diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 41b2b86..2211171 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -25,9 +25,5 @@ jobs:
         gem install bundler -v 2.4.10
         bundle config set --local path "$GITHUB_WORKSPACE/.bundle/install"
         bundle install
-    - name: Run Integration Tests
-      run: bundle exec rspec spec/tests/integration/write_and_run_osws_spec.rb
-      if: always()
-    - name: Run Unit Tests
-      run: bundle exec rspec spec/tests/unit/buildingsync_reader_spec.rb
-      if: always()
+    - name: Run Tests
+      run: bundle exec rspec
diff --git a/Gemfile.lock b/Gemfile.lock
index 1644caf..1e540f6 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -158,6 +158,11 @@ GEM
       unicode-display_width (>= 2.4.0, < 3.0)
     rubocop-ast (1.30.0)
       parser (>= 3.2.1.0)
+    rubocop-checkstyle_formatter (0.6.0)
+      rubocop (>= 1.14.0)
+    rubocop-performance (1.20.0)
+      rubocop (>= 1.48.1, < 2.0)
+      rubocop-ast (>= 1.30.0, < 2.0)
     ruby-ole (1.2.13.1)
     ruby-progressbar (1.13.0)
     ruby2_keywords (0.0.5)
@@ -191,6 +196,8 @@ DEPENDENCIES
   rake (~> 13.0)
   rspec (~> 3.13)
   rubocop (= 1.50)
+  rubocop-checkstyle_formatter (= 0.6.0)
+  rubocop-performance (= 1.20.0)
 
 BUNDLED WITH
    2.4.10
diff --git a/README.md b/README.md
index cfe7b34..55d94bb 100644
--- a/README.md
+++ b/README.md
@@ -21,6 +21,30 @@ BuildingSync OpenStudio Simulator (BOSS) takes in BuildingSync files, creates Op
     bundle install
     ```
 
+4. Install external non-gem measure repositories declared in the shipped manifest.
+
+    ```bash
+    bundle exec rake measures:install_external
+    ```
+
+5. (Optional) List resolved external measure roots.
+
+    ```bash
+    bundle exec rake measures:list_external
+    ```
+
+The shipped manifest lives at [config/external_measure_repos.yml](config/external_measure_repos.yml) and is preconfigured with:
+
+- local measure roots: `lib/measures` (first in precedence)
+- external repository: comstock (`measures` and `resources/measures`)
+
+Measure path precedence is:
+
+1. local measure roots from [config/external_measure_repos.yml](config/external_measure_repos.yml)
+2. gem-provided measure directories
+3. external non-gem repository measure roots from [config/external_measure_repos.yml](config/external_measure_repos.yml)
+
+The generated `in.osw` will include these paths in order under `measure_paths`.
 
 ## OpenStudio Compatibility Version
 
@@ -97,6 +121,11 @@ bundle exec boss write_baseline_osw BUILDINGSYNC_FILE -o OUTPUT_PATH [options]
 bundle exec boss run_osw BUILDINGSYNC_FILE -o OUTPUT_PATH [options]
 ```
 
+To get help text, type the following:
+```bash
+bundle exec boss help [COMMAND]
+```
+
 ### Options
 
 - `-o`, `--output_path` (required): directory where BOSS writes output (for example, use an XML-specific folder such as `output/v2.7.0/L100_Audit-1.0.0`)
diff --git a/Rakefile b/Rakefile
index 2813932..23985fe 100644
--- a/Rakefile
+++ b/Rakefile
@@ -6,10 +6,37 @@
 
 require 'bundler/gem_tasks'
 require 'rspec/core/rake_task'
+require_relative './lib/BOSS/constants'
+require_relative './lib/BOSS/external_measure_repo_manager'
 
 RSpec::Core::RakeTask.new(:spec)
 
 require 'rubocop/rake_task'
 RuboCop::RakeTask.new
 
-task default: :spec
\ No newline at end of file
+task default: :spec
+
+namespace :measures do
+  desc 'Clone/fetch external non-gem measure repositories declared in config/external_measure_repos.yml'
+  task :install_external do
+    manager = BOSS::ExternalMeasureRepoManager.new
+
+    if !manager.manifest_exists?
+      puts "No external measure manifest found at #{EXTERNAL_MEASURE_REPOS_MANIFEST_PATH}"
+      next
+    end
+
+    dirs = manager.install_all
+    puts "Installed external measure roots (#{dirs.length}):"
+    dirs.each { |dir| puts "  - #{dir}" }
+  end
+
+  desc 'List resolved external non-gem measure directories'
+  task :list_external do
+    manager = BOSS::ExternalMeasureRepoManager.new
+    dirs = manager.resolved_measure_directories
+
+    puts "External measure roots (#{dirs.length}):"
+    dirs.each { |dir| puts "  - #{dir}" }
+  end
+end
\ No newline at end of file
diff --git a/config/external_measure_repos.yml b/config/external_measure_repos.yml
new file mode 100644
index 0000000..212bbcd
--- /dev/null
+++ b/config/external_measure_repos.yml
@@ -0,0 +1,27 @@
+# External non-gem measure repositories.
