diff --git a/capability.go b/capability.go
index cdc39146..4831324c 100644
--- a/capability.go
+++ b/capability.go
@@ -21,6 +21,15 @@ type Interface struct {
 	cap CapabilityID
 }
 
+// i.EncodeAsPtr is equivalent to i.ToPtr(); for implementing TypeParam.
+// The segment argument is ignored.
+func (i Interface) EncodeAsPtr(*Segment) Ptr { return i.ToPtr() }
+
+// DecodeFromPtr(p) is equivalent to p.Interface(); for implementing TypeParam.
+func (Interface) DecodeFromPtr(p Ptr) Interface { return p.Interface() }
+
+var _ TypeParam[Interface] = Interface{}
+
 // NewInterface creates a new interface pointer.
 //
 // No allocation is performed in the given segment: it is used purely
@@ -572,6 +581,18 @@ func (c Client) Release() {
 	h.Shutdown()
 }
 
+func (c Client) EncodeAsPtr(seg *Segment) Ptr {
+	capId := seg.Message().AddCap(c)
+	return NewInterface(seg, capId).ToPtr()
+}
+
+func (Client) DecodeFromPtr(p Ptr) Client {
+	return p.Interface().Client()
+}
+
+var _ TypeParam[Client] = Client{}
+
+
 // isResolve reports whether ch has been resolved.
 // The caller must be holding onto ch.mu.
 func (ch *clientHook) isResolved() bool {
diff --git a/capnpc-go/templates/baseStructFuncs b/capnpc-go/templates/baseStructFuncs
index a4f23ec2..edc0dbd1 100644
--- a/capnpc-go/templates/baseStructFuncs
+++ b/capnpc-go/templates/baseStructFuncs
@@ -21,3 +21,6 @@ func (s {{.Node.Name}}) String() string {
 }
 {{end}}
 
+func ({{.Node.Name}}) DecodeFromPtr(p {{.G.Capnp}}.Ptr) {{.Node.Name}} {
+	return {{.Node.Name}}{ Struct: {{.G.Capnp}}.Struct{}.DecodeFromPtr(p) }
+}
diff --git a/capnpc-go/templates/interfaceClient b/capnpc-go/templates/interfaceClient
index 60e5d11f..14ef4072 100644
--- a/capnpc-go/templates/interfaceClient
+++ b/capnpc-go/templates/interfaceClient
@@ -26,3 +26,7 @@ func (c {{$.Node.Name}}) AddRef() {{$.Node.Name}} {
 		Client: c.Client.AddRef(),
 	}
 }
+
+func ({{$.Node.Name}}) DecodeFromPtr(p {{.G.Capnp}}.Ptr) {{$.Node.Name}} {
+	return {{$.Node.Name}}{ Client: {{.G.Capnp}}.Client{}.DecodeFromPtr(p) }
+}
diff --git a/internal/aircraftlib/aircraft.capnp.go b/internal/aircraftlib/aircraft.capnp.go
index 5b8d0c53..6ce45ee8 100644
--- a/internal/aircraftlib/aircraft.capnp.go
+++ b/internal/aircraftlib/aircraft.capnp.go
@@ -48,6 +48,9 @@ func (s Zdate) String() string {
 	return str
 }
 
+func (Zdate) DecodeFromPtr(p capnp.Ptr) Zdate {
+	return Zdate{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Zdate) Year() int16 {
 	return int16(s.Struct.Uint16(0))
 }
@@ -114,6 +117,9 @@ func (s Zdata) String() string {
 	return str
 }
 
+func (Zdata) DecodeFromPtr(p capnp.Ptr) Zdata {
+	return Zdata{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Zdata) Data() ([]byte, error) {
 	p, err := s.Struct.Ptr(0)
 	return []byte(p.Data()), err
@@ -238,6 +244,9 @@ func (s PlaneBase) String() string {
 	return str
 }
 
+func (PlaneBase) DecodeFromPtr(p capnp.Ptr) PlaneBase {
+	return PlaneBase{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s PlaneBase) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -354,6 +363,9 @@ func (s B737) String() string {
 	return str
 }
 
+func (B737) DecodeFromPtr(p capnp.Ptr) B737 {
+	return B737{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s B737) Base() (PlaneBase, error) {
 	p, err := s.Struct.Ptr(0)
 	return PlaneBase{Struct: p.Struct()}, err
@@ -424,6 +436,9 @@ func (s A320) String() string {
 	return str
 }
 
+func (A320) DecodeFromPtr(p capnp.Ptr) A320 {
+	return A320{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s A320) Base() (PlaneBase, error) {
 	p, err := s.Struct.Ptr(0)
 	return PlaneBase{Struct: p.Struct()}, err
@@ -494,6 +509,9 @@ func (s F16) String() string {
 	return str
 }
 
+func (F16) DecodeFromPtr(p capnp.Ptr) F16 {
+	return F16{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s F16) Base() (PlaneBase, error) {
 	p, err := s.Struct.Ptr(0)
 	return PlaneBase{Struct: p.Struct()}, err
@@ -564,6 +582,9 @@ func (s Regression) String() string {
 	return str
 }
 
+func (Regression) DecodeFromPtr(p capnp.Ptr) Regression {
+	return Regression{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Regression) Base() (PlaneBase, error) {
 	p, err := s.Struct.Ptr(0)
 	return PlaneBase{Struct: p.Struct()}, err
@@ -730,6 +751,10 @@ func (s Aircraft) String() string {
 	return str
 }
 
+func (Aircraft) DecodeFromPtr(p capnp.Ptr) Aircraft {
+	return Aircraft{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Aircraft) Which() Aircraft_Which {
 	return Aircraft_Which(s.Struct.Uint16(0))
 }
@@ -1048,6 +1073,10 @@ func (s Z) String() string {
 	return str
 }
 
+func (Z) DecodeFromPtr(p capnp.Ptr) Z {
+	return Z{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Z) Which() Z_Which {
 	return Z_Which(s.Struct.Uint16(0))
 }
@@ -2378,6 +2407,9 @@ func (s Counter) String() string {
 	return str
 }
 
+func (Counter) DecodeFromPtr(p capnp.Ptr) Counter {
+	return Counter{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Counter) Size() int64 {
 	return int64(s.Struct.Uint64(0))
 }
@@ -2494,6 +2526,9 @@ func (s Bag) String() string {
 	return str
 }
 
+func (Bag) DecodeFromPtr(p capnp.Ptr) Bag {
+	return Bag{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Bag) Counter() (Counter, error) {
 	p, err := s.Struct.Ptr(0)
 	return Counter{Struct: p.Struct()}, err
@@ -2564,6 +2599,9 @@ func (s Zserver) String() string {
 	return str
 }
 
+func (Zserver) DecodeFromPtr(p capnp.Ptr) Zserver {
+	return Zserver{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Zserver) Waitingjobs() (Zjob_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return Zjob_List{List: p.List()}, err
@@ -2630,6 +2668,9 @@ func (s Zjob) String() string {
 	return str
 }
 
+func (Zjob) DecodeFromPtr(p capnp.Ptr) Zjob {
+	return Zjob{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Zjob) Cmd() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -2714,6 +2755,10 @@ func (s VerEmpty) String() string {
 	return str
 }
 
+func (VerEmpty) DecodeFromPtr(p capnp.Ptr) VerEmpty {
+	return VerEmpty{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 // VerEmpty_List is a list of VerEmpty.
 type VerEmpty_List = capnp.StructList[VerEmpty]
 
@@ -2756,6 +2801,9 @@ func (s VerOneData) String() string {
 	return str
 }
 
+func (VerOneData) DecodeFromPtr(p capnp.Ptr) VerOneData {
+	return VerOneData{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s VerOneData) Val() int16 {
 	return int16(s.Struct.Uint16(0))
 }
@@ -2806,6 +2854,9 @@ func (s VerTwoData) String() string {
 	return str
 }
 
+func (VerTwoData) DecodeFromPtr(p capnp.Ptr) VerTwoData {
+	return VerTwoData{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s VerTwoData) Val() int16 {
 	return int16(s.Struct.Uint16(0))
 }
@@ -2864,6 +2915,9 @@ func (s VerOnePtr) String() string {
 	return str
 }
 
+func (VerOnePtr) DecodeFromPtr(p capnp.Ptr) VerOnePtr {
+	return VerOnePtr{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s VerOnePtr) Ptr() (VerOneData, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerOneData{Struct: p.Struct()}, err
@@ -2934,6 +2988,9 @@ func (s VerTwoPtr) String() string {
 	return str
 }
 
