diff --git a/cmd/sbox/sbox_proto/sbox.pb.go b/cmd/sbox/sbox_proto/sbox.pb.go
new file mode 100644
index 0000000..6584bdf
--- /dev/null
+++ b/cmd/sbox/sbox_proto/sbox.pb.go
@@ -0,0 +1,233 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// source: sbox.proto
+
+package sbox_proto
+
+import (
+	fmt "fmt"
+	proto "github.com/golang/protobuf/proto"
+	math "math"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion3 // please upgrade the proto package
+
+// A set of commands to run in a sandbox.
+type Manifest struct {
+	// A list of commands to run in the sandbox.
+	Commands []*Command `protobuf:"bytes,1,rep,name=commands" json:"commands,omitempty"`
+	// If set, GCC-style dependency files from any command that references __SBOX_DEPFILE__ will be
+	// merged into the given output file relative to the $PWD when sbox was started.
+	OutputDepfile        *string  `protobuf:"bytes,2,opt,name=output_depfile,json=outputDepfile" json:"output_depfile,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *Manifest) Reset()         { *m = Manifest{} }
+func (m *Manifest) String() string { return proto.CompactTextString(m) }
+func (*Manifest) ProtoMessage()    {}
+func (*Manifest) Descriptor() ([]byte, []int) {
+	return fileDescriptor_9d0425bf0de86ed1, []int{0}
+}
+
+func (m *Manifest) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Manifest.Unmarshal(m, b)
+}
+func (m *Manifest) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Manifest.Marshal(b, m, deterministic)
+}
+func (m *Manifest) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Manifest.Merge(m, src)
+}
+func (m *Manifest) XXX_Size() int {
+	return xxx_messageInfo_Manifest.Size(m)
+}
+func (m *Manifest) XXX_DiscardUnknown() {
+	xxx_messageInfo_Manifest.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Manifest proto.InternalMessageInfo
+
+func (m *Manifest) GetCommands() []*Command {
+	if m != nil {
+		return m.Commands
+	}
+	return nil
+}
+
+func (m *Manifest) GetOutputDepfile() string {
+	if m != nil && m.OutputDepfile != nil {
+		return *m.OutputDepfile
+	}
+	return ""
+}
+
+// SandboxManifest describes a command to run in the sandbox.
+type Command struct {
+	// A list of copy rules to run before the sandboxed command.  The from field is relative to the
+	// $PWD when sbox was run, the to field is relative to the top of the temporary sandbox directory.
+	CopyBefore []*Copy `protobuf:"bytes,1,rep,name=copy_before,json=copyBefore" json:"copy_before,omitempty"`
+	// If true, change the working directory to the top of the temporary sandbox directory before
+	// running the command.  If false, leave the working directory where it was when sbox was started.
+	Chdir *bool `protobuf:"varint,2,opt,name=chdir" json:"chdir,omitempty"`
+	// The command to run.
+	Command *string `protobuf:"bytes,3,req,name=command" json:"command,omitempty"`
+	// A list of copy rules to run after the sandboxed command.  The from field is relative to the
+	// top of the temporary sandbox directory, the to field is relative to the $PWD when sbox was run.
+	CopyAfter []*Copy `protobuf:"bytes,4,rep,name=copy_after,json=copyAfter" json:"copy_after,omitempty"`
+	// An optional hash of the input files to ensure the textproto files and the sbox rule reruns
+	// when the lists of inputs changes, even if the inputs are not on the command line.
