diff --git a/CHANGELOG.md b/CHANGELOG.md
index ba4e05f..8b2a57d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -30,6 +30,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **Column-header tooltips clipped** – Tooltips on the members-overview column headers are no longer clipped by the sticky table header.
 - **Text selection opens member** – Dragging to select text in a members-overview row (for example to copy an email) no longer opens the member details; a plain click still opens them.
 - **Sort by custom date** – Sorting the member list or member export by a custom date field now orders rows chronologically instead of like text, so e.g. 29.01.1981 correctly comes before 01.03.1982.
+- **Concurrent member creation no longer deadlocks** – Creating members in parallel (e.g. simultaneous sign-ups, or batch operations) could intermittently fail with a PostgreSQL deadlock; the affected foreign keys are now deferrable, so concurrent member creation succeeds reliably.
 
 ## [1.2.0] - 2026-05-08
 
diff --git a/docs/test-performance-optimization.md b/docs/test-performance-optimization.md
index b45c9fc..0a243c3 100644
--- a/docs/test-performance-optimization.md
+++ b/docs/test-performance-optimization.md
@@ -90,6 +90,29 @@ test/
 
 ---
 
+## 5. Concurrent `create_member` deadlock and deferrable FKs
+
+A class of intermittent failures (PostgreSQL `deadlock_detected`, SQLSTATE `40P01`) was traced to **concurrent `create_member` transactions**, not to any single test. It surfaced as a `MatchError` on `{:ok, member} = ...` in member-heavy LiveView tests (e.g. `FormMemberSelectionTest`) and reproduced only under CPU contention (≈1 in 12 full-fast-suite runs at high `async: true` concurrency; effectively never on an idle machine).
+
+**Root cause.** `create_member` writes a cascade in one transaction (member row, `custom_field_values`, the `user` link, fee-type defaulting, cycle generation). Concurrent inserts take FK `FOR KEY SHARE` (MultiXact) locks on shared parent rows across `members` / `users` / `membership_fee_types`; under contention these can form a cross-transaction lock cycle that Postgres resolves by aborting one transaction. It is a product-level concurrency property, **not** test-data contention, so it is not fixable by test-state isolation.
+
+**Fix.** Migration `…_make_member_user_fks_deferrable.exs` makes the three FKs (`users.member_id`, `users.role_id`, `members.membership_fee_type_id`) `DEFERRABLE INITIALLY DEFERRED`, moving the FK check (and its lock) to commit time and breaking the cycle. Verified: **0 deadlocks in 15 full-suite runs under maximum CPU contention**, versus 1/12 before. This does **not** weaken integrity — `NOT NULL` is independent of FK deferral, a real dangling reference still aborts the commit, and `ON DELETE RESTRICT` (e.g. `users.role_id`) stays immediate regardless of deferrability. `Mv.DeferrableFkTest` asserts the constraint state as a regression guard (a deterministic in-process concurrent reproduction is infeasible under the Ecto sandbox, which serializes connections by ownership).
+
+This deadlock is also a latent **production** risk under concurrent sign-ups; the deferrable-FK fix addresses both.
+
+### Async-test-safety checklist (members/groups/custom fields)
+
+Several member-creating test files historically used `async: false` with a "prevent PostgreSQL deadlocks" comment. With the deferrable-FK migration in place those files are deadlock-safe, but before flipping any such file to `async: true`:
+
+- **Prove isolation under load, not just one green run.** Re-run the file (and the full suite) under varying `--seed` **and** CPU contention; a single green run is not evidence (the deadlock and the isolation flakes below are load-dependent).
+- **Watch for separate async-isolation issues beyond the deadlock.** `index_groups_url_params_test.exs` and `member_filter_component_test.exs` showed filtered-member-leak failures (`refute html =~ name`) under concurrency that are independent of the FK deadlock — these need their own per-file isolation fix before they can run async.
+
+### StreamData generator pitfall
+
+`FilterTooNarrowError` appeared on unlucky seeds (e.g. 222) in a property test that built a value with a reject-filter (`StreamData.filter` discarding ~1/4 of generated pairs). Under full property-run counts this hits too many consecutive rejections. Fix: **construct the desired value directly** instead of generating-then-filtering (preserves the exact domain, no rejection). Prefer constructive generators over reject-filters in property tests.
+
+---
+
 ## References
 
 - Testing Standards: `CODE_GUIDELINES.md` §4
diff --git a/priv/repo/migrations/20260616165309_make_member_user_fks_deferrable.exs b/priv/repo/migrations/20260616165309_make_member_user_fks_deferrable.exs
new file mode 100644
index 0000000..2fa45fb
--- /dev/null
+++ b/priv/repo/migrations/20260616165309_make_member_user_fks_deferrable.exs
@@ -0,0 +1,32 @@
+defmodule Mv.Repo.Migrations.MakeMemberUserFksDeferrable do
+  @moduledoc """
+  Makes the members/users foreign keys DEFERRABLE INITIALLY DEFERRED.
+
+  Concurrent `create_member` transactions take FK `FOR KEY SHARE` (MultiXact)
+  locks on these foreign keys at statement time and can form a cross-transaction
+  lock cycle, producing a PostgreSQL `deadlock_detected` (40P01). Deferring the
+  FK checks to commit time breaks the cycle.
+
+  Constraint deferrability is not tracked by AshPostgres resource snapshots, so
+  this is a hand-written migration with raw `execute/2`. Do not regenerate it
+  via `mix ash_postgres.generate_migrations`.
+  """
+  use Ecto.Migration
+
+  def change do
+    execute(
+      "ALTER TABLE users ALTER CONSTRAINT users_member_id_fkey DEFERRABLE INITIALLY DEFERRED",
+      "ALTER TABLE users ALTER CONSTRAINT users_member_id_fkey NOT DEFERRABLE"
+    )
+
+    execute(
+      "ALTER TABLE users ALTER CONSTRAINT users_role_id_fkey DEFERRABLE INITIALLY DEFERRED",
+      "ALTER TABLE users ALTER CONSTRAINT users_role_id_fkey NOT DEFERRABLE"
+    )
+
+    execute(
+      "ALTER TABLE members ALTER CONSTRAINT members_membership_fee_type_id_fkey DEFERRABLE INITIALLY DEFERRED",
+      "ALTER TABLE members ALTER CONSTRAINT members_membership_fee_type_id_fkey NOT DEFERRABLE"
+    )
+  end
+end
diff --git a/test/membership/member_cycle_calculations_test.exs b/test/membership/member_cycle_calculations_test.exs
index 9be1272..860d784 100644
--- a/test/membership/member_cycle_calculations_test.exs
+++ b/test/membership/member_cycle_calculations_test.exs
@@ -4,30 +4,15 @@ defmodule Mv.Membership.MemberCycleCalculationsTest do
   """
   use Mv.DataCase, async: true
 
+  import Mv.Fixtures, only: [create_fee_type: 2, create_cycle: 4]
+
   alias Mv.MembershipFees.CalendarCycles
-  alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
 
   setup do
     system_actor = Mv.Helpers.SystemActor.get_system_actor()
     %{actor: system_actor}
   end
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs, actor) do
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   # Helper to create a member
   defp create_member(attrs, actor) do
     default_attrs = %{
@@ -41,23 +26,6 @@ defmodule Mv.Membership.MemberCycleCalculationsTest do
     member
   end
 
-  # Helper to create a cycle
-  defp create_cycle(member, fee_type, attrs, actor) do
-    default_attrs = %{
-      cycle_start: ~D[2024-01-01],
-      amount: Decimal.new("50.00"),
-      member_id: member.id,
-      membership_fee_type_id: fee_type.id,
-      status: :unpaid
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeCycle
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   describe "current_cycle_status" do
     test "returns status of current cycle for member with active cycle", %{actor: actor} do
       fee_type = create_fee_type(%{interval: :yearly}, actor)
diff --git a/test/membership/member_type_change_integration_test.exs b/test/membership/member_type_change_integration_test.exs
index 35b3137..a2baf78 100644
--- a/test/membership/member_type_change_integration_test.exs
+++ b/test/membership/member_type_change_integration_test.exs
@@ -4,9 +4,10 @@ defmodule Mv.Membership.MemberTypeChangeIntegrationTest do
   """
   use Mv.DataCase, async: true
 
+  import Mv.Fixtures, only: [create_fee_type: 2, create_cycle: 4]
+
   alias Mv.MembershipFees.CalendarCycles
   alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
 
   require Ash.Query
 
@@ -15,21 +16,6 @@ defmodule Mv.Membership.MemberTypeChangeIntegrationTest do
     %{actor: system_actor}
   end
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs, actor) do
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   # Helper to create a member
   defp create_member(attrs, actor) do
     default_attrs = %{
@@ -44,23 +30,6 @@ defmodule Mv.Membership.MemberTypeChangeIntegrationTest do
     member
   end
 