+func (VerTwoPtr) DecodeFromPtr(p capnp.Ptr) VerTwoPtr {
+	return VerTwoPtr{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s VerTwoPtr) Ptr1() (VerOneData, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerOneData{Struct: p.Struct()}, err
@@ -3032,6 +3089,9 @@ func (s VerTwoDataTwoPtr) String() string {
 	return str
 }
 
+func (VerTwoDataTwoPtr) DecodeFromPtr(p capnp.Ptr) VerTwoDataTwoPtr {
+	return VerTwoDataTwoPtr{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s VerTwoDataTwoPtr) Val() int16 {
 	return int16(s.Struct.Uint16(0))
 }
@@ -3146,6 +3206,9 @@ func (s HoldsVerEmptyList) String() string {
 	return str
 }
 
+func (HoldsVerEmptyList) DecodeFromPtr(p capnp.Ptr) HoldsVerEmptyList {
+	return HoldsVerEmptyList{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s HoldsVerEmptyList) Mylist() (VerEmpty_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerEmpty_List{List: p.List()}, err
@@ -3212,6 +3275,9 @@ func (s HoldsVerOneDataList) String() string {
 	return str
 }
 
+func (HoldsVerOneDataList) DecodeFromPtr(p capnp.Ptr) HoldsVerOneDataList {
+	return HoldsVerOneDataList{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s HoldsVerOneDataList) Mylist() (VerOneData_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerOneData_List{List: p.List()}, err
@@ -3278,6 +3344,9 @@ func (s HoldsVerTwoDataList) String() string {
 	return str
 }
 
+func (HoldsVerTwoDataList) DecodeFromPtr(p capnp.Ptr) HoldsVerTwoDataList {
+	return HoldsVerTwoDataList{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s HoldsVerTwoDataList) Mylist() (VerTwoData_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerTwoData_List{List: p.List()}, err
@@ -3344,6 +3413,9 @@ func (s HoldsVerOnePtrList) String() string {
 	return str
 }
 
+func (HoldsVerOnePtrList) DecodeFromPtr(p capnp.Ptr) HoldsVerOnePtrList {
+	return HoldsVerOnePtrList{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s HoldsVerOnePtrList) Mylist() (VerOnePtr_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerOnePtr_List{List: p.List()}, err
@@ -3410,6 +3482,9 @@ func (s HoldsVerTwoPtrList) String() string {
 	return str
 }
 
+func (HoldsVerTwoPtrList) DecodeFromPtr(p capnp.Ptr) HoldsVerTwoPtrList {
+	return HoldsVerTwoPtrList{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s HoldsVerTwoPtrList) Mylist() (VerTwoPtr_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerTwoPtr_List{List: p.List()}, err
@@ -3476,6 +3551,9 @@ func (s HoldsVerTwoTwoList) String() string {
 	return str
 }
 
+func (HoldsVerTwoTwoList) DecodeFromPtr(p capnp.Ptr) HoldsVerTwoTwoList {
+	return HoldsVerTwoTwoList{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s HoldsVerTwoTwoList) Mylist() (VerTwoDataTwoPtr_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerTwoDataTwoPtr_List{List: p.List()}, err
@@ -3542,6 +3620,9 @@ func (s HoldsVerTwoTwoPlus) String() string {
 	return str
 }
 
+func (HoldsVerTwoTwoPlus) DecodeFromPtr(p capnp.Ptr) HoldsVerTwoTwoPlus {
+	return HoldsVerTwoTwoPlus{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s HoldsVerTwoTwoPlus) Mylist() (VerTwoTwoPlus_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerTwoTwoPlus_List{List: p.List()}, err
@@ -3608,6 +3689,9 @@ func (s VerTwoTwoPlus) String() string {
 	return str
 }
 
+func (VerTwoTwoPlus) DecodeFromPtr(p capnp.Ptr) VerTwoTwoPlus {
+	return VerTwoTwoPlus{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s VerTwoTwoPlus) Val() int16 {
 	return int16(s.Struct.Uint16(0))
 }
@@ -3754,6 +3838,9 @@ func (s HoldsText) String() string {
 	return str
 }
 
+func (HoldsText) DecodeFromPtr(p capnp.Ptr) HoldsText {
+	return HoldsText{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s HoldsText) Txt() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -3862,6 +3949,9 @@ func (s WrapEmpty) String() string {
 	return str
 }
 
+func (WrapEmpty) DecodeFromPtr(p capnp.Ptr) WrapEmpty {
+	return WrapEmpty{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s WrapEmpty) MightNotBeReallyEmpty() (VerEmpty, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerEmpty{Struct: p.Struct()}, err
@@ -3932,6 +4022,9 @@ func (s Wrap2x2) String() string {
 	return str
 }
 
+func (Wrap2x2) DecodeFromPtr(p capnp.Ptr) Wrap2x2 {
+	return Wrap2x2{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Wrap2x2) MightNotBeReallyEmpty() (VerTwoDataTwoPtr, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerTwoDataTwoPtr{Struct: p.Struct()}, err
@@ -4002,6 +4095,9 @@ func (s Wrap2x2plus) String() string {
 	return str
 }
 
+func (Wrap2x2plus) DecodeFromPtr(p capnp.Ptr) Wrap2x2plus {
+	return Wrap2x2plus{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Wrap2x2plus) MightNotBeReallyEmpty() (VerTwoTwoPlus, error) {
 	p, err := s.Struct.Ptr(0)
 	return VerTwoTwoPlus{Struct: p.Struct()}, err
@@ -4090,6 +4186,10 @@ func (s VoidUnion) String() string {
 	return str
 }
 
+func (VoidUnion) DecodeFromPtr(p capnp.Ptr) VoidUnion {
+	return VoidUnion{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s VoidUnion) Which() VoidUnion_Which {
 	return VoidUnion_Which(s.Struct.Uint16(0))
 }
@@ -4145,6 +4245,9 @@ func (s Nester1Capn) String() string {
 	return str
 }
 
+func (Nester1Capn) DecodeFromPtr(p capnp.Ptr) Nester1Capn {
+	return Nester1Capn{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Nester1Capn) Strs() (capnp.TextList, error) {
 	p, err := s.Struct.Ptr(0)
 	return capnp.TextList{List: p.List()}, err
@@ -4211,6 +4314,9 @@ func (s RWTestCapn) String() string {
 	return str
 }
 
+func (RWTestCapn) DecodeFromPtr(p capnp.Ptr) RWTestCapn {
+	return RWTestCapn{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s RWTestCapn) NestMatrix() (capnp.PointerList, error) {
 	p, err := s.Struct.Ptr(0)
 	return capnp.PointerList{List: p.List()}, err
@@ -4277,6 +4383,9 @@ func (s ListStructCapn) String() string {
 	return str
 }
 
+func (ListStructCapn) DecodeFromPtr(p capnp.Ptr) ListStructCapn {
+	return ListStructCapn{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s ListStructCapn) Vec() (Nester1Capn_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return Nester1Capn_List{List: p.List()}, err
@@ -4346,6 +4455,10 @@ func (c Echo) AddRef() Echo {
 	}
 }
 
+func (Echo) DecodeFromPtr(p capnp.Ptr) Echo {
+	return Echo{Client: capnp.Client{}.DecodeFromPtr(p)}
+}
+
 // A Echo_Server is a Echo with a local implementation.
 type Echo_Server interface {
 	Echo(context.Context, Echo_echo) error
@@ -4436,6 +4549,9 @@ func (s Echo_echo_Params) String() string {
 	return str
 }
 
+func (Echo_echo_Params) DecodeFromPtr(p capnp.Ptr) Echo_echo_Params {
+	return Echo_echo_Params{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Echo_echo_Params) In() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -4496,6 +4612,9 @@ func (s Echo_echo_Results) String() string {
 	return str
 }
 
+func (Echo_echo_Results) DecodeFromPtr(p capnp.Ptr) Echo_echo_Results {
+	return Echo_echo_Results{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Echo_echo_Results) Out() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -4556,6 +4675,9 @@ func (s Hoth) String() string {
 	return str
 }
 
+func (Hoth) DecodeFromPtr(p capnp.Ptr) Hoth {
+	return Hoth{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Hoth) Base() (EchoBase, error) {
 	p, err := s.Struct.Ptr(0)
 	return EchoBase{Struct: p.Struct()}, err
@@ -4626,6 +4748,9 @@ func (s EchoBase) String() string {
 	return str
 }
 
+func (EchoBase) DecodeFromPtr(p capnp.Ptr) EchoBase {
+	return EchoBase{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s EchoBase) Echo() Echo {
 	p, _ := s.Struct.Ptr(0)
 	return Echo{Client: p.Interface().Client()}
@@ -4690,6 +4815,9 @@ func (s StackingRoot) String() string {
 	return str
 }
 
