diff --git a/migrations/0005_chapter_body_md_tts.sql b/migrations/0005_chapter_body_md_tts.sql
index cb69956..c0c608d 100644
--- a/migrations/0005_chapter_body_md_tts.sql
+++ b/migrations/0005_chapter_body_md_tts.sql
@@ -10,6 +10,3 @@
 -- whenever the author's beat-placement taste shifts.
 ALTER TABLE chapters
     ADD COLUMN body_md_tts text;
-
--- generation_runs.kind already accepts any string; no check
--- constraint to update. The new pass kind is 'narrate_prep'.
diff --git a/migrations/0006_generation_runs_narrate_prep.sql b/migrations/0006_generation_runs_narrate_prep.sql
new file mode 100644
index 0000000..025b87f
--- /dev/null
+++ b/migrations/0006_generation_runs_narrate_prep.sql
@@ -0,0 +1,9 @@
+-- Extend generation_runs.kind to allow the new narrate_prep pass.
+-- (Migration 0005 added body_md_tts but missed the check constraint.)
+-- Postgres doesn't support altering a check constraint in place,
+-- so we drop + re-add.
+ALTER TABLE generation_runs
+    DROP CONSTRAINT generation_runs_kind_check;
+ALTER TABLE generation_runs
+    ADD CONSTRAINT generation_runs_kind_check
+    CHECK (kind = ANY (ARRAY['gen', 'cleanup', 'audit', 'summary', 'embed', 'narrate_prep']));