diff --git a/AGENTS.md b/AGENTS.md
index 4dbcac2..28c0a3a 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -24,6 +24,10 @@ Every owned Ruby file must enable inline RBS with `# rbs_inline: enabled`; annot
 
 Write Minitest files as `test/**/*_test.rb`. Start behavioral changes with a focused failing test. Exercise locking, leases, fencing, and claiming against real database adapters. Synchronize races with queues, barriers, or condition variables instead of arbitrary sleeps. Host-app actor tests should include `SolidObjects::TestHelper` rather than rely on transactional tests.
 
+Watch the test fail before making it pass, and quote the observed failure in the pull request. A test that has never failed has not been shown to test anything, and the ways it can pass while proving nothing are not exotic: a regression test written after the fix, a double that lacks the `ensure` its real collaborator runs, a mock that ignores the signal under test, or a second guard that covers for the one being removed. When a change fixes a defect, revert the fix and confirm the test fails for the expected reason rather than some other one.
+
+Run code in the process and environment it actually runs in. A runtime role gets only what `require "solid_objects"` defines, so verify it through `solid_objects start` rather than in a test process that has already loaded the constant it needs; `test/integration/load_contract_test.rb` enforces that boundary and is the place to record a deliberate exception. Browser modules go through a real browser as well as jsdom. Adapter behavior goes through the real database and every supported client, and because a skipped test looks exactly like a passing one in the summary line, check the skip count when a change touches an adapter.
+
 ## Commit & Pull Request Guidelines
 
 Use concise imperative subjects, preferably under 50 characters; use prefixes such as `fix:`, `ci:`, or `chore:`. Pull requests should explain API, correctness, security, migration, and compatibility effects; list exact validation commands; link issues; and include screenshots for UI or reactive ERB changes. Never bypass hooks or add AI attribution.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 53f4855..4507d11 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,23 @@
 # Changelog
 
+## 0.10.2 - 2026-08-10
+
+- Load the mailbox when the gem is required. `SolidObjects::Mailbox` was
+  reachable only through the caller path, which loads it as a side effect of
+  `SolidObjects.client`. The reminder scheduler and the effect executor enqueue
+  through it directly and run in `solid_objects start`, a process that never
+  calls the client, so both raised
+  `NameError: uninitialized constant SolidObjects::ReminderScheduler::Mailbox`.
+  Reminders never fired and effect result messages never delivered, while the
+  supervisor replaced the dying role over and over. Nothing caught it because
+  every test process has already loaded the constant through some other path.
+- Add a load contract test that asks a fresh process what `require
+  "solid_objects"` actually defines, and fails when a file stops being loaded
+  unless it is listed as deliberately deferred with a reason. This is the class
+  of bug that only appears in the standalone worker.
+- Run a due reminder through a real `solid_objects start` worker in the test
+  suite, rather than only in process.
+
 ## 0.10.1 - 2026-08-10
 
 - Support Trilogy. Adapter selection matched the client name rather than the
diff --git a/Gemfile.lock b/Gemfile.lock
index b261ae2..5905bba 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    solid_objects (0.10.1)
+    solid_objects (0.10.2)
       actioncable (>= 8.0)
       actionpack (>= 8.0)
       actionview (>= 8.0)
@@ -383,7 +383,7 @@ CHECKSUMS
   rubocop-rails-omakase (1.1.0) sha256=2af73ac8ee5852de2919abbd2618af9c15c19b512c4cfc1f9a5d3b6ef009109d
   ruby-progressbar (1.13.0) sha256=80fc9c47a9b640d6834e0dc7b3c94c9df37f08cb072b7761e4a71e22cff29b33
   securerandom (0.4.1) sha256=cc5193d414a4341b6e225f0cb4446aceca8e50d5e1888743fac16987638ea0b1
-  solid_objects (0.10.1)
+  solid_objects (0.10.2)
   sqlite3 (2.9.5-aarch64-linux-gnu) sha256=78075b6337d3d182c6d2b4691049ed45cd220826160c9ea18946bf6a1de200dc
   sqlite3 (2.9.5-aarch64-linux-musl) sha256=18c801185deb4adc01ddb281e8f672a39e3d1729979ca91e39439cd3eac0402d
   sqlite3 (2.9.5-arm-linux-gnu) sha256=1bdfca0c7d63998c60b0f4a8e3c8df2d33800ccc4abd2d612eddbbbc92a4c48b
diff --git a/docs/roadmap.md b/docs/roadmap.md
index a20ad43..ddef3fc 100644
--- a/docs/roadmap.md
+++ b/docs/roadmap.md
@@ -18,7 +18,11 @@
   status, which works on all three adapters; a future version may add narrow
   ready/claimed membership tables for very large outboxes, as messages already
   have
-- One-shot and recurring reminders with `:latest` or `:all` catch-up
+- One-shot and recurring reminders with `:latest` or `:all` catch-up, exercised
+  through a real `solid_objects start` worker as well as in process. They were
+  listed here while broken in that worker: the scheduler reached a constant the
+  caller path happened to load, so reminders never fired in production and
+  every in-process test still passed
 - Durable observable invalidations, scalar Turbo replacement, keyed ERB
   components, signed component locals, and authorized replace or morph refresh
 - Batched component refreshes: components sharing a signed `batch:` collapse to
diff --git a/lib/solid_objects.rb b/lib/solid_objects.rb
index c28a6af..e8c9d85 100644
--- a/lib/solid_objects.rb
+++ b/lib/solid_objects.rb
@@ -55,6 +55,11 @@
 require "solid_objects/commit_action_registry"
 require "solid_objects/lease"
 require "solid_objects/lease_renewer"
+# The reminder scheduler and the effect executor enqueue through the mailbox,
+# and both run in the standalone worker where nothing else has loaded it. It
+# was reachable only through the caller path, so requiring the gem was not
+# enough to run a role that uses it.
+require "solid_objects/mailbox"
 require "solid_objects/worker"
 require "solid_objects/effect_executor"
 require "solid_objects/reminder_scheduler"
diff --git a/lib/solid_objects/version.rb b/lib/solid_objects/version.rb
index a16de9c..54655ff 100644
--- a/lib/solid_objects/version.rb
+++ b/lib/solid_objects/version.rb
@@ -1,5 +1,5 @@
 # rbs_inline: enabled
 