+func (StackingRoot) DecodeFromPtr(p capnp.Ptr) StackingRoot {
+	return StackingRoot{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s StackingRoot) A() (StackingA, error) {
 	p, err := s.Struct.Ptr(1)
 	return StackingA{Struct: p.Struct()}, err
@@ -4792,6 +4920,9 @@ func (s StackingA) String() string {
 	return str
 }
 
+func (StackingA) DecodeFromPtr(p capnp.Ptr) StackingA {
+	return StackingA{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s StackingA) Num() int32 {
 	return int32(s.Struct.Uint32(0))
 }
@@ -4870,6 +5001,9 @@ func (s StackingB) String() string {
 	return str
 }
 
+func (StackingB) DecodeFromPtr(p capnp.Ptr) StackingB {
+	return StackingB{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s StackingB) Num() int32 {
 	return int32(s.Struct.Uint32(0))
 }
@@ -4923,6 +5057,10 @@ func (c CallSequence) AddRef() CallSequence {
 	}
 }
 
+func (CallSequence) DecodeFromPtr(p capnp.Ptr) CallSequence {
+	return CallSequence{Client: capnp.Client{}.DecodeFromPtr(p)}
+}
+
 // A CallSequence_Server is a CallSequence with a local implementation.
 type CallSequence_Server interface {
 	GetNumber(context.Context, CallSequence_getNumber) error
@@ -5013,6 +5151,10 @@ func (s CallSequence_getNumber_Params) String() string {
 	return str
 }
 
+func (CallSequence_getNumber_Params) DecodeFromPtr(p capnp.Ptr) CallSequence_getNumber_Params {
+	return CallSequence_getNumber_Params{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 // CallSequence_getNumber_Params_List is a list of CallSequence_getNumber_Params.
 type CallSequence_getNumber_Params_List = capnp.StructList[CallSequence_getNumber_Params]
 
@@ -5055,6 +5197,9 @@ func (s CallSequence_getNumber_Results) String() string {
 	return str
 }
 
+func (CallSequence_getNumber_Results) DecodeFromPtr(p capnp.Ptr) CallSequence_getNumber_Results {
+	return CallSequence_getNumber_Results{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s CallSequence_getNumber_Results) N() uint32 {
 	return s.Struct.Uint32(0)
 }
@@ -5124,6 +5269,10 @@ func (c Pipeliner) AddRef() Pipeliner {
 	}
 }
 
+func (Pipeliner) DecodeFromPtr(p capnp.Ptr) Pipeliner {
+	return Pipeliner{Client: capnp.Client{}.DecodeFromPtr(p)}
+}
+
 // A Pipeliner_Server is a Pipeliner with a local implementation.
 type Pipeliner_Server interface {
 	NewPipeliner(context.Context, Pipeliner_newPipeliner) error
@@ -5228,6 +5377,10 @@ func (s Pipeliner_newPipeliner_Params) String() string {
 	return str
 }
 
+func (Pipeliner_newPipeliner_Params) DecodeFromPtr(p capnp.Ptr) Pipeliner_newPipeliner_Params {
+	return Pipeliner_newPipeliner_Params{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 // Pipeliner_newPipeliner_Params_List is a list of Pipeliner_newPipeliner_Params.
 type Pipeliner_newPipeliner_Params_List = capnp.StructList[Pipeliner_newPipeliner_Params]
 
@@ -5270,6 +5423,9 @@ func (s Pipeliner_newPipeliner_Results) String() string {
 	return str
 }
 
+func (Pipeliner_newPipeliner_Results) DecodeFromPtr(p capnp.Ptr) Pipeliner_newPipeliner_Results {
+	return Pipeliner_newPipeliner_Results{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Pipeliner_newPipeliner_Results) Extra() (capnp.Ptr, error) {
 	return s.Struct.Ptr(0)
 }
@@ -5350,6 +5506,9 @@ func (s Defaults) String() string {
 	return str
 }
 
+func (Defaults) DecodeFromPtr(p capnp.Ptr) Defaults {
+	return Defaults{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Defaults) Text() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.TextDefault("foo"), err
@@ -5450,6 +5609,9 @@ func (s BenchmarkA) String() string {
 	return str
 }
 
+func (BenchmarkA) DecodeFromPtr(p capnp.Ptr) BenchmarkA {
+	return BenchmarkA{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s BenchmarkA) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -5560,6 +5722,9 @@ func (s AllocBenchmark) String() string {
 	return str
 }
 
+func (AllocBenchmark) DecodeFromPtr(p capnp.Ptr) AllocBenchmark {
+	return AllocBenchmark{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s AllocBenchmark) Fields() (AllocBenchmark_Field_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return AllocBenchmark_Field_List{List: p.List()}, err
@@ -5626,6 +5791,9 @@ func (s AllocBenchmark_Field) String() string {
 	return str
 }
 
+func (AllocBenchmark_Field) DecodeFromPtr(p capnp.Ptr) AllocBenchmark_Field {
+	return AllocBenchmark_Field{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s AllocBenchmark_Field) StringValue() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
diff --git a/internal/aircraftlib/aircraft_test.go b/internal/aircraftlib/aircraft_test.go
new file mode 100644
index 00000000..7c2eb50f
--- /dev/null
+++ b/internal/aircraftlib/aircraft_test.go
@@ -0,0 +1,17 @@
+package aircraftlib
+
+import (
+	"capnproto.org/go/capnp/v3"
+)
+
+var (
+	// Make sure interface types satisfy TypeParam:
+	_ capnp.TypeParam[Echo] = Echo{}
+
+	// ...and structs:
+	_ capnp.TypeParam[Zdate] = Zdate{}
+
+	// ...and lists:
+	_ capnp.TypeParam[Echo_List] = Echo_List{}
+	_ capnp.TypeParam[Zdate_List] = Zdate_List{}
+)
diff --git a/internal/demo/books/books.capnp.go b/internal/demo/books/books.capnp.go
index d980c5dc..b6a32edf 100644
--- a/internal/demo/books/books.capnp.go
+++ b/internal/demo/books/books.capnp.go
@@ -33,6 +33,9 @@ func (s Book) String() string {
 	return str
 }
 
+func (Book) DecodeFromPtr(p capnp.Ptr) Book {
+	return Book{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Book) Title() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
diff --git a/internal/schema/schema.capnp.go b/internal/schema/schema.capnp.go
index 3d312cc6..26f72f99 100644
--- a/internal/schema/schema.capnp.go
+++ b/internal/schema/schema.capnp.go
@@ -68,6 +68,10 @@ func ReadRootNode(msg *capnp.Message) (Node, error) {
 	return Node{root.Struct()}, err
 }
 
+func (Node) DecodeFromPtr(p capnp.Ptr) Node {
+	return Node{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Node) Which() Node_Which {
 	return Node_Which(s.Struct.Uint16(12))
 }
@@ -569,6 +573,9 @@ func ReadRootNode_Parameter(msg *capnp.Message) (Node_Parameter, error) {
 	return Node_Parameter{root.Struct()}, err
 }
 
+func (Node_Parameter) DecodeFromPtr(p capnp.Ptr) Node_Parameter {
+	return Node_Parameter{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Node_Parameter) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -616,6 +623,9 @@ func ReadRootNode_NestedNode(msg *capnp.Message) (Node_NestedNode, error) {
 	return Node_NestedNode{root.Struct()}, err
 }
 
+func (Node_NestedNode) DecodeFromPtr(p capnp.Ptr) Node_NestedNode {
+	return Node_NestedNode{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Node_NestedNode) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -671,6 +681,9 @@ func ReadRootNode_SourceInfo(msg *capnp.Message) (Node_SourceInfo, error) {
 	return Node_SourceInfo{root.Struct()}, err
 }
 
+func (Node_SourceInfo) DecodeFromPtr(p capnp.Ptr) Node_SourceInfo {
+	return Node_SourceInfo{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Node_SourceInfo) Id() uint64 {
 	return s.Struct.Uint64(0)
 }
@@ -750,6 +763,9 @@ func ReadRootNode_SourceInfo_Member(msg *capnp.Message) (Node_SourceInfo_Member,
 	return Node_SourceInfo_Member{root.Struct()}, err
 }
 
+func (Node_SourceInfo_Member) DecodeFromPtr(p capnp.Ptr) Node_SourceInfo_Member {
+	return Node_SourceInfo_Member{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Node_SourceInfo_Member) DocComment() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -837,6 +853,10 @@ func ReadRootField(msg *capnp.Message) (Field, error) {
 	return Field{root.Struct()}, err
 }
 
