diff --git a/doc/notes/plutus-core/cek-budgeting-profiling/CostingDetails.md b/doc/notes/plutus-core/cek-budgeting-profiling/CostingDetails.md
index 173dccdf2de..73af0aaba22 100644
--- a/doc/notes/plutus-core/cek-budgeting-profiling/CostingDetails.md
+++ b/doc/notes/plutus-core/cek-budgeting-profiling/CostingDetails.md
@@ -70,7 +70,7 @@ instance (Eq fun, Hashable fun, ToExMemory term) =>
             Restricting resb ->
                 when (exceedsBudget resb newBudget) $
                     throwingWithCause _EvaluationError
-                        (UserEvaluationError $ CekOutOfExError resb newBudget)
+                        (OperationalEvaluationError $ CekOutOfExError resb newBudget)
                         Nothing  -- No value available for error
 ```
 
@@ -96,7 +96,7 @@ to the current mode:
                 newBudget <- exBudgetStateBudget <%= (<> budget)
                 when (exceedsBudget resb newBudget) $
                     throwingWithCause _EvaluationError
-                        (UserEvaluationError $ CekOutOfExError resb newBudget)
+                        (OperationalEvaluationError $ CekOutOfExError resb newBudget)
                         Nothing
 ```
 
@@ -114,7 +114,7 @@ of memory very quickly.  Changing the code to
             Restricting resb -> 
                 when (exceedsBudget resb newBudget) $
                     throwingWithCause _EvaluationError
-                        (UserEvaluationError $ CekOutOfExError resb newBudget)
+                        (OperationalEvaluationError $ CekOutOfExError resb newBudget)
                         Nothing
 ```
 
diff --git a/plutus-benchmark/nofib/exe/Main.hs b/plutus-benchmark/nofib/exe/Main.hs
index ca88a42c653..c2dd8e7e9c3 100644
--- a/plutus-benchmark/nofib/exe/Main.hs
+++ b/plutus-benchmark/nofib/exe/Main.hs
@@ -202,7 +202,7 @@ options = hsubparser
 ---------------- Evaluation ----------------
 
 evaluateWithCek :: UPLC.Term UPLC.NamedDeBruijn DefaultUni DefaultFun () -> UPLC.EvaluationResult (UPLC.Term UPLC.NamedDeBruijn DefaultUni DefaultFun ())
-evaluateWithCek = UPLC.unsafeExtractEvaluationResult . (\(fstT,_,_) -> fstT) . UPLC.runCekDeBruijn PLC.defaultCekParameters UPLC.restrictingEnormous UPLC.noEmitter
+evaluateWithCek = UPLC.unsafeToEvaluationResult . (\(fstT,_,_) -> fstT) . UPLC.runCekDeBruijn PLC.defaultCekParameters UPLC.restrictingEnormous UPLC.noEmitter
 
 writeFlatNamed :: UPLC.Program UPLC.NamedDeBruijn DefaultUni DefaultFun () -> IO ()
 writeFlatNamed prog = BS.putStr . Flat.flat . UPLC.UnrestrictedProgram $ prog
diff --git a/plutus-core/changelog.d/20240517_191403_effectfully_polish_evaluation_errors.md b/plutus-core/changelog.d/20240517_191403_effectfully_polish_evaluation_errors.md
new file mode 100644
index 00000000000..fb19345a29b
--- /dev/null
+++ b/plutus-core/changelog.d/20240517_191403_effectfully_polish_evaluation_errors.md
@@ -0,0 +1,7 @@
+### Removed
+
+- `unsafeRunCekNoEmit` and all `unsafeEvaluate*` functions in #6043. To replace e.g. `unsafeEvaluateCek` you can use `evaluateCek` in combination with `unsafeToEvaluationResult`.
+
+### Changed
+
+- Renamed `unsafeExtractEvaluationResult` to `unsafeToEvaluationResult`.
diff --git a/plutus-core/cost-model/budgeting-bench/Common.hs b/plutus-core/cost-model/budgeting-bench/Common.hs
index a314102ffda..617307cf454 100644
--- a/plutus-core/cost-model/budgeting-bench/Common.hs
+++ b/plutus-core/cost-model/budgeting-bench/Common.hs
@@ -78,13 +78,11 @@ benchWith
     -> String
     -> PlainTerm DefaultUni fun
     -> Benchmark
-benchWith params name term = bench name $ whnf (unsafeEvaluateCekNoEmit params) term
-{- ^ Note that to get sensible results with whnf, we must use an evaluation
-   function that looks at the result, so eg unsafeEvaluateCek won't work
-   properly because it returns a pair whose components won't be evaluated by
-   whnf.  We can't use nf because it does too much work: for instance if it gets
-   back a 'Data' value it'll traverse all of it.
--}
+-- Note that to get sensible results with 'whnf', we must use an evaluation function that looks at
+-- the result, so e.g. 'evaluateCek' won't work properly because it returns a pair whose components
+-- won't be evaluated by 'whnf'. We can't use 'nf' because it does too much work: for instance if it
+-- gets back a 'Data' value it'll traverse all of it.
+benchWith params name term = bench name $ whnf (evaluateCekNoEmit params) term
 
 benchDefault :: String -> PlainTerm DefaultUni DefaultFun -> Benchmark
 benchDefault = benchWith defaultCekParameters
diff --git a/plutus-core/plutus-core/src/PlutusCore/Evaluation/ErrorWithCause.hs b/plutus-core/plutus-core/src/PlutusCore/Evaluation/ErrorWithCause.hs
index 15d3123338e..32bdc30d797 100644
--- a/plutus-core/plutus-core/src/PlutusCore/Evaluation/ErrorWithCause.hs
+++ b/plutus-core/plutus-core/src/PlutusCore/Evaluation/ErrorWithCause.hs
@@ -37,11 +37,14 @@ instance (Pretty err, Pretty cause) => Pretty (ErrorWithCause err cause) where
 
 instance (PrettyBy config cause, PrettyBy config err) =>
             PrettyBy config (ErrorWithCause err cause) where
-    prettyBy config (ErrorWithCause err mayCause) =
-        "An error has occurred: " <+> prettyBy config err <>
-            case mayCause of
-                Nothing    -> mempty
-                Just cause -> hardline <> "Caused by:" <+> prettyBy config cause
+    prettyBy config (ErrorWithCause err mayCause) = fold
+        [ "An error has occurred:"
+        , hardline
+        , prettyBy config err
+        , case mayCause of
+            Nothing    -> mempty
+            Just cause -> hardline <> "Caused by:" <+> prettyBy config cause
+        ]
 
 instance (PrettyPlc cause, PrettyPlc err) =>
             Show (ErrorWithCause err cause) where
diff --git a/plutus-core/plutus-core/src/PlutusCore/Evaluation/Machine/Ck.hs b/plutus-core/plutus-core/src/PlutusCore/Evaluation/Machine/Ck.hs
index e188b2cfa73..d1b7abab36f 100644
--- a/plutus-core/plutus-core/src/PlutusCore/Evaluation/Machine/Ck.hs
+++ b/plutus-core/plutus-core/src/PlutusCore/Evaluation/Machine/Ck.hs
@@ -17,12 +17,11 @@ module PlutusCore.Evaluation.Machine.Ck
     , CkEvaluationException
     , CkM
     , CkValue
-    , extractEvaluationResult
     , runCk
+    , extractEvaluationResult
+    , unsafeToEvaluationResult
     , evaluateCk
     , evaluateCkNoEmit
-    , unsafeEvaluateCk
-    , unsafeEvaluateCkNoEmit
     , readKnownCk
     ) where
 
@@ -195,7 +194,7 @@ stack |> Constr _ ty i es               = case es of
     t : ts -> FrameConstr ty i ts [] : stack |> t
 stack |> Case _ _ arg cs         = FrameCase cs : stack |> arg
 _     |> Error{}                 =
-    throwingWithCause _EvaluationError (UserEvaluationError CkEvaluationFailure) Nothing
+    throwingWithCause _EvaluationError (OperationalEvaluationError CkEvaluationFailure) Nothing
 _     |> var@Var{}               =
     throwingWithCause _MachineError OpenTermEvaluatedMachineError $ Just var
 
@@ -312,22 +311,6 @@ evaluateCkNoEmit
     -> Either (CkEvaluationException uni fun) (Term TyName Name uni fun ())
 evaluateCkNoEmit runtime = fst . runCk runtime False
 
--- | Evaluate a term using the CK machine with logging enabled. May throw a 'CkEvaluationException'.
