diff --git a/v2/ruby/lib/terminalwire/v2/rails.rb b/v2/ruby/lib/terminalwire/v2/rails.rb
index cfd248f..68cacf6 100644
--- a/v2/ruby/lib/terminalwire/v2/rails.rb
+++ b/v2/ruby/lib/terminalwire/v2/rails.rb
@@ -52,6 +52,28 @@ def self.dual_terminal(cli, v1: nil, v2: nil)
         )
       end
 
+      # The v2-DEFAULT endpoint: serve `cli` over v2, with no v1. Mount it the same way
+      # as dual_terminal:
+      #
+      #   match "/terminal", to: Terminalwire::V2::Rails.terminal(MainTerminal),
+      #                      via: [:get, :connect]
+      #
+      # It returns a version endpoint (not the bare Rack): a connection advertising the
+      # `terminalwire.v2` subprotocol — and any connection that doesn't ask for another
+      # version — is served by the v2 server. The endpoint is the forward-compatible
+      # seam: a future v3 registers another handler here without changing the app's
+      # route. (A bare Rack handed to `match to:` drops streaming output in production;
+      # the endpoint, like dual_terminal's, is what Rails routing needs.)
+      def self.terminal(cli, verbose: nil, report: nil)
+        Terminalwire::V2::Server.dualize(cli)
+        v2 = Terminalwire::V2::Server::Rack.new(
+          cli,
+          verbose: verbose.nil? ? verbose?() : verbose,
+          report: report || self.report
+        )
+        VersionEndpoint.new(default: v2, by_subprotocol: { SUBPROTOCOL => v2 })
+      end
+
       # In dev/test, show the full backtrace to the client (consider_all_requests_local,
       # like v1). In production the client sees the generic message — but the real
       # exception is still LOGGED + reported (below), never silently swallowed.
@@ -97,6 +119,23 @@ def call(env)
           (protos.include?(SUBPROTOCOL) ? @v2 : @v1).call(env)
         end
       end
+
+      # Routes a WebSocket upgrade to a handler by the version subprotocol it advertises,
+      # falling back to `default` (v2) when none matches — the forward-compatible seam for
+      # registering future protocol versions. Same Rack-endpoint shape as Dispatcher, so
+      # Rails `match to:` hands the connection off correctly in production.
+      class VersionEndpoint
+        def initialize(default:, by_subprotocol: {})
+          @default = default
+          @by_subprotocol = by_subprotocol
+        end
+
+        def call(env)
+          protos = env["HTTP_SEC_WEBSOCKET_PROTOCOL"].to_s.split(/,\s*/)
+          handler = protos.lazy.filter_map { |proto| @by_subprotocol[proto] }.first || @default
+          handler.call(env)
+        end
+      end
     end
   end
 end
diff --git a/v2/ruby/spec/server/rails_terminal_spec.rb b/v2/ruby/spec/server/rails_terminal_spec.rb
new file mode 100644
index 0000000..11baad7
--- /dev/null
+++ b/v2/ruby/spec/server/rails_terminal_spec.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+require "terminalwire/v2/rails"
+
+RSpec.describe Terminalwire::V2::Rails do
+  describe Terminalwire::V2::Rails::VersionEndpoint do
+    let(:v2) { ->(env) { [:v2, env] } }
+    let(:v3) { ->(env) { [:v3, env] } }
+
+    subject(:endpoint) do
+      described_class.new(default: v2, by_subprotocol: { "terminalwire.v2" => v2, "terminalwire.v3" => v3 })
+    end
+
+    def env(protocols)
+      { "HTTP_SEC_WEBSOCKET_PROTOCOL" => protocols }
+    end
+
+    it "routes an advertised version subprotocol to its handler" do
+      expect(endpoint.call(env("terminalwire.v2")).first).to eq :v2
+      expect(endpoint.call(env("terminalwire.v3")).first).to eq :v3
+    end
+
+    it "defaults (to v2) when no known version is advertised" do
+      expect(endpoint.call(env(nil)).first).to eq :v2
+      expect(endpoint.call(env("")).first).to eq :v2
+      expect(endpoint.call(env("ws, made-up")).first).to eq :v2
+    end
+
+    it "picks the first matching version among several offered" do
+      expect(endpoint.call(env("ws, terminalwire.v3")).first).to eq :v3
+    end
+  end
+
+  describe ".terminal" do
+    let(:cli) { Class.new(Thor) }
+
+    it "returns a v2-default VersionEndpoint" do
+      expect(described_class.terminal(cli)).to be_a(Terminalwire::V2::Rails::VersionEndpoint)
+    end
+
+    it "routes the v2 subprotocol — and anything unversioned — to a Server::Rack" do
+      endpoint = described_class.terminal(cli)
+      rack = endpoint.instance_variable_get(:@default)
+      expect(rack).to be_a(Terminalwire::V2::Server::Rack)
+      # the v2 subprotocol maps to the same Rack as the default
+      expect(endpoint.instance_variable_get(:@by_subprotocol)["terminalwire.v2"]).to be(rack)
+    end
+
+    it "dualizes the cli so it answers the v2 wire" do
+      described_class.terminal(cli)
+      expect(cli.include?(Terminalwire::V2::Server::DualThor)).to be(true)
+    end
+  end
+end