diff --git a/go.mod b/go.mod
index d27c803f..303799a6 100644
--- a/go.mod
+++ b/go.mod
@@ -9,10 +9,9 @@ require (
 	github.com/dogmatiq/configkit v0.14.0
 	github.com/dogmatiq/discoverkit v0.1.2
 	github.com/dogmatiq/dogma v0.14.3
-	github.com/dogmatiq/enginekit v0.12.0
+	github.com/dogmatiq/enginekit v0.12.1
 	github.com/dogmatiq/example v0.0.0-20240928215850-83b14743c287
 	github.com/dogmatiq/ferrite v1.4.0
-	github.com/dogmatiq/marshalkit v0.9.0
 	github.com/dogmatiq/persistencekit v0.10.0
 	github.com/dogmatiq/primo v0.3.1
 	github.com/dogmatiq/spruce v0.2.2
@@ -38,6 +37,7 @@ require (
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/mattn/go-runewidth v0.0.16 // indirect
+	github.com/onsi/ginkgo/v2 v2.20.2 // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
 	golang.org/x/net v0.29.0 // indirect
diff --git a/go.sum b/go.sum
index 4c21ef0d..d7a05e8e 100644
--- a/go.sum
+++ b/go.sum
@@ -14,8 +14,8 @@ github.com/dogmatiq/dogma v0.14.3 h1:qwZqU1yqp80toUJcJBdFxLlh6xvlFd7jb7rycmriRUo
 github.com/dogmatiq/dogma v0.14.3/go.mod h1:9lyVA+6V2+E/exV0IrBOrkUiyFwIATEhv+b0vnB2umQ=
 github.com/dogmatiq/dyad v1.0.0 h1:T50WQ9rAzCMcT941wVH5RW5+tAGRssuVlNog+ZMQR54=
 github.com/dogmatiq/dyad v1.0.0/go.mod h1:PrUQr7OCSEUjAkhi7ad8BjxFPKe0I9yP2f1kGimPcJE=
-github.com/dogmatiq/enginekit v0.12.0 h1:w16TGKVrvvfTejd6HJ2rhVQGZBW3TSK+o3heo7gTEog=
-github.com/dogmatiq/enginekit v0.12.0/go.mod h1:o0xikkm3INnWBjIXvJ9LffjdYRhIG3jwFNDyhTk1hcI=
+github.com/dogmatiq/enginekit v0.12.1 h1:EcW7LPWTer+notttjwkCCsjlywaRg8r/MWbfaKgZe1g=
+github.com/dogmatiq/enginekit v0.12.1/go.mod h1:aMBlieoE3An8SVW3vxUcxOOAVaz5Pxc9BPY37Jdg9M0=
 github.com/dogmatiq/example v0.0.0-20240928215850-83b14743c287 h1:MS/wfudIjXb0vFiALKpS1IZmNMu9AoDzdghrjqB4vPI=
 github.com/dogmatiq/example v0.0.0-20240928215850-83b14743c287/go.mod h1:T/G0HRH6OSo5cIIH31dLBYZiFjsL8RQsaN2vv8XjoTw=
 github.com/dogmatiq/ferrite v1.4.0 h1:cXmorC8NdSieWhPBfgmnj4cmWIeaCQK2sflGa2H0xXY=
@@ -28,8 +28,6 @@ github.com/dogmatiq/jumble v0.1.0 h1:Cb3ExfxY+AoUP4G9/sOwoOdYX8o+kOLK8+dhXAry+QA
 github.com/dogmatiq/jumble v0.1.0/go.mod h1:FCGV2ImXu8zvThxhd4QLstiEdu74vbIVw9bFJSBcKr4=
 github.com/dogmatiq/linger v1.1.0 h1:kGL9sL79qRa6Cr8PhadeJ/ptbum+b48pAaNWWlyVVKg=
 github.com/dogmatiq/linger v1.1.0/go.mod h1:OOWJUwTxNkFolhuVdaTYjO4FmFLjZHZ8EMc5H5qOJ7Q=
-github.com/dogmatiq/marshalkit v0.9.0 h1:YjBYoxRCSfLyRc5SUIDoCX0DTZ/RRCUkiUKEM49iINQ=
-github.com/dogmatiq/marshalkit v0.9.0/go.mod h1:dQ4yRVYT6FhAF+DOPwUh4wqcqmzbpGITluPeH1stpA0=
 github.com/dogmatiq/persistencekit v0.10.0 h1:i87Bv0riDAxDWrCqxyGIqzpymEHeL7WmBaKGXflihWc=
 github.com/dogmatiq/persistencekit v0.10.0/go.mod h1:F2M0TCqf/mkH5Nno1aILZfiR00I4LDQg/BE9s01qXfc=
 github.com/dogmatiq/primo v0.3.1 h1:JSqiCh1ma9CbIVzPf8k1vhzQ2Zn/d/WupzElDoiYZw0=
@@ -88,8 +86,6 @@ github.com/jackc/pgtype v1.14.0 h1:y+xUdabmyMkJLyApYuPj38mW+aAIqCe5uuBB51rH3Vw=
 github.com/jackc/pgtype v1.14.0/go.mod h1:LUMuVrfsFfdKGLw+AFFVv6KtHOFMwRgDDzBt76IqCA4=
 github.com/jackc/pgx/v4 v4.18.3 h1:dE2/TrEsGX3RBprb3qryqSV9Y60iZN1C6i8IrmW9/BA=
 github.com/jackc/pgx/v4 v4.18.3/go.mod h1:Ey4Oru5tH5sB6tV7hDmfWFahwF15Eb7DNXlRKx2CkVw=
-github.com/jmalloc/gomegax v0.0.0-20200507221434-64fca4c0e03a h1:Gk7Gkwl1KUJII/FiAjvBjRgEz/lpvTV8kNYp+9jdpuk=
-github.com/jmalloc/gomegax v0.0.0-20200507221434-64fca4c0e03a/go.mod h1:TZpc8ObQEKqTuy1/VXpPRfcMU80QFDU4zK3nchXts/k=
 github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
diff --git a/internal/engineconfig/app.go b/internal/engineconfig/app.go
index 9c20950d..2b79c75f 100644
--- a/internal/engineconfig/app.go
+++ b/internal/engineconfig/app.go
@@ -6,21 +6,20 @@ import (
 
