diff --git a/plugins/os-backlog/bin/os-backlog b/plugins/os-backlog/bin/os-backlog
index cc975d2..6b5f8e3 100755
--- a/plugins/os-backlog/bin/os-backlog
+++ b/plugins/os-backlog/bin/os-backlog
@@ -40,6 +40,18 @@ def fail_soft(message)
   exit 1
 end
 
+# Guards board-ensure/activate/archive's positional NAME argument against a
+# mistaken flag-style invocation (e.g. `board-ensure --board apprise-api`,
+# where `--board` is swallowed as the name and `apprise-api` is dropped
+# silently). Called immediately after each command shifts its name arg,
+# before build_client, so a bad name never reaches Planka.
+def validate_board_name!(name, command)
+  return unless name.start_with?("--")
+
+  fail_soft("#{command}: board name #{name.inspect} must not start with \"--\" " \
+             "(looks like a flag was passed positionally — check your quoting/flags)")
+end
+
 def build_client
   require "planka_api"
   client = Planka::Client.new
@@ -190,6 +202,7 @@ case command
 when "board-ensure"
   name = rest.shift
   fail_soft("board-ensure requires a board name") unless name
+  validate_board_name!(name, "board-ensure")
   project = parse_project_flag(rest)
   client = build_client
   result = Backlog::BoardEnsurer.new(client: client).ensure(name, project_name: project)
@@ -199,12 +212,14 @@ when "board-ensure"
 when "activate"
   name = rest.shift
   fail_soft("activate requires a board name") unless name
+  validate_board_name!(name, "activate")
   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
+  validate_board_name!(name, "archive")
   fail_soft("archive requires explicit --yes (human go-ahead only)") unless rest.include?("--yes")
 
   client = build_client
diff --git a/plugins/os-backlog/tests/board_name_validation_test.rb b/plugins/os-backlog/tests/board_name_validation_test.rb
new file mode 100644
index 0000000..4ab051a
--- /dev/null
+++ b/plugins/os-backlog/tests/board_name_validation_test.rb
@@ -0,0 +1,50 @@
+require_relative "test_helper"
+
+# Card #1818501985909868001: a mistaken flag-style invocation like
+# `os-backlog board-ensure --board apprise-api` must fail loudly with a
+# usage error instead of silently creating a Planka board literally named
+# "--board". These are CLI-contract tests (shell out to bin/os-backlog)
+# because the bug is about what the positional NAME arg parsing accepts
+# BEFORE any Planka client/network call is made — no PLANKA_* env vars are
+# set, so if validation didn't happen first, these would instead fail on
+# network auth with a different message.
+class BoardNameValidationCliTest < Minitest::Test
+  BIN = File.expand_path("../bin/os-backlog", __dir__)
+
+  # Strip any live Planka credentials from the child's env: these tests
+  # assert that flag-like names are rejected BEFORE build_client ever runs,
+  # so no test here may be allowed to reach the network even accidentally.
+  def run_cli(*args)
+    env = { "PLANKA_BASE_URL" => "", "PLANKA_USERNAME" => "", "PLANKA_PASSWORD" => "" }
+    out = IO.popen(env, [RbConfig.ruby, BIN, *args], err: [:child, :out], &:read)
+    [out, $?.exitstatus]
+  end
+
+  def test_board_ensure_rejects_flag_like_name
+    out, status = run_cli("board-ensure", "--board", "apprise-api")
+
+    refute_equal 0, status
+    assert_match(/board name.*must not start with/i, out)
+  end
+
+  def test_activate_rejects_flag_like_name
+    out, status = run_cli("activate", "--board")
+
+    refute_equal 0, status
+    assert_match(/board name.*must not start with/i, out)
+  end
+
+  def test_archive_rejects_flag_like_name
+    out, status = run_cli("archive", "--board", "--yes")
+
+    refute_equal 0, status
+    assert_match(/board name.*must not start with/i, out)
+  end
+
+  def test_board_ensure_accepts_normal_name_and_fails_later_on_network
+    out, status = run_cli("board-ensure", "apprise-api")
+
+    refute_equal 0, status
+    refute_match(/board name.*must not start with/i, out)
+  end
+end