+func (Field) DecodeFromPtr(p capnp.Ptr) Field {
+	return Field{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Field) Which() Field_Which {
 	return Field_Which(s.Struct.Uint16(8))
 }
@@ -1033,6 +1053,9 @@ func ReadRootEnumerant(msg *capnp.Message) (Enumerant, error) {
 	return Enumerant{root.Struct()}, err
 }
 
+func (Enumerant) DecodeFromPtr(p capnp.Ptr) Enumerant {
+	return Enumerant{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Enumerant) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -1112,6 +1135,9 @@ func ReadRootSuperclass(msg *capnp.Message) (Superclass, error) {
 	return Superclass{root.Struct()}, err
 }
 
+func (Superclass) DecodeFromPtr(p capnp.Ptr) Superclass {
+	return Superclass{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Superclass) Id() uint64 {
 	return s.Struct.Uint64(0)
 }
@@ -1173,6 +1199,9 @@ func ReadRootMethod(msg *capnp.Message) (Method, error) {
 	return Method{root.Struct()}, err
 }
 
+func (Method) DecodeFromPtr(p capnp.Ptr) Method {
+	return Method{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Method) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -1464,6 +1493,10 @@ func ReadRootType(msg *capnp.Message) (Type, error) {
 	return Type{root.Struct()}, err
 }
 
+func (Type) DecodeFromPtr(p capnp.Ptr) Type {
+	return Type{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Type) Which() Type_Which {
 	return Type_Which(s.Struct.Uint16(0))
 }
@@ -1788,6 +1821,9 @@ func ReadRootBrand(msg *capnp.Message) (Brand, error) {
 	return Brand{root.Struct()}, err
 }
 
+func (Brand) DecodeFromPtr(p capnp.Ptr) Brand {
+	return Brand{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Brand) Scopes() (Brand_Scope_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return Brand_Scope_List{List: p.List()}, err
@@ -1859,6 +1895,10 @@ func ReadRootBrand_Scope(msg *capnp.Message) (Brand_Scope, error) {
 	return Brand_Scope{root.Struct()}, err
 }
 
+func (Brand_Scope) DecodeFromPtr(p capnp.Ptr) Brand_Scope {
+	return Brand_Scope{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Brand_Scope) Which() Brand_Scope_Which {
 	return Brand_Scope_Which(s.Struct.Uint16(8))
 }
@@ -1954,6 +1994,10 @@ func ReadRootBrand_Binding(msg *capnp.Message) (Brand_Binding, error) {
 	return Brand_Binding{root.Struct()}, err
 }
 
+func (Brand_Binding) DecodeFromPtr(p capnp.Ptr) Brand_Binding {
+	return Brand_Binding{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Brand_Binding) Which() Brand_Binding_Which {
 	return Brand_Binding_Which(s.Struct.Uint16(0))
 }
@@ -2092,6 +2136,10 @@ func ReadRootValue(msg *capnp.Message) (Value, error) {
 	return Value{root.Struct()}, err
 }
 
+func (Value) DecodeFromPtr(p capnp.Ptr) Value {
+	return Value{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Value) Which() Value_Which {
 	return Value_Which(s.Struct.Uint16(0))
 }
@@ -2380,6 +2428,9 @@ func ReadRootAnnotation(msg *capnp.Message) (Annotation, error) {
 	return Annotation{root.Struct()}, err
 }
 
+func (Annotation) DecodeFromPtr(p capnp.Ptr) Annotation {
+	return Annotation{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Annotation) Id() uint64 {
 	return s.Struct.Uint64(0)
 }
@@ -2539,6 +2590,9 @@ func ReadRootCapnpVersion(msg *capnp.Message) (CapnpVersion, error) {
 	return CapnpVersion{root.Struct()}, err
 }
 
+func (CapnpVersion) DecodeFromPtr(p capnp.Ptr) CapnpVersion {
+	return CapnpVersion{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s CapnpVersion) Major() uint16 {
 	return s.Struct.Uint16(0)
 }
@@ -2592,6 +2646,9 @@ func ReadRootCodeGeneratorRequest(msg *capnp.Message) (CodeGeneratorRequest, err
 	return CodeGeneratorRequest{root.Struct()}, err
 }
 
+func (CodeGeneratorRequest) DecodeFromPtr(p capnp.Ptr) CodeGeneratorRequest {
+	return CodeGeneratorRequest{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s CodeGeneratorRequest) CapnpVersion() (CapnpVersion, error) {
 	p, err := s.Struct.Ptr(2)
 	return CapnpVersion{Struct: p.Struct()}, err
@@ -2717,6 +2774,9 @@ func ReadRootCodeGeneratorRequest_RequestedFile(msg *capnp.Message) (CodeGenerat
 	return CodeGeneratorRequest_RequestedFile{root.Struct()}, err
 }
 
+func (CodeGeneratorRequest_RequestedFile) DecodeFromPtr(p capnp.Ptr) CodeGeneratorRequest_RequestedFile {
+	return CodeGeneratorRequest_RequestedFile{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s CodeGeneratorRequest_RequestedFile) Id() uint64 {
 	return s.Struct.Uint64(0)
 }
@@ -2796,6 +2856,9 @@ func ReadRootCodeGeneratorRequest_RequestedFile_Import(msg *capnp.Message) (Code
 	return CodeGeneratorRequest_RequestedFile_Import{root.Struct()}, err
 }
 
+func (CodeGeneratorRequest_RequestedFile_Import) DecodeFromPtr(p capnp.Ptr) CodeGeneratorRequest_RequestedFile_Import {
+	return CodeGeneratorRequest_RequestedFile_Import{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s CodeGeneratorRequest_RequestedFile_Import) Id() uint64 {
 	return s.Struct.Uint64(0)
 }
diff --git a/list.go b/list.go
index 1a42c841..fd182f25 100644
--- a/list.go
+++ b/list.go
@@ -226,9 +226,20 @@ func (p List) SetStruct(i int, s Struct) error {
 	return nil
 }
 
+// l.EncodeAsPtr is equivalent to l.ToPtr(); for implementing TypeParam.
+// The segment argument is ignored.
+func (l List) EncodeAsPtr(*Segment) Ptr { return l.ToPtr() }
+
+// DecodeFromPtr(p) is equivalent to p.List; for implementing TypeParam.
+func (List) DecodeFromPtr(p Ptr) List { return p.List() }
+
+var _ TypeParam[List] = List{}
+
 // A BitList is a reference to a list of booleans.
 type BitList struct{ List }
 
+var _ TypeParam[BitList] = BitList{}
+
 // NewBitList creates a new bit list, preferring placement in s.
 func NewBitList(s *Segment, n int32) (BitList, error) {
 	if n < 0 || n >= 1<<29 {
@@ -305,9 +316,15 @@ func (p BitList) String() string {
 	return string(buf)
 }
 
+func (BitList) DecodeFromPtr(p Ptr) BitList {
+	return BitList{ List: List{}.DecodeFromPtr(p) }
+}
+
 // A PointerList is a reference to an array of pointers.
 type PointerList struct{ List }
 
+var _ TypeParam[PointerList] = PointerList{}
+
 // NewPointerList allocates a new list of pointers, preferring placement in s.
 func NewPointerList(s *Segment, n int32) (PointerList, error) {
 	total, ok := wordSize.times(n)
@@ -345,9 +362,15 @@ func (p PointerList) Set(i int, v Ptr) error {
 	return p.seg.writePtr(addr, v, false)
 }
 
+func (PointerList) DecodeFromPtr(p Ptr) PointerList {
+	return PointerList{ List: List{}.DecodeFromPtr(p) }
+}
+
 // TextList is an array of pointers to strings.
 type TextList struct{ List }
 
+var _ TypeParam[TextList] = TextList{}
+
 // NewTextList allocates a new list of text pointers, preferring placement in s.
 func NewTextList(s *Segment, n int32) (TextList, error) {
 	pl, err := NewPointerList(s, n)
@@ -419,9 +442,15 @@ func (l TextList) String() string {
 	return string(buf)
 }
 
+func (TextList) DecodeFromPtr(p Ptr) TextList {
+	return TextList{ List: List{}.DecodeFromPtr(p) }
+}
+
 // DataList is an array of pointers to data.
 type DataList struct{ List }
 
+var _ TypeParam[DataList] = DataList{}
+
 // NewDataList allocates a new list of data pointers, preferring placement in s.
 func NewDataList(s *Segment, n int32) (DataList, error) {
 	pl, err := NewPointerList(s, n)
@@ -479,9 +508,15 @@ func (l DataList) String() string {
 	return string(buf)
 }
 
