`concurrent.interpreters.Interpreter.exec` propagate `SyntaxError`

Bug report

Bug description:

Hi,

I am testing the concurrent.interpreters feature from Python 3.14rc3 (the latest current rc).

The subinterpreter seems to behave in a surprising way when encountering syntax errors. For example, in the following code:

from concurrent import interpreters

interpr = interpreters.create()

def exec_catching_errors(code: str) -> None:
    try:
        interpr.exec(code)
    except interpreters.ExecutionFailed as e:
        print(f"There was an error: {e}")
    print("The function ends")


exec_catching_errors("print(1/0)")
exec_catching_errors("print 1")  # this is the surprising line

# the whole script dies with an uncaught SyntaxError

• trying to execute print(1/0) causes an interpreters.ExecutionFailed that correctly wraps a ZeroDivisionError.
• trying to execute print 1 causes a bare SyntaxError, whereas I would have expected a subclass of interpreters.InterpreterError wrapping the SyntaxError.

Is this intended behaviour, a bug, or something that simply needs to be better documented?

Thanks

CPython versions tested on:

3.14

Operating systems tested on:

Linux

Start with the implementation of concurrent.interpreters.Interpreter.exec and reproduce the two code snippets from the report on Python 3.14. Determine the intended handling of SyntaxError versus ExecutionFailed, then add or update focused tests so the behavior is explicit and consistent.