diff --git a/cabal.project b/cabal.project
index 6ecd7821eb..0370d02937 100644
--- a/cabal.project
+++ b/cabal.project
@@ -34,6 +34,11 @@ multi-repl: True
 
 import: ./asserts.cabal
 
+allow-newer: plutus-core:cardano-crypto-class
+           , bytestring
+           , serdoc-core:tasty-quickcheck
+           , kes-agent:base
+
 package ouroboros-network
   -- Certain ThreadNet tests rely on transactions to be submitted promptly after
   -- a node (re)start. Therefore, we disable this flag (see
@@ -44,3 +49,46 @@ package ouroboros-network
 if(os(windows))
   constraints:
     bitvec -simd
+
+source-repository-package
+  type: git
+  location: git@github.com:input-output-hk/kes-agent
+  tag: 7d3517d61004b3e0867b62f1b4cf02ae5eee5589
+  --sha256: sha256-N4XRVqC+UgWej+J16RPh3EO6MSIE3wmJvmP5/nRgIuw=
+  subdir:
+      kes-agent
+
+source-repository-package
+  type: git
+  location: https://github.com/input-output-hk/cardano-ledger
+  tag: 9d380ab7d6ae52ff66aae9a19dbb3036b1b13c94
+  --sha256: sha256-N4XRVqC+UgWej+J16RPh3EO6MSIE3wmJvmP5/nRgIuw=
+  subdir:
+      eras/allegra/impl
+      eras/alonzo/impl
+      eras/alonzo/test-suite
+      eras/babbage/impl
+      eras/babbage/test-suite
+      eras/byron/chain/executable-spec
+      eras/byron/crypto
+      eras/byron/crypto/test
+      eras/byron/ledger/executable-spec
+      eras/byron/ledger/impl
+      eras/byron/ledger/impl/test
+      eras/conway/impl
+      eras/conway/test-suite
+      eras/mary/impl
+      eras/shelley/impl
+      eras/shelley-ma/test-suite
+      eras/shelley/test-suite
+      libs/cardano-data
+      libs/cardano-ledger-api
+      libs/cardano-ledger-binary
+      libs/cardano-ledger-core
+      libs/cardano-ledger-test
+      libs/cardano-protocol-tpraos
+      libs/constrained-generators
+      libs/non-integral
+      libs/set-algebra
+      libs/small-steps
+      libs/vector-map
diff --git a/ouroboros-consensus-cardano/changelog.d/20250130_093803_tdammers_mlocked_kes_rebase.md b/ouroboros-consensus-cardano/changelog.d/20250130_093803_tdammers_mlocked_kes_rebase.md
new file mode 100644
index 0000000000..073423d539
--- /dev/null
+++ b/ouroboros-consensus-cardano/changelog.d/20250130_093803_tdammers_mlocked_kes_rebase.md
@@ -0,0 +1,8 @@
+### Breaking
+
+- Use new mlocked KES API for all internal KES sign key handling.
+- Add finalizers to all block forgings (required by `ouroboros-consensus`).
+- Change `ShelleyLeaderCredentials` to not contain the KES sign key itself
+  anymore. Instead, the `CanBeLeader` data structure now contains a
+  `praosCanBeLeaderCredentialsSource` field, which specifies how to obtain the
+  actual credentials (OpCert and KES SignKey).
diff --git a/ouroboros-consensus-cardano/ouroboros-consensus-cardano.cabal b/ouroboros-consensus-cardano/ouroboros-consensus-cardano.cabal
index 4bcdff0c4e..ad31fbbb7b 100644
--- a/ouroboros-consensus-cardano/ouroboros-consensus-cardano.cabal
+++ b/ouroboros-consensus-cardano/ouroboros-consensus-cardano.cabal
@@ -129,16 +129,16 @@ library
     bytestring >=0.10 && <0.13,
     cardano-binary,
     cardano-crypto,
-    cardano-crypto-class,
+    cardano-crypto-class ^>= 2.2,
     cardano-crypto-wrapper,
     cardano-ledger-allegra ^>=1.6,
     cardano-ledger-alonzo ^>=1.12,
     cardano-ledger-api ^>=1.10,
     cardano-ledger-babbage ^>=1.10,
-    cardano-ledger-binary ^>=1.5,
+    cardano-ledger-binary ^>=1.6,
     cardano-ledger-byron ^>=1.0.1,
     cardano-ledger-conway ^>=1.18,
-    cardano-ledger-core ^>=1.16,
+    cardano-ledger-core ^>=1.17,
     cardano-ledger-mary ^>=1.7,
     cardano-ledger-shelley ^>=1.15,
     cardano-prelude,
@@ -147,9 +147,10 @@ library
     cardano-strict-containers,
     cborg ^>=0.2.2,
     containers >=0.5 && <0.8,
-    cryptonite >=0.25 && <0.31,
+    crypton,
     deepseq,
     formatting >=6.3 && <7.3,
+    kes-agent,
     measures,
     microlens,
     mtl,
@@ -159,6 +160,7 @@ library
     ouroboros-network-api ^>=0.12,
     serialise ^>=0.2,
     small-steps,
+    serdoc-core,
     sop-core ^>=0.5,
     sop-extras ^>=0.2,
     strict-sop-core ^>=0.1,
@@ -301,7 +303,7 @@ library unstable-shelley-testlib
     cardano-ledger-alonzo,
     cardano-ledger-alonzo-test,
     cardano-ledger-babbage-test,
-    cardano-ledger-conway-test >=1.2.1,
+    cardano-ledger-conway-test >=1.3.0,
     cardano-ledger-core:{cardano-ledger-core, testlib},
     cardano-ledger-mary,
     cardano-ledger-shelley:{cardano-ledger-shelley, testlib},
@@ -311,6 +313,7 @@ library unstable-shelley-testlib
     cardano-strict-containers,
     containers,
     generic-random,
+    kes-agent,
     microlens,
     mtl,
     ouroboros-consensus:{ouroboros-consensus, unstable-consensus-testlib},
@@ -319,6 +322,7 @@ library unstable-shelley-testlib
     ouroboros-consensus-protocol:{ouroboros-consensus-protocol, unstable-protocol-testlib},
     ouroboros-network-api,
     quiet ^>=0.2,
+    serdoc-core,
     small-steps,
 
 test-suite shelley-test
@@ -557,6 +561,7 @@ library unstable-cardano-tools
     ouroboros-network-framework ^>=0.16,
     ouroboros-network-protocols,
     resource-registry,
+    serdoc-core,
     serialise ^>=0.2,
     singletons,
     sop-core,
diff --git a/ouroboros-consensus-cardano/src/byron/Ouroboros/Consensus/Byron/Crypto/DSIGN.hs b/ouroboros-consensus-cardano/src/byron/Ouroboros/Consensus/Byron/Crypto/DSIGN.hs
index 5fe214077a..bb8fe671dd 100644
--- a/ouroboros-consensus-cardano/src/byron/Ouroboros/Consensus/Byron/Crypto/DSIGN.hs
+++ b/ouroboros-consensus-cardano/src/byron/Ouroboros/Consensus/Byron/Crypto/DSIGN.hs
@@ -92,7 +92,7 @@ instance DSIGNAlgorithm ByronDSIGN where
       where
         seedBytes = case getBytesFromSeed 32 seed of
           Just (x,_) -> x
-          Nothing    -> throw $ SeedBytesExhausted (-1) -- TODO We can't get the seed size!
+          Nothing    -> throw $ SeedBytesExhausted (-1) (-1) -- TODO We can't get the seed size!
 
     deriveVerKeyDSIGN (SignKeyByronDSIGN sk) = VerKeyByronDSIGN $ toVerification sk
 
diff --git a/ouroboros-consensus-cardano/src/byron/Ouroboros/Consensus/Byron/Node.hs b/ouroboros-consensus-cardano/src/byron/Ouroboros/Consensus/Byron/Node.hs
index 9fb24f382d..76082e4c4e 100644
--- a/ouroboros-consensus-cardano/src/byron/Ouroboros/Consensus/Byron/Node.hs
+++ b/ouroboros-consensus-cardano/src/byron/Ouroboros/Consensus/Byron/Node.hs
@@ -140,6 +140,7 @@ byronBlockForging creds = BlockForging {
                                slot
                                tickedPBftState
     , forgeBlock       = \cfg -> return ....: forgeByronBlock cfg
+    , finalize = pure ()
     }
   where
     canBeLeader = mkPBftCanBeLeader creds
diff --git a/ouroboros-consensus-cardano/src/ouroboros-consensus-cardano/Ouroboros/Consensus/Cardano/Node.hs b/ouroboros-consensus-cardano/src/ouroboros-consensus-cardano/Ouroboros/Consensus/Cardano/Node.hs
index b05dfed499..0e7c1e702e 100644
--- a/ouroboros-consensus-cardano/src/ouroboros-consensus-cardano/Ouroboros/Consensus/Cardano/Node.hs
+++ b/ouroboros-consensus-cardano/src/ouroboros-consensus-cardano/Ouroboros/Consensus/Cardano/Node.hs
@@ -57,8 +57,7 @@ import qualified Cardano.Ledger.Api.Transition as L
 import qualified Cardano.Ledger.BaseTypes as SL
 import qualified Cardano.Ledger.Shelley.API as SL
 import           Cardano.Prelude (cborError)
-import qualified Cardano.Protocol.TPraos.OCert as Absolute (KESPeriod (..),
-                     ocertKESPeriod)
+import qualified Cardano.Protocol.TPraos.OCert as Absolute (KESPeriod (..))
 import qualified Codec.CBOR.Decoding as CBOR
 import           Codec.CBOR.Encoding (Encoding)
 import qualified Codec.CBOR.Encoding as CBOR
@@ -93,10 +92,9 @@ import           Ouroboros.Consensus.Ledger.Extended
 import           Ouroboros.Consensus.Node.NetworkProtocolVersion
 import           Ouroboros.Consensus.Node.ProtocolInfo
 import           Ouroboros.Consensus.Node.Run
-import qualified Ouroboros.Consensus.Protocol.Ledger.HotKey as HotKey
 import           Ouroboros.Consensus.Protocol.Praos (Praos, PraosParams (..))
-import           Ouroboros.Consensus.Protocol.Praos.Common
-                     (praosCanBeLeaderOpCert)
+import           Ouroboros.Consensus.Protocol.Praos.Common (PraosCanBeLeader (..), instantiatePraosCredentials)
+import           Ouroboros.Consensus.Protocol.Praos.AgentClient
 import           Ouroboros.Consensus.Protocol.TPraos (TPraos, TPraosParams (..))
 import qualified Ouroboros.Consensus.Protocol.TPraos as Shelley
 import           Ouroboros.Consensus.Shelley.HFEras ()
@@ -106,14 +104,13 @@ import           Ouroboros.Consensus.Shelley.Ledger.Block (IsShelleyBlock,
                      ShelleyBlockLedgerEra)
 import           Ouroboros.Consensus.Shelley.Ledger.NetworkProtocolVersion
 import           Ouroboros.Consensus.Shelley.Node
-import           Ouroboros.Consensus.Shelley.Node.Common (ShelleyEraWithCrypto,
-                     shelleyBlockIssuerVKey)
+import           Ouroboros.Consensus.Shelley.Node.Common (ShelleyEraWithCrypto, shelleyBlockIssuerVKey)
 import qualified Ouroboros.Consensus.Shelley.Node.Praos as Praos
 import qualified Ouroboros.Consensus.Shelley.Node.TPraos as TPraos
 import           Ouroboros.Consensus.Storage.Serialisation
 import           Ouroboros.Consensus.TypeFamilyWrappers
 import           Ouroboros.Consensus.Util.Assert
-import           Ouroboros.Consensus.Util.IOLike
+
 {-------------------------------------------------------------------------------
   SerialiseHFC
 -------------------------------------------------------------------------------}
@@ -464,7 +461,10 @@ data CardanoProtocolParams c = CardanoProtocolParams {
 -- PRECONDITION: only a single set of Shelley credentials is allowed when used
 -- for mainnet (check against @'SL.gNetworkId' == 'SL.Mainnet'@).
 protocolInfoCardano ::
-     forall c m. (IOLike m, CardanoHardForkConstraints c)
+     forall c m.
+     ( CardanoHardForkConstraints c
+     , KESAgentContext c m
+     )
   => CardanoProtocolParams c
   -> ( ProtocolInfo      (CardanoBlock c)
      , m [BlockForging m (CardanoBlock c)]
@@ -479,7 +479,7 @@ protocolInfoCardano paramsCardano
         pInfoConfig       = cfg
       , pInfoInitLedger   = initExtLedgerStateCardano
       }
-    , blockForging
+    , mkBlockForgings
     )
   where
     CardanoProtocolParams {
@@ -826,8 +826,8 @@ protocolInfoCardano paramsCardano
     -- credentials. If there are multiple Shelley credentials, we merge the
     -- Byron credentials with the first Shelley one but still have separate
     -- threads for the remaining Shelley ones.
-    blockForging :: m [BlockForging m (CardanoBlock c)]
-    blockForging = do
+    mkBlockForgings :: m [BlockForging m (CardanoBlock c)]
+    mkBlockForgings = do
         shelleyBased <- traverse blockForgingShelleyBased credssShelleyBased
         let blockForgings :: [NonEmptyOptNP (BlockForging m) (CardanoEras c)]
             blockForgings = case (mBlockForgingByron, shelleyBased) of
@@ -853,24 +853,19 @@ protocolInfoCardano paramsCardano
          ShelleyLeaderCredentials c
       -> m (NonEmptyOptNP (BlockForging m) (CardanoEras c))
     blockForgingShelleyBased credentials = do
-        let ShelleyLeaderCredentials
-              { shelleyLeaderCredentialsInitSignKey = initSignKey
-              , shelleyLeaderCredentialsCanBeLeader = canBeLeader
-              } = credentials
-
-        hotKey <- do
-          let maxKESEvo :: Word64
-              maxKESEvo = assert (tpraosMaxKESEvo == praosMaxKESEvo) praosMaxKESEvo
-
-              startPeriod :: Absolute.KESPeriod
-              startPeriod = Absolute.ocertKESPeriod $ praosCanBeLeaderOpCert canBeLeader
-
-          HotKey.mkHotKey @m @c initSignKey startPeriod maxKESEvo
+        let canBeLeader = shelleyLeaderCredentialsCanBeLeader credentials
 
         let slotToPeriod :: SlotNo -> Absolute.KESPeriod
             slotToPeriod (SlotNo slot) = assert (tpraosSlotsPerKESPeriod == praosSlotsPerKESPeriod) $
               Absolute.KESPeriod $ fromIntegral $ slot `div` praosSlotsPerKESPeriod
 
+            maxKESEvo :: Word64
+            maxKESEvo = assert (tpraosMaxKESEvo == praosMaxKESEvo) praosMaxKESEvo
+
+        hotKey <- instantiatePraosCredentials
+                    maxKESEvo
+                    (praosCanBeLeaderCredentialsSource canBeLeader)
+
         let tpraos :: forall era.
                  ShelleyEraWithCrypto c       (TPraos c) era
               => BlockForging m (ShelleyBlock (TPraos c) era)
diff --git a/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/Common.hs b/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/Common.hs
index 572ed23a4e..9683f3a0be 100644
--- a/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/Common.hs
+++ b/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/Common.hs
@@ -48,12 +48,7 @@ import           Ouroboros.Consensus.Storage.ImmutableDB
 -------------------------------------------------------------------------------}
 
 data ShelleyLeaderCredentials c = ShelleyLeaderCredentials
-  { -- | The unevolved signing KES key (at evolution 0).
-    --
-    -- Note that this is not inside 'ShelleyCanBeLeader' since it gets evolved
-    -- automatically, whereas 'ShelleyCanBeLeader' does not change.
-    shelleyLeaderCredentialsInitSignKey :: SL.SignKeyKES c,
-    shelleyLeaderCredentialsCanBeLeader :: PraosCanBeLeader c,
+  { shelleyLeaderCredentialsCanBeLeader :: PraosCanBeLeader c,
     -- | Identifier for this set of credentials.
     --
     -- Useful when the node is running with multiple sets of credentials.
diff --git a/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/Praos.hs b/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/Praos.hs
index 35fcbaf0ba..626d016858 100644
--- a/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/Praos.hs
+++ b/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/Praos.hs
@@ -28,8 +28,6 @@ import qualified Ouroboros.Consensus.Ledger.SupportsMempool as Mempool
 import qualified Ouroboros.Consensus.Protocol.Ledger.HotKey as HotKey
 import           Ouroboros.Consensus.Protocol.Praos (Praos, PraosParams (..),
                      praosCheckCanForge)
-import           Ouroboros.Consensus.Protocol.Praos.Common
-                     (PraosCanBeLeader (praosCanBeLeaderOpCert))
 import           Ouroboros.Consensus.Shelley.Eras (EraCrypto)
 import           Ouroboros.Consensus.Shelley.Ledger (ShelleyBlock,
                      ShelleyCompatible, forgeShelleyBlock)
@@ -51,21 +49,13 @@ praosBlockForging ::
      , IOLike m
      )
   => PraosParams
+  -> HotKey.HotKey c m
   -> ShelleyLeaderCredentials (EraCrypto era)
-  -> m (BlockForging m (ShelleyBlock (Praos c) era))
-praosBlockForging praosParams credentials = do
-    hotKey <- HotKey.mkHotKey @m @c initSignKey startPeriod praosMaxKESEvo
-    pure $ praosSharedBlockForging hotKey slotToPeriod credentials
+  -> BlockForging m (ShelleyBlock (Praos c) era)
+praosBlockForging praosParams hotKey credentials =
+    praosSharedBlockForging hotKey slotToPeriod credentials
   where
-    PraosParams {praosMaxKESEvo, praosSlotsPerKESPeriod} = praosParams
-
-    ShelleyLeaderCredentials {
-        shelleyLeaderCredentialsInitSignKey = initSignKey
-      , shelleyLeaderCredentialsCanBeLeader = canBeLeader
-      } = credentials
-
-    startPeriod :: Absolute.KESPeriod
-    startPeriod = SL.ocertKESPeriod $ praosCanBeLeaderOpCert canBeLeader
+    PraosParams {praosSlotsPerKESPeriod} = praosParams
 