+#
+# Precedence in workflow measure lookup is:
+# 1) local_measure_roots below
+# 2) gem-provided measure dirs
+# 3) external repos listed here
+#
+# local_measure_roots are resolved relative to this file.
+# The default shipped configuration keeps this repository's local measures first.
+local_measure_roots:
+  - ../lib/measures
+
+# For each repo:
+# - name: local checkout folder name under vendor/external_measures
+# - url: git repository URL
+# - ref: pinned tag/branch/commit to checkout
+# - measure_roots: one or more paths inside the repo that contain measure directories
+#
+
+# The below measures are needed for the BOSS L200 workflow.
+repos:
+  - name: comstock
+    url: https://github.com/NatLabRockies/comstock.git
+    ref: main
+    measure_roots:
+      - measures
+      - resources/measures
diff --git a/lib/BOSS/boss.rb b/lib/BOSS/boss.rb
index ab17f31..71bbe49 100644
--- a/lib/BOSS/boss.rb
+++ b/lib/BOSS/boss.rb
@@ -9,6 +9,7 @@
 require 'fileutils'
 require 'BOSS/buildingsync_reader/buildingsync_reader'
 require 'BOSS/osw_arg_populator'
+require 'BOSS/external_measure_repo_manager'
 
 require 'openstudio/common_measures'
 require 'openstudio/model_articulation'
@@ -56,6 +57,31 @@ def write_baseline_osw
       OSWArgPopulator::populate_set_electric_equipment_loads_by_epd_args(baseline_osw, @bsync_reader)
       OSWArgPopulator::populate_openstudio_results_args(baseline_osw, @bsync_reader)
 
+      # Gather extension-derived paths (typically gem-based measures/files) from ObjectSpace.
+      OpenStudio::Extension.configure_osw(baseline_osw)
+
+      # Force ordering: local BOSS measures, extension-discovered (gems), then external repos.
+      manager = ExternalMeasureRepoManager.new
+      local_measure_dirs = manager.local_measure_directories
+      external_measure_dirs = manager.resolved_measure_directories
+      discovered_measure_dirs = baseline_osw[:measure_paths] || []
+
+      discovered_nonlocal_nonexternal = discovered_measure_dirs.reject do |path|
+        local_measure_dirs.include?(path) || external_measure_dirs.include?(path)
+      end
+
+      baseline_osw[:measure_paths] = ordered_unique(local_measure_dirs + discovered_nonlocal_nonexternal + external_measure_dirs)
+
+      local_file_paths = local_measure_dirs.map { |path| measure_path_to_files_path(path) }
+      external_file_paths = external_measure_dirs.map { |path| measure_path_to_files_path(path) }
+      discovered_file_paths = baseline_osw[:file_paths] || []
+
+      discovered_file_nonlocal_nonexternal = discovered_file_paths.reject do |path|
+        local_file_paths.include?(path) || external_file_paths.include?(path)
+      end
+
+      baseline_osw[:file_paths] = ordered_unique(local_file_paths + discovered_file_nonlocal_nonexternal + external_file_paths)
+
       # write to file
       workflow_dir = File.join(@output_dir, 'baseline')
       FileUtils.mkdir_p(workflow_dir)
@@ -85,5 +111,23 @@ def run_baseline_osw
       # run the baseline osm
       return runner.run_osws([baseline_osw_path])
     end
+
+    private
+
+    def measure_path_to_files_path(measure_path)
+      path = measure_path.to_s
+      replaced = path.sub(%r{/measures/?$}, '/files')
+      return replaced if replaced != path
+
+      File.expand_path(File.join(path, '..', 'files'))
+    end
+
+    def ordered_unique(paths)
+      (paths || []).each_with_object([]) do |path, acc|
+        next if path.nil? || path.empty? || acc.include?(path)
+
+        acc << path
+      end
+    end
   end
 end
diff --git a/lib/BOSS/constants.rb b/lib/BOSS/constants.rb
index 587ca9e..a7a4e81 100644
--- a/lib/BOSS/constants.rb
+++ b/lib/BOSS/constants.rb
@@ -12,9 +12,10 @@
 SCHEMA_2_7_0_URL = 'https://raw.githubusercontent.com/BuildingSync/schema/v2.7.0/BuildingSync.xsd'
 EMPTY_BASELINE_OSW_PATH = File.expand_path(File.join(__dir__, 'empty_baseline.osw'))
 BUILDING_TYPES_BY_OCCUPANCY_CLASSIFICATION_PATH = File.expand_path(File.join(__dir__, 'buildingsync_reader/building_types_by_occupancy_classification.json'))
