diff --git a/plugins/os-backlog/.claude-plugin/plugin.json b/plugins/os-backlog/.claude-plugin/plugin.json
new file mode 100644
index 0000000..b9f9538
--- /dev/null
+++ b/plugins/os-backlog/.claude-plugin/plugin.json
@@ -0,0 +1,5 @@
+{
+  "name": "os-backlog",
+  "version": "0.1.0",
+  "description": "Uniform Planka backlog boards across projects: idempotent board-ensure (lists, labels, archive convention, Planka 2.1.1 quirk handling) and a deterministic repo-to-board routing resolver."
+}
diff --git a/plugins/os-backlog/bin/os-backlog b/plugins/os-backlog/bin/os-backlog
new file mode 100755
index 0000000..3253c51
--- /dev/null
+++ b/plugins/os-backlog/bin/os-backlog
@@ -0,0 +1,82 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+#
+# os-backlog CLI: board-ensure, activate, archive.
+#
+# Usage:
+#   os-backlog board-ensure NAME --project Dev|Clients
+#   os-backlog activate NAME
+#   os-backlog archive NAME --yes
+#
+# Talks to Planka over the network (the installed planka-api gem,
+# credentials from PLANKA_BASE_URL/USERNAME/PASSWORD).
+#
+# Fails soft: if the gem or Planka credentials are unavailable, prints one
+# clear error and exits nonzero. Never destructive.
+
+require_relative "../lib/backlog"
+
+def fail_soft(message)
+  warn "os-backlog: #{message}"
+  exit 1
+end
+
+def build_client
+  require "planka_api"
+  client = Planka::Client.new
+  client.login
+  client
+rescue LoadError
+  fail_soft("the planka-api gem is not installed/loadable; cannot reach Planka")
+rescue StandardError => e
+  fail_soft("could not authenticate to Planka: #{e.message}")
+end
+
+def parse_project_flag(args)
+  idx = args.index("--project")
+  return "Dev" unless idx
+
+  args.delete_at(idx)
+  project = args.delete_at(idx)
+  project || fail_soft("--project requires a value (Dev or Clients)")
+end
+
+command, *rest = ARGV
+
+case command
+when "board-ensure"
+  name = rest.shift
+  fail_soft("board-ensure requires a board name") unless name
+  project = parse_project_flag(rest)
+  client = build_client
+  result = Backlog::BoardEnsurer.new(client: client).ensure(name, project_name: project)
+  puts "board #{result.board['name']} (#{result.created ? 'created' : 'existing'}) " \
+       "in project #{project}; lists created: #{result.lists_created.join(', ')}; " \
+       "labels created: #{result.labels_created.join(', ')}"
+when "activate"
+  name = rest.shift
+  fail_soft("activate requires a board name") unless name
+  client = build_client
+  board = Backlog::BoardEnsurer.new(client: client).activate(name)
+  puts "activated: #{board['name']}"
+when "archive"
+  name = rest.shift
+  fail_soft("archive requires a board name") unless name
+  fail_soft("archive requires explicit --yes (human go-ahead only)") unless rest.include?("--yes")
+
+  client = build_client
+  board = Backlog::BoardEnsurer.new(client: client).archive(name)
+  puts "archived: #{board['name']}"
+when nil, "-h", "--help"
+  puts <<~USAGE
+    usage: os-backlog <command> [options]
+
+    commands:
+      board-ensure NAME --project Dev|Clients
+      activate NAME
+      archive NAME --yes
+  USAGE
+  exit(command.nil? ? 1 : 0)
+else
+  fail_soft("unknown command #{command.inspect}")
+end
diff --git a/plugins/os-backlog/lib/backlog.rb b/plugins/os-backlog/lib/backlog.rb
new file mode 100644
index 0000000..bfbe912
--- /dev/null
+++ b/plugins/os-backlog/lib/backlog.rb
@@ -0,0 +1,2 @@
+require_relative "backlog/board_spec"
+require_relative "backlog/board_ensurer"
diff --git a/plugins/os-backlog/lib/backlog/board_ensurer.rb b/plugins/os-backlog/lib/backlog/board_ensurer.rb
new file mode 100644
index 0000000..92f3fd8
--- /dev/null
+++ b/plugins/os-backlog/lib/backlog/board_ensurer.rb
@@ -0,0 +1,150 @@
+require_relative "board_spec"
+
+module Backlog
+  # Idempotently creates/repairs a uniform Planka board: the project it
+  # lives under, its lists, and its label set — plus the Planka 2.1.1
+  # quirks the planka-api gem does not handle for us:
+  #
+  #   1. undocumented `type` fields on create (project: "shared" so a
+  #      manager can be added later; list: "active"; the gem already
+  #      requires callers to pass these — it does not default them)
+  #   2. bot-created projects are invisible to the human: a `"private"`
+  #      project auto-assigns its creator as sole ownerProjectManagerId and
+  #      rejects additional managers (422). We create projects as
+  #      `type: "shared"` instead, then explicitly add the human as a
+  #      project manager and null out ownerProjectManagerId.
