diff --git a/packages/metaschema-schema/Makefile b/packages/metaschema-schema/Makefile
index a7a2d43c..c92ebad4 100644
--- a/packages/metaschema-schema/Makefile
+++ b/packages/metaschema-schema/Makefile
@@ -1,5 +1,5 @@
 EXTENSION = metaschema-schema
-DATA = sql/metaschema-schema--0.15.5.sql
+DATA = sql/metaschema-schema--0.31.0.sql
 
 PG_CONFIG = pg_config
 PGXS := $(shell $(PG_CONFIG) --pgxs)
diff --git a/packages/metaschema-schema/deploy/schemas/metaschema_public/tables/database/table.sql b/packages/metaschema-schema/deploy/schemas/metaschema_public/tables/database/table.sql
index fbfd17e7..624a811d 100644
--- a/packages/metaschema-schema/deploy/schemas/metaschema_public/tables/database/table.sql
+++ b/packages/metaschema-schema/deploy/schemas/metaschema_public/tables/database/table.sql
@@ -14,6 +14,10 @@ CREATE TABLE metaschema_public.database (
   
   hash uuid,
 
+  -- Singleton flag marking the platform (constructive) database itself.
+  -- Write-once: first row to set it wins; immutable once true.
+  platform boolean NOT NULL DEFAULT false,
+
   created_at timestamptz DEFAULT now(),
   updated_at timestamptz DEFAULT now(),
 
@@ -23,6 +27,10 @@ CREATE TABLE metaschema_public.database (
 ALTER TABLE metaschema_public.database
   ADD CONSTRAINT db_namechk CHECK (char_length(name) > 2);
 
+CREATE UNIQUE INDEX databases_database_platform_singleton_idx
+  ON metaschema_public.database (platform)
+  WHERE platform;
+
 COMMENT ON COLUMN metaschema_public.database.schema_hash IS '@omit';
 
 COMMIT;
diff --git a/packages/metaschema-schema/metaschema-schema.control b/packages/metaschema-schema/metaschema-schema.control
index 89b4acdd..c15713e3 100644
--- a/packages/metaschema-schema/metaschema-schema.control
+++ b/packages/metaschema-schema/metaschema-schema.control
@@ -1,6 +1,6 @@
 # metaschema-schema extension
 comment = 'metaschema-schema extension'
-default_version = '0.15.5'
+default_version = '0.31.0'
 module_pathname = '$libdir/metaschema-schema'
 requires = 'citext,hstore,pgpm-inflection,pgpm-database-jobs,pgpm-types,pgcrypto,plpgsql,postgis,uuid-ossp,pgpm-verify'
 relocatable = false
diff --git a/packages/metaschema-schema/sql/metaschema-schema--0.15.5.sql b/packages/metaschema-schema/sql/metaschema-schema--0.31.0.sql
similarity index 99%
rename from packages/metaschema-schema/sql/metaschema-schema--0.15.5.sql
rename to packages/metaschema-schema/sql/metaschema-schema--0.31.0.sql
index 79a4487d..21d914d1 100644
--- a/packages/metaschema-schema/sql/metaschema-schema--0.15.5.sql
+++ b/packages/metaschema-schema/sql/metaschema-schema--0.31.0.sql
@@ -36,6 +36,7 @@ CREATE TABLE metaschema_public.database (
   name text,
   label text,
   hash uuid,
+  platform boolean NOT NULL DEFAULT false,
   created_at timestamptz DEFAULT now(),
   updated_at timestamptz DEFAULT now(),
   UNIQUE (schema_hash)
@@ -45,6 +46,8 @@ ALTER TABLE metaschema_public.database
   ADD CONSTRAINT db_namechk 
     CHECK (char_length(name) > 2);
 
+CREATE UNIQUE INDEX databases_database_platform_singleton_idx ON metaschema_public.database (platform) WHERE platform;
+
 COMMENT ON COLUMN metaschema_public.database.schema_hash IS '@omit';
 
 CREATE TABLE metaschema_public.schema (
diff --git a/packages/metaschema-schema/verify/schemas/metaschema_public/tables/database/table.sql b/packages/metaschema-schema/verify/schemas/metaschema_public/tables/database/table.sql
index 2644ae25..387734c8 100644
--- a/packages/metaschema-schema/verify/schemas/metaschema_public/tables/database/table.sql
+++ b/packages/metaschema-schema/verify/schemas/metaschema_public/tables/database/table.sql
@@ -2,5 +2,6 @@
 BEGIN;
 
 SELECT verify_table ('metaschema_public.database');
+SELECT verify_index ('metaschema_public.database', 'databases_database_platform_singleton_idx');
 
 ROLLBACK;
diff --git a/packages/services/__tests__/__snapshots__/services.test.ts.snap b/packages/services/__tests__/__snapshots__/services.test.ts.snap
index 068e12f2..5bdc4077 100644
--- a/packages/services/__tests__/__snapshots__/services.test.ts.snap
+++ b/packages/services/__tests__/__snapshots__/services.test.ts.snap
@@ -8,6 +8,7 @@ exports[`services functionality should handle complete meta workflow with servic
   "label": null,
   "name": "my-meta-db",
   "owner_id": "[ID]",
+  "platform": false,
   "schema_hash": null,
   "updated_at": "[DATE]",
 }