-  # Helper to create a cycle
-  defp create_cycle(member, fee_type, attrs, actor) do
-    default_attrs = %{
-      cycle_start: ~D[2024-01-01],
-      amount: Decimal.new("50.00"),
-      member_id: member.id,
-      membership_fee_type_id: fee_type.id,
-      status: :unpaid
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeCycle
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   describe "type change cycle regeneration" do
     test "future unpaid cycles are regenerated with new amount", %{actor: actor} do
       today = Date.utc_today()
diff --git a/test/membership_fees/changes/validate_same_interval_test.exs b/test/membership_fees/changes/validate_same_interval_test.exs
index 31c2847..21e0a55 100644
--- a/test/membership_fees/changes/validate_same_interval_test.exs
+++ b/test/membership_fees/changes/validate_same_interval_test.exs
@@ -4,29 +4,15 @@ defmodule Mv.MembershipFees.Changes.ValidateSameIntervalTest do
   """
   use Mv.DataCase, async: true
 
+  import Mv.Fixtures, only: [create_fee_type: 2]
+
   alias Mv.MembershipFees.Changes.ValidateSameInterval
-  alias Mv.MembershipFees.MembershipFeeType
 
   setup do
     system_actor = Mv.Helpers.SystemActor.get_system_actor()
     %{actor: system_actor}
   end
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs, actor) do
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   # Helper to create a member
   defp create_member(attrs, actor) do
     default_attrs = %{
diff --git a/test/membership_fees/member_cycle_integration_test.exs b/test/membership_fees/member_cycle_integration_test.exs
index 76f4d08..c6a1486 100644
--- a/test/membership_fees/member_cycle_integration_test.exs
+++ b/test/membership_fees/member_cycle_integration_test.exs
@@ -4,8 +4,9 @@ defmodule Mv.MembershipFees.MemberCycleIntegrationTest do
   """
   use Mv.DataCase, async: false
 
+  import Mv.Fixtures, only: [create_fee_type: 2]
+
   alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
 
   require Ash.Query
 
@@ -14,21 +15,6 @@ defmodule Mv.MembershipFees.MemberCycleIntegrationTest do
     %{actor: system_actor}
   end
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs, actor) do
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   # Helper to set up settings
   defp setup_settings(include_joining_cycle, actor) do
     {:ok, settings} = Mv.Membership.get_settings()
diff --git a/test/membership_fees/membership_fee_cycle_test.exs b/test/membership_fees/membership_fee_cycle_test.exs
index 8770134..f4f89af 100644
--- a/test/membership_fees/membership_fee_cycle_test.exs
+++ b/test/membership_fees/membership_fee_cycle_test.exs
@@ -4,29 +4,15 @@ defmodule Mv.MembershipFees.MembershipFeeCycleTest do
   """
   use Mv.DataCase, async: true
 
+  import Mv.Fixtures, only: [create_fee_type: 2, create_cycle: 4]
+
   alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
 
   setup do
     system_actor = Mv.Helpers.SystemActor.get_system_actor()
     %{actor: system_actor}
   end
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs, actor) do
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   # Helper to create a member
   defp create_member(attrs, actor) do
     default_attrs = %{
@@ -40,22 +26,6 @@ defmodule Mv.MembershipFees.MembershipFeeCycleTest do
     member
   end
 
-  # Helper to create a cycle
-  defp create_cycle(member, fee_type, attrs, actor) do
-    default_attrs = %{
-      cycle_start: ~D[2024-01-01],
-      amount: Decimal.new("50.00"),
-      member_id: member.id,
-      membership_fee_type_id: fee_type.id
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeCycle
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   describe "status defaults" do
     test "status defaults to :unpaid when creating a cycle", %{actor: actor} do
       fee_type = create_fee_type(%{interval: :yearly}, actor)
diff --git a/test/membership_fees/membership_fee_type_integration_test.exs b/test/membership_fees/membership_fee_type_integration_test.exs
index f834094..86ef284 100644
--- a/test/membership_fees/membership_fee_type_integration_test.exs
+++ b/test/membership_fees/membership_fee_type_integration_test.exs
@@ -4,6 +4,8 @@ defmodule Mv.MembershipFees.MembershipFeeTypeIntegrationTest do
   """
   use Mv.DataCase, async: false
 
+  import Mv.Fixtures, only: [create_fee_type: 2]
+
   alias Mv.Membership.Member
   alias Mv.MembershipFees.MembershipFeeCycle
   alias Mv.MembershipFees.MembershipFeeType
@@ -15,21 +17,6 @@ defmodule Mv.MembershipFees.MembershipFeeTypeIntegrationTest do
     %{actor: system_actor}
   end
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs, actor) do
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   describe "admin can create membership fee type" do
     test "creates type with all fields", %{actor: actor} do
       attrs = %{
diff --git a/test/mv/membership/members_pdf_test.exs b/test/mv/membership/members_pdf_test.exs
index 2b83e3b..3ae18cf 100644
--- a/test/mv/membership/members_pdf_test.exs
+++ b/test/mv/membership/members_pdf_test.exs
@@ -274,17 +274,38 @@ defmodule Mv.Membership.MembersPDFTest do
 
       assert {:ok, _pdf_binary} = result
 
-      # Wait a bit for cleanup (async cleanup might take a moment)
-      Process.sleep(100)
-
-      # Count temp directories after
-      after_count =
+      count_export_dirs = fn ->
         temp_base
         |> File.ls!()
         |> Enum.count(fn name -> String.starts_with?(name, "mv_pdf_export_") end)
+      end
+
+      # Poll the observable cleanup condition (temp-dir count returns to the baseline)
+      # with a bounded deadline instead of a fixed sleep, so the test waits no longer
+      # than the cleanup actually needs and still fails if cleanup never runs.
+      after_count = poll_until_cleaned(count_export_dirs, before_count, 100)
 
       # Should have same or fewer temp dirs (cleanup should have run)
       assert after_count <= before_count + 1
     end
   end
+
+  # Bounded poll: returns the export-dir count once it drops back to the baseline
+  # (cleanup done), or the last observed count when the attempt budget is exhausted
+  # (so the caller's assertion reports the real state on a genuine cleanup stall).
+  defp poll_until_cleaned(count_fun, baseline, attempts_left) do
+    current = count_fun.()
+
+    cond do
+      current <= baseline ->
+        current
+
+      attempts_left <= 0 ->
+        current
+
+      true ->
+        Process.sleep(10)
+        poll_until_cleaned(count_fun, baseline, attempts_left - 1)
+    end
+  end
 end
diff --git a/test/mv/membership_fees/cycle_generator_edge_cases_test.exs b/test/mv/membership_fees/cycle_generator_edge_cases_test.exs
index a9e3316..eb9da26 100644
--- a/test/mv/membership_fees/cycle_generator_edge_cases_test.exs
+++ b/test/mv/membership_fees/cycle_generator_edge_cases_test.exs
@@ -12,9 +12,10 @@ defmodule Mv.MembershipFees.CycleGeneratorEdgeCasesTest do
   """
   use Mv.DataCase, async: false
 
+  import Mv.Fixtures, only: [create_fee_type: 2]
+
   alias Mv.MembershipFees.CycleGenerator
   alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
 
   require Ash.Query
 
@@ -23,21 +24,6 @@ defmodule Mv.MembershipFees.CycleGeneratorEdgeCasesTest do
     %{actor: system_actor}
   end
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs, actor) do
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   # Helper to create a member. Note: If membership_fee_type_id is provided,
   # cycles will be auto-generated during creation in test environment.
   defp create_member(attrs, actor) do
diff --git a/test/mv/membership_fees/cycle_generator_test.exs b/test/mv/membership_fees/cycle_generator_test.exs
index f193903..a715ca9 100644
--- a/test/mv/membership_fees/cycle_generator_test.exs
+++ b/test/mv/membership_fees/cycle_generator_test.exs
@@ -4,9 +4,10 @@ defmodule Mv.MembershipFees.CycleGeneratorTest do
   """
   use Mv.DataCase, async: false
 
+  import Mv.Fixtures, only: [create_fee_type: 2]
+
   alias Mv.MembershipFees.CycleGenerator
   alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
 
   require Ash.Query
 
@@ -15,21 +16,6 @@ defmodule Mv.MembershipFees.CycleGeneratorTest do
     %{actor: system_actor}
   end
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs, actor) do
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   # Helper to create a member without triggering cycle generation
   defp create_member_without_cycles(attrs, actor) do
     default_attrs = %{
diff --git a/test/mv/membership_fees/membership_fee_cycle_policies_test.exs b/test/mv/membership_fees/membership_fee_cycle_policies_test.exs
index cf7e889..e3e37ba 100644
--- a/test/mv/membership_fees/membership_fee_cycle_policies_test.exs
+++ b/test/mv/membership_fees/membership_fee_cycle_policies_test.exs
@@ -8,6 +8,8 @@ defmodule Mv.MembershipFees.MembershipFeeCyclePoliciesTest do
   """
   use Mv.DataCase, async: false
 
+  import Mv.Fixtures, only: [create_fee_type: 1, create_cycle: 3]
+
   alias Mv.Membership
   alias Mv.MembershipFees
 
@@ -32,41 +34,15 @@ defmodule Mv.MembershipFees.MembershipFeeCyclePoliciesTest do
     member
   end
 
-  defp create_fee_type_fixture do
-    admin = Mv.Fixtures.user_with_role_fixture("admin")
-
-    {:ok, fee_type} =
-      MembershipFees.create_membership_fee_type(
-        %{
-          name: "Test Fee #{System.unique_integer([:positive])}",
-          amount: Decimal.new("10.00"),
-          interval: :yearly,
-          description: "Test"
-        },
-        actor: admin
-      )
-
-    fee_type
+  defp fee_type_fixture do
+    create_fee_type(%{amount: Decimal.new("10.00"), description: "Test"})
   end
 
