diff --git a/stovepipe/core/filter/BUILD.bazel b/stovepipe/core/filter/BUILD.bazel
new file mode 100644
index 00000000..454754b5
--- /dev/null
+++ b/stovepipe/core/filter/BUILD.bazel
@@ -0,0 +1,9 @@
+load("@rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "filter",
+    srcs = ["filter.go"],
+    importpath = "github.com/uber/submitqueue/stovepipe/core/filter",
+    visibility = ["//visibility:public"],
+    deps = ["//stovepipe/entity"],
+)
diff --git a/stovepipe/entity/entity.go b/stovepipe/core/filter/filter.go
similarity index 50%
rename from stovepipe/entity/entity.go
rename to stovepipe/core/filter/filter.go
index 15ac8680..4130bb5a 100644
--- a/stovepipe/entity/entity.go
+++ b/stovepipe/core/filter/filter.go
@@ -12,5 +12,24 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package entity holds Stovepipe-specific domain types (distinct from shared repo entity/).
-package entity
+// Package filter implements a filter for commit events.
+package filter
+
+import (
+	"strings"
+
+	"github.com/uber/submitqueue/stovepipe/entity"
+)
+
+// Config controls which VCS URIs are watched.
+// WatchedURIPrefixes is a list of URI prefixes to match against ChangeEvent.URI.
+// Example: "git://github.com/uber/go-code/refs/heads/main"
+// watches all commits on the main branch of uber/go-code.
+func ShouldProcess(event entity.ChangeEvent, watchedPrefixes []string) bool {
+	for _, prefix := range watchedPrefixes {
+		if strings.HasPrefix(event.URI, prefix) {
+			return true
+		}
+	}
+	return false
+}
diff --git a/stovepipe/entity/BUILD.bazel b/stovepipe/entity/BUILD.bazel
index c179fb43..96707407 100644
--- a/stovepipe/entity/BUILD.bazel
+++ b/stovepipe/entity/BUILD.bazel
@@ -2,7 +2,12 @@ load("@rules_go//go:def.bzl", "go_library")
 
 go_library(
     name = "entity",
-    srcs = ["entity.go"],
+    srcs = [
+        "change_event.go",
+        "change_uri.go",
+        "commit.go",
+    ],
     importpath = "github.com/uber/submitqueue/stovepipe/entity",
     visibility = ["//visibility:public"],
+    deps = ["//stovepipe/entity/git"],
 )
diff --git a/stovepipe/entity/change_event.go b/stovepipe/entity/change_event.go
new file mode 100644
index 00000000..46a664cf
--- /dev/null
+++ b/stovepipe/entity/change_event.go
@@ -0,0 +1,59 @@
+// 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"
+	"fmt"
+
+	entitygit "github.com/uber/submitqueue/stovepipe/entity/git"
+)
+
+// ChangeEvent represents a single new trunk change entering the pipeline, published to the
+// start topic. A trunk change is one commit, so the event carries one git-backed URI. It is
+// source-agnostic: both the webhook and the reconciliation poller emit it. Additional fields
+// (e.g. source, committer time) can be added later as ingestion needs them.
+type ChangeEvent struct {
+	// URI identifies the commit that entered the pipeline (git://owner/repo/branch/revision).
+	URI string `json:"uri"`
+}
+
+// ToBytes serializes the ChangeEvent to JSON bytes for queue message payload.
+func (e ChangeEvent) ToBytes() ([]byte, error) {
+	return json.Marshal(e)
+}
+
+// Validate checks that the change event carries a valid git-backed commit URI.
+func (e ChangeEvent) Validate() error {
+	if e.URI == "" {
+		return fmt.Errorf("change event requires a commit URI")
+	}
+	if _, err := entitygit.ParseChangeID(e.URI); err != nil {
+		return fmt.Errorf("change event URI: %w", err)
+	}
+	return nil
+}
+
+// ChangeEventFromBytes deserializes a ChangeEvent from JSON bytes.
+func ChangeEventFromBytes(data []byte) (ChangeEvent, error) {
+	var event ChangeEvent
+	if err := json.Unmarshal(data, &event); err != nil {
+		return ChangeEvent{}, err
+	}
+	if err := event.Validate(); err != nil {
+		return ChangeEvent{}, err
+	}
+	return event, nil
+}
diff --git a/stovepipe/entity/change_uri.go b/stovepipe/entity/change_uri.go
new file mode 100644
index 00000000..7abc45f3
--- /dev/null
+++ b/stovepipe/entity/change_uri.go
@@ -0,0 +1,36 @@
+// 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"
+
+// ChangeURI is the lightweight reference passed between pipeline stages. It
+// carries only the change identity; stages re-resolve any state they need.
+type ChangeURI struct {
+	// URI is the change identity (git://owner/repo/branch/revision).
+	URI string `json:"uri"`
+}
+
+// ToBytes serializes the ChangeURI to JSON bytes for a queue message payload.
+func (c ChangeURI) ToBytes() ([]byte, error) {
+	return json.Marshal(c)
+}
+
+// ChangeURIFromBytes deserializes a ChangeURI from JSON bytes.
