From 4c88770353a582c49237902e70fee2140f6dbaf6 Mon Sep 17 00:00:00 2001
From: Marko Vejnovic <marko@atuin.sh>
Date: Wed, 7 Oct 2026 15:48:31 -0700
Subject: [PATCH 1/3] test: make sender_test.exs exercise sender supervision

---
 test/posthog/sender_test.exs | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/test/posthog/sender_test.exs b/test/posthog/sender_test.exs
index 94c7b18..0eadbce 100644
--- a/test/posthog/sender_test.exs
+++ b/test/posthog/sender_test.exs
@@ -188,15 +188,14 @@ defmodule PostHog.SenderTest do
     end
 
     test "sends leftovers on shutdown", %{api_client: api_client} do
-      pid =
-        start_supervised!(
-          {Sender,
-           supervisor_name: @supervisor_name,
-           index: 1,
-           api_client: api_client,
-           max_batch_time_ms: 60_000,
-           max_batch_events: 100}
-        )
+      start_supervised!(
+        {Sender,
+         supervisor_name: @supervisor_name,
+         index: 1,
+         api_client: api_client,
+         max_batch_time_ms: 60_000,
+         max_batch_events: 100}
+      )
 
       expect(API.Mock, :request, fn _client, method, url, opts ->
         assert method == :post
@@ -209,7 +208,7 @@ defmodule PostHog.SenderTest do
 
       Sender.send("foo", @supervisor_name)
 
-      assert :ok = GenServer.stop(pid)
+      assert :ok = stop_supervised(Sender)
     end
 
     test "does not send empty batch", %{api_client: api_client, registry: registry} do

From ee6600749c8f5616a7a851a08f66be02791f061d Mon Sep 17 00:00:00 2001
From: Marko Vejnovic <marko@atuin.sh>
Date: Wed, 7 Oct 2026 15:49:48 -0700
Subject: [PATCH 2/3] fix: correctly trap exits in Sender

---
 lib/posthog/sender.ex | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/posthog/sender.ex b/lib/posthog/sender.ex
index 0970fa3..e914d1a 100644
--- a/lib/posthog/sender.ex
+++ b/lib/posthog/sender.ex
@@ -20,7 +20,6 @@ defmodule PostHog.Sender do
       |> PostHog.Registry.via(__MODULE__, opts[:index])
 
     callers = Process.get(:"$callers", [])
-    Process.flag(:trap_exit, true)
 
     GenServer.start_link(__MODULE__, {opts, callers}, name: name)
   end
@@ -70,6 +69,8 @@ defmodule PostHog.Sender do
 
   @impl GenServer
   def init({opts, callers}) do
+    Process.flag(:trap_exit, true)
+
     state = %__MODULE__{
       registry: PostHog.Registry.registry_name(opts[:supervisor_name]),
       index: Keyword.fetch!(opts, :index),

From f4ef911e4d80dd1386a01ae9c7a86f9d9df16437 Mon Sep 17 00:00:00 2001
From: Marko Vejnovic <marko@atuin.sh>
Date: Wed, 7 Oct 2026 18:10:50 -0700
Subject: [PATCH 3/3] chore: add sampo changeset

---
 .sampo/changesets/flush-on-process-exit.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .sampo/changesets/flush-on-process-exit.md

diff --git a/.sampo/changesets/flush-on-process-exit.md b/.sampo/changesets/flush-on-process-exit.md
new file mode 100644
index 0000000..add6a65
--- /dev/null
+++ b/.sampo/changesets/flush-on-process-exit.md
@@ -0,0 +1,5 @@
+---
+hex/posthog: patch
+---
+
+Fix `PostHog.Sender` not flushing all events on app termination.