+  #   3. label colors must come from Planka's (undocumented) color-name
+  #      whitelist — we try an ordered candidate list per label, same
+  #      pattern the planka-api gem uses for its own priority labels.
+  #
+  # This class never archives a board — archiving only happens on explicit
+  # human request (see BoardSpec / the resolver). It does provide the raw
+  # rename primitives (+activate+ / +archive+) that a caller may invoke.
+  class BoardEnsurer
+    Result = Struct.new(:board, :created, :project, :lists_created, :labels_created, keyword_init: true)
+
+    # @param client [Planka::Client] an already-authenticated client
+    # @param human_user_id [String, Integer, nil] Planka user id of the
+    #   human who must be able to see bot-created projects. Falls back to
+    #   +ENV["PLANKA_HUMAN_USER_ID"]+. Only needed when a project doesn't
+    #   already exist.
+    def initialize(client:, human_user_id: nil)
+      @client = client
+      @human_user_id = human_user_id || ENV["PLANKA_HUMAN_USER_ID"]
+    end
+
+    # @param name [String] board name (never an archived---prefixed name;
+    #   this method only ever targets the active board)
+    # @param project_name [String] "Dev" or "Clients" (or any project name)
+    # @return [Result]
+    def ensure(name, project_name:)
+      raise ArgumentError, "board name must not use the archived-- prefix" if BoardSpec.archived?(name)
+
+      project = find_or_create_project(project_name)
+      board, created = find_or_create_board(project, name)
+
+      lists_created = ensure_lists(board)
+      labels_created = ensure_labels(board)
+
+      Result.new(board: board, created: created, project: project,
+                 lists_created: lists_created, labels_created: labels_created)
+    end
+
+    # Rename an archived board back to its active name. Raises if no
+    # archived board by that name exists.
+    #
+    # @param name [String] the active (non-prefixed) name to activate
+    # @return [Hash] the updated board
+    def activate(name)
+      board = find_board_by_name(BoardSpec.archived_name(name))
+      raise "no archived board named #{BoardSpec.archived_name(name).inspect} found" unless board
+
+      @client.boards.update(board["id"], name: name)
+    end
+
+    # Rename an active board to its archived form. Only ever called on
+    # explicit human request — never invoked by +ensure+.
+    #
+    # @param name [String] the active (non-prefixed) name to archive
+    # @return [Hash] the updated board
+    def archive(name)
+      board = find_board_by_name(name)
+      raise "no active board named #{name.inspect} found" unless board
+
+      @client.boards.update(board["id"], name: BoardSpec.archived_name(name))
+    end
+
+    private
+
+    def find_or_create_project(project_name)
+      existing = @client.projects.list.find { |p| p["name"] == project_name }
+      return existing if existing
+
+      project = @client.projects.create(name: project_name, type: "shared")
+      fix_visibility(project)
+      project
+    end
+
+    # Quirk 2: null the bot's sole ownerProjectManagerId and add the human
+    # as a project manager, so the project shows up for them.
