diff --git a/.env.example b/.env.example
index 80b00b3..19c98a3 100644
--- a/.env.example
+++ b/.env.example
@@ -13,6 +13,7 @@ DISCORD_ARBITER_BOT_TOKEN=            # Arbiter bot
 # --- Agent type configuration ---
 OWNER_AGENT_TYPE=codex                # codex | claude-code
 REVIEWER_AGENT_TYPE=claude-code       # claude-code | codex
+# ARBITER_AGENT_TYPE=codex            # optional: codex | claude-code
 
 # --- API keys ---
 CLAUDE_CODE_OAUTH_TOKENS=             # Canonical comma-separated Claude Code OAuth tokens (use one value for single-account too)
@@ -85,8 +86,8 @@ STATUS_CHANNEL_ID=                    # Discord channel ID for live status updat
 # REVIEWER_EFFORT=high                  # Reviewer effort override
 # REVIEWER_FALLBACK_ENABLED=true        # Fall back to codex on Claude failure (default: true)
 #
-# ARBITER_MODEL=claude-opus-4-8         # Arbiter model override
-# ARBITER_EFFORT=high                   # Arbiter effort override
+# ARBITER_MODEL=gpt-5.5                 # Arbiter model override when ARBITER_AGENT_TYPE=codex
+# ARBITER_EFFORT=xhigh                  # Arbiter effort override
 # ARBITER_FALLBACK_ENABLED=true         # Fall back to codex on Claude failure (default: true)
 
 # --- Mixture of Agents (MoA) ---
diff --git a/docs/configuration.md b/docs/configuration.md
index 4fc1cd3..de2a1ea 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -27,7 +27,7 @@ DISCORD_ARBITER_BOT_TOKEN=
 # 역할별 provider
 OWNER_AGENT_TYPE=codex
 REVIEWER_AGENT_TYPE=claude-code
-# ARBITER_AGENT_TYPE=claude-code
+ARBITER_AGENT_TYPE=codex
 
 # provider 기본 모델
 # 공식 Claude API 모델 ID입니다.
@@ -46,14 +46,16 @@ REVIEWER_MODEL=claude-opus-4-8
 REVIEWER_EFFORT=high
 REVIEWER_FALLBACK_ENABLED=true
 
-ARBITER_MODEL=claude-opus-4-8
-ARBITER_EFFORT=high
+ARBITER_MODEL=gpt-5.5
+ARBITER_EFFORT=xhigh
 ARBITER_FALLBACK_ENABLED=true
 ```
 
 설명:
 
 - reviewer / arbiter provider 선택은 **전역 설정**
+- 역할별 `*_MODEL`은 해당 역할의 provider에 맞춰 주입됩니다. `codex` 역할에는 Codex 모델을, `claude-code` 역할에는 Claude 모델을 넣어야 합니다.
+- 예를 들어 `ARBITER_AGENT_TYPE=claude-code`로 바꾸면 그때 `ARBITER_MODEL=claude-opus-4-8`을 사용할 수 있습니다.
 - 특정 방에서만 reviewer를 Codex로 고르는 기능은 없음
 - room-level `agentConfig`의 `claudeModel`, `codexModel`은 역할별이 아니라 provider별 override
 - `ARBITER_AGENT_TYPE`은 옵션이며, 설정하지 않으면 arbiter는 비활성 상태입니다