-  defp create_cycle_fixture do
-    admin = Mv.Fixtures.user_with_role_fixture("admin")
-    member = create_member_fixture()
-    fee_type = create_fee_type_fixture()
-
-    {:ok, cycle} =
-      MembershipFees.create_membership_fee_cycle(
-        %{
-          member_id: member.id,
-          membership_fee_type_id: fee_type.id,
-          cycle_start: Date.utc_today(),
-          amount: Decimal.new("10.00"),
-          status: :unpaid
-        },
-        actor: admin
-      )
-
-    cycle
+  defp cycle_fixture do
+    create_cycle(create_member_fixture(), fee_type_fixture(), %{
+      cycle_start: Date.utc_today(),
+      amount: Decimal.new("10.00")
+    })
   end
 
   describe "own_data permission set" do
@@ -74,7 +50,7 @@ defmodule Mv.MembershipFees.MembershipFeeCyclePoliciesTest do
       user = Mv.Fixtures.user_with_role_fixture("own_data")
       linked_member = create_member_fixture()
       other_member = create_member_fixture()
-      fee_type = create_fee_type_fixture()
+      fee_type = fee_type_fixture()
       admin = Mv.Fixtures.user_with_role_fixture("admin")
 
       user =
@@ -130,7 +106,7 @@ defmodule Mv.MembershipFees.MembershipFeeCyclePoliciesTest do
   describe "read_only permission set" do
     setup %{actor: actor} do
       user = Mv.Fixtures.user_with_role_fixture("read_only")
-      cycle = create_cycle_fixture()
+      cycle = cycle_fixture()
       %{actor: actor, user: user, cycle: cycle}
     end
 
@@ -156,7 +132,7 @@ defmodule Mv.MembershipFees.MembershipFeeCyclePoliciesTest do
 
     test "cannot create cycle (returns forbidden)", %{user: user, actor: _actor} do
       member = create_member_fixture()
-      fee_type = create_fee_type_fixture()
+      fee_type = fee_type_fixture()
 
       assert {:error, %Ash.Error.Forbidden{}} =
                MembershipFees.create_membership_fee_cycle(
@@ -180,7 +156,7 @@ defmodule Mv.MembershipFees.MembershipFeeCyclePoliciesTest do
   describe "normal_user permission set" do
     setup %{actor: actor} do
       user = Mv.Fixtures.user_with_role_fixture("normal_user")
-      cycle = create_cycle_fixture()
+      cycle = cycle_fixture()
       %{actor: actor, user: user, cycle: cycle}
     end
 
@@ -210,7 +186,7 @@ defmodule Mv.MembershipFees.MembershipFeeCyclePoliciesTest do
 
     test "can create cycle", %{user: user, actor: _actor} do
       member = create_member_fixture()
-      fee_type = create_fee_type_fixture()
+      fee_type = fee_type_fixture()
 
       assert {:ok, created} =
                MembershipFees.create_membership_fee_cycle(
@@ -235,7 +211,7 @@ defmodule Mv.MembershipFees.MembershipFeeCyclePoliciesTest do
   describe "admin permission set" do
     setup %{actor: actor} do
       user = Mv.Fixtures.user_with_role_fixture("admin")
-      cycle = create_cycle_fixture()
+      cycle = cycle_fixture()
       %{actor: actor, user: user, cycle: cycle}
     end
 
@@ -270,7 +246,7 @@ defmodule Mv.MembershipFees.MembershipFeeCyclePoliciesTest do
 
     test "can create cycle", %{user: user, actor: _actor} do
       member = create_member_fixture()
-      fee_type = create_fee_type_fixture()
+      fee_type = fee_type_fixture()
 
       assert {:ok, created} =
                MembershipFees.create_membership_fee_cycle(
diff --git a/test/mv/repo/deferrable_fk_test.exs b/test/mv/repo/deferrable_fk_test.exs
new file mode 100644
index 0000000..4127082
--- /dev/null
+++ b/test/mv/repo/deferrable_fk_test.exs
@@ -0,0 +1,37 @@
+defmodule Mv.DeferrableFkTest do
+  @moduledoc """
+  Regression guard for the deferrable-FK migration.
+
+  Asserts the schema property directly (`condeferred = true`) for the three
+  members/users foreign keys. A multi-connection deadlock reproduction cannot
+  be made deterministic under the Ecto sandbox (ownership serializes
+  connections), so the structural assertion is the guard here; see the
+  migration moduledoc for the full FOR-KEY-SHARE/MultiXact deadlock rationale.
+  """
+  use Mv.DataCase, async: true
+
+  @deferrable_fks ~w(
+    users_member_id_fkey
+    users_role_id_fkey
+    members_membership_fee_type_id_fkey
+  )
+
+  test "member/user foreign keys are DEFERRABLE INITIALLY DEFERRED" do
+    query = """
+    SELECT conname, condeferrable, condeferred
+    FROM pg_constraint
+    WHERE conname = ANY($1)
+    """
+
+    {:ok, %{rows: rows}} = Mv.Repo.query(query, [@deferrable_fks])
+
+    found = Map.new(rows, fn [name, deferrable, deferred] -> {name, {deferrable, deferred}} end)
+
+    for fk <- @deferrable_fks do
+      assert Map.has_key?(found, fk), "expected foreign key #{fk} to exist"
+
+      assert found[fk] == {true, true},
+             "expected #{fk} to be DEFERRABLE INITIALLY DEFERRED, got #{inspect(found[fk])}"
+    end
+  end
+end
diff --git a/test/mv/statistics_test.exs b/test/mv/statistics_test.exs
index 874681f..19533e2 100644
--- a/test/mv/statistics_test.exs
+++ b/test/mv/statistics_test.exs
@@ -5,11 +5,11 @@ defmodule Mv.StatisticsTest do
   use Mv.DataCase, async: true
 
   import Ash.Expr
+  import Mv.Fixtures, only: [create_fee_type: 2]
 
   alias Mv.Membership.Member
   alias Mv.MembershipFees
   alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
   alias Mv.Statistics
 
   require Ash.Query
@@ -19,22 +19,6 @@ defmodule Mv.StatisticsTest do
     %{actor: actor}
   end
 
-  defp create_fee_type(actor, attrs) do
-    MembershipFeeType
-    |> Ash.Changeset.for_create(
-      :create,
-      Map.merge(
-        %{
-          name: "Test Fee #{System.unique_integer([:positive])}",
-          amount: Decimal.new("50.00"),
-          interval: :yearly
-        },
-        attrs
-      )
-    )
-    |> Ash.create!(actor: actor)
-  end
-
   describe "first_join_year/1" do
     test "returns the year of the earliest join_date", %{actor: actor} do
       Mv.Fixtures.member_fixture(%{join_date: ~D[2019-03-15]})
@@ -132,7 +116,7 @@ defmodule Mv.StatisticsTest do
     end
 
     test "returns totals by status for cycles in that year", %{actor: actor} do
-      fee_type = create_fee_type(actor, %{amount: Decimal.new("50.00")})
+      fee_type = create_fee_type(%{amount: Decimal.new("50.00")}, actor)
 
       # Creating members with fee type triggers cycle generation (2020..today). We use 2024 cycles.
       _member1 =
@@ -172,8 +156,8 @@ defmodule Mv.StatisticsTest do
     test "when fee_type_id is passed in opts, returns only cycles of that fee type", %{
       actor: actor
     } do
-      fee_type_a = create_fee_type(actor, %{amount: Decimal.new("30.00")})
-      fee_type_b = create_fee_type(actor, %{amount: Decimal.new("70.00")})
+      fee_type_a = create_fee_type(%{amount: Decimal.new("30.00")}, actor)
+      fee_type_b = create_fee_type(%{amount: Decimal.new("70.00")}, actor)
 
       _m1 =
         Mv.Fixtures.member_fixture(%{
@@ -208,7 +192,7 @@ defmodule Mv.StatisticsTest do
     end
 
     test "returns sum of amount for all unpaid cycles", %{actor: actor} do
-      fee_type = create_fee_type(actor, %{amount: Decimal.new("50.00")})
+      fee_type = create_fee_type(%{amount: Decimal.new("50.00")}, actor)
 
       _member =
         Mv.Fixtures.member_fixture(%{
diff --git a/test/mv_web/components/member_filter_component_test.exs b/test/mv_web/components/member_filter_component_test.exs
index 9364eaa..b93accc 100644
--- a/test/mv_web/components/member_filter_component_test.exs
+++ b/test/mv_web/components/member_filter_component_test.exs
@@ -8,7 +8,10 @@ defmodule MvWeb.Components.MemberFilterComponentTest do
   - Button label and badge logic
   - Filtering to show only boolean custom fields
   """
-  # async: false to prevent PostgreSQL deadlocks when running LiveView tests against DB
+  # Kept async: false. The deferrable-FK migration removed the concurrent
+  # create_member deadlock, but this file additionally showed an async-isolation
+  # failure under load (filtered members from a parallel test leaking in), so it
+  # is not trivially async-safe; resolving that is a separate follow-up.
   use MvWeb.ConnCase, async: false
 
   use Gettext, backend: MvWeb.Gettext
diff --git a/test/mv_web/live/import_live_test.exs b/test/mv_web/live/import_live_test.exs
index bd5cdec..8837fc6 100644
--- a/test/mv_web/live/import_live_test.exs
+++ b/test/mv_web/live/import_live_test.exs
@@ -37,7 +37,27 @@ defmodule MvWeb.ImportLiveTest do
     confirm_import(view)
   end
 