     slotToPeriod :: SlotNo -> Absolute.KESPeriod
     slotToPeriod (SlotNo slot) =
@@ -90,7 +80,7 @@ praosSharedBlockForging
   ShelleyLeaderCredentials {
       shelleyLeaderCredentialsCanBeLeader = canBeLeader
     , shelleyLeaderCredentialsLabel = label
-    } = do
+    } =
     BlockForging
       { forgeLabel = label <> "_" <> T.pack (L.eraName @era),
         canBeLeader = canBeLeader,
@@ -105,5 +95,6 @@ praosSharedBlockForging
           forgeShelleyBlock
             hotKey
             canBeLeader
-            cfg
+            cfg,
+        finalize = HotKey.finalize hotKey
       }
diff --git a/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/TPraos.hs b/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/TPraos.hs
index 82e5698885..e8654532ed 100644
--- a/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/TPraos.hs
+++ b/ouroboros-consensus-cardano/src/shelley/Ouroboros/Consensus/Shelley/Node/TPraos.hs
@@ -33,9 +33,11 @@ module Ouroboros.Consensus.Shelley.Node.TPraos (
   ) where
 
 import qualified Cardano.Crypto.VRF as VRF
+import qualified Cardano.Crypto.KES as KES
 import qualified Cardano.Ledger.Api.Era as L
 import qualified Cardano.Ledger.Api.Transition as L
 import qualified Cardano.Ledger.Shelley.API as SL
+import           Cardano.Ledger.Crypto (KES)
 import qualified Cardano.Protocol.TPraos.API as SL
 import qualified Cardano.Protocol.TPraos.OCert as Absolute (KESPeriod (..))
 import qualified Cardano.Protocol.TPraos.OCert as SL
@@ -43,6 +45,7 @@ import           Cardano.Slotting.EpochInfo
 import           Cardano.Slotting.Time (mkSlotLength)
 import           Control.Monad.Except (Except)
 import           Data.Bifunctor (first)
+import qualified Data.SerDoc.Class as SerDoc
 import qualified Data.Text as T
 import qualified Data.Text as Text
 import           Lens.Micro ((^.))
@@ -59,17 +62,20 @@ import           Ouroboros.Consensus.Protocol.Ledger.HotKey (HotKey)
 import qualified Ouroboros.Consensus.Protocol.Ledger.HotKey as HotKey
 import           Ouroboros.Consensus.Protocol.Praos.Common
 import           Ouroboros.Consensus.Protocol.TPraos
+import           Ouroboros.Consensus.Protocol.Praos.AgentClient
 import           Ouroboros.Consensus.Shelley.Eras
 import           Ouroboros.Consensus.Shelley.Ledger
 import           Ouroboros.Consensus.Shelley.Ledger.Inspect ()
 import           Ouroboros.Consensus.Shelley.Ledger.NetworkProtocolVersion ()
 import           Ouroboros.Consensus.Shelley.Node.Common
                      (ProtocolParamsShelleyBased (..), ShelleyEraWithCrypto,
-                     ShelleyLeaderCredentials (..), shelleyBlockIssuerVKey)
+                     ShelleyLeaderCredentials (..),
+                     shelleyBlockIssuerVKey)
 import           Ouroboros.Consensus.Shelley.Node.Serialisation ()
 import           Ouroboros.Consensus.Shelley.Protocol.TPraos ()
 import           Ouroboros.Consensus.Util.Assert
 import           Ouroboros.Consensus.Util.IOLike
+import qualified Cardano.KESAgent.Serialization.DirectCodec as Agent
 
 {-------------------------------------------------------------------------------
   BlockForging
@@ -88,21 +94,13 @@ shelleyBlockForging ::
       , IOLike m
       )
   => TPraosParams
+  -> HotKey c m
   -> ShelleyLeaderCredentials (EraCrypto era)
-  -> m (BlockForging m (ShelleyBlock (TPraos c) era))
-shelleyBlockForging tpraosParams credentials = do
-    hotKey <- HotKey.mkHotKey @m @c initSignKey startPeriod tpraosMaxKESEvo
-    pure $ shelleySharedBlockForging hotKey slotToPeriod credentials
+  -> BlockForging m (ShelleyBlock (TPraos c) era)
+shelleyBlockForging tpraosParams hotKey credentials = do
+    shelleySharedBlockForging hotKey slotToPeriod credentials
   where
-    TPraosParams {tpraosMaxKESEvo, tpraosSlotsPerKESPeriod} = tpraosParams
-
-    ShelleyLeaderCredentials {
-        shelleyLeaderCredentialsInitSignKey = initSignKey
-      , shelleyLeaderCredentialsCanBeLeader = canBeLeader
-      } = credentials
-
-    startPeriod :: Absolute.KESPeriod
-    startPeriod = SL.ocertKESPeriod $ praosCanBeLeaderOpCert canBeLeader
+    TPraosParams {tpraosSlotsPerKESPeriod} = tpraosParams
 
     slotToPeriod :: SlotNo -> Absolute.KESPeriod
     slotToPeriod (SlotNo slot) =
@@ -139,6 +137,7 @@ shelleySharedBlockForging hotKey slotToPeriod credentials =
             hotKey
             canBeLeader
             cfg
+      , finalize = HotKey.finalize hotKey
       }
   where
     ShelleyLeaderCredentials {
@@ -173,8 +172,12 @@ protocolInfoShelley ::
      forall m c.
       ( IOLike m
       , PraosCrypto c
+      , AgentCrypto c
       , ShelleyCompatible (TPraos c) (ShelleyEra c)
       , TxLimits (ShelleyBlock (TPraos c) (ShelleyEra c))
+      , MonadKESAgent m
+      , SerDoc.HasInfo (Agent.DirectCodec m) (KES.VerKeyKES (KES c))
+      , SerDoc.HasInfo (Agent.DirectCodec m) (KES.SignKeyKES (KES c))
       )
   => SL.ShelleyGenesis c
   -> ProtocolParamsShelleyBased c
@@ -192,11 +195,11 @@ protocolInfoShelley shelleyGenesis
 
 protocolInfoTPraosShelleyBased ::
      forall m era c.
-      ( IOLike m
-      , PraosCrypto c
+      ( PraosCrypto c
       , ShelleyCompatible (TPraos c) era
       , TxLimits (ShelleyBlock (TPraos c) era)
       , c ~ EraCrypto era
+      , KESAgentContext c m
       )
   => ProtocolParamsShelleyBased c
   -> L.TransitionConfig era
@@ -216,11 +219,20 @@ protocolInfoTPraosShelleyBased ProtocolParamsShelleyBased {
         pInfoConfig       = topLevelConfig
       , pInfoInitLedger   = initExtLedgerState
       }
-    , traverse
-        (shelleyBlockForging tpraosParams)
-        credentialss
+    , traverse mkBlockForging credentialss
     )
   where
+    mkBlockForging :: ShelleyLeaderCredentials c -> m (BlockForging m (ShelleyBlock (TPraos c) era))
+    mkBlockForging credentials = do
+      let canBeLeader = shelleyLeaderCredentialsCanBeLeader credentials
+
+      hotKey :: HotKey c m <-
+                  instantiatePraosCredentials
+                    (tpraosMaxKESEvo tpraosParams)
+                    (praosCanBeLeaderCredentialsSource canBeLeader)
+
+      return $ shelleyBlockForging tpraosParams hotKey credentials
+
     genesis :: SL.ShelleyGenesis c
     genesis = transitionCfg ^. L.tcShelleyGenesisL
 
diff --git a/ouroboros-consensus-cardano/src/unstable-byron-testlib/Ouroboros/Consensus/ByronDual/Node.hs b/ouroboros-consensus-cardano/src/unstable-byron-testlib/Ouroboros/Consensus/ByronDual/Node.hs
index 0b2045dd7c..c6f81b9aa0 100644
--- a/ouroboros-consensus-cardano/src/unstable-byron-testlib/Ouroboros/Consensus/ByronDual/Node.hs
+++ b/ouroboros-consensus-cardano/src/unstable-byron-testlib/Ouroboros/Consensus/ByronDual/Node.hs
@@ -66,6 +66,7 @@ dualByronBlockForging creds = BlockForging {
         fmap castForgeStateUpdateInfo .: updateForgeState (dualTopLevelConfigMain cfg)
     , checkCanForge    = checkCanForge . dualTopLevelConfigMain
     , forgeBlock       = return .....: forgeDualByronBlock
+    , finalize         = return ()
     }
   where
     BlockForging {..} = byronBlockForging creds
diff --git a/ouroboros-consensus-cardano/src/unstable-cardano-testlib/Test/Consensus/Cardano/ProtocolInfo.hs b/ouroboros-consensus-cardano/src/unstable-cardano-testlib/Test/Consensus/Cardano/ProtocolInfo.hs
index e3943da9f6..53eaa9ca97 100644
--- a/ouroboros-consensus-cardano/src/unstable-cardano-testlib/Test/Consensus/Cardano/ProtocolInfo.hs
+++ b/ouroboros-consensus-cardano/src/unstable-cardano-testlib/Test/Consensus/Cardano/ProtocolInfo.hs
@@ -21,6 +21,7 @@ module Test.Consensus.Cardano.ProtocolInfo (
   , protocolVersionZero
   ) where
 
+import           Ouroboros.Consensus.Protocol.Praos.AgentClient (KESAgentContext)
 import qualified Cardano.Chain.Genesis as CC.Genesis
 import qualified Cardano.Chain.Update as CC.Update
 import           Cardano.Ledger.Api.Era (StandardCrypto)
@@ -50,7 +51,6 @@ import           Ouroboros.Consensus.Protocol.PBFT (PBftParams,
 import           Ouroboros.Consensus.Shelley.Node
                      (ProtocolParamsShelleyBased (..), ShelleyGenesis,
                      ShelleyLeaderCredentials)
-import           Ouroboros.Consensus.Util.IOLike (IOLike)
 import qualified Test.Cardano.Ledger.Alonzo.Examples.Consensus as SL
 import qualified Test.Cardano.Ledger.Conway.Examples.Consensus as SL
 import qualified Test.ThreadNet.Infra.Byron as Byron
@@ -214,7 +214,10 @@ mkSimpleTestProtocolInfo
 --
 mkTestProtocolInfo ::
      forall m c
-   . (CardanoHardForkConstraints c, IOLike m, c ~ StandardCrypto)
+   . ( CardanoHardForkConstraints c
+     , KESAgentContext c m
+     , c ~ StandardCrypto
+     )
   => (CoreNodeId, Shelley.CoreNode c)
   -- ^ Id of the node for which the protocol info will be elaborated.
   -> ShelleyGenesis c
diff --git a/ouroboros-consensus-cardano/src/unstable-cardano-testlib/Test/ThreadNet/Infra/ShelleyBasedHardFork.hs b/ouroboros-consensus-cardano/src/unstable-cardano-testlib/Test/ThreadNet/Infra/ShelleyBasedHardFork.hs
index 6f12f3d9b6..aa8ac2e578 100644
--- a/ouroboros-consensus-cardano/src/unstable-cardano-testlib/Test/ThreadNet/Infra/ShelleyBasedHardFork.hs
+++ b/ouroboros-consensus-cardano/src/unstable-cardano-testlib/Test/ThreadNet/Infra/ShelleyBasedHardFork.hs
@@ -56,13 +56,14 @@ import           Ouroboros.Consensus.Ledger.SupportsProtocol
                      (LedgerSupportsProtocol)
 import           Ouroboros.Consensus.Node
 import           Ouroboros.Consensus.Node.NetworkProtocolVersion
+import           Ouroboros.Consensus.Protocol.Praos.AgentClient (KESAgentContext)
 import           Ouroboros.Consensus.Protocol.TPraos
 import           Ouroboros.Consensus.Shelley.Eras
 import           Ouroboros.Consensus.Shelley.Ledger
 import           Ouroboros.Consensus.Shelley.Node
+import           Ouroboros.Consensus.Shelley.Protocol.Abstract (ProtoCrypto)
 import           Ouroboros.Consensus.TypeFamilyWrappers
 import           Ouroboros.Consensus.Util (eitherToMaybe)
-import           Ouroboros.Consensus.Util.IOLike (IOLike)
 import           Test.ThreadNet.TxGen
 import           Test.ThreadNet.TxGen.Shelley ()
 
@@ -265,7 +266,9 @@ instance ShelleyBasedHardForkConstraints proto1 era1 proto2 era2
 
 protocolInfoShelleyBasedHardFork ::
      forall m proto1 era1 proto2 era2.
-     (IOLike m, ShelleyBasedHardForkConstraints proto1 era1 proto2 era2)
+     ( KESAgentContext (ProtoCrypto proto2) m
+     , ShelleyBasedHardForkConstraints proto1 era1 proto2 era2
+     )
   => ProtocolParamsShelleyBased (EraCrypto era1)
   -> SL.ProtVer
   -> SL.ProtVer
diff --git a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/Key.hs b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/Key.hs
index 6322d3aa3d..559035aebc 100644
--- a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/Key.hs
+++ b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/Key.hs
@@ -9,7 +9,6 @@ module Cardano.Api.Key (
   , CastSigningKeyRole (..)
   , CastVerificationKeyRole (..)
   , Key (..)
-  , generateSigningKey
   ) where
 
 import           Cardano.Api.Any
@@ -51,16 +50,17 @@ class (Eq (VerificationKey keyrole),
     verificationKeyHash :: VerificationKey keyrole -> Hash keyrole
 
 
--- TODO: We should move this into the Key type class, with the existing impl as the default impl.
--- For KES we can then override it to keep the seed and key in mlocked memory at all times.
--- | Generate a 'SigningKey' using a seed from operating system entropy.
---
-generateSigningKey :: Key keyrole => AsType keyrole -> IO (SigningKey keyrole)
-generateSigningKey keytype = do
-    seed <- Crypto.readSeedFromSystemEntropy seedSize
-    return $! deterministicSigningKey keytype seed
-  where
-    seedSize = deterministicSigningKeySeedSize keytype
+    -- | Generate a 'SigningKey' using a seed from operating system entropy.
+    generateSigningKey :: AsType keyrole -> IO (SigningKey keyrole)
+    generateSigningKey keytype = do
+        --
+        -- For KES we can override this to keep the seed and key in mlocked memory
+        -- at all times.
+        --
+        seed <- Crypto.readSeedFromSystemEntropy seedSize
+        return $! deterministicSigningKey keytype seed
+      where
+        seedSize = deterministicSigningKeySeedSize keytype
 
 
 instance HasTypeProxy a => HasTypeProxy (VerificationKey a) where
diff --git a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/KeysPraos.hs b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/KeysPraos.hs
index 153f0a3cd5..e852db11aa 100644
--- a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/KeysPraos.hs
+++ b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/KeysPraos.hs
@@ -14,7 +14,7 @@
 --
 module Cardano.Api.KeysPraos (
     -- * Key types
-    KesKey
+    UnsoundPureKesKey
   , VrfKey
     -- * Data family instances
   , AsType (..)
@@ -31,7 +31,7 @@ import qualified Cardano.Crypto.DSIGN.Class as Crypto
 import qualified Cardano.Crypto.Hash.Class as Crypto
 import qualified Cardano.Crypto.KES.Class as Crypto
 import qualified Cardano.Crypto.VRF.Class as Crypto
-import           Cardano.Ledger.Crypto (StandardCrypto)
+import           Cardano.Ledger.Crypto (Crypto(..), StandardCrypto)
 import qualified Cardano.Ledger.Crypto as Shelley (KES, VRF)
 import qualified Cardano.Ledger.Keys as Shelley
 import           Data.String (IsString (..))
@@ -40,95 +40,95 @@ import           Data.String (IsString (..))
 -- KES keys
 --
 
-data KesKey
+data UnsoundPureKesKey
 
-instance HasTypeProxy KesKey where
-    data AsType KesKey = AsKesKey
-    proxyToAsType _ = AsKesKey
+instance HasTypeProxy UnsoundPureKesKey where
+    data AsType UnsoundPureKesKey = AsUnsoundPureKesKey
+    proxyToAsType _ = AsUnsoundPureKesKey
 
-instance Key KesKey where
+instance Key UnsoundPureKesKey where
 
-    newtype VerificationKey KesKey =
+    newtype VerificationKey UnsoundPureKesKey =
         KesVerificationKey (Shelley.VerKeyKES StandardCrypto)
       deriving stock (Eq)
-      deriving (Show, IsString) via UsingRawBytesHex (VerificationKey KesKey)
+      deriving (Show, IsString) via UsingRawBytesHex (VerificationKey UnsoundPureKesKey)
       deriving newtype (EncCBOR, DecCBOR, ToCBOR, FromCBOR)
       deriving anyclass SerialiseAsCBOR
 
-    newtype SigningKey KesKey =
-        KesSigningKey (Shelley.SignKeyKES StandardCrypto)
-      deriving (Show, IsString) via UsingRawBytesHex (SigningKey KesKey)
-      deriving newtype (EncCBOR, DecCBOR, ToCBOR, FromCBOR)
-      deriving anyclass SerialiseAsCBOR
+    newtype SigningKey UnsoundPureKesKey =
+        KesSigningKey (Crypto.UnsoundPureSignKeyKES (KES StandardCrypto))
+      deriving (Show, IsString) via UsingRawBytesHex (SigningKey UnsoundPureKesKey)
+      deriving newtype (ToCBOR, FromCBOR)
+      deriving anyclass (EncCBOR, DecCBOR, SerialiseAsCBOR)
 
     --This loses the mlock safety of the seed, since it starts from a normal in-memory seed.
-    deterministicSigningKey :: AsType KesKey -> Crypto.Seed -> SigningKey KesKey
-    deterministicSigningKey AsKesKey =
-        KesSigningKey . Crypto.genKeyKES
+    deterministicSigningKey :: AsType UnsoundPureKesKey -> Crypto.Seed -> SigningKey UnsoundPureKesKey
+    deterministicSigningKey AsUnsoundPureKesKey =
+        KesSigningKey . Crypto.unsoundPureGenKeyKES
 
-    deterministicSigningKeySeedSize :: AsType KesKey -> Word
-    deterministicSigningKeySeedSize AsKesKey =
+    deterministicSigningKeySeedSize :: AsType UnsoundPureKesKey -> Word
+    deterministicSigningKeySeedSize AsUnsoundPureKesKey =
         Crypto.seedSizeKES proxy
       where
         proxy :: Proxy (Shelley.KES StandardCrypto)
         proxy = Proxy
 
