diff --git a/Makefile b/Makefile
index f54da47a..ad5ee4f5 100644
--- a/Makefile
+++ b/Makefile
@@ -99,6 +99,10 @@ example.deps: PHONY SAVI
 
 # Generate Savi and Crystal source code from CapnProto definitions.
 gen.capnp: PHONY self-hosted.deps $(BUILD)/capnpc-savi $(BUILD)/capnpc-crystal
+	capnp compile \
+		-I"$(shell find self-hosted/deps/github:jemc-savi/CapnProto/* -name src | sort -r -V | head -n 1)/" \
+		self-hosted/src/SaviProto/SaviProto.Artifact.capnp --output=- \
+		| $(BUILD)/capnpc-savi > self-hosted/src/SaviProto/SaviProto.Artifact.capnp.savi
 	capnp compile \
 		-I"$(shell find self-hosted/deps/github:jemc-savi/CapnProto/* -name src | sort -r -V | head -n 1)/" \
 		self-hosted/src/SaviProto/SaviProto.AST.capnp --output=- \
@@ -111,6 +115,10 @@ gen.capnp: PHONY self-hosted.deps $(BUILD)/capnpc-savi $(BUILD)/capnpc-crystal
 		-I"$(shell find self-hosted/deps/github:jemc-savi/CapnProto/* -name src | sort -r -V | head -n 1)/" \
 		self-hosted/src/SaviProto/SaviProto.AST.capnp --output=- \
 		| $(BUILD)/capnpc-crystal > self-hosted/src/SaviProto/SaviProto.AST.capnp.cr
+	capnp compile \
+		-I"$(shell find self-hosted/deps/github:jemc-savi/CapnProto/* -name src | sort -r -V | head -n 1)/" \
+		self-hosted/src/SaviProto/SaviProto.Artifact.capnp --output=- \
+		| $(BUILD)/capnpc-crystal > self-hosted/src/SaviProto/SaviProto.Artifact.capnp.cr
 	capnp compile \
 		-I"$(shell find self-hosted/deps/github:jemc-savi/CapnProto/* -name src | sort -r -V | head -n 1)/" \
 		self-hosted/src/SaviProto/SaviProto.Source.capnp --output=- \
@@ -118,13 +126,19 @@ gen.capnp: PHONY self-hosted.deps $(BUILD)/capnpc-savi $(BUILD)/capnpc-crystal
 gen.capnp.check: gen.capnp
 	git diff --exit-code self-hosted/src/SaviProto
 
-# Update deps for the Self-hosted Savi subprograms.
+# Update deps for the Self-hosted Savi compiler subprograms.
 self-hosted.deps: PHONY SAVI
+	echo && $(SAVI) deps update --cd self-hosted --for savi-lang-broker
+	echo && $(SAVI) deps update --cd self-hosted --for savi-lang-plumber
 	echo && $(SAVI) deps update --cd self-hosted --for savi-lang-parse
 
-# Create the self-hosted Savi parse subprogram.
-self-hosted/bin/savi-lang-parse: $(SAVI) $(shell find self-hosted/src/savi-lang-parse self-hosted/src/SaviProto -name '*.savi')
-	echo && $(SAVI) --cd self-hosted savi-lang-parse --print-perf --backtrace
+# Create the self-hosted Savi compiler subprograms.
+self-hosted/bin/savi-lang-broker: $(SAVI) $(shell find self-hosted/src/savi-lang-broker self-hosted/src/SaviWorker self-hosted/src/SaviProto -name '*.savi')
+	echo && $(SAVI) build --cd self-hosted savi-lang-broker --print-perf --backtrace
+self-hosted/bin/savi-lang-plumber: $(SAVI) $(shell find self-hosted/src/savi-lang-plumber self-hosted/src/SaviWorker self-hosted/src/SaviProto -name '*.savi')
+	echo && $(SAVI) build --cd self-hosted savi-lang-plumber --print-perf --backtrace
+self-hosted/bin/savi-lang-parse: $(SAVI) $(shell find self-hosted/src/savi-lang-parse self-hosted/src/SaviWorker self-hosted/src/SaviProto -name '*.savi')
+	echo && $(SAVI) build --cd self-hosted savi-lang-parse --print-perf --backtrace
 
 # Run spec scripts for self-hosted Savi subprograms.
 spec.self-hosted: PHONY self-hosted/bin/$(name)
diff --git a/self-hosted/manifest.savi b/self-hosted/manifest.savi
index 430a9029..f7cbbd64 100644
--- a/self-hosted/manifest.savi
+++ b/self-hosted/manifest.savi
@@ -1,6 +1,8 @@
-:manifest bin "savi-lang-parse"
-  :sources "src/savi-lang-parse/*.savi"
-  :sources "src/SaviProto/*.savi"
+:manifest lib SaviWorker
+  :sources "src/SaviWorker/*.savi"
+  :sources "src/SaviProto/SaviProto.Source.capnp.savi"
+  :sources "src/SaviProto/SaviProto.Artifact.capnp.savi"
+  :sources "src/SaviProto/SaviProto.Artifact.Path.savi"
 
   :dependency CapnProto v0
     :from "github:jemc-savi/CapnProto"
@@ -9,25 +11,69 @@
   :dependency Map v0
     :from "github:savi-lang/Map"
 
-  :dependency PEG v0
-    :from "github:savi-lang/PEG"
-
   :dependency Time v0
     :from "github:savi-lang/Time"
 
-  :dependency StdIn v0
-    :from "github:savi-lang/StdIn"
-    :depends on ByteStream
-    :depends on IO
-    :depends on OSError
+  :dependency Timer v0
+    :from "github:savi-lang/Timer"
+    :depends on Time
+
+  :dependency CLI v0
+    :from "github:savi-lang/CLI"
+    :depends on Map
+
+  :dependency Logger v0
+    :from "github:savi-lang/Logger"
+    :depends on Time
+
+  :dependency ByteStream v0
+    :from "github:savi-lang/ByteStream"
 
   :dependency IO v0
     :from "github:savi-lang/IO"
     :depends on ByteStream
     :depends on OSError
 
-  :transitive dependency ByteStream v0
-    :from "github:savi-lang/ByteStream"
+  :dependency TCP v0
+    :from "github:savi-lang/TCP"
+    :depends on ByteStream
+    :depends on IO
+    :depends on OSError
+    :depends on IPAddress
+
+  :dependency StdIn v0
+    :from "github:savi-lang/StdIn"
+    :depends on ByteStream
+    :depends on IO
+    :depends on OSError
 
   :transitive dependency OSError v0
     :from "github:savi-lang/OSError"
+
+  :transitive dependency IPAddress v0
+    :from "github:savi-lang/IPAddress"
+
+  :dependency File v0
+    :from "github:savi-lang/File"
+    :depends on OSError
+    :depends on Time
+    :depends on IO
+    :depends on ByteStream
+    :depends on Map
+
+:manifest bin "savi-lang-broker"
+  :sources "src/savi-lang-broker/*.savi"
+  :copies SaviWorker
+
+:manifest bin "savi-lang-plumber"
+  :sources "src/savi-lang-plumber/*.savi"
+  :sources "src/SaviProto/SaviProto.AST.capnp.savi"
+  :copies SaviWorker
+
+:manifest bin "savi-lang-parse"
+  :sources "src/savi-lang-parse/*.savi"
+  :sources "src/SaviProto/SaviProto.AST.capnp.savi"
+  :copies SaviWorker
+
+  :dependency PEG v0
+    :from "github:savi-lang/PEG"
diff --git a/self-hosted/spec/savi-lang-parse.sh b/self-hosted/spec/savi-lang-parse.sh
index 2b96333c..74dce3b7 100755
--- a/self-hosted/spec/savi-lang-parse.sh
+++ b/self-hosted/spec/savi-lang-parse.sh
@@ -5,6 +5,6 @@ cd -- "$(dirname -- "$0")"
 set -e
 
 find savi-lang-parse -name '*.savi' | xargs -I '{}' \
-  sh -c 'cat {} | ../bin/savi-lang-parse > {}.ast.yaml'
+  sh -c 'cat {} | ../bin/savi-lang-parse --test-mode > {}.ast.yaml'
 
 git diff --exit-code savi-lang-parse
diff --git a/self-hosted/src/SaviProto/SaviProto.AST.capnp.cr b/self-hosted/src/SaviProto/SaviProto.AST.capnp.cr
new file mode 100644
index 00000000..c2a8bdc6
--- /dev/null
+++ b/self-hosted/src/SaviProto/SaviProto.AST.capnp.cr
@@ -0,0 +1,665 @@
+  ###
+  # NOTE: This file was auto-generated from a Cap'n Proto file"
+  # using the `capnp` compiler with the `--output=cr` option."
+
+
+struct SaviProto::AST
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def position
+    SaviProto::Source::Position.read_from_pointer(@p.struct(0))
+  end
+
+  def is_none : Bool
+    @p.check_union(0x0, 0)
+  end
+  def none!
+    @p.assert_union!(0x0, 0)
+    nil
+  end
+
+  def is_character : Bool
+    @p.check_union(0x0, 1)
+  end
+  def character!
+    @p.assert_union!(0x0, 1)
+    @p.u64(0x8)
+  end
+
+  def is_positive_integer : Bool
+    @p.check_union(0x0, 2)
+  end
+  def positive_integer!
+    @p.assert_union!(0x0, 2)
+    @p.u64(0x8)
+  end
+
+  def is_negative_integer : Bool
+    @p.check_union(0x0, 3)
+  end
+  def negative_integer!
+    @p.assert_union!(0x0, 3)
+    @p.u64(0x8)
+  end
+
+  def is_floating_point : Bool
+    @p.check_union(0x0, 4)
+  end
+  def floating_point!
+    @p.assert_union!(0x0, 4)
+    @p.f64(0x8)
+  end
+
+  def is_name : Bool
+    @p.check_union(0x0, 5)
+  end
+  def name!
+    @p.assert_union!(0x0, 5)
+    @p.text(1)
+  end
+
+  def is_string : Bool
+    @p.check_union(0x0, 6)
+  end
+  def string!