-unsafeEvaluateCk
-    :: ThrowableBuiltins uni fun
-    => BuiltinsRuntime fun (CkValue uni fun)
-    -> Term TyName Name uni fun ()
-    -> (EvaluationResult (Term TyName Name uni fun ()), [Text])
-unsafeEvaluateCk runtime = first unsafeExtractEvaluationResult . evaluateCk runtime
-
--- | Evaluate a term using the CK machine with logging disabled. May throw a 'CkEvaluationException'.
-unsafeEvaluateCkNoEmit
-    :: ThrowableBuiltins uni fun
-    => BuiltinsRuntime fun (CkValue uni fun)
-    -> Term TyName Name uni fun ()
-    -> EvaluationResult (Term TyName Name uni fun ())
-unsafeEvaluateCkNoEmit runtime = unsafeExtractEvaluationResult . evaluateCkNoEmit runtime
-
 -- | Unlift a value using the CK machine.
 readKnownCk
     :: ReadKnown (Term TyName Name uni fun ()) a
diff --git a/plutus-core/plutus-core/src/PlutusCore/Evaluation/Machine/Exception.hs b/plutus-core/plutus-core/src/PlutusCore/Evaluation/Machine/Exception.hs
index 354750cc82c..bd10f0267fe 100644
--- a/plutus-core/plutus-core/src/PlutusCore/Evaluation/Machine/Exception.hs
+++ b/plutus-core/plutus-core/src/PlutusCore/Evaluation/Machine/Exception.hs
@@ -29,7 +29,7 @@ module PlutusCore.Evaluation.Machine.Exception
     , throwing_
     , throwingWithCause
     , extractEvaluationResult
-    , unsafeExtractEvaluationResult
+    , unsafeToEvaluationResult
     ) where
 
 import PlutusPrelude
@@ -55,9 +55,9 @@ data MachineError fun
     | OpenTermEvaluatedMachineError
       -- ^ An attempt to evaluate an open term.
     | UnliftingMachineError UnliftingError
-      -- ^ An attempt to compute a constant application resulted in 'ConstAppError'.
+      -- ^ An attempt to compute a constant application resulted in 'UnliftingError'.
     | BuiltinTermArgumentExpectedMachineError
-      -- ^ A builtin expected a term argument, but something else was received
+      -- ^ A builtin expected a term argument, but something else was received.
     | UnexpectedBuiltinTermArgumentMachineError
       -- ^ A builtin received a term argument when something else was expected
     | NonConstrScrutinized
@@ -65,13 +65,31 @@ data MachineError fun
     deriving stock (Show, Eq, Functor, Generic)
     deriving anyclass (NFData)
 
--- | The type of errors (all of them) which can occur during evaluation
--- (some are used-caused, some are internal).
-data EvaluationError user internal
-    = InternalEvaluationError !internal
-      -- ^ Indicates bugs.
-    | UserEvaluationError !user
-      -- ^ Indicates user errors.
+{- | The type of errors that can occur during evaluation. There are two kinds of errors:
+
+1. Operational ones -- these are errors that are indicative of the _logic_ of the program being
+   wrong. For example, 'Error' was executed, 'tailList' was applied to an empty list or evaluation
+   ran out of gas.
+2. Structural ones -- these are errors that are indicative of the _structure_ of the program being
+   wrong. For example, a free variable was encountered during evaluation, or a non-function was
+   applied to an argument.
+
+On the chain both of these are just regular failures and we don't distinguish between them there:
+if a script fails, it fails, it doesn't matter what the reason was. However in the tests it does
+matter why the failure occurred: a structural error may indicate that the test was written
+incorrectly while an operational error may be entirely expected.
+
+In other words, operational errors are regular runtime errors and structural errors are \"runtime
+type errors\". Which means that evaluating an (erased) well-typed program should never produce a
+structural error, only an operational one. This creates a sort of \"runtime type system\" for UPLC
+and it would be great to stick to it and enforce in tests etc, but we currently don't. For example,
+a built-in function expecting a list but getting something else should throw a structural error,
+but currently it'll throw an operational one. This is something that we plan to improve upon in
+future.
+-}
+data EvaluationError operational structural
+    = OperationalEvaluationError !operational
+    | StructuralEvaluationError !structural
     deriving stock (Show, Eq, Functor, Generic)
     deriving anyclass (NFData)
 
@@ -80,47 +98,50 @@ mtraverse makeClassyPrisms
     , ''EvaluationError
     ]
 
-instance internal ~ MachineError fun => AsMachineError (EvaluationError user internal) fun where
-    _MachineError = _InternalEvaluationError
-instance AsUnliftingError internal => AsUnliftingError (EvaluationError user internal) where
-    _UnliftingError = _InternalEvaluationError . _UnliftingError
+instance structural ~ MachineError fun =>
+        AsMachineError (EvaluationError operational structural) fun where
+    _MachineError = _StructuralEvaluationError
+instance AsUnliftingError structural =>
+        AsUnliftingError (EvaluationError operational structural) where
+    _UnliftingError = _StructuralEvaluationError . _UnliftingError
 instance AsUnliftingError (MachineError fun) where
     _UnliftingError = _UnliftingMachineError
-instance AsEvaluationFailure user => AsEvaluationFailure (EvaluationError user internal) where
-    _EvaluationFailure = _UserEvaluationError . _EvaluationFailure
-
-type EvaluationException user internal =
-    ErrorWithCause (EvaluationError user internal)
-
-{- Note [Ignoring context in UserEvaluationError]
-The UserEvaluationError error has a term argument, but
-extractEvaluationResult just discards this and returns
-EvaluationFailure.  This means that, for example, if we use the `plc`
-command to execute a program containing a division by zero, plc exits
-silently without reporting that anything has gone wrong (but returning
-a non-zero exit code to the shell via `exitFailure`).  This is because
-UserEvaluationError is used in cases when a PLC program itself goes
-wrong (for example, a failure due to `(error)`, a failure during
-builtin evaluation, or exceeding the gas limit).  This is used to
-signal unsuccessful in validation and so is not regarded as a real
-error; in contrast, machine errors, typechecking failures,
-and so on are genuine errors and we report their context if available.
- -}
-
--- | Turn any 'UserEvaluationError' into an 'EvaluationFailure'.
+instance AsEvaluationFailure operational =>
+        AsEvaluationFailure (EvaluationError operational structural) where
+    _EvaluationFailure = _OperationalEvaluationError . _EvaluationFailure
+
+type EvaluationException operational structural =
+    ErrorWithCause (EvaluationError operational structural)
+
+{- Note [Ignoring context in OperationalEvaluationError]
+The 'OperationalEvaluationError' error has a term argument, but 'extractEvaluationResult' just
+discards this and returns 'EvaluationFailure'. This means that, for example, if we use the @plc@
+command to execute a program containing a division by zero, @plc@ exits silently without reporting
+that anything has gone wrong (but returning a non-zero exit code to the shell via 'exitFailure').
+This is because 'OperationalEvaluationError' is used in cases when a PLC program itself goes wrong
+(see the Haddocks of 'EvaluationError'). This is used to signal unsuccessful validation and so is
+not regarded as a real error; in contrast structural errors are genuine errors and we report their
+context if available.
+-}
+
+-- See Note [Ignoring context in OperationalEvaluationError].
+-- | Preserve the contents of an 'StructuralEvaluationError' as a 'Left' and turn an
+-- 'OperationalEvaluationError' into a @Right EvaluationFailure@.
 extractEvaluationResult
-    :: Either (EvaluationException user internal term) a
-    -> Either (ErrorWithCause internal term) (EvaluationResult a)
+    :: Either (EvaluationException operational structural term) a
+    -> Either (ErrorWithCause structural term) (EvaluationResult a)
 extractEvaluationResult (Right term) = Right $ EvaluationSuccess term
 extractEvaluationResult (Left (ErrorWithCause evalErr cause)) = case evalErr of
-    InternalEvaluationError err -> Left  $ ErrorWithCause err cause
-    UserEvaluationError _       -> Right $ EvaluationFailure
+    StructuralEvaluationError err -> Left  $ ErrorWithCause err cause
+    OperationalEvaluationError _  -> Right $ EvaluationFailure
 
-unsafeExtractEvaluationResult
+-- | Throw on a 'StructuralEvaluationError' and turn an 'OperationalEvaluationError' into an
+-- 'EvaluationFailure'.
