diff --git a/migrate.go b/migrate.go
index e7119c7..89bec4b 100644
--- a/migrate.go
+++ b/migrate.go
@@ -10,9 +10,6 @@ func runMigrations(database *sql.DB) {
 	migrations := []string{
 		`ALTER TABLE events ADD COLUMN description TEXT DEFAULT ''`,
 		`ALTER TABLE events ADD COLUMN user_id INTEGER REFERENCES users(id)`,
-		// Users may have email, phone, or both. Add whichever column is missing.
-		`ALTER TABLE users ADD COLUMN phone TEXT UNIQUE`,
-		`ALTER TABLE users ADD COLUMN email TEXT UNIQUE`,
 		// Verification codes use a generic identifier column.
 		`ALTER TABLE verification_codes ADD COLUMN identifier TEXT NOT NULL DEFAULT ''`,
 		// Indexes for auth tables (created here so they run after column migrations).
@@ -47,4 +44,56 @@ func runMigrations(database *sql.DB) {
 			log.Printf("migration warning: %v", err)
 		}
 	}
+
+	rebuildLegacyUsersTable(database)
+}
+
+// rebuildLegacyUsersTable migrates users tables from the phone-auth era
+// (phone NOT NULL, no email column). SQLite can't add a UNIQUE column or
+// drop NOT NULL via ALTER TABLE, so the table has to be rebuilt. Detected
+// by the missing email column.
+func rebuildLegacyUsersTable(database *sql.DB) {
+	var hasEmail int
+	err := database.QueryRow(
+		`SELECT COUNT(*) FROM pragma_table_info('users') WHERE name = 'email'`,
+	).Scan(&hasEmail)
+	if err != nil || hasEmail > 0 {
+		return
+	}
+
+	// Disable FK enforcement so DROP TABLE users doesn't cascade-delete
+	// sessions. main.go sets MaxOpenConns(1), so these pragmas apply to
+	// the same connection the transaction runs on.
+	database.Exec(`PRAGMA foreign_keys=OFF`)
+	defer database.Exec(`PRAGMA foreign_keys=ON`)
+
+	tx, err := database.Begin()
+	if err != nil {
+		log.Printf("users rebuild: %v", err)
+		return
+	}
+	defer tx.Rollback()
+
+	stmts := []string{
+		`CREATE TABLE users_new (
+			id         INTEGER PRIMARY KEY AUTOINCREMENT,
+			phone      TEXT    UNIQUE,
+			email      TEXT    UNIQUE,
+			name       TEXT    NOT NULL DEFAULT '',
+			created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
+		)`,
+		`INSERT INTO users_new (id, phone, name, created_at)
+			SELECT id, phone, name, created_at FROM users`,
+		`DROP TABLE users`,
+		`ALTER TABLE users_new RENAME TO users`,
+	}
+	for _, stmt := range stmts {
+		if _, err := tx.Exec(stmt); err != nil {
+			log.Printf("users rebuild: %v", err)
+			return
+		}
+	}
+	if err := tx.Commit(); err != nil {
+		log.Printf("users rebuild: %v", err)
+	}
 }