diff --git a/.changeset/spec-notification-event-migration-id.md b/.changeset/spec-notification-event-migration-id.md
new file mode 100644
index 0000000000..786e4da2a7
--- /dev/null
+++ b/.changeset/spec-notification-event-migration-id.md
@@ -0,0 +1,11 @@
+---
+"@objectstack/spec": minor
+---
+
+`@objectstack/spec/system` now names the ADR-0030 notification cut-over, so "has this deployment run it?" has a place to be answered.
+
+`sys_migration` is the ledger a deployment writes to record that a data migration ran against its own database, and consumers read it instead of the platform version. Its well-known ids were `adr-0104-file-references` and `adr-0104-value-shapes` — the two ADR-0104 scans, both driven by an `os migrate` command that records the row. `migrateSysNotificationToEvent` (`@objectstack/metadata/migrations`) had none. It is destructive and one-way, operators are handed the call verbatim in `docs/handoff/adr-0030-notification-convergence.md`, and it recorded nothing when it ran: a deployment that performed the cut-over and one that never did are indistinguishable from the ledger. A row can only be keyed by an id, so without one the question had nowhere to be answered even in principle.
+
+Added: `NOTIFICATION_EVENT_MIGRATION_ID = 'adr-0030-notification-event'`, exported from `@objectstack/spec/system`. Purely additive — no existing export, schema or predicate changes, and nothing reads the new id yet.
+
+Deliberately NOT decided here, and the constant's docblock says so rather than leaving its silence to be read as an answer: what a `sys_migration` row under this id means. The two ADR-0104 ids get their `last_run_at` / `applied_at` / `verified_at` / `blocking` semantics from a command that scans, self-checks and only then records; this migration has no command and no self-check, and reports `migrated` / `already_done` / `not_applicable` / `error` to its caller instead. Which of those columns one of its runs may claim, whether anything may gate on the row, and whether a datastore created after the cut-over belongs in `CREATION_ATTESTED_MIGRATION_IDS`, are contract questions on this surface and are left open.
diff --git a/packages/spec/api-surface/system.json b/packages/spec/api-surface/system.json
index efec0a6ea6..39ed8694f4 100644
--- a/packages/spec/api-surface/system.json
+++ b/packages/spec/api-surface/system.json
@@ -444,6 +444,7 @@
     "MutualTLSConfig (type)",
     "MutualTLSConfigParsed (type)",
     "MutualTLSConfigSchema (const)",
+    "NOTIFICATION_EVENT_MIGRATION_ID (const)",
     "NavNodeLike (interface)",
     "NotificationChannel (type)",
     "NotificationChannelSchema (const)",
diff --git a/packages/spec/export-origins/system.json b/packages/spec/export-origins/system.json
index cfd6c1f57c..e00823c986 100644
--- a/packages/spec/export-origins/system.json
+++ b/packages/spec/export-origins/system.json
@@ -444,6 +444,7 @@
     "MutualTLSConfig": "src/system/auth-config.zod.ts#MutualTLSConfig (type)",
     "MutualTLSConfigParsed": "src/system/auth-config.zod.ts#MutualTLSConfigParsed (type)",
     "MutualTLSConfigSchema": "src/system/auth-config.zod.ts#MutualTLSConfigSchema (const)",
+    "NOTIFICATION_EVENT_MIGRATION_ID": "src/system/migration.zod.ts#NOTIFICATION_EVENT_MIGRATION_ID (const)",
     "NavNodeLike": "src/system/i18n-resolver.ts#NavNodeLike (interface)",
     "NotificationChannel": "src/system/notification.zod.ts#NotificationChannel (type)",
     "NotificationChannelSchema": "src/system/notification.zod.ts#NotificationChannelSchema (const)",
diff --git a/packages/spec/src/system/migration.zod.ts b/packages/spec/src/system/migration.zod.ts
index de1d58347b..db06f15093 100644
--- a/packages/spec/src/system/migration.zod.ts
+++ b/packages/spec/src/system/migration.zod.ts
@@ -169,6 +169,36 @@ export const FILE_REFERENCES_MIGRATION_ID = 'adr-0104-file-references';
  */
 export const VALUE_SHAPES_MIGRATION_ID = 'adr-0104-value-shapes';
 
+/**
+ * Well-known migration id: ADR-0030 notification convergence — this
+ * deployment's legacy per-user `sys_notification` inbox rows split into
+ * `sys_inbox_message` + `sys_notification_receipt`, and the `sys_notification`
+ * row itself rewritten to the L2 event shape, by `migrateSysNotificationToEvent`
+ * (`@objectstack/metadata/migrations`).
+ *
+ * Registered so that "has this cut-over run here?" is ANSWERABLE at all. The
+ * cut-over is destructive and one-way, it is handed to operators as a call they
+ * make themselves (`docs/handoff/adr-0030-notification-convergence.md`, under
+ * "Data migration (not auto-run)"), and it shipped with no id — so a deployment
+ * that ran it recorded nothing, and one that did not is indistinguishable from
+ * one that did. A ledger row can only be keyed by an id; without one the
+ * question has no place to be answered even in principle. That absence, not the
+ * migration, is what this constant repairs.
+ *
+ * WARNING — what a row under this id MEANS is deliberately NOT settled here,
+ * and its silence is not an answer. The two ids above are written by an
+ * `os migrate` command that scans, self-checks, and only then records, which is
+ * what gives `last_run_at` / `applied_at` / `verified_at` / `blocking` their
+ * meaning for them. This migration has no such command and no self-check: it
+ * reports `migrated` / `already_done` / `not_applicable` / `error` to its
+ * caller and nothing else. Which of those columns a run of it may legitimately
+ * claim, whether anything may gate on the row, and whether a datastore created
+ * after the cut-over belongs in {@link CREATION_ATTESTED_MIGRATION_IDS}, are
+ * open contract questions on this surface (#14025) — not facts this constant
+ * asserts, and not ones to settle by copying the neighbours above.
+ */
+export const NOTIFICATION_EVENT_MIGRATION_ID = 'adr-0030-notification-event';
+
 /**
  * The migrations a datastore attests at CREATION rather than by scanning.
  *