+    @p.assert_union!(0x0, 6)
+    @p.text(1)
+  end
+
+  def is_string_with_prefix : Bool
+    @p.check_union(0x0, 7)
+  end
+  def string_with_prefix!
+    @p.assert_union!(0x0, 7)
+    SaviProto::AST::AS_stringWithPrefix.read_from_pointer(@p)
+  end
+
+  def is_string_compose : Bool
+    @p.check_union(0x0, 8)
+  end
+  def string_compose!
+    @p.assert_union!(0x0, 8)
+    SaviProto::AST::AS_stringCompose.read_from_pointer(@p)
+  end
+
+  def is_prefix : Bool
+    @p.check_union(0x0, 9)
+  end
+  def prefix!
+    @p.assert_union!(0x0, 9)
+    SaviProto::AST::AS_prefix.read_from_pointer(@p)
+  end
+
+  def is_qualify : Bool
+    @p.check_union(0x0, 10)
+  end
+  def qualify!
+    @p.assert_union!(0x0, 10)
+    SaviProto::AST::AS_qualify.read_from_pointer(@p)
+  end
+
+  def is_group : Bool
+    @p.check_union(0x0, 11)
+  end
+  def group!
+    @p.assert_union!(0x0, 11)
+    SaviProto::AST::Group.read_from_pointer(@p.struct(1))
+  end
+
+  def is_relate : Bool
+    @p.check_union(0x0, 12)
+  end
+  def relate!
+    @p.assert_union!(0x0, 12)
+    SaviProto::AST::AS_relate.read_from_pointer(@p)
+  end
+
+  def is_field_read : Bool
+    @p.check_union(0x0, 13)
+  end
+  def field_read!
+    @p.assert_union!(0x0, 13)
+    SaviProto::AST::AS_fieldRead.read_from_pointer(@p)
+  end
+
+  def is_field_write : Bool
+    @p.check_union(0x0, 14)
+  end
+  def field_write!
+    @p.assert_union!(0x0, 14)
+    SaviProto::AST::AS_fieldWrite.read_from_pointer(@p)
+  end
+
+  def is_field_displace : Bool
+    @p.check_union(0x0, 15)
+  end
+  def field_displace!
+    @p.assert_union!(0x0, 15)
+    SaviProto::AST::AS_fieldDisplace.read_from_pointer(@p)
+  end
+
+  def is_call : Bool
+    @p.check_union(0x0, 16)
+  end
+  def call!
+    @p.assert_union!(0x0, 16)
+    SaviProto::AST::Call.read_from_pointer(@p.struct(1))
+  end
+
+  def is_choice : Bool
+    @p.check_union(0x0, 17)
+  end
+  def choice!
+    @p.assert_union!(0x0, 17)
+    SaviProto::AST::AS_choice.read_from_pointer(@p)
+  end
+
+  def is_loop : Bool
+    @p.check_union(0x0, 18)
+  end
+  def loop!
+    @p.assert_union!(0x0, 18)
+    SaviProto::AST::Loop.read_from_pointer(@p.struct(1))
+  end
+
+  def is_try : Bool
+    @p.check_union(0x0, 19)
+  end
+  def try!
+    @p.assert_union!(0x0, 19)
+    SaviProto::AST::Try.read_from_pointer(@p.struct(1))
+  end
+
+  def is_jump : Bool
+    @p.check_union(0x0, 20)
+  end
+  def jump!
+    @p.assert_union!(0x0, 20)
+    SaviProto::AST::AS_jump.read_from_pointer(@p)
+  end
+
+  def is_yield : Bool
+    @p.check_union(0x0, 21)
+  end
+  def yield!
+    @p.assert_union!(0x0, 21)
+    SaviProto::AST::AS_yield.read_from_pointer(@p)
+  end
+end
+
+struct SaviProto::AST::AS_stringWithPrefix
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def prefix
+    SaviProto::AST::Name.read_from_pointer(@p.struct(1))
+  end
+
+  def string
+    @p.text(2)
+  end
+end
+
+struct SaviProto::AST::AS_stringCompose
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def prefix
+    SaviProto::AST::Name.read_from_pointer(@p.struct(1))
+  end
+
+  def terms
+    CapnProto::List(SaviProto::AST).read_from_pointer(@p.list(2))
+  end
+end
+
+struct SaviProto::AST::AS_prefix
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def op
+    SaviProto::AST::Name.read_from_pointer(@p.struct(1))
+  end
+
+  def term
+    SaviProto::AST.read_from_pointer(@p.struct(2))
+  end
+end
+
+struct SaviProto::AST::AS_qualify
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def term
+    SaviProto::AST.read_from_pointer(@p.struct(1))
+  end
+
+  def group
+    SaviProto::AST::Group.read_from_pointer(@p.struct(2))
+  end
+end
+
+struct SaviProto::AST::AS_relate
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def op
+    SaviProto::AST::Name.read_from_pointer(@p.struct(1))
+  end
+
+  def terms
+    SaviProto::AST::Pair.read_from_pointer(@p.struct(2))
+  end
+end
+
+struct SaviProto::AST::AS_fieldRead
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def field
+    @p.text(1)
+  end
+end
+
+struct SaviProto::AST::AS_fieldWrite
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def field
+    @p.text(1)
+  end
+
+  def value
+    SaviProto::AST.read_from_pointer(@p.struct(2))
+  end
+end
+
+struct SaviProto::AST::AS_fieldDisplace
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def field
+    @p.text(1)
+  end
+
+  def value
+    SaviProto::AST.read_from_pointer(@p.struct(2))
+  end
+end
+
+struct SaviProto::AST::AS_choice
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def branches
+    CapnProto::List(SaviProto::AST::ChoiceBranch).read_from_pointer(@p.list(1))
+  end
+end
+
+struct SaviProto::AST::AS_jump
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def term
+    SaviProto::AST.read_from_pointer(@p.struct(1))
+  end
+
+  def kind
+    SaviProto::AST::JumpKind.new(@p.u16(4))
+  end
+end
+
+struct SaviProto::AST::AS_yield
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def terms
+    CapnProto::List(SaviProto::AST).read_from_pointer(@p.list(1))
+  end
+end
+
+struct SaviProto::AST::Annotation
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 1_u16
+  CAPN_PROTO_POINTER_COUNT = 2_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def position
+    SaviProto::Source::Position.read_from_pointer(@p.struct(0))
+  end
+
+  def target
+    @p.u64(0x0)
+  end
+
+  def value
+    @p.text(1)
+  end
+end
+
+struct SaviProto::AST::Name
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 2_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def position
+    SaviProto::Source::Position.read_from_pointer(@p.struct(0))
+  end
+
+  def value
+    @p.text(1)
+  end
+end
+
+struct SaviProto::AST::Pair
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def position
+    SaviProto::Source::Position.read_from_pointer(@p.struct(0))
+  end
+
+  def left
+    SaviProto::AST.read_from_pointer(@p.struct(1))
+  end
+
+  def right
+    SaviProto::AST.read_from_pointer(@p.struct(2))
+  end
+end
+
+struct SaviProto::AST::Group
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 1_u16
+  CAPN_PROTO_POINTER_COUNT = 2_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def position
+    SaviProto::Source::Position.read_from_pointer(@p.struct(0))
+  end
+
+  def style
+    SaviProto::AST::Group::Style.new(@p.u16(0))
+  end
+
+  def terms
+    CapnProto::List(SaviProto::AST).read_from_pointer(@p.list(1))
+  end
+
+  def has_exclamation
+    @p.bool(0x2, 1)
+  end
+end
+
+enum SaviProto::AST::Group::Style
+  Root = 0
+  Paren = 1
+  Pipe = 2
+  Square = 3
+  Curly = 4
+  Space = 5
+end
+
+struct SaviProto::AST::Call
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 4_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def receiver
+    SaviProto::AST.read_from_pointer(@p.struct(0))
+  end
+
+  def name
+    SaviProto::AST::Name.read_from_pointer(@p.struct(1))
+  end
+
+  def args
+    CapnProto::List(SaviProto::AST).read_from_pointer(@p.list(2))
+  end
+
+  def yield
+    SaviProto::AST::CallYield.read_from_pointer(@p.struct(3))
+  end
+end
+
+struct SaviProto::AST::CallYield
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 2_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def params
+    SaviProto::AST::Group.read_from_pointer(@p.struct(0))
+  end
+
+  def block
+    SaviProto::AST::Group.read_from_pointer(@p.struct(1))
+  end
+end
+
+struct SaviProto::AST::ChoiceBranch
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 2_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def cond
+    SaviProto::AST.read_from_pointer(@p.struct(0))
+  end
+
+  def body
+    SaviProto::AST.read_from_pointer(@p.struct(1))
+  end
+end
+
+struct SaviProto::AST::Loop
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 4_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def initial_cond
+    SaviProto::AST.read_from_pointer(@p.struct(0))
+  end
+
+  def body
+    SaviProto::AST.read_from_pointer(@p.struct(1))
+  end
+
+  def repeat_cond
+    SaviProto::AST.read_from_pointer(@p.struct(2))
+  end
+
+  def else_body
+    SaviProto::AST.read_from_pointer(@p.struct(3))
+  end
+end
+
+struct SaviProto::AST::Try
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 1_u16
+  CAPN_PROTO_POINTER_COUNT = 2_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def body
+    SaviProto::AST.read_from_pointer(@p.struct(0))
+  end
+
+  def else_body
+    SaviProto::AST.read_from_pointer(@p.struct(1))
+  end
+
+  def allow_non_partial_body
+    @p.bool(0x0, 1)
+  end
+end
+
+enum SaviProto::AST::JumpKind
+  Error = 0
+  Return = 1
+  Break = 2
+  Next = 3
+end
+
+struct SaviProto::AST::Declare
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 4_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def terms
+    CapnProto::List(SaviProto::AST).read_from_pointer(@p.list(0))
+  end
+
+  def main_annotation
+    @p.text(1)
+  end
+
+  def body_annotations