+    def fix_visibility(project)
+      return unless @human_user_id
+
+      @client.projects.add_manager(project["id"], @human_user_id)
+      @client.projects.update(project["id"], ownerProjectManagerId: nil)
+    end
+
+    def find_or_create_board(project, name)
+      board = find_board_by_name(name, project: project)
+      return [board, false] if board
+
+      created = @client.boards.create(project["id"], name: name, position: 65_536)
+      [created, true]
+    end
+
+    def find_board_by_name(name, project: nil)
+      projects = project ? [project] : @client.projects.list
+      projects.each do |p|
+        board = @client.boards.list(p["id"]).find { |b| b["name"] == name }
+        return board if board
+      end
+      nil
+    end
+
+    def ensure_lists(board)
+      existing = @client.lists.list(board["id"]).filter_map { |l| l["name"] }
+      created = []
+      BoardSpec::LISTS.each_with_index do |list_name, index|
+        next if existing.include?(list_name)
+
+        @client.lists.create(board["id"], name: list_name, type: "active", position: (index + 1) * 65_536)
+        created << list_name
+      end
+      created
+    end
+
+    def ensure_labels(board)
+      existing = @client.labels.list(board["id"]).filter_map { |l| l["name"] }
+      created = []
+      BoardSpec::LABEL_NAMES.each do |label_name|
+        next if existing.include?(label_name)
+
+        create_label_with_fallback_color(board, label_name)
+        created << label_name
+      end
+      created
+    end
+
+    def create_label_with_fallback_color(board, label_name)
+      candidates = BoardSpec::LABEL_COLOR_CANDIDATES.fetch(label_name)
+      last_error = nil
+      candidates.each do |color|
+        return @client.labels.create(board["id"], name: label_name, color: color, position: 65_536)
+      rescue Planka::ValidationError => e
+        last_error = e
+        next
+      end
+      raise last_error || RuntimeError, "could not create label #{label_name.inspect}: no candidate color accepted"
+    end
+  end
+end
diff --git a/plugins/os-backlog/lib/backlog/board_spec.rb b/plugins/os-backlog/lib/backlog/board_spec.rb
new file mode 100644
index 0000000..c1f5b98
--- /dev/null
+++ b/plugins/os-backlog/lib/backlog/board_spec.rb
@@ -0,0 +1,34 @@
+module Backlog
+  # The uniform board contract every os-backlog board must have: list order
+  # and the enforced label set. Values only — no client/network code.
+  module BoardSpec
+    # Lists in required left-to-right order.
+    LISTS = %w[Backlog Next Doing Waiting Review Done].freeze
+
+    # Label name => ordered candidate colors, tried in turn until the server
+    # accepts one (Planka's palette-name whitelist is not documented, so we
+    # can't assert it in advance — cf. planka-api gem's Priority::COLOR_CANDIDATES
+    # pattern). The first candidate in each list is the verified-good default.
+    LABEL_COLOR_CANDIDATES = {
+      "P0" => %w[berry-red red-burgundy salsa-red],
+      "P1" => %w[pumpkin-orange orange-peel sunset-orange],
+      "P2" => %w[egg-yellow sunny-grass bright-moss],
+      "P3" => %w[steel-grey morning-sky light-cocoa],
+      "hitl" => %w[tank-green bright-moss lagoon-blue],
+      "semi" => %w[lagoon-blue summer-sky navy-blue],
+      "afk-ready" => %w[antique-blue bright-moss slate-blue]
+    }.freeze
+
+    LABEL_NAMES = LABEL_COLOR_CANDIDATES.keys.freeze
+
+    ARCHIVE_PREFIX = "archived--"
+
+    class << self
+      def archived_name(name) = "#{ARCHIVE_PREFIX}#{name}"
+
+      def archived?(name) = name.to_s.start_with?(ARCHIVE_PREFIX)
+
+      def active_name(name) = archived?(name) ? name.sub(ARCHIVE_PREFIX, "") : name
+    end
+  end
+end
diff --git a/plugins/os-backlog/tests/all.rb b/plugins/os-backlog/tests/all.rb
new file mode 100644
index 0000000..8336904
--- /dev/null
+++ b/plugins/os-backlog/tests/all.rb
@@ -0,0 +1,2 @@
+# Run the whole suite: ruby tests/all.rb
+Dir.glob(File.join(__dir__, "*_test.rb")).sort.each { |f| require f }
diff --git a/plugins/os-backlog/tests/board_ensurer_test.rb b/plugins/os-backlog/tests/board_ensurer_test.rb
new file mode 100644
index 0000000..46794f3
--- /dev/null
+++ b/plugins/os-backlog/tests/board_ensurer_test.rb
@@ -0,0 +1,118 @@
+require_relative "test_helper"
+
+class BoardEnsurerTest < Minitest::Test
+  include BacklogTestHelpers
+
+  def test_creates_missing_project_board_lists_and_labels
+    client = FakePlankaClient.new