-    getVerificationKey :: SigningKey KesKey -> VerificationKey KesKey
+    getVerificationKey :: SigningKey UnsoundPureKesKey -> VerificationKey UnsoundPureKesKey
     getVerificationKey (KesSigningKey sk) =
-        KesVerificationKey (Crypto.deriveVerKeyKES sk)
+        KesVerificationKey (Crypto.unsoundPureDeriveVerKeyKES sk)
 
-    verificationKeyHash :: VerificationKey KesKey -> Hash KesKey
+    verificationKeyHash :: VerificationKey UnsoundPureKesKey -> Hash UnsoundPureKesKey
     verificationKeyHash (KesVerificationKey vkey) =
-        KesKeyHash (Crypto.hashVerKeyKES vkey)
+        UnsoundPureKesKeyHash (Crypto.hashVerKeyKES vkey)
 
 
-instance SerialiseAsRawBytes (VerificationKey KesKey) where
+instance SerialiseAsRawBytes (VerificationKey UnsoundPureKesKey) where
     serialiseToRawBytes (KesVerificationKey vk) =
       Crypto.rawSerialiseVerKeyKES vk
 
-    deserialiseFromRawBytes (AsVerificationKey AsKesKey) bs =
+    deserialiseFromRawBytes (AsVerificationKey AsUnsoundPureKesKey) bs =
       KesVerificationKey <$>
         Crypto.rawDeserialiseVerKeyKES bs
 
-instance SerialiseAsRawBytes (SigningKey KesKey) where
+instance SerialiseAsRawBytes (SigningKey UnsoundPureKesKey) where
     serialiseToRawBytes (KesSigningKey sk) =
-      Crypto.rawSerialiseSignKeyKES sk
+      Crypto.rawSerialiseUnsoundPureSignKeyKES sk
 
-    deserialiseFromRawBytes (AsSigningKey AsKesKey) bs =
-      KesSigningKey <$> Crypto.rawDeserialiseSignKeyKES bs
+    deserialiseFromRawBytes (AsSigningKey AsUnsoundPureKesKey) bs =
+      KesSigningKey <$> Crypto.rawDeserialiseUnsoundPureSignKeyKES bs
 
-instance SerialiseAsBech32 (VerificationKey KesKey) where
+instance SerialiseAsBech32 (VerificationKey UnsoundPureKesKey) where
     bech32PrefixFor         _ =  "kes_vk"
     bech32PrefixesPermitted _ = ["kes_vk"]
 
-instance SerialiseAsBech32 (SigningKey KesKey) where
+instance SerialiseAsBech32 (SigningKey UnsoundPureKesKey) where
     bech32PrefixFor         _ =  "kes_sk"
     bech32PrefixesPermitted _ = ["kes_sk"]
 
 
-newtype instance Hash KesKey =
-    KesKeyHash (Shelley.Hash StandardCrypto
+newtype instance Hash UnsoundPureKesKey =
+    UnsoundPureKesKeyHash (Shelley.Hash StandardCrypto
                              (Shelley.VerKeyKES StandardCrypto))
   deriving stock (Eq, Ord)
-  deriving (Show, IsString) via UsingRawBytesHex (Hash KesKey)
-  deriving (ToCBOR, FromCBOR) via UsingRawBytes (Hash KesKey)
+  deriving (Show, IsString) via UsingRawBytesHex (Hash UnsoundPureKesKey)
+  deriving (ToCBOR, FromCBOR) via UsingRawBytes (Hash UnsoundPureKesKey)
   deriving anyclass SerialiseAsCBOR
 
-instance SerialiseAsRawBytes (Hash KesKey) where
-    serialiseToRawBytes (KesKeyHash vkh) =
+instance SerialiseAsRawBytes (Hash UnsoundPureKesKey) where
+    serialiseToRawBytes (UnsoundPureKesKeyHash vkh) =
       Crypto.hashToBytes vkh
 
-    deserialiseFromRawBytes (AsHash AsKesKey) bs =
-      KesKeyHash <$> Crypto.hashFromBytes bs
+    deserialiseFromRawBytes (AsHash AsUnsoundPureKesKey) bs =
+      UnsoundPureKesKeyHash <$> Crypto.hashFromBytes bs
 
-instance HasTextEnvelope (VerificationKey KesKey) where
+instance HasTextEnvelope (VerificationKey UnsoundPureKesKey) where
     textEnvelopeType _ = "KesVerificationKey_"
                       <> fromString (Crypto.algorithmNameKES proxy)
       where
         proxy :: Proxy (Shelley.KES StandardCrypto)
         proxy = Proxy
 
-instance HasTextEnvelope (SigningKey KesKey) where
+instance HasTextEnvelope (SigningKey UnsoundPureKesKey) where
     textEnvelopeType _ = "KesSigningKey_"
                       <> fromString (Crypto.algorithmNameKES proxy)
       where
diff --git a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/OperationalCertificate.hs b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/OperationalCertificate.hs
index 9570a3175b..be6f1c9222 100644
--- a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/OperationalCertificate.hs
+++ b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/OperationalCertificate.hs
@@ -94,7 +94,7 @@ instance HasTypeProxy OperationalCertificateIssueCounter where
 instance HasTextEnvelope OperationalCertificate where
     textEnvelopeType _ = "NodeOperationalCertificate"
 
-getHotKey :: OperationalCertificate -> VerificationKey KesKey
+getHotKey :: OperationalCertificate -> VerificationKey UnsoundPureKesKey
 getHotKey (OperationalCertificate cert _) = KesVerificationKey $ Shelley.ocertVkHot cert
 
 getKesPeriod :: OperationalCertificate -> Word
diff --git a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/Protocol/Types.hs b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/Protocol/Types.hs
index 60aa1de618..2c442cac17 100644
--- a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/Protocol/Types.hs
+++ b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Api/Protocol/Types.hs
@@ -6,6 +6,7 @@
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE UndecidableInstances #-}
 
 -- DUPLICATE -- adapted from: cardano-api/src/Cardano/Api/Protocol/Types.hs
 
@@ -30,13 +31,14 @@ import qualified Ouroboros.Consensus.Ledger.SupportsProtocol as Consensus
 import           Ouroboros.Consensus.Node.ProtocolInfo (ProtocolClientInfo (..),
                      ProtocolInfo (..))
 import           Ouroboros.Consensus.Node.Run (RunNode)
+import           Ouroboros.Consensus.Protocol.Praos.AgentClient
 import qualified Ouroboros.Consensus.Protocol.TPraos as Consensus
 import qualified Ouroboros.Consensus.Shelley.Eras as Consensus (ShelleyEra)
 import qualified Ouroboros.Consensus.Shelley.Ledger.Block as Consensus
                      (ShelleyBlock)
 import           Ouroboros.Consensus.Shelley.Ledger.SupportsProtocol ()
 import           Ouroboros.Consensus.Shelley.ShelleyHFC (ShelleyBlockHFC)
-import           Ouroboros.Consensus.Util.IOLike (IOLike)
+import           Ouroboros.Consensus.Util.IOLike
 
 
 class (RunNode blk, IOLike m) => Protocol m blk where
@@ -62,7 +64,11 @@ instance IOLike m => Protocol m ByronBlockHFC where
                                                 , pure . map inject $ blockForgingByron params
                                                 )
 
-instance (CardanoHardForkConstraints StandardCrypto, IOLike m) => Protocol m (CardanoBlock StandardCrypto) where
+instance ( CardanoHardForkConstraints StandardCrypto
+         , IOLike m
+         , MonadKESAgent m
+         )
+  => Protocol m (CardanoBlock StandardCrypto) where
   data ProtocolInfoArgs m (CardanoBlock StandardCrypto) =
          ProtocolInfoArgsCardano
           (CardanoProtocolParams StandardCrypto)
@@ -83,6 +89,7 @@ instance CardanoHardForkConstraints StandardCrypto => ProtocolClient (CardanoBlo
     protocolClientInfoCardano epochSlots
 
 instance ( IOLike m
+         , MonadKESAgent m
          , Consensus.LedgerSupportsProtocol
              (Consensus.ShelleyBlock
                 (Consensus.TPraos StandardCrypto) (ShelleyEra StandardCrypto))
diff --git a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Node/Protocol/Shelley.hs b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Node/Protocol/Shelley.hs
index fd58263650..743517cba9 100644
--- a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Node/Protocol/Shelley.hs
+++ b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Node/Protocol/Shelley.hs
@@ -45,7 +45,7 @@ import qualified Data.ByteString as BS
 import qualified Data.Text as T
 import qualified Ouroboros.Consensus.Cardano as Consensus
 import           Ouroboros.Consensus.Protocol.Praos.Common
-                     (PraosCanBeLeader (..))
+                     (PraosCanBeLeader (..), PraosCredentialsSource (..))
 import           Ouroboros.Consensus.Shelley.Node (Nonce (..),
                      ProtocolParamsShelleyBased (..), ShelleyGenesis (..),
                      ShelleyLeaderCredentials (..))
@@ -170,12 +170,12 @@ opCertKesKeyCheck ::
   -- ^ KES key
   -> FilePath
   -- ^ Operational certificate
-  -> ExceptT PraosLeaderCredentialsError IO (OperationalCertificate, SigningKey KesKey)
+  -> ExceptT PraosLeaderCredentialsError IO (OperationalCertificate, SigningKey UnsoundPureKesKey)
 opCertKesKeyCheck kesFile certFile = do
   opCert <-
     firstExceptT FileError (newExceptT $ readFileTextEnvelope AsOperationalCertificate certFile)
   kesSKey <-
-    firstExceptT FileError (newExceptT $ readFileTextEnvelope (AsSigningKey AsKesKey) kesFile)
+    firstExceptT FileError (newExceptT $ readFileTextEnvelope (AsSigningKey AsUnsoundPureKesKey) kesFile)
   let opCertSpecifiedKesKeyhash = verificationKeyHash $ getHotKey opCert
       suppliedKesKeyHash = verificationKeyHash $ getVerificationKey kesSKey
   -- Specified KES key in operational certificate should match the one
@@ -200,11 +200,11 @@ readLeaderCredentialsBulk ProtocolFilepaths { shelleyBulkCredsFile = mfp } =
    parseShelleyCredentials
      :: ShelleyCredentials
      -> ExceptT PraosLeaderCredentialsError IO (ShelleyLeaderCredentials StandardCrypto)
-   parseShelleyCredentials ShelleyCredentials { scCert, scVrf, scKes } = do
+   parseShelleyCredentials ShelleyCredentials { scCert, scVrf, scKes } =
      mkPraosLeaderCredentials
-       <$> parseEnvelope AsOperationalCertificate scCert
-       <*> parseEnvelope (AsSigningKey AsVrfKey) scVrf
-       <*> parseEnvelope (AsSigningKey AsKesKey) scKes
+      <$> parseEnvelope AsOperationalCertificate scCert
+      <*> parseEnvelope (AsSigningKey AsVrfKey) scVrf
+      <*> parseEnvelope (AsSigningKey AsUnsoundPureKesKey) scKes
 
    readBulkFile
      :: Maybe FilePath
@@ -228,7 +228,7 @@ readLeaderCredentialsBulk ProtocolFilepaths { shelleyBulkCredsFile = mfp } =
 mkPraosLeaderCredentials ::
      OperationalCertificate
   -> SigningKey VrfKey
-  -> SigningKey KesKey
+  -> SigningKey UnsoundPureKesKey
   -> ShelleyLeaderCredentials StandardCrypto
 mkPraosLeaderCredentials
     (OperationalCertificate opcert (StakePoolVerificationKey vkey))
@@ -237,11 +237,10 @@ mkPraosLeaderCredentials
     ShelleyLeaderCredentials
     { shelleyLeaderCredentialsCanBeLeader =
         PraosCanBeLeader {
-        praosCanBeLeaderOpCert     = opcert,
           praosCanBeLeaderColdVerKey = coerceKeyRole vkey,
-          praosCanBeLeaderSignKeyVRF = vrfKey
+          praosCanBeLeaderSignKeyVRF = vrfKey,
+          praosCanBeLeaderCredentialsSource = PraosCredentialsUnsound opcert kesKey
         },
-      shelleyLeaderCredentialsInitSignKey = kesKey,
       shelleyLeaderCredentialsLabel = "Shelley"
     }
 
diff --git a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Tools/DBSynthesizer/Run.hs b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Tools/DBSynthesizer/Run.hs
index cc88fbd694..1a7e18addd 100644
--- a/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Tools/DBSynthesizer/Run.hs
+++ b/ouroboros-consensus-cardano/src/unstable-cardano-tools/Cardano/Tools/DBSynthesizer/Run.hs
@@ -23,6 +23,7 @@ import           Data.Aeson as Aeson (FromJSON, Result (..), Value,
 import           Data.Bool (bool)
 import           Data.ByteString as BS (ByteString, readFile)
 import qualified Data.Set as Set
+import qualified Ouroboros.Consensus.Block.Forging as BlockForging
 import           Ouroboros.Consensus.Cardano.Block
 import           Ouroboros.Consensus.Cardano.Node
 import           Ouroboros.Consensus.Config (TopLevelConfig, configStorage)
@@ -134,7 +135,7 @@ synthesize genTxs DBSynthesizerConfig{confOptions, confShelleyGenesis, confDbDir
               (Node.stdMkChainDbHasFS confDbDir)
               $ ChainDB.defaultArgs
 
-        forgers <- blockForging
+        (_, forgers) <- allocate registry (const $ mkForgers) (mapM_ BlockForging.finalize)
         let fCount = length forgers
         putStrLn $ "--> forger count: " ++ show fCount
         if fCount > 0
@@ -163,9 +164,10 @@ synthesize genTxs DBSynthesizerConfig{confOptions, confShelleyGenesis, confDbDir
         { pInfoConfig
         , pInfoInitLedger
         }
-      , blockForging
+      , mkForgers
       ) = protocolInfoCardano runP
 
+
 preOpenChainDB :: DBSynthesizerOpenMode -> FilePath -> IO ()
 preOpenChainDB mode db =
     doesDirectoryExist db >>= bool create checkMode
diff --git a/ouroboros-consensus-cardano/src/unstable-shelley-testlib/Test/Consensus/Shelley/MockCrypto.hs b/ouroboros-consensus-cardano/src/unstable-shelley-testlib/Test/Consensus/Shelley/MockCrypto.hs
index c438a4f38e..9489f662ac 100644
--- a/ouroboros-consensus-cardano/src/unstable-shelley-testlib/Test/Consensus/Shelley/MockCrypto.hs
+++ b/ouroboros-consensus-cardano/src/unstable-shelley-testlib/Test/Consensus/Shelley/MockCrypto.hs
@@ -4,6 +4,7 @@
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE OverloadedStrings #-}
 
 {-# OPTIONS_GHC -Wno-orphans #-}
 
@@ -27,12 +28,16 @@ import           Control.State.Transition.Extended (PredicateFailure)
 import           Ouroboros.Consensus.Ledger.SupportsProtocol
                      (LedgerSupportsProtocol)
 import qualified Ouroboros.Consensus.Protocol.Praos as Praos
+import           Ouroboros.Consensus.Protocol.Praos.AgentClient (AgentCrypto (..))
 import           Ouroboros.Consensus.Protocol.TPraos (TPraos)
 import           Ouroboros.Consensus.Shelley.Eras (EraCrypto, ShelleyEra)
 import           Ouroboros.Consensus.Shelley.Ledger (ShelleyBlock,
                      ShelleyCompatible)
 import qualified Test.Cardano.Ledger.Shelley.ConcreteCryptoTypes as SL (Mock)
 import           Test.QuickCheck (Arbitrary)
+import qualified Cardano.KESAgent.KES.Crypto as Agent
+import qualified Cardano.KESAgent.Protocols.VersionedProtocol as Agent
+import qualified Cardano.KESAgent.Processes.ServiceClient as Agent
 
 -- | A mock replacement for 'StandardCrypto'
 --
@@ -76,3 +81,16 @@ type CanMock proto era =
   , Arbitrary (StashedAVVMAddresses era)
   , Arbitrary (Core.GovState era)
   )
+
+instance Agent.NamedCrypto (MockCrypto h) where
+  cryptoName _ = Agent.CryptoName "Mock"
+
+instance Agent.ServiceClientDrivers (MockCrypto h) where
+  availableServiceClientDrivers = []
+
+instance Agent.Crypto (MockCrypto h) where
+  type KES (MockCrypto h) = MockKES 10
+  type DSIGN (MockCrypto h) = MockDSIGN
+
+instance HashAlgorithm h => AgentCrypto (MockCrypto h) where
+  type ACrypto (MockCrypto h) = MockCrypto h
diff --git a/ouroboros-consensus-cardano/src/unstable-shelley-testlib/Test/ThreadNet/Infra/Shelley.hs b/ouroboros-consensus-cardano/src/unstable-shelley-testlib/Test/ThreadNet/Infra/Shelley.hs
index b67594b964..ac524d06fa 100644
--- a/ouroboros-consensus-cardano/src/unstable-shelley-testlib/Test/ThreadNet/Infra/Shelley.hs
+++ b/ouroboros-consensus-cardano/src/unstable-shelley-testlib/Test/ThreadNet/Infra/Shelley.hs
@@ -37,7 +37,9 @@ module Test.ThreadNet.Infra.Shelley (
 
 import           Cardano.Crypto.DSIGN (DSIGNAlgorithm (..), seedSizeDSIGN)
 import           Cardano.Crypto.Hash (HashAlgorithm)
-import           Cardano.Crypto.KES (KESAlgorithm (..))
+import           Cardano.Crypto.KES (UnsoundPureSignKeyKES, KESAlgorithm (..),
+                     UnsoundPureKESAlgorithm (..),
+                     seedSizeKES, unsoundPureGenKeyKES, unsoundPureDeriveVerKeyKES)
 import           Cardano.Crypto.Seed (mkSeedFromBytes)
 import qualified Cardano.Crypto.Seed as Cardano.Crypto
 import           Cardano.Crypto.VRF (SignKeyVRF, deriveVerKeyVRF, genKeyVRF,
@@ -78,8 +80,10 @@ import           Ouroboros.Consensus.Config.SecurityParam
 import           Ouroboros.Consensus.Node.ProtocolInfo
 import           Ouroboros.Consensus.Protocol.Praos.Common
                      (PraosCanBeLeader (PraosCanBeLeader),
-                     praosCanBeLeaderColdVerKey, praosCanBeLeaderOpCert,
-                     praosCanBeLeaderSignKeyVRF)
+                     praosCanBeLeaderColdVerKey,
+                     praosCanBeLeaderSignKeyVRF,
+                     praosCanBeLeaderCredentialsSource,
+                     PraosCredentialsSource (..))
 import           Ouroboros.Consensus.Protocol.TPraos
 import           Ouroboros.Consensus.Shelley.Eras (EraCrypto, ShelleyEra)
 import           Ouroboros.Consensus.Shelley.Ledger (GenTx (..),
@@ -87,7 +91,6 @@ import           Ouroboros.Consensus.Shelley.Ledger (GenTx (..),
                      mkShelleyTx)
 import           Ouroboros.Consensus.Shelley.Node
 import           Ouroboros.Consensus.Util.Assert
-import           Ouroboros.Consensus.Util.IOLike
 import           Quiet (Quiet (..))
 import qualified Test.Cardano.Ledger.Core.KeyPair as TL (KeyPair (..),
                      mkWitnessesVKey)
@@ -97,6 +100,7 @@ import           Test.QuickCheck
 import           Test.Util.Orphans.Arbitrary ()
 import           Test.Util.Slots (NumSlots (..))
 import           Test.Util.Time (dawnOfTime)
+import           Ouroboros.Consensus.Protocol.Praos.AgentClient (KESAgentContext)
 