+    CapnProto::List(SaviProto::AST::Annotation).read_from_pointer(@p.list(2))
+  end
+
+  def body
+    SaviProto::AST::Group.read_from_pointer(@p.struct(3))
+  end
+end
+
+struct SaviProto::AST::Document
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def source
+    SaviProto::Source.read_from_pointer(@p.struct(0))
+  end
+
+  def declares
+    CapnProto::List(SaviProto::AST::Declare).read_from_pointer(@p.list(1))
+  end
+
+  def bodies
+    CapnProto::List(SaviProto::AST::Group).read_from_pointer(@p.list(2))
+  end
+end
\ No newline at end of file
diff --git a/self-hosted/src/SaviProto/SaviProto.Artifact.Path.savi b/self-hosted/src/SaviProto/SaviProto.Artifact.Path.savi
new file mode 100644
index 00000000..45cf8e6e
--- /dev/null
+++ b/self-hosted/src/SaviProto/SaviProto.Artifact.Path.savi
@@ -0,0 +1,31 @@
+:module SaviProto.Artifact.Path
+  :fun read_root(root Env.Root)
+    File.Path.ReadOnly.new(root, "/tmp/savi-cache") // TODO: configurable
+
+  :fun write_root(root Env.Root)
+    File.Path.WriteOnly.new(root, "/tmp/savi-cache") // TODO: configurable
+
+  :fun read_from(root File.Path.Readable, name SaviProto.Artifact)
+    root.subpath(@_for(name))
+
+  :fun write_to(root File.Path.Writable, name SaviProto.Artifact)
+    root.subpath(@_for(name))
+
+  :fun _for(artifact SaviProto.Artifact, out = String.new(0x200)) String'ref
+    @_for_name(artifact.name, out)
+    out << "+\(artifact.hash).savi-\(artifact.name.kind)"
+    out
+
+  :fun _for_name(name SaviProto.Artifact.Name, out String'ref) None
+    try (p = name.package!, return @_for_package(p, out))
+    try (s = name.source!, return @_for_source(s, out))
+    out << "UNSUPPORTED-ARTIFACT-NAME-TYPE"
+
+  :fun _for_package(name SaviProto.Artifact.Name.Package, out String'ref) None
+    out << "\(name.key)"
+
+  :fun _for_source(name SaviProto.Artifact.Name.Source, out String'ref) None
+    prior_size = out.size
+    @_for_package(name.package, out)
+    if out.size != prior_size out << "-"
+    out << "\(name.key)"
diff --git a/self-hosted/src/SaviProto/SaviProto.Artifact.capnp b/self-hosted/src/SaviProto/SaviProto.Artifact.capnp
new file mode 100644
index 00000000..7ae49ffa
--- /dev/null
+++ b/self-hosted/src/SaviProto/SaviProto.Artifact.capnp
@@ -0,0 +1,42 @@
+@0xf053415649415254; # "\xf0" + "SAVIART"
+
+using Savi = import "/CapnProto.Savi.Meta.capnp";
+$Savi.namespace("SaviProto");
+
+using Source = import "SaviProto.Source.capnp".Source;
+
+struct Artifact {
+  name @0 :Artifact.Name;
+  hash @1 :UInt64;
+
+  struct Name {
+    kind @0 :Text;
+
+    union {
+      package @1 :Artifact.Name.Package;
+      source @2 :Artifact.Name.Source;
+    }
+
+    struct Package {
+      key @0 :Text;
+      path @1 :Text;
+    }
+
+    struct Source {
+      package @0 :Artifact.Name.Package;
+      key @1 :Text;
+      path @2 :Text;
+    }
+  }
+
+  struct Invoke {
+    id @0 :UInt64;
+    inputs @1 :List(Artifact);
+
+    struct Result {
+      id @0 :UInt64;
+      outputs @1 :List(Artifact);
+      errors @2 :List(Source.Error);
+    }
+  }
+}
diff --git a/self-hosted/src/SaviProto/SaviProto.Artifact.capnp.cr b/self-hosted/src/SaviProto/SaviProto.Artifact.capnp.cr
new file mode 100644
index 00000000..14a64692
--- /dev/null
+++ b/self-hosted/src/SaviProto/SaviProto.Artifact.capnp.cr
@@ -0,0 +1,138 @@
+  ###
+  # NOTE: This file was auto-generated from a Cap'n Proto file"
+  # using the `capnp` compiler with the `--output=cr` option."
+
+
+struct SaviProto::Artifact
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 1_u16
+  CAPN_PROTO_POINTER_COUNT = 1_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def name
+    SaviProto::Artifact::Name.read_from_pointer(@p.struct(0))
+  end
+
+  def hash
+    @p.u64(0x0)
+  end
+end
+
+struct SaviProto::Artifact::Name
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 1_u16
+  CAPN_PROTO_POINTER_COUNT = 2_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def kind
+    @p.text(0)
+  end
+
+  def is_package : Bool
+    @p.check_union(0x0, 0)
+  end
+  def package!
+    @p.assert_union!(0x0, 0)
+    SaviProto::Artifact::Name::Package.read_from_pointer(@p.struct(1))
+  end
+
+  def is_source : Bool
+    @p.check_union(0x0, 1)
+  end
+  def source!
+    @p.assert_union!(0x0, 1)
+    SaviProto::Artifact::Name::Source.read_from_pointer(@p.struct(1))
+  end
+end
+
+struct SaviProto::Artifact::Name::Package
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 2_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def key
+    @p.text(0)
+  end
+
+  def path
+    @p.text(1)
+  end
+end
+
+struct SaviProto::Artifact::Name::Source
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def package
+    SaviProto::Artifact::Name::Package.read_from_pointer(@p.struct(0))
+  end
+
+  def key
+    @p.text(1)
+  end
+
+  def path
+    @p.text(2)
+  end
+end
+
+struct SaviProto::Artifact::Invoke
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 1_u16
+  CAPN_PROTO_POINTER_COUNT = 1_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def id
+    @p.u64(0x0)
+  end
+
+  def inputs
+    CapnProto::List(SaviProto::Artifact).read_from_pointer(@p.list(0))
+  end
+end
+
+struct SaviProto::Artifact::Invoke::Result
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 1_u16
+  CAPN_PROTO_POINTER_COUNT = 2_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def id
+    @p.u64(0x0)
+  end
+
+  def outputs
+    CapnProto::List(SaviProto::Artifact).read_from_pointer(@p.list(0))
+  end
+
+  def errors
+    CapnProto::List(SaviProto::Source::Error).read_from_pointer(@p.list(1))
+  end
+end
\ No newline at end of file
diff --git a/self-hosted/src/SaviProto/SaviProto.Artifact.capnp.savi b/self-hosted/src/SaviProto/SaviProto.Artifact.capnp.savi
new file mode 100644
index 00000000..9943e644
--- /dev/null
+++ b/self-hosted/src/SaviProto/SaviProto.Artifact.capnp.savi
@@ -0,0 +1,352 @@
+///
+// NOTE: This file was auto-generated from a Cap'n Proto file
+// using the `capnp` compiler with the `--output=savi` option.
+
+:struct box SaviProto.Artifact
+  :let _p CapnProto.Pointer.Struct
+  :new box read_from_pointer(@_p)
+  :new val read_val_from_pointer(p CapnProto.Pointer.Struct'val): @_p = p
+
+  :const capn_proto_data_word_count U16: 1
+  :const capn_proto_pointer_count U16: 1
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    trace.object(@_p.absolute_address) -> (
+      try trace.property("name", @name_if_set!)
+      try trace.property("hash", @hash_if_set!)
+    )
+
+  :fun name: SaviProto.Artifact.Name.read_from_pointer(@_p.struct(0))
+  :fun name_if_set!: SaviProto.Artifact.Name.read_from_pointer(@_p.struct_if_set!(0))
+
+  :fun hash: @_p.u64(0x0)
+  :fun hash_if_set!: @_p.u64_if_set!(0x0)
+
+:struct box SaviProto.Artifact.Name
+  :let _p CapnProto.Pointer.Struct
+  :new box read_from_pointer(@_p)
+  :new val read_val_from_pointer(p CapnProto.Pointer.Struct'val): @_p = p
+
+  :const capn_proto_data_word_count U16: 1
+  :const capn_proto_pointer_count U16: 2
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    trace.object(@_p.absolute_address) -> (
+      try trace.property("kind", @kind_if_set!)
+      try trace.property("package", @package!)
+      try trace.property("source", @source!)
+    )
+
+  :fun kind: @_p.text(0)
+  :fun kind_if_set!: @_p.text_if_set!(0)
+
+  :fun is_package: @_p.check_union(0x0, 0)
+  :fun package!: @_p.assert_union!(0x0, 0), SaviProto.Artifact.Name.Package.read_from_pointer(@_p.struct(1))
+  :fun package_if_set!: @_p.assert_union!(0x0, 0), SaviProto.Artifact.Name.Package.read_from_pointer(@_p.struct_if_set!(1))
+
+  :fun is_source: @_p.check_union(0x0, 1)
+  :fun source!: @_p.assert_union!(0x0, 1), SaviProto.Artifact.Name.Source.read_from_pointer(@_p.struct(1))
+  :fun source_if_set!: @_p.assert_union!(0x0, 1), SaviProto.Artifact.Name.Source.read_from_pointer(@_p.struct_if_set!(1))
+
+:struct box SaviProto.Artifact.Name.Package
+  :let _p CapnProto.Pointer.Struct
+  :new box read_from_pointer(@_p)
+  :new val read_val_from_pointer(p CapnProto.Pointer.Struct'val): @_p = p
+
+  :const capn_proto_data_word_count U16: 0
+  :const capn_proto_pointer_count U16: 2
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    trace.object(@_p.absolute_address) -> (
+      try trace.property("key", @key_if_set!)
+      try trace.property("path", @path_if_set!)
+    )
+
+  :fun key: @_p.text(0)
+  :fun key_if_set!: @_p.text_if_set!(0)
+
+  :fun path: @_p.text(1)
+  :fun path_if_set!: @_p.text_if_set!(1)
+
+:struct box SaviProto.Artifact.Name.Source
+  :let _p CapnProto.Pointer.Struct
+  :new box read_from_pointer(@_p)
+  :new val read_val_from_pointer(p CapnProto.Pointer.Struct'val): @_p = p
+
+  :const capn_proto_data_word_count U16: 0
+  :const capn_proto_pointer_count U16: 3
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    trace.object(@_p.absolute_address) -> (
+      try trace.property("package", @package_if_set!)