+	InputHash            *string  `protobuf:"bytes,5,opt,name=input_hash,json=inputHash" json:"input_hash,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *Command) Reset()         { *m = Command{} }
+func (m *Command) String() string { return proto.CompactTextString(m) }
+func (*Command) ProtoMessage()    {}
+func (*Command) Descriptor() ([]byte, []int) {
+	return fileDescriptor_9d0425bf0de86ed1, []int{1}
+}
+
+func (m *Command) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Command.Unmarshal(m, b)
+}
+func (m *Command) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Command.Marshal(b, m, deterministic)
+}
+func (m *Command) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Command.Merge(m, src)
+}
+func (m *Command) XXX_Size() int {
+	return xxx_messageInfo_Command.Size(m)
+}
+func (m *Command) XXX_DiscardUnknown() {
+	xxx_messageInfo_Command.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Command proto.InternalMessageInfo
+
+func (m *Command) GetCopyBefore() []*Copy {
+	if m != nil {
+		return m.CopyBefore
+	}
+	return nil
+}
+
+func (m *Command) GetChdir() bool {
+	if m != nil && m.Chdir != nil {
+		return *m.Chdir
+	}
+	return false
+}
+
+func (m *Command) GetCommand() string {
+	if m != nil && m.Command != nil {
+		return *m.Command
+	}
+	return ""
+}
+
+func (m *Command) GetCopyAfter() []*Copy {
+	if m != nil {
+		return m.CopyAfter
+	}
+	return nil
+}
+
+func (m *Command) GetInputHash() string {
+	if m != nil && m.InputHash != nil {
+		return *m.InputHash
+	}
+	return ""
+}
+
+// Copy describes a from-to pair of files to copy.  The paths may be relative, the root that they
+// are relative to is specific to the context the Copy is used in and will be different for
+// from and to.
+type Copy struct {
+	From                 *string  `protobuf:"bytes,1,req,name=from" json:"from,omitempty"`
+	To                   *string  `protobuf:"bytes,2,req,name=to" json:"to,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *Copy) Reset()         { *m = Copy{} }
+func (m *Copy) String() string { return proto.CompactTextString(m) }
+func (*Copy) ProtoMessage()    {}
+func (*Copy) Descriptor() ([]byte, []int) {
+	return fileDescriptor_9d0425bf0de86ed1, []int{2}
+}
+
+func (m *Copy) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Copy.Unmarshal(m, b)
+}
+func (m *Copy) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Copy.Marshal(b, m, deterministic)
+}
+func (m *Copy) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Copy.Merge(m, src)
+}
+func (m *Copy) XXX_Size() int {
+	return xxx_messageInfo_Copy.Size(m)
+}
+func (m *Copy) XXX_DiscardUnknown() {
+	xxx_messageInfo_Copy.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Copy proto.InternalMessageInfo
+
+func (m *Copy) GetFrom() string {
+	if m != nil && m.From != nil {
+		return *m.From
+	}
+	return ""
+}
+
+func (m *Copy) GetTo() string {
+	if m != nil && m.To != nil {
+		return *m.To
+	}
+	return ""
+}
+
+func init() {
+	proto.RegisterType((*Manifest)(nil), "sbox.Manifest")
+	proto.RegisterType((*Command)(nil), "sbox.Command")
+	proto.RegisterType((*Copy)(nil), "sbox.Copy")
+}
+
+func init() {
+	proto.RegisterFile("sbox.proto", fileDescriptor_9d0425bf0de86ed1)
+}
+
+var fileDescriptor_9d0425bf0de86ed1 = []byte{
+	// 252 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x64, 0x90, 0x41, 0x4b, 0xc3, 0x40,
+	0x10, 0x85, 0x49, 0x9a, 0xd2, 0x66, 0x6a, 0x7b, 0x18, 0x3c, 0xec, 0x45, 0x08, 0x01, 0x21, 0x55,
