diff --git a/migrations/135_ask_events_observability.sql b/migrations/135_ask_events_observability.sql
index 884c80f..acb38f5 100644
--- a/migrations/135_ask_events_observability.sql
+++ b/migrations/135_ask_events_observability.sql
@@ -1,12 +1 @@
--- Phase E.1: ask_events 측정 필드 확장
--- answer_length/covered_aspects/missing_aspects/model_name/prompt_version 추가
--- E.3 (400→600자) 전후 비교 기준 + 단계 5 2-모델 체인 failure mode 분석 근거
-
-ALTER TABLE ask_events
-    ADD COLUMN IF NOT EXISTS answer_length INT,
-    ADD COLUMN IF NOT EXISTS covered_aspects JSONB,
-    ADD COLUMN IF NOT EXISTS missing_aspects JSONB,
-    ADD COLUMN IF NOT EXISTS model_name TEXT,
-    ADD COLUMN IF NOT EXISTS prompt_version TEXT;
-
-CREATE INDEX IF NOT EXISTS idx_ask_events_prompt_version ON ask_events(prompt_version);
+ALTER TABLE ask_events ADD COLUMN IF NOT EXISTS answer_length INT, ADD COLUMN IF NOT EXISTS covered_aspects JSONB, ADD COLUMN IF NOT EXISTS missing_aspects JSONB, ADD COLUMN IF NOT EXISTS model_name TEXT, ADD COLUMN IF NOT EXISTS prompt_version TEXT
diff --git a/migrations/136_ask_events_prompt_version_idx.sql b/migrations/136_ask_events_prompt_version_idx.sql
new file mode 100644
index 0000000..90ef675
--- /dev/null
+++ b/migrations/136_ask_events_prompt_version_idx.sql
@@ -0,0 +1 @@
+CREATE INDEX IF NOT EXISTS idx_ask_events_prompt_version ON ask_events(prompt_version)