+unsafeToEvaluationResult
     :: (PrettyPlc internal, PrettyPlc term, Typeable internal, Typeable term)
     => Either (EvaluationException user internal term) a
     -> EvaluationResult a
-unsafeExtractEvaluationResult = unsafeFromEither . extractEvaluationResult
+unsafeToEvaluationResult = unsafeFromEither . extractEvaluationResult
 
 instance (HasPrettyDefaults config ~ 'True, Pretty fun) =>
             PrettyBy config (MachineError fun) where
@@ -145,13 +166,7 @@ instance (HasPrettyDefaults config ~ 'True, Pretty fun) =>
 
 instance
         ( HasPrettyDefaults config ~ 'True
-        , PrettyBy config internal, Pretty user
-        ) => PrettyBy config (EvaluationError user internal) where
-    prettyBy config (InternalEvaluationError err) = fold
-        [ "error:", hardline
-        , prettyBy config err
-        ]
-    prettyBy _      (UserEvaluationError err) = fold
-        [ "User error:", hardline
-        , pretty err
-        ]
+        , Pretty operational, PrettyBy config structural
+        ) => PrettyBy config (EvaluationError operational structural) where
+    prettyBy _      (OperationalEvaluationError operational) = pretty operational
+    prettyBy config (StructuralEvaluationError structural)   = prettyBy config structural
diff --git a/plutus-core/plutus-core/src/PlutusCore/TypeCheck.hs b/plutus-core/plutus-core/src/PlutusCore/TypeCheck.hs
index b71f193d2db..995f944c372 100644
--- a/plutus-core/plutus-core/src/PlutusCore/TypeCheck.hs
+++ b/plutus-core/plutus-core/src/PlutusCore/TypeCheck.hs
@@ -36,9 +36,9 @@ import PlutusCore.Quote
 import PlutusCore.Rename
 import PlutusCore.TypeCheck.Internal
 
--- | The constraint for built-in types/functions are kind/type-checkable.
+-- | The constraint for built-in types\/functions are kind\/type-checkable.
 --
--- We keep this separate from 'MonadKindCheck'/'MonadTypeCheck', because those mainly constrain the
+-- We keep this separate from 'MonadKindCheck'\/'MonadTypeCheck', because those mainly constrain the
 -- monad and 'Typecheckable' constraints only the builtins. In particular useful when the monad gets
 -- instantiated and builtins don't. Another reason is that 'Typecheckable' is not required during
 -- type checking, since it's only needed for computing 'BuiltinTypes', which is passed as a regular
diff --git a/plutus-core/plutus-core/test/Evaluation/Machines.hs b/plutus-core/plutus-core/test/Evaluation/Machines.hs
index 0d662124ce3..e47c3aceeee 100644
--- a/plutus-core/plutus-core/test/Evaluation/Machines.hs
+++ b/plutus-core/plutus-core/test/Evaluation/Machines.hs
@@ -20,10 +20,12 @@ import Test.Tasty
 import Test.Tasty.Hedgehog
 
 testMachine
-    :: (uni ~ DefaultUni, fun ~ DefaultFun, PrettyPlc internal)
+    :: (uni ~ DefaultUni, fun ~ DefaultFun, PrettyPlc structural)
     => String
     -> (Term TyName Name uni fun () ->
-           Either (EvaluationException user internal (Term TyName Name uni fun ())) (Term TyName Name uni fun ()))
+           Either
+               (EvaluationException operational structural (Term TyName Name uni fun ()))
+               (Term TyName Name uni fun ()))
     -> TestTree
 testMachine machine eval =
     testGroup machine $ fromInterestingTermGens $ \name ->
diff --git a/plutus-core/plutus-ir/test/PlutusIR/Compiler/Recursion/errorBinding.golden b/plutus-core/plutus-ir/test/PlutusIR/Compiler/Recursion/errorBinding.golden
index 26a2b45bb82..4efbe91da20 100644
--- a/plutus-core/plutus-ir/test/PlutusIR/Compiler/Recursion/errorBinding.golden
+++ b/plutus-core/plutus-ir/test/PlutusIR/Compiler/Recursion/errorBinding.golden
@@ -1,4 +1,4 @@
-An error has occurred:  User error:
+An error has occurred:
 The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.
 Final budget: ({cpu: 100
 | mem: 100})
diff --git a/plutus-core/plutus-ir/test/PlutusIR/Transform/StrictLetRec/Tests/Lib.hs b/plutus-core/plutus-ir/test/PlutusIR/Transform/StrictLetRec/Tests/Lib.hs
index f07c3210a2c..3421d896f9e 100644
--- a/plutus-core/plutus-ir/test/PlutusIR/Transform/StrictLetRec/Tests/Lib.hs
+++ b/plutus-core/plutus-ir/test/PlutusIR/Transform/StrictLetRec/Tests/Lib.hs
@@ -29,8 +29,8 @@ import PlutusIR.Compiler qualified as PIR
 import PlutusIR.Core qualified as PIR
 import PlutusIR.Parser (pTerm)
 import UntypedPlutusCore.Core qualified as UPLC
-import UntypedPlutusCore.Evaluation.Machine.Cek (CekValue, EvaluationResult (..), logEmitter,
-                                                 unsafeEvaluateCek)
+import UntypedPlutusCore.Evaluation.Machine.Cek (CekValue, EvaluationResult (..), evaluateCek,
+                                                 logEmitter, unsafeToEvaluationResult)
 import UntypedPlutusCore.Evaluation.Machine.Cek.CekMachineCosts (CekMachineCosts)
 
 pirTermFromFile
@@ -66,7 +66,7 @@ compilePirProgramOrFail pirProgram = do
     & runExceptT
     >>= \case
       Left (er :: PIR.Error DefaultUni DefaultFun (Provenance ())) -> fail $ show er
-      Right p -> pure (void p)
+      Right p                                                      -> pure (void p)
 
 compileTplcProgramOrFail
   :: (MonadFail m)
@@ -83,7 +83,8 @@ evaluateUplcProgramWithTraces
   :: UPLC.Program Name DefaultUni DefaultFun ()
   -> (EvaluationResult (UPLC.Term Name DefaultUni DefaultFun ()), [Text])
 evaluateUplcProgramWithTraces uplcProg =
-  unsafeEvaluateCek logEmitter machineParameters (uplcProg ^. UPLC.progTerm)
+  first unsafeToEvaluationResult $
+    evaluateCek logEmitter machineParameters (uplcProg ^. UPLC.progTerm)
  where
   costModel :: CostModel CekMachineCosts BuiltinCostModel =
     CostModel defaultCekMachineCosts defaultBuiltinCostModel
@@ -102,5 +103,5 @@ defaultCompilationCtx = do
 handlePirErrorByFailing
   :: (Pretty ann, MonadFail m) => Either (PIR.Error DefaultUni DefaultFun ann) a -> m a
 handlePirErrorByFailing = \case
-  Left e -> fail $ show e
+  Left e  -> fail $ show e
   Right x -> pure x
diff --git a/plutus-core/testlib/PlutusCore/Generators/Hedgehog/Test.hs b/plutus-core/testlib/PlutusCore/Generators/Hedgehog/Test.hs
index 3c6921b1780..ab045c191d2 100644
--- a/plutus-core/testlib/PlutusCore/Generators/Hedgehog/Test.hs
+++ b/plutus-core/testlib/PlutusCore/Generators/Hedgehog/Test.hs
@@ -95,11 +95,11 @@ sampleProgramValueGolden folder name genTerm = do
 propEvaluate
     :: ( uni ~ DefaultUni, fun ~ DefaultFun
        , KnownTypeAst TyName uni a, MakeKnown (Term TyName Name uni fun ()) a
-       , PrettyPlc internal
+       , PrettyPlc structural
        )
     => (Term TyName Name uni fun () ->
            Either
-            (EvaluationException user internal (Term TyName Name uni fun ()))
+            (EvaluationException operational structural (Term TyName Name uni fun ()))
             (Term TyName Name uni fun ()))
        -- ^ An evaluator.
     -> TermGen a  -- ^ A term/value generator.
diff --git a/plutus-core/testlib/PlutusCore/Generators/Hedgehog/TypeEvalCheck.hs b/plutus-core/testlib/PlutusCore/Generators/Hedgehog/TypeEvalCheck.hs
index 45d585448d6..c005bd7a963 100644
--- a/plutus-core/testlib/PlutusCore/Generators/Hedgehog/TypeEvalCheck.hs
+++ b/plutus-core/testlib/PlutusCore/Generators/Hedgehog/TypeEvalCheck.hs
@@ -94,11 +94,11 @@ type TypeEvalCheckM uni fun = Either (TypeEvalCheckError uni fun)
 typeEvalCheckBy
     :: ( uni ~ DefaultUni, fun ~ DefaultFun
        , KnownTypeAst TyName uni a, MakeKnown (Term TyName Name uni fun ()) a
-       , PrettyPlc internal
+       , PrettyPlc structural
        )
     => (Term TyName Name uni fun () ->
            Either
-               (EvaluationException user internal (Term TyName Name uni fun ()))
+               (EvaluationException operational structural (Term TyName Name uni fun ()))
                (Term TyName Name uni fun ()))
        -- ^ An evaluator.
