diff --git a/server/test/burble/chat/message_store_test.exs b/server/test/burble/chat/message_store_test.exs
index 93e3a831..f7029f07 100644
--- a/server/test/burble/chat/message_store_test.exs
+++ b/server/test/burble/chat/message_store_test.exs
@@ -14,15 +14,10 @@ defmodule Burble.Chat.MessageStoreTest do
 
   alias Burble.Chat.MessageStore
 
-  # Start a fresh MessageStore for each test so ETS state doesn't bleed.
+  # Shared-app strategy (burble#62): the application owns MessageStore.
+  # Every test uses a unique random room id (room_id/0) so ETS state
+  # cannot bleed between tests without restarting the process.
   setup do
-    # Stop any existing instance (e.g. from Application startup in test env).
-    case Process.whereis(MessageStore) do
-      nil -> :ok
-      pid -> GenServer.stop(pid)
-    end
-
-    {:ok, _pid} = start_supervised!(MessageStore)
     :ok
   end
 
diff --git a/server/test/burble/concurrency/session_concurrency_test.exs b/server/test/burble/concurrency/session_concurrency_test.exs
index 11a1ab7b..ba1c0f52 100644
--- a/server/test/burble/concurrency/session_concurrency_test.exs
+++ b/server/test/burble/concurrency/session_concurrency_test.exs
@@ -35,9 +35,9 @@ defmodule Burble.Concurrency.SessionConcurrencyTest do
 
     # Use start_supervised! so ExUnit owns the lifecycle and restarts these
     # processes between tests, giving each test a clean slate.
-    start_supervised!({Phoenix.PubSub, name: Burble.PubSub})
-    start_supervised!({Registry, keys: :unique, name: Burble.RoomRegistry})
-    start_supervised!({DynamicSupervisor, name: Burble.RoomSupervisor, strategy: :one_for_one})
+    ensure_started({Phoenix.PubSub, name: Burble.PubSub})
+    ensure_started({Registry, keys: :unique, name: Burble.RoomRegistry})
+    ensure_started({DynamicSupervisor, name: Burble.RoomSupervisor, strategy: :one_for_one})
 
     :ok
   end
diff --git a/server/test/burble/e2e/signaling_test.exs b/server/test/burble/e2e/signaling_test.exs
index e922b9f3..445738be 100644
--- a/server/test/burble/e2e/signaling_test.exs
+++ b/server/test/burble/e2e/signaling_test.exs
@@ -45,15 +45,15 @@ defmodule Burble.E2E.SignalingTest do
     Application.ensure_all_started(:phoenix_pubsub)
 
     # start_supervised! ensures ExUnit owns the lifecycle and tears down between tests.
-    start_supervised!({Phoenix.PubSub, name: Burble.PubSub})
-    start_supervised!({Registry, keys: :unique, name: Burble.RoomRegistry})
-    start_supervised!({DynamicSupervisor, name: Burble.RoomSupervisor, strategy: :one_for_one})
+    ensure_started({Phoenix.PubSub, name: Burble.PubSub})
+    ensure_started({Registry, keys: :unique, name: Burble.RoomRegistry})
+    ensure_started({DynamicSupervisor, name: Burble.RoomSupervisor, strategy: :one_for_one})
 
     # Presence tracker — required by RoomChannel.handle_info(:after_join).
-    start_supervised!(Burble.Presence)
+    ensure_started(Burble.Presence)
 
     # Media.Engine — required by RoomChannel.join/3 (add_peer call).
-    start_supervised!(Burble.Media.Engine)
+    ensure_started(Burble.Media.Engine)
 
     # Start Endpoint last — depends on PubSub.
     # BurbleWeb.Endpoint is configured with server: false in test config so
diff --git a/server/test/burble/text/nntps_backend_test.exs b/server/test/burble/text/nntps_backend_test.exs
index 4ddc0027..4bd854e3 100644
--- a/server/test/burble/text/nntps_backend_test.exs
+++ b/server/test/burble/text/nntps_backend_test.exs
@@ -37,11 +37,11 @@ defmodule Burble.Text.NNTPSBackendTest do
   setup do
     # PubSub must be running because post_message broadcasts to "text:<room_id>".
     Application.ensure_all_started(:phoenix_pubsub)
-    start_supervised!({Phoenix.PubSub, name: Burble.PubSub})
+    ensure_started({Phoenix.PubSub, name: Burble.PubSub})
 