+      try trace.property("key", @key_if_set!)
+      try trace.property("path", @path_if_set!)
+    )
+
+  :fun package: SaviProto.Artifact.Name.Package.read_from_pointer(@_p.struct(0))
+  :fun package_if_set!: SaviProto.Artifact.Name.Package.read_from_pointer(@_p.struct_if_set!(0))
+
+  :fun key: @_p.text(1)
+  :fun key_if_set!: @_p.text_if_set!(1)
+
+  :fun path: @_p.text(2)
+  :fun path_if_set!: @_p.text_if_set!(2)
+
+:struct box SaviProto.Artifact.Invoke
+  :let _p CapnProto.Pointer.Struct
+  :new box read_from_pointer(@_p)
+  :new val read_val_from_pointer(p CapnProto.Pointer.Struct'val): @_p = p
+
+  :const capn_proto_data_word_count U16: 1
+  :const capn_proto_pointer_count U16: 1
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    trace.object(@_p.absolute_address) -> (
+      try trace.property("id", @id_if_set!)
+      try trace.property("inputs", @inputs_if_set!)
+    )
+
+  :fun id: @_p.u64(0x0)
+  :fun id_if_set!: @_p.u64_if_set!(0x0)
+
+  :fun inputs: CapnProto.List(SaviProto.Artifact).read_from_pointer(@_p.list(0))
+  :fun inputs_if_set!: CapnProto.List(SaviProto.Artifact).read_from_pointer(@_p.list_if_set!(0))
+
+:struct box SaviProto.Artifact.Invoke.Result
+  :let _p CapnProto.Pointer.Struct
+  :new box read_from_pointer(@_p)
+  :new val read_val_from_pointer(p CapnProto.Pointer.Struct'val): @_p = p
+
+  :const capn_proto_data_word_count U16: 1
+  :const capn_proto_pointer_count U16: 2
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    trace.object(@_p.absolute_address) -> (
+      try trace.property("id", @id_if_set!)
+      try trace.property("outputs", @outputs_if_set!)
+      try trace.property("errors", @errors_if_set!)
+    )
+
+  :fun id: @_p.u64(0x0)
+  :fun id_if_set!: @_p.u64_if_set!(0x0)
+
+  :fun outputs: CapnProto.List(SaviProto.Artifact).read_from_pointer(@_p.list(0))
+  :fun outputs_if_set!: CapnProto.List(SaviProto.Artifact).read_from_pointer(@_p.list_if_set!(0))
+
+  :fun errors: CapnProto.List(SaviProto.Source.Error).read_from_pointer(@_p.list(1))
+  :fun errors_if_set!: CapnProto.List(SaviProto.Source.Error).read_from_pointer(@_p.list_if_set!(1))
+
+:struct SaviProto.Artifact.Builder
+  :let _p CapnProto.Pointer.Struct.Builder
+  :new from_pointer(@_p)
+  :fun as_reader: SaviProto.Artifact.read_from_pointer(@_p.as_reader)
+
+  :const capn_proto_data_word_count U16: 1
+  :const capn_proto_pointer_count U16: 1
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    @as_reader.trace_data(trace)
+
+  :fun ref copy_data_from(other SaviProto.Artifact) None
+    try (other_name = other.name_if_set!, @name.copy_data_from(other_name))
+    try @_p.set_u64(0x0, other.hash_if_set!, 0)
+
+  :fun ref name: SaviProto.Artifact.Name.Builder.from_pointer(@_p.struct(0, 1, 2))
+  :fun ref name_if_set!: SaviProto.Artifact.Name.Builder.from_pointer(@_p.struct_if_set!(0, 1, 2))
+  :fun ref set_name_to_point_to_existing(existing SaviProto.Artifact.Name.Builder): SaviProto.Artifact.Name.Builder.from_pointer(@_p.set_struct_to_point_to_existing(0, existing._p))
+
+  :fun hash: @_p.u64(0x0)
+  :fun hash_if_set!: @_p.u64_if_set!(0x0)
+  :fun ref "hash="(new_value): @_p.set_u64(0x0, new_value, 0)
+
+:struct SaviProto.Artifact.Name.Builder
+  :let _p CapnProto.Pointer.Struct.Builder
+  :new from_pointer(@_p)
+  :fun as_reader: SaviProto.Artifact.Name.read_from_pointer(@_p.as_reader)
+
+  :const capn_proto_data_word_count U16: 1
+  :const capn_proto_pointer_count U16: 2
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    @as_reader.trace_data(trace)
+
+  :fun ref copy_data_from(other SaviProto.Artifact.Name) None
+    try @_p.set_text(0, "\(other.kind_if_set!)", "")
+    try (other_package = other.package!, @init_package.copy_data_from(other_package))
+    try (other_source = other.source!, @init_source.copy_data_from(other_source))
+
+  :fun ref kind: @_p.text(0)
+  :fun ref kind_if_set!: @_p.text_if_set!(0)
+  :fun ref "kind="(new_value): @_p.set_text(0, new_value, "")
+
+  :fun is_package: @_p.check_union(0x0, 0)
+  :fun ref package!: @_p.assert_union!(0x0, 0), SaviProto.Artifact.Name.Package.Builder.from_pointer(@_p.struct(1, 0, 2))
+  :fun ref package_if_set!: @_p.assert_union!(0x0, 0), SaviProto.Artifact.Name.Package.Builder.from_pointer(@_p.struct_if_set!(1, 0, 2))
+  :fun ref init_package
+    @_p.clear_pointer(1) // package
+    @_p.mark_union(0x0, 0)
+    SaviProto.Artifact.Name.Package.Builder.from_pointer(@_p.struct(1, 0, 2))
+
+  :fun is_source: @_p.check_union(0x0, 1)
+  :fun ref source!: @_p.assert_union!(0x0, 1), SaviProto.Artifact.Name.Source.Builder.from_pointer(@_p.struct(1, 0, 3))
+  :fun ref source_if_set!: @_p.assert_union!(0x0, 1), SaviProto.Artifact.Name.Source.Builder.from_pointer(@_p.struct_if_set!(1, 0, 3))
+  :fun ref init_source
+    @_p.clear_pointer(1) // source
+    @_p.mark_union(0x0, 1)
+    SaviProto.Artifact.Name.Source.Builder.from_pointer(@_p.struct(1, 0, 3))
+
+:struct SaviProto.Artifact.Name.Package.Builder
+  :let _p CapnProto.Pointer.Struct.Builder
+  :new from_pointer(@_p)
+  :fun as_reader: SaviProto.Artifact.Name.Package.read_from_pointer(@_p.as_reader)
+
+  :const capn_proto_data_word_count U16: 0
+  :const capn_proto_pointer_count U16: 2
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    @as_reader.trace_data(trace)
+
+  :fun ref copy_data_from(other SaviProto.Artifact.Name.Package) None
+    try @_p.set_text(0, "\(other.key_if_set!)", "")
+    try @_p.set_text(1, "\(other.path_if_set!)", "")
+
+  :fun ref key: @_p.text(0)
+  :fun ref key_if_set!: @_p.text_if_set!(0)
+  :fun ref "key="(new_value): @_p.set_text(0, new_value, "")
+
+  :fun ref path: @_p.text(1)
+  :fun ref path_if_set!: @_p.text_if_set!(1)
+  :fun ref "path="(new_value): @_p.set_text(1, new_value, "")
+
+:struct SaviProto.Artifact.Name.Source.Builder
+  :let _p CapnProto.Pointer.Struct.Builder
+  :new from_pointer(@_p)
+  :fun as_reader: SaviProto.Artifact.Name.Source.read_from_pointer(@_p.as_reader)
+
+  :const capn_proto_data_word_count U16: 0
+  :const capn_proto_pointer_count U16: 3
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    @as_reader.trace_data(trace)
+
+  :fun ref copy_data_from(other SaviProto.Artifact.Name.Source) None
+    try (other_package = other.package_if_set!, @package.copy_data_from(other_package))
+    try @_p.set_text(1, "\(other.key_if_set!)", "")
+    try @_p.set_text(2, "\(other.path_if_set!)", "")
+
+  :fun ref package: SaviProto.Artifact.Name.Package.Builder.from_pointer(@_p.struct(0, 0, 2))
+  :fun ref package_if_set!: SaviProto.Artifact.Name.Package.Builder.from_pointer(@_p.struct_if_set!(0, 0, 2))
+  :fun ref set_package_to_point_to_existing(existing SaviProto.Artifact.Name.Package.Builder): SaviProto.Artifact.Name.Package.Builder.from_pointer(@_p.set_struct_to_point_to_existing(0, existing._p))
+
+  :fun ref key: @_p.text(1)
+  :fun ref key_if_set!: @_p.text_if_set!(1)
+  :fun ref "key="(new_value): @_p.set_text(1, new_value, "")
+
+  :fun ref path: @_p.text(2)
+  :fun ref path_if_set!: @_p.text_if_set!(2)
+  :fun ref "path="(new_value): @_p.set_text(2, new_value, "")
+
+:struct SaviProto.Artifact.Invoke.Builder
+  :let _p CapnProto.Pointer.Struct.Builder
+  :new from_pointer(@_p)
+  :fun as_reader: SaviProto.Artifact.Invoke.read_from_pointer(@_p.as_reader)
+
+  :const capn_proto_data_word_count U16: 1
+  :const capn_proto_pointer_count U16: 1
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    @as_reader.trace_data(trace)
+
+  :fun ref copy_data_from(other SaviProto.Artifact.Invoke) None
+    try @_p.set_u64(0x0, other.id_if_set!, 0)
+    try @init_inputs_and_copy_data_from(other.inputs_if_set!)
