diff --git a/stovepipe/entity/BUILD.bazel b/stovepipe/entity/BUILD.bazel
index 64862273..0884ce1a 100644
--- a/stovepipe/entity/BUILD.bazel
+++ b/stovepipe/entity/BUILD.bazel
@@ -3,6 +3,7 @@ load("@rules_go//go:def.bzl", "go_library", "go_test")
 go_library(
     name = "go_default_library",
     srcs = [
+        "build.go",
         "ingest.go",
         "queue.go",
         "queue_config.go",
@@ -16,6 +17,7 @@ go_library(
 go_test(
     name = "go_default_test",
     srcs = [
+        "build_test.go",
         "request_id_test.go",
         "request_test.go",
     ],
diff --git a/stovepipe/entity/build.go b/stovepipe/entity/build.go
new file mode 100644
index 00000000..4c194bc3
--- /dev/null
+++ b/stovepipe/entity/build.go
@@ -0,0 +1,118 @@
+// Copyright (c) 2025 Uber Technologies, Inc.
+//
+// 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.
+
+package entity
+
+import "encoding/json"
+
+// BuildStatus defines the possible states of a build. Shaped the same as
+// SubmitQueue's own BuildStatus (submitqueue/entity/build.go), but defined
+// locally rather than shared — see build.md's "Alternatives considered for
+// sharing the contract".
+type BuildStatus string
+
+const (
+	// BuildStatusUnknown is the unreachable zero value, set by default when
+	// the structure is initialized. It should never be seen in the system.
+	BuildStatusUnknown BuildStatus = ""
+
+	// BuildStatusAccepted indicates the build has been accepted for
+	// execution by the runner via Trigger, but has not yet started.
+	BuildStatusAccepted BuildStatus = "accepted"
+
+	// BuildStatusRunning indicates the build is currently executing.
+	BuildStatusRunning BuildStatus = "running"
+
+	// BuildStatusSucceeded indicates the build completed successfully.
+	// This is a terminal state.
+	BuildStatusSucceeded BuildStatus = "succeeded"
+
+	// BuildStatusFailed indicates the build did not complete successfully.
+	// This is a terminal state.
+	BuildStatusFailed BuildStatus = "failed"
+
+	// BuildStatusCancelled indicates the build was cancelled.
+	// This is a terminal state.
+	BuildStatusCancelled BuildStatus = "cancelled"
+)
+
+// IsTerminal returns true if the status represents a final state
+// (Succeeded, Failed, or Cancelled). A terminal status is write-once: once
+// buildsignal persists one, a later poll reporting a different terminal
+// value must never overwrite it (see buildsignal.md's Algorithm, step 6).
+func (s BuildStatus) IsTerminal() bool {
+	return s == BuildStatusSucceeded || s == BuildStatusFailed || s == BuildStatusCancelled
+}
+
+// Build represents a single build triggered for a Request's commit. All
+// fields except Status and Version are immutable after creation — build is
+// the sole creator (via BuildStore.Create), and buildsignal is the sole
+// writer of Status/Version afterward.
+type Build struct {
+	// ID is the build's own key: the runner-assigned id returned by
+	// Trigger (e.g. a Buildkite build number). Opaque; never parsed or
+	// derived by stovepipe.
+	ID string `json:"id"`
+	// RequestID is the Request this build validates (Build->Request
+	// navigation; no reverse index from Request to its builds is needed).
+	RequestID string `json:"request_id"`
+	// URI is the head URI being built (== Request.URI).
+	URI string `json:"uri"`
+	// BaseURI is the incremental baseline; empty for full builds.
+	BaseURI string `json:"base_uri"`
+	// Status is the build's lifecycle state.
+	Status BuildStatus `json:"status"`
+	// Version is used for optimistic locking. Versioning starts at 1 and
+	// is incremented for each change to the object.
+	Version int32 `json:"version"`
+}
+
+// ToBytes serializes the Build to JSON bytes for queue message payload.