     # Start a fresh NNTPSBackend instance.  start_supervised! gives ExUnit
     # ownership so it is torn down (and the name released) after each test.
-    start_supervised!(NNTPSBackend)
+    ensure_started(NNTPSBackend)
 
     :ok
   end
diff --git a/server/test/burble/timing/alignment_test.exs b/server/test/burble/timing/alignment_test.exs
index c5ac1d2c..5950e7eb 100644
--- a/server/test/burble/timing/alignment_test.exs
+++ b/server/test/burble/timing/alignment_test.exs
@@ -20,8 +20,10 @@ defmodule Burble.Timing.AlignmentTest do
       opts
       |> Keyword.put_new(:local_node, :"local@testhost")
       |> Keyword.put_new(:window_ms, 30_000)
+      # start_link/1 forces name: __MODULE__ when :name is absent, colliding
+      # with the application-owned Alignment. Unique-name per test (#62).
+      |> Keyword.put(:name, :"alignment_test_#{System.unique_integer([:positive])}")
 
-    # Do NOT pass :name so tests get an anonymous pid and don't conflict.
     start_supervised!({Alignment, opts})
   end
 
diff --git a/server/test/burble_web/channels/room_channel_text_test.exs b/server/test/burble_web/channels/room_channel_text_test.exs
index 0f2f0863..ef65ab05 100644
--- a/server/test/burble_web/channels/room_channel_text_test.exs
+++ b/server/test/burble_web/channels/room_channel_text_test.exs
@@ -29,20 +29,15 @@ defmodule BurbleWeb.Channels.RoomChannelTextTest do
   setup do
     Application.ensure_all_started(:phoenix_pubsub)
 
-    start_supervised!({Phoenix.PubSub, name: Burble.PubSub})
-    start_supervised!({Registry, keys: :unique, name: Burble.RoomRegistry})
-    start_supervised!({DynamicSupervisor, name: Burble.RoomSupervisor, strategy: :one_for_one})
-    start_supervised!(Burble.Presence)
-    start_supervised!(Burble.Media.Engine)
-    start_supervised!(Burble.Text.NNTPSBackend)
-
-    # MessageStore — stop any existing instance first so we get a clean ETS table.
-    case Process.whereis(Burble.Chat.MessageStore) do
-      nil -> :ok
-      pid -> GenServer.stop(pid)
-    end
-
-    start_supervised!(Burble.Chat.MessageStore)
+    ensure_started({Phoenix.PubSub, name: Burble.PubSub})
+    ensure_started({Registry, keys: :unique, name: Burble.RoomRegistry})
+    ensure_started({DynamicSupervisor, name: Burble.RoomSupervisor, strategy: :one_for_one})
+    ensure_started(Burble.Presence)
+    ensure_started(Burble.Media.Engine)
+    ensure_started(Burble.Text.NNTPSBackend)
+
+    # MessageStore is application-owned; unique room ids isolate (#62).
+    ensure_started(Burble.Chat.MessageStore)
 
     case BurbleWeb.Endpoint.start_link() do
       {:ok, _pid} -> :ok
diff --git a/server/test/support/test_helpers.ex b/server/test/support/test_helpers.ex
index 6f0490da..a959eb82 100644
--- a/server/test/support/test_helpers.ex
+++ b/server/test/support/test_helpers.ex
@@ -54,6 +54,22 @@ defmodule Burble.TestHelpers do
     "user-" <> Base.encode16(:crypto.strong_rand_bytes(4), case: :lower)
   end
 
+  @doc """
+  Start a child spec for the test, or reuse it if the application already
+  owns it (shared-app+reset test strategy, burble#62). Returns `{:ok, pid}`
+  whether freshly started or already running, so setups never crash on
+  `:already_started` for app-owned singletons.
+  """
+  @spec ensure_started(tuple() | module()) :: {:ok, pid()}
+  def ensure_started(spec) do
+    case ExUnit.Callbacks.start_supervised(spec) do
+      {:ok, pid} -> {:ok, pid}
+      {:error, {:already_started, pid}} -> {:ok, pid}
+      {:error, {{:already_started, pid}, _spec}} -> {:ok, pid}
+      {:error, reason} -> raise "ensure_started failed: #{inspect(reason)}"
+    end
+  end
+
   @doc "Build a Plug.Conn for testing API endpoints."
   @spec build_conn(String.t(), String.t(), map()) :: Plug.Conn.t()
   def build_conn(method, path, params \\ %{}) do