-
+LOCAL_MEASURES_DIR = File.expand_path(File.join(__dir__, '..', 'measures'))
 WEATHER_DIR = File.expand_path(File.join(__dir__, '../../weather'))
-
+EXTERNAL_MEASURE_REPOS_MANIFEST_PATH = File.expand_path(File.join(__dir__, '..', '..', 'config', 'external_measure_repos.yml'))
+EXTERNAL_MEASURE_REPOS_INSTALL_DIR = File.expand_path(File.join(__dir__, '..', '..', 'vendor', 'external_measures'))
 
 # Standards strings
 ASHRAE90_1 = 'ASHRAE90.1'
diff --git a/lib/BOSS/external_measure_repo_manager.rb b/lib/BOSS/external_measure_repo_manager.rb
new file mode 100644
index 0000000..c4aa967
--- /dev/null
+++ b/lib/BOSS/external_measure_repo_manager.rb
@@ -0,0 +1,168 @@
+# frozen_string_literal: true
+
+# *******************************************************************************
+# OpenStudio(R), Copyright (c) Alliance for Energy Innovation, LLC.
+# See also https://github.com/BuildingSync/BuildingSync-gem/blob/develop/LICENSE.md
+# *******************************************************************************
+
+require 'fileutils'
+require 'open3'
+require 'yaml'
+
+module BOSS
+  # Manages non-gem measure repositories declared in a manifest file.
+  class ExternalMeasureRepoManager
+    def initialize(manifest_path: EXTERNAL_MEASURE_REPOS_MANIFEST_PATH, install_dir: EXTERNAL_MEASURE_REPOS_INSTALL_DIR)
+      @manifest_path = manifest_path
+      @install_dir = install_dir
+    end
+
+    def manifest_exists?
+      File.file?(@manifest_path)
+    end
+
+    def configured?
+      !repo_entries.empty?
+    end
+
+    def local_measure_directories
+      return [LOCAL_MEASURES_DIR] if !manifest_exists?
+
+      roots = manifest['local_measure_roots']
+      roots = [LOCAL_MEASURES_DIR] if !roots.is_a?(Array) || roots.empty?
+
+      directories = roots.map do |path|
+        File.expand_path(path, File.expand_path('..', @manifest_path))
+      end
+
+      directories.select { |path| Dir.exist?(path) }.uniq
+    end
+
+    def install_all
+      return [] if !manifest_exists?
+
+      FileUtils.mkdir_p(@install_dir)
+
+      repo_entries.each do |repo_entry|
+        install_repo(repo_entry)
+      end
+
+      resolved_measure_directories
+    end
+
+    def resolved_measure_directories
+      return [] if !manifest_exists?
+
+      directories = []
+      repo_entries.each do |repo_entry|
+        repo_root = repo_checkout_dir(repo_entry)
+        if !Dir.exist?(repo_root)
+          message = "Repository '#{repo_entry['name']}' is not installed at #{repo_root}. Run rake measures:install_external."
+          if defined?(OpenStudio) && OpenStudio.respond_to?(:logFree)
+            OpenStudio.logFree(OpenStudio::Warn, 'BOSS.ExternalMeasureRepoManager.resolved_measure_directories', message)
+          else
+            warn("BOSS.ExternalMeasureRepoManager.resolved_measure_directories: #{message}")
+          end
+          next
+        end
+
+        repo_entry['measure_roots'].each do |root_rel_path|
+          root_abs_path = File.expand_path(File.join(repo_root, root_rel_path))
+          if Dir.exist?(root_abs_path)
+            directories << root_abs_path
+          else
+            message = "Configured measure root '#{root_rel_path}' does not exist for repository '#{repo_entry['name']}' (#{root_abs_path})."
+            if defined?(OpenStudio) && OpenStudio.respond_to?(:logFree)
+              OpenStudio.logFree(OpenStudio::Warn, 'BOSS.ExternalMeasureRepoManager.resolved_measure_directories', message)
+            else
+              warn("BOSS.ExternalMeasureRepoManager.resolved_measure_directories: #{message}")
+            end
+          end
+        end
+      end
+
+      ordered_unique(directories)
+    end
+
+    private
+
+    def manifest
+      @manifest ||= begin
+        parsed = YAML.safe_load(File.read(@manifest_path), permitted_classes: [], aliases: false)
+        parsed.is_a?(Hash) ? parsed : {}
+      end
+    end
+
+    def repo_entries
+      return [] if !manifest_exists?