+func (b Build) ToBytes() ([]byte, error) {
+	return json.Marshal(b)
+}
+
+// BuildFromBytes deserializes a Build from JSON bytes.
+func BuildFromBytes(data []byte) (Build, error) {
+	var build Build
+	err := json.Unmarshal(data, &build)
+	return build, err
+}
+
+// BuildID is a lightweight entity for publishing and consuming just the
+// build identifier via the queue, and for the BuildRunner Status/Cancel
+// parameter. It wraps the one runner-assigned id everywhere it appears.
+type BuildID struct {
+	// ID is the runner-assigned identifier for the build.
+	ID string `json:"id"`
+}
+
+// ToBytes serializes the BuildID to JSON bytes for queue message payload.
+func (b BuildID) ToBytes() ([]byte, error) {
+	return json.Marshal(b)
+}
+
+// BuildIDFromBytes deserializes a BuildID from JSON bytes.
+func BuildIDFromBytes(data []byte) (BuildID, error) {
+	var bid BuildID
+	err := json.Unmarshal(data, &bid)
+	return bid, err
+}
+
+// BuildMetadata carries caller-supplied, provider-echoed free-form metadata
+// about a build. The runner must not depend on its contents. Empty today;
+// expected to carry real data eventually (e.g. conflict-graph info, or other
+// upstream decisions relevant to the build) once a concrete need lands in
+// either domain — the shape is deferred until then, not decided here.
+type BuildMetadata map[string]string
diff --git a/stovepipe/entity/build_test.go b/stovepipe/entity/build_test.go
new file mode 100644
index 00000000..4d94c3b1
--- /dev/null
+++ b/stovepipe/entity/build_test.go
@@ -0,0 +1,127 @@
+// Copyright (c) 2025 Uber Technologies, Inc.
+//
+// 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.
+
+package entity
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestBuildStatus_IsTerminal(t *testing.T) {
+	tests := []struct {
+		name     string
+		status   BuildStatus
+		expected bool
+	}{
+		{name: "succeeded is terminal", status: BuildStatusSucceeded, expected: true},
+		{name: "failed is terminal", status: BuildStatusFailed, expected: true},
+		{name: "cancelled is terminal", status: BuildStatusCancelled, expected: true},
+		{name: "accepted is not terminal", status: BuildStatusAccepted, expected: false},
+		{name: "running is not terminal", status: BuildStatusRunning, expected: false},
+		{name: "unknown is not terminal", status: BuildStatusUnknown, expected: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, tt.status.IsTerminal())
+		})
+	}
+}
+
+func TestBuild_SerializationRoundTrip(t *testing.T) {
+	tests := []struct {
+		name  string
+		build Build
+	}{
+		{
+			name: "accepted incremental build",
+			build: Build{
+				ID:        "bk-1001",
+				RequestID: "request/monorepo/main/42",
+				URI:       "git://remote/monorepo/main/deadbeef",
+				BaseURI:   "git://remote/monorepo/main/cafef00d",
+				Status:    BuildStatusAccepted,
+				Version:   1,
+			},
+		},
+		{
+			name: "succeeded full build with no baseline",
+			build: Build{
+				ID:        "bk-1002",
+				RequestID: "request/monorepo/main/43",
+				URI:       "git://remote/monorepo/main/feedface",
+				Status:    BuildStatusSucceeded,
+				Version:   3,
+			},
+		},
+		{
+			name: "failed build",
+			build: Build{
+				ID:        "bk-1003",
+				RequestID: "request/monorepo/main/44",
+				URI:       "git://remote/monorepo/main/0ff1ce",
+				BaseURI:   "git://remote/monorepo/main/cafef00d",
+				Status:    BuildStatusFailed,
+				Version:   2,
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			data, err := tt.build.ToBytes()
+			require.NoError(t, err)
+
