diff --git a/.env.example b/.env.example
index 1f1e6c0..ebec073 100644
--- a/.env.example
+++ b/.env.example
@@ -12,7 +12,7 @@ RUNTIME_CPU_LIMIT=4
 RUNTIME_PIDS_LIMIT=256
 # Bound Node/Rolldown build parallelism inside the runtime container.
 RUNTIME_NODE_OPTIONS=--max-old-space-size=1536
-RUNTIME_RAYON_NUM_THREADS=2
+RUNTIME_RAYON_NUM_THREADS=1
 # Optional smoke-only limits used with compose.smoke.yaml (maximum supported defaults shown).
 # SMOKE_RUNTIME_MEMORY_LIMIT=4g
 # SMOKE_RUNTIME_MEMORY_SWAP_LIMIT=4g
diff --git a/README.md b/README.md
index fb63185..00b497a 100644
--- a/README.md
+++ b/README.md
@@ -29,7 +29,7 @@ runtime은 기본적으로 memory/swap 각각 4 GiB, CPU 4개, PID 256개 상한
 runtime 중지가 우선입니다.
 
 초기 빌드와 profile worktree 빌드는 기본 Node heap 1536 MiB,
-`RAYON_NUM_THREADS=2` 안에서 실행됩니다. `RUNTIME_NODE_OPTIONS`의 heap 상한은
+`RAYON_NUM_THREADS=1` 안에서 실행됩니다. `RUNTIME_NODE_OPTIONS`의 heap 상한은
 512~2048 MiB, `RUNTIME_RAYON_NUM_THREADS`는 1~4만 허용됩니다. 이는 빌드 중
 container hard limit에 먼저 닿는 것을 막고 실행 process에도 같은 상한을
 적용합니다.
diff --git a/compose.yaml b/compose.yaml
index ad71d2d..95e3ee0 100644
--- a/compose.yaml
+++ b/compose.yaml
@@ -50,7 +50,7 @@ services:
       CORE_SSH_PRIVATE_KEY_BASE64: ${CORE_SSH_PRIVATE_KEY_BASE64:-}
       CORE_SSH_KNOWN_HOSTS_BASE64: ${CORE_SSH_KNOWN_HOSTS_BASE64:-}
       NODE_OPTIONS: ${RUNTIME_NODE_OPTIONS:---max-old-space-size=1536}
-      RAYON_NUM_THREADS: ${RUNTIME_RAYON_NUM_THREADS:-2}
+      RAYON_NUM_THREADS: ${RUNTIME_RAYON_NUM_THREADS:-1}
       POSTGRES_HOST: postgres
       POSTGRES_PORT: '5432'
       POSTGRES_DB: ${POSTGRES_DB:-sammo}