diff --git a/platform/extension/gitworkspace/BUILD.bazel b/platform/extension/gitworkspace/BUILD.bazel
new file mode 100644
index 00000000..c68827bd
--- /dev/null
+++ b/platform/extension/gitworkspace/BUILD.bazel
@@ -0,0 +1,8 @@
+load("@rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["gitworkspace.go"],
+    importpath = "github.com/uber/submitqueue/platform/extension/gitworkspace",
+    visibility = ["//visibility:public"],
+)
diff --git a/platform/extension/gitworkspace/gitworkspace.go b/platform/extension/gitworkspace/gitworkspace.go
new file mode 100644
index 00000000..c9c22dfd
--- /dev/null
+++ b/platform/extension/gitworkspace/gitworkspace.go
@@ -0,0 +1,64 @@
+// Copyright (c) 2026 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 gitworkspace defines the pluggable interface for executing git
+// commands in a stateful workspace. The OSS implementation runs commands as
+// local subprocesses; alternative deployments wrap their backend's exec API
+// in the same contract.
+package gitworkspace
+
+//go:generate mockgen -source=gitworkspace.go -destination=mock/gitworkspace_mock.go -package=mock
+
+import "context"
+
+// Command is one command to execute in a git workspace.
+type Command struct {
+	// Alias identifies this command's Output in the response.
+	Alias string
+	// Bin is the executable name.
+	Bin string
+	// Args are the command-line arguments.
+	Args []string
+	// Stdin is optional standard input.
+	Stdin string
+}
+
+// Output is the result of one executed command.
+type Output struct {
+	// Alias matches the Command that produced this output.
+	Alias string
+	// ExitCode is the process exit code (0 = success, -1 = skipped).
+	ExitCode int32
+	// Stdout is the captured standard output.
+	Stdout string
+	// Stderr is the captured standard error.
+	Stderr string
+}
+
+// Workspace is a stateful git environment where command batches execute
+// sequentially. Commands within one Exec call run in order; a non-zero
+// exit code skips the remaining commands in that batch. State persists
+// across Exec calls on the same Workspace.
+type Workspace interface {
+	// Exec sends a batch of commands and returns their outputs.
+	Exec(commands []Command) ([]Output, error)
+	// Close releases the workspace and its resources.
+	Close() error
+}
+
+// Factory creates Workspace instances bound to a repository.
+type Factory interface {
+	// For returns a Workspace for the given repository.
+	For(ctx context.Context, repo string) (Workspace, error)
+}
diff --git a/platform/extension/gitworkspace/mock/BUILD.bazel b/platform/extension/gitworkspace/mock/BUILD.bazel
new file mode 100644
index 00000000..5d768ea4
--- /dev/null
+++ b/platform/extension/gitworkspace/mock/BUILD.bazel
@@ -0,0 +1,12 @@
+load("@rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["gitworkspace_mock.go"],
+    importpath = "github.com/uber/submitqueue/platform/extension/gitworkspace/mock",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//platform/extension/gitworkspace:go_default_library",
+        "@org_uber_go_mock//gomock:go_default_library",
+    ],
+)
diff --git a/platform/extension/gitworkspace/mock/gitworkspace_mock.go b/platform/extension/gitworkspace/mock/gitworkspace_mock.go
new file mode 100644
index 00000000..c2617943
--- /dev/null
+++ b/platform/extension/gitworkspace/mock/gitworkspace_mock.go
@@ -0,0 +1,103 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: gitworkspace.go
+
+// Package mock is a generated GoMock package.
+package mock
+
+import (
+	context "context"
+	reflect "reflect"
+
+	gitworkspace "github.com/uber/submitqueue/platform/extension/gitworkspace"
+	gomock "go.uber.org/mock/gomock"
+)
+
+// MockWorkspace is a mock of Workspace interface.
+type MockWorkspace struct {
+	ctrl     *gomock.Controller
+	recorder *MockWorkspaceMockRecorder
+}
+
+// MockWorkspaceMockRecorder is the mock recorder for MockWorkspace.
+type MockWorkspaceMockRecorder struct {
+	mock *MockWorkspace
+}
+
+// NewMockWorkspace creates a new mock instance.
+func NewMockWorkspace(ctrl *gomock.Controller) *MockWorkspace {
+	mock := &MockWorkspace{ctrl: ctrl}
+	mock.recorder = &MockWorkspaceMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockWorkspace) EXPECT() *MockWorkspaceMockRecorder {
+	return m.recorder
+}
+
+// Close mocks base method.
+func (m *MockWorkspace) Close() error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Close")
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// Close indicates an expected call of Close.
+func (mr *MockWorkspaceMockRecorder) Close() *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Close", reflect.TypeOf((*MockWorkspace)(nil).Close))
+}
+
+// Exec mocks base method.
+func (m *MockWorkspace) Exec(commands []gitworkspace.Command) ([]gitworkspace.Output, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Exec", commands)
+	ret0, _ := ret[0].([]gitworkspace.Output)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// Exec indicates an expected call of Exec.
+func (mr *MockWorkspaceMockRecorder) Exec(commands interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Exec", reflect.TypeOf((*MockWorkspace)(nil).Exec), commands)
+}
+
+// MockFactory is a mock of Factory interface.
+type MockFactory struct {
+	ctrl     *gomock.Controller
+	recorder *MockFactoryMockRecorder
+}
+
+// MockFactoryMockRecorder is the mock recorder for MockFactory.
+type MockFactoryMockRecorder struct {
+	mock *MockFactory
+}
+
+// NewMockFactory creates a new mock instance.
+func NewMockFactory(ctrl *gomock.Controller) *MockFactory {
+	mock := &MockFactory{ctrl: ctrl}
+	mock.recorder = &MockFactoryMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockFactory) EXPECT() *MockFactoryMockRecorder {
+	return m.recorder
+}
+
+// For mocks base method.
+func (m *MockFactory) For(ctx context.Context, repo string) (gitworkspace.Workspace, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "For", ctx, repo)
+	ret0, _ := ret[0].(gitworkspace.Workspace)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// For indicates an expected call of For.
+func (mr *MockFactoryMockRecorder) For(ctx, repo interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "For", reflect.TypeOf((*MockFactory)(nil).For), ctx, repo)
+}