Support for record was added in JShell for JDK-14.

Reproduced as follows...

In JDK-13 jshell tool do:

jshell> /set mode bug normal -command
| Created new feedback mode: bug

jshell> /set mode -retain bug

In JDK-14 jshell tool (passed --enable-preview) do:

jshell> /set feedback bug
| Feedback mode: bug

jshell> interface Expr {}
| created interface Expr

jshell> public record ConstExpr(Expr e) implements Expr{}
| created method ConstExpr()

Note: records are called methods in this and other cases.

There are at least two issues here:
(1) rather than catching the error, it seems to fail down to the next format.
(2) there is no support for upgrading old mode definitions

Work-around for now: Either rebuild the custom mode from a built-in mode or edit the custom mode to handle all places that "record" is present in new built-in modes (5 places).