 {-------------------------------------------------------------------------------
   The decentralization parameter
@@ -138,7 +142,7 @@ data CoreNode c = CoreNode {
       -- ^ The hash of the corresponding verification (public) key will be
       -- used as the staking credential.
     , cnVRF         :: !(SL.SignKeyVRF   c)
-    , cnKES         :: !(SL.SignKeyKES   c)
+    , cnKES         :: !(UnsoundPureSignKeyKES (KES c))
     , cnOCert       :: !(SL.OCert        c)
     }
 
@@ -180,8 +184,8 @@ genCoreNode startKESPeriod = do
     delKey <- genKeyDSIGN <$> genSeed (seedSizeDSIGN (Proxy @(DSIGN c)))
     stkKey <- genKeyDSIGN <$> genSeed (seedSizeDSIGN (Proxy @(DSIGN c)))
     vrfKey <- genKeyVRF   <$> genSeed (seedSizeVRF   (Proxy @(VRF   c)))
-    kesKey <- genKeyKES   <$> genSeed (seedSizeKES   (Proxy @(KES   c)))
-    let kesPub = deriveVerKeyKES kesKey
+    kesKey <- unsoundPureGenKeyKES <$> genSeed (seedSizeKES   (Proxy @(KES   c)))
+    let kesPub = unsoundPureDeriveVerKeyKES kesKey
         sigma  = LK.signedDSIGN
           @c
           delKey
@@ -212,9 +216,8 @@ genCoreNode startKESPeriod = do
 mkLeaderCredentials :: PraosCrypto c => CoreNode c -> ShelleyLeaderCredentials c
 mkLeaderCredentials CoreNode { cnDelegateKey, cnVRF, cnKES, cnOCert } =
     ShelleyLeaderCredentials {
-        shelleyLeaderCredentialsInitSignKey = cnKES
-      , shelleyLeaderCredentialsCanBeLeader = PraosCanBeLeader {
-          praosCanBeLeaderOpCert     = cnOCert
+        shelleyLeaderCredentialsCanBeLeader = PraosCanBeLeader {
+          praosCanBeLeaderCredentialsSource = PraosCredentialsUnsound cnOCert cnKES
         , praosCanBeLeaderColdVerKey = SL.VKey $ deriveVerKeyDSIGN cnDelegateKey
         , praosCanBeLeaderSignKeyVRF = cnVRF
         }
@@ -405,7 +408,10 @@ mkGenesisConfig pVer k f d maxLovelaceSupply slotLength kesCfg coreNodes =
 
 mkProtocolShelley ::
      forall m c.
-     (IOLike m, PraosCrypto c, ShelleyCompatible (TPraos c) (ShelleyEra c))
+     ( KESAgentContext c m
+     , PraosCrypto c
+     , ShelleyCompatible (TPraos c) (ShelleyEra c)
+     )
   => ShelleyGenesis c
   -> SL.Nonce
   -> ProtVer
@@ -421,6 +427,7 @@ mkProtocolShelley genesis initialNonce protVer coreNode =
         , shelleyBasedLeaderCredentials = [mkLeaderCredentials coreNode]
         }
       protVer
+
 {-------------------------------------------------------------------------------
   Necessary transactions for updating the 'DecentralizationParam'
 -------------------------------------------------------------------------------}
diff --git a/ouroboros-consensus-cardano/test/cardano-test/Test/ThreadNet/Cardano.hs b/ouroboros-consensus-cardano/test/cardano-test/Test/ThreadNet/Cardano.hs
index f0dccc8304..58ca2487cb 100644
--- a/ouroboros-consensus-cardano/test/cardano-test/Test/ThreadNet/Cardano.hs
+++ b/ouroboros-consensus-cardano/test/cardano-test/Test/ThreadNet/Cardano.hs
@@ -51,9 +51,9 @@ import           Ouroboros.Consensus.Node.NetworkProtocolVersion
 import           Ouroboros.Consensus.Node.ProtocolInfo
 import           Ouroboros.Consensus.NodeId
 import           Ouroboros.Consensus.Protocol.PBFT
+import           Ouroboros.Consensus.Protocol.Praos.AgentClient (KESAgentContext)
 import           Ouroboros.Consensus.Shelley.Ledger.SupportsProtocol ()
 import           Ouroboros.Consensus.Shelley.Node
-import           Ouroboros.Consensus.Util.IOLike (IOLike)
 import           Test.Consensus.Cardano.ProtocolInfo
                      (hardForkOnDefaultProtocolVersions, mkTestProtocolInfo)
 import           Test.QuickCheck
@@ -434,7 +434,7 @@ prop_simple_cardano_convergence TestSetup
         property $ maxRollbacks setupK >= finalIntersectionDepth
 
 mkProtocolCardanoAndHardForkTxs ::
-     forall c m. (IOLike m, c ~ StandardCrypto)
+     forall c m. (KESAgentContext c m, c ~ StandardCrypto)
      -- Byron
   => PBftParams
   -> CoreNodeId
diff --git a/ouroboros-consensus-diffusion/changelog.d/20250130_100651_tdammers_mlocked_kes_rebase.md b/ouroboros-consensus-diffusion/changelog.d/20250130_100651_tdammers_mlocked_kes_rebase.md
new file mode 100644
index 0000000000..44c5f98e69
--- /dev/null
+++ b/ouroboros-consensus-diffusion/changelog.d/20250130_100651_tdammers_mlocked_kes_rebase.md
@@ -0,0 +1,3 @@
+### Non-Breaking
+
+- Ensure that block forging threads finalize their keys when shutting down.
diff --git a/ouroboros-consensus-diffusion/ouroboros-consensus-diffusion.cabal b/ouroboros-consensus-diffusion/ouroboros-consensus-diffusion.cabal
index a765dfacc7..022c6b776e 100644
--- a/ouroboros-consensus-diffusion/ouroboros-consensus-diffusion.cabal
+++ b/ouroboros-consensus-diffusion/ouroboros-consensus-diffusion.cabal
@@ -91,6 +91,7 @@ library
     mtl,
     network-mux ^>=0.6,
     ouroboros-consensus ^>=0.22,
+    ouroboros-consensus-protocol ^>=0.10,
     ouroboros-network ^>=0.19.0.2,
     ouroboros-network-api ^>=0.12,
     ouroboros-network-framework ^>=0.16,
@@ -143,6 +144,7 @@ library unstable-diffusion-testlib
     io-sim,
     mtl,
     ouroboros-consensus:{ouroboros-consensus, unstable-consensus-testlib},
+    ouroboros-consensus-protocol,
     ouroboros-consensus-diffusion,
     ouroboros-network,
     ouroboros-network-api,
@@ -174,8 +176,8 @@ library unstable-mock-testlib
     QuickCheck,
     base,
     bytestring,
-    cardano-crypto-class,
-    cardano-crypto-tests,
+    cardano-crypto-class ^>= 2.2,
+    cardano-crypto-tests ^>= 2.2,
     containers,
     ouroboros-consensus:{ouroboros-consensus, unstable-consensus-testlib, unstable-mock-block},
     ouroboros-network-protocols:testlib,
@@ -281,7 +283,7 @@ test-suite consensus-test
     base,
     binary,
     bytestring,
-    cardano-crypto-class,
+    cardano-crypto-class ^>= 2.2,
     cardano-slotting:{cardano-slotting, testlib},
     cardano-strict-containers,
     containers,
diff --git a/ouroboros-consensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/Node/Tracers.hs b/ouroboros-consensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/Node/Tracers.hs
index 9b5a6eb8db..31da10d2b8 100644
--- a/ouroboros-consensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/Node/Tracers.hs
+++ b/ouroboros-consensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/Node/Tracers.hs
@@ -38,6 +38,7 @@ import           Ouroboros.Consensus.MiniProtocol.ChainSync.Server
 import           Ouroboros.Consensus.MiniProtocol.LocalTxSubmission.Server
                      (TraceLocalTxSubmissionServerEvent (..))
 import           Ouroboros.Consensus.Node.GSM (TraceGsmEvent)
+import           Ouroboros.Consensus.Protocol.Praos.AgentClient (KESAgentClientTrace (..))
 import           Ouroboros.Network.Block (Tip)
 import           Ouroboros.Network.BlockFetch (TraceFetchClientState,
                      TraceLabelPeer)
@@ -74,6 +75,7 @@ data Tracers' remotePeer localPeer blk f = Tracers
   , gddTracer                     :: f (TraceGDDEvent remotePeer blk)
   , csjTracer                     :: f (TraceLabelPeer remotePeer (CSJumping.TraceEventCsj remotePeer blk))
   , dbfTracer                     :: f (CSJumping.TraceEventDbf remotePeer)
+  , kesAgentTracer                :: f KESAgentClientTrace
   }
 
 instance (forall a. Semigroup (f a))
@@ -99,6 +101,7 @@ instance (forall a. Semigroup (f a))
       , gddTracer                     = f gddTracer
       , csjTracer                     = f csjTracer
       , dbfTracer                     = f dbfTracer
+      , kesAgentTracer                = f kesAgentTracer
       }
     where
       f :: forall a. Semigroup a
@@ -132,6 +135,7 @@ nullTracers = Tracers
     , gddTracer                     = nullTracer
     , csjTracer                     = nullTracer
     , dbfTracer                     = nullTracer
+    , kesAgentTracer                = nullTracer
     }
 
 showTracers :: ( Show blk
@@ -168,6 +172,7 @@ showTracers tr = Tracers
     , gddTracer                     = showTracing tr
     , csjTracer                     = showTracing tr
     , dbfTracer                     = showTracing tr
+    , kesAgentTracer                = showTracing tr
     }
 
 {-------------------------------------------------------------------------------
diff --git a/ouroboros-consensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/NodeKernel.hs b/ouroboros-consensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/NodeKernel.hs
index 7f1396e82a..f9a4b96c39 100644
--- a/ouroboros-consensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/NodeKernel.hs
+++ b/ouroboros-consensus-diffusion/src/ouroboros-consensus-diffusion/Ouroboros/Consensus/NodeKernel.hs
@@ -435,10 +435,13 @@ forkBlockForging ::
     -> BlockForging m blk
     -> m (Thread m Void)
 forkBlockForging IS{..} blockForging =
-    forkLinkedWatcher registry threadLabel
-    $ knownSlotWatcher btime
-    $ withEarlyExit_ . go
+    forkLinkedWatcherFinalize registry threadLabel
+      watcher
+      (finalize blockForging)
   where
+    watcher :: Watcher m SlotNo SlotNo
+    watcher = knownSlotWatcher btime $ withEarlyExit_ . go
+
     threadLabel :: String
     threadLabel =
         "NodeKernel.blockForging." <> Text.unpack (forgeLabel blockForging)
diff --git a/ouroboros-consensus-diffusion/src/unstable-diffusion-testlib/Test/ThreadNet/General.hs b/ouroboros-consensus-diffusion/src/unstable-diffusion-testlib/Test/ThreadNet/General.hs
index 95008ef9ef..0b5f3ff783 100644
--- a/ouroboros-consensus-diffusion/src/unstable-diffusion-testlib/Test/ThreadNet/General.hs
+++ b/ouroboros-consensus-diffusion/src/unstable-diffusion-testlib/Test/ThreadNet/General.hs
@@ -52,13 +52,14 @@ import           Ouroboros.Consensus.Node.Run
 import           Ouroboros.Consensus.NodeId
 import           Ouroboros.Consensus.Protocol.Abstract (LedgerView)
 import           Ouroboros.Consensus.Protocol.LeaderSchedule
+import           Ouroboros.Consensus.Protocol.Praos.AgentClient (MonadKESAgent)
 import qualified Ouroboros.Consensus.Storage.ChainDB as ChainDB
 import           Ouroboros.Consensus.TypeFamilyWrappers
 import           Ouroboros.Consensus.Util.Condense
 import           Ouroboros.Consensus.Util.Enclose (pattern FallingEdge)
-import           Ouroboros.Consensus.Util.IOLike
 import           Ouroboros.Consensus.Util.Orphans ()
 import           Ouroboros.Consensus.Util.RedundantConstraints
+import           Ouroboros.Consensus.Util.IOLike
 import qualified Ouroboros.Network.Mock.Chain as MockChain
 import qualified System.FS.Sim.MockFS as Mock
 import           System.FS.Sim.MockFS (MockFS)
@@ -206,7 +207,7 @@ runTestNetwork ::
      )
   => TestConfig
   -> TestConfigB blk
-  -> (forall m. IOLike m => TestConfigMB m blk)
+  -> (forall m. (IOLike m, MonadKESAgent m) => TestConfigMB m blk)
   -> TestOutput blk
 runTestNetwork TestConfig
   { numCoreNodes
diff --git a/ouroboros-consensus-diffusion/src/unstable-diffusion-testlib/Test/ThreadNet/Network.hs b/ouroboros-consensus-diffusion/src/unstable-diffusion-testlib/Test/ThreadNet/Network.hs
index d7dd9e75cc..0e39141e9b 100644
--- a/ouroboros-consensus-diffusion/src/unstable-diffusion-testlib/Test/ThreadNet/Network.hs
+++ b/ouroboros-consensus-diffusion/src/unstable-diffusion-testlib/Test/ThreadNet/Network.hs
@@ -63,6 +63,7 @@ import           Network.TypedProtocol.Codec (AnyMessage (..), CodecFailure,
                      mapFailureCodec)
 import qualified Network.TypedProtocol.Codec as Codec
 import           Ouroboros.Consensus.Block
+import qualified Ouroboros.Consensus.Block.Forging as BlockForging
 import           Ouroboros.Consensus.BlockchainTime
 import           Ouroboros.Consensus.Config
 import           Ouroboros.Consensus.Ledger.Abstract
@@ -802,7 +803,7 @@ runThreadNetwork systemTime ThreadNetworkArgs
       -> m ( NodeKernel m NodeId Void blk
            , LimitedApp m NodeId      blk
            )
-    forkNode coreNodeId clock joinSlot registry pInfo blockForging nodeInfo txs0 = do
+    forkNode coreNodeId clock joinSlot registry pInfo mkBlockForging nodeInfo txs0 = do
       let ProtocolInfo{..} = pInfo
 
       let NodeInfo
@@ -1042,9 +1043,9 @@ runThreadNetwork systemTime ThreadNetworkArgs
 
       nodeKernel <- initNodeKernel nodeKernelArgs
 
-      blockForging' <-
-            map (\bf -> bf { forgeBlock = customForgeBlock bf })
-        <$> blockForging
+      (_, blockForging) <- allocate registry (const mkBlockForging) (mapM_ BlockForging.finalize)
+      let blockForging' =
+            map (\bf -> bf { forgeBlock = customForgeBlock bf }) blockForging
       setBlockForging nodeKernel blockForging'
 
       let mempool = getMempool nodeKernel
diff --git a/ouroboros-consensus-diffusion/test/consensus-test/Test/Consensus/HardFork/Combinator/A.hs b/ouroboros-consensus-diffusion/test/consensus-test/Test/Consensus/HardFork/Combinator/A.hs
index 4aa3b65074..6155b3fcb5 100644
--- a/ouroboros-consensus-diffusion/test/consensus-test/Test/Consensus/HardFork/Combinator/A.hs
+++ b/ouroboros-consensus-diffusion/test/consensus-test/Test/Consensus/HardFork/Combinator/A.hs
@@ -292,6 +292,7 @@ blockForgingA = BlockForging {
    , checkCanForge    = \_ _ _ _ _ -> return ()
    , forgeBlock       = \cfg bno slot st txs proof -> return $
        forgeBlockA cfg bno slot st (fmap txForgetValidated txs) proof
+   , finalize = return ()
    }
 
 -- | See 'Ouroboros.Consensus.HardFork.History.EraParams.safeFromTip'
diff --git a/ouroboros-consensus-diffusion/test/consensus-test/Test/Consensus/HardFork/Combinator/B.hs b/ouroboros-consensus-diffusion/test/consensus-test/Test/Consensus/HardFork/Combinator/B.hs
index 7c45c64137..e58145554a 100644
--- a/ouroboros-consensus-diffusion/test/consensus-test/Test/Consensus/HardFork/Combinator/B.hs
+++ b/ouroboros-consensus-diffusion/test/consensus-test/Test/Consensus/HardFork/Combinator/B.hs
@@ -240,6 +240,7 @@ blockForgingB = BlockForging {
    , checkCanForge    = \_ _ _ _ _ -> return ()
    , forgeBlock       = \cfg bno slot st txs proof -> return $
        forgeBlockB cfg bno slot st (fmap txForgetValidated txs) proof
+   , finalize = return ()
    }
 