-  defp wait_for_import_completion, do: Process.sleep(1000)
+  # Waits for the asynchronous chunk-import to finish by polling the rendered
+  # results panel, instead of a fixed sleep. In the test sandbox the chunks run
+  # in-process and signal completion via self-messages; each render/2 forces the
+  # LiveView to drain its mailbox before replying, so the panel appears once all
+  # chunk messages have been processed. Bounded so a genuine stall still fails.
+  defp wait_for_import_completion(view) do
+    wait_for_import_completion(view, 200)
+  end
+
+  defp wait_for_import_completion(_view, 0) do
+    flunk("import did not complete: results panel never rendered")
+  end
+
+  defp wait_for_import_completion(view, attempts_left) do
+    if has_element?(view, "[data-testid='import-results-panel']") do
+      :ok
+    else
+      Process.sleep(10)
+      wait_for_import_completion(view, attempts_left - 1)
+    end
+  end
 
   # ---------- Business logic: Authorization ----------
   describe "Authorization" do
@@ -67,7 +87,7 @@ defmodule MvWeb.ImportLiveTest do
 
       {:ok, view, _html} = live(conn, ~p"/admin/import")
       run_full_import(view, csv_content)
-      wait_for_import_completion()
+      wait_for_import_completion(view)
 
       assert has_element?(view, "[data-testid='import-results-panel']")
       assert has_element?(view, "[data-testid='import-summary']")
@@ -131,7 +151,7 @@ defmodule MvWeb.ImportLiveTest do
     } do
       {:ok, view, _html} = live(conn, ~p"/admin/import")
       run_full_import(view, csv_content, "invalid_import.csv")
-      wait_for_import_completion()
+      wait_for_import_completion(view)
 
       assert has_element?(view, "[data-testid='import-results-panel']")
       assert has_element?(view, "[data-testid='import-error-list']")
@@ -150,7 +170,7 @@ defmodule MvWeb.ImportLiveTest do
         for i <- 1..100, do: "Row#{i};Last#{i};;Country#{i};City#{i};Street#{i};12345\n"
 
       run_full_import(view, header <> Enum.join(invalid_rows), "large_invalid.csv")
-      wait_for_import_completion()
+      wait_for_import_completion(view)
 
       assert has_element?(view, "[data-testid='import-results-panel']")
       assert has_element?(view, "[data-testid='import-error-list']")
@@ -182,7 +202,7 @@ defmodule MvWeb.ImportLiveTest do
         |> File.read!()
 
       run_full_import(view, csv_content, "bom_import.csv")
-      wait_for_import_completion()
+      wait_for_import_completion(view)
 
       assert has_element?(view, "[data-testid='import-results-panel']")
       html = render(view)
@@ -200,7 +220,7 @@ defmodule MvWeb.ImportLiveTest do
         |> File.read!()
 
       run_full_import(view, csv_content, "empty_lines.csv")
-      wait_for_import_completion()
+      wait_for_import_completion(view)
 
       assert has_element?(view, "[data-testid='import-error-list']")
       html = render(view)
@@ -214,7 +234,7 @@ defmodule MvWeb.ImportLiveTest do
     } do
       {:ok, view, _html} = live(conn, ~p"/admin/import")
       run_full_import(view, csv_content, "unknown_custom.csv")
-      wait_for_import_completion()
+      wait_for_import_completion(view)
 
       assert has_element?(view, "[data-testid='import-results-panel']")
       assert has_element?(view, "[data-testid='import-warnings']")
@@ -279,7 +299,7 @@ defmodule MvWeb.ImportLiveTest do
 
       {:ok, view, _html} = live(conn, ~p"/admin/import")
       run_full_import(view, csv_content)
-      wait_for_import_completion()
+      wait_for_import_completion(view)
       assert has_element?(view, "[data-testid='import-progress-container']")
       html = render(view)
       assert html =~ "aria-live"
@@ -342,7 +362,7 @@ defmodule MvWeb.ImportLiveTest do
     } do
       {:ok, view, _html} = live(conn, ~p"/admin/import")
       run_full_import(view, csv_content)
-      wait_for_import_completion()
+      wait_for_import_completion(view)
 
       assert has_element?(view, "[data-testid='import-results-panel']")
 
diff --git a/test/mv_web/live/member_live/date_filter_property_test.exs b/test/mv_web/live/member_live/date_filter_property_test.exs
index fcce2a3..8844f91 100644
--- a/test/mv_web/live/member_live/date_filter_property_test.exs
+++ b/test/mv_web/live/member_live/date_filter_property_test.exs
@@ -20,11 +20,12 @@ defmodule MvWeb.MemberLive.Index.DateFilterPropertyTest do
 
   # Generators -----------------------------------------------------------
 
+  defp date_gen do
+    map(integer(-3650..3650), &Date.add(~D[2000-01-01], &1))
+  end
+
   defp optional_date_gen do
-    one_of([
-      constant(nil),
-      map(integer(-3650..3650), &Date.add(~D[2000-01-01], &1))
-    ])
+    one_of([constant(nil), date_gen()])
   end
 
   defp exit_date_mode_gen do
@@ -57,19 +58,25 @@ defmodule MvWeb.MemberLive.Index.DateFilterPropertyTest do
 
   # Property -------------------------------------------------------------
 
+  # Generates a {from, to} pair with at least one bound set. Built by construction
+  # (pick which bounds are set, then generate the required dates) rather than by
+  # filtering out the both-nil case, so StreamData never rejects values and cannot
+  # raise FilterTooNarrowError on unlucky seeds.
   defp bound_pair_with_at_least_one_set_gen do
     gen all(
-          from <- optional_date_gen(),
-          to <- optional_date_gen(),
-          from != nil or to != nil
+          which <- member_of([:from_only, :to_only, :both]),
+          date_a <- date_gen(),
+          date_b <- date_gen()
         ) do
-      {from, to}
+      case which do
+        :from_only -> {date_a, nil}
+        :to_only -> {nil, date_a}
+        :both -> {date_a, date_b}
+      end
     end
   end
 
-  defp value_date_gen do
-    map(integer(-3650..3650), &Date.add(~D[2000-01-01], &1))
-  end
+  defp value_date_gen, do: date_gen()
 
   # Property -------------------------------------------------------------
 
diff --git a/test/mv_web/live/membership_fee_type_live/form_test.exs b/test/mv_web/live/membership_fee_type_live/form_test.exs
index a836c4d..998fb65 100644
--- a/test/mv_web/live/membership_fee_type_live/form_test.exs
+++ b/test/mv_web/live/membership_fee_type_live/form_test.exs
@@ -5,6 +5,7 @@ defmodule MvWeb.MembershipFeeTypeLive.FormTest do
   use MvWeb.ConnCase, async: false
 
   import Phoenix.LiveViewTest
+  import Mv.Fixtures, only: [create_fee_type: 1]
 
   alias Mv.MembershipFees.MembershipFeeType
 
@@ -17,23 +18,6 @@ defmodule MvWeb.MembershipFeeTypeLive.FormTest do
     %{conn: authenticated_conn, user: user}
   end
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs) do
-    system_actor = Mv.Helpers.SystemActor.get_system_actor()
-
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: system_actor)
-  end
-
   # Helper to create a member
   defp create_member(attrs) do
     system_actor = Mv.Helpers.SystemActor.get_system_actor()
diff --git a/test/mv_web/live/membership_fee_type_live/index_test.exs b/test/mv_web/live/membership_fee_type_live/index_test.exs
index c65341f..8c99d90 100644
--- a/test/mv_web/live/membership_fee_type_live/index_test.exs
+++ b/test/mv_web/live/membership_fee_type_live/index_test.exs
@@ -5,6 +5,7 @@ defmodule MvWeb.MembershipFeeTypeLive.IndexTest do
   use MvWeb.ConnCase, async: false
 
   import Phoenix.LiveViewTest
+  import Mv.Fixtures, only: [create_fee_type: 2]
 
   alias Mv.MembershipFees.MembershipFeeType
 
@@ -13,22 +14,6 @@ defmodule MvWeb.MembershipFeeTypeLive.IndexTest do
   # Use global setup from ConnCase which provides admin user with role
   # No custom setup needed
 