 	"github.com/dogmatiq/configkit"
 	"github.com/dogmatiq/dogma"
+	"github.com/dogmatiq/enginekit/marshaler"
+	"github.com/dogmatiq/enginekit/marshaler/codecs/json"
+	"github.com/dogmatiq/enginekit/marshaler/codecs/protobuf"
+	"github.com/dogmatiq/enginekit/protobuf/envelopepb"
 	"github.com/dogmatiq/enginekit/protobuf/identitypb"
 	"github.com/dogmatiq/enginekit/protobuf/uuidpb"
-	"github.com/dogmatiq/marshalkit"
-	"github.com/dogmatiq/marshalkit/codec"
-	"github.com/dogmatiq/marshalkit/codec/json"
-	"github.com/dogmatiq/marshalkit/codec/protobuf"
-	"github.com/dogmatiq/veracity/internal/envelope"
 	"github.com/dogmatiq/veracity/internal/integration"
 )
 
 type applicationVisitor struct {
 	*Config
 
-	marshaler marshalkit.ValueMarshaler
-	packer    *envelope.Packer
+	marshaler marshaler.Marshaler
+	packer    *envelopepb.Packer
 }
 
 func (c applicationVisitor) VisitRichApplication(ctx context.Context, cfg configkit.RichApplication) error {
@@ -29,9 +28,9 @@ func (c applicationVisitor) VisitRichApplication(ctx context.Context, cfg config
 		types = append(types, t.ReflectType())
 	}
 