 -- | A basic 'History.SafeZone'
diff --git a/ouroboros-consensus-diffusion/test/mock-test/Test/ThreadNet/Praos.hs b/ouroboros-consensus-diffusion/test/mock-test/Test/ThreadNet/Praos.hs
index d65cddcc3a..35b3883722 100644
--- a/ouroboros-consensus-diffusion/test/mock-test/Test/ThreadNet/Praos.hs
+++ b/ouroboros-consensus-diffusion/test/mock-test/Test/ThreadNet/Praos.hs
@@ -49,7 +49,7 @@ data TestSetup = TestSetup
 
 genEvolvingStake :: EpochSize -> TestConfig -> Gen PraosEvolvingStake
 genEvolvingStake epochSize TestConfig {numSlots, numCoreNodes} = do
-    chosenEpochs <- sublistOf [0..EpochNo $ max 1 maxEpochs - 1]
+    chosenEpochs <- sublistOf [EpochNo 0..EpochNo $ max 1 maxEpochs - 1]
     let l = fromIntegral maxEpochs
     stakeDists <- replicateM l genStakeDist
     return . PraosEvolvingStake . Map.fromList $ zip chosenEpochs stakeDists
diff --git a/ouroboros-consensus-protocol/changelog.d/20250130_101128_tdammers_mlocked_kes_rebase.md b/ouroboros-consensus-protocol/changelog.d/20250130_101128_tdammers_mlocked_kes_rebase.md
new file mode 100644
index 0000000000..804067168e
--- /dev/null
+++ b/ouroboros-consensus-protocol/changelog.d/20250130_101128_tdammers_mlocked_kes_rebase.md
@@ -0,0 +1,18 @@
+### Breaking
+
+- Use new mlocked KES API for all internal KES sign key handling.
+- Add finalizers to all block forgings (required by `ouroboros-consensus`).
+- Change `HotKey` to manage not only KES sign keys, but also the corresponding
+  OpCerts. This is in preparation for KES agent connectivity: with the new
+  design, the KES agent will provide both KES sign keys and matching OpCerts
+  together, and we need to be able to dynamically replace them both together.
+- Add finalizer to `HotKey`. This takes care of securely forgetting any KES
+  keys the HotKey may still hold, and will be called automatically when the
+  owning block forging terminates.
+- Change `PraosCanBeLeader` to not contain the KES sign key itself anymore.
+  Instead, it now contains a `PraosCredentialsSource` field, which
+  specifies how to obtain the actual credentials (OpCert and KES SignKey). For
+  now, the only supported method is passing an OpCert and an
+  UnsoundPureSignKeyKES, presumably loaded from disk
+  (`PraosCredentialsUnsound`); future iterations will add support for
+  connecting to a KES agent.
diff --git a/ouroboros-consensus-protocol/ouroboros-consensus-protocol.cabal b/ouroboros-consensus-protocol/ouroboros-consensus-protocol.cabal
index 9725c76e0b..e7a1be7396 100644
--- a/ouroboros-consensus-protocol/ouroboros-consensus-protocol.cabal
+++ b/ouroboros-consensus-protocol/ouroboros-consensus-protocol.cabal
@@ -57,6 +57,7 @@ library
     Ouroboros.Consensus.Protocol.Ledger.Util
     Ouroboros.Consensus.Protocol.Praos
     Ouroboros.Consensus.Protocol.Praos.Common
+    Ouroboros.Consensus.Protocol.Praos.AgentClient
     Ouroboros.Consensus.Protocol.Praos.Header
     Ouroboros.Consensus.Protocol.Praos.VRF
     Ouroboros.Consensus.Protocol.Praos.Views
@@ -66,7 +67,7 @@ library
     base >=4.14 && <4.21,
     bytestring,
     cardano-binary,
-    cardano-crypto-class,
+    cardano-crypto-class ^>= 2.2,
     cardano-ledger-binary,
     cardano-ledger-core,
     cardano-ledger-shelley,
@@ -74,11 +75,20 @@ library
     cardano-slotting,
     cborg,
     containers,
+    contra-tracer ^>=0.1.0,
+    io-classes ^>=1.5.0,
+    io-sim,
+    kes-agent,
     mtl,
+    network ^>=3.1.4.0,
     nothunks,
     ouroboros-consensus ^>=0.22,
+    ouroboros-network-framework ^>=0.16,
+    ouroboros-network-testing ^>=0.8,
     serialise,
+    serdoc-core,
     text,
+    Win32-network ^>=0.2,
 
 library unstable-protocol-testlib
   import: common-lib
@@ -94,9 +104,9 @@ library unstable-protocol-testlib
     base,
     base16-bytestring,
     bytestring,
-    cardano-crypto-class,
-    cardano-crypto-praos,
-    cardano-crypto-tests,
+    cardano-crypto-class ^>= 2.2,
+    cardano-crypto-praos ^>= 2.2,
+    cardano-crypto-tests ^>= 2.2,
     cardano-ledger-binary,
     cardano-ledger-core,
     cardano-ledger-shelley-test,
@@ -117,9 +127,9 @@ test-suite protocol-test
   build-depends:
     QuickCheck,
     base,
-    cardano-crypto-class,
+    cardano-crypto-class ^>= 2.2,
     cardano-ledger-binary:testlib,
-    cardano-ledger-core ^>=1.16,
+    cardano-ledger-core ^>=1.17,
     containers,
     ouroboros-consensus:{ouroboros-consensus, unstable-consensus-testlib},
     ouroboros-consensus-protocol,
diff --git a/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Ledger/HotKey.hs b/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Ledger/HotKey.hs
index 8a46088450..3878dfb826 100644
--- a/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Ledger/HotKey.hs
+++ b/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Ledger/HotKey.hs
@@ -1,9 +1,13 @@
 {-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE DataKinds #-}
 {-# LANGUAGE DeriveAnyClass #-}
 {-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE DerivingVia #-}
+{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE NamedFieldPuns #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE StandaloneDeriving #-}
 
 -- | Hot key
 --
@@ -18,21 +22,29 @@ module Ouroboros.Consensus.Protocol.Ledger.HotKey (
   , kesStatus
     -- * Hot Key
   , HotKey (..)
+  , finalize
+  , getOCert
   , KESEvolutionError (..)
   , KESEvolutionInfo
   , mkHotKey
+  , mkHotKeyAtEvolution
+  , mkEmptyHotKey
+  , mkDynamicHotKey
   , sign
   ) where
 
 import qualified Cardano.Crypto.KES as Relative (Period)
-import           Cardano.Ledger.Crypto (Crypto)
+import           Cardano.Ledger.Crypto (Crypto (..))
 import qualified Cardano.Ledger.Keys as SL
+import qualified Cardano.Protocol.TPraos.OCert as OCert
 import qualified Cardano.Protocol.TPraos.OCert as Absolute (KESPeriod (..))
 import           Data.Word (Word64)
 import           GHC.Generics (Generic)
 import           GHC.Stack (HasCallStack)
 import           Ouroboros.Consensus.Block.Forging (UpdateInfo (..))
 import           Ouroboros.Consensus.Util.IOLike
+import           NoThunks.Class (OnlyCheckWhnfNamed (..))
+import           Control.Monad (forM_)
 
 {-------------------------------------------------------------------------------
   KES Info
@@ -126,19 +138,52 @@ data HotKey c m = HotKey {
       --
       -- When the key cannot evolve anymore, we poison it.
       evolve     :: Absolute.KESPeriod -> m KESEvolutionInfo
+
       -- | Return 'KESInfo' of the signing key.
     , getInfo    :: m KESInfo
-      -- | Return 'True' when the signing key is poisoned because it expired.
+
+      -- | Return the 'OCert' corresponding to the KES signing key, if any.
+    , getOCertMaybe :: m (Maybe (OCert.OCert c))
+
+      -- | Check whether a valid KES signing key exists. "Poisoned" means no
+      -- key exists; reasons for this could be:
+      -- - no signing key has been set yet
+      -- - the signing key has been explicitly erased ('forget')
+      -- - the signing key has been evolved past the end of the available
+      --   evolutions
     , isPoisoned :: m Bool
+
       -- | Sign the given @toSign@ with the current signing key.
       --
       -- PRECONDITION: the key is not poisoned.
       --
       -- POSTCONDITION: the signature is in normal form.
     , sign_      :: forall toSign. (SL.KESignable c toSign, HasCallStack)
-                 => toSign -> m (SL.SignedKES c toSign)
+                 => toSign
+                 -> m (SL.SignedKES c toSign)
+
+      -- | Securely erase the key and release its memory.
+    , forget :: m ()
+
+      -- | Release any resources held by the 'HotKey', except for the signing
+      -- key itself. User code should use 'finalize' instead.
+    , finalize_ :: m ()
     }
 
+-- | Release all resources held by the 'HotKey', including the signing key
+-- itself. Use this exactly once per 'HotKey' instance.
+finalize :: Monad m => HotKey c m -> m ()
+finalize hotKey = forget hotKey >> finalize_ hotKey
+
+deriving via (OnlyCheckWhnfNamed "HotKey" (HotKey c m)) instance NoThunks (HotKey c m)
+
+getOCert :: Monad m => HotKey c m -> m (OCert.OCert c)
+getOCert hotKey = do
+  ocertMay <- getOCertMaybe hotKey
+  case ocertMay of
+    Just ocert -> return ocert
+    Nothing -> error "trying to read OpCert for poisoned key"
+
 sign ::
      (SL.KESignable c toSign, HasCallStack)
   => HotKey c m
@@ -148,7 +193,7 @@ sign = sign_
 -- | The actual KES key, unless it expired, in which case it is replaced by
 -- \"poison\".
 data KESKey c =
-    KESKey !(SL.SignKeyKES c)
+    KESKey !(OCert.OCert c) !(SL.SignKeyKES c)
   | KESKeyPoisoned
   deriving (Generic)
 
@@ -156,7 +201,7 @@ instance Crypto c => NoThunks (KESKey c)
 
 kesKeyIsPoisoned :: KESKey c -> Bool
 kesKeyIsPoisoned KESKeyPoisoned = True
-kesKeyIsPoisoned (KESKey _)     = False
+kesKeyIsPoisoned (KESKey _ _)     = False
 
 data KESState c = KESState {
       kesStateInfo :: !KESInfo
@@ -166,42 +211,145 @@ data KESState c = KESState {
 
 instance Crypto c => NoThunks (KESState c)
 
+-- Create a new 'HotKey' and initialize it to the given initial KES key. The
+-- initial key must be at evolution 0 (i.e., freshly generated and never
+-- evolved).
 mkHotKey ::
      forall m c. (Crypto c, IOLike m)
-  => SL.SignKeyKES c
+  => OCert.OCert c
+  -> SL.SignKeyKES c
   -> Absolute.KESPeriod  -- ^ Start period
   -> Word64              -- ^ Max KES evolutions
   -> m (HotKey c m)
-mkHotKey initKey startPeriod@(Absolute.KESPeriod start) maxKESEvolutions = do
+mkHotKey = mkHotKeyAtEvolution 0
+
+-- Create a new 'HotKey' and initialize it to the given initial KES key. The
+-- initial key should be at the given evolution.
+mkHotKeyAtEvolution ::
+     forall m c. (Crypto c, IOLike m)
+  => Word
+  -> OCert.OCert c
+  -> SL.SignKeyKES c
+  -> Absolute.KESPeriod  -- ^ Start period
+  -> Word64              -- ^ Max KES evolutions
+  -> m (HotKey c m)
+mkHotKeyAtEvolution evolution ocert initKey startPeriod maxKESEvolutions =
+  mkHotKeyWith
+    (Just (ocert, initKey, evolution, startPeriod))
+    maxKESEvolutions
+    Nothing
+    (pure ())
+
+-- | Create a new 'HotKey' and initialize it to a poisoned state (containing no
+-- valid KES sign key).
+mkEmptyHotKey ::
+     forall m c. (Crypto c, IOLike m)
+  => Word64              -- ^ Max KES evolutions
+  -> m ()
+  -> m (HotKey c m)
+mkEmptyHotKey maxKESEvolutions =
+  mkDynamicHotKey maxKESEvolutions Nothing
+
+mkKESState :: Word64 -> OCert.OCert c -> SL.SignKeyKES c -> Word -> Absolute.KESPeriod -> KESState c
+mkKESState maxKESEvolutions newOCert newKey evolution startPeriod@(Absolute.KESPeriod start) =
+    KESState {
+      kesStateInfo = KESInfo {
+          kesStartPeriod = startPeriod
+        , kesEndPeriod   = Absolute.KESPeriod (start + fromIntegral maxKESEvolutions)
+        , kesEvolution   = evolution
+      }
+      , kesStateKey = KESKey newOCert newKey
+    }
+
+-- | Create a new 'HotKey' that runs a key-producer action on a separate thread.
+-- The key producer action will receive a callback that can be used to pass
+-- keys into the HotKey; the HotKey will dynamically update its internal state
+-- to reflect new keys as they arrive.
+mkDynamicHotKey ::
+     forall m c. (Crypto c, IOLike m)
+  => Word64              -- ^ Max KES evolutions
+  -> Maybe (
+        (OCert.OCert c -> SL.SignKeyKES c -> Word -> Absolute.KESPeriod -> m ())
+        -> m ()
+     )
+  -> m ()
+  -> m (HotKey c m)
+mkDynamicHotKey = mkHotKeyWith Nothing
+
+-- | The most general function for creating a new 'HotKey', accepting an initial
+-- set of credentials, a key producer action, and a custom finalizer.
+mkHotKeyWith ::
+     forall m c. (Crypto c, IOLike m)
+  => Maybe (OCert.OCert c, SL.SignKeyKES c, Word, Absolute.KESPeriod)
+  -> Word64              -- ^ Max KES evolutions
+  -> Maybe (
+        (OCert.OCert c -> SL.SignKeyKES c -> Word -> Absolute.KESPeriod -> m ())
+        -> m ()
+     )
+  -> m ()
+  -> m (HotKey c m)
+mkHotKeyWith initialStateMay maxKESEvolutions keyThreadMay finalizer = do
     varKESState <- newMVar initKESState
+
+    let set newOCert newKey evolution startPeriod =
+          modifyMVar_ varKESState $ \oldState -> do
+            _ <- poisonState oldState
+            return $ mkKESState maxKESEvolutions newOCert newKey evolution startPeriod
+
+    forM_ initialStateMay $ \(newOCert, newKey, evolution, startPeriod) ->
+            set newOCert newKey evolution startPeriod
+
+    finalizer' <- case keyThreadMay of
+      Just keyThread -> do
+        keyThreadAsync <- async $ do
+                            labelThisThread "HotKey receiver"
+                            keyThread set
+        return (cancel keyThreadAsync >> finalizer)
+      Nothing ->
+        return finalizer
+
     return HotKey {
         evolve     = evolveKey varKESState
       , getInfo    = kesStateInfo <$> readMVar varKESState
+      , getOCertMaybe   = kesStateKey <$> readMVar varKESState >>= \case
+                            KESKeyPoisoned -> return Nothing
+                            KESKey ocert _ -> return (Just ocert)
+
       , isPoisoned = kesKeyIsPoisoned . kesStateKey <$> readMVar varKESState
       , sign_      = \toSign -> do
-          KESState { kesStateInfo, kesStateKey } <- readMVar varKESState
-          case kesStateKey of
-            KESKeyPoisoned -> error "trying to sign with a poisoned key"
-            KESKey key     -> do
-              let evolution = kesEvolution kesStateInfo
-                  signed    = SL.signedKES () evolution toSign key
-              -- Force the signature to WHNF (for 'SignedKES', WHNF implies
-              -- NF) so that we don't have any thunks holding on to a key that
-              -- might be destructively updated when evolved.
-              evaluate signed
+          withMVar varKESState $ \KESState { kesStateInfo, kesStateKey } -> do
+            case kesStateKey of
+              KESKeyPoisoned ->
+                error "trying to sign with a poisoned key"
+              KESKey _ key -> do
+                let evolution = kesEvolution kesStateInfo
+                SL.signedKES () evolution toSign key
+      , forget = do
+          modifyMVar_ varKESState $ poisonState
+      , finalize_ = finalizer'
       }
   where
     initKESState :: KESState c
     initKESState = KESState {
         kesStateInfo = KESInfo {
-            kesStartPeriod = startPeriod
-          , kesEndPeriod   = Absolute.KESPeriod (start + fromIntegral maxKESEvolutions)
-            -- We always start from 0 as the key hasn't evolved yet.
+            kesStartPeriod = Absolute.KESPeriod 0
+          , kesEndPeriod   = Absolute.KESPeriod 0
           , kesEvolution   = 0
           }
-      , kesStateKey = KESKey initKey
+      , kesStateKey = KESKeyPoisoned
       }
 
+poisonState :: forall m c. (Crypto c, IOLike m)
+            => KESState c -> m (KESState c)
+poisonState kesState = do
+  case kesStateKey kesState of
+    KESKeyPoisoned -> do
+      -- already poisoned
+      return kesState
+    KESKey _ sk -> do
+      forgetSignKeyKES sk
+      return kesState { kesStateKey = KESKeyPoisoned }
+
 -- | Evolve the 'HotKey' so that its evolution matches the given KES period.
 --
 -- When the given KES period is after the end period of the 'HotKey', we
@@ -230,7 +378,7 @@ evolveKey varKESState targetPeriod = modifyMVar varKESState $ \kesState -> do
         let err = KESKeyAlreadyPoisoned info targetPeriod
         in return (kesState, UpdateFailed err)
 
-      KESKey key -> case kesStatus info targetPeriod of
+      KESKey ocert key -> case kesStatus info targetPeriod of
         -- When the absolute period is before the start period, we can't
         -- update the key. 'checkCanForge' will say we can't forge because the
         -- key is not valid yet.
@@ -239,9 +387,10 @@ evolveKey varKESState targetPeriod = modifyMVar varKESState $ \kesState -> do
 
         -- When the absolute period is after the end period, we can't evolve
         -- anymore and poison the expired key.
-        AfterKESEnd {} ->
+        AfterKESEnd {} -> do
             let err = KESCouldNotEvolve info targetPeriod
-            in return (poisonState kesState, UpdateFailed err)
+            poisonedState <- poisonState kesState
+            return (poisonedState, UpdateFailed err)
 