-  # Helper to create a membership fee type
-  # Uses admin_user to test permissions (UI-/Permissions-nah)
-  defp create_fee_type(attrs, admin_user) do
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: admin_user)
-  end
-
   # Helper to create a member. Requires actor (e.g. admin_user from setup); no fallback so
   # missing-actor bugs are not masked in tests.
   defp create_member(attrs, actor) do
diff --git a/test/mv_web/member_live/form_membership_fee_type_test.exs b/test/mv_web/member_live/form_membership_fee_type_test.exs
index 5382dfc..01812df 100644
--- a/test/mv_web/member_live/form_membership_fee_type_test.exs
+++ b/test/mv_web/member_live/form_membership_fee_type_test.exs
@@ -5,27 +5,10 @@ defmodule MvWeb.MemberLive.FormMembershipFeeTypeTest do
   use MvWeb.ConnCase, async: false
 
   import Phoenix.LiveViewTest
-
-  alias Mv.MembershipFees.MembershipFeeType
+  import Mv.Fixtures, only: [create_fee_type: 2]
 
   require Ash.Query
 
-  # Helper to create a membership fee type
-  # Uses admin_user to test permissions (UI-/Permissions-nah)
-  defp create_fee_type(attrs, admin_user) do
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: admin_user)
-  end
-
   # Helper to create a member
   # Uses admin_user to test permissions (UI-/Permissions-nah)
   defp create_member(attrs, admin_user) do
diff --git a/test/mv_web/member_live/index/membership_fee_status_test.exs b/test/mv_web/member_live/index/membership_fee_status_test.exs
index 5d96e68..8412f61 100644
--- a/test/mv_web/member_live/index/membership_fee_status_test.exs
+++ b/test/mv_web/member_live/index/membership_fee_status_test.exs
@@ -4,30 +4,13 @@ defmodule MvWeb.MemberLive.Index.MembershipFeeStatusTest do
   """
   use Mv.DataCase, async: false
 
+  import Mv.Fixtures, only: [create_fee_type: 1, create_cycle: 3]
+
   alias Mv.Membership.Member
-  alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
   alias MvWeb.MemberLive.Index.MembershipFeeStatus
 
   require Ash.Query
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs) do
-    system_actor = Mv.Helpers.SystemActor.get_system_actor()
-
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: system_actor)
-  end
-
   # Helper to create a member
   defp create_member(attrs) do
     system_actor = Mv.Helpers.SystemActor.get_system_actor()
@@ -43,27 +26,6 @@ defmodule MvWeb.MemberLive.Index.MembershipFeeStatusTest do
     member
   end
 
-  # Helper to create a cycle
-  # Note: Does not delete existing cycles - tests should manage their own test data
-  # If cleanup is needed, it should be done in setup or explicitly in the test
-  defp create_cycle(member, fee_type, attrs) do
-    system_actor = Mv.Helpers.SystemActor.get_system_actor()
-
-    default_attrs = %{
-      cycle_start: ~D[2023-01-01],
-      amount: Decimal.new("50.00"),
-      member_id: member.id,
-      membership_fee_type_id: fee_type.id,
-      status: :unpaid
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeCycle
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: system_actor)
-  end
-
   describe "load_cycles_for_members/2" do
     test "efficiently loads cycles for members" do
       fee_type = create_fee_type(%{interval: :yearly})
diff --git a/test/mv_web/member_live/index_custom_fields_display_test.exs b/test/mv_web/member_live/index_custom_fields_display_test.exs
index e4e1824..74db2bf 100644
--- a/test/mv_web/member_live/index_custom_fields_display_test.exs
+++ b/test/mv_web/member_live/index_custom_fields_display_test.exs
@@ -9,7 +9,10 @@ defmodule MvWeb.MemberLive.IndexCustomFieldsDisplayTest do
   - Custom field values are correctly formatted for different types
   - Members without custom field values show empty cell or "-"
   """
-  # async: false to prevent PostgreSQL deadlocks when creating members and custom fields
+  # Kept async: false as a deferred scope decision. The deferrable-FK migration
+  # removed the concurrent-create_member deadlock that previously forced this, so
+  # re-flipping this members/custom-fields suite to async is a possible follow-up
+  # rather than part of the original change.
   use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
 
diff --git a/test/mv_web/member_live/index_field_visibility_test.exs b/test/mv_web/member_live/index_field_visibility_test.exs
index 21c75ae..63dff1c 100644
--- a/test/mv_web/member_live/index_field_visibility_test.exs
+++ b/test/mv_web/member_live/index_field_visibility_test.exs
@@ -10,7 +10,10 @@ defmodule MvWeb.MemberLive.IndexFieldVisibilityTest do
   - Integration with member list display
   - Custom fields visibility
   """
-  # async: false to prevent PostgreSQL deadlocks when creating members and custom fields
+  # Kept async: false as a deferred scope decision. The deferrable-FK migration
+  # removed the concurrent-create_member deadlock that previously forced this, so
+  # re-flipping this members/custom-fields suite to async is a possible follow-up
+  # rather than part of the original change.
   use MvWeb.ConnCase, async: false
 
   import Phoenix.LiveViewTest
@@ -158,9 +161,6 @@ defmodule MvWeb.MemberLive.IndexFieldVisibilityTest do
       |> element("button[phx-click='select_item'][phx-value-item='email']")
       |> render_click()
 
-      # Wait for update
-      :timer.sleep(100)
-
       # Email should no longer be visible
       html = render(view)
       refute html =~ "alice@example.com"
@@ -187,9 +187,6 @@ defmodule MvWeb.MemberLive.IndexFieldVisibilityTest do
       |> element("button[phx-click='select_item'][phx-value-item='#{custom_field_string}']")
       |> render_click()
 
-      # Wait for update
-      :timer.sleep(100)
-
       # Custom field should no longer be visible
       html = render(view)
       refute html =~ "M001"
@@ -214,9 +211,6 @@ defmodule MvWeb.MemberLive.IndexFieldVisibilityTest do
       |> element("button[phx-click='select_all']")
       |> render_click()
 
-      # Wait for update
-      :timer.sleep(100)
-
       # All fields should be visible
       html = render(view)
       assert html =~ "alice@example.com"
@@ -238,9 +232,6 @@ defmodule MvWeb.MemberLive.IndexFieldVisibilityTest do
       |> element("button[phx-click='select_none']")
       |> render_click()
 
-      # Wait for update
-      :timer.sleep(100)
-
       # Only first_name should be visible (it's always shown)
       html = render(view)
       # Email and street should be hidden
@@ -263,9 +254,6 @@ defmodule MvWeb.MemberLive.IndexFieldVisibilityTest do
       |> element("button[phx-click='select_item'][phx-value-item='email']")
       |> render_click()
 
-      # Wait for URL update
-      :timer.sleep(100)
-
       # Check that URL contains fields parameter
       # Note: In LiveView tests, we check the rendered HTML for the updated state
       # The actual URL update happens via push_patch
@@ -330,8 +318,6 @@ defmodule MvWeb.MemberLive.IndexFieldVisibilityTest do
       |> element("button[phx-click='select_item'][phx-value-item='email']")
       |> render_click()
 
-      :timer.sleep(100)
-
       html = render(view)
       refute html =~ "alice@example.com"
     end
@@ -388,8 +374,6 @@ defmodule MvWeb.MemberLive.IndexFieldVisibilityTest do
         view
         |> element("button[phx-click='select_item'][phx-value-item='email']")
         |> render_click()
-
-        :timer.sleep(50)
       end
 
       # Should still work correctly
@@ -459,9 +443,6 @@ defmodule MvWeb.MemberLive.IndexFieldVisibilityTest do
       |> element("button[phx-click='select_item'][phx-value-item='email']")
       |> render_keydown(%{key: "Enter"})
 
-      # Wait for update
-      :timer.sleep(100)
-
       # Email should no longer be visible
       html = render(view)
       refute html =~ "alice@example.com"
diff --git a/test/mv_web/member_live/index_groups_accessibility_test.exs b/test/mv_web/member_live/index_groups_accessibility_test.exs
index 1644d5f..bfe47c4 100644
--- a/test/mv_web/member_live/index_groups_accessibility_test.exs
+++ b/test/mv_web/member_live/index_groups_accessibility_test.exs
@@ -8,7 +8,10 @@ defmodule MvWeb.MemberLive.IndexGroupsAccessibilityTest do
   - Sort header has aria-label for screen reader
   - Keyboard navigation works (Tab through filter, sort header)
   """
-  # async: false to prevent PostgreSQL deadlocks when creating members and groups
+  # Kept async: false as a deferred scope decision. The deferrable-FK migration
+  # removed the concurrent-create_member deadlock that previously forced this, so
+  # re-flipping this members/groups suite to async is a possible follow-up rather
+  # than part of the original change.
   use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
 
diff --git a/test/mv_web/member_live/index_groups_display_test.exs b/test/mv_web/member_live/index_groups_display_test.exs
index 4521942..ed817dd 100644
--- a/test/mv_web/member_live/index_groups_display_test.exs
+++ b/test/mv_web/member_live/index_groups_display_test.exs
@@ -8,7 +8,10 @@ defmodule MvWeb.MemberLive.IndexGroupsDisplayTest do
   - No badge for members without groups
   - Badge shows group name correctly
   """
-  # async: false to prevent PostgreSQL deadlocks when creating members and groups
+  # Kept async: false as a deferred scope decision. The deferrable-FK migration
+  # removed the concurrent-create_member deadlock that previously forced this, so
+  # re-flipping this members/groups suite to async is a possible follow-up rather
+  # than part of the original change.
   use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
 