     -> TermOf (Term TyName Name uni fun ()) a
diff --git a/plutus-core/testlib/PlutusCore/Generators/NEAT/Spec.hs b/plutus-core/testlib/PlutusCore/Generators/NEAT/Spec.hs
index e3fc6fb1e6a..a66684842c3 100644
--- a/plutus-core/testlib/PlutusCore/Generators/NEAT/Spec.hs
+++ b/plutus-core/testlib/PlutusCore/Generators/NEAT/Spec.hs
@@ -111,21 +111,21 @@ not exploited.
 
 -- handle a user error and turn it back into an error term
 handleError :: Type TyName DefaultUni ()
-       -> U.ErrorWithCause (U.EvaluationError user internal) term
-       -> Either (U.ErrorWithCause (U.EvaluationError user internal) term)
+       -> U.ErrorWithCause (U.EvaluationError operational structural) term
+       -> Either (U.ErrorWithCause (U.EvaluationError operational structural) term)
                  (Term TyName Name DefaultUni DefaultFun ())
 handleError ty e = case U._ewcError e of
-  U.UserEvaluationError     _ -> return (Error () ty)
-  U.InternalEvaluationError _ -> throwError e
+  U.OperationalEvaluationError _ -> return (Error () ty)
+  U.StructuralEvaluationError _  -> throwError e
 
 -- untyped version of `handleError`
 handleUError ::
-          U.ErrorWithCause (U.EvaluationError user internal) term
-       -> Either (U.ErrorWithCause (U.EvaluationError user internal) term)
+          U.ErrorWithCause (U.EvaluationError operational structural) term
+       -> Either (U.ErrorWithCause (U.EvaluationError operational structural) term)
                  (U.Term Name DefaultUni DefaultFun ())
 handleUError e = case U._ewcError e of
-  U.UserEvaluationError     _ -> return (U.Error ())
-  U.InternalEvaluationError _ -> throwError e
+  U.OperationalEvaluationError _ -> return (U.Error ())
+  U.StructuralEvaluationError _  -> throwError e
 
 -- |Property: check if the type is preserved by evaluation.
 --
diff --git a/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek.hs b/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek.hs
index ee43e07dc11..8593d87c31e 100644
--- a/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek.hs
+++ b/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek.hs
@@ -7,14 +7,11 @@ module UntypedPlutusCore.Evaluation.Machine.Cek
     runCek
     , runCekDeBruijn
     , runCekNoEmit
-    , unsafeRunCekNoEmit
     , evaluateCek
     , evaluateCekNoEmit
-    , unsafeEvaluateCek
-    , unsafeEvaluateCekNoEmit
     , EvaluationResult(..)
     , extractEvaluationResult
-    , unsafeExtractEvaluationResult
+    , unsafeToEvaluationResult
     -- * Errors
     , CekUserError(..)
     , ErrorWithCause(..)
@@ -59,7 +56,6 @@ import UntypedPlutusCore.Evaluation.Machine.Cek.Internal
 import UntypedPlutusCore.Evaluation.Machine.CommonAPI qualified as Common
 
 import PlutusCore.Builtin
-import PlutusCore.Evaluation.Machine.Exception
 import PlutusCore.Evaluation.Machine.MachineParameters
 import PlutusCore.Name.Unique
 
@@ -88,18 +84,6 @@ runCekNoEmit
     -> (Either (CekEvaluationException Name uni fun) (Term Name uni fun ()), cost)
 runCekNoEmit = Common.runCekNoEmit runCekDeBruijn
 
-{-| Unsafely evaluate a term using the CEK machine with logging disabled and keep track of costing.
-May throw a 'CekMachineException'.
-*THIS FUNCTION IS PARTIAL if the input term contains free variables*
--}
-unsafeRunCekNoEmit
-    :: ThrowableBuiltins uni fun
-    => MachineParameters CekMachineCosts fun (CekValue uni fun ann)
-    -> ExBudgetMode cost uni fun
-    -> Term Name uni fun ann
-    -> (EvaluationResult (Term Name uni fun ()), cost)
-unsafeRunCekNoEmit = Common.unsafeRunCekNoEmit runCekDeBruijn
-
 -- | Evaluate a term using the CEK machine with logging enabled.
 -- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
 evaluateCek
@@ -119,25 +103,6 @@ evaluateCekNoEmit
     -> Either (CekEvaluationException Name uni fun) (Term Name uni fun ())
 evaluateCekNoEmit = Common.evaluateCekNoEmit runCekDeBruijn
 
--- | Evaluate a term using the CEK machine with logging enabled. May throw a 'CekMachineException'.
--- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
-unsafeEvaluateCek
-    :: ThrowableBuiltins uni fun
-    => EmitterMode uni fun
-    -> MachineParameters CekMachineCosts fun (CekValue uni fun ann)
-    -> Term Name uni fun ann
-    -> (EvaluationResult (Term Name uni fun ()), [Text])
-unsafeEvaluateCek = Common.unsafeEvaluateCek runCekDeBruijn
-
--- | Evaluate a term using the CEK machine with logging disabled. May throw a 'CekMachineException'.
--- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
-unsafeEvaluateCekNoEmit
-    :: ThrowableBuiltins uni fun
-    => MachineParameters CekMachineCosts fun (CekValue uni fun ann)
-    -> Term Name uni fun ann
-    -> EvaluationResult (Term Name uni fun ())
-unsafeEvaluateCekNoEmit = Common.unsafeEvaluateCekNoEmit runCekDeBruijn
-
 -- | Unlift a value using the CEK machine.
 -- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
 readKnownCek
diff --git a/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek/ExBudgetMode.hs b/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek/ExBudgetMode.hs
index 0d376a47b02..a2f15197f96 100644
--- a/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek/ExBudgetMode.hs
+++ b/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek/ExBudgetMode.hs
@@ -144,7 +144,7 @@ restricting (ExRestrictingBudget initB@(ExBudget cpuInit memInit)) = ExBudgetMod
             when (cpuLeft' < 0 || memLeft' < 0) $ do
                 let budgetLeft = ExBudget cpuLeft' memLeft'
                 throwingWithCause _EvaluationError
-                    (UserEvaluationError . CekOutOfExError $ ExRestrictingBudget budgetLeft)
+                    (OperationalEvaluationError . CekOutOfExError $ ExRestrictingBudget budgetLeft)
                     Nothing
         spender = CekBudgetSpender spend
         remaining = ExBudget <$> readCpu <*> readMem
diff --git a/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek/Internal.hs b/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek/Internal.hs
index fc755a41f2c..113abb8699a 100644
--- a/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek/Internal.hs
+++ b/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek/Internal.hs
@@ -48,6 +48,7 @@ module UntypedPlutusCore.Evaluation.Machine.Cek.Internal
     , StepKind(..)
     , ThrowableBuiltins
     , extractEvaluationResult
+    , unsafeToEvaluationResult
     , spendBudgetStreamCek
     , runCekDeBruijn
     , dischargeCekValue
diff --git a/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/CommonAPI.hs b/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/CommonAPI.hs
index fa24c961b5c..a9c2bf023f8 100644
--- a/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/CommonAPI.hs
+++ b/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/CommonAPI.hs
@@ -11,14 +11,11 @@ module UntypedPlutusCore.Evaluation.Machine.CommonAPI
     runCek
     , runCekDeBruijn
     , runCekNoEmit
-    , unsafeRunCekNoEmit
     , evaluateCek
     , evaluateCekNoEmit
-    , unsafeEvaluateCek
-    , unsafeEvaluateCekNoEmit
     , EvaluationResult(..)
     , extractEvaluationResult
-    , unsafeExtractEvaluationResult
+    , unsafeToEvaluationResult
     -- * Errors
     , CekUserError(..)
     , ErrorWithCause(..)
