diff --git a/check_schemapurity.go b/check_schemapurity.go
new file mode 100644
index 0000000..af5a7bc
--- /dev/null
+++ b/check_schemapurity.go
@@ -0,0 +1,99 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strings"
+)
+
+func init() {
+	register(Check{
+		Seq:   310,
+		ID:    "32",
+		Title: "schema.sql contains only tables created by core migrations",
+		Run: func(ctx *ScanContext, rep *Reporter) {
+			schemaPath := filepath.Join(ctx.backendDir, "sql", "schema.sql")
+			migrationsDir := filepath.Join(ctx.backendDir, "sql", "migrations")
+			if !fileExists(schemaPath) || !dirExists(migrationsDir) {
+				rep.Skip("no backend/sql/schema.sql + migrations pair to check")
+				return
+			}
+
+			schemaTables, err := schemaCreatedTables(schemaPath)
+			if err != nil {
+				rep.Fatal("reading schema.sql: %v", err)
+				return
+			}
+			migrationTables, err := migrationCreatedTables(migrationsDir)
+			if err != nil {
+				rep.Fatal("reading migrations: %v", err)
+				return
+			}
+
+			var leaked []string
+			for table := range schemaTables {
+				if !migrationTables[table] {
+					leaked = append(leaked, table)
+				}
+			}
+			if len(leaked) > 0 {
+				sort.Strings(leaked)
+				rep.Fail("%d table(s) in schema.sql are not created by any core migration (plugin leakage; regenerate with `make schema`, which dumps a clean-room DB)", len(leaked))
+				for _, t := range leaked {
+					rep.Findingf("backend/sql/schema.sql — table %q has no CREATE TABLE in backend/sql/migrations", t)
+				}
+				return
+			}
+			rep.OK("all %d schema.sql tables originate from core migrations", len(schemaTables))
+		},
+	})
+}
+
+var schemaCreateTableRe = regexp.MustCompile(`(?im)^CREATE TABLE (?:IF NOT EXISTS )?(?:public\.)?([a-zA-Z0-9_]+)`)
+
+// Migrations are hand-written: CREATE TABLE may be indented (inside DO blocks
+// etc.), so no line anchor.
+var migrationCreateTableRe = regexp.MustCompile(`(?i)CREATE TABLE (?:IF NOT EXISTS )?(?:public\.)?([a-zA-Z0-9_]+)`)
+
+func schemaCreatedTables(path string) (map[string]bool, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	tables := map[string]bool{}
+	for _, m := range schemaCreateTableRe.FindAllStringSubmatch(string(data), -1) {
+		tables[strings.ToLower(m[1])] = true
+	}
+	return tables, nil
+}
+
+// migrationCreatedTables collects every table name a migration creates or
+// renames to, from both Up and Down sections (a superset is fine: the check
+// only flags schema.sql tables NO migration could have produced).
+var migrationRenameRe = regexp.MustCompile(`(?i)ALTER TABLE (?:IF EXISTS )?(?:ONLY )?(?:public\.)?[a-zA-Z0-9_]+ RENAME TO ([a-zA-Z0-9_]+)`)
+
+func migrationCreatedTables(dir string) (map[string]bool, error) {
+	tables := map[string]bool{"goose_db_version": true}
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return nil, err
+	}
+	for _, entry := range entries {
+		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".sql") {
+			continue
+		}
+		data, err := os.ReadFile(filepath.Join(dir, entry.Name()))
+		if err != nil {
+			return nil, err
+		}
+		for _, m := range migrationCreateTableRe.FindAllStringSubmatch(string(data), -1) {
+			tables[strings.ToLower(m[1])] = true
+		}
+		for _, m := range migrationRenameRe.FindAllStringSubmatch(string(data), -1) {
+			tables[strings.ToLower(m[1])] = true
+		}
+	}
+	return tables, nil
+}