diff --git a/test/mv_web/member_live/index_groups_filter_test.exs b/test/mv_web/member_live/index_groups_filter_test.exs
index 48a335a..c8d5160 100644
--- a/test/mv_web/member_live/index_groups_filter_test.exs
+++ b/test/mv_web/member_live/index_groups_filter_test.exs
@@ -6,7 +6,10 @@ defmodule MvWeb.MemberLive.IndexGroupsFilterTest do
   All / Yes / No (per group). Multiple active group filters combine with AND
   (member must match all selected group conditions).
   """
-  # async: false to prevent PostgreSQL deadlocks when creating members and groups
+  # Kept async: false as a deferred scope decision. The deferrable-FK migration
+  # removed the concurrent-create_member deadlock that previously forced this, so
+  # re-flipping this members/groups suite to async is a possible follow-up rather
+  # than part of the original change.
   use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
 
diff --git a/test/mv_web/member_live/index_groups_integration_test.exs b/test/mv_web/member_live/index_groups_integration_test.exs
index 3c32f4c..cae9ce1 100644
--- a/test/mv_web/member_live/index_groups_integration_test.exs
+++ b/test/mv_web/member_live/index_groups_integration_test.exs
@@ -10,7 +10,10 @@ defmodule MvWeb.MemberLive.IndexGroupsIntegrationTest do
   - Groups work with existing search (but not testing search integration itself)
   - Member index search by group name returns members in that group (Issue #375)
   """
-  # async: false to prevent PostgreSQL deadlocks when creating members and groups
+  # Kept async: false as a deferred scope decision. The deferrable-FK migration
+  # removed the concurrent-create_member deadlock that previously forced this, so
+  # re-flipping this members/groups suite to async is a possible follow-up rather
+  # than part of the original change.
   use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
 
diff --git a/test/mv_web/member_live/index_groups_performance_test.exs b/test/mv_web/member_live/index_groups_performance_test.exs
index c5f170a..6d05908 100644
--- a/test/mv_web/member_live/index_groups_performance_test.exs
+++ b/test/mv_web/member_live/index_groups_performance_test.exs
@@ -8,7 +8,10 @@ defmodule MvWeb.MemberLive.IndexGroupsPerformanceTest do
   - Filter works at database level (not in-memory)
   - Sort runs in-memory but uses preloaded group data (no extra DB queries)
   """
-  # async: false to prevent PostgreSQL deadlocks when creating members and groups
+  # Kept async: false as a deferred scope decision. The deferrable-FK migration
+  # removed the concurrent-create_member deadlock that previously forced this, so
+  # re-flipping this members/groups suite to async is a possible follow-up rather
+  # than part of the original change.
   use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
 
diff --git a/test/mv_web/member_live/index_groups_sorting_test.exs b/test/mv_web/member_live/index_groups_sorting_test.exs
index 0828a33..6e19779 100644
--- a/test/mv_web/member_live/index_groups_sorting_test.exs
+++ b/test/mv_web/member_live/index_groups_sorting_test.exs
@@ -2,7 +2,10 @@ defmodule MvWeb.MemberLive.IndexGroupsSortingTest do
   @moduledoc """
   Tests for sorting by groups in the member overview.
   """
-  # async: false to prevent PostgreSQL deadlocks when creating members and groups
+  # Kept async: false as a deferred scope decision. The deferrable-FK migration
+  # removed the concurrent-create_member deadlock that previously forced this, so
+  # re-flipping this members/groups suite to async is a possible follow-up rather
+  # than part of the original change.
   use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
 
diff --git a/test/mv_web/member_live/index_groups_url_params_test.exs b/test/mv_web/member_live/index_groups_url_params_test.exs
index d2f3b7b..8ce82aa 100644
--- a/test/mv_web/member_live/index_groups_url_params_test.exs
+++ b/test/mv_web/member_live/index_groups_url_params_test.exs
@@ -9,7 +9,10 @@ defmodule MvWeb.MemberLive.IndexGroupsUrlParamsTest do
   - URL parameters work with other parameters (query, sort_field, etc.)
   - URL is bookmarkable (filter/sorting persist)
   """
-  # async: false to prevent PostgreSQL deadlocks when creating members and groups
+  # Kept async: false. The deferrable-FK migration removed the concurrent
+  # create_member deadlock, but this file additionally showed an async-isolation
+  # failure under load (filtered members from a parallel test leaking in), so it
+  # is not trivially async-safe; resolving that is a separate follow-up.
   use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
 
diff --git a/test/mv_web/member_live/index_membership_fee_status_test.exs b/test/mv_web/member_live/index_membership_fee_status_test.exs
index ce6bee8..2efe055 100644
--- a/test/mv_web/member_live/index_membership_fee_status_test.exs
+++ b/test/mv_web/member_live/index_membership_fee_status_test.exs
@@ -5,29 +5,12 @@ defmodule MvWeb.MemberLive.IndexMembershipFeeStatusTest do
   use MvWeb.ConnCase, async: false
 
   import Phoenix.LiveViewTest
+  import Mv.Fixtures, only: [create_fee_type: 1, create_cycle: 3]
 
   alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
 
   require Ash.Query
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs) do
-    system_actor = Mv.Helpers.SystemActor.get_system_actor()
-
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: system_actor)
-  end
-
   # Helper to create a member
   defp create_member(attrs) do
     system_actor = Mv.Helpers.SystemActor.get_system_actor()
@@ -43,38 +26,16 @@ defmodule MvWeb.MemberLive.IndexMembershipFeeStatusTest do
     member
   end
 
-  # Helper to create a cycle
-  defp create_cycle(member, fee_type, attrs) do
-    system_actor = Mv.Helpers.SystemActor.get_system_actor()
-
-    # Delete any auto-generated cycles first to avoid conflicts
-    existing_cycles =
-      MembershipFeeCycle
-      |> Ash.Query.filter(member_id == ^member.id)
-      |> Ash.read!(actor: system_actor)
-
-    Enum.each(existing_cycles, fn cycle -> Ash.destroy!(cycle, actor: system_actor) end)
-
-    default_attrs = %{
-      cycle_start: ~D[2023-01-01],
-      amount: Decimal.new("50.00"),
-      member_id: member.id,
-      membership_fee_type_id: fee_type.id,
-      status: :unpaid
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeCycle
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: system_actor)
-  end
-
   describe "status column display" do
     test "shows status column in member list", %{conn: conn} do
       fee_type = create_fee_type(%{interval: :yearly})
       member = create_member(%{membership_fee_type_id: fee_type.id})
-      create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :paid})
+
+      create_cycle(member, fee_type, %{
+        cycle_start: ~D[2023-01-01],
+        status: :paid,
+        replace_existing: true
+      })
 
       {:ok, _view, html} = live(conn, "/members")
 
@@ -85,8 +46,18 @@ defmodule MvWeb.MemberLive.IndexMembershipFeeStatusTest do
     test "shows last completed cycle status by default", %{conn: conn} do
       fee_type = create_fee_type(%{interval: :yearly})
       member = create_member(%{membership_fee_type_id: fee_type.id})
-      create_cycle(member, fee_type, %{cycle_start: ~D[2022-01-01], status: :paid})
-      create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :unpaid})
+
+      create_cycle(member, fee_type, %{
+        cycle_start: ~D[2022-01-01],
+        status: :paid,
+        replace_existing: true
+      })
+
+      create_cycle(member, fee_type, %{
+        cycle_start: ~D[2023-01-01],
+        status: :unpaid,
+        replace_existing: true
+      })
 
       {:ok, view, _html} = live(conn, "/members")
 
@@ -102,8 +73,17 @@ defmodule MvWeb.MemberLive.IndexMembershipFeeStatusTest do
       today = Date.utc_today()
       current_year_start = %{today | month: 1, day: 1}
 
-      create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :paid})
-      create_cycle(member, fee_type, %{cycle_start: current_year_start, status: :suspended})
+      create_cycle(member, fee_type, %{
+        cycle_start: ~D[2023-01-01],
+        status: :paid,
+        replace_existing: true
+      })
+
+      create_cycle(member, fee_type, %{
+        cycle_start: current_year_start,
+        status: :suspended,
+        replace_existing: true
+      })
 
       {:ok, view, _html} = live(conn, "/members")
 
@@ -120,7 +100,12 @@ defmodule MvWeb.MemberLive.IndexMembershipFeeStatusTest do
     test "shows correct color coding for paid status", %{conn: conn} do
       fee_type = create_fee_type(%{interval: :yearly})
       member = create_member(%{membership_fee_type_id: fee_type.id})
-      create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :paid})
+
+      create_cycle(member, fee_type, %{
+        cycle_start: ~D[2023-01-01],
+        status: :paid,
+        replace_existing: true
+      })
 
       {:ok, view, _html} = live(conn, "/members")
 
@@ -131,7 +116,12 @@ defmodule MvWeb.MemberLive.IndexMembershipFeeStatusTest do
     test "shows correct color coding for unpaid status", %{conn: conn} do
       fee_type = create_fee_type(%{interval: :yearly})
       member = create_member(%{membership_fee_type_id: fee_type.id})
-      create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :unpaid})
+
+      create_cycle(member, fee_type, %{
+        cycle_start: ~D[2023-01-01],
+        status: :unpaid,
+        replace_existing: true
+      })
 
       {:ok, view, _html} = live(conn, "/members")
 
@@ -142,7 +132,12 @@ defmodule MvWeb.MemberLive.IndexMembershipFeeStatusTest do
     test "shows correct color coding for suspended status", %{conn: conn} do
       fee_type = create_fee_type(%{interval: :yearly})
       member = create_member(%{membership_fee_type_id: fee_type.id})
-      create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :suspended})
+
+      create_cycle(member, fee_type, %{
+        cycle_start: ~D[2023-01-01],
+        status: :suspended,
+        replace_existing: true
+      })
 