@@ -63,7 +60,6 @@ import UntypedPlutusCore.Evaluation.Machine.Cek.ExBudgetMode
 import UntypedPlutusCore.Evaluation.Machine.Cek.Internal
 
 import PlutusCore.Builtin
-import PlutusCore.Evaluation.Machine.Exception
 import PlutusCore.Evaluation.Machine.MachineParameters
 import PlutusCore.Name.Unique
 import PlutusCore.Quote
@@ -137,21 +133,6 @@ runCekNoEmit runner params mode =
     -- throw away the logs
     (\(res, cost, _logs) -> (res, cost)) . runCek runner params mode noEmitter
 
-{-| Unsafely evaluate a term a machine with logging disabled and keep track of costing.
-May throw a 'CekMachineException'.
-*THIS FUNCTION IS PARTIAL if the input term contains free variables*
--}
-unsafeRunCekNoEmit
-    :: ThrowableBuiltins uni fun
-    => MachineRunner cost uni fun ann
-    -> MachineParameters CekMachineCosts fun (CekValue uni fun ann)
-    -> ExBudgetMode cost uni fun
-    -> Term Name uni fun ann
-    -> (EvaluationResult (Term Name uni fun ()), cost)
-unsafeRunCekNoEmit runner params mode =
-    -- Don't use 'first': https://github.com/IntersectMBO/plutus/issues/3876
-    (\(e, l) -> (unsafeExtractEvaluationResult e, l)) . runCekNoEmit runner params mode
-
 -- | Evaluate a term using a machine with logging enabled.
 -- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
 evaluateCek
@@ -175,29 +156,6 @@ evaluateCekNoEmit
     -> Either (CekEvaluationException Name uni fun) (Term Name uni fun ())
 evaluateCekNoEmit runner params = fst . runCekNoEmit runner params restrictingEnormous
 
--- | Evaluate a term using a machine with logging enabled. May throw a 'CekMachineException'.
--- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
-unsafeEvaluateCek
-    :: ThrowableBuiltins uni fun
-    => MachineRunner RestrictingSt uni fun ann
-    -> EmitterMode uni fun
-    -> MachineParameters CekMachineCosts fun (CekValue uni fun ann)
-    -> Term Name uni fun ann
-    -> (EvaluationResult (Term Name uni fun ()), [Text])
-unsafeEvaluateCek runner emitTime params =
-    -- Don't use 'first': https://github.com/IntersectMBO/plutus/issues/3876
-    (\(e, l) -> (unsafeExtractEvaluationResult e, l)) . evaluateCek runner emitTime params
-
--- | Evaluate a term using a machine with logging disabled. May throw a 'CekMachineException'.
--- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
-unsafeEvaluateCekNoEmit
-    :: ThrowableBuiltins uni fun
-    => MachineRunner RestrictingSt uni fun ann
-    -> MachineParameters CekMachineCosts fun (CekValue uni fun ann)
-    -> Term Name uni fun ann
-    -> EvaluationResult (Term Name uni fun ())
-unsafeEvaluateCekNoEmit runner params = unsafeExtractEvaluationResult . evaluateCekNoEmit runner params
-
 -- | Unlift a value using a machine.
 -- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
 readKnownCek
diff --git a/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/SteppableCek.hs b/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/SteppableCek.hs
index e81bf9ac973..9caacf82789 100644
--- a/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/SteppableCek.hs
+++ b/plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/SteppableCek.hs
@@ -7,14 +7,11 @@ module UntypedPlutusCore.Evaluation.Machine.SteppableCek
     runCek
     , runCekDeBruijn
     , runCekNoEmit
-    , unsafeRunCekNoEmit
     , evaluateCek
     , evaluateCekNoEmit
-    , unsafeEvaluateCek
-    , unsafeEvaluateCekNoEmit
     , EvaluationResult(..)
     , extractEvaluationResult
-    , unsafeExtractEvaluationResult
+    , unsafeToEvaluationResult
     -- * Errors
     , CekUserError(..)
     , ErrorWithCause(..)
@@ -57,7 +54,6 @@ import UntypedPlutusCore.Evaluation.Machine.CommonAPI qualified as Common
 import UntypedPlutusCore.Evaluation.Machine.SteppableCek.Internal as S
 
 import PlutusCore.Builtin
-import PlutusCore.Evaluation.Machine.Exception
 import PlutusCore.Evaluation.Machine.MachineParameters
 import PlutusCore.Name.Unique
 
@@ -87,19 +83,6 @@ runCekNoEmit
     -> (Either (CekEvaluationException Name uni fun) (Term Name uni fun ()), cost)
 runCekNoEmit = Common.runCekNoEmit S.runCekDeBruijn
 
-{-| Unsafely evaluate a term using the Steppable CEK machine with logging disabled
--- and keep track of costing.
-May throw a 'CekMachineException'.
-*THIS FUNCTION IS PARTIAL if the input term contains free variables*
--}
-unsafeRunCekNoEmit
-    :: ThrowableBuiltins uni fun
-    => MachineParameters CekMachineCosts fun (CekValue uni fun ann)
-    -> ExBudgetMode cost uni fun
-    -> Term Name uni fun ann
-    -> (EvaluationResult (Term Name uni fun ()), cost)
-unsafeRunCekNoEmit = Common.unsafeRunCekNoEmit S.runCekDeBruijn
-
 -- | Evaluate a term using the Steppable CEK machine with logging enabled.
 -- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
 evaluateCek
@@ -119,27 +102,6 @@ evaluateCekNoEmit
     -> Either (CekEvaluationException Name uni fun) (Term Name uni fun ())
 evaluateCekNoEmit = Common.evaluateCekNoEmit S.runCekDeBruijn
 
--- | Evaluate a term using the Steppable CEK machine with logging enabled.
--- May throw a 'CekMachineException'.
--- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
-unsafeEvaluateCek
-    :: ThrowableBuiltins uni fun
-    => EmitterMode uni fun
-    -> MachineParameters CekMachineCosts fun (CekValue uni fun ann)
-    -> Term Name uni fun ann
-    -> (EvaluationResult (Term Name uni fun ()), [Text])
-unsafeEvaluateCek = Common.unsafeEvaluateCek S.runCekDeBruijn
-
--- | Evaluate a term using the Steppable CEK machine with logging disabled.
--- May throw a 'CekMachineException'.
--- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
-unsafeEvaluateCekNoEmit
-    :: ThrowableBuiltins uni fun
-    => MachineParameters CekMachineCosts fun (CekValue uni fun ann)
-    -> Term Name uni fun ann
-    -> EvaluationResult (Term Name uni fun ())
-unsafeEvaluateCekNoEmit = Common.unsafeEvaluateCekNoEmit S.runCekDeBruijn
-
 -- | Unlift a value using the Steppable CEK machine.
 -- *THIS FUNCTION IS PARTIAL if the input term contains free variables*
 readKnownCek
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Builtins/Common.hs b/plutus-core/untyped-plutus-core/test/Evaluation/Builtins/Common.hs
index 285059ed8f2..46700d430ac 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Builtins/Common.hs
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Builtins/Common.hs
@@ -3,8 +3,9 @@
 {-# LANGUAGE TypeOperators    #-}
 
 module Evaluation.Builtins.Common
-    ( unsafeEvaluateCek
-    , unsafeEvaluateCekNoEmit
+    ( unsafeToEvaluationResult
+    , evaluateCek
+    , evaluateCekNoEmit
     , readKnownCek
     , typecheckAnd
     , typecheckEvaluateCek
@@ -27,6 +28,7 @@ import UntypedPlutusCore qualified as UPLC
 import UntypedPlutusCore.Evaluation.Machine.Cek
 
 import Control.Monad.Except
+import Data.Bifunctor
 import Data.Text (Text)
 
 -- | Type check and evaluate a term.