+
+      repos = manifest.is_a?(Hash) ? manifest['repos'] : nil
+      return [] if repos.nil?
+      raise StandardError, "Expected 'repos' array in #{@manifest_path}" if !repos.is_a?(Array)
+
+      repos.map do |repo|
+        validate_repo_entry(repo)
+      end
+    end
+
+    def validate_repo_entry(repo)
+      if !repo.is_a?(Hash)
+        raise StandardError, "Each repo entry in #{@manifest_path} must be a map"
+      end
+
+      required = %w[name url ref measure_roots]
+      missing = required.select { |key| repo[key].nil? || repo[key].to_s.empty? }
+      if !missing.empty?
+        raise StandardError, "Repo entry is missing required keys #{missing.join(', ')} in #{@manifest_path}"
+      end
+
+      # Prevent path traversal / unexpected nesting in checkout dir.
+      if !repo['name'].to_s.match?(/\A[\w.-]+\z/)
+        raise StandardError, "Repo name '#{repo['name']}' must match /\\A[\\w.-]+\\z/ in #{@manifest_path}"
+      end
+
+      if !repo['measure_roots'].is_a?(Array) || repo['measure_roots'].empty?
+        raise StandardError, "Repo '#{repo['name']}' must define a non-empty measure_roots array"
+      end
+      repo
+    end
+
+    def install_repo(repo_entry)
+      repo_dir = repo_checkout_dir(repo_entry)
+      measure_roots = repo_entry['measure_roots']
+
+      if Dir.exist?(File.join(repo_dir, '.git'))
+        run_git(%W[-C #{repo_dir} remote set-url origin #{repo_entry['url']}])
+      else
+        FileUtils.mkdir_p(File.dirname(repo_dir))
+        run_git(%W[clone --filter=blob:none --no-checkout #{repo_entry['url']} #{repo_dir}])
+      end
+
+      run_git(%W[-C #{repo_dir} sparse-checkout init --cone])
+      run_git(['-C', repo_dir, 'sparse-checkout', 'set', *measure_roots])
+      run_git(%W[-C #{repo_dir} fetch --depth 1 origin #{repo_entry['ref']}])
+      run_git(%W[-C #{repo_dir} checkout --force FETCH_HEAD])
+    end
+
+    def repo_checkout_dir(repo_entry)
+      File.join(@install_dir, repo_entry['name'])
+    end
+
+    def run_git(args)
+      stdout, stderr, status = Open3.capture3('git', *args)
+      if !status.success?
+        raise StandardError, "git #{args.join(' ')} failed:\n#{stdout}\n#{stderr}"
+      end
+    end
+
+    def ordered_unique(paths)
+      seen = {}
+      paths.each_with_object([]) do |path, acc|
+        next if seen[path]
+
+        seen[path] = true
+        acc << path
+      end
+    end
+  end
+end
diff --git a/lib/boss_cli.rb b/lib/boss_cli.rb
index 1e22dcd..8fd6c4d 100755
--- a/lib/boss_cli.rb
+++ b/lib/boss_cli.rb
@@ -10,7 +10,8 @@
 
 module BOSS
   class CLI < Thor
-    desc "write_baseline_osw BUILDINGSYNC_FILE", "writes a baseline osw using data from the provided Buildingsync file."
+    desc "write_baseline_osw BUILDINGSYNC_FILE", "Writes a baseline osw using data from the provided Buildingsync file."
+    long_desc "Example: $ boss write_baseline_osw my_buildingsync.xml -o ./output_dir -w ./specific_weather_file.epw"
     option :output_path, :required => true, :aliases => "-o", :desc => "path to where the ows gets written. Defaults to '.'"
     option :epw_path, :aliases => "-w", :desc => "path to weather file. If not given, one is derived from the BUILDINGSYNC_FILE."
     option :standard_version, :aliases => "-v", :desc => "building standard to use (eg ASHRAE90.1 or CaliforniaTitle24). Defaults to ASHRAE90.1"
@@ -26,13 +27,15 @@ def write_baseline_osw(buildingsync_file)
       end
     end
 
-    desc "run_osw BUILDINGSYNC_FILE", "runs an existing baseline osw from the output path."
-    option :output_path, :required => true, :aliases => "-o", :desc => "path where the baseline osw exists (expects baseline/in.osw)."
+    desc "run_osw BUILDINGSYNC_FILE", "Runs an existing baseline osw from the output path."