+			deserialized, err := BuildFromBytes(data)
+			require.NoError(t, err)
+
+			assert.Equal(t, tt.build, deserialized)
+		})
+	}
+}
+
+func TestBuildFromBytes_InvalidJSON(t *testing.T) {
+	_, err := BuildFromBytes([]byte(`{"invalid": json"}`))
+	assert.Error(t, err)
+}
+
+func TestBuildFromBytes_EmptyData(t *testing.T) {
+	build, err := BuildFromBytes([]byte(`{}`))
+	require.NoError(t, err)
+
+	assert.Empty(t, build.ID)
+	assert.Empty(t, build.RequestID)
+	assert.Equal(t, BuildStatusUnknown, build.Status)
+	assert.Equal(t, int32(0), build.Version)
+}
+
+func TestBuildID_SerializationRoundTrip(t *testing.T) {
+	original := BuildID{ID: "bk-1001"}
+
+	data, err := original.ToBytes()
+	require.NoError(t, err)
+
+	deserialized, err := BuildIDFromBytes(data)
+	require.NoError(t, err)
+
+	assert.Equal(t, original, deserialized)
+}
+
+func TestBuildIDFromBytes_InvalidJSON(t *testing.T) {
+	_, err := BuildIDFromBytes([]byte(`{"invalid": json"}`))
+	assert.Error(t, err)
+}
diff --git a/stovepipe/entity/request.go b/stovepipe/entity/request.go
index 69b49fb8..817b5250 100644
--- a/stovepipe/entity/request.go
+++ b/stovepipe/entity/request.go
@@ -36,8 +36,21 @@ const (
 	RequestStateProcessing RequestState = "processing"
 	// RequestStateSuperseded means process skipped the request because a newer head exists.
 	RequestStateSuperseded RequestState = "superseded"
+	// RequestStateRecordedGreen means record wrote whole-repo greenness as green for this URI.
+	RequestStateRecordedGreen RequestState = "recorded_green"
+	// RequestStateRecordedNotGreen means record wrote whole-repo greenness as not-green for this
+	// URI — either a genuine build failure, or a conservative verdict forced by the DLQ
+	// reconciler when the request could never complete (see workflow.md's fail-closed posture).
+	RequestStateRecordedNotGreen RequestState = "recorded_not_green"
 )
 
+// IsTerminal returns true if the state is one the pipeline never advances past: superseded (a
+// newer head preempted this request) or either recorded outcome (record wrote greenness for
+// this URI, whether via the normal path or the fail-closed reconciler).
+func (s RequestState) IsTerminal() bool {
+	return s == RequestStateSuperseded || s == RequestStateRecordedGreen || s == RequestStateRecordedNotGreen
+}
+
 // BuildStrategy defines how build validates the request's commit.
 type BuildStrategy string
 
diff --git a/stovepipe/entity/request_test.go b/stovepipe/entity/request_test.go
index 10fa4bd5..e4120d6f 100644
--- a/stovepipe/entity/request_test.go
+++ b/stovepipe/entity/request_test.go
@@ -79,6 +79,27 @@ func TestRequestFromBytes_EmptyData(t *testing.T) {
 	assert.Equal(t, int32(0), req.Version)
 }
 
+func TestRequestState_IsTerminal(t *testing.T) {
+	tests := []struct {
+		name     string
+		state    RequestState
+		expected bool
+	}{
+		{name: "superseded is terminal", state: RequestStateSuperseded, expected: true},
+		{name: "recorded green is terminal", state: RequestStateRecordedGreen, expected: true},
+		{name: "recorded not green is terminal", state: RequestStateRecordedNotGreen, expected: true},
+		{name: "unknown is not terminal", state: RequestStateUnknown, expected: false},
+		{name: "accepted is not terminal", state: RequestStateAccepted, expected: false},
+		{name: "processing is not terminal", state: RequestStateProcessing, expected: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, tt.state.IsTerminal())
+		})
+	}
+}
+
 func TestRequestID_SerializationRoundTrip(t *testing.T) {
 	original := RequestID{ID: "request/monorepo/main/100"}