 module SolidObjects
-  VERSION = "0.10.1"
+  VERSION = "0.10.2"
 end
diff --git a/test/dummy/prepare_cli_reminder.rb b/test/dummy/prepare_cli_reminder.rb
new file mode 100644
index 0000000..c8b5625
--- /dev/null
+++ b/test/dummy/prepare_cli_reminder.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+ENV["RAILS_ENV"] = "test"
+
+require_relative "config/environment"
+require_relative "../../db/migrate/20260805000000_create_solid_objects_tables"
+require_relative "../../db/migrate/20260806000000_add_state_revision_to_solid_objects_instances"
+
+CreateSolidObjectsTables.new.migrate(:up)
+AddStateRevisionToSolidObjectsInstances.new.migrate(:up)
+
+# A reminder that is already due, so the scheduler claims and enqueues it on
+# its first pass rather than waiting.
+instance = SolidObjects::Instance.create!(
+  actor_type: "CliWorkerActor",
+  actor_id: "reminder-in-worker",
+  state: {},
+  state_version: 1
+)
+reminder = SolidObjects::Reminder.create!(
+  instance:,
+  actor_type: instance.actor_type,
+  actor_id: instance.actor_id,
+  name: "deliver_push",
+  message_name: "complete",
+  arguments: {},
+  next_run_at: 1.minute.ago,
+  status: "scheduled"
+)
+
+puts reminder.id
diff --git a/test/integration/cli_test.rb b/test/integration/cli_test.rb
index d1a10a2..8650911 100644
--- a/test/integration/cli_test.rb
+++ b/test/integration/cli_test.rb
@@ -44,6 +44,39 @@ class CLITest < ActiveSupport::TestCase
     assert_raises(SolidObjects::Unauthorized) { command.prune_messages }
   end
 