+func (DataList) DecodeFromPtr(p Ptr) DataList {
+	return DataList{ List: List{}.DecodeFromPtr(p) }
+}
+
 // A VoidList is a list of zero-sized elements.
 type VoidList struct{ List }
 
+var _ TypeParam[VoidList] = VoidList{}
+
 // NewVoidList creates a list of voids.  No allocation is performed;
 // s is only used for Segment()'s return value.
 func NewVoidList(s *Segment, n int32) VoidList {
@@ -509,9 +544,15 @@ func (l VoidList) String() string {
 	return string(buf)
 }
 
+func (VoidList) DecodeFromPtr(p Ptr) VoidList {
+	return VoidList{ List: List{}.DecodeFromPtr(p) }
+}
+
 // A UInt8List is an array of UInt8 values.
 type UInt8List struct{ List }
 
+var _ TypeParam[UInt8List] = UInt8List{}
+
 // NewUInt8List creates a new list of UInt8, preferring placement in s.
 func NewUInt8List(s *Segment, n int32) (UInt8List, error) {
 	l, err := newPrimitiveList(s, 1, n)
@@ -590,9 +631,15 @@ func (l UInt8List) String() string {
 	return string(buf)
 }
 
+func (UInt8List) DecodeFromPtr(p Ptr) UInt8List {
+	return UInt8List{ List: List{}.DecodeFromPtr(p) }
+}
+
 // Int8List is an array of Int8 values.
 type Int8List struct{ List }
 
+var _ TypeParam[Int8List] = Int8List{}
+
 // NewInt8List creates a new list of Int8, preferring placement in s.
 func NewInt8List(s *Segment, n int32) (Int8List, error) {
 	l, err := newPrimitiveList(s, 1, n)
@@ -634,9 +681,15 @@ func (l Int8List) String() string {
 	return string(buf)
 }
 
+func (Int8List) DecodeFromPtr(p Ptr) Int8List {
+	return Int8List{ List: List{}.DecodeFromPtr(p) }
+}
+
 // A UInt16List is an array of UInt16 values.
 type UInt16List struct{ List }
 
+var _ TypeParam[UInt16List] = UInt16List{}
+
 // NewUInt16List creates a new list of UInt16, preferring placement in s.
 func NewUInt16List(s *Segment, n int32) (UInt16List, error) {
 	l, err := newPrimitiveList(s, 2, n)
@@ -678,9 +731,15 @@ func (l UInt16List) String() string {
 	return string(buf)
 }
 
+func (UInt16List) DecodeFromPtr(p Ptr) UInt16List {
+	return UInt16List{ List: List{}.DecodeFromPtr(p) }
+}
+
 // Int16List is an array of Int16 values.
 type Int16List struct{ List }
 
+var _ TypeParam[Int16List] = Int16List{}
+
 // NewInt16List creates a new list of Int16, preferring placement in s.
 func NewInt16List(s *Segment, n int32) (Int16List, error) {
 	l, err := newPrimitiveList(s, 2, n)
@@ -722,9 +781,15 @@ func (l Int16List) String() string {
 	return string(buf)
 }
 
+func (Int16List) DecodeFromPtr(p Ptr) Int16List {
+	return Int16List{ List: List{}.DecodeFromPtr(p) }
+}
+
 // UInt32List is an array of UInt32 values.
 type UInt32List struct{ List }
 
+var _ TypeParam[UInt32List] = UInt32List{}
+
 // NewUInt32List creates a new list of UInt32, preferring placement in s.
 func NewUInt32List(s *Segment, n int32) (UInt32List, error) {
 	l, err := newPrimitiveList(s, 4, n)
@@ -766,9 +831,15 @@ func (l UInt32List) String() string {
 	return string(buf)
 }
 
+func (UInt32List) DecodeFromPtr(p Ptr) UInt32List {
+	return UInt32List{ List: List{}.DecodeFromPtr(p) }
+}
+
 // Int32List is an array of Int32 values.
 type Int32List struct{ List }
 
+var _ TypeParam[Int32List] = Int32List{}
+
 // NewInt32List creates a new list of Int32, preferring placement in s.
 func NewInt32List(s *Segment, n int32) (Int32List, error) {
 	l, err := newPrimitiveList(s, 4, n)
@@ -810,9 +881,15 @@ func (l Int32List) String() string {
 	return string(buf)
 }
 
+func (Int32List) DecodeFromPtr(p Ptr) Int32List {
+	return Int32List{ List: List{}.DecodeFromPtr(p) }
+}
+
 // UInt64List is an array of UInt64 values.
 type UInt64List struct{ List }
 
+var _ TypeParam[UInt64List] = UInt64List{}
+
 // NewUInt64List creates a new list of UInt64, preferring placement in s.
 func NewUInt64List(s *Segment, n int32) (UInt64List, error) {
 	l, err := newPrimitiveList(s, 8, n)
@@ -854,9 +931,15 @@ func (l UInt64List) String() string {
 	return string(buf)
 }
 
+func (UInt64List) DecodeFromPtr(p Ptr) UInt64List {
+	return UInt64List{ List: List{}.DecodeFromPtr(p) }
+}
+
 // Int64List is an array of Int64 values.
 type Int64List struct{ List }
 
+var _ TypeParam[Int64List] = Int64List{}
+
 // NewInt64List creates a new list of Int64, preferring placement in s.
 func NewInt64List(s *Segment, n int32) (Int64List, error) {
 	l, err := newPrimitiveList(s, 8, n)
@@ -898,9 +981,15 @@ func (l Int64List) String() string {
 	return string(buf)
 }
 
+func (Int64List) DecodeFromPtr(p Ptr) Int64List {
+	return Int64List{ List: List{}.DecodeFromPtr(p) }
+}
+
 // Float32List is an array of Float32 values.
 type Float32List struct{ List }
 
+var _ TypeParam[Float32List] = Float32List{}
+
 // NewFloat32List creates a new list of Float32, preferring placement in s.
 func NewFloat32List(s *Segment, n int32) (Float32List, error) {
 	l, err := newPrimitiveList(s, 4, n)
@@ -942,9 +1031,15 @@ func (l Float32List) String() string {
 	return string(buf)
 }
 
+func (Float32List) DecodeFromPtr(p Ptr) Float32List {
+	return Float32List{ List: List{}.DecodeFromPtr(p) }
+}
+
 // Float64List is an array of Float64 values.
 type Float64List struct{ List }
 
+var _ TypeParam[Float64List] = Float64List{}
+
 // NewFloat64List creates a new list of Float64, preferring placement in s.
 func NewFloat64List(s *Segment, n int32) (Float64List, error) {
 	l, err := newPrimitiveList(s, 8, n)
@@ -986,9 +1081,15 @@ func (l Float64List) String() string {
 	return string(buf)
 }
 
+func (Float64List) DecodeFromPtr(p Ptr) Float64List {
+	return Float64List{ List: List{}.DecodeFromPtr(p) }
+}
+
 // A list of some Cap'n Proto enum type T.
 type EnumList[T ~uint16] UInt16List
 
+var _ TypeParam[EnumList[uint16]] = EnumList[uint16]{}
+
 // NewEnumList creates a new list of T, preferring placement in s.
 func NewEnumList[T ~uint16](s *Segment, n int32) (EnumList[T], error) {
 	l, err := NewUInt16List(s, n)
@@ -1010,9 +1111,15 @@ func (l EnumList[T]) String() string {
 	return UInt16List(l).String()
 }
 
+func (EnumList[T]) DecodeFromPtr(p Ptr) EnumList[T] {
+	return EnumList[T]{ List: List{}.DecodeFromPtr(p) }
+}
+
 // A list of some Cap'n Proto struct type T.
 type StructList[T ~struct{ Struct }] struct{ List }
 
+var _ TypeParam[StructList[struct{Struct}]] = StructList[struct{Struct}]{}
+
 // At returns the i'th element.
 func (s StructList[T]) At(i int) T {
 	return T{s.List.Struct(i)}
@@ -1037,6 +1144,10 @@ func (s StructList[T]) String() string {
 	return buf.String()
 }
 
+func (StructList[T]) DecodeFromPtr(p Ptr) StructList[T] {
+	return StructList[T]{ List: List{}.DecodeFromPtr(p) }
+}
+
 type CapList[T ~struct{ Client }] PointerList
 
 func (c CapList[T]) At(i int) (T, error) {
@@ -1054,6 +1165,10 @@ func (c CapList[T]) Set(i int, v T) error {
 	return pl.Set(i, NewInterface(seg, capId).ToPtr())
 }
 
