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diff --git a/CHANGELOG.md b/CHANGELOG.md
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--- /dev/null
+++ b/CHANGELOG.md
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+# Revision history for effectful-st
+
+## 0.0.0.0 -- 2022-09-06
+
+* First version. Released on an unsuspecting world.
diff --git a/README.md b/README.md
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+++ b/README.md
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+# `effectful-st`
+
+Version 0.0.0.0
+
+## Description
+
+An [`ST`]-style alternative to the [`Prim`] effect in [`effectful`] that
+allows safely running scoped state transformations without `IOE`.
+
+The `Prim` effect allows the use of [`PrimMonad`] on `Eff` without
+allowing arbitrary `IO`. However, there is no safe way to run the
+effect without introducing the `IOE` effect because `Prim` has no
+way of delimiting the scope of the mutation to `runPrim`. In other
+words, `Prim` is effectively acting merely as a restricted form of
+`IOE` that only allows `PrimMonad`.
+
+`STE` from this package on the other hand borrows the quantification
+trick from [`Control.Monad.ST`][`ST`] to provide a safe way to run
+the effect purely.
+
+This project follows the [Haskell Package Versioning Policy][PVP].
+
+[`ST`]: https://hackage.haskell.org/package/base/docs/Control-Monad-ST.html
+[`Prim`]: https://hackage.haskell.org/package/effectful-core/docs/Effectful-Prim.html
+[`effectful`]: https://hackage.haskell.org/package/effectful-core
+[`PrimMonad`]: https://hackage.haskell.org/package/primitive/docs/Control-Monad-Primitive.html#t:PrimMonad
+[PVP]: https://pvp.haskell.org/
+
+## Copyright
+
+Each contributor waives their Copyright and Related Rights to
+this work according to [CC0-1.0].
+
+[CC0-1.0]: https://creativecommons.org/publicdomain/zero/1.0/
+
+## Patent
+
+Each contributor licenses you to do everything with this work that
+would otherwise infringe any patent claims they can license or become
+able to license.
diff --git a/effectful-st.cabal b/effectful-st.cabal
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--- /dev/null
+++ b/effectful-st.cabal
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+cabal-version:      2.4
+name:               effectful-st
+version:            0.0.0.0
+license:            CC0-1.0
+license-file:       CC0-1.0.txt
+author:             Russell Hernandez Ruiz
+maintainer:         qrpnxz@hyperlife.xyz
+stability:          stable
+homepage:           https://sr.ht/~qrpnxz/effectful-st/
+bug-reports:        https://todo.sr.ht/~qrpnxz/effectful-st
+synopsis:           `ST`-style mutation for `effectful`.
+description:
+  An `ST`-style alternative to the `Prim` effect in `effectful` that
+  allows safely running scoped state transformations without `IOE`.
+  .
+  The `Prim` effect allows the use of `PrimMonad` on `Eff` without
+  allowing arbitrary `IO`. However, there is no safe way to run the
+  effect without introducing the `IOE` effect because `Prim` has no
+  way of delimiting the scope of the mutation to `runPrim`. In other
+  words, `Prim` is effectively acting merely as a restricted form of
+  `IOE` that only allows `PrimMonad`.
+  .
+  `STE` from this package on the other hand borrows the quantification
+  trick from `Control.Monad.ST` to provide a safe way to run the effect
+  purely.
+category:           effectful
+extra-source-files: README.md
+extra-source-files: CHANGELOG.md
+
+source-repository head
+  type:     git
+  location: https://git.sr.ht/~qrpnxz/effectful-st
+
+source-repository this
+  type:     git
+  location: https://git.sr.ht/~qrpnxz/effectful-st
+  tag:      0.0.0.0
+
+library
+  hs-source-dirs:   src
+  exposed-modules:
+      Effectful.ST
+  build-depends:
+      base >=4.13 && <4.18
+    , effectful-core >1 && <2.2
+    , primitive >=0.7 && <0.8
+  default-language: Haskell2010
+  ghc-options:
+    -Wall
+    -Wcompat
+    -Widentities
+    -Wincomplete-record-updates
+    -Wincomplete-uni-patterns
+    -Wpartial-fields
+    -Wredundant-constraints
+  ghc-options:
+    -Wno-redundant-constraints
+    -Wno-unticked-promoted-constructors
diff --git a/src/Effectful/ST.hs b/src/Effectful/ST.hs
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--- /dev/null
+++ b/src/Effectful/ST.hs
@@ -0,0 +1,102 @@
+-- SPDX-License-Identifier: CC0-1.0
+{-
+Each contributor licenses you to do everything with this work that
+would otherwise infringe any patent claims they can license or become
+able to license.