       {:ok, view, _html} = live(conn, "/members")
 
@@ -169,11 +164,21 @@ defmodule MvWeb.MemberLive.IndexMembershipFeeStatusTest do
 
       # Member with unpaid last cycle
       member1 = create_member(%{first_name: "UnpaidMember", membership_fee_type_id: fee_type.id})
-      create_cycle(member1, fee_type, %{cycle_start: ~D[2023-01-01], status: :unpaid})
+
+      create_cycle(member1, fee_type, %{
+        cycle_start: ~D[2023-01-01],
+        status: :unpaid,
+        replace_existing: true
+      })
 
       # Member with paid last cycle
       member2 = create_member(%{first_name: "PaidMember", membership_fee_type_id: fee_type.id})
-      create_cycle(member2, fee_type, %{cycle_start: ~D[2023-01-01], status: :paid})
+
+      create_cycle(member2, fee_type, %{
+        cycle_start: ~D[2023-01-01],
+        status: :paid,
+        replace_existing: true
+      })
 
       system_actor = Mv.Helpers.SystemActor.get_system_actor()
 
@@ -205,11 +210,21 @@ defmodule MvWeb.MemberLive.IndexMembershipFeeStatusTest do
 
       # Member with unpaid current cycle
       member1 = create_member(%{first_name: "UnpaidCurrent", membership_fee_type_id: fee_type.id})
-      create_cycle(member1, fee_type, %{cycle_start: current_year_start, status: :unpaid})
+
+      create_cycle(member1, fee_type, %{
+        cycle_start: current_year_start,
+        status: :unpaid,
+        replace_existing: true
+      })
 
       # Member with paid current cycle
       member2 = create_member(%{first_name: "PaidCurrent", membership_fee_type_id: fee_type.id})
-      create_cycle(member2, fee_type, %{cycle_start: current_year_start, status: :paid})
+
+      create_cycle(member2, fee_type, %{
+        cycle_start: current_year_start,
+        status: :paid,
+        replace_existing: true
+      })
 
       system_actor = Mv.Helpers.SystemActor.get_system_actor()
 
@@ -243,7 +258,12 @@ defmodule MvWeb.MemberLive.IndexMembershipFeeStatusTest do
       # Create multiple members with cycles
       Enum.each(1..5, fn _ ->
         member = create_member(%{membership_fee_type_id: fee_type.id})
-        create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :paid})
+
+        create_cycle(member, fee_type, %{
+          cycle_start: ~D[2023-01-01],
+          status: :paid,
+          replace_existing: true
+        })
       end)
 
       {:ok, _view, html} = live(conn, "/members")
diff --git a/test/mv_web/member_live/index_test.exs b/test/mv_web/member_live/index_test.exs
index d664a5c..1985534 100644
--- a/test/mv_web/member_live/index_test.exs
+++ b/test/mv_web/member_live/index_test.exs
@@ -1,57 +1,18 @@
 defmodule MvWeb.MemberLive.IndexTest do
+  # async: false on purpose: the @slow "boolean filter performance with 150 members"
+  # test asserts a wall-clock budget (duration < 1000ms). Running this module in
+  # parallel with others adds CPU contention that inflates that measurement and makes
+  # the timing assertion flaky, so this module stays synchronous.
   use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
+  import Mv.Fixtures, only: [create_fee_type: 2, create_cycle: 4]
 
   alias Mv.Helpers.SystemActor
   alias Mv.Membership
   alias Mv.Membership.CustomField
   alias Mv.Membership.CustomFieldValue
-  alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
   alias MvWeb.MemberLive.Index, as: MemberIndex
 
-  require Ash.Query
-
-  # Helper to create a membership fee type (shared across all tests)
-  defp create_fee_type(attrs, actor) do
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
-  # Helper to create a cycle (shared across all tests)
-  defp create_cycle(member, fee_type, attrs, actor) do
-    # Delete any auto-generated cycles first to avoid conflicts
-    existing_cycles =
-      MembershipFeeCycle
-      |> Ash.Query.filter(member_id == ^member.id)
-      |> Ash.read!(actor: actor)
-
-    Enum.each(existing_cycles, fn cycle -> Ash.destroy!(cycle, actor: actor) end)
-
-    default_attrs = %{
-      cycle_start: ~D[2023-01-01],
-      amount: Decimal.new("50.00"),
-      member_id: member.id,
-      membership_fee_type_id: fee_type.id,
-      status: :unpaid
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeCycle
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: actor)
-  end
-
   describe "desktop layout: scroll container and sticky table header" do
     @describetag :ui
 
@@ -338,10 +299,14 @@ defmodule MvWeb.MemberLive.IndexTest do
 
     send(view.pid, {:search_changed, "Friedrich"})
 
-    state = :sys.get_state(view.pid)
-
-    assert state.socket.assigns.query == "Friedrich"
-    assert is_list(state.socket.assigns.members)
+    # Rationale: this exercises the handle_info(:search_changed) callback in isolation.
+    # The search box value is owned by SearchBarComponent (assign_new), and scope is
+    # recomputed on handle_params rather than this handle_info, so the updated :query
+    # and :members assigns have no faithful rendered proxy here. The assigns are
+    # asserted on internal state to preserve the original coverage of the callback.
+    assigns = :sys.get_state(view.pid).socket.assigns
+    assert assigns.query == "Friedrich"
+    assert is_list(assigns.members)
   end
 
   @tag :ui
@@ -434,6 +399,38 @@ defmodule MvWeb.MemberLive.IndexTest do
     |> LazyHTML.query(~s([data-testid="bulk-actions-scope-badge"]))
   end
 
+  # Opens the bulk-actions dropdown and returns the mailto link's BCC payload
+  # (everything after "mailto:?bcc="). This is the observable carrier of the
+  # recipient set / recipient_count, replacing direct socket-assign inspection.
+  defp mailto_bcc(view) do
+    view |> element(~s([data-testid="bulk-actions-button"])) |> render_click()
+
+    href =
+      render(view)
+      |> LazyHTML.from_fragment()
+      |> LazyHTML.query(~s([data-testid="bulk-actions-mailto"]))
+      |> LazyHTML.attribute("href")
+      |> List.first()
+
+    case href do
+      "mailto:?bcc=" <> bcc -> bcc
+      other -> other || ""
+    end
+  end
+
+  # Opens the member-filter dropdown so its boolean filter controls are rendered.
+  defp open_member_filter(view) do
+    view
+    |> element(~s(button[phx-click="toggle_dropdown"][aria-label="Filter members"]))
+    |> render_click()
+  end
+
+  # Returns the rendered HTML of the member-filter dropdown (with it open).
+  defp member_filter_html(view) do
+    open_member_filter(view)
+    render(view)
+  end
+
   describe "copy_emails feature" do
     setup do
       system_actor = SystemActor.get_system_actor()
@@ -569,15 +566,13 @@ defmodule MvWeb.MemberLive.IndexTest do
 
       # Select two members by sending the select_member event directly
       render_click(view, "select_member", %{"id" => member1.id})
-      render_click(view, "select_member", %{"id" => member2.id})
+      html = render_click(view, "select_member", %{"id" => member2.id})
 
-      # Get the socket state to verify the formatted email string
-      state = :sys.get_state(view.pid)
-      selected_members = state.socket.assigns.selected_members
-
-      # Verify MapSet is used
-      assert %MapSet{} = selected_members
-      assert MapSet.size(selected_members) == 2
+      # Both selected members are observably reflected: their row checkboxes are
+      # checked and the scope badge shows the selection count ("2").
+      assert has_element?(view, ~s(input[role="checkbox"][name="#{member1.id}"][checked]))
+      assert has_element?(view, ~s(input[role="checkbox"][name="#{member2.id}"][checked]))
+      assert scope_badge(html) |> LazyHTML.text() |> String.trim() == "2"
     end
 
     test "email format is 'First Last <email>' with comma separator", %{
@@ -1010,26 +1005,23 @@ defmodule MvWeb.MemberLive.IndexTest do
 
     test "scope is :all when nothing selected and no filter", %{conn: conn} do
       conn = conn_with_oidc_user(conn)
-      {:ok, view, _html} = live(conn, "/members")
+      {:ok, _view, html} = live(conn, "/members")
 
-      assigns = :sys.get_state(view.pid).socket.assigns
-      assert assigns.scope == :all
+      # :all scope renders the muted "all" badge.
+      assert scope_badge(html) |> LazyHTML.text() |> String.trim() == "all"
     end
 
     test "scope is :filtered when a search term is active", %{conn: conn} do
       conn = conn_with_oidc_user(conn)
-      {:ok, view, _html} = live(conn, "/members?query=Scope")
+      {:ok, _view, html} = live(conn, "/members?query=Scope")
 