+func (CapList[T]) DecodeFromPtr(p Ptr) CapList[T] {
+	return CapList[T](PointerList{}.DecodeFromPtr(p))
+}
+
 type listFlags uint8
 
 const (
diff --git a/pointer.go b/pointer.go
index e5c5d711..b0ee3735 100644
--- a/pointer.go
+++ b/pointer.go
@@ -200,6 +200,15 @@ func SamePtr(p, q Ptr) bool {
 	return p.seg == q.seg && p.off == q.off
 }
 
+// EncodeAsPtr returns the receiver; for implementing TypeParam.
+// The segment argument is ignored.
+func (p Ptr) EncodeAsPtr(*Segment) Ptr { return p }
+
+// DecodeFromPtr returns its argument; for implementing TypeParam.
+func (Ptr) DecodeFromPtr(p Ptr) Ptr { return p }
+
+var _ TypeParam[Ptr] = Ptr{}
+
 func unmarshalDefault(def []byte) (Ptr, error) {
 	msg, err := Unmarshal(def)
 	if err != nil {
diff --git a/rpc/internal/testcapnp/test.capnp.go b/rpc/internal/testcapnp/test.capnp.go
index cb1c53e1..1dca94db 100644
--- a/rpc/internal/testcapnp/test.capnp.go
+++ b/rpc/internal/testcapnp/test.capnp.go
@@ -39,6 +39,10 @@ func (c PingPong) AddRef() PingPong {
 	}
 }
 
+func (PingPong) DecodeFromPtr(p capnp.Ptr) PingPong {
+	return PingPong{Client: capnp.Client{}.DecodeFromPtr(p)}
+}
+
 // A PingPong_Server is a PingPong with a local implementation.
 type PingPong_Server interface {
 	EchoNum(context.Context, PingPong_echoNum) error
@@ -129,6 +133,9 @@ func (s PingPong_echoNum_Params) String() string {
 	return str
 }
 
+func (PingPong_echoNum_Params) DecodeFromPtr(p capnp.Ptr) PingPong_echoNum_Params {
+	return PingPong_echoNum_Params{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s PingPong_echoNum_Params) N() int64 {
 	return int64(s.Struct.Uint64(0))
 }
@@ -179,6 +186,9 @@ func (s PingPong_echoNum_Results) String() string {
 	return str
 }
 
+func (PingPong_echoNum_Results) DecodeFromPtr(p capnp.Ptr) PingPong_echoNum_Results {
+	return PingPong_echoNum_Results{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s PingPong_echoNum_Results) N() int64 {
 	return int64(s.Struct.Uint64(0))
 }
@@ -232,6 +242,10 @@ func (c StreamTest) AddRef() StreamTest {
 	}
 }
 
+func (StreamTest) DecodeFromPtr(p capnp.Ptr) StreamTest {
+	return StreamTest{Client: capnp.Client{}.DecodeFromPtr(p)}
+}
+
 // A StreamTest_Server is a StreamTest with a local implementation.
 type StreamTest_Server interface {
 	Push(context.Context, StreamTest_push) error
@@ -322,6 +336,9 @@ func (s StreamTest_push_Params) String() string {
 	return str
 }
 
+func (StreamTest_push_Params) DecodeFromPtr(p capnp.Ptr) StreamTest_push_Params {
+	return StreamTest_push_Params{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s StreamTest_push_Params) Data() ([]byte, error) {
 	p, err := s.Struct.Ptr(0)
 	return []byte(p.Data()), err
@@ -396,6 +413,10 @@ func (c CapArgsTest) AddRef() CapArgsTest {
 	}
 }
 
+func (CapArgsTest) DecodeFromPtr(p capnp.Ptr) CapArgsTest {
+	return CapArgsTest{Client: capnp.Client{}.DecodeFromPtr(p)}
+}
+
 // A CapArgsTest_Server is a CapArgsTest with a local implementation.
 type CapArgsTest_Server interface {
 	Call(context.Context, CapArgsTest_call) error
@@ -517,6 +538,9 @@ func (s CapArgsTest_call_Params) String() string {
 	return str
 }
 
+func (CapArgsTest_call_Params) DecodeFromPtr(p capnp.Ptr) CapArgsTest_call_Params {
+	return CapArgsTest_call_Params{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s CapArgsTest_call_Params) Cap() capnp.Client {
 	p, _ := s.Struct.Ptr(0)
 	return p.Interface().Client()
@@ -581,6 +605,10 @@ func (s CapArgsTest_call_Results) String() string {
 	return str
 }
 
+func (CapArgsTest_call_Results) DecodeFromPtr(p capnp.Ptr) CapArgsTest_call_Results {
+	return CapArgsTest_call_Results{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 // CapArgsTest_call_Results_List is a list of CapArgsTest_call_Results.
 type CapArgsTest_call_Results_List = capnp.StructList[CapArgsTest_call_Results]
 
@@ -623,6 +651,10 @@ func (s CapArgsTest_self_Params) String() string {
 	return str
 }
 
+func (CapArgsTest_self_Params) DecodeFromPtr(p capnp.Ptr) CapArgsTest_self_Params {
+	return CapArgsTest_self_Params{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 // CapArgsTest_self_Params_List is a list of CapArgsTest_self_Params.
 type CapArgsTest_self_Params_List = capnp.StructList[CapArgsTest_self_Params]
 
@@ -665,6 +697,9 @@ func (s CapArgsTest_self_Results) String() string {
 	return str
 }
 
+func (CapArgsTest_self_Results) DecodeFromPtr(p capnp.Ptr) CapArgsTest_self_Results {
+	return CapArgsTest_self_Results{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s CapArgsTest_self_Results) Self() CapArgsTest {
 	p, _ := s.Struct.Ptr(0)
 	return CapArgsTest{Client: p.Interface().Client()}
diff --git a/std/capnp/compat/json/json.capnp.go b/std/capnp/compat/json/json.capnp.go
index 7a097bce..7626798f 100644
--- a/std/capnp/compat/json/json.capnp.go
+++ b/std/capnp/compat/json/json.capnp.go
@@ -75,6 +75,10 @@ func (s Value) String() string {
 	return str
 }
 
+func (Value) DecodeFromPtr(p capnp.Ptr) Value {
+	return Value{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Value) Which() Value_Which {
 	return Value_Which(s.Struct.Uint16(0))
 }
@@ -274,6 +278,9 @@ func (s Value_Field) String() string {
 	return str
 }
 
+func (Value_Field) DecodeFromPtr(p capnp.Ptr) Value_Field {
+	return Value_Field{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Value_Field) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -362,6 +369,9 @@ func (s Value_Call) String() string {
 	return str
 }
 
+func (Value_Call) DecodeFromPtr(p capnp.Ptr) Value_Call {
+	return Value_Call{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Value_Call) Function() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -446,6 +456,9 @@ func (s FlattenOptions) String() string {
 	return str
 }
 
+func (FlattenOptions) DecodeFromPtr(p capnp.Ptr) FlattenOptions {
+	return FlattenOptions{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s FlattenOptions) Prefix() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -506,6 +519,9 @@ func (s DiscriminatorOptions) String() string {
 	return str
 }
 
+func (DiscriminatorOptions) DecodeFromPtr(p capnp.Ptr) DiscriminatorOptions {
+	return DiscriminatorOptions{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s DiscriminatorOptions) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
diff --git a/std/capnp/persistent/persistent.capnp.go b/std/capnp/persistent/persistent.capnp.go
index 200336e0..c8ea8821 100644
--- a/std/capnp/persistent/persistent.capnp.go
+++ b/std/capnp/persistent/persistent.capnp.go
@@ -40,6 +40,10 @@ func (c Persistent) AddRef() Persistent {
 	}
 }
 
+func (Persistent) DecodeFromPtr(p capnp.Ptr) Persistent {
+	return Persistent{Client: capnp.Client{}.DecodeFromPtr(p)}
+}
+
 // A Persistent_Server is a Persistent with a local implementation.
 type Persistent_Server interface {
 	Save(context.Context, Persistent_save) error
@@ -130,6 +134,9 @@ func (s Persistent_SaveParams) String() string {
 	return str
 }
 
+func (Persistent_SaveParams) DecodeFromPtr(p capnp.Ptr) Persistent_SaveParams {
+	return Persistent_SaveParams{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Persistent_SaveParams) SealFor() (capnp.Ptr, error) {
 	return s.Struct.Ptr(0)
 }
@@ -188,6 +195,9 @@ func (s Persistent_SaveResults) String() string {
 	return str
 }
 
