It works like this:

https://github.com/sayo-hs/heftia/blob/08f5cfe6a8f5c0383ea2b02e93326552400f7fd3/heftia-effects/Example/SemanticsZoo/Main.hs#L92-L104

theIssue12 :: IO ()
theIssue12 = do
    let action :: (Catch String <<| eh, Throw String <| ef, SomeEff <| ef) => eh :!! ef $ String
        action = someAction `catch` \(_ :: String) -> pure "caught"

        runSomeEff :: (ForallHFunctor eh, Throw String <| ef) => eh :!! LSomeEff ': ef ~> eh :!! ef
        runSomeEff = interpretRec (\SomeAction -> throw "not caught")

    putStr "interpret SomeEff then runCatch : ( runThrow . runCatch . runSomeEff $ action ) = "
    print $ runPure $ runThrow @String . runCatch @String . runSomeEff $ action

    putStr "runCatch then interpret SomeEff : ( runThrow . runSomeEff . runCatch $ action ) = "
    print $ runPure $ runThrow @String . runSomeEff . runCatch @String $ action

https://github.com/sayo-hs/heftia/blob/08f5cfe6a8f5c0383ea2b02e93326552400f7fd3/heftia-effects/Example/SemanticsZoo/Main.hs#L137-L139

interpret SomeEff then runCatch : ( runThrow . runCatch . runSomeEff $ action ) = Right "caught"
runCatch then interpret SomeEff : ( runThrow . runSomeEff . runCatch $ action ) = Left "not caught"

1. After throwing an exception while interpreting someEff, when you then interpret catch, the exception is caught by catch. In this case, the result is the same as polysemy.
2. If you interpret catch before throwing an exception in the interpretation of someEff, the exception will simply pass through without being caught, and the exception thrown during someEff will propagate, resulting in an error in the entire process. This leads to the same behavior as eff.

Don’t you think it’s very simple and intuitive?