         InKESRange targetEvolution
           -- No evolving needed
@@ -251,27 +400,27 @@ evolveKey varKESState targetPeriod = modifyMVar varKESState $ \kesState -> do
           -- Evolving needed
           | otherwise
           -> (\s' -> (s', Updated (kesStateInfo s'))) <$>
-               go targetEvolution info key
+               go targetEvolution info ocert key
 
   where
-    poisonState :: KESState c -> KESState c
-    poisonState kesState = kesState { kesStateKey = KESKeyPoisoned }
-
     -- | PRECONDITION:
     --
     -- > targetEvolution >= curEvolution
-    go :: KESEvolution -> KESInfo -> SL.SignKeyKES c -> m (KESState c)
-    go targetEvolution info key
+    go :: KESEvolution -> KESInfo -> OCert.OCert c -> SL.SignKeyKES c -> m (KESState c)
+    go targetEvolution info ocert key
       | targetEvolution <= curEvolution
-      = return $ KESState { kesStateInfo = info, kesStateKey = KESKey key }
+      = return $ KESState { kesStateInfo = info, kesStateKey = KESKey ocert key }
       | otherwise
-      = case SL.updateKES () key curEvolution of
-          -- This cannot happen
-          Nothing    -> error "Could not update KES key"
-          Just !key' -> do
-            -- Clear the memory associated with the old key
-            forgetSignKeyKES key
-            let info' = info { kesEvolution = curEvolution + 1 }
-            go targetEvolution info' key'
+      = do
+          maybeKey' <- SL.updateKES () key curEvolution
+          case maybeKey' of
+            Nothing    ->
+              -- This cannot happen
+              error "Could not update KES key"
+            Just !key' -> do
+              -- Clear the memory associated with the old key
+              forgetSignKeyKES key
+              let info' = info { kesEvolution = curEvolution + 1 }
+              go targetEvolution info' ocert key'
       where
         curEvolution = kesEvolution info
diff --git a/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Praos.hs b/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Praos.hs
index ce8bcdb08e..08c8f2b555 100644
--- a/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Praos.hs
+++ b/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Praos.hs
@@ -160,27 +160,25 @@ forgePraosFields
   hotKey
   PraosCanBeLeader
     { praosCanBeLeaderColdVerKey,
-      praosCanBeLeaderSignKeyVRF,
-      praosCanBeLeaderOpCert
+      praosCanBeLeaderSignKeyVRF
     }
   PraosIsLeader {praosIsLeaderVrfRes}
   mkToSign = do
+    ocert <- HotKey.getOCert hotKey
+    let signedFields =
+          PraosToSign
+            { praosToSignIssuerVK = praosCanBeLeaderColdVerKey,
+              praosToSignVrfVK = VRF.deriveVerKeyVRF praosCanBeLeaderSignKeyVRF,
+              praosToSignVrfRes = praosIsLeaderVrfRes,
+              praosToSignOCert = ocert
+            }
+        toSign = mkToSign signedFields
     signature <- HotKey.sign hotKey toSign
     return
       PraosFields
         { praosSignature = signature,
           praosToSign = toSign
         }
-    where
-      toSign = mkToSign signedFields
-
-      signedFields =
-        PraosToSign
-          { praosToSignIssuerVK = praosCanBeLeaderColdVerKey,
-            praosToSignVrfVK = VRF.deriveVerKeyVRF praosCanBeLeaderSignKeyVRF,
-            praosToSignVrfRes = praosIsLeaderVrfRes,
-            praosToSignOCert = praosCanBeLeaderOpCert
-          }
 
 {-------------------------------------------------------------------------------
   Protocol proper
diff --git a/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Praos/AgentClient.hs b/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Praos/AgentClient.hs
new file mode 100644
index 0000000000..8451d6aaaa
--- /dev/null
+++ b/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Praos/AgentClient.hs
@@ -0,0 +1,183 @@
+{-# OPTIONS_GHC -Wno-orphans #-}
+
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE TypeSynonymInstances #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE ConstraintKinds #-}
+
+module Ouroboros.Consensus.Protocol.Praos.AgentClient (
+  runKESAgentClient,
+  AgentCrypto (..),
+  MonadKESAgent (..),
+  KESAgentContext,
+  KESAgentClientTrace (..),
+)
+where
+
+import qualified Cardano.KESAgent.KES.Bundle as Agent
+import qualified Cardano.KESAgent.KES.Crypto as Agent
+import qualified Cardano.KESAgent.KES.OCert as Agent
+import qualified Cardano.KESAgent.Processes.ServiceClient as Agent
+import qualified Cardano.KESAgent.Protocols.RecvResult as Agent
+import qualified Cardano.KESAgent.Protocols.VersionedProtocol as Agent
+import qualified Cardano.KESAgent.Protocols.StandardCrypto as Agent
+import qualified Cardano.KESAgent.Serialization.DirectCodec as Agent
+import           Cardano.KESAgent.Util.RefCounting
+import qualified Cardano.Protocol.TPraos.OCert as OCert
+import           Cardano.Ledger.Crypto (Crypto, KES, DSIGN, VRF, StandardCrypto)
+
+import Cardano.Crypto.KES.Class
+import Cardano.Crypto.VRF.Class
+import Cardano.Crypto.DirectSerialise (DirectSerialise, DirectDeserialise)
+
+import           Ouroboros.Network.RawBearer
+import           Ouroboros.Network.Snocket
+import           Ouroboros.Consensus.Util.IOLike
+
+import Control.Monad (forever)
+import Control.Monad.Class.MonadAsync
+import Control.Tracer
+import Data.Coerce (coerce)
+import Network.Socket
+import System.IOManager
+import Data.Typeable
+import Data.Kind
+import Data.SerDoc.Class as SerDoc
+import Control.Monad.IOSim
+import qualified Simulation.Network.Snocket as SimSnocket
+import Test.Ouroboros.Network.Data.AbsBearerInfo as ABI
+
+type KESAgentContext c m =
+      ( AgentCrypto c
+      , MonadKESAgent m
+      , SerDoc.HasInfo (Agent.DirectCodec m) (VerKeyKES (KES c))
+      , SerDoc.HasInfo (Agent.DirectCodec m) (SignKeyKES (KES c))
+      , IOLike m
+      )
+
+data KESAgentClientTrace
+  = KESAgentClientException SomeException
+  | KESAgentClientTrace Agent.ServiceClientTrace
+  deriving (Show)
+
+class ( Crypto c
+      , Agent.Crypto (ACrypto c)
+      , Agent.NamedCrypto (ACrypto c)
+      , Agent.KES (ACrypto c) ~ KES c
+      , Agent.DSIGN (ACrypto c) ~ DSIGN c
+      , ContextKES (KES c) ~ ()
+      , ContextVRF (VRF c) ~ ()
+      , Typeable (ACrypto c)
+      , Agent.ServiceClientDrivers (ACrypto c)
+      , DirectSerialise (SignKeyKES (KES c))
+      , DirectDeserialise (SignKeyKES (KES c))
+      )
+  => AgentCrypto c where
+        type ACrypto c :: Type
+
+instance AgentCrypto StandardCrypto where
+  type ACrypto StandardCrypto = Agent.StandardCrypto
+
+convertOCert :: ( AgentCrypto c
+                )
+              => Agent.OCert (ACrypto c) -> OCert.OCert c
+convertOCert oca =
+  OCert.OCert
+    { OCert.ocertVkHot = Agent.ocertVkHot oca
+    , OCert.ocertN = Agent.ocertN oca
+    , OCert.ocertKESPeriod = OCert.KESPeriod (Agent.unKESPeriod $ Agent.ocertKESPeriod oca)
+    , OCert.ocertSigma = coerce (Agent.ocertSigma oca)
+    }
+
+class (MonadFail m, Show (Addr m)) => MonadKESAgent m where
+  type FD m :: Type
+  type Addr m :: Type
+  withAgentContext :: (Snocket m (FD m) (Addr m) -> m a) -> m a
+  makeRawBearer :: MakeRawBearer m (FD m)
+  makeAddress :: Proxy m -> FilePath -> Addr m
+
+instance MonadKESAgent IO where
+  type FD IO = Socket
+  type Addr IO = SockAddr
+  withAgentContext inner =
+    withIOManager $ \ioManager ->
+      inner (socketSnocket ioManager)
+  makeRawBearer = makeSocketRawBearer
+  makeAddress _ = SockAddrUnix
+
+instance MonadKESAgent (IOSim s) where
+  type FD (IOSim s) = SimSnocket.FD (IOSim s) (TestAddress FilePath)
+  type Addr (IOSim s) = TestAddress FilePath
+  withAgentContext inner = do
+    SimSnocket.withSnocket
+      nullTracer
+      (toBearerInfo $ absNoAttenuation {abiConnectionDelay = SmallDelay})
+      mempty
+      $ \snocket _observe -> inner snocket
+  makeRawBearer = SimSnocket.makeFDRawBearer nullTracer
+  makeAddress _ = TestAddress
+
+instance SimSnocket.GlobalAddressScheme FilePath where
+  getAddressType = const SimSnocket.IPv4Address
+  ephemeralAddress _ty num = TestAddress $ "simSnocket_" <> show num
+
+runKESAgentClient :: forall m c.
+                     ( KESAgentContext c m
+                     )
+                  => Tracer m KESAgentClientTrace
+                  -> FilePath
+                  -> (OCert.OCert c -> SignKeyKES (KES c) -> Word -> m ())
+                  -> m ()
+runKESAgentClient tracer path handleKey = do
+  withAgentContext $ \snocket -> do
+    forever $ do
+      Agent.runServiceClient
+        (Proxy @(ACrypto c))
+        makeRawBearer
+        (Agent.ServiceClientOptions
+          { Agent.serviceClientSnocket = snocket
+          , Agent.serviceClientAddress = makeAddress (Proxy @m) path
+          } :: Agent.ServiceClientOptions m (FD m) (Addr m)
+        )
+        (\(Agent.Bundle skpRef ocert) -> do
+            -- We take ownership of the key, so we acquire one extra reference,
+            -- preventing the key from being discarded after `handleKey`
+            -- finishes.
+            _ <- acquireCRef skpRef
+            withCRefValue skpRef $ \(SignKeyWithPeriodKES sk p) ->
+              handleKey (convertOCert ocert) sk p
+            return Agent.RecvOK
+        )
+        (contramap KESAgentClientTrace tracer)
+        `catch` ( \(_e :: AsyncCancelled) ->
+                    return ()
+                )
+        `catch` ( \(e :: SomeException) ->
+                    traceWith tracer (KESAgentClientException e)
+                )
+      threadDelay 10000000
+
+toBearerInfo :: ABI.AbsBearerInfo -> SimSnocket.BearerInfo
+toBearerInfo abi =
+  SimSnocket.BearerInfo
+    { SimSnocket.biConnectionDelay = ABI.delay (ABI.abiConnectionDelay abi)
+    , SimSnocket.biInboundAttenuation = attenuation (ABI.abiInboundAttenuation abi)
+    , SimSnocket.biOutboundAttenuation = attenuation (ABI.abiOutboundAttenuation abi)
+    , SimSnocket.biInboundWriteFailure = ABI.abiInboundWriteFailure abi
+    , SimSnocket.biOutboundWriteFailure = ABI.abiOutboundWriteFailure abi
+    , SimSnocket.biAcceptFailures =
+        ( \(errDelay, errType) ->
+            ( ABI.delay errDelay
+            , errType
+            )
+        )
+          <$> abiAcceptFailure abi
+    , SimSnocket.biSDUSize = toSduSize (ABI.abiSDUSize abi)
+    }
+
diff --git a/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Praos/Common.hs b/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Praos/Common.hs
index 94241bc6c1..ff408bb582 100644
--- a/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Praos/Common.hs
+++ b/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/Praos/Common.hs
@@ -2,9 +2,13 @@
 {-# LANGUAGE DeriveAnyClass #-}
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE DerivingVia #-}
+{-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 
 -- | Various things common to iterations of the Praos protocol.
 module Ouroboros.Consensus.Protocol.Praos.Common (
@@ -15,24 +19,30 @@ module Ouroboros.Consensus.Protocol.Praos.Common (
     -- * node support
   , PraosNonces (..)
   , PraosProtocolSupportsNode (..)
+  , PraosCredentialsSource (..)
+  , instantiatePraosCredentials
   ) where
 
 import qualified Cardano.Crypto.VRF as VRF
-import           Cardano.Ledger.BaseTypes (Nonce)
 import qualified Cardano.Ledger.BaseTypes as SL
-import           Cardano.Ledger.Crypto (Crypto, VRF)
+import qualified Cardano.Crypto.KES.Class as KES
+import           Cardano.Ledger.BaseTypes (Nonce)
+import           Cardano.Ledger.Crypto (Crypto, VRF, KES)
 import           Cardano.Ledger.Keys (KeyHash, KeyRole (BlockIssuer))
 import qualified Cardano.Ledger.Shelley.API as SL
 import qualified Cardano.Protocol.TPraos.OCert as OCert
 import           Cardano.Slotting.Block (BlockNo)
 import           Cardano.Slotting.Slot (SlotNo)
+import           Control.Tracer (nullTracer)
 import           Data.Function (on)
 import           Data.Map.Strict (Map)
 import           Data.Ord (Down (Down))
 import           Data.Word (Word64)
 import           GHC.Generics (Generic)
-import           NoThunks.Class (NoThunks)
 import           Ouroboros.Consensus.Protocol.Abstract
+import qualified Ouroboros.Consensus.Protocol.Ledger.HotKey as HotKey
+import           Ouroboros.Consensus.Protocol.Praos.AgentClient
+import           Ouroboros.Consensus.Util.IOLike
 
 -- | The maximum major protocol version.
 --
@@ -245,16 +255,57 @@ instance Crypto c => ChainOrder (PraosChainSelectView c) where
   preferCandidate cfg ours cand = comparePraos cfg ours cand == LT
 
 data PraosCanBeLeader c = PraosCanBeLeader
-  { -- | Certificate delegating rights from the stake pool cold key (or
-    -- genesis stakeholder delegate cold key) to the online KES key.
-    praosCanBeLeaderOpCert     :: !(OCert.OCert c),
-    -- | Stake pool cold key or genesis stakeholder delegate cold key.
+  { -- | Stake pool cold key or genesis stakeholder delegate cold key.
     praosCanBeLeaderColdVerKey :: !(SL.VKey 'SL.BlockIssuer c),
-    praosCanBeLeaderSignKeyVRF :: !(SL.SignKeyVRF c)
+    praosCanBeLeaderSignKeyVRF :: !(SL.SignKeyVRF c),
+    -- | How to obtain KES credentials (ocert + sign key)
+    praosCanBeLeaderCredentialsSource :: !(PraosCredentialsSource c)
   }
   deriving (Generic)
 
-instance Crypto c => NoThunks (PraosCanBeLeader c)
+instance (NoThunks (KES.UnsoundPureSignKeyKES (KES c)), Crypto c) => NoThunks (PraosCanBeLeader c)
+
+-- | Defines a method for obtaining Praos credentials (opcert + KES signing
+-- key).
+data PraosCredentialsSource c
+  = -- | Pass an opcert and sign key directly. This uses
+    -- 'KES.UnsoundPureSignKeyKES', which does not provide mlocking guarantees,
+    -- violating the rule that KES secrets must never be stored on disk, but
+    -- allows the sign key to be loaded from a local file. This method is
+    -- provided for backwards compatibility.
+    PraosCredentialsUnsound (OCert.OCert c) (KES.UnsoundPureSignKeyKES (KES c))
+  | -- | Connect to a KES agent listening on a service socket at the given path.
+    PraosCredentialsAgent FilePath
+  deriving (Generic)
+
+instance (NoThunks (KES.UnsoundPureSignKeyKES (KES c)), Crypto c) => NoThunks (PraosCredentialsSource c)
+
+instantiatePraosCredentials :: forall m c.
+                               ( KESAgentContext c m
+                               )
+                            => Word64
+                            -> PraosCredentialsSource c
+                            -> m (HotKey.HotKey c m)
+instantiatePraosCredentials maxKESEvolutions (PraosCredentialsUnsound ocert skUnsound) = do
+  sk <- KES.unsoundPureSignKeyKESToSoundSignKeyKES skUnsound
+  let startPeriod :: OCert.KESPeriod
+      startPeriod = OCert.ocertKESPeriod ocert
+
+  HotKey.mkHotKey
+              ocert
+              sk
+              startPeriod
+              maxKESEvolutions
+
+instantiatePraosCredentials maxKESEvolutions (PraosCredentialsAgent path) = do
+  HotKey.mkDynamicHotKey
+      maxKESEvolutions
+      (Just $ \send -> do
+        let handleKey ocert sk p = do
+              send ocert sk p (OCert.ocertKESPeriod ocert)
+        runKESAgentClient nullTracer path handleKey
+      )
+      (pure ())
 
 -- | See 'PraosProtocolSupportsNode'
 data PraosNonces = PraosNonces {
diff --git a/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/TPraos.hs b/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/TPraos.hs
index 43529217bc..43d6026f5f 100644
--- a/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/TPraos.hs
+++ b/ouroboros-consensus-protocol/src/ouroboros-consensus-protocol/Ouroboros/Consensus/Protocol/TPraos.hs
@@ -129,21 +129,21 @@ forgeTPraosFields ::
   -> (TPraosToSign c -> toSign)
   -> m (TPraosFields c toSign)
 forgeTPraosFields hotKey PraosCanBeLeader{..} TPraosIsLeader{..} mkToSign = do
+    ocert <- HotKey.getOCert hotKey
+    let signedFields =
+          TPraosToSign {
+              tpraosToSignIssuerVK = praosCanBeLeaderColdVerKey
+            , tpraosToSignVrfVK    = VRF.deriveVerKeyVRF praosCanBeLeaderSignKeyVRF
+            , tpraosToSignEta      = tpraosIsLeaderEta
+            , tpraosToSignLeader   = tpraosIsLeaderProof
+            , tpraosToSignOCert    = ocert
+            }
+        toSign = mkToSign signedFields
     signature <- HotKey.sign hotKey toSign
     return TPraosFields {
         tpraosSignature = signature
       , tpraosToSign    = toSign
       }
-  where
-    toSign = mkToSign signedFields
-
-    signedFields = TPraosToSign {
-        tpraosToSignIssuerVK = praosCanBeLeaderColdVerKey
-      , tpraosToSignVrfVK    = VRF.deriveVerKeyVRF praosCanBeLeaderSignKeyVRF
-      , tpraosToSignEta      = tpraosIsLeaderEta
-      , tpraosToSignLeader   = tpraosIsLeaderProof
-      , tpraosToSignOCert    = praosCanBeLeaderOpCert
-      }
 