+  # A role that only the standalone worker runs can depend on a constant that
+  # the caller path happens to load first. In this process everything is
+  # already loaded, so the failure is only reachable from a real worker.
+  test "a due reminder fires in the standalone worker" do
+    Dir.mktmpdir("solid-objects-reminder") do |directory|
+      completed = File.join(directory, "completed")
+      environment = worker_environment(directory, completed)
+      dummy_root = File.expand_path("../dummy", __dir__)
+      prepare(environment, dummy_root, "prepare_cli_reminder.rb")
+
+      _input, output, error_output, wait_thread = Open3.popen3(
+        environment,
+        "bundle", "exec", "solid_objects", "start",
+        "--workers", "1",
+        "--reminder-schedulers", "1",
+        "--effect-workers", "0",
+        "--broadcast-workers", "0",
+        chdir: dummy_root
+      )
+      fired = wait_for_file(completed, timeout: 20)
+      # The pipes only reach EOF once the process is gone, so reading them for
+      # the failure message has to wait until after it is stopped.
+      Process.kill("TERM", wait_thread.pid) if wait_thread.alive?
+      wait_thread.join
+      diagnosis = [ output.read, error_output.read ].join("\n")
+
+      assert fired, "the scheduler should have enqueued the due reminder:\n#{diagnosis}"
+    ensure
+      Process.kill("TERM", wait_thread.pid) if wait_thread&.alive?
+      wait_thread&.join
+    end
+  end
+
   # Deny-by-default means an unconfigured host hits this on its first CLI
   # command, so it is the most likely thing a new adopter ever sees.
   test "a denied command reports the policy rather than a backtrace" do
@@ -121,4 +154,35 @@ class CLITest < ActiveSupport::TestCase
       wait_thread&.join
     end
   end
+
+  private
+
+  def worker_environment(directory, probe)
+    {
+      "BUNDLE_GEMFILE" => File.expand_path("../../Gemfile", __dir__),
+      "RAILS_ENV" => "test",
+      "SOLID_OBJECTS_CLI_WORKER_PROBE" => probe,
+      "SOLID_OBJECTS_DUMMY_DATABASE" => File.join(directory, "dummy.sqlite3")
+    }
+  end
+
+  def prepare(environment, dummy_root, script)
+    _output, error_output, status = Open3.capture3(
+      environment,
+      Gem.ruby,
+      File.join(dummy_root, script),
+      chdir: dummy_root
+    )
+    assert status.success?, error_output
+  end
+
+  def wait_for_file(path, timeout:)
+    deadline = Process.clock_gettime(Process::CLOCK_MONOTONIC) + timeout
+    until Process.clock_gettime(Process::CLOCK_MONOTONIC) > deadline
+      return true if File.exist?(path)
+
+      sleep 0.1
+    end
+    false
+  end
 end
diff --git a/test/integration/load_contract_test.rb b/test/integration/load_contract_test.rb
new file mode 100644
index 0000000..5014f1f
--- /dev/null
+++ b/test/integration/load_contract_test.rb
@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "open3"
+
+# Runtime roles run in `solid_objects start`, a process that requires the gem
+# and nothing else. A constant reached only through the caller path resolves
+# fine in this test process, where everything is already loaded, and raises
+# NameError in that worker. Asking a fresh process what `require
+# "solid_objects"` actually defines is the only way to see the difference.
+class LoadContractTest < ActiveSupport::TestCase
+  # Each of these is deliberately not loaded by requiring the gem. Anything
+  # else that stops being loaded is a role waiting to fail in production, so
+  # this list is the place to argue that a role never reaches it.
+  DEFERRED = {
+    "application_actor_loader" => "used only by the CLI",
+    "caller_process" => "the caller path, required by SolidObjects.caller_process",
+    "cli" => "loaded by exe/solid_objects, and pulls in thor",
+    "client" => "the caller path, required by SolidObjects.client",
+    "doctor" => "an operator tool, loaded by the doctor command",
+    "errors" => "defines error classes individually, so no SolidObjects::Errors exists",
+    "sync_diagnostics" => "the caller path, required with the client",
+    "synchronous_invocation" => "the caller path, required with the client",
+    "test_helper" => "opt-in, required by host application tests"
+  }.freeze
+
+  test "requiring the gem defines everything a runtime role reaches for" do
+    assert_equal DEFERRED.keys.sort, undefined_after_require,
+      "a file that stopped being loaded is only safe if no runtime role reaches it"
+  end
+
+  # The reported failure: two roles enqueue through the mailbox, and requiring
+  # the gem did not define it.
+  test "the mailbox is defined by requiring the gem" do
+    refute_includes undefined_after_require, "mailbox",
+      "the reminder scheduler and effect executor enqueue through it"
+  end
+
+  private
+
+  # Computed inside the fresh process, where both the file list and what the
+  # require actually defined are available.
+  def undefined_after_require
+    @undefined_after_require ||= begin
+      output, error_output, status = Open3.capture3(
+        { "BUNDLE_GEMFILE" => gem_root("Gemfile") },
+        Gem.ruby,
+        "-e",
+        probe,
+        chdir: gem_root(".")
+      )
+      assert status.success?, error_output
+      output.split("\n").sort
+    end
+  end
+
+  def probe
+    <<~RUBY
+      require "solid_objects"
+
+      def classify(path)
+        path.split("/").map { |part| part.split("_").map(&:capitalize).join }.join("::")
+      end
+
+      undefined = Dir.glob("**/*.rb", base: "lib/solid_objects").filter_map do |path|
+        file = path.delete_suffix(".rb")
+        next if file == "version"
+
+        begin
+          Object.const_get("SolidObjects::" + classify(file))
+          nil
+        rescue NameError
+          file
+        end
+      end
+      puts undefined
+    RUBY
+  end
+
+  def gem_root(path)
+    File.expand_path("../../#{path}", __dir__)
+  end
+end