+func (Persistent_SaveResults) DecodeFromPtr(p capnp.Ptr) Persistent_SaveResults {
+	return Persistent_SaveResults{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Persistent_SaveResults) SturdyRef() (capnp.Ptr, error) {
 	return s.Struct.Ptr(0)
 }
diff --git a/std/capnp/rpc/rpc.capnp.go b/std/capnp/rpc/rpc.capnp.go
index 284b4eca..de40f836 100644
--- a/std/capnp/rpc/rpc.capnp.go
+++ b/std/capnp/rpc/rpc.capnp.go
@@ -88,6 +88,10 @@ func (s Message) String() string {
 	return str
 }
 
+func (Message) DecodeFromPtr(p capnp.Ptr) Message {
+	return Message{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Message) Which() Message_Which {
 	return Message_Which(s.Struct.Uint16(0))
 }
@@ -611,6 +615,9 @@ func (s Bootstrap) String() string {
 	return str
 }
 
+func (Bootstrap) DecodeFromPtr(p capnp.Ptr) Bootstrap {
+	return Bootstrap{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Bootstrap) QuestionId() uint32 {
 	return s.Struct.Uint32(0)
 }
@@ -699,6 +706,9 @@ func (s Call) String() string {
 	return str
 }
 
+func (Call) DecodeFromPtr(p capnp.Ptr) Call {
+	return Call{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Call) QuestionId() uint32 {
 	return s.Struct.Uint32(0)
 }
@@ -909,6 +919,10 @@ func (s Return) String() string {
 	return str
 }
 
+func (Return) DecodeFromPtr(p capnp.Ptr) Return {
+	return Return{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Return) Which() Return_Which {
 	return Return_Which(s.Struct.Uint16(6))
 }
@@ -1087,6 +1101,9 @@ func (s Finish) String() string {
 	return str
 }
 
+func (Finish) DecodeFromPtr(p capnp.Ptr) Finish {
+	return Finish{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Finish) QuestionId() uint32 {
 	return s.Struct.Uint32(0)
 }
@@ -1163,6 +1180,10 @@ func (s Resolve) String() string {
 	return str
 }
 
+func (Resolve) DecodeFromPtr(p capnp.Ptr) Resolve {
+	return Resolve{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Resolve) Which() Resolve_Which {
 	return Resolve_Which(s.Struct.Uint16(4))
 }
@@ -1288,6 +1309,9 @@ func (s Release) String() string {
 	return str
 }
 
+func (Release) DecodeFromPtr(p capnp.Ptr) Release {
+	return Release{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Release) Id() uint32 {
 	return s.Struct.Uint32(0)
 }
@@ -1371,6 +1395,9 @@ func (s Disembargo) String() string {
 	return str
 }
 
+func (Disembargo) DecodeFromPtr(p capnp.Ptr) Disembargo {
+	return Disembargo{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Disembargo) Target() (MessageTarget, error) {
 	p, err := s.Struct.Ptr(0)
 	return MessageTarget{Struct: p.Struct()}, err
@@ -1499,6 +1526,9 @@ func (s Provide) String() string {
 	return str
 }
 
+func (Provide) DecodeFromPtr(p capnp.Ptr) Provide {
+	return Provide{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Provide) QuestionId() uint32 {
 	return s.Struct.Uint32(0)
 }
@@ -1593,6 +1623,9 @@ func (s Accept) String() string {
 	return str
 }
 
+func (Accept) DecodeFromPtr(p capnp.Ptr) Accept {
+	return Accept{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Accept) QuestionId() uint32 {
 	return s.Struct.Uint32(0)
 }
@@ -1667,6 +1700,9 @@ func (s Join) String() string {
 	return str
 }
 
+func (Join) DecodeFromPtr(p capnp.Ptr) Join {
+	return Join{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Join) QuestionId() uint32 {
 	return s.Struct.Uint32(0)
 }
@@ -1779,6 +1815,10 @@ func (s MessageTarget) String() string {
 	return str
 }
 
+func (MessageTarget) DecodeFromPtr(p capnp.Ptr) MessageTarget {
+	return MessageTarget{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s MessageTarget) Which() MessageTarget_Which {
 	return MessageTarget_Which(s.Struct.Uint16(4))
 }
@@ -1872,6 +1912,9 @@ func (s Payload) String() string {
 	return str
 }
 
+func (Payload) DecodeFromPtr(p capnp.Ptr) Payload {
+	return Payload{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Payload) Content() (capnp.Ptr, error) {
 	return s.Struct.Ptr(0)
 }
@@ -1984,6 +2027,10 @@ func (s CapDescriptor) String() string {
 	return str
 }
 
+func (CapDescriptor) DecodeFromPtr(p capnp.Ptr) CapDescriptor {
+	return CapDescriptor{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s CapDescriptor) Which() CapDescriptor_Which {
 	return CapDescriptor_Which(s.Struct.Uint16(0))
 }
@@ -2150,6 +2197,9 @@ func (s PromisedAnswer) String() string {
 	return str
 }
 
+func (PromisedAnswer) DecodeFromPtr(p capnp.Ptr) PromisedAnswer {
+	return PromisedAnswer{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s PromisedAnswer) QuestionId() uint32 {
 	return s.Struct.Uint32(0)
 }
@@ -2242,6 +2292,10 @@ func (s PromisedAnswer_Op) String() string {
 	return str
 }
 
+func (PromisedAnswer_Op) DecodeFromPtr(p capnp.Ptr) PromisedAnswer_Op {
+	return PromisedAnswer_Op{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s PromisedAnswer_Op) Which() PromisedAnswer_Op_Which {
 	return PromisedAnswer_Op_Which(s.Struct.Uint16(0))
 }
@@ -2304,6 +2358,9 @@ func (s ThirdPartyCapDescriptor) String() string {
 	return str
 }
 
+func (ThirdPartyCapDescriptor) DecodeFromPtr(p capnp.Ptr) ThirdPartyCapDescriptor {
+	return ThirdPartyCapDescriptor{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s ThirdPartyCapDescriptor) Id() (capnp.Ptr, error) {
 	return s.Struct.Ptr(0)
 }
@@ -2370,6 +2427,9 @@ func (s Exception) String() string {
 	return str
 }
 
+func (Exception) DecodeFromPtr(p capnp.Ptr) Exception {
+	return Exception{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Exception) Reason() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
diff --git a/std/capnp/rpctwoparty/rpc-twoparty.capnp.go b/std/capnp/rpctwoparty/rpc-twoparty.capnp.go
index 8b3bc6ee..73def667 100644
--- a/std/capnp/rpctwoparty/rpc-twoparty.capnp.go
+++ b/std/capnp/rpctwoparty/rpc-twoparty.capnp.go
@@ -77,6 +77,9 @@ func (s VatId) String() string {
 	return str
 }
 
+func (VatId) DecodeFromPtr(p capnp.Ptr) VatId {
+	return VatId{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s VatId) Side() Side {
 	return Side(s.Struct.Uint16(0))
 }
@@ -127,6 +130,9 @@ func (s ProvisionId) String() string {
 	return str
 }
 
+func (ProvisionId) DecodeFromPtr(p capnp.Ptr) ProvisionId {
+	return ProvisionId{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s ProvisionId) JoinId() uint32 {
 	return s.Struct.Uint32(0)
 }
@@ -177,6 +183,10 @@ func (s RecipientId) String() string {
 	return str
 }
 
+func (RecipientId) DecodeFromPtr(p capnp.Ptr) RecipientId {
+	return RecipientId{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 // RecipientId_List is a list of RecipientId.
 type RecipientId_List = capnp.StructList[RecipientId]
 
@@ -219,6 +229,10 @@ func (s ThirdPartyCapId) String() string {
 	return str
 }
 
+func (ThirdPartyCapId) DecodeFromPtr(p capnp.Ptr) ThirdPartyCapId {
+	return ThirdPartyCapId{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 // ThirdPartyCapId_List is a list of ThirdPartyCapId.
 type ThirdPartyCapId_List = capnp.StructList[ThirdPartyCapId]
 
@@ -261,6 +275,9 @@ func (s JoinKeyPart) String() string {
 	return str
 }
 
+func (JoinKeyPart) DecodeFromPtr(p capnp.Ptr) JoinKeyPart {
+	return JoinKeyPart{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s JoinKeyPart) JoinId() uint32 {
 	return s.Struct.Uint32(0)
 }
@@ -327,6 +344,9 @@ func (s JoinResult) String() string {
 	return str
 }
 
+func (JoinResult) DecodeFromPtr(p capnp.Ptr) JoinResult {
+	return JoinResult{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s JoinResult) JoinId() uint32 {
 	return s.Struct.Uint32(0)
 }
diff --git a/std/capnp/schema/schema.capnp.go b/std/capnp/schema/schema.capnp.go
index c19b1180..f64d3eaa 100644
--- a/std/capnp/schema/schema.capnp.go
+++ b/std/capnp/schema/schema.capnp.go
@@ -75,6 +75,10 @@ func (s Node) String() string {
 	return str
 }
 
