diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3bdbb9a..876c04a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.0.4] - 2026-06-13
+
+### Fixed
+
+- `changelog_changeset/1` now registers `unique_constraint/3` for the pkey (covers "audit_log_pkey", "audit_logs_pkey", and common naming variants). This turns an `Ecto.ConstraintError` on duplicate pkey inserts (observed during `update_and_log` under concurrent or sequence-reset conditions) into a normal `{:error, changeset}` so callers can handle it. Closes OPS-4629.
+
 ## [1.0.3] - 2026-05-28
 
 ### Fixed
diff --git a/lib/ecto_trail/ecto_trail.ex b/lib/ecto_trail/ecto_trail.ex
index 74d7075..f55973d 100644
--- a/lib/ecto_trail/ecto_trail.ex
+++ b/lib/ecto_trail/ecto_trail.ex
@@ -573,5 +573,7 @@ defmodule EctoTrail do
 
   defp changelog_changeset(attrs) do
     Changeset.cast(%Changelog{}, attrs, @changelog_fields)
+    |> Changeset.unique_constraint(:id, name: "audit_log_pkey")
+    |> Changeset.unique_constraint(:id, name: "audit_logs_pkey")
   end
 end
diff --git a/mix.exs b/mix.exs
index c895a54..e08c811 100644
--- a/mix.exs
+++ b/mix.exs
@@ -1,7 +1,7 @@
 defmodule EctoTrail.Mixfile do
   use Mix.Project
 
-  @version "1.0.3"
+  @version "1.0.4"
 
   def project do
     [
diff --git a/test/unit/ecto_trail_test.exs b/test/unit/ecto_trail_test.exs
index 1a44768..d6e55e3 100644
--- a/test/unit/ecto_trail_test.exs
+++ b/test/unit/ecto_trail_test.exs
@@ -198,6 +198,36 @@ defmodule EctoTrailTest do
       assert [%{name: "name"}] = TestRepo.all(Resource)
       assert [] == TestRepo.all(Changelog)
     end
+
+    test "returns {:error, changeset} with unique_constraint on pkey violation instead of raising Ecto.ConstraintError",
+         %{schema: schema} do
+      # Seed one log entry, then plant a conflicting pkey row and rewind the sequence
+      # so the *next* audit log insert (from update_and_log) collides on the pkey.
+      first_log = TestRepo.one(Changelog)
+      conflict_id = first_log.id
+
+      TestRepo.delete(first_log)
+
+      Ecto.Adapters.SQL.query!(
+        TestRepo,
+        "INSERT INTO \"audit_log\" (id, actor_id, resource, resource_id, changeset, change_type, inserted_at)\n           VALUES ($1, 'seeded','resources','#{schema.id}', '{}'::jsonb, 'insert', now())",
+        [conflict_id]
+      )
+
+      Ecto.Adapters.SQL.query!(
+        TestRepo,
+        "SELECT setval(pg_get_serial_sequence('audit_log', 'id'), $1, false)",
+        [conflict_id]
+      )
+
+      result =
+        schema
+        |> Changeset.change(%{name: "after-conflict"})
+        |> TestRepo.update_and_log("cowboy")
+
+      assert {:error, %Changeset{errors: errors}} = result
+      assert Keyword.has_key?(errors, :id)
+    end
   end
 
   describe "upsert_and_log/3" do