournament.join`, `tournament.placeBet` | `engineAuthedProcedure`, API outer 없음 (`app/game-api/src/router/tournament/index.ts`) | PostgreSQL ENGINE resource/meta 명령과 Redis-owned participants/bets를 결합하고 실패 시 보상 ENGINE 명령을 보낸다. API clock advisory lock을 잡은 채 child ENGINE transaction을 기다리지 않으며, command에는 HTTP request-scoped step ID를 전달한다. 여전히 하나의 DB transaction이 아니므로 durable saga/reconciliation이 필요하다. |
 
 합계 **3개 route**다.
 
@@ -93,6 +94,8 @@ selection-pool create/reselect는 client request ID가 있을 때
 - `app/game-api/test/troopRouter.test.ts`: troop mutation의 동일 계약을 검증한다.
 - `app/game-api/test/auctionRouter.test.ts`: auction mutation이 API transaction 없이
   daemon command와 Redis timer projection을 완료하는 계약을 검증한다.
+- `app/game-api/test/tournamentRouter.test.ts`: 참가·베팅이 API transaction을 열지 않고
+  request-scoped ENGINE command ID와 Redis mutation lock을 사용하는지 검증한다.
 - `app/game-api/test/inheritRouter.test.ts`,
   `app/game-engine/test/inheritanceActionPersistence.integration.test.ts`: 인증 actor, point/log,
   general/message 변경이 `inheritanceAction` ENGINE transaction에 함께 있는지 검증한다.