+func ChangeURIFromBytes(data []byte) (ChangeURI, error) {
+	var ref ChangeURI
+	err := json.Unmarshal(data, &ref)
+	return ref, err
+}
diff --git a/stovepipe/entity/commit.go b/stovepipe/entity/commit.go
new file mode 100644
index 00000000..fe734cdb
--- /dev/null
+++ b/stovepipe/entity/commit.go
@@ -0,0 +1,45 @@
+// 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
+
+// CommitStatus is the validation state of a trunk commit as determined by Stovepipe.
+type CommitStatus string
+
+const (
+	// CommitStatusUnknown is the default state when a commit is first ingested.
+	// The commit has landed on main but has not yet been validated.
+	CommitStatusUnknown CommitStatus = ""
+	// CommitStatusSucceeded means the relevant targets build and test successfully at this commit.
+	CommitStatusSucceeded CommitStatus = "succeeded"
+	// CommitStatusFailed means a target is broken at this commit; it is the offending change.
+	CommitStatusFailed CommitStatus = "failed"
+)
+
+// IsCommitStatusTerminal returns true if the status is a final, irreversible state.
+func IsCommitStatusTerminal(s CommitStatus) bool {
+	return s == CommitStatusSucceeded || s == CommitStatusFailed
+}
+
+// Commit is a trunk commit tracked by Stovepipe's gateway.
+type Commit struct {
+	// URI is the canonical change identity from the originating ChangeEvent.
+	URI string
+	// Status is the current validation state of this commit.
+	Status CommitStatus
+	// CreatedAt is the time this commit was first recorded, in milliseconds since epoch.
+	CreatedAt int64
+	// UpdatedAt is the time this commit was last updated, in milliseconds since epoch.
+	UpdatedAt int64
+}
diff --git a/stovepipe/extension/BUILD.bazel b/stovepipe/extension/BUILD.bazel
index bbf4f83b..ac032b39 100644
--- a/stovepipe/extension/BUILD.bazel
+++ b/stovepipe/extension/BUILD.bazel
@@ -5,4 +5,5 @@ go_library(
     srcs = ["extension.go"],
     importpath = "github.com/uber/submitqueue/stovepipe/extension",
     visibility = ["//visibility:public"],
+    deps = ["//stovepipe/entity"],
 )
diff --git a/stovepipe/extension/changeingester/BUILD.bazel b/stovepipe/extension/changeingester/BUILD.bazel
new file mode 100644
index 00000000..4575d4b3
--- /dev/null
+++ b/stovepipe/extension/changeingester/BUILD.bazel
@@ -0,0 +1,13 @@
+load("@rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "changeingester",
+    srcs = ["logging.go"],
+    importpath = "github.com/uber/submitqueue/stovepipe/extension/changeingester",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//stovepipe/entity",
+        "//stovepipe/extension",
+        "@org_uber_go_zap//:zap",
+    ],
+)
diff --git a/stovepipe/extension/changeingester/logging.go b/stovepipe/extension/changeingester/logging.go
new file mode 100644
index 00000000..88e566b1
--- /dev/null
+++ b/stovepipe/extension/changeingester/logging.go
@@ -0,0 +1,43 @@
+// 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 changeingester provides ChangeIngester implementations.
+package changeingester
+
+import (
+	"context"
+
+	"github.com/uber/submitqueue/stovepipe/entity"
+	"github.com/uber/submitqueue/stovepipe/extension"
+	"go.uber.org/zap"
+)
+
+// LoggingHandler is a stub ChangeHandler that logs received changes.
+// Replace with real persistence logic once DB schema is ready.
+type LoggingHandler struct {
+	logger *zap.Logger
+}
+
+// New constructs a new LoggingHandler.
+// The return type enforces interface compliance at compile time.
+func New(logger *zap.Logger) extension.ChangeHandler {
+	return LoggingHandler{logger: logger}
+}
+
+func (h LoggingHandler) IngestChange(ctx context.Context, event entity.ChangeEvent) error {
+	h.logger.Info("ingested change",
+		zap.String("uri", event.URI),
+	)
+	return nil
+}
diff --git a/stovepipe/extension/extension.go b/stovepipe/extension/extension.go
index 92d4bcea..f4de9644 100644
--- a/stovepipe/extension/extension.go
+++ b/stovepipe/extension/extension.go
@@ -14,3 +14,21 @@
 
 // Package extension holds Stovepipe-specific extension implementations.
 package extension
+
+import (
+	"context"
+
+	"github.com/uber/submitqueue/stovepipe/entity"
+)
+
+// ChangeIngester subscribes to change events from a VCS source
+// and dispatches them for processing. The source and VCS are
+// implementation details left to the injected backend.
+type ChangeIngester interface {
+	Start(ctx context.Context) error
+}
+
+// ChangeHandler processes a single change received from the ingester.
+type ChangeHandler interface {
+	IngestChange(ctx context.Context, event entity.ChangeEvent) error
+}