-      assigns = :sys.get_state(view.pid).socket.assigns
-      assert assigns.scope == :filtered
+      # An active search narrows the list, so the scope badge reads "filtered".
+      assert scope_badge(html) |> LazyHTML.text() |> String.trim() == "filtered"
     end
 
     test "scope is :filtered when a non-search filter is active", %{conn: conn} do
       conn = conn_with_oidc_user(conn)
-      {:ok, view, html} = live(conn, "/members?cycle_status_filter=paid")
-
-      assigns = :sys.get_state(view.pid).socket.assigns
-      assert assigns.scope == :filtered
+      {:ok, _view, html} = live(conn, "/members?cycle_status_filter=paid")
 
       badge = scope_badge(html)
       assert badge |> LazyHTML.text() |> String.trim() == "filtered"
@@ -1042,10 +1034,13 @@ defmodule MvWeb.MemberLive.IndexTest do
       conn = conn_with_oidc_user(conn)
       {:ok, view, _html} = live(conn, "/members")
 
-      render_click(view, "select_member", %{"id" => member1.id})
+      html = render_click(view, "select_member", %{"id" => member1.id})
 
-      assigns = :sys.get_state(view.pid).socket.assigns
-      assert assigns.scope == :selection
+      # A selection switches the badge to the emphasized (primary) variant whose
+      # label is the selected count ("1"), which is the observable proxy for scope == :selection.
+      badge = scope_badge(html)
+      assert badge |> LazyHTML.text() |> String.trim() == "1"
+      assert badge |> LazyHTML.attribute("class") |> List.first() =~ "badge-primary"
     end
 
     test "with no selection, recipient_count and mailto_bcc cover all members", %{
@@ -1054,11 +1049,11 @@ defmodule MvWeb.MemberLive.IndexTest do
       conn = conn_with_oidc_user(conn)
       {:ok, view, _html} = live(conn, "/members")
 
-      assigns = :sys.get_state(view.pid).socket.assigns
+      # The mailto link's BCC is the observable carrier of recipient_count/mailto_bcc.
+      bcc = mailto_bcc(view)
       # Both seeded members have an email, so the no-selection scope covers both.
-      assert assigns.recipient_count == 2
-      assert assigns.mailto_bcc =~ "scope1%40example.com"
-      assert assigns.mailto_bcc =~ "scope2%40example.com"
+      assert bcc =~ "scope1%40example.com"
+      assert bcc =~ "scope2%40example.com"
     end
 
     test "with a selection, recipient_count and mailto_bcc cover only the selection", %{
@@ -1070,10 +1065,9 @@ defmodule MvWeb.MemberLive.IndexTest do
 
       render_click(view, "select_member", %{"id" => member1.id})
 
-      assigns = :sys.get_state(view.pid).socket.assigns
-      assert assigns.recipient_count == 1
-      assert assigns.mailto_bcc =~ "scope1%40example.com"
-      refute assigns.mailto_bcc =~ "scope2%40example.com"
+      bcc = mailto_bcc(view)
+      assert bcc =~ "scope1%40example.com"
+      refute bcc =~ "scope2%40example.com"
     end
   end
 
@@ -1111,7 +1105,7 @@ defmodule MvWeb.MemberLive.IndexTest do
       create_cycle(
         paid_member,
         fee_type,
-        %{cycle_start: last_year_start, status: :paid},
+        %{cycle_start: last_year_start, status: :paid, replace_existing: true},
         system_actor
       )
 
@@ -1128,7 +1122,7 @@ defmodule MvWeb.MemberLive.IndexTest do
       create_cycle(
         unpaid_member,
         fee_type,
-        %{cycle_start: last_year_start, status: :unpaid},
+        %{cycle_start: last_year_start, status: :unpaid, replace_existing: true},
         system_actor
       )
 
@@ -1158,7 +1152,7 @@ defmodule MvWeb.MemberLive.IndexTest do
       create_cycle(
         paid_member,
         fee_type,
-        %{cycle_start: last_year_start, status: :paid},
+        %{cycle_start: last_year_start, status: :paid, replace_existing: true},
         system_actor
       )
 
@@ -1175,7 +1169,7 @@ defmodule MvWeb.MemberLive.IndexTest do
       create_cycle(
         unpaid_member,
         fee_type,
-        %{cycle_start: last_year_start, status: :unpaid},
+        %{cycle_start: last_year_start, status: :unpaid, replace_existing: true},
         system_actor
       )
 
@@ -1205,7 +1199,7 @@ defmodule MvWeb.MemberLive.IndexTest do
       create_cycle(
         paid_member,
         fee_type,
-        %{cycle_start: current_year_start, status: :paid},
+        %{cycle_start: current_year_start, status: :paid, replace_existing: true},
         system_actor
       )
 
@@ -1222,7 +1216,7 @@ defmodule MvWeb.MemberLive.IndexTest do
       create_cycle(
         unpaid_member,
         fee_type,
-        %{cycle_start: current_year_start, status: :unpaid},
+        %{cycle_start: current_year_start, status: :unpaid, replace_existing: true},
         system_actor
       )
 
@@ -1252,7 +1246,7 @@ defmodule MvWeb.MemberLive.IndexTest do
       create_cycle(
         paid_member,
         fee_type,
-        %{cycle_start: current_year_start, status: :paid},
+        %{cycle_start: current_year_start, status: :paid, replace_existing: true},
         system_actor
       )
 
@@ -1269,7 +1263,7 @@ defmodule MvWeb.MemberLive.IndexTest do
       create_cycle(
         unpaid_member,
         fee_type,
-        %{cycle_start: current_year_start, status: :unpaid},
+        %{cycle_start: current_year_start, status: :unpaid, replace_existing: true},
         system_actor
       )
 
@@ -1339,6 +1333,9 @@ defmodule MvWeb.MemberLive.IndexTest do
       conn = conn_with_oidc_user(conn)
       {:ok, view, _html} = live(conn, "/members")
 
+      # Rationale: with no boolean fields and no active filter there is no rendered
+      # filter control or active-count badge to observe, so the empty initial filter
+      # map is asserted on internal state directly.
       state = :sys.get_state(view.pid)
       assert state.socket.assigns.boolean_custom_field_filters == %{}
     end
@@ -1350,6 +1347,9 @@ defmodule MvWeb.MemberLive.IndexTest do
       conn = conn_with_oidc_user(conn)
       {:ok, view, _html} = live(conn, "/members")
 
+      # Rationale: the absence of boolean fields means the filter dropdown renders
+      # no boolean fieldsets; "empty list" has no positive rendered signal, so it is
+      # asserted on internal state directly.
       state = :sys.get_state(view.pid)
       assert state.socket.assigns.boolean_custom_fields == []
     end
@@ -1360,89 +1360,82 @@ defmodule MvWeb.MemberLive.IndexTest do
       # Create boolean and non-boolean custom fields
       boolean_field1 = create_boolean_custom_field(%{name: "Active Member"})
       boolean_field2 = create_boolean_custom_field(%{name: "Newsletter Subscription"})
-      _string_field = create_string_custom_field(%{name: "Phone Number"})
+      string_field = create_string_custom_field(%{name: "Phone Number"})
 
       {:ok, view, _html} = live(conn, "/members")
+      open_member_filter(view)
 
-      state = :sys.get_state(view.pid)
-      boolean_custom_fields = state.socket.assigns.boolean_custom_fields
-
-      # Should only contain boolean fields
-      assert length(boolean_custom_fields) == 2
-      assert Enum.all?(boolean_custom_fields, &(&1.value_type == :boolean))
-      assert Enum.any?(boolean_custom_fields, &(&1.id == boolean_field1.id))
-      assert Enum.any?(boolean_custom_fields, &(&1.id == boolean_field2.id))
+      # Only the boolean fields render a tri-state filter control; the string field does not.
+      assert has_element?(view, "##{"custom-boolean-filter-#{boolean_field1.id}-all"}")
+      assert has_element?(view, "##{"custom-boolean-filter-#{boolean_field2.id}-all"}")
+      refute has_element?(view, "##{"custom-boolean-filter-#{string_field.id}-all"}")
     end
 
     test "mount sorts boolean custom fields by name ascending", %{conn: conn} do
       conn = conn_with_oidc_user(conn)
 
       # Create boolean fields with specific names to test sorting
-      _boolean_field_z = create_boolean_custom_field(%{name: "Zebra Field"})
-      _boolean_field_a = create_boolean_custom_field(%{name: "Alpha Field"})
-      _boolean_field_m = create_boolean_custom_field(%{name: "Middle Field"})
+      field_z = create_boolean_custom_field(%{name: "Zebra Field"})
+      field_a = create_boolean_custom_field(%{name: "Alpha Field"})
+      field_m = create_boolean_custom_field(%{name: "Middle Field"})
 
       {:ok, view, _html} = live(conn, "/members")
+      html = member_filter_html(view)
 
-      state = :sys.get_state(view.pid)
-      boolean_custom_fields = state.socket.assigns.boolean_custom_fields
+      # The rendered boolean filter controls appear in name-ascending order.
+      rendered_order =
+        html
+        |> LazyHTML.from_fragment()
+        |> LazyHTML.query(~s(input[id$="-all"][name^="custom_boolean"]))
+        |> LazyHTML.attribute("id")
+        |> Enum.map(
+          &(&1
+            |> String.replace_prefix("custom-boolean-filter-", "")
+            |> String.replace_suffix("-all", ""))
+        )
 
-      # Should be sorted by name ascending
-      names = Enum.map(boolean_custom_fields, & &1.name)
-      assert names == ["Alpha Field", "Middle Field", "Zebra Field"]
+      assert rendered_order == [field_a.id, field