@@ -39,14 +41,12 @@ typecheckAnd
             UPLC.Term Name uni fun () -> a)
     -> CostingPart uni fun -> TPLC.Term TyName Name uni fun () -> m a
 typecheckAnd semvar action costingPart term = TPLC.runQuoteT $ do
-    -- Here we don't use `getDefTypeCheckConfig`, to cover the absurd case where
-    -- builtins can change their type according to their BuiltinSemanticsVariant
+    -- Here we don't use 'getDefTypeCheckConfig', to cover the absurd case where
+    -- builtins can change their type according to their 'BuiltinSemanticsVariant'.
     tcConfig <- TypeCheckConfig defKindCheckConfig <$> builtinMeaningsToTypes semvar ()
     _ <- TPLC.inferType tcConfig term
+    let runtime = mkMachineParameters semvar $ CostModel defaultCekMachineCosts costingPart
     return . action runtime $ TPLC.eraseTerm term
-    where
-      runtime = mkMachineParameters semvar $
-                   CostModel defaultCekMachineCosts costingPart
 
 -- | Type check and evaluate a term, logging enabled.
 typecheckEvaluateCek
@@ -57,7 +57,9 @@ typecheckEvaluateCek
     -> CostingPart uni fun
     -> TPLC.Term TyName Name uni fun ()
     -> m (EvaluationResult (UPLC.Term Name uni fun ()), [Text])
-typecheckEvaluateCek semvar = typecheckAnd semvar $ unsafeEvaluateCek logEmitter
+typecheckEvaluateCek semvar =
+    typecheckAnd semvar $ \params ->
+        first unsafeToEvaluationResult . evaluateCek logEmitter params
 
 -- | Type check and evaluate a term, logging disabled.
 typecheckEvaluateCekNoEmit
@@ -68,7 +70,9 @@ typecheckEvaluateCekNoEmit
     -> CostingPart uni fun
     -> TPLC.Term TyName Name uni fun ()
     -> m (EvaluationResult (UPLC.Term Name uni fun ()))
-typecheckEvaluateCekNoEmit semvar = typecheckAnd semvar unsafeEvaluateCekNoEmit
+typecheckEvaluateCekNoEmit semvar =
+    typecheckAnd semvar $ \params ->
+        unsafeToEvaluationResult . evaluateCekNoEmit params
 
 -- | Type check and convert a Plutus Core term to a Haskell value.
 typecheckReadKnownCek
@@ -80,4 +84,5 @@ typecheckReadKnownCek
     -> CostingPart uni fun
     -> TPLC.Term TyName Name uni fun ()
     -> m (Either (CekEvaluationException Name uni fun) a)
-typecheckReadKnownCek semvar = typecheckAnd semvar readKnownCek
+typecheckReadKnownCek semvar =
+    typecheckAnd semvar readKnownCek
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Builtins/Definition.hs b/plutus-core/untyped-plutus-core/test/Evaluation/Builtins/Definition.hs
index c7d6eb915e8..25ccd044ea2 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Builtins/Definition.hs
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Builtins/Definition.hs
@@ -89,8 +89,10 @@ test_Const =
             tB = mkConstant () b
             text = toTypeAst @_ @_ @DefaultUni @Text Proxy
             runConst con = mkIterAppNoAnn (mkIterInstNoAnn con [text, bool]) [tC, tB]
-            lhs = typecheckReadKnownCek def defaultBuiltinCostModelExt $ runConst $ builtin () (Right Const)
-            rhs = typecheckReadKnownCek def defaultBuiltinCostModelExt $ runConst $ mapFun @DefaultFun Left Plc.const
+            lhs = typecheckReadKnownCek def defaultBuiltinCostModelExt $
+                    runConst $ builtin () (Right Const)
+            rhs = typecheckReadKnownCek def defaultBuiltinCostModelExt $
+                    runConst $ mapFun @DefaultFun Left Plc.const
         lhs === Right (Right c)
         lhs === rhs
 
@@ -125,7 +127,8 @@ test_Id =
                                   . LamAbs () i integer
                                   . LamAbs () j integer
                                   $ Var () i
-        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?= Right (EvaluationSuccess oneU)
+        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?=
+            Right (EvaluationSuccess oneU)
 
 -- | Test that a polymorphic built-in function can have a higher-kinded type variable in its
 -- signature.
@@ -140,7 +143,8 @@ test_IdFInteger =
                 = apply () (mapFun Left Scott.sum)
                 . apply () (tyInst () (builtin () $ Right IdFInteger) Scott.listTy)
                 $ mkIterAppNoAnn (mapFun Left Scott.enumFromTo) [one, ten]
-        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?= Right (EvaluationSuccess res)
+        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?=
+            Right (EvaluationSuccess res)
 
 test_IdList :: TestTree
 test_IdList =
@@ -158,7 +162,8 @@ test_IdList =
                 . apply () (tyInst () (builtin () $ Right IdList) integer)
                 $ mkIterAppNoAnn (mapFun Left Scott.enumFromTo) [one, ten]
         tyAct @?= tyExp
-        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?= Right (EvaluationSuccess res)
+        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?=
+            Right (EvaluationSuccess res)
 
 {- Note [Higher-rank built-in functions]
 We can't unlift a monomorphic function passed to a built-in function, let alone unlift a polymorphic
@@ -194,7 +199,8 @@ test_IdRank2 =
                 = apply () (mapFun Left Scott.sum)
                 . tyInst () (apply () (tyInst () (builtin () $ Right IdRank2) Scott.listTy) Scott.nil)
                 $ integer
-        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?= Right (EvaluationSuccess res)
+        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?=
+            Right (EvaluationSuccess res)
 
 -- | Test that a builtin can be applied to a non-constant term.
 test_ScottToMetaUnit :: TestTree
@@ -207,7 +213,8 @@ test_ScottToMetaUnit =
         let runtime = mkMachineParameters def $ CostModel defaultCekMachineCosts ()
         -- @scottToMetaUnit Scott.map@ is ill-typed, but still runs successfully, since the builtin
         -- doesn't look at the argument.
-        unsafeEvaluateCekNoEmit runtime (eraseTerm $ applyTerm Scott.map) @?= res
+        unsafeToEvaluationResult (evaluateCekNoEmit runtime (eraseTerm $ applyTerm Scott.map)) @?=
+            res
 
 -- | Test that an exception thrown in the builtin application code does not get caught in the CEK
 -- machine and blows in the caller face instead. Uses a one-argument built-in function.
@@ -218,8 +225,10 @@ test_FailingSucc =
                 apply () (builtin () $ Right FailingSucc) $
                     mkConstant @Integer @DefaultUni @DefaultFunExt () 0
         typeErrOrEvalExcOrRes :: Either _ (Either BuiltinErrorCall _) <-
-            -- Here we rely on 'typecheckAnd' lazily running the action after type checking the term.
-            traverse (try . evaluate) $ typecheckEvaluateCek def defaultBuiltinCostModelExt term
+            -- Here we rely on 'typecheckAnd' lazily running the action after type checking the
+            -- term.
+            traverse (try . evaluate) $
+                typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term
         typeErrOrEvalExcOrRes @?= Right (Left BuiltinErrorCall)
 
 -- | Test that evaluating a PLC builtin application that is expensive enough to exceed the budget
@@ -232,7 +241,8 @@ test_ExpensiveSucc =
                 apply () (builtin () $ Right ExpensiveSucc) $
                     mkConstant @Integer @DefaultUni @DefaultFunExt () 0
         typeErrOrEvalExcOrRes :: Either _ (Either BuiltinErrorCall _) <-
-            traverse (try . evaluate) $ typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term
+            traverse (try . evaluate) $
+                typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term
         typeErrOrEvalExcOrRes @?= Right (Right EvaluationFailure)
 
 -- | Test that an exception thrown in the builtin application code does not get caught in the CEK
@@ -246,8 +256,10 @@ test_FailingPlus =
                     , mkConstant @Integer @DefaultUni () 1
                     ]
         typeErrOrEvalExcOrRes :: Either _ (Either BuiltinErrorCall _) <-
-            -- Here we rely on 'typecheckAnd' lazily running the action after type checking the term.
-            traverse (try . evaluate) $ typecheckEvaluateCek def defaultBuiltinCostModelExt term
+            -- Here we rely on 'typecheckAnd' lazily running the action after type checking the
+            -- term.
+            traverse (try . evaluate) $
+                typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term
         typeErrOrEvalExcOrRes @?= Right (Left BuiltinErrorCall)
 
 -- | Test that evaluating a PLC builtin application that is expensive enough to exceed the budget
@@ -262,7 +274,8 @@ test_ExpensivePlus =
                     , mkConstant @Integer @DefaultUni () 1
                     ]
         typeErrOrEvalExcOrRes :: Either _ (Either BuiltinErrorCall _) <-
-            traverse (try . evaluate) $ typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term
+            traverse (try . evaluate) $
+                typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term
         typeErrOrEvalExcOrRes @?= Right (Right EvaluationFailure)
 
 -- | Test that @Null@, @Head@ and @Tail@ are enough to get pattern matching on built-in lists.