+    long_desc "Example: $ boss run_osw my_buildingsync.xml -o ./output_dir -w ./specific_weather_file.epw"
+    option :output_path, :required => true, :aliases => "-o", :desc => "path where the baseline osw exists (baseline/in.osw will be appended to the path)."
     option :epw_path, :aliases => "-w", :desc => "path to weather file. If not given, one is derived from the BUILDINGSYNC_FILE."
-    option :standard_version, :aliases => "-v", :desc => "building standard to use (eg ASHRAE90.1 or CaliforniaTitle24). Defaults to ASHRAE90.1"
+    # option :standard_version, :aliases => "-v", :desc => "building standard to use (eg ASHRAE90.1 or CaliforniaTitle24). Defaults to ASHRAE90.1"
+    # todo: we don't really need standard_version at this point, but we need to keep it for now to avoid breaking the CLI interface. We can remove it later.
     def run_osw(buildingsync_file)
-      standard_version = options[:standard_version] || ASHRAE90_1
-      boss = BOSS::Boss.new(buildingsync_file, options[:output_path], options[:epw_path], standard_version)
+      #standard_version = options[:standard_version] || ASHRAE90_1
+      boss = BOSS::Boss.new(buildingsync_file, options[:output_path], options[:epw_path], nil)
       boss.run_baseline_osw
     end
   end
diff --git a/lib/measures/.gitkeep b/lib/measures/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/spec/tests/unit/boss_spec.rb b/spec/tests/unit/boss_spec.rb
new file mode 100644
index 0000000..d353103
--- /dev/null
+++ b/spec/tests/unit/boss_spec.rb
@@ -0,0 +1,118 @@
+# *******************************************************************************
+# OpenStudio(R), Copyright (c) Alliance for Energy Innovation, LLC.
+# BuildingSync(R), Copyright (c) Alliance for Energy Innovation, LLC.
+# See also https://github.com/BuildingSync/BOSS/blob/develop/LICENSE.md
+# *******************************************************************************
+
+require 'tmpdir'
+require 'json'
+require 'BOSS/constants'
+require 'BOSS/boss'
+
+BOSS_SPEC_FILES_DIR = File.expand_path('../../files', __dir__)
+
+RSpec.describe BOSS::Boss do
+  # A minimal real XML that Boss.new can parse without errors.
+  let(:xml_path) { File.join(BOSS_SPEC_FILES_DIR, 'v2.7.0', 'building_151.xml') }
+
+  # Placeholder paths that represent the three tiers.
+  let(:gem_measure_dir)      { '/fake/gem/measures' }
+  let(:external_measure_dir) { '/fake/external/measures' }
+
+  before do
+    # Prevent real weather file downloads triggered by BuildingSyncReader.
+    allow(BOSS::BCLWeatherFileDownloader)
+      .to receive(:download_weather_file_from_city_name)
+      .and_return(openstudio_weather_file_path)
+
+    # Stub all OSWArgPopulator class methods so they are no-ops; we only care
+    # about measure_paths ordering, not the steps payload.
+    [
+      :populate_set_run_period_args,
+      :populate_change_building_location_args,
+      :populate_create_bar_from_building_type_ratios_args,
+      :populate_create_typical_building_from_model_args,
+      :populate_set_lighting_loads_by_LPD_args,
+      :populate_set_electric_equipment_loads_by_epd_args,
+      :populate_openstudio_results_args
+    ].each { |m| allow(OSWArgPopulator).to receive(m) }
+  end
+
+  describe '#write_baseline_osw measure_paths ordering' do
+    it 'places local measures first, then gem-provided measures, then external repo measures' do
+      Dir.mktmpdir do |output_dir|
+        boss = described_class.new(xml_path, output_dir, nil, ASHRAE90_1)
+
+        # Simulate OpenStudio::Extension.configure_osw adding gem-provided paths.
+        allow(OpenStudio::Extension).to receive(:configure_osw) do |osw|
+          osw[:measure_paths] = [gem_measure_dir]
+        end
+
+        # Control what ExternalMeasureRepoManager reports.
