Run Rails builds as standalone commands

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## 0.1.0.alpha.6 - 2026-08-28
+
+- Run `bin/rails boring:build` as a standalone builder process so Dagger can
+  preserve the command, streaming progress, signals, and cleanup.
+
 ## 0.1.0.alpha.5 - 2026-08-28
 
 - Record the exact local or BoringCache build result for deployment tools.

lib/boringbuilder/tasks/boring.rake

@@ -29,8 +29,7 @@ namespace :boring do
     end
 
     command << Rails.root.to_s
-    status = BoringBuilder::CLI.start(command)
-    raise BoringBuilder::BuildError, "BoringBuilder exited unsuccessfully" unless status.zero?
+    Kernel.exec(Gem.ruby, Gem.bin_path("boringbuilder", "boringbuilder"), *command)
   end
 
   desc "Check the configured container runtime"

lib/boringbuilder/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module BoringBuilder
-  VERSION = "0.1.0.alpha.5"
+  VERSION = "0.1.0.alpha.6"
 end

test/boringbuilder/rake_task_test.rb

@@ -24,35 +24,33 @@ def test_exposes_the_rails_shaped_build_task
 
   def test_builds_the_rails_application
     calls = []
-    start = lambda do |arguments|
-      calls << arguments
-      0
-    end
+    executable = Gem.bin_path("boringbuilder", "boringbuilder")
 
     with_environment("BORINGBUILDER_RUNTIME" => "docker", "BORINGBUILDER_OUTPUT" => "dist/app.tar.zst") do
       with_rails_root do
-        with_cli_start(start) do
+        with_kernel_exec(->(*arguments) { calls << arguments }) do
           Rake::Task["boring:build"].invoke
         end
       end
     end
 
     assert_equal [
-      ["build", "--runtime", "docker", "--output", "dist/app.tar.zst", Pathname.pwd.to_s]
+      [Gem.ruby, executable, "build", "--runtime", "docker", "--output", "dist/app.tar.zst",
+       Pathname.pwd.to_s]
     ], calls
   end
 
   private
 
-  def with_cli_start(replacement)
-    singleton_class = BoringBuilder::CLI.singleton_class
-    original = BoringBuilder::CLI.method(:start)
-    singleton_class.send(:remove_method, :start)
-    singleton_class.define_method(:start, replacement)
+  def with_kernel_exec(replacement)
+    singleton_class = Kernel.singleton_class
+    original = Kernel.method(:exec)
+    singleton_class.send(:remove_method, :exec)
+    singleton_class.define_method(:exec, replacement)
     yield
   ensure
-    singleton_class.send(:remove_method, :start)
-    singleton_class.define_method(:start, original)
+    singleton_class.send(:remove_method, :exec)
+    singleton_class.define_method(:exec, original)
   end
 
   def with_environment(values)