+
+  :fun id: @_p.u64(0x0)
+  :fun id_if_set!: @_p.u64_if_set!(0x0)
+  :fun ref "id="(new_value): @_p.set_u64(0x0, new_value, 0)
+
+  :fun ref inputs: CapnProto.List.Builder(SaviProto.Artifact.Builder).from_pointer(@_p.list(0))
+  :fun ref inputs_if_set!: CapnProto.List.Builder(SaviProto.Artifact.Builder).from_pointer(@_p.list_if_set!(0))
+  :fun ref init_inputs(new_count)
+    CapnProto.List.Builder(SaviProto.Artifact.Builder).from_pointer(@_p.init_list(0, 1, 1, new_count))
+  :fun ref init_inputs_and_copy_data_from(existing CapnProto.List(SaviProto.Artifact))
+    list = CapnProto.List.Builder(SaviProto.Artifact.Builder).from_pointer(@_p.init_list(0, 1, 1, existing.size))
+    existing.each_with_index -> (existing_item, index |
+      new_item = try (list[index]! | next)
+      new_item.copy_data_from(existing_item)
+    )
+    list
+  :fun ref trim_inputs(new_start, new_finish)
+    CapnProto.List.Builder(SaviProto.Artifact.Builder).from_pointer(@_p.trim_list(0, 1, 1, new_start, new_finish))
+
+:struct SaviProto.Artifact.Invoke.Result.Builder
+  :let _p CapnProto.Pointer.Struct.Builder
+  :new from_pointer(@_p)
+  :fun as_reader: SaviProto.Artifact.Invoke.Result.read_from_pointer(@_p.as_reader)
+
+  :const capn_proto_data_word_count U16: 1
+  :const capn_proto_pointer_count U16: 2
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    @as_reader.trace_data(trace)
+
+  :fun ref copy_data_from(other SaviProto.Artifact.Invoke.Result) None
+    try @_p.set_u64(0x0, other.id_if_set!, 0)
+    try @init_outputs_and_copy_data_from(other.outputs_if_set!)
+    try @init_errors_and_copy_data_from(other.errors_if_set!)
+
+  :fun id: @_p.u64(0x0)
+  :fun id_if_set!: @_p.u64_if_set!(0x0)
+  :fun ref "id="(new_value): @_p.set_u64(0x0, new_value, 0)
+
+  :fun ref outputs: CapnProto.List.Builder(SaviProto.Artifact.Builder).from_pointer(@_p.list(0))
+  :fun ref outputs_if_set!: CapnProto.List.Builder(SaviProto.Artifact.Builder).from_pointer(@_p.list_if_set!(0))
+  :fun ref init_outputs(new_count)
+    CapnProto.List.Builder(SaviProto.Artifact.Builder).from_pointer(@_p.init_list(0, 1, 1, new_count))
+  :fun ref init_outputs_and_copy_data_from(existing CapnProto.List(SaviProto.Artifact))
+    list = CapnProto.List.Builder(SaviProto.Artifact.Builder).from_pointer(@_p.init_list(0, 1, 1, existing.size))
+    existing.each_with_index -> (existing_item, index |
+      new_item = try (list[index]! | next)
+      new_item.copy_data_from(existing_item)
+    )
+    list
+  :fun ref trim_outputs(new_start, new_finish)
+    CapnProto.List.Builder(SaviProto.Artifact.Builder).from_pointer(@_p.trim_list(0, 1, 1, new_start, new_finish))
+
+  :fun ref errors: CapnProto.List.Builder(SaviProto.Source.Error.Builder).from_pointer(@_p.list(1))
+  :fun ref errors_if_set!: CapnProto.List.Builder(SaviProto.Source.Error.Builder).from_pointer(@_p.list_if_set!(1))
+  :fun ref init_errors(new_count)
+    CapnProto.List.Builder(SaviProto.Source.Error.Builder).from_pointer(@_p.init_list(1, 0, 3, new_count))
+  :fun ref init_errors_and_copy_data_from(existing CapnProto.List(SaviProto.Source.Error))
+    list = CapnProto.List.Builder(SaviProto.Source.Error.Builder).from_pointer(@_p.init_list(1, 0, 3, existing.size))
+    existing.each_with_index -> (existing_item, index |
+      new_item = try (list[index]! | next)
+      new_item.copy_data_from(existing_item)
+    )
+    list
+  :fun ref trim_errors(new_start, new_finish)
+    CapnProto.List.Builder(SaviProto.Source.Error.Builder).from_pointer(@_p.trim_list(1, 0, 3, new_start, new_finish))
diff --git a/self-hosted/src/SaviProto/SaviProto.Source.capnp b/self-hosted/src/SaviProto/SaviProto.Source.capnp
index 369f2c3a..0895f329 100644
--- a/self-hosted/src/SaviProto/SaviProto.Source.capnp
+++ b/self-hosted/src/SaviProto/SaviProto.Source.capnp
@@ -21,4 +21,10 @@ struct Source {
     absoluteManifestDirectoryPath @0 :Text;
     name @1 :Text;
   }
+
+  struct Error {
+    position @0 :Position;
+    message @1 :Text;
+    extraInfo @2 :List(Source.Error);
+  }
 }
diff --git a/self-hosted/src/SaviProto/SaviProto.Source.capnp.cr b/self-hosted/src/SaviProto/SaviProto.Source.capnp.cr
new file mode 100644
index 00000000..f336d76f
--- /dev/null
+++ b/self-hosted/src/SaviProto/SaviProto.Source.capnp.cr
@@ -0,0 +1,104 @@
+  ###
+  # NOTE: This file was auto-generated from a Cap'n Proto file"
+  # using the `capnp` compiler with the `--output=cr` option."
+
+
+struct SaviProto::Source
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 1_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def absolute_file_path
+    @p.text(0)
+  end
+
+  def content_for_non_file
+    @p.text(1)
+  end
+
+  def content_hash64
+    @p.u64(0x0)
+  end
+
+  def package
+    SaviProto::Source::Package.read_from_pointer(@p.struct(2))
+  end
+end
+
+struct SaviProto::Source::Position
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 2_u16
+  CAPN_PROTO_POINTER_COUNT = 1_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def source
+    SaviProto::Source.read_from_pointer(@p.struct(0))
+  end
+
+  def offset
+    @p.u32(0x0)
+  end
+
+  def size
+    @p.u32(0x4)
+  end
+
+  def row
+    @p.u32(0x8)
+  end
+
+  def column
+    @p.u32(0xc)
+  end
+end
+
+struct SaviProto::Source::Package
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 2_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def absolute_manifest_directory_path
+    @p.text(0)
+  end
+
+  def name
+    @p.text(1)
+  end
+end
+
+struct SaviProto::Source::Error
+  def initialize(@p : CapnProto::Pointer::Struct)
+  end
+  private def self.new; end
+  def self.read_from_pointer(p); obj = allocate; obj.initialize(p); obj; end
+
+  CAPN_PROTO_DATA_WORD_COUNT = 0_u16
+  CAPN_PROTO_POINTER_COUNT = 3_u16
+  def capn_proto_address : UInt64; @p.capn_proto_address; end
+
+  def position
+    SaviProto::Source::Position.read_from_pointer(@p.struct(0))
+  end
+
+  def message
+    @p.text(1)
+  end
+
+  def extra_info
+    CapnProto::List(SaviProto::Source::Error).read_from_pointer(@p.list(2))
+  end
+end
\ No newline at end of file
diff --git a/self-hosted/src/SaviProto/SaviProto.Source.capnp.savi b/self-hosted/src/SaviProto/SaviProto.Source.capnp.savi
index 8ab8340e..83a01a38 100644
--- a/self-hosted/src/SaviProto/SaviProto.Source.capnp.savi
+++ b/self-hosted/src/SaviProto/SaviProto.Source.capnp.savi
@@ -88,6 +88,32 @@
   :fun name: @_p.text(1)
   :fun name_if_set!: @_p.text_if_set!(1)
 
+:struct box SaviProto.Source.Error
+  :let _p CapnProto.Pointer.Struct
+  :new box read_from_pointer(@_p)
+  :new val read_val_from_pointer(p CapnProto.Pointer.Struct'val): @_p = p
+
+  :const capn_proto_data_word_count U16: 0
+  :const capn_proto_pointer_count U16: 3
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    trace.object(@_p.absolute_address) -> (
+      try trace.property("position", @position_if_set!)
+      try trace.property("message", @message_if_set!)
+      try trace.property("extra_info", @extra_info_if_set!)
+    )
+
+  :fun position: SaviProto.Source.Position.read_from_pointer(@_p.struct(0))
+  :fun position_if_set!: SaviProto.Source.Position.read_from_pointer(@_p.struct_if_set!(0))
+
+  :fun message: @_p.text(1)
+  :fun message_if_set!: @_p.text_if_set!(1)
+
+  :fun extra_info: CapnProto.List(SaviProto.Source.Error).read_from_pointer(@_p.list(2))
+  :fun extra_info_if_set!: CapnProto.List(SaviProto.Source.Error).read_from_pointer(@_p.list_if_set!(2))
+
 :struct SaviProto.Source.Builder
   :let _p CapnProto.Pointer.Struct.Builder
   :new from_pointer(@_p)
@@ -187,3 +213,43 @@
   :fun ref name: @_p.text(1)
   :fun ref name_if_set!: @_p.text_if_set!(1)
   :fun ref "name="(new_value): @_p.set_text(1, new_value, "")
+
+:struct SaviProto.Source.Error.Builder
+  :let _p CapnProto.Pointer.Struct.Builder
+  :new from_pointer(@_p)
+  :fun as_reader: SaviProto.Source.Error.read_from_pointer(@_p.as_reader)
+
+  :const capn_proto_data_word_count U16: 0
+  :const capn_proto_pointer_count U16: 3
+  :fun capn_proto_address U64: @_p.capn_proto_address
+
+  :is TraceData
+  :fun trace_data(trace TraceData.Observer)
+    @as_reader.trace_data(trace)
+
+  :fun ref copy_data_from(other SaviProto.Source.Error) None
+    try (other_position = other.position_if_set!, @position.copy_data_from(other_position))
+    try @_p.set_text(1, "\(other.message_if_set!)", "")
+    try @init_extra_info_and_copy_data_from(other.extra_info_if_set!)