+func (Node) DecodeFromPtr(p capnp.Ptr) Node {
+	return Node{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Node) Which() Node_Which {
 	return Node_Which(s.Struct.Uint16(12))
 }
@@ -651,6 +655,9 @@ func (s Node_Parameter) String() string {
 	return str
 }
 
+func (Node_Parameter) DecodeFromPtr(p capnp.Ptr) Node_Parameter {
+	return Node_Parameter{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Node_Parameter) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -711,6 +718,9 @@ func (s Node_NestedNode) String() string {
 	return str
 }
 
+func (Node_NestedNode) DecodeFromPtr(p capnp.Ptr) Node_NestedNode {
+	return Node_NestedNode{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Node_NestedNode) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -779,6 +789,9 @@ func (s Node_SourceInfo) String() string {
 	return str
 }
 
+func (Node_SourceInfo) DecodeFromPtr(p capnp.Ptr) Node_SourceInfo {
+	return Node_SourceInfo{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Node_SourceInfo) Id() uint64 {
 	return s.Struct.Uint64(0)
 }
@@ -871,6 +884,9 @@ func (s Node_SourceInfo_Member) String() string {
 	return str
 }
 
+func (Node_SourceInfo_Member) DecodeFromPtr(p capnp.Ptr) Node_SourceInfo_Member {
+	return Node_SourceInfo_Member{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Node_SourceInfo_Member) DocComment() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -971,6 +987,10 @@ func (s Field) String() string {
 	return str
 }
 
+func (Field) DecodeFromPtr(p capnp.Ptr) Field {
+	return Field{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Field) Which() Field_Which {
 	return Field_Which(s.Struct.Uint16(8))
 }
@@ -1218,6 +1238,9 @@ func (s Enumerant) String() string {
 	return str
 }
 
+func (Enumerant) DecodeFromPtr(p capnp.Ptr) Enumerant {
+	return Enumerant{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Enumerant) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -1310,6 +1333,9 @@ func (s Superclass) String() string {
 	return str
 }
 
+func (Superclass) DecodeFromPtr(p capnp.Ptr) Superclass {
+	return Superclass{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Superclass) Id() uint64 {
 	return s.Struct.Uint64(0)
 }
@@ -1388,6 +1414,9 @@ func (s Method) String() string {
 	return str
 }
 
+func (Method) DecodeFromPtr(p capnp.Ptr) Method {
+	return Method{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Method) Name() (string, error) {
 	p, err := s.Struct.Ptr(0)
 	return p.Text(), err
@@ -1700,6 +1729,10 @@ func (s Type) String() string {
 	return str
 }
 
+func (Type) DecodeFromPtr(p capnp.Ptr) Type {
+	return Type{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Type) Which() Type_Which {
 	return Type_Which(s.Struct.Uint16(0))
 }
@@ -2139,6 +2172,9 @@ func (s Brand) String() string {
 	return str
 }
 
+func (Brand) DecodeFromPtr(p capnp.Ptr) Brand {
+	return Brand{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Brand) Scopes() (Brand_Scope_List, error) {
 	p, err := s.Struct.Ptr(0)
 	return Brand_Scope_List{List: p.List()}, err
@@ -2223,6 +2259,10 @@ func (s Brand_Scope) String() string {
 	return str
 }
 
+func (Brand_Scope) DecodeFromPtr(p capnp.Ptr) Brand_Scope {
+	return Brand_Scope{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Brand_Scope) Which() Brand_Scope_Which {
 	return Brand_Scope_Which(s.Struct.Uint16(8))
 }
@@ -2331,6 +2371,10 @@ func (s Brand_Binding) String() string {
 	return str
 }
 
+func (Brand_Binding) DecodeFromPtr(p capnp.Ptr) Brand_Binding {
+	return Brand_Binding{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Brand_Binding) Which() Brand_Binding_Which {
 	return Brand_Binding_Which(s.Struct.Uint16(0))
 }
@@ -2486,6 +2530,10 @@ func (s Value) String() string {
 	return str
 }
 
+func (Value) DecodeFromPtr(p capnp.Ptr) Value {
+	return Value{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 func (s Value) Which() Value_Which {
 	return Value_Which(s.Struct.Uint16(0))
 }
@@ -2799,6 +2847,9 @@ func (s Annotation) String() string {
 	return str
 }
 
+func (Annotation) DecodeFromPtr(p capnp.Ptr) Annotation {
+	return Annotation{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s Annotation) Id() uint64 {
 	return s.Struct.Uint64(0)
 }
@@ -2979,6 +3030,9 @@ func (s CapnpVersion) String() string {
 	return str
 }
 
+func (CapnpVersion) DecodeFromPtr(p capnp.Ptr) CapnpVersion {
+	return CapnpVersion{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s CapnpVersion) Major() uint16 {
 	return s.Struct.Uint16(0)
 }
@@ -3045,6 +3099,9 @@ func (s CodeGeneratorRequest) String() string {
 	return str
 }
 
+func (CodeGeneratorRequest) DecodeFromPtr(p capnp.Ptr) CodeGeneratorRequest {
+	return CodeGeneratorRequest{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s CodeGeneratorRequest) CapnpVersion() (CapnpVersion, error) {
 	p, err := s.Struct.Ptr(2)
 	return CapnpVersion{Struct: p.Struct()}, err
@@ -3187,6 +3244,9 @@ func (s CodeGeneratorRequest_RequestedFile) String() string {
 	return str
 }
 
+func (CodeGeneratorRequest_RequestedFile) DecodeFromPtr(p capnp.Ptr) CodeGeneratorRequest_RequestedFile {
+	return CodeGeneratorRequest_RequestedFile{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s CodeGeneratorRequest_RequestedFile) Id() uint64 {
 	return s.Struct.Uint64(0)
 }
@@ -3279,6 +3339,9 @@ func (s CodeGeneratorRequest_RequestedFile_Import) String() string {
 	return str
 }
 
+func (CodeGeneratorRequest_RequestedFile_Import) DecodeFromPtr(p capnp.Ptr) CodeGeneratorRequest_RequestedFile_Import {
+	return CodeGeneratorRequest_RequestedFile_Import{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
 func (s CodeGeneratorRequest_RequestedFile_Import) Id() uint64 {
 	return s.Struct.Uint64(0)
 }
diff --git a/std/capnp/stream/stream.capnp.go b/std/capnp/stream/stream.capnp.go
index 93020e96..edee2a3f 100644
--- a/std/capnp/stream/stream.capnp.go
+++ b/std/capnp/stream/stream.capnp.go
@@ -33,6 +33,10 @@ func (s StreamResult) String() string {
 	return str
 }
 
+func (StreamResult) DecodeFromPtr(p capnp.Ptr) StreamResult {
+	return StreamResult{Struct: capnp.Struct{}.DecodeFromPtr(p)}
+}
+
 // StreamResult_List is a list of StreamResult.
 type StreamResult_List = capnp.StructList[StreamResult]
 
diff --git a/struct.go b/struct.go
index bdde010c..bf8d0709 100644
--- a/struct.go
+++ b/struct.go
@@ -345,3 +345,13 @@ func copyStruct(dst, src Struct) error {
 
 	return nil
 }
+
+// s.EncodeAsPtr is equivalent to s.ToPtr(); for implementing TypeParam.
+// The segment argument is ignored.
+func (s Struct) EncodeAsPtr(*Segment) Ptr { return s.ToPtr() }
+
+// DecodeFromPtr(p) is equivalent to p.Struct() (the receiver is ignored).
+// for implementing TypeParam.
+func (Struct) DecodeFromPtr(p Ptr) Struct { return p.Struct() }
+
+var _ TypeParam[Struct] = Struct{}
diff --git a/typeparam.go b/typeparam.go
new file mode 100644
index 00000000..fa58f81c
--- /dev/null
+++ b/typeparam.go
@@ -0,0 +1,16 @@
+package capnp
+
+// The TypeParam interface must be satisified by a type to be used as a capnproto
+// type parameter. This is satisified by all capnproto pointer types. T should
+// be instantiated by the type itself; in type parameter lists you will typically
+// see parameter/constraints like T TypeParam[T].
+type TypeParam[T any] interface {
+	// Convert the receiver to a Ptr, storing it in seg if it is not
+	// already associated with some message (only true for Clients and
+	// wrappers around them.
+	EncodeAsPtr(seg *Segment) Ptr
+
+	// Decode the pointer as the type of the receiver. Generally,
+	// the reciever will be the zero value for the type.
+	DecodeFromPtr(p Ptr) T
+}