 -- | Because we are using the executable spec, rather than implementing the
 -- protocol directly here, we have a fixed header type rather than an
diff --git a/ouroboros-consensus-protocol/src/unstable-protocol-testlib/Test/Consensus/Protocol/Serialisation/Generators.hs b/ouroboros-consensus-protocol/src/unstable-protocol-testlib/Test/Consensus/Protocol/Serialisation/Generators.hs
index 7686d00a04..a17d958b84 100644
--- a/ouroboros-consensus-protocol/src/unstable-protocol-testlib/Test/Consensus/Protocol/Serialisation/Generators.hs
+++ b/ouroboros-consensus-protocol/src/unstable-protocol-testlib/Test/Consensus/Protocol/Serialisation/Generators.hs
@@ -1,4 +1,6 @@
 {-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE UndecidableInstances #-}
 
 {-# OPTIONS_GHC -Wno-orphans #-}
 
@@ -6,7 +8,7 @@
 -- to be semantically correct at all, only structurally correct.
 module Test.Consensus.Protocol.Serialisation.Generators () where
 
-import           Cardano.Crypto.KES (signedKES)
+import           Cardano.Crypto.KES (unsoundPureSignedKES)
 import           Cardano.Crypto.VRF (evalCertified)
 import           Cardano.Protocol.TPraos.BHeader (HashHeader, PrevHash (..))
 import           Cardano.Protocol.TPraos.OCert (KESPeriod (KESPeriod),
@@ -27,7 +29,7 @@ import           Test.QuickCheck (Arbitrary (..), Gen, choose, oneof)
 instance Arbitrary InputVRF where
   arbitrary = mkInputVRF <$> arbitrary <*> arbitrary
 
-instance Praos.PraosCrypto c => Arbitrary (HeaderBody c) where
+instance (Praos.PraosCrypto c) => Arbitrary (HeaderBody c) where
   arbitrary =
     let ocert =
           OCert
@@ -55,12 +57,12 @@ instance Praos.PraosCrypto c => Arbitrary (HeaderBody c) where
           <*> ocert
           <*> arbitrary
 
-instance Praos.PraosCrypto c => Arbitrary (Header c) where
+instance (Praos.PraosCrypto c) => Arbitrary (Header c) where
   arbitrary = do
     hBody <- arbitrary
     period <- arbitrary
     sKey <- arbitrary
-    let hSig = signedKES () period hBody sKey
+    let hSig = unsoundPureSignedKES () period hBody sKey
     pure $ Header hBody hSig
 
 instance Praos.PraosCrypto c => Arbitrary (PraosState c) where
diff --git a/ouroboros-consensus-protocol/src/unstable-protocol-testlib/Test/Ouroboros/Consensus/Protocol/Praos/Header.hs b/ouroboros-consensus-protocol/src/unstable-protocol-testlib/Test/Ouroboros/Consensus/Protocol/Praos/Header.hs
index 09c9f65c6e..05ff3d27a6 100644
--- a/ouroboros-consensus-protocol/src/unstable-protocol-testlib/Test/Ouroboros/Consensus/Protocol/Praos/Header.hs
+++ b/ouroboros-consensus-protocol/src/unstable-protocol-testlib/Test/Ouroboros/Consensus/Protocol/Praos/Header.hs
@@ -27,8 +27,6 @@ import           Cardano.Crypto.DSIGN
 import           Cardano.Crypto.Hash (Blake2b_256, Hash, hashFromBytes,
                      hashToBytes, hashWith)
 import qualified Cardano.Crypto.KES as KES
-import           Cardano.Crypto.KES.Class (genKeyKES, rawDeserialiseSignKeyKES,
-                     rawSerialiseSignKeyKES)
 import           Cardano.Crypto.Seed (mkSeedFromBytes)
 import           Cardano.Crypto.VRF (deriveVerKeyVRF, hashVerKeyVRF,
                      rawDeserialiseSignKeyVRF, rawSerialiseSignKeyVRF)
@@ -115,14 +113,14 @@ mutate context header mutation =
                 let Header body _ = header
                 newKESSignKey <- newKESSigningKey <$> gen32Bytes
                 KESPeriod kesPeriod <- genValidKESPeriod (hbSlotNo body) praosSlotsPerKESPeriod
-                let sig' = KES.signKES () kesPeriod body newKESSignKey
+                let sig' = KES.unsoundPureSignKES () kesPeriod body newKESSignKey
                 pure (context, Header body (KES.SignedKES sig'))
             MutateColdKey -> do
                 let Header body _ = header
                 newColdSignKey <- genKeyDSIGN . mkSeedFromBytes <$> gen32Bytes
                 (hbOCert, KESPeriod kesPeriod) <- genCert (hbSlotNo body) context{coldSignKey = newColdSignKey}
                 let newBody = body{hbOCert}
-                let sig' = KES.signKES () kesPeriod newBody kesSignKey
+                let sig' = KES.unsoundPureSignKES () kesPeriod newBody kesSignKey
                 pure (context, Header newBody (KES.SignedKES sig'))
             MutateKESPeriod -> do
                 let Header body _ = header
@@ -137,7 +135,7 @@ mutate context header mutation =
                                     , ocertSigma = signedDSIGN @StandardCrypto coldSignKey (OCertSignable ocertVkHot ocertN newKESPeriod)
                                     }
                             }
-                let sig' = KES.signKES () kesPeriod' newBody kesSignKey
+                let sig' = KES.unsoundPureSignKES () kesPeriod' newBody kesSignKey
                 pure (context, Header newBody (KES.SignedKES sig'))
             MutateKESPeriodBefore -> do
                 let Header body _ = header
@@ -147,7 +145,7 @@ mutate context header mutation =
                     period' = unSlotNo newSlotNo `div` praosSlotsPerKESPeriod
                     hbVrfRes = VRF.evalCertified () rho' vrfSignKey
                     newBody = body{hbSlotNo = newSlotNo, hbVrfRes}
-                    sig' = KES.signKES () (fromIntegral period' - kesPeriod) newBody kesSignKey
+                    sig' = KES.unsoundPureSignKES () (fromIntegral period' - kesPeriod) newBody kesSignKey
                 pure (context, Header newBody (KES.SignedKES sig'))
             MutateCounterOver1 -> do
                 let poolId = coerce $ hashKey $ VKey $ deriveVerKeyDSIGN coldSignKey
@@ -255,13 +253,13 @@ instance Json.FromJSON MutatedHeader where
             either (fail . show) pure $ decodeFullAnnotator @(Header StandardCrypto) testVersion "Header" decCBOR $ LBS.fromStrict headerBytes
 
 -- * Generators
-type KESKey = KES.SignKeyKES (KES.Sum6KES Ed25519DSIGN Blake2b_256)
+type KESKey = KES.UnsoundPureSignKeyKES (KES.Sum6KES Ed25519DSIGN Blake2b_256)
 
 newVRFSigningKey :: ByteString -> (VRF.SignKeyVRF VRF.PraosVRF, VRF.VerKeyVRF VRF.PraosVRF)
 newVRFSigningKey = VRF.genKeyPairVRF . mkSeedFromBytes
 
 newKESSigningKey :: ByteString -> KESKey
-newKESSigningKey = genKeyKES . mkSeedFromBytes
+newKESSigningKey = KES.unsoundPureGenKeyKES . mkSeedFromBytes
 
 data GeneratorContext = GeneratorContext
     { praosSlotsPerKESPeriod :: !Word64
@@ -279,7 +277,8 @@ instance Eq GeneratorContext where
     a == b =
         praosSlotsPerKESPeriod a == praosSlotsPerKESPeriod b
             && praosMaxKESEvo a == praosMaxKESEvo b
-            && serialize' testVersion (kesSignKey a) == serialize' testVersion (kesSignKey b)
+            && serialize' testVersion (KES.encodeUnsoundPureSignKeyKES (kesSignKey a)) ==
+               serialize' testVersion (KES.encodeUnsoundPureSignKeyKES (kesSignKey b))
             && coldSignKey a == coldSignKey b
             && vrfSignKey a == vrfSignKey b
             && nonce a == nonce b
@@ -298,7 +297,7 @@ instance Json.ToJSON GeneratorContext where
             , "activeSlotCoeff" .= activeSlotVal activeSlotCoeff
             ]
       where
-        rawKesSignKey = decodeUtf8 . Base16.encode $ rawSerialiseSignKeyKES kesSignKey
+        rawKesSignKey = decodeUtf8 . Base16.encode $ KES.rawSerialiseUnsoundPureSignKeyKES kesSignKey
         rawColdSignKey = decodeUtf8 . Base16.encode $ rawSerialiseSignKeyDSIGN coldSignKey
         rawVrfSignKey = decodeUtf8 . Base16.encode $ rawSerialiseSignKeyVRF $ skToBatchCompat vrfSignKey
         rawVrVKeyHash = decodeUtf8 . Base16.encode $ hashToBytes $ hashVerKeyVRF @_ @Blake2b_256 $ deriveVerKeyVRF vrfSignKey
@@ -337,7 +336,7 @@ instance Json.FromJSON GeneratorContext where
             case Base16.decode (encodeUtf8 rawKey) of
                 Left err -> fail err
                 Right keyBytes ->
-                    case rawDeserialiseSignKeyKES keyBytes of
+                    case KES.rawDeserialiseUnsoundPureSignKeyKES keyBytes of
                         Nothing -> fail $ "Invalid KES key bytes: " <> show rawKey
                         Just key -> pure key
         parseVrfSignKey rawKey = do
@@ -376,7 +375,7 @@ generated for the purpose of producing the header are returned.
 genHeader :: GeneratorContext -> Gen (Header StandardCrypto)
 genHeader context = do
     (body, KESPeriod kesPeriod) <- genHeaderBody context
-    let sign = KES.SignedKES $ KES.signKES () kesPeriod body kesSignKey
+    let sign = KES.SignedKES $ KES.unsoundPureSignKES () kesPeriod body kesSignKey
     pure $ (Header body sign)
   where
     GeneratorContext{kesSignKey} = context
@@ -420,7 +419,7 @@ protocolVersionZero = ProtVer versionZero 0
 
 genCert :: SlotNo -> GeneratorContext -> Gen (OCert StandardCrypto, KESPeriod)
 genCert slotNo context = do
-    let ocertVkHot = KES.deriveVerKeyKES kesSignKey
+    let ocertVkHot = KES.unsoundPureDeriveVerKeyKES kesSignKey
         poolId = coerce $ hashKey $ VKey $ deriveVerKeyDSIGN coldSignKey
         ocertN = fromMaybe 0 $ Map.lookup poolId ocertCounters
     ocertKESPeriod <- genValidKESPeriod slotNo praosSlotsPerKESPeriod
diff --git a/ouroboros-consensus/changelog.d/20250130_093251_tdammers_mlocked_kes_rebase.md b/ouroboros-consensus/changelog.d/20250130_093251_tdammers_mlocked_kes_rebase.md
new file mode 100644
index 0000000000..0aa430bf84
--- /dev/null
+++ b/ouroboros-consensus/changelog.d/20250130_093251_tdammers_mlocked_kes_rebase.md
@@ -0,0 +1,8 @@
+### Breaking
+
+- Use new mlocked KES API to represent KES sign keys internally. This ensures
+  that KES keys are securely erased when replaced with a newer evolution or a
+  fresh key, and that they will not spill to disk or swap. See
+  https://github.com/IntersectMBO/cardano-base/pull/255.
+- Add `finalize` method to `BlockForging`, and use it where necessary to clean
+  up when a block forging thread terminates (see `forkLinkedWatcherFinalize`)
diff --git a/ouroboros-consensus/ouroboros-consensus.cabal b/ouroboros-consensus/ouroboros-consensus.cabal
index 749b54b134..b5f1dcd2a6 100644
--- a/ouroboros-consensus/ouroboros-consensus.cabal
+++ b/ouroboros-consensus/ouroboros-consensus.cabal
@@ -278,7 +278,7 @@ library
     bytestring >=0.10 && <0.13,
     cardano-binary,
     cardano-crypto-class,
-    cardano-ledger-core ^>=1.16,
+    cardano-ledger-core ^>=1.17,
     cardano-prelude,
     cardano-slotting,
     cardano-strict-containers,
@@ -471,7 +471,7 @@ library unstable-mock-block
     bytestring,
     cardano-binary,
     cardano-crypto-class,
-    cardano-slotting:{cardano-slotting, testlib},
+    cardano-slotting:{cardano-slotting},
     cborg,
     containers,
     deepseq,
@@ -543,8 +543,8 @@ test-suite consensus-test
     base,
     base-deriving-via,
     cardano-binary,
-    cardano-crypto-class,
-    cardano-crypto-tests,
+    cardano-crypto-class ^>= 2.2,
+    cardano-crypto-tests ^>= 2.2,
     cardano-slotting:{cardano-slotting, testlib},
     cborg,
     containers,
@@ -652,8 +652,8 @@ test-suite storage-test
     bifunctors,
     binary,
     bytestring,
-    cardano-crypto-class,
-    cardano-slotting:{cardano-slotting, testlib},
+    cardano-crypto-class ^>= 2.2,
+    cardano-slotting:{cardano-slotting,testlib},
     cborg,
     containers,
     contra-tracer,
diff --git a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Block/Forging.hs b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Block/Forging.hs
index 03e5682d93..3698b362ec 100644
--- a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Block/Forging.hs
+++ b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Block/Forging.hs
@@ -143,6 +143,15 @@ data BlockForging m blk = BlockForging {
         -> [Validated (GenTx blk)]      -- Transactions to include
         -> IsLeader (BlockProtocol blk) -- Proof we are leader
         -> m blk
+
+      -- | Clean up any unmanaged resources.
+      --
+      -- Such resources may include KES keys that require explicit erasing
+      -- ("secure forgetting"), and threads that connect to a KES agent.
+      -- This method will be run once when the block forging thread
+      -- terminates, whether cleanly or due to an exception.
+    , finalize :: m ()
+
     }
 
 data ShouldForge blk =
diff --git a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/HardFork/Combinator/Embed/Unary.hs b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/HardFork/Combinator/Embed/Unary.hs
index d182dbb22e..f09548067a 100644
--- a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/HardFork/Combinator/Embed/Unary.hs
+++ b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/HardFork/Combinator/Embed/Unary.hs
@@ -417,6 +417,7 @@ instance Functor m => Isomorphic (BlockForging m) where
   project BlockForging {..} = BlockForging {
         forgeLabel       = forgeLabel
       , canBeLeader      = project' (Proxy @(WrapCanBeLeader blk)) canBeLeader
+      , finalize         = finalize
       , updateForgeState = \cfg sno tickedChainDepSt ->
                                project <$>
                                  updateForgeState
@@ -464,6 +465,7 @@ instance Functor m => Isomorphic (BlockForging m) where
   inject BlockForging {..} = BlockForging {
         forgeLabel       = forgeLabel
       , canBeLeader      = inject' (Proxy @(WrapCanBeLeader blk)) canBeLeader
+      , finalize         = finalize
       , updateForgeState = \cfg sno tickedChainDepSt ->
                                inject <$>
                                  updateForgeState
diff --git a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/HardFork/Combinator/Forging.hs b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/HardFork/Combinator/Forging.hs
index 5aab6219d9..6ba6aa7b3d 100644
--- a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/HardFork/Combinator/Forging.hs
+++ b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/HardFork/Combinator/Forging.hs
@@ -15,8 +15,11 @@ module Ouroboros.Consensus.HardFork.Combinator.Forging (
   , hardForkBlockForging
   ) where
 
+import           Control.Monad (void)
 import           Data.Functor.Product
 import           Data.Maybe (fromMaybe)
+import           Data.SOP (Top)
+import           Data.SOP.Constraint (All)
 import           Data.SOP.BasicFunctors
 import           Data.SOP.Functors (Product2 (..))
 import           Data.SOP.Index
@@ -90,6 +93,7 @@ hardForkBlockForging label blockForging =
       , updateForgeState = hardForkUpdateForgeState          blockForging
       , checkCanForge    = hardForkCheckCanForge             blockForging
       , forgeBlock       = hardForkForgeBlock                blockForging
+      , finalize         = hardForkFinalize                  blockForging
       }
 
 hardForkCanBeLeader ::
@@ -99,6 +103,11 @@ hardForkCanBeLeader =
       SomeErasCanBeLeader
     . hmap (WrapCanBeLeader . canBeLeader)
 
+hardForkFinalize :: (Monad m, All Top xs)
+                 => NonEmptyOptNP (BlockForging m) xs -> m ()
+hardForkFinalize blockForging =
+  void $ htraverse_ finalize blockForging
+
 -- | POSTCONDITION: the returned 'ForgeStateUpdateInfo' is from the same era as
 -- the ticked 'ChainDepState'.
 hardForkUpdateForgeState ::
diff --git a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/Jumping.hs b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/Jumping.hs
index 1e951a0a37..680dbe56be 100644
--- a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/Jumping.hs
+++ b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/Jumping.hs
@@ -360,9 +360,7 @@ data Instruction blk
 deriving instance (HasHeader (Header blk), Eq (Header blk)) => Eq (Instruction blk)
 deriving instance (HasHeader (Header blk), Show (Header blk)) => Show (Instruction blk)
 deriving anyclass instance
-  ( HasHeader blk,
-    LedgerSupportsProtocol blk,
-    NoThunks (Header blk)
+  ( LedgerSupportsProtocol blk
   ) => NoThunks (Instruction blk)
 
 data JumpInstruction blk
@@ -382,9 +380,7 @@ instance (HasHeader (Header blk), Show (Header blk)) => Show (JumpInstruction bl
       showParen (p > 10) $ showString "JumpToGoodPoint " . shows (AF.headPoint $ jTheirFragment jumpInfo)
 
 deriving anyclass instance
-  ( HasHeader blk,
-    LedgerSupportsProtocol blk,
-    NoThunks (Header blk)
+  ( LedgerSupportsProtocol blk
   ) => NoThunks (JumpInstruction blk)
 
 -- | The result of a jump request, either accepted or rejected.
@@ -397,9 +393,7 @@ deriving instance (HasHeader (Header blk), Eq (Header blk)) => Eq (JumpResult bl
 deriving instance (HasHeader (Header blk), Show (Header blk)) => Show (JumpResult blk)
 
 deriving anyclass instance
-  ( HasHeader blk,
-    LedgerSupportsProtocol blk,
-    NoThunks (Header blk)
+  ( LedgerSupportsProtocol blk
   ) => NoThunks (JumpResult blk)
 