-	m, err := codec.NewMarshaler(
+	m, err := marshaler.New(
 		types,
-		[]codec.Codec{
+		[]marshaler.Codec{
 			protobuf.DefaultNativeCodec,
 			json.DefaultCodec,
 		},
@@ -42,7 +41,7 @@ func (c applicationVisitor) VisitRichApplication(ctx context.Context, cfg config
 
 	c.marshaler = m
 
-	c.packer = &envelope.Packer{
+	c.packer = &envelopepb.Packer{
 		Site:        c.SiteID,
 		Application: marshalIdentity(cfg.Identity()),
 		Marshaler:   c.marshaler,
@@ -90,7 +89,7 @@ func (c applicationVisitor) VisitRichProjection(context.Context, configkit.RichP
 }
 
 func marshalIdentity(id configkit.Identity) *identitypb.Identity {
-	key, err := uuidpb.FromString(id.Key)
+	key, err := uuidpb.Parse(id.Key)
 	if err != nil {
 		panic(err)
 	}
diff --git a/internal/engineconfig/cluster.go b/internal/engineconfig/cluster.go
index 267d1ca0..89cb588e 100644
--- a/internal/engineconfig/cluster.go
+++ b/internal/engineconfig/cluster.go
@@ -10,7 +10,7 @@ var nodeID = ferrite.
 	WithConstraint(
 		"must be a UUID",
 		func(v string) bool {
-			id, err := uuidpb.FromString(v)
+			id, err := uuidpb.Parse(v)
 			if err != nil {
 				return false
 			}
@@ -27,11 +27,7 @@ func (c *Config) finalizeNodeID() {
 