+	0xe8, 0xc1, 0x7f, 0x60, 0xf5, 0xe0, 0xc5, 0xcb, 0x1e, 0x45, 0x08, 0xdb, 0x64, 0x97, 0x04, 0x4c,
+	0x66, 0xd9, 0xdd, 0x82, 0xfd, 0x57, 0xfe, 0x44, 0xd9, 0x49, 0xea, 0xc5, 0xdb, 0xcc, 0xfb, 0x78,
+	0xf3, 0x1e, 0x03, 0xe0, 0x4f, 0xf4, 0x7d, 0xb0, 0x8e, 0x02, 0x61, 0x16, 0xe7, 0xf2, 0x13, 0xd6,
+	0xef, 0x6a, 0xec, 0x8d, 0xf6, 0x01, 0xf7, 0xb0, 0x6e, 0x68, 0x18, 0xd4, 0xd8, 0x7a, 0x91, 0x14,
+	0x8b, 0x6a, 0xf3, 0xb4, 0x3d, 0xb0, 0xe1, 0x65, 0x52, 0xe5, 0x1f, 0xc6, 0x7b, 0xd8, 0xd1, 0x39,
+	0xd8, 0x73, 0xa8, 0x5b, 0x6d, 0x4d, 0xff, 0xa5, 0x45, 0x5a, 0x24, 0x55, 0x2e, 0xb7, 0x93, 0xfa,
+	0x3a, 0x89, 0xe5, 0x4f, 0x02, 0xab, 0xd9, 0x8c, 0x8f, 0xb0, 0x69, 0xc8, 0x5e, 0xea, 0x93, 0x36,
+	0xe4, 0xf4, 0x1c, 0x00, 0xd7, 0x00, 0x7b, 0x91, 0x10, 0xf1, 0x91, 0x29, 0xde, 0xc2, 0xb2, 0xe9,
+	0xda, 0xde, 0xf1, 0xd9, 0xb5, 0x9c, 0x16, 0x14, 0xb0, 0x9a, 0x1b, 0x88, 0x45, 0x91, 0x56, 0xb9,
+	0xbc, 0xae, 0xb8, 0x07, 0x76, 0xd7, 0xca, 0x04, 0xed, 0x44, 0xf6, 0xef, 0x76, 0x1e, 0xe9, 0x73,
+	0x84, 0x78, 0x07, 0xd0, 0x8f, 0xb1, 0x79, 0xa7, 0x7c, 0x27, 0x96, 0x5c, 0x3b, 0x67, 0xe5, 0x4d,
+	0xf9, 0xae, 0x7c, 0x80, 0x2c, 0x3a, 0x10, 0x21, 0x33, 0x8e, 0x06, 0x91, 0x70, 0x10, 0xcf, 0xb8,
+	0x83, 0x34, 0x90, 0x48, 0x59, 0x49, 0x03, 0x1d, 0x6f, 0x3e, 0xf8, 0xa1, 0x35, 0x3f, 0xf4, 0x37,
+	0x00, 0x00, 0xff, 0xff, 0x95, 0x4d, 0xee, 0x7d, 0x5d, 0x01, 0x00, 0x00,
+}
diff --git a/cmd/sbox/sbox_proto/sbox.proto b/cmd/sbox/sbox_proto/sbox.proto
new file mode 100644
index 0000000..ab95545
--- /dev/null
+++ b/cmd/sbox/sbox_proto/sbox.proto
@@ -0,0 +1,58 @@
+// Copyright 2020 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto2";
+
+package sbox;
+option go_package = "sbox_proto";
+
+// A set of commands to run in a sandbox.
+message Manifest {
+  // A list of commands to run in the sandbox.
+  repeated Command commands = 1;
+
+  // If set, GCC-style dependency files from any command that references __SBOX_DEPFILE__ will be
+  // merged into the given output file relative to the $PWD when sbox was started.
+  optional string output_depfile = 2;
+}
+
+// SandboxManifest describes a command to run in the sandbox.
+message Command {
+  // A list of copy rules to run before the sandboxed command.  The from field is relative to the
+  // $PWD when sbox was run, the to field is relative to the top of the temporary sandbox directory.
+  repeated Copy copy_before = 1;
+
+  // If true, change the working directory to the top of the temporary sandbox directory before
+  // running the command.  If false, leave the working directory where it was when sbox was started.
+  optional bool chdir = 2;
+
+  // The command to run.
+  required string command = 3;
+
+  // A list of copy rules to run after the sandboxed command.  The from field is relative to the
+  // top of the temporary sandbox directory, the to field is relative to the $PWD when sbox was run.
+  repeated Copy copy_after = 4;
+
+  // An optional hash of the input files to ensure the textproto files and the sbox rule reruns
+  // when the lists of inputs changes, even if the inputs are not on the command line.
+  optional string input_hash = 5;
+}
+
+// Copy describes a from-to pair of files to copy.  The paths may be relative, the root that they
+// are relative to is specific to the context the Copy is used in and will be different for
+// from and to.
+message Copy {
+  required string from = 1;
+  required string to = 2;
+}
\ No newline at end of file