+
+  :fun ref position: SaviProto.Source.Position.Builder.from_pointer(@_p.struct(0, 2, 1))
+  :fun ref position_if_set!: SaviProto.Source.Position.Builder.from_pointer(@_p.struct_if_set!(0, 2, 1))
+  :fun ref set_position_to_point_to_existing(existing SaviProto.Source.Position.Builder): SaviProto.Source.Position.Builder.from_pointer(@_p.set_struct_to_point_to_existing(0, existing._p))
+
+  :fun ref message: @_p.text(1)
+  :fun ref message_if_set!: @_p.text_if_set!(1)
+  :fun ref "message="(new_value): @_p.set_text(1, new_value, "")
+
+  :fun ref extra_info: CapnProto.List.Builder(SaviProto.Source.Error.Builder).from_pointer(@_p.list(2))
+  :fun ref extra_info_if_set!: CapnProto.List.Builder(SaviProto.Source.Error.Builder).from_pointer(@_p.list_if_set!(2))
+  :fun ref init_extra_info(new_count)
+    CapnProto.List.Builder(SaviProto.Source.Error.Builder).from_pointer(@_p.init_list(2, 0, 3, new_count))
+  :fun ref init_extra_info_and_copy_data_from(existing CapnProto.List(SaviProto.Source.Error))
+    list = CapnProto.List.Builder(SaviProto.Source.Error.Builder).from_pointer(@_p.init_list(2, 0, 3, existing.size))
+    existing.each_with_index -> (existing_item, index |
+      new_item = try (list[index]! | next)
+      new_item.copy_data_from(existing_item)
+    )
+    list
+  :fun ref trim_extra_info(new_start, new_finish)
+    CapnProto.List.Builder(SaviProto.Source.Error.Builder).from_pointer(@_p.trim_list(2, 0, 3, new_start, new_finish))
diff --git a/self-hosted/src/SaviWorker/SaviWorker.TCP.savi b/self-hosted/src/SaviWorker/SaviWorker.TCP.savi
new file mode 100644
index 00000000..a0f5dd5e
--- /dev/null
+++ b/self-hosted/src/SaviWorker/SaviWorker.TCP.savi
@@ -0,0 +1,180 @@
+:trait tag SaviWorker.TCP.Connection.Registry
+  :be register(kind String, worker SaviWorker.TCP.Connection)
+  :be deregister(kind String, worker SaviWorker.TCP.Connection)
+
+:actor SaviWorker.TCP.Listener
+  :is IO.Actor(IO.Action)
+
+  :const default_port I64: 43434 // TODO: register with IANA
+
+  :let registry SaviWorker.TCP.Connection.Registry
+  :let log _Log
+  :let io TCP.Listen.Engine
+  :let workers: Map(String, Array(SaviWorker.TCP.Connection)).new
+
+  :new (@registry, @log, ticket)
+    @io = TCP.Listen.Engine.new(@, --ticket)
+
+  :fun ref io_react(action IO.Action)
+    case action == (
+    | IO.Action.Opened |
+      @log.info -> (
+        port = try @io.listen_port_number!
+        "Listening on port: \(port)"
+      )
+    | IO.Action.OpenFailed |
+      @log.error -> (
+        "Failed to listen: \(@io.listen_error)"
+      )
+    | IO.Action.Read |
+      @io.pending_connections -> (ticket |
+        SaviWorker.TCP.Connection.new(@registry, @log, --ticket)
+      )
+    | IO.Action.Closed |
+      @log.info -> ("Stopped listening")
+    )
+    @
+
+:actor SaviWorker.TCP.Connection
+  :is IO.Actor(IO.Action)
+
+  :let registry SaviWorker.TCP.Connection.Registry
+  :let log _Log
+  :let io TCP.Engine
+  :var _ping_number U64: 0
+  :var _pong_number U64: 0
+  :const ping_miss_max U64: 3
+
+  :new (@registry, @log, ticket)
+    @io = TCP.Engine.accept(@, --ticket)
+    @log.info -> ("Accepted connection from worker")
+
+  :fun ref io_react(action IO.Action)
+    case action == (
+    | IO.Action.Read |
+      try (
+        while True (
+          @handle_message(@io.read_stream.extract_frame_u32_be!)
+        )
+      )
+    | IO.Action.Closed |
+      @log.info -> ("Closed connection from worker")
+    )
+    @
+
+  :fun ref send_message(message Bytes)
+    @io.write_stream.push_native_u32(message.size.u32.native_to_be)
+    @io.write_stream << message
+    try @io.flush! // TODO: do we need to handle failure here in some way?
+
+  :var kind: ""
+  :fun ref handle_message(message Bytes)
+    case (
+    | @kind.is_empty |
+      @kind = String.from_bytes(message)
+      @registry.register(@kind, @)
+    | message == b"PONG" |
+      @_pong_number = @_ping_number
+    |
+      segments = CapnProto.Segments.new
+      segment = CapnProto.Segment.new_from_bytes(segments, message.clone) // TODO: no clone
+
+      try (
+        m = CapnProto.Message(SaviProto.Artifact.Invoke.Result)
+          .from_val_segments!(segments.take_val_segments)
+        @log.debug -> ("Received: \(Inspect[m.root])")
+      |
+        @log.error -> ("Failed to parse invoke result")
+      )
+    )
+
+  :be invoke(message CapnProto.Message(SaviProto.Artifact.Invoke)'val)
+    id = message.root.id
+    @log.info -> ("Invoking with id: \(id)")
+
+    try (
+      @send_message(message.val_buffers.first!) // TODO: not just the first segment
+    |
+      @log.error -> ("Failed to get invoke message buffer")
+    )
+
+  :be ping(number U64)
+    @send_message(b"PING")
+
+    @_ping_number = number
+    if @_pong_number.is_zero (
+      @_pong_number = @_ping_number
+      return
+    )
+
+    if @_ping_number - @_pong_number > @ping_miss_max (
+      @log.warn -> ("Ping timeout")
+      @registry.deregister(@kind, @)
+    )
+
+  :be close
+    @io.close
+    @log.info -> ("Closed worker connection")
+
+:actor SaviWorker.TCP
+  :is IO.Actor(IO.Action)
+  :is SaviWorker.ResultSink
+
+  :let worker SaviWorker
+  :let log _Log
+  :let io TCP.Engine
+
+  :new (@worker, @log, ticket)
+    @worker.set_result_sink(@)
+    @io = TCP.Engine.new(@, --ticket)
+
+  :fun ref io_react(action IO.Action)
+    case action == (
+    | IO.Action.Opened |
+      @log.info -> ("Connecting as worker with kind: \(@worker.kind)")
+      @send_message(@worker.kind.as_bytes)
+    | IO.Action.OpenFailed |
+      @log.error -> ("Failed to connect")
+    | IO.Action.Read |
+      try (
+        while True (
+          @handle_message(@io.read_stream.extract_frame_u32_be!)
+        )
+      )
+    | IO.Action.Closed |
+      @log.info -> ("Disconnected")
+    )
+    @
+
+  :fun ref send_message(message Bytes)
+    @io.write_stream.push_native_u32(message.size.u32.native_to_be)
+    @io.write_stream << message
+    try @io.flush! // TODO: do we need to handle failure here in some way?
+
+  :fun ref handle_message(bytes Bytes'iso)
+    case (
+    | bytes == b"PING" |
+      @send_message(b"PONG")
+    |
+      invoke = try (
+        segments = CapnProto.Segments.new
+        segment = CapnProto.Segment.new_from_bytes(segments, --bytes)
+        @worker.work(
+          CapnProto.Message(SaviProto.Artifact.Invoke)
+            .from_val_segments!(segments.take_val_segments)
+        )
+      |
+        @log.error -> ("Failed to parse invoke message")
+        return
+      )
+    )
+
+  :be work_result(message CapnProto.Message(SaviProto.Artifact.Invoke.Result)'val)
+    try (
+      @log.debug -> ("Sending: \(Inspect[message.root])")
+      @send_message(message.val_buffers.first!) // TODO: not just the first segment
+      @log.info -> ("Finished processing invoke")
+    |
+      @log.error -> ("Failed to get result message buffer")
+      return
+    )
diff --git a/self-hosted/src/SaviWorker/SaviWorker.savi b/self-hosted/src/SaviWorker/SaviWorker.savi
new file mode 100644
index 00000000..65ee7323
--- /dev/null
+++ b/self-hosted/src/SaviWorker/SaviWorker.savi
@@ -0,0 +1,7 @@
+:trait tag SaviWorker
+  :fun non kind String
+  :be set_result_sink(sink SaviWorker.ResultSink)
+  :be work(invoke CapnProto.Message(SaviProto.Artifact.Invoke)'val)
+
+:trait tag SaviWorker.ResultSink
+  :be work_result(result CapnProto.Message(SaviProto.Artifact.Invoke.Result)'val)
\ No newline at end of file
diff --git a/self-hosted/src/SaviWorker/_Log.savi b/self-hosted/src/SaviWorker/_Log.savi
new file mode 100644
index 00000000..02040d4c
--- /dev/null
+++ b/self-hosted/src/SaviWorker/_Log.savi
@@ -0,0 +1,3 @@
+:alias _Log: Logger(
+  Logger.Formatter.StringWithLevelAndTimestamp
+)
diff --git a/self-hosted/src/savi-lang-broker/Main.savi b/self-hosted/src/savi-lang-broker/Main.savi
new file mode 100644
index 00000000..ce9fa5e3
--- /dev/null
+++ b/self-hosted/src/savi-lang-broker/Main.savi
@@ -0,0 +1,97 @@
+:class _CLI
+  :var port: SaviWorker.TCP.Listener.default_port
+  :var trigger_port: _Trigger.TCP.Listener.default_port
+
+  :is CLI.Option.Data
+  :fun non define_cli_options(defs CLI.Option.Defs) None
+    defs.i64("port", 'p')
+    defs.i64("trigger-port", 'P')
+
+  :fun ref trace_data_mutable(trace TraceData.Mutator) None
+    trace.object(identity_digest_of @) -> (key |
+      case key == (
+      | "port"         | trace.replace_i64(@port)         -> (v | @port = v)
+      | "trigger-port" | trace.replace_i64(@trigger_port) -> (v | @trigger_port = v)
+      )
+    )
+
+:actor Main
+  :let env Env
+  :new (@env)
+    cli = try (
+      CLI.Parser(_CLI).parse!(_CLI.new, @env.args)
+    | error |
+      @env.err.print(error.message)
+      @env.exit_code = 1
+      return
+    )
+    log = _Log.new(@env.err, Logger.Level.Debug)
+    tcp = TCP.auth(@env.root)
+
+    broker = SaviBroker.new(log)
+    SaviWorker.TCP.Listener.new(
+      broker, log, tcp.listen.on("0.0.0.0", "\(cli.options.port)")
+    )
+    _Trigger.TCP.Listener.new(
+      broker, log, tcp.listen.on("0.0.0.0", "\(cli.options.trigger_port)")
+    )
+
+
+:actor _Trigger.TCP.Listener
+  :is IO.Actor(IO.Action)
+
+  :const default_port I64: 23232 // TODO: register with IANA
+
+  :let broker SaviBroker
+  :let log _Log
+  :let io TCP.Listen.Engine
+
+  :new (@broker, @log, ticket)
+    @io = TCP.Listen.Engine.new(@, --ticket)
+
+  :fun ref io_react(action IO.Action)
+    case action == (
+    | IO.Action.Opened |
+      @log.info -> (
+        port = try @io.listen_port_number!