 	if c.UseEnv {
 		if v, ok := nodeID.Value(); ok {
-			id, err := uuidpb.FromString(v)
-			if err != nil {
-				panic(err)
-			}
-			c.NodeID = id
+			c.NodeID = uuidpb.MustParse(v)
 			return
 		}
 	}
diff --git a/internal/envelope/doc.go b/internal/envelope/doc.go
deleted file mode 100644
index 95f5fa61..00000000
--- a/internal/envelope/doc.go
+++ /dev/null
@@ -1,2 +0,0 @@
-// Package envelope contains tools for working with message envelopes.
-package envelope
diff --git a/internal/envelope/packer.go b/internal/envelope/packer.go
deleted file mode 100644
index 7956247f..00000000
--- a/internal/envelope/packer.go
+++ /dev/null
@@ -1,155 +0,0 @@
-package envelope
-
-import (
-	"fmt"
-	"time"
-
-	"github.com/dogmatiq/dogma"
-	"github.com/dogmatiq/enginekit/protobuf/envelopepb"
-	"github.com/dogmatiq/enginekit/protobuf/identitypb"
-	"github.com/dogmatiq/enginekit/protobuf/uuidpb"
-	"github.com/dogmatiq/marshalkit"
-	"google.golang.org/protobuf/types/known/timestamppb"
-)
-
-// A Packer puts messages into envelopes.
-type Packer struct {
-	// Site is the (optional) identity of the site that the source application
-	// is running within.
-	//
-	// The site is used to disambiguate between messages from different
-	// installations of the same application.
-	Site *identitypb.Identity
-
-	// Application is the identity of the application that is the source of the
-	// messages.
-	Application *identitypb.Identity
-
-	// Marshaler is used to marshal messages into envelopes.
-	Marshaler marshalkit.ValueMarshaler
-
-	// GenerateID is a function used to generate new message IDs. If it is nil,
-	// a UUID is generated.
-	GenerateID func() *uuidpb.UUID
-
-	// Now is a function used to get the current time. If it is nil, time.Now()
-	// is used.
-	Now func() time.Time
-}
-
-// Pack returns an envelope containing the given message.
-func (p *Packer) Pack(
-	m dogma.Message,
-	options ...PackOption,
-) *envelopepb.Envelope {
-	packet := marshalkit.MustMarshal(p.Marshaler, m)
-	_, name, err := packet.ParseMediaType()
-	if err != nil {
-		// CODE COVERAGE: This branch would require the marshaler to violate its
-		// own requirements on the format of the media-type.
-		panic(err)
-	}
-
-	id := p.generateID()
-
-	env := &envelopepb.Envelope{
-		MessageId:         id,
-		CorrelationId:     id,
-		CausationId:       id,
-		SourceSite:        p.Site,
-		SourceApplication: p.Application,
-		CreatedAt:         p.now(),
-		Description:       m.MessageDescription(),
-		PortableName:      name,
-		MediaType:         packet.MediaType,
-		Data:              packet.Data,
-	}
-
-	for _, opt := range options {
-		opt(env)
-	}
-
-	if err := env.Validate(); err != nil {
-		panic(err)
-	}
-
-	return env
-}
-
-// Unpack returns the message contained within an envelope.
-func (p *Packer) Unpack(env *envelopepb.Envelope) (dogma.Message, error) {
-	packet := marshalkit.Packet{
-		MediaType: env.MediaType,
-		Data:      env.Data,
-	}
-
-	m, err := p.Marshaler.Unmarshal(packet)
-	if err != nil {
-		return nil, err
-	}
-
-	if m, ok := m.(dogma.Message); ok {
-		return m, nil
-	}
-
-	return nil, fmt.Errorf("'%T' is not a dogma message", m)
-}
-
-// now returns the current time.
-func (p *Packer) now() *timestamppb.Timestamp {
-	if p.Now == nil {
-		return timestamppb.Now()
-	}
-
-	return timestamppb.New(p.Now())
-}
-
-// generateID generates a new message ID.
-func (p *Packer) generateID() *uuidpb.UUID {
-	if p.GenerateID != nil {
-		return p.GenerateID()
-	}
-
-	return uuidpb.Generate()
-}
-
-// PackOption is an option that alters the behavior of a Pack operation.
-type PackOption func(*envelopepb.Envelope)
-
-// WithCause sets env as the "cause" of the message being packed.
-func WithCause(env *envelopepb.Envelope) PackOption {
-	return func(e *envelopepb.Envelope) {
-		e.CausationId = env.MessageId
-		e.CorrelationId = env.CorrelationId
-	}
-}
-
-// WithHandler sets h as the identity of the handler that is the source of the
-// message.
-func WithHandler(h *identitypb.Identity) PackOption {
-	return func(e *envelopepb.Envelope) {
-		e.SourceHandler = h
-	}
-}
-
-// WithInstanceID sets the aggregate or process instance ID that is the
-// source of the message.
-func WithInstanceID(id string) PackOption {
-	return func(e *envelopepb.Envelope) {
-		e.SourceInstanceId = id
-	}
-}
-
-// WithCreatedAt sets the creation time of a message.
-func WithCreatedAt(t time.Time) PackOption {
-	return func(e *envelopepb.Envelope) {
-		e.CreatedAt = timestamppb.New(t)
-	}
-}
-
-// WithScheduledFor sets the scheduled time of a timeout message.
-func WithScheduledFor(t time.Time) PackOption {
-	return func(e *envelopepb.Envelope) {
-		e.ScheduledFor = timestamppb.New(t)
-	}
-}
diff --git a/internal/envelope/transcoder.go b/internal/envelope/transcoder.go
deleted file mode 100644
index f1c3f90b..00000000
--- a/internal/envelope/transcoder.go
+++ /dev/null
@@ -1,55 +0,0 @@
-package envelope
-
-import (
-	"strings"
-
-	"github.com/dogmatiq/enginekit/protobuf/envelopepb"
-	"github.com/dogmatiq/marshalkit"
-	"google.golang.org/protobuf/proto"
-)
-
-// Transcoder re-encodes messages to different media-types on the fly.
-type Transcoder struct {
-	// MediaTypes is a map of the message's "portable name" to a list of
-	// supported media-types, in order of preference.
-	MediaTypes map[string][]string
-
-	// Marshaler is the marshaler to use to unmarshal and marshal messages.
-	Marshaler marshalkit.Marshaler
-}
-
-// Transcode re-encodes the message in env to one of the supported media-types.
-func (t *Transcoder) Transcode(env *envelopepb.Envelope) (*envelopepb.Envelope, bool, error) {
-	candidates := t.MediaTypes[env.PortableName]
-
-	// If the existing encoding is supported by the consumer use the envelope
-	// without any re-encoding.
-	for _, candidate := range candidates {
-		if strings.EqualFold(env.MediaType, candidate) {
-			return env, true, nil
-		}
-	}
-
-	packet := marshalkit.Packet{
-		MediaType: env.MediaType,
-		Data:      env.Data,
-	}
-
-	m, err := t.Marshaler.Unmarshal(packet)
-	if err != nil {
-		return nil, false, err
-	}
-
-	// Otherwise, attempt to marshal the message using the client's requested
-	// media-types in order of preference.
-	packet, ok, err := t.Marshaler.MarshalAs(m, candidates)
-	if !ok || err != nil {
-		return nil, ok, err
-	}
-
-	env = proto.Clone(env).(*envelopepb.Envelope)
-	env.MediaType = packet.MediaType
-	env.Data = packet.Data
-
-	return env, true, nil
-}
diff --git a/internal/eventstream/append_test.go b/internal/eventstream/append_test.go
index 10881974..c1f9517a 100644
--- a/internal/eventstream/append_test.go
+++ b/internal/eventstream/append_test.go
@@ -9,11 +9,9 @@ import (
 	"github.com/dogmatiq/enginekit/protobuf/envelopepb"
 	"github.com/dogmatiq/enginekit/protobuf/identitypb"
 	"github.com/dogmatiq/enginekit/protobuf/uuidpb"
-	. "github.com/dogmatiq/marshalkit/fixtures"
 	"github.com/dogmatiq/persistencekit/driver/memory/memoryjournal"
 	"github.com/dogmatiq/persistencekit/journal"
 	"github.com/dogmatiq/spruce"
-	"github.com/dogmatiq/veracity/internal/envelope"
 	. "github.com/dogmatiq/veracity/internal/eventstream"
 	"github.com/dogmatiq/veracity/internal/eventstream/internal/eventstreamjournal"
 	"github.com/dogmatiq/veracity/internal/test"
@@ -25,7 +23,7 @@ func TestAppend(t *testing.T) {
 	type dependencies struct {
 		Journals   *memoryjournal.BinaryStore
 		Supervisor *Supervisor
-		Packer     *envelope.Packer
+		Packer     *envelopepb.Packer
 	}
 
