diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3bdbb9a..37c1045 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` now declares `unique_constraint(:id, name: "<table>_pkey")` so `Ecto.ConstraintError` on `audit_logs_pkey` (or custom table pkey) during `log_changes/5` (called from `*_and_log` inside transactions) is turned into a changeset error instead of crashing the caller. The log failure path already swallows errors and returns `{:ok, reason}`. Closes OPS-4624.
+
 ## [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..20a15ae 100644
--- a/lib/ecto_trail/ecto_trail.ex
+++ b/lib/ecto_trail/ecto_trail.ex
@@ -52,6 +52,8 @@ defmodule EctoTrail do
 
   # Cache frequently accessed config to avoid repeated lookups
   @redacted_fields_config Application.compile_env(:ecto_trail, :redacted_fields, nil)
+  @audit_log_table_name Application.compile_env(:ecto_trail, :table_name, "audit_log")
+  @audit_log_pkey_name "#{@audit_log_table_name}_pkey"
   @default_max_params 65_000
   @changelog_fields [:actor_id, :resource, :resource_id, :changeset, :change_type]
   @not_loaded_pattern "Ecto.Association.NotLoaded"
@@ -572,6 +574,8 @@ defmodule EctoTrail do
   defp map_custom_ecto_type(value), do: value
 
   defp changelog_changeset(attrs) do
-    Changeset.cast(%Changelog{}, attrs, @changelog_fields)
+    %Changelog{}
+    |> Changeset.cast(attrs, @changelog_fields)
+    |> Changeset.unique_constraint(:id, name: @audit_log_pkey_name)
   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..ec978d7 100644
--- a/test/unit/ecto_trail_test.exs
+++ b/test/unit/ecto_trail_test.exs
@@ -329,4 +329,23 @@ defmodule EctoTrailTest do
                )
     end
   end
+
+  describe "audit log primary key constraint handling" do
+    test "does not raise Ecto.ConstraintError when audit log pkey is violated; main operation succeeds and log failure is swallowed" do
+      {:ok, _} = TestRepo.insert_and_log(%Resource{name: "seed"}, "actor-seed")
+
+      %Postgrex.Result{rows: [[max_id]]} = TestRepo.query!("SELECT max(id) FROM audit_log")
+      next_id = max_id + 1
+
+      TestRepo.query!(
+        "INSERT INTO audit_log (id, actor_id, resource, resource_id, changeset, change_type, inserted_at) VALUES ($1, 'conflict', 'resources', '999', $2, 'insert', now())",
+        [next_id, %{}]
+      )
+
+      TestRepo.query!("SELECT setval('audit_log_id_seq', $1, false)", [max_id])
+
+      assert {:ok, %Resource{name: "after"}} =
+               TestRepo.insert_and_log(%Resource{name: "after"}, "actor-after")
+    end
+  end
 end