+        "Listening for triggers on port: \(port)"
+      )
+    | IO.Action.OpenFailed |
+      @log.error -> (
+        "Failed to listen for triggers: \(@io.listen_error)"
+      )
+    | IO.Action.Read |
+      @io.pending_connections -> (ticket |
+        _Trigger.TCP.Connection.new(@broker, @log, --ticket)
+      )
+    | IO.Action.Closed |
+      @log.info -> ("Stopped listening for triggers")
+    )
+    @
+
+:actor _Trigger.TCP.Connection
+  :is IO.Actor(IO.Action)
+
+  :let broker SaviBroker
+  :let log _Log
+  :let io TCP.Engine
+
+  :new (@broker, @log, ticket)
+    @io = TCP.Engine.accept(@, --ticket)
+    @log.info -> ("Accepted connection from trigger client")
+
+  :fun ref io_react(action IO.Action)
+    case action == (
+    | IO.Action.Read |
+      try (
+        while True (
+          @handle_message(@io.read_stream.extract_line!)
+        )
+      )
+    | IO.Action.Closed |
+      @log.info -> ("Closed connection from worker")
+    )
+    @
+
+  :fun ref handle_message(message Bytes)
+    @broker.trigger_manifest_parse(message.as_string)
diff --git a/self-hosted/src/savi-lang-broker/SaviBroker.savi b/self-hosted/src/savi-lang-broker/SaviBroker.savi
new file mode 100644
index 00000000..4a208284
--- /dev/null
+++ b/self-hosted/src/savi-lang-broker/SaviBroker.savi
@@ -0,0 +1,99 @@
+:actor SaviBroker
+  :is SaviWorker.TCP.Connection.Registry
+
+  :const ping_interval_seconds U64: 1
+  :let log _Log
+  :let _ping_timer _PingTimer
+  :let _workers: Map(String, SaviBroker.WorkerPool).new
+  :var _next_id U64: 0
+
+  :new (@log)
+    @_ping_timer = _PingTimer.new(@, @ping_interval_seconds)
+
+  :be register(kind String, conn SaviWorker.TCP.Connection)
+    pool = @_workers.get_or_insert(kind) -> (SaviBroker.WorkerPool.new)
+    pool.register(kind, conn)
+    @log.info -> ("Registered a worker of kind: \(kind)")
+
+  :be deregister(kind String, conn SaviWorker.TCP.Connection)
+    try (
+      pool = @_workers[kind]!
+      pool.deregister(kind, conn)
+      @log.info -> ("Deregistered a worker of kind: \(kind)")
+    )
+
+  :be ping(number U64)
+    @_workers.each_value -> (pool |
+      pool.workers.each -> (worker |
+        worker.conn.ping(number)
+      )
+    )
+
+  :be invoke(kind String, message CapnProto.Message(SaviProto.Artifact.Invoke)'val)
+    pool = @_workers.get_or_insert(kind) -> (SaviBroker.WorkerPool.new)
+    pool.invoke(message)
+
+  :be trigger_manifest_parse(path String)
+    message = CapnProto.Message.Builder(SaviProto.Artifact.Invoke.Builder).new(0x4000)
+    message.root.id = (@_next_id += 1)
+
+    inputs = message.root.init_inputs(1)
+    try (
+      input = inputs[0]!
+      input.name.kind = "trigger-parse"
+
+      source = input.name.init_source
+      source.key = "manifest"
+      source.path = path
+    )
+
+    try (
+      @invoke("parse"
+        CapnProto.Message(SaviProto.Artifact.Invoke).from_val_segments!(
+          message.take_val_segments
+        )
+      )
+    |
+      @log.error -> ("Failed to convert invoke to val message")
+    )
+
+:class SaviBroker.WorkerPool
+  :let workers Array(SaviBroker.WorkerEntry)'ref: []
+  :let queued Array(CapnProto.Message(SaviProto.Artifact.Invoke)'val)'ref: []
+  :var _round_robin_index USize: 0
+
+  :fun ref register(kind String, conn SaviWorker.TCP.Connection)
+    @workers << SaviBroker.WorkerEntry.new(kind, conn)
+    @_drain_queue
+
+  :fun ref deregister(kind String, conn SaviWorker.TCP.Connection)
+    try @workers.delete_at!(@workers.find_index! -> (w | w.conn === conn))
+    // TODO: pull out any pending messages and requeue them
+    conn.close
+
+  :fun ref invoke(message CapnProto.Message(SaviProto.Artifact.Invoke)'val) None
+    if @workers.is_empty (
+      @queued << message
+      return
+    )
+
+    if @_round_robin_index >= @workers.size (
+      @_round_robin_index = 0
+    )
+    try @workers[@_round_robin_index]!.invoke(message)
+    @_round_robin_index += 1
+
+  :fun ref _drain_queue None
+    return if @queued.is_empty || @workers.is_empty
+    @queued.each -> (message | @invoke(message))
+    @queued.clear
+
+:struct SaviBroker.WorkerEntry
+  :let kind String
+  :let conn SaviWorker.TCP.Connection
+  :let pending_invokes: Map(U64, CapnProto.Message(SaviProto.Artifact.Invoke)'val).new
+  :new (@kind, @conn)
+
+  :fun ref invoke(message CapnProto.Message(SaviProto.Artifact.Invoke)'val)
+    @pending_invokes[message.root.id] = message
+    @conn.invoke(message)
diff --git a/self-hosted/src/savi-lang-broker/_PingTimer.savi b/self-hosted/src/savi-lang-broker/_PingTimer.savi
new file mode 100644
index 00000000..8389222b
--- /dev/null
+++ b/self-hosted/src/savi-lang-broker/_PingTimer.savi
@@ -0,0 +1,17 @@
+
+:trait tag _PingTimerTarget
+  :be ping(number U64)
+
+:actor _PingTimer
+  :is Timer.Actor
+  :let timer Timer.Engine
+  :let target _PingTimerTarget
+  :var number U64: 0
+
+  :new (@target, interval_seconds)
+    interval = Time.Duration.seconds(interval_seconds)
+    @timer = Timer.Engine.new(@, interval)
+
+  :fun ref timer_react @
+    @target.ping(@number += 1)
+    @
diff --git a/self-hosted/src/savi-lang-parse/Main.TestMode.savi b/self-hosted/src/savi-lang-parse/Main.TestMode.savi
new file mode 100644
index 00000000..610ba9f6
--- /dev/null
+++ b/self-hosted/src/savi-lang-parse/Main.TestMode.savi
@@ -0,0 +1,52 @@
+:actor Main.TestMode
+  :is StdIn.Actor
+  :let env Env
+  :let log _Log
+  :let io StdIn.Engine
+  :let _reader: CapnProto.Segments.Reader.new
+  :new (@env, @log)
+    @io = StdIn.Engine.new(@)
+    StdIn.Ticket.get(@env.root.ticket_issuer, @)
+
+  :fun ref io_react(action IO.Action)
+    case action == (
+    | IO.Action.Closed |
+      @handle_code(@io.read_stream.extract_all.as_string)
+    )
+    @
+
+  :fun handle_code(code String)
+    nanos = Time.Measure.nanoseconds -> (
+      printer = PEG.Parser(_Token, String).new(_Grammar.new, _TreePrinter.new)
+
+      builder = _TreeBuilder.new
+      builder.code = code
+      parser = PEG.Parser(
+        _Token
+        CapnProto.Message.Builder(SaviProto.AST.Document.Builder)
+      ).new(_Grammar.new, builder)
+
+      try (
+        Inspect.out("Parsing code: \(code)")
+        message = parser.parse!(code)
+
+        if builder.error.has_any (
+          @env.err.print(printer.parse!(code))
+
+          builder.error.each -> (info |
+            @env.err.print("\(info.code) at \(info.at.start)...\(info.at.end)")
+          )
+        |
+          @env.out.print(Inspect.TraceData.Printer.Deterministic.print(message.root))
+          // message.take_val_buffers.each -> (buffer |
+          //   @env.out.write(buffer.as_string)
+          // )
+        )
+      |
+        @env.err.print(
+          "Parse error at byte \(parser.last_parse_byte_size)"
+        )
+      )
+    )
+
+    @env.err.print("It took \(nanos.f64 / 1e6) milliseconds...")