 	setup := func(t test.TestingT) (deps dependencies) {
@@ -36,7 +34,7 @@ func TestAppend(t *testing.T) {
 			Logger:   spruce.NewTestLogger(t),
 		}
 
-		deps.Packer = &envelope.Packer{
+		deps.Packer = &envelopepb.Packer{
 			Application: identitypb.New("<app>", uuidpb.Generate()),
 			Marshaler:   Marshaler,
 		}
diff --git a/internal/integration/executor.go b/internal/integration/executor.go
index afef29b4..e46eceeb 100644
--- a/internal/integration/executor.go
+++ b/internal/integration/executor.go
@@ -4,7 +4,7 @@ import (
 	"context"
 
 	"github.com/dogmatiq/dogma"
-	"github.com/dogmatiq/veracity/internal/envelope"
+	"github.com/dogmatiq/enginekit/protobuf/envelopepb"
 	"github.com/dogmatiq/veracity/internal/messaging"
 )
 
@@ -12,7 +12,7 @@ import (
 // dispatches the command to an exchange queue.
 type CommandExecutor struct {
 	ExecuteQueue *messaging.ExchangeQueue[ExecuteRequest, ExecuteResponse]
-	Packer       *envelope.Packer
+	Packer       *envelopepb.Packer
 }
 