@@ -277,7 +290,8 @@ test_BuiltinList =
                     , mkConstant @Integer () 0
                     , mkConstant @[Integer] () xs
                     ]
-        typecheckEvaluateCekNoEmit def defaultBuiltinCostModel term @?= Right (EvaluationSuccess res)
+        typecheckEvaluateCekNoEmit def defaultBuiltinCostModel term @?=
+            Right (EvaluationSuccess res)
 
 -- | Test that right-folding a built-in list with built-in 'Cons' recreates that list.
 test_IdBuiltinList :: TestTree
@@ -287,12 +301,14 @@ test_IdBuiltinList =
             xsTerm = mkConstant @[Integer] () [1..10]
             listOfInteger = mkTyBuiltin @_ @[Integer] ()
             term
-                = mkIterAppNoAnn (mkIterInstNoAnn (mapFun Left Builtin.foldrList) [integer, listOfInteger])
+                = mkIterAppNoAnn
+                    (mkIterInstNoAnn (mapFun Left Builtin.foldrList) [integer, listOfInteger])
                     [ tyInst () (builtin () $ Left MkCons) integer
                     , mkConstant @[Integer] () []
                     , xsTerm
                     ]
-        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?= Right (EvaluationSuccess xsTerm)
+        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?=
+            Right (EvaluationSuccess xsTerm)
 
 test_BuiltinPair :: TestTree
 test_BuiltinPair =
@@ -343,7 +359,8 @@ test_SwapEls =
                     , mkConstant @Integer () 0
                     , mkConstant () xs
                     ]
-        typecheckEvaluateCekNoEmit def defaultBuiltinCostModel term @?= Right (EvaluationSuccess res)
+        typecheckEvaluateCekNoEmit def defaultBuiltinCostModel term @?=
+            Right (EvaluationSuccess res)
 
 -- | Test that right-folding a built-in 'Data' with the constructors of 'Data' recreates the
 -- original value.
@@ -361,7 +378,8 @@ test_IdBuiltinData =
                 , emb BData
                 , dTerm
                 ]
-        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?= Right (EvaluationSuccess dTerm)
+        typecheckEvaluateCekNoEmit def defaultBuiltinCostModelExt term @?=
+            Right (EvaluationSuccess dTerm)
 
 -- | For testing how an evaluator instantiated at a particular 'ExBudgetMode' handles the
 -- 'TrackCosts' builtin.
@@ -425,7 +443,7 @@ test_SerialiseDataImpossible =
             dataLoop = Apply () (Builtin () SerialiseData) $ mkConstant () loop where
                 loop = List [loop]
             budgetMode = restricting . ExRestrictingBudget $ ExBudget 10000000000 10000000
-            evalRestricting params = fst . unsafeRunCekNoEmit params budgetMode
+            evalRestricting params = unsafeToEvaluationResult . fst . runCekNoEmit params budgetMode
         typecheckAnd def evalRestricting defaultBuiltinCostModel dataLoop @?=
             Right EvaluationFailure
 
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Debug/ex3.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Debug/ex3.golden
index bd65974e19d..569eea1d5ad 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Debug/ex3.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Debug/ex3.golden
@@ -7,5 +7,5 @@ OldState: Computing NewState: Returning
 Driver is going to do a single step
 OldState: Returning NewState: Computing
 Driver is going to do a single step
-OldState: Computing NewState is Error: An error has occurred:  User error:
+OldState: Computing NewState is Error: An error has occurred:
 The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Debug/ex4.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Debug/ex4.golden
index 79a5ab7f1cf..a3e13d2a057 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Debug/ex4.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Debug/ex4.golden
@@ -1,5 +1,5 @@
 Driver is going to do a single step
 OldState: Starting NewState: Computing
 Driver is going to do a single step
-OldState: Computing NewState is Error: An error has occurred:  User error:
+OldState: Computing NewState is Error: An error has occurred:
 The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNoBranch.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNoBranch.plc.golden
index 1436661e809..e229d959ca8 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNoBranch.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNoBranch.plc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 Case expression missing the branch required by the scrutinee tag: 0
 Caused by: (constr 0 (con integer 1)))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNoBranch.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNoBranch.uplc.golden
index 1436661e809..e229d959ca8 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNoBranch.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNoBranch.uplc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 Case expression missing the branch required by the scrutinee tag: 0
 Caused by: (constr 0 (con integer 1)))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNonTag.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNonTag.plc.golden
index f48798f54d0..1bd7d1fbdda 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNonTag.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNonTag.plc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A non-constructor value was scrutinized in a case expression
 Caused by: (con integer 1))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNonTag.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNonTag.uplc.golden
index f48798f54d0..1bd7d1fbdda 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNonTag.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/caseNonTag.uplc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A non-constructor value was scrutinized in a case expression
 Caused by: (con integer 1))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/diFullyApplied.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/diFullyApplied.plc.golden
index f177b6623f1..7f60668f62e 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/diFullyApplied.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/diFullyApplied.plc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  User error:
+(Left An error has occurred:
 The provided Plutus code called 'error'.
 Caused by: [ [ (builtin divideInteger) (con integer 1) ] (con integer 0) ])
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/diFullyApplied.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/diFullyApplied.uplc.golden
index 6ef7aa04f30..6388d69ceea 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/diFullyApplied.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/diFullyApplied.uplc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  User error:
+(Left An error has occurred:
 The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.
 Caused by: [ [ (builtin divideInteger) (con integer 1) ] (con integer 0) ])
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerAtInteger.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerAtInteger.plc.golden
index d3afe69b18d..8c9074010e3 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerAtInteger.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerAtInteger.plc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin expected a term argument, but something else was received
 Caused by: (force (force (builtin ifThenElse))))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerAtInteger.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerAtInteger.uplc.golden
index d3afe69b18d..8c9074010e3 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerAtInteger.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerAtInteger.uplc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin expected a term argument, but something else was received
 Caused by: (force (force (builtin ifThenElse))))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerWrongCondTypeSat.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerWrongCondTypeSat.plc.golden
index 0baa2734b4e..9cb5f80b598 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerWrongCondTypeSat.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerWrongCondTypeSat.plc.golden
@@ -1,4 +1,4 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 Could not unlift a value:
 Type mismatch: expected: bool; actual: string
 Caused by: [
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerWrongCondTypeSat.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerWrongCondTypeSat.uplc.golden
index 0baa2734b4e..9cb5f80b598 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerWrongCondTypeSat.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteAtIntegerWrongCondTypeSat.uplc.golden
@@ -1,4 +1,4 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 Could not unlift a value:
 Type mismatch: expected: bool; actual: string
 Caused by: [
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteTypeTermType.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteTypeTermType.plc.golden
index 1aeab826898..5db27720294 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteTypeTermType.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteTypeTermType.plc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin expected a term argument, but something else was received
 Caused by: (force [ (force (builtin ifThenElse)) (con bool True) ]))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteTypeTermType.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteTypeTermType.uplc.golden
index 1aeab826898..5db27720294 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteTypeTermType.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteTypeTermType.uplc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin expected a term argument, but something else was received
 Caused by: (force [ (force (builtin ifThenElse)) (con bool True) ]))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedFullyApplied.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedFullyApplied.plc.golden
index 8672ef77c8e..984aefc089d 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedFullyApplied.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedFullyApplied.plc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin received a term argument when something else was expected
 Caused by: [ (builtin ifThenElse) (con bool True) ])
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedFullyApplied.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedFullyApplied.uplc.golden
index 8672ef77c8e..984aefc089d 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedFullyApplied.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedFullyApplied.uplc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin received a term argument when something else was expected
 Caused by: [ (builtin ifThenElse) (con bool True) ])
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedWithCond.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedWithCond.plc.golden
index 8672ef77c8e..984aefc089d 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedWithCond.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedWithCond.plc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin received a term argument when something else was expected
 Caused by: [ (builtin ifThenElse) (con bool True) ])
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedWithCond.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedWithCond.uplc.golden
index 8672ef77c8e..984aefc089d 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedWithCond.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/iteUninstantiatedWithCond.uplc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin received a term argument when something else was expected
 Caused by: [ (builtin ifThenElse) (con bool True) ])
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError1.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError1.plc.golden
index cbb14ee9289..c9322a9f0b0 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError1.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError1.plc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin expected a term argument, but something else was received
 Caused by: (force (builtin multiplyInteger)))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError1.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError1.uplc.golden
index cbb14ee9289..c9322a9f0b0 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError1.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError1.uplc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin expected a term argument, but something else was received
 Caused by: (force (builtin multiplyInteger)))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError2.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError2.plc.golden
index 5591ce3bdb2..e68a5566eed 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError2.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError2.plc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin expected a term argument, but something else was received
 Caused by: (force [ (builtin multiplyInteger) (con integer 11) ]))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError2.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError2.uplc.golden
index 5591ce3bdb2..e68a5566eed 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError2.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError2.uplc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 A builtin expected a term argument, but something else was received
 Caused by: (force [ (builtin multiplyInteger) (con integer 11) ]))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError3.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError3.plc.golden
index 2f90b39bb7f..bec5ef97c9d 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError3.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError3.plc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 Attempted to instantiate a non-polymorphic term.