+-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-|
+This modules provides the `STE` effect; a way to run
+the effect purely, with `Prim`, or with `IOE`; and
+functions for lifting abstract and concrete
+state-transformer actions into `Eff`.
+-}
+module Effectful.ST
+  ( -- * Effect
+    STE
+    -- * Handlers
+  , runSTE
+  , steAsPrim
+  , steAsIOE
+    -- * Operations
+    -- ** Prim to STE
+  , primToSTE
+  , stToSTE
+  , stToSTE'
+  , ioToSTE
+    -- ** Prim to IOE
+  , primToIOE
+  , stToIOE
+  , stToIOE'
+  ) where
+
+import Control.Monad.ST ( RealWorld, ST )
+import qualified Control.Monad.ST.Lazy as L
+
+import Unsafe.Coerce ( unsafeCoerce )
+import GHC.IO ( IO(IO) )
+
+import Effectful
+    ( type (:>), Effect, Dispatch(Static), DispatchOf, Eff, IOE )
+import Effectful.Dispatch.Static
+    ( evalStaticRep,
+      unsafeEff_,
+      SideEffects(NoSideEffects),
+      StaticRep )
+import Effectful.Prim ( Prim )
+
+import Control.Monad.Primitive
+    ( PrimBase(..), PrimMonad(PrimState) )
+
+data STE s :: Effect
+-- ^ An effect for delimited primitive state-transformer actions.
+type instance DispatchOf (STE s) = Static NoSideEffects
+data instance StaticRep (STE s) = STERep
+
+-- | Run an 'Eff' computation with primitive state-transformer actions purely.
+runSTE :: (forall s. Eff (STE s : es) a) -> Eff es a
+runSTE eff = evalStaticRep STERep eff
+
+-- | Interpret `STE` as `Prim`.
+steAsPrim :: Prim :> es => Eff (STE (PrimState (Eff es)) : es) a -> Eff es a
+steAsPrim = evalStaticRep STERep
+
+-- | Interpret `STE` as `IOE`.
+steAsIOE :: IOE :> es => Eff (STE RealWorld : es) a -> Eff es a
+steAsIOE = evalStaticRep STERep
+
+-- | Lift a primitive state-transformer action with `STE`.
+primToSTE
+  :: (PrimBase m, STE s :> es, PrimState m ~ s)
+  => m a -> Eff es a
+primToSTE = unsafeEff_ . IO . unsafeCoerce . internal
+
+-- | Lift a strict `ST` action with `STE`.
+stToSTE :: (STE s :> es) => ST s a -> Eff es a
+stToSTE = primToSTE
+
+-- | Lift a lazy `L.ST` action with `STE`.
+stToSTE' :: (STE s :> es) => L.ST s a -> Eff es a
+stToSTE' = primToSTE
+
+-- | Lift an IO action with `STE`.
+ioToSTE :: (STE RealWorld :> es) => IO a -> Eff es a
+ioToSTE = primToSTE
+
+-- | Lift a primitive state-transformer action with `IOE`.
+primToIOE
+  :: (PrimBase m, IOE :> es, PrimState m ~ RealWorld)
+  => m a -> Eff es a
+primToIOE = unsafeEff_ . IO . internal
+
+-- | Lift a strict `ST` action with `IOE`.
+stToIOE :: (IOE :> es) => ST RealWorld a -> Eff es a
+stToIOE = primToIOE
+
+-- | Lift a lazy `L.ST` action with `IOE`.
+stToIOE' :: (IOE :> es) => L.ST RealWorld a -> Eff es a
+stToIOE' = primToIOE