 // ExecuteCommand enqueues a command.
diff --git a/internal/integration/packer_test.go b/internal/integration/packer_test.go
index 46b4bfe6..0a054972 100644
--- a/internal/integration/packer_test.go
+++ b/internal/integration/packer_test.go
@@ -4,15 +4,15 @@ import (
 	"sync/atomic"
 	"time"
 
+	. "github.com/dogmatiq/enginekit/enginetest/stubs"
+	"github.com/dogmatiq/enginekit/protobuf/envelopepb"
 	"github.com/dogmatiq/enginekit/protobuf/identitypb"
 	"github.com/dogmatiq/enginekit/protobuf/uuidpb"
-	. "github.com/dogmatiq/marshalkit/fixtures"
-	"github.com/dogmatiq/veracity/internal/envelope"
 )
 
-func newPacker() *envelope.Packer {
+func newPacker() *envelopepb.Packer {
 	var counter atomic.Uint64
-	return &envelope.Packer{
+	return &envelopepb.Packer{
 		Application: identitypb.New("<app>", uuidpb.Generate()),
 		Marshaler:   Marshaler,
 		Now: func() time.Time {
diff --git a/internal/integration/supervisor.go b/internal/integration/supervisor.go
index f650b6f4..e8852c2b 100644
--- a/internal/integration/supervisor.go
+++ b/internal/integration/supervisor.go
@@ -10,7 +10,6 @@ import (
 	"github.com/dogmatiq/enginekit/protobuf/uuidpb"
 	"github.com/dogmatiq/persistencekit/journal"
 	"github.com/dogmatiq/persistencekit/kv"
-	"github.com/dogmatiq/veracity/internal/envelope"
 	"github.com/dogmatiq/veracity/internal/eventstream"
 	"github.com/dogmatiq/veracity/internal/fsm"
 	"github.com/dogmatiq/veracity/internal/integration/internal/integrationjournal"
@@ -36,7 +35,7 @@ type Supervisor struct {
 	HandlerIdentity *identitypb.Identity
 	Journals        journal.BinaryStore
 	Keyspaces       kv.BinaryStore
-	Packer          *envelope.Packer
+	Packer          *envelopepb.Packer
 	EventRecorder   EventRecorder
 
 	eventStreamID             *uuidpb.UUID
@@ -184,7 +183,14 @@ func (s *Supervisor) handleCommand(ctx context.Context, cmd *envelopepb.Envelope
 
 	var envs []*envelopepb.Envelope
 	for _, ev := range sc.evs {
-		envs = append(envs, s.Packer.Pack(ev, envelope.WithCause(cmd), envelope.WithHandler(s.HandlerIdentity)))
+		envs = append(
+			envs,
+			s.Packer.Pack(
+				ev,
+				envelopepb.WithCause(cmd),
+				envelopepb.WithHandler(s.HandlerIdentity),
+			),
+		)
 	}
 
 	if s.eventStreamID == nil {
diff --git a/internal/integration/supervisor_test.go b/internal/integration/supervisor_test.go
index 7eeab055..553a10e9 100644
--- a/internal/integration/supervisor_test.go
+++ b/internal/integration/supervisor_test.go
@@ -16,7 +16,6 @@ import (
 	"github.com/dogmatiq/enginekit/protobuf/uuidpb"
 	"github.com/dogmatiq/persistencekit/driver/memory/memoryjournal"
 	"github.com/dogmatiq/persistencekit/driver/memory/memorykv"
-	"github.com/dogmatiq/veracity/internal/envelope"
 	"github.com/dogmatiq/veracity/internal/eventstream"
 	. "github.com/dogmatiq/veracity/internal/integration"
 	"github.com/dogmatiq/veracity/internal/integration/internal/integrationjournal"
@@ -28,7 +27,7 @@ import (
 
 func TestSupervisor(t *testing.T) {
 	type dependencies struct {
-		Packer        *envelope.Packer
+		Packer        *envelopepb.Packer
 		Journals      *memoryjournal.BinaryStore
 		Keyspaces     *memorykv.BinaryStore
 		Handler       *IntegrationMessageHandlerStub