+    ensurer = Backlog::BoardEnsurer.new(client: client, human_user_id: "human-1")
+
+    result = ensurer.ensure("llf-schema", project_name: "Dev")
+
+    assert result.created
+    assert_equal "llf-schema", result.board["name"]
+    assert_equal Backlog::BoardSpec::LISTS, result.lists_created
+    assert_equal Backlog::BoardSpec::LABEL_NAMES, result.labels_created
+
+    project = client.projects_store.first
+    assert_equal "Dev", project.name
+    assert_equal "shared", project.type
+  end
+
+  def test_rerun_is_a_noop
+    client = FakePlankaClient.new
+    ensurer = Backlog::BoardEnsurer.new(client: client, human_user_id: "human-1")
+    ensurer.ensure("llf-schema", project_name: "Dev")
+
+    result = ensurer.ensure("llf-schema", project_name: "Dev")
+
+    refute result.created
+    assert_empty result.lists_created
+    assert_empty result.labels_created
+    assert_equal 1, client.boards_store.size
+    assert_equal Backlog::BoardSpec::LISTS.size, client.lists_store.size
+    assert_equal Backlog::BoardSpec::LABEL_NAMES.size, client.labels_store.size
+  end
+
+  def test_reuses_existing_project
+    client = FakePlankaClient.new
+    ensurer = Backlog::BoardEnsurer.new(client: client, human_user_id: "human-1")
+    ensurer.ensure("board-a", project_name: "Dev")
+
+    ensurer.ensure("board-b", project_name: "Dev")
+
+    assert_equal 1, client.projects_store.size
+    assert_equal 2, client.boards_store.size
+  end
+
+  def test_applies_owner_manager_visibility_fix_on_new_project
+    client = FakePlankaClient.new
+    ensurer = Backlog::BoardEnsurer.new(client: client, human_user_id: "human-1")
+
+    ensurer.ensure("llf-schema", project_name: "Dev")
+
+    project = client.projects_store.first
+    assert_includes project.managers, "human-1"
+    assert_nil project.ownerProjectManagerId
+  end
+
+  def test_semi_label_is_part_of_enforced_set
+    assert_includes Backlog::BoardSpec::LABEL_NAMES, "semi"
+    assert_includes Backlog::BoardSpec::LABEL_NAMES, "hitl"
+    assert_includes Backlog::BoardSpec::LABEL_NAMES, "afk-ready"
+  end
+
+  def test_label_color_falls_back_to_next_candidate_on_rejection
+    first_choice = Backlog::BoardSpec::LABEL_COLOR_CANDIDATES.fetch("P0").first
+    client = FakePlankaClient.new(reject_colors: [first_choice])
+    ensurer = Backlog::BoardEnsurer.new(client: client, human_user_id: "human-1")
+
+    ensurer.ensure("llf-schema", project_name: "Dev")
+
+    p0 = client.labels_store.find { |l| l.name == "P0" }
+    refute_equal first_choice, p0.color
+  end
+
+  def test_activate_renames_archived_board_back
+    client = FakePlankaClient.new
+    ensurer = Backlog::BoardEnsurer.new(client: client, human_user_id: "human-1")
+    ensurer.ensure("llf-schema", project_name: "Dev")
+    board = client.boards_store.first
+    board.name = "archived--llf-schema"
+
+    result = ensurer.activate("llf-schema")
+
+    assert_equal "llf-schema", result["name"]
+  end
+
+  def test_archive_renames_active_board
+    client = FakePlankaClient.new
+    ensurer = Backlog::BoardEnsurer.new(client: client, human_user_id: "human-1")
+    ensurer.ensure("llf-schema", project_name: "Dev")
+
+    result = ensurer.archive("llf-schema")
+
+    assert_equal "archived--llf-schema", result["name"]
+  end
+
+  def test_ensure_never_touches_archived_boards
+    client = FakePlankaClient.new
+    ensurer = Backlog::BoardEnsurer.new(client: client, human_user_id: "human-1")
+    ensurer.ensure("llf-schema", project_name: "Dev")
+    ensurer.archive("llf-schema")
+
+    result = ensurer.ensure("llf-schema", project_name: "Dev")
+
+    assert result.created
+    assert_equal 2, client.boards_store.size
+    archived = client.boards_store.find { |b| b.name == "archived--llf-schema" }
+    refute_nil archived
+  end
+
+  def test_ensure_rejects_archived_prefixed_name
+    client = FakePlankaClient.new
+    ensurer = Backlog::BoardEnsurer.new(client: client, human_user_id: "human-1")
+
+    assert_raises(ArgumentError) { ensurer.ensure("archived--x", project_name: "Dev") }
+  end
+end
diff --git a/plugins/os-backlog/tests/test_helper.rb b/plugins/os-backlog/tests/test_helper.rb
new file mode 100644
index 0000000..b4ae1bc
--- /dev/null
+++ b/plugins/os-backlog/tests/test_helper.rb
@@ -0,0 +1,139 @@
+require "minitest/autorun"
+require_relative "../lib/backlog"
+
+# Minimal stand-ins for the planka-api gem's error hierarchy, so tests never
+# require (or need) the real gem installed — only the shape our code
+# rescues against.