 -- | Compute the next instruction for the given peer. In the majority of cases,
diff --git a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/State.hs b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/State.hs
index 6faef18cff..b9d22d8465 100644
--- a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/State.hs
+++ b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/MiniProtocol/ChainSync/Client/State.hs
@@ -97,9 +97,7 @@ data ChainSyncClientHandle m blk = ChainSyncClientHandle {
 
 deriving anyclass instance (
   IOLike m,
-  HasHeader blk,
-  LedgerSupportsProtocol blk,
-  NoThunks (Header blk)
+  LedgerSupportsProtocol blk
   ) => NoThunks (ChainSyncClientHandle m blk)
 
 -- | A collection of ChainSync client handles for the peers of this node.
@@ -125,10 +123,8 @@ data ChainSyncClientHandleCollection peer m blk = ChainSyncClientHandleCollectio
 
 deriving anyclass instance (
   IOLike m,
-  HasHeader blk,
   LedgerSupportsProtocol blk,
   NoThunks (STM m ()),
-  NoThunks (Header blk),
   NoThunks (STM m (Map peer (ChainSyncClientHandle m blk))),
   NoThunks (STM m (StrictSeq (peer, ChainSyncClientHandle m blk)))
   ) => NoThunks (ChainSyncClientHandleCollection peer m blk)
@@ -175,9 +171,7 @@ data DynamoInitState blk
   deriving (Generic)
 
 deriving anyclass instance
-  ( HasHeader blk,
-    LedgerSupportsProtocol blk,
-    NoThunks (Header blk)
+  ( LedgerSupportsProtocol blk
   ) => NoThunks (DynamoInitState blk)
 
 data ObjectorInitState
@@ -241,9 +235,7 @@ data ChainSyncJumpingState m blk
 
 deriving anyclass instance
   ( IOLike m,
-    HasHeader blk,
-    LedgerSupportsProtocol blk,
-    NoThunks (Header blk)
+    LedgerSupportsProtocol blk
   ) => NoThunks (ChainSyncJumpingState m blk)
 
 -- | The ChainSync state required for jumps
@@ -295,7 +287,5 @@ data ChainSyncJumpingJumperState blk
   deriving (Generic)
 
 deriving anyclass instance
-  ( HasHeader blk,
-    LedgerSupportsProtocol blk,
-    NoThunks (Header blk)
+  ( LedgerSupportsProtocol blk
   ) => NoThunks (ChainSyncJumpingJumperState blk)
diff --git a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/EarlyExit.hs b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/EarlyExit.hs
index d132bec59c..34cba81e82 100644
--- a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/EarlyExit.hs
+++ b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/EarlyExit.hs
@@ -329,7 +329,7 @@ instance MonadLabelledSTM m => MonadLabelledSTM (WithEarlyExit m) where
 instance MonadSay m => MonadSay (WithEarlyExit m) where
   say = lift . say
 
-instance (MonadInspectSTM m, Monad (InspectMonad m)) =>  MonadInspectSTM (WithEarlyExit m) where
+instance (MonadInspectSTM m) =>  MonadInspectSTM (WithEarlyExit m) where
     type InspectMonad (WithEarlyExit m) = InspectMonad m
     inspectTVar  _ = inspectTVar (Proxy @m)
     inspectTMVar _ = inspectTMVar (Proxy @m)
diff --git a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/Orphans.hs b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/Orphans.hs
index 0ba537b87b..ea3bd3ecdb 100644
--- a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/Orphans.hs
+++ b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/Orphans.hs
@@ -14,7 +14,7 @@ module Ouroboros.Consensus.Util.Orphans () where
 
 import           Cardano.Crypto.DSIGN.Class
 import           Cardano.Crypto.DSIGN.Mock (MockDSIGN)
-import           Cardano.Crypto.Hash (Hash)
+import           Cardano.Crypto.Hash (Hash, SizeHash)
 import           Cardano.Ledger.Genesis (NoGenesis (..))
 import           Codec.CBOR.Decoding (Decoder)
 import           Codec.Serialise (Serialise (..))
@@ -26,6 +26,7 @@ import qualified Data.IntPSQ as PSQ
 import           Data.MultiSet (MultiSet)
 import qualified Data.MultiSet as MultiSet
 import           Data.SOP.BasicFunctors
+import           GHC.TypeLits (KnownNat)
 import           NoThunks.Class (InspectHeap (..), InspectHeapNamed (..),
                      NoThunks (..), OnlyCheckWhnfNamed (..), allNoThunks,
                      noThunksInKeysAndValues)
@@ -38,7 +39,7 @@ import           System.FS.CRC (CRC (CRC))
   Serialise
 -------------------------------------------------------------------------------}
 
-instance Serialise (Hash h a) where
+instance KnownNat (SizeHash h) => Serialise (Hash h a) where
 
 instance Serialise (VerKeyDSIGN MockDSIGN) where
   encode = encodeVerKeyDSIGN
diff --git a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/STM.hs b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/STM.hs
index 947ab3e927..4a38f06892 100644
--- a/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/STM.hs
+++ b/ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Util/STM.hs
@@ -11,6 +11,7 @@ module Ouroboros.Consensus.Util.STM (
     -- * 'Watcher'
     Watcher (..)
   , forkLinkedWatcher
+  , forkLinkedWatcherFinalize
   , withWatcher
     -- * Misc
   , Fingerprint (..)
@@ -163,6 +164,19 @@ forkLinkedWatcher :: forall m a fp. (IOLike m, Eq fp, HasCallStack)
 forkLinkedWatcher registry label watcher =
     forkLinkedThread registry label $ runWatcher watcher
 
+-- | Spawn a new thread that runs a 'Watcher', executing a finalizer when the
+-- thread terminates.
+--
+-- The thread will be linked to the registry.
+forkLinkedWatcherFinalize :: forall m a fp. (IOLike m, Eq fp, HasCallStack)
+                          => ResourceRegistry m
+                          -> String    -- ^ Label for the thread
+                          -> Watcher m a fp
+                          -> m ()
+                          -> m (Thread m Void)
+forkLinkedWatcherFinalize registry label watcher finalizer =
+    forkLinkedThread registry label $ runWatcher watcher `finally` finalizer
+
 -- | Spawn a new thread that runs a 'Watcher'
 --
 -- The thread is bracketed via 'withAsync' and 'link'ed.
diff --git a/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Ledger/Block.hs b/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Ledger/Block.hs
index f6db8e90cf..17933a9dcd 100644
--- a/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Ledger/Block.hs
+++ b/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Ledger/Block.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE ConstraintKinds #-}
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE DeriveAnyClass #-}
 {-# LANGUAGE DeriveGeneric #-}
@@ -76,6 +77,7 @@ import           Data.Proxy
 import           Data.Typeable
 import           Data.Word
 import           GHC.Generics (Generic)
+import           GHC.TypeNats (KnownNat)
 import           NoThunks.Class (NoThunks (..))
 import           Ouroboros.Consensus.Block
 import           Ouroboros.Consensus.Config
@@ -162,6 +164,8 @@ instance (SimpleCrypto c, Typeable ext, Typeable ext')
 
   headerIsEBB = const Nothing
 
+type KnownHashSize c = KnownNat (Hash.SizeHash (SimpleHash c))
+
 data SimpleStdHeader c ext = SimpleStdHeader {
       simplePrev     :: ChainHash (SimpleBlock c ext)
     , simpleSlotNo   :: SlotNo
@@ -170,7 +174,10 @@ data SimpleStdHeader c ext = SimpleStdHeader {
     , simpleBodySize :: SizeInBytes
     }
   deriving stock    (Generic, Show, Eq)
-  deriving anyclass (Serialise, NoThunks)
+  deriving anyclass (NoThunks)
+
+deriving anyclass instance KnownHashSize c =>
+  Serialise (SimpleStdHeader c ext)
 
 data SimpleBody = SimpleBody {
       simpleTxs :: [Mock.Tx]
@@ -367,7 +374,10 @@ newtype instance LedgerState (SimpleBlock c ext) = SimpleLedgerState {
       simpleLedgerState :: MockState (SimpleBlock c ext)
     }
   deriving stock   (Generic, Show, Eq)
-  deriving newtype (Serialise, NoThunks)
+  deriving newtype (NoThunks)
+
+deriving anyclass instance KnownHashSize c =>
+  Serialise (LedgerState (SimpleBlock c ext))
 
 -- Ticking has no effect on the simple ledger state
 newtype instance Ticked (LedgerState (SimpleBlock c ext)) = TickedSimpleLedgerState {
@@ -541,7 +551,7 @@ instance InspectLedger (SimpleBlock c ext) where
   Crypto needed for simple blocks
 -------------------------------------------------------------------------------}
 
-class (HashAlgorithm (SimpleHash c), Typeable c) => SimpleCrypto c where
+class (KnownHashSize c, HashAlgorithm (SimpleHash c), Typeable c) => SimpleCrypto c where
   type family SimpleHash c :: Type
 
 data SimpleStandardCrypto
@@ -598,7 +608,8 @@ instance Condense ext' => Condense (SimpleBlock' c ext ext') where
 instance ToCBOR SimpleBody where
   toCBOR = encode
 
-encodeSimpleHeader :: (ext' -> CBOR.Encoding)
+encodeSimpleHeader :: KnownHashSize c
+                   => (ext' -> CBOR.Encoding)
                    -> Header (SimpleBlock' c ext ext')
                    -> CBOR.Encoding
 encodeSimpleHeader encodeExt SimpleHeader{..} =  mconcat [
diff --git a/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node.hs b/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node.hs
index dab988bc6d..317ce07382 100644
--- a/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node.hs
+++ b/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node.hs
@@ -102,6 +102,7 @@ simpleBlockForging aCanBeLeader aForgeExt = BlockForging {
               lst
               (map txForgetValidated txs)
               proof
+    , finalize = pure ()
     }
   where
     _ = keepRedundantConstraint (Proxy @(ForgeStateUpdateError (SimpleBlock c ext) ~ Void))
diff --git a/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node/PBFT.hs b/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node/PBFT.hs
index c2b22c8c40..96f58b752f 100644
--- a/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node/PBFT.hs
+++ b/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node/PBFT.hs
@@ -110,4 +110,5 @@ pbftBlockForging canBeLeader = BlockForging {
               lst
               (map txForgetValidated txs)
               proof
+    , finalize = pure ()
     }
diff --git a/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node/Praos.hs b/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node/Praos.hs
index 00d678da6d..5756154ad9 100644
--- a/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node/Praos.hs
+++ b/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Node/Praos.hs
@@ -104,7 +104,7 @@ blockForgingPraos numCoreNodes nid = sequence [praosBlockForging nid initHotKey]
     initHotKey =
         HotKey
           0
-          (SignKeyMockKES
+          (UnsoundPureSignKeyMockKES
             -- key ID
             (fst $ verKeys Map.! nid)
             -- KES initial slot
@@ -136,4 +136,5 @@ praosBlockForging cid initHotKey = do
                                    tickedLedgerSt
                                    (map txForgetValidated txs)
                                    isLeader
+      , finalize = pure ()
       }
diff --git a/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Protocol/Praos.hs b/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Protocol/Praos.hs
index 73407f75af..9a2c28d4fe 100644
--- a/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Protocol/Praos.hs
+++ b/ouroboros-consensus/src/unstable-mock-block/Ouroboros/Consensus/Mock/Protocol/Praos.hs
@@ -43,11 +43,12 @@ module Ouroboros.Consensus.Mock.Protocol.Praos (
   ) where
 
 import           Cardano.Binary (FromCBOR (..), ToCBOR (..), serialize')
-import           Cardano.Crypto.DSIGN.Ed448 (Ed448DSIGN)
+import           Cardano.Crypto.DSIGN.Ed25519 (Ed25519DSIGN)
 import           Cardano.Crypto.Hash.Class (HashAlgorithm (..), hashToBytes,
                      hashWithSerialiser, sizeHash)
 import           Cardano.Crypto.Hash.SHA256 (SHA256)
 import           Cardano.Crypto.KES.Class
+
 import           Cardano.Crypto.KES.Mock
 import           Cardano.Crypto.KES.Simple
 import           Cardano.Crypto.Util
@@ -76,7 +77,6 @@ import           Ouroboros.Consensus.NodeId (CoreNodeId (..))
 import           Ouroboros.Consensus.Protocol.Abstract
 import           Ouroboros.Consensus.Protocol.Signed
 import           Ouroboros.Consensus.Util.Condense
-import           Test.Cardano.Slotting.Numeric ()
 
 -- The Praos paper can be located at https://ia.cr/2017/573
 --
@@ -203,12 +203,15 @@ praosValidateView getFields hdr =
 data HotKey c =
     HotKey
       !Period  -- ^ Absolute period of the KES key
-      !(SignKeyKES (PraosKES c))
+      !(UnsoundPureSignKeyKES (PraosKES c))
   | HotKeyPoisoned
   deriving (Generic)
 
-instance PraosCrypto c => NoThunks (HotKey c)
-deriving instance PraosCrypto c => Show (HotKey c)
+instance (PraosCrypto c, NoThunks (UnsoundPureSignKeyKES (PraosKES c))) => NoThunks (HotKey c)
+
+instance PraosCrypto c => Show (HotKey c) where
+  show (HotKey p _) = "HotKey " ++ show p ++ " <SignKeyKES: hidden>"
+  show HotKeyPoisoned = "HotKeyPoisoned"
 
 -- | The 'HotKey' could not be evolved to the given 'Period'.
 newtype HotKeyEvolutionError = HotKeyEvolutionError Period
@@ -229,7 +232,7 @@ evolveKey slotNo hotKey = case hotKey of
       | keyPeriod >= targetPeriod
       -> (hotKey, Updated hotKey)
       | otherwise
-      -> case updateKES () oldKey keyPeriod of
+      -> case unsoundPureUpdateKES () oldKey keyPeriod of
            Nothing     ->
              (HotKeyPoisoned, UpdateFailed $ HotKeyEvolutionError targetPeriod)
            Just newKey ->
@@ -251,11 +254,11 @@ forgePraosFields :: ( PraosCrypto c
                  => PraosProof c
                  -> HotKey c
                  -> (PraosExtraFields c -> toSign)
-                 -> PraosFields c toSign
+                 -> (PraosFields c toSign)
 forgePraosFields PraosProof{..} hotKey mkToSign =
     case hotKey of
       HotKey kesPeriod key -> PraosFields {
-          praosSignature   = signedKES () kesPeriod (mkToSign fieldsToSign) key
+          praosSignature   = unsoundPureSignedKES () kesPeriod (mkToSign fieldsToSign) key
         , praosExtraFields = fieldsToSign
         }
       HotKeyPoisoned -> error "trying to sign with a poisoned key"
@@ -406,14 +409,14 @@ infosEta :: forall c. (PraosCrypto c)
          -> [BlockInfo c]
          -> EpochNo
          -> Natural
-infosEta l _  0 =
+infosEta l _  (EpochNo 0) =
     praosInitialEta l
-infosEta l@PraosConfig{praosParams = PraosParams{..}} xs e =
+infosEta l@PraosConfig{praosParams = PraosParams{..}} xs (EpochNo e) =
     let e'   = e - 1
         -- the η from the previous epoch
-        eta' = infosEta l xs e'
+        eta' = infosEta l xs (EpochNo e')
         -- the first slot in previous epoch
-        from = epochFirst l e'
+        from = epochFirst l (EpochNo e')
         -- 2/3 of the slots per epoch
         n    = div (2 * praosSlotsPerEpoch) 3
         -- the last of the 2/3 of slots in this epoch
@@ -591,7 +594,7 @@ rhoYT st xs s nid =
   Crypto models
 -------------------------------------------------------------------------------}
 
-class ( KESAlgorithm  (PraosKES  c)
+class ( UnsoundPureKESAlgorithm  (PraosKES  c)
       , VRFAlgorithm  (PraosVRF  c)
       , HashAlgorithm (PraosHash c)
       , Typeable c
@@ -609,7 +612,7 @@ data PraosStandardCrypto
 data PraosMockCrypto
 
 instance PraosCrypto PraosStandardCrypto where
-  type PraosKES  PraosStandardCrypto = SimpleKES Ed448DSIGN 1000
+  type PraosKES  PraosStandardCrypto = SimpleKES Ed25519DSIGN 1000
   type PraosVRF  PraosStandardCrypto = SimpleVRF
   type PraosHash PraosStandardCrypto = SHA256
 
diff --git a/sop-extras/changelog.d/20250130_111443_tdammers_mlocked_kes_rebase.md b/sop-extras/changelog.d/20250130_111443_tdammers_mlocked_kes_rebase.md
new file mode 100644
index 0000000000..9b277fc185
--- /dev/null
+++ b/sop-extras/changelog.d/20250130_111443_tdammers_mlocked_kes_rebase.md
@@ -0,0 +1,3 @@
+### Non-Breaking
+
+- Add `ctraverse`, `traverse_`, and `HTraverse_` to `OptNP`
diff --git a/sop-extras/src/Data/SOP/OptNP.hs b/sop-extras/src/Data/SOP/OptNP.hs
index 488967f471..15bc7b22b9 100644
--- a/sop-extras/src/Data/SOP/OptNP.hs
+++ b/sop-extras/src/Data/SOP/OptNP.hs
@@ -142,9 +142,28 @@ ctraverse' _ f = go
     go (OptSkip   xs) = OptSkip <$>         go xs
     go OptNil         = pure OptNil
 
+ctraverse_ ::
+     forall c proxy empty xs f g. (All c xs, Applicative g)
+  => proxy c -> (forall a. c a => f a -> g ()) -> OptNP empty f xs -> g ()
+ctraverse_ _ f = go
+  where
+    go :: All c ys => OptNP empty' f ys -> g ()
+    go (OptCons x xs) = f x *> go xs
+    go (OptSkip xs)   = go xs
+    go OptNil         = pure ()
+
+traverse_ ::
+     forall empty xs f g. (SListI xs, Applicative g)
+  => (forall a. f a -> g ()) -> OptNP empty f xs -> g ()
+traverse_ f = ctraverse_ (Proxy @Top) f
+
 instance HAp (OptNP empty) where
   hap = ap
 
+instance HTraverse_ (OptNP empty) where
+  hctraverse_ = ctraverse_
+  htraverse_ = traverse_
+
 instance HSequence (OptNP empty) where
   hctraverse' = ctraverse'
   htraverse'  = hctraverse' (Proxy @Top)