+        fake_manager = instance_double(BOSS::ExternalMeasureRepoManager)
+        allow(BOSS::ExternalMeasureRepoManager).to receive(:new).and_return(fake_manager)
+        allow(fake_manager).to receive(:local_measure_directories).and_return([LOCAL_MEASURES_DIR])
+        allow(fake_manager).to receive(:resolved_measure_directories).and_return([external_measure_dir])
+
+        osw_path = boss.write_baseline_osw
+
+        osw = JSON.parse(File.read(osw_path), symbolize_names: true)
+        measure_paths = osw[:measure_paths]
+
+        local_idx    = measure_paths.index(LOCAL_MEASURES_DIR)
+        gem_idx      = measure_paths.index(gem_measure_dir)
+        external_idx = measure_paths.index(external_measure_dir)
+
+        expect(local_idx).not_to    be_nil, "local measures dir should appear in measure_paths"
+        expect(gem_idx).not_to      be_nil, "gem measures dir should appear in measure_paths"
+        expect(external_idx).not_to be_nil, "external repo measures dir should appear in measure_paths"
+
+        expect(local_idx).to   be < gem_idx,      "local measures must come before gem measures"
+        expect(gem_idx).to     be < external_idx,  "gem measures must come before external repo measures"
+      end
+    end
+
+    it 'omits external repo dir when no external repos are configured' do
+      Dir.mktmpdir do |output_dir|
+        boss = described_class.new(xml_path, output_dir, nil, ASHRAE90_1)
+
+        allow(OpenStudio::Extension).to receive(:configure_osw) do |osw|
+          osw[:measure_paths] = [gem_measure_dir]
+        end
+
+        fake_manager = instance_double(BOSS::ExternalMeasureRepoManager)
+        allow(BOSS::ExternalMeasureRepoManager).to receive(:new).and_return(fake_manager)
+        allow(fake_manager).to receive(:local_measure_directories).and_return([LOCAL_MEASURES_DIR])
+        allow(fake_manager).to receive(:resolved_measure_directories).and_return([])
+
+        osw_path = boss.write_baseline_osw
+
+        measure_paths = JSON.parse(File.read(osw_path), symbolize_names: true)[:measure_paths]
+        expect(measure_paths).to include(LOCAL_MEASURES_DIR)
+        expect(measure_paths).to include(gem_measure_dir)
+        expect(measure_paths).not_to include(external_measure_dir)
+      end
+    end
+
+    it 'does not duplicate paths that appear in both gem output and local dirs' do
+      Dir.mktmpdir do |output_dir|
+        boss = described_class.new(xml_path, output_dir, nil, ASHRAE90_1)
+
+        # Extension reports the local dir again (can happen with some gem setups).
+        allow(OpenStudio::Extension).to receive(:configure_osw) do |osw|
+          osw[:measure_paths] = [LOCAL_MEASURES_DIR, gem_measure_dir]
+        end
+
+        fake_manager = instance_double(BOSS::ExternalMeasureRepoManager)
+        allow(BOSS::ExternalMeasureRepoManager).to receive(:new).and_return(fake_manager)
+        allow(fake_manager).to receive(:local_measure_directories).and_return([LOCAL_MEASURES_DIR])
+        allow(fake_manager).to receive(:resolved_measure_directories).and_return([external_measure_dir])
+
+        osw_path = boss.write_baseline_osw
+
+        measure_paths = JSON.parse(File.read(osw_path), symbolize_names: true)[:measure_paths]
+        expect(measure_paths.count(LOCAL_MEASURES_DIR)).to eq 1
+      end
+    end
+  end
+end
diff --git a/spec/tests/unit/external_measure_repo_manager_spec.rb b/spec/tests/unit/external_measure_repo_manager_spec.rb
new file mode 100644
index 0000000..035248f
--- /dev/null
+++ b/spec/tests/unit/external_measure_repo_manager_spec.rb
@@ -0,0 +1,312 @@
+# *******************************************************************************
+# OpenStudio(R), Copyright (c) Alliance for Energy Innovation, LLC.
+# BuildingSync(R), Copyright (c) Alliance for Energy Innovation, LLC.
+# See also https://github.com/BuildingSync/BOSS/blob/develop/LICENSE.md
+# *******************************************************************************
+
+require 'tmpdir'
+require 'fileutils'
+require 'BOSS/constants'
+require 'BOSS/external_measure_repo_manager'
+
+RSpec.describe BOSS::ExternalMeasureRepoManager do
+  # Helpers to write a manifest YAML to a temp dir
+  def write_manifest(dir, content)
+    path = File.join(dir, 'external_measure_repos.yml')
+    File.write(path, content)
+    path
+  end
+
+  def manager_for(manifest_path, install_dir)
+    described_class.new(manifest_path: manifest_path, install_dir: install_dir)
+  end
+
+  # ---------------------------------------------------------------------------
+  describe '#manifest_exists?' do
+    it 'returns true when the manifest file is present' do
+      Dir.mktmpdir do |dir|
+        path = write_manifest(dir, "repos: []\n")
+        mgr = manager_for(path, dir)
+        expect(mgr.manifest_exists?).to be true
+      end
+    end
+
+    it 'returns false when the manifest file is absent' do
+      Dir.mktmpdir do |dir|
+        mgr = manager_for(File.join(dir, 'missing.yml'), dir)
+        expect(mgr.manifest_exists?).to be false
+      end
+    end
+  end
+
+  # ---------------------------------------------------------------------------
+  describe '#configured?' do
+    it 'returns false when manifest has no repos' do
+      Dir.mktmpdir do |dir|
+        path = write_manifest(dir, "repos: []\n")
+        expect(manager_for(path, dir).configured?).to be false
+      end
+    end
+
+    it 'returns false when manifest has no repos key' do
+      Dir.mktmpdir do |dir|
+        path = write_manifest(dir, "local_measure_roots:\n  - ./measures\n")
+        expect(manager_for(path, dir).configured?).to be false
+      end
+    end
+
+    it 'returns true when at least one repo is declared' do
+      Dir.mktmpdir do |dir|
+        yaml = <<~YAML
+          repos:
+            - name: my_repo
+              url: https://example.com/repo.git
+              ref: main
+              measure_roots:
+                - measures
+        YAML
+        path = write_manifest(dir, yaml)
+        expect(manager_for(path, dir).configured?).to be true
+      end
+    end
+  end
+
+  # ---------------------------------------------------------------------------
+  describe '#local_measure_directories' do
+    it 'returns the default LOCAL_MEASURES_DIR when no manifest exists' do
+      Dir.mktmpdir do |dir|
+        mgr = manager_for(File.join(dir, 'missing.yml'), dir)
+        expect(mgr.local_measure_directories).to eq [LOCAL_MEASURES_DIR]
+      end
+    end
+
+    it 'expands paths relative to the manifest directory' do
+      Dir.mktmpdir do |dir|
+        # Create a real sub-directory so Dir.exist? passes
+        measures_dir = File.join(dir, 'my_measures')
+        FileUtils.mkdir_p(measures_dir)
+
+        yaml = "local_measure_roots:\n  - my_measures\n"
+        path = write_manifest(dir, yaml)
+
+        result = manager_for(path, dir).local_measure_directories
+        expect(result).to eq [measures_dir]
+      end
+    end
+
+    it 'filters out paths that do not exist' do
+      Dir.mktmpdir do |dir|
+        yaml = "local_measure_roots:\n  - nonexistent_dir\n"
+        path = write_manifest(dir, yaml)
+
+        result = manager_for(path, dir).local_measure_directories
+        expect(result).to be_empty
+      end
+    end
+
+    it 'deduplicates identical paths' do
+      Dir.mktmpdir do |dir|
+        measures_dir = File.join(dir, 'measures')
+        FileUtils.mkdir_p(measures_dir)
+
+        yaml = "local_measure_roots:\n  - measures\n  - measures\n"
+        path = write_manifest(dir, yaml)
+
+        result = manager_for(path, dir).local_measure_directories
+        expect(result).to eq [measures_dir]
+      end
+    end
+
+    it 'falls back to LOCAL_MEASURES_DIR when local_measure_roots is empty' do
+      Dir.mktmpdir do |dir|
+        yaml = "local_measure_roots: []\n"
+        path = write_manifest(dir, yaml)
+
+        result = manager_for(path, dir).local_measure_directories
+        expect(result).to eq [LOCAL_MEASURES_DIR]
+      end
+    end
+  end
+
+  # ---------------------------------------------------------------------------
+  describe '#resolved_measure_directories' do
+    it 'returns empty array when manifest does not exist' do
+      Dir.mktmpdir do |dir|
+        mgr = manager_for(File.join(dir, 'missing.yml'), dir)
+        expect(mgr.resolved_measure_directories).to eq []
+      end
+    end
+
+    it 'returns empty array when repos list is empty' do
+      Dir.mktmpdir do |dir|
+        path = write_manifest(dir, "repos: []\n")
+        expect(manager_for(path, dir).resolved_measure_directories).to eq []
+      end
+    end
+
+    it 'returns existing measure root directories for installed repos' do
+      Dir.mktmpdir do |dir|
+        install_dir = File.join(dir, 'vendor')
+        repo_root   = File.join(install_dir, 'my_repo')
+        mroot       = File.join(repo_root, 'measures')
+        FileUtils.mkdir_p(mroot)
+
+        yaml = <<~YAML
+          repos:
+            - name: my_repo
+              url: https://example.com/repo.git
+              ref: main
+              measure_roots:
+                - measures
+        YAML
+        path = write_manifest(dir, yaml)
+
+        result = manager_for(path, install_dir).resolved_measure_directories
+        expect(result).to eq [mroot]
+      end
+    end
+
+    it 'skips repo if checkout directory does not exist' do
+      Dir.mktmpdir do |dir|
+        install_dir = File.join(dir, 'vendor')
+        FileUtils.mkdir_p(install_dir)
+
+        yaml = <<~YAML
+          repos:
+            - name: missing_repo
+              url: https://example.com/repo.git
+              ref: main
+              measure_roots:
+                - measures
+        YAML
+        path = write_manifest(dir, yaml)
+
+        # Silence the OpenStudio warning — stub module + constant
+        stub_const('OpenStudio', Module.new)
+        stub_const('OpenStudio::Warn', 0)
+        allow(OpenStudio).to receive(:logFree)
+
+        result = manager_for(path, install_dir).resolved_measure_directories
+        expect(result).to eq []
+      end
+    end
+
+    it 'skips a measure_root sub-path that does not exist inside the repo' do
+      Dir.mktmpdir do |dir|
+        install_dir = File.join(dir, 'vendor')
+        repo_root   = File.join(install_dir, 'my_repo')
+        FileUtils.mkdir_p(repo_root) # repo exists but measure sub-dir does not
+
+        yaml = <<~YAML
+          repos:
+            - name: my_repo
+              url: https://example.com/repo.git
+              ref: main
+              measure_roots:
+                - measures
+        YAML
+        path = write_manifest(dir, yaml)
+
+        stub_const('OpenStudio', Module.new)
+        stub_const('OpenStudio::Warn', 0)
+        allow(OpenStudio).to receive(:logFree)
+
+        result = manager_for(path, install_dir).resolved_measure_directories
+        expect(result).to eq []
+      end
+    end
+
+    it 'deduplicates identical resolved paths across repos' do
+      Dir.mktmpdir do |dir|
+        install_dir = File.join(dir, 'vendor')
+        repo_root   = File.join(install_dir, 'repo_a')
+        mroot       = File.join(repo_root, 'measures')
+        FileUtils.mkdir_p(mroot)
+
+        # Two entries pointing at the same resolved path
+        yaml = <<~YAML
+          repos:
+            - name: repo_a
+              url: https://example.com/a.git
+              ref: main
+              measure_roots:
+                - measures
+                - measures
+        YAML
+        path = write_manifest(dir, yaml)
+
+        result = manager_for(path, install_dir).resolved_measure_directories
+        expect(result).to eq [mroot]
+      end
+    end
+
+    it 'returns multiple measure roots from one repo' do
+      Dir.mktmpdir do |dir|
+        install_dir = File.join(dir, 'vendor')
+        repo_root   = File.join(install_dir, 'my_repo')
+        mroot_a     = File.join(repo_root, 'measures')
+        mroot_b     = File.join(repo_root, 'resources', 'measures')
+        FileUtils.mkdir_p(mroot_a)
+        FileUtils.mkdir_p(mroot_b)
+
+        yaml = <<~YAML
+          repos:
+            - name: my_repo
+              url: https://example.com/repo.git
+              ref: main
+              measure_roots:
+                - measures
+                - resources/measures
+        YAML
+        path = write_manifest(dir, yaml)
+
+        result = manager_for(path, install_dir).resolved_measure_directories
+        expect(result).to contain_exactly(mroot_a, mroot_b)
+      end
+    end
+  end
+
+  # ---------------------------------------------------------------------------
+  describe 'manifest validation' do
+    it 'raises when repos key is not an array' do
+      Dir.mktmpdir do |dir|
+        path = write_manifest(dir, "repos: not_an_array\n")
+        expect { manager_for(path, dir).configured? }.to raise_error(StandardError, /Expected 'repos' array/)
+      end
+    end
+
+    it 'raises when a repo entry is missing required keys' do
+      Dir.mktmpdir do |dir|
+        yaml = <<~YAML
+          repos:
+            - name: incomplete_repo
+              url: https://example.com/repo.git
+        YAML
+        path = write_manifest(dir, yaml)
+        expect { manager_for(path, dir).configured? }.to raise_error(StandardError, /missing required keys/)
+      end
+    end
+
+    it 'raises when measure_roots is empty' do
+      Dir.mktmpdir do |dir|
+        yaml = <<~YAML
+          repos:
+            - name: my_repo
+              url: https://example.com/repo.git
+              ref: main
+              measure_roots: []
+        YAML
+        path = write_manifest(dir, yaml)
+        expect { manager_for(path, dir).configured? }.to raise_error(StandardError, /non-empty measure_roots/)
+      end
+    end
+
+    it 'raises when a repo entry is not a hash' do
+      Dir.mktmpdir do |dir|
+        yaml = "repos:\n  - just_a_string\n"
+        path = write_manifest(dir, yaml)
+        expect { manager_for(path, dir).configured? }.to raise_error(StandardError, /must be a map/)
+      end
+    end
+  end
+end