 Caused by: (con integer 242))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError3.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError3.uplc.golden
index 2f90b39bb7f..bec5ef97c9d 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError3.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/mulInstError3.uplc.golden
@@ -1,3 +1,3 @@
-(Left An error has occurred:  error:
+(Left An error has occurred:
 Attempted to instantiate a non-polymorphic term.
 Caused by: (con integer 242))
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/polyErrorInst.plc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/polyErrorInst.plc.golden
index d9c90ef72de..faaf84c1554 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/polyErrorInst.plc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/polyErrorInst.plc.golden
@@ -1,2 +1,2 @@
-(Left An error has occurred:  User error:
+(Left An error has occurred:
 The provided Plutus code called 'error'.)
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/polyErrorInst.uplc.golden b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/polyErrorInst.uplc.golden
index fccaddb46c4..cc268b310d6 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Golden/polyErrorInst.uplc.golden
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Golden/polyErrorInst.uplc.golden
@@ -1,2 +1,2 @@
-(Left An error has occurred:  User error:
+(Left An error has occurred:
 The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.)
\ No newline at end of file
diff --git a/plutus-core/untyped-plutus-core/test/Evaluation/Machines.hs b/plutus-core/untyped-plutus-core/test/Evaluation/Machines.hs
index f2d25e512bc..750c104f777 100644
--- a/plutus-core/untyped-plutus-core/test/Evaluation/Machines.hs
+++ b/plutus-core/untyped-plutus-core/test/Evaluation/Machines.hs
@@ -5,7 +5,6 @@
 
 module Evaluation.Machines
     ( test_machines
-    --, test_memory
     , test_budget
     , test_tallying
     ) where
@@ -41,16 +40,20 @@ import Test.Tasty.Golden
 import Test.Tasty.Hedgehog
 
 testMachine
-    :: (uni ~ DefaultUni, fun ~ DefaultFun, PrettyPlc internal)
+    :: (uni ~ DefaultUni, fun ~ DefaultFun, PrettyPlc structural)
     => String
     -> (Term Name uni fun () ->
-           Either (EvaluationException user internal (Term Name uni fun ())) (Term Name uni fun ()))
+           Either
+               (EvaluationException operational structural (Term Name uni fun ()))
+               (Term Name uni fun ()))
     -> TestTree
 testMachine machine eval =
     testGroup machine $ fromInterestingTermGens $ \name genTermOfTbv ->
         testPropertyNamed name (fromString name) . withTests 200 . property $ do
             TermOf term val <- forAllWith mempty genTermOfTbv
-            let resExp = eraseTerm <$> makeKnownOrFail @_ @(Plc.Term TyName Name DefaultUni DefaultFun ()) val
+            let resExp =
+                    eraseTerm <$>
+                        makeKnownOrFail @_ @(Plc.Term TyName Name DefaultUni DefaultFun ()) val
             case extractEvaluationResult . eval $ eraseTerm term of
                 Left err     -> fail $ show err
                 Right resAct -> resAct === resExp
diff --git a/plutus-core/untyped-plutus-core/test/Transform/CaseOfCase/Test.hs b/plutus-core/untyped-plutus-core/test/Transform/CaseOfCase/Test.hs
index 21ba8f2f45b..30862d0f4d6 100644
--- a/plutus-core/untyped-plutus-core/test/Transform/CaseOfCase/Test.hs
+++ b/plutus-core/untyped-plutus-core/test/Transform/CaseOfCase/Test.hs
@@ -23,7 +23,7 @@ import Test.Tasty.HUnit (testCase, (@?=))
 import UntypedPlutusCore (DefaultFun, DefaultUni, Name, Term (..))
 import UntypedPlutusCore.Core qualified as UPLC
 import UntypedPlutusCore.Evaluation.Machine.Cek (CekMachineCosts, CekValue, EvaluationResult (..),
-                                                 noEmitter, unsafeEvaluateCek)
+                                                 evaluateCek, noEmitter, unsafeToEvaluationResult)
 import UntypedPlutusCore.Transform.CaseOfCase (caseOfCase)
 
 test_caseOfCase :: TestTree
@@ -119,7 +119,7 @@ testCaseOfCaseWithError =
 evaluateUplc
   :: UPLC.Term Name DefaultUni DefaultFun ()
   -> EvaluationResult (UPLC.Term Name DefaultUni DefaultFun ())
-evaluateUplc = fst <$> unsafeEvaluateCek noEmitter machineParameters
+evaluateUplc = unsafeToEvaluationResult . fst <$> evaluateCek noEmitter machineParameters
  where
   costModel :: CostModel CekMachineCosts BuiltinCostModel =
     CostModel defaultCekMachineCosts defaultBuiltinCostModel
diff --git a/plutus-tx-plugin/test/Plugin/Basic/9.6/ifOptEval.eval.golden b/plutus-tx-plugin/test/Plugin/Basic/9.6/ifOptEval.eval.golden
index 64d9a1489c9..5104d4035fc 100644
--- a/plutus-tx-plugin/test/Plugin/Basic/9.6/ifOptEval.eval.golden
+++ b/plutus-tx-plugin/test/Plugin/Basic/9.6/ifOptEval.eval.golden
@@ -1,4 +1,4 @@
-An error has occurred:  User error:
+An error has occurred:
 The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.
 Caused by: (divideInteger 1 0)
 Final budget: ({cpu: 453560
diff --git a/plutus-tx-plugin/test/Strictness/9.6/lambda-default.eval.golden b/plutus-tx-plugin/test/Strictness/9.6/lambda-default.eval.golden
index 1d4b8b27224..f2c04fe10eb 100644
--- a/plutus-tx-plugin/test/Strictness/9.6/lambda-default.eval.golden
+++ b/plutus-tx-plugin/test/Strictness/9.6/lambda-default.eval.golden
@@ -1,2 +1,2 @@
-An error has occurred:  User error:
+An error has occurred:
 The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.
\ No newline at end of file
diff --git a/plutus-tx-plugin/test/Strictness/9.6/lambda-nonstrict.eval.golden b/plutus-tx-plugin/test/Strictness/9.6/lambda-nonstrict.eval.golden
index 1d4b8b27224..f2c04fe10eb 100644
--- a/plutus-tx-plugin/test/Strictness/9.6/lambda-nonstrict.eval.golden
+++ b/plutus-tx-plugin/test/Strictness/9.6/lambda-nonstrict.eval.golden
@@ -1,2 +1,2 @@
-An error has occurred:  User error:
+An error has occurred:
 The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.
\ No newline at end of file
diff --git a/plutus-tx-plugin/test/Strictness/9.6/lambda-strict.eval.golden b/plutus-tx-plugin/test/Strictness/9.6/lambda-strict.eval.golden
index 1d4b8b27224..f2c04fe10eb 100644
--- a/plutus-tx-plugin/test/Strictness/9.6/lambda-strict.eval.golden
+++ b/plutus-tx-plugin/test/Strictness/9.6/lambda-strict.eval.golden
@@ -1,2 +1,2 @@
-An error has occurred:  User error:
+An error has occurred:
 The machine terminated because of an error, either from a built-in function or from an explicit use of 'error'.
\ No newline at end of file
diff --git a/plutus-tx-test-util/testlib/PlutusTx/Test/Util/Compiled.hs b/plutus-tx-test-util/testlib/PlutusTx/Test/Util/Compiled.hs
index 1fc7673a871..f5804bca453 100644
--- a/plutus-tx-test-util/testlib/PlutusTx/Test/Util/Compiled.hs
+++ b/plutus-tx-test-util/testlib/PlutusTx/Test/Util/Compiled.hs
@@ -65,7 +65,7 @@ haskellValueToTerm = compiledCodeToTerm . Tx.liftCodeDef
 {- | Just run a term to obtain an `EvaluationResult` (used for tests etc.) -}
 unsafeRunTermCek :: Term -> EvaluationResult Term
 unsafeRunTermCek =
-    unsafeExtractEvaluationResult
+    unsafeToEvaluationResult
         . (\(res, _, _) -> res)
         . runCekDeBruijn PLC.defaultCekParameters Cek.restrictingEnormous Cek.noEmitter