+module Planka
+  class Error < StandardError; end
+  class ValidationError < Error; end
+end
+
+module BacklogTestHelpers
+  # A hand-rolled fake of the subset of Planka::Client's resource surface
+  # BoardEnsurer touches: projects, boards, lists, labels. In-memory only,
+  # no network. Mirrors the gem's real return shapes (string-keyed hashes).
+  class FakePlankaClient
+    Project = Struct.new(:id, :name, :type, :ownerProjectManagerId, :managers, keyword_init: true)
+    Board = Struct.new(:id, :project_id, :name, keyword_init: true)
+    List = Struct.new(:id, :board_id, :name, :type, keyword_init: true)
+    Label = Struct.new(:id, :board_id, :name, :color, keyword_init: true)
+
+    attr_reader :projects, :boards, :lists, :labels
+
+    def initialize(reject_colors: [])
+      @next_id = 0
+      @projects_store = []
+      @boards_store = []
+      @lists_store = []
+      @labels_store = []
+
+      @projects = ProjectsResource.new(self)
+      @boards = BoardsResource.new(self)
+      @lists = ListsResource.new(self)
+      @labels = LabelsResource.new(self, reject_colors: reject_colors)
+    end
+
+    def next_id = (@next_id += 1).to_s
+
+    attr_reader :projects_store, :boards_store, :lists_store, :labels_store
+
+    class ProjectsResource
+      def initialize(client) = @client = client
+
+      def list = @client.projects_store.map { |p| stringify(p) }
+
+      def create(attrs)
+        project = FakePlankaClient::Project.new(
+          id: @client.next_id, name: attrs[:name], type: attrs[:type],
+          ownerProjectManagerId: @client.next_id, managers: []
+        )
+        @client.projects_store << project
+        stringify(project)
+      end
+
+      def update(id, attrs)
+        project = @client.projects_store.find { |p| p.id == id }
+        project.ownerProjectManagerId = attrs[:ownerProjectManagerId] if attrs.key?(:ownerProjectManagerId)
+        stringify(project)
+      end
+
+      def add_manager(project_id, user_id)
+        project = @client.projects_store.find { |p| p.id == project_id }
+        project.managers << user_id
+        { "id" => @client.next_id, "projectId" => project_id, "userId" => user_id }
+      end
+
+      private
+
+      def stringify(p) = { "id" => p.id, "name" => p.name, "type" => p.type }
+    end
+
+    class BoardsResource
+      def initialize(client) = @client = client
+
+      def list(project_id)
+        @client.boards_store.select { |b| b.project_id == project_id }.map { |b| stringify(b) }
+      end
+
+      def create(project_id, attrs)
+        board = FakePlankaClient::Board.new(id: @client.next_id, project_id: project_id, name: attrs[:name])
+        @client.boards_store << board
+        stringify(board)
+      end
+
+      def update(id, attrs)
+        board = @client.boards_store.find { |b| b.id == id }
+        board.name = attrs[:name] if attrs.key?(:name)
+        stringify(board)
+      end
+
+      private
+
+      def stringify(b) = { "id" => b.id, "projectId" => b.project_id, "name" => b.name }
+    end
+
+    class ListsResource
+      def initialize(client) = @client = client
+
+      def list(board_id)
+        @client.lists_store.select { |l| l.board_id == board_id }.map { |l| stringify(l) }
+      end
+
+      def create(board_id, attrs)
+        raise ArgumentError, "list create requires type" unless attrs[:type]
+
+        list = FakePlankaClient::List.new(id: @client.next_id, board_id: board_id, name: attrs[:name], type: attrs[:type])
+        @client.lists_store << list
+        stringify(list)
+      end
+
+      private
+
+      def stringify(l) = { "id" => l.id, "boardId" => l.board_id, "name" => l.name, "type" => l.type }
+    end
+
+    class LabelsResource
+      def initialize(client, reject_colors: [])
+        @client = client
+        @reject_colors = reject_colors
+      end
+
+      def list(board_id)
+        @client.labels_store.select { |l| l.board_id == board_id }.map { |l| stringify(l) }
+      end
+
+      def create(board_id, attrs)
+        raise Planka::ValidationError, "color #{attrs[:color]} rejected" if @reject_colors.include?(attrs[:color])
+
+        label = FakePlankaClient::Label.new(id: @client.next_id, board_id: board_id, name: attrs[:name], color: attrs[:color])
+        @client.labels_store << label
+        stringify(label)
+      end
+
+      private
+
+      def stringify(l) = { "id" => l.id, "boardId" => l.board_id, "name" => l.name, "color" => l.color }
+    end
+  end
+end