diff --git a/self-hosted/src/savi-lang-parse/Main.savi b/self-hosted/src/savi-lang-parse/Main.savi
index 6bc0b45e..044ee872 100644
--- a/self-hosted/src/savi-lang-parse/Main.savi
+++ b/self-hosted/src/savi-lang-parse/Main.savi
@@ -1,50 +1,199 @@
+:class _CLI
+  :var test_mode: False
+  :var port: SaviWorker.TCP.Listener.default_port
+
+  :is CLI.Option.Data
+  :fun non define_cli_options(defs CLI.Option.Defs) None
+    defs.bool("test-mode", 't')
+    defs.i64("port", 'p')
+
+  :fun ref trace_data_mutable(trace TraceData.Mutator) None
+    trace.object(identity_digest_of @) -> (key |
+      case key == (
+      | "test-mode" | trace.replace_bool(@test_mode) -> (v | @test_mode = v)
+      | "port" | trace.replace_i64(@port) -> (v | @port = v)
+      )
+    )
+
 :actor Main
-  :is StdIn.Actor
   :let env Env
-  :let io StdIn.Engine
-  :let _reader: CapnProto.Segments.Reader.new
   :new (@env)
-    @io = StdIn.Engine.new(@)
-    StdIn.Ticket.get(@env.root.ticket_issuer, @)
-
-  :fun ref io_react(action IO.Action)
-    case action == (
-    | IO.Action.Closed |
-      @handle_code(@io.read_stream.extract_all.as_string)
-    )
-    @
-
-  :fun handle_code(code String)
-    nanos = Time.Measure.nanoseconds -> (
-      printer = PEG.Parser(_Token, String).new(_Grammar.new, _TreePrinter.new)
-
-      builder = _TreeBuilder.new
-      builder.code = code
-      parser = PEG.Parser(
-        _Token
-        CapnProto.Message.Builder(SaviProto.AST.Document.Builder)
-      ).new(_Grammar.new, builder)
-
-      try (
-        message = parser.parse!(code)
-
-        if builder.error.has_any (
-          @env.err.print(printer.parse!(code))
-
-          builder.error.each -> (info |
-            @env.err.print("\(info.code) at \(info.at.start)...\(info.at.end)")
-          )
-        |
-          @env.out.print(Inspect.TraceData.Printer.Deterministic.print(message.root))
-          // message.take_val_buffers.each -> (buffer |
-          //   @env.out.write(buffer.as_string)
-          // )
-        )
-      |
-        @env.err.print(
-          "Parse error at byte \(parser.last_parse_byte_size)"
-        )
+    cli = try (
+      CLI.Parser(_CLI).parse!(_CLI.new, @env.args)
+    | error |
+      @env.err.print(error.message)
+      @env.exit_code = 1
+      return
+    )
+    log = _Log.new(@env.err, Logger.Level.Debug)
+
+    if cli.options.test_mode (
+      Main.TestMode.new(@env, log)
+    |
+      SaviWorker.TCP.new(
+        _Worker.new(@env, log)
+        log
+        TCP.auth(@env.root).connect.to("0.0.0.0", "\(cli.options.port)")
+      )
+    )
+
+:actor _Worker
+  :is SaviWorker
+
+  :let env Env
+  :let log _Log
+  :let file_loader: File.Loader.new
+  :let file_dumper: File.Dumper.new
+  :new (@env, @log)
+
+  :fun non kind: "parse"
+  :var result_sink (SaviWorker.ResultSink | None): None
+  :let pending_results Array(
+    CapnProto.Message.Builder(SaviProto.Artifact.Invoke.Result.Builder)
+  ): [] // TODO: This isn't enough to handle a future scenario where the file loading/dumping isn't causal
+
+  :be set_result_sink(sink): @result_sink = sink
+
+  :fun ref send_result None
+    result = try (@pending_results.shift! |
+      @log.error -> ("No pending result in the stack")
+      return
+    )
+
+    final = try (
+      CapnProto.Message(SaviProto.Artifact.Invoke.Result).from_val_segments!(
+        result.take_val_segments
       )
+    |
+      @log.error -> ("Failed to finalize result")
+      return
+    )
+
+    try (
+      @result_sink.not!(None).work_result(final)
+    |
+      @log.error -> ("No result sink set")
+    )
+
+  :fun ref prep_result None
+    :yields SaviProto.Artifact.Invoke.Result.Builder
+
+    result = try (@pending_results.first! |
+      @log.error -> ("No pending result in the stack")
+      return
+    )
+
+    yield result.root
+
+  :fun ref send_error(message String) None
+    @prep_result -> (result |
+      result.init_errors(1)
+      try (result.errors[0]!.message = message) // "cannot fail"
+    )
+    @send_result
+
+  :fun ref send_error_bug(message String) None
+    @send_error(message)
+    @log.error -> (message)
+
+  :be work(invoke CapnProto.Message(SaviProto.Artifact.Invoke)'val)
+    result = CapnProto.Message.Builder(SaviProto.Artifact.Invoke.Result.Builder).new(0x4000)
+    result.root.id = invoke.root.id
+    @pending_results << result
+
+    if invoke.root.inputs.size != 1 (
+      return @send_error("parse step expects \
+        1 input per invoke, but got \(invoke.root.inputs.size)")
+    )
+
+    input = try (invoke.root.inputs[0]! | return)
+
+    if "\(input.name.kind)" != "trigger-parse" ( // TODO: no string interpolation
+      return @send_error("parse step expects \
+        a trigger-parse artifact as input, but got \(input.name.kind)")
+    )
+
+    source = try (input.name.source! |
+      return @send_error("parse step expects a source-level artifact as input")
+    )
+
+    try (
+      output = result.root.init_outputs(1)[0]!
+      output.name.copy_data_from(input.name)
+      output.name.kind = "parse"
+    |
+      @send_error_bug("Output artifact list was not initialized")
+    )
+
+    path = File.Path.ReadOnly.new(@env.root, "\(source.path)")
+    @log.debug -> ("Loading file from \(path.string)")
+    @file_loader.load_from_file(path, @)
+
+  :is File.Loader.ResultActor
+  :be result_of_load_from_file(
+    path File.Path.Readable
+    result File.Result
+    content Bytes'iso
+  )
+    if result != File.Result.Success (
+      return @send_error("Error loading file from \(path.string): \(result)")
+    )
+    @log.debug -> ("Loaded file from \(path.string)")
+
+    code = (--content).as_string
+    builder = _TreeBuilder.new
+    builder.code = code
+    parser = PEG.Parser(
+      _Token
+      CapnProto.Message.Builder(SaviProto.AST.Document.Builder)
+    ).new(_Grammar.new, builder)
+
+    message = try (
+      parser.parse!(code)
+    |
+      return @send_error("TODO: show grammar error specifics during parsing")
+    )
+
+    if builder.error.has_any (
+      // TODO: show more error specifics
+
+      // builder.error.each -> (info |
+      //   @env.err.print("\(info.code) at \(info.at.start)...\(info.at.end)")
+      // )
+      return @send_error("TODO: show build error specifics during parsing")
+    )
+
+    buffers = try (
+      CapnProto.Segments.Writer.add_header_to_val_buffers!(
+        message.take_val_buffers
+      )
+    |
+      return @send_error_bug("Output artifact data was too large")
+    )
+
+    try (
+      output = @pending_results[0]!.root.outputs[0]!
+      buffers.each -> (b | output.hash = output.hash.bit_xor(b.hash.u64)) // TODO: proper hash64, even on 32-bit platforms
+    |
+      return @send_error_bug("Output artifact data was not initialized")
+    )
+
+    output_path = SaviProto.Artifact.Path.write_to(
+      SaviProto.Artifact.Path.write_root(@env.root)
+      output.as_reader
+    )
+
+    @log.debug -> ("Writing parse results to \(output_path.string)")
+    @file_dumper.dump_to_file(output_path, buffers, @)
+
+  :is File.Dumper.ResultActor
+  :be result_of_dump_to_file(
+    path File.Path.Writable
+    result File.Result
+  )
+    @log.debug -> ("Wrote parse results to \(path.string)")
+    if result != File.Result.Success (
+      return @send_error_bug("Error writing file to \(path.string): \(result)")
     )
 
-    @env.err.print("It took \(nanos.f64 / 1e6) milliseconds...")
+    @send_result
diff --git a/self-hosted/src/savi-lang-plumber/Main.savi b/self-hosted/src/savi-lang-plumber/Main.savi
new file mode 100644
index 00000000..cf31f7bb
--- /dev/null
+++ b/self-hosted/src/savi-lang-plumber/Main.savi
@@ -0,0 +1,80 @@
+:class _CLI
+  :var to_yaml: ""
+
+  :is CLI.Option.Data
+  :fun non define_cli_options(defs CLI.Option.Defs) None
+    defs.string("to-yaml")
+
+  :fun ref trace_data_mutable(trace TraceData.Mutator) None
+    trace.object(identity_digest_of @) -> (key |
+      case key == (
+      | "to-yaml" | trace.replace_string(@to_yaml) -> (v | @to_yaml = v)
+      )
+    )
+
+:actor Main
+  :let env Env
+  :new (@env)
+    cli = try (
+      CLI.Parser(_CLI).parse!(_CLI.new, @env.args)
+    | error |
+      @env.err.print(error.message)
+      @env.exit_code = 1
+      return
+    )
+    log = _Log.new(@env.err, Logger.Level.Debug)
+
+    case (
+    | cli.options.to_yaml != "" |
+      path = File.Path.ReadOnly.new(@env.root, cli.options.to_yaml)
+      ToYAML.new(log, path, @env.out)
+    )
+
+:actor ToYAML
+  :let log _Log
+  :let path File.Path.Readable
+  :let out Env.OutStream
+  :new (@log, @path, @out)
+    File.Loader.new.load_from_file(@path, @)
+
+  :is File.Loader.ResultActor
+  :be result_of_load_from_file(
+    path File.Path.Readable
+    result File.Result
+    content Bytes'iso
+  )
+    if result != File.Result.Success (
+      @log.error -> ("Failed to load file \(path.string): \(result)")
+      return
+    )
+
+    stream = ByteStream.Pair.new
+    stream.write << --content
+    try stream.write.flush!
+
+    reader = CapnProto.Segments.Reader.new
+    try (
+      res = reader.read!(stream.read)
+      if !res (
+        @log.error -> ("Incomplete data at \(path.string)")
+        return
+      )
+    |
+      @log.error -> ("Failed to read the data at \(path.string)")
+      return
+    )
+
+    try (
+      case @path.ext_name == (
+      | "savi-parse" |
+        message = CapnProto.Message(SaviProto.AST.Document)
+          .from_segments!(reader.take_segments)
+        @out.print(Inspect.TraceData.Printer.Deterministic.print(message.root))
+      |
+        @log.error -> ("Unsupported file extension \(path.ext_name)")
+        return
+      )
+    |
+      @log.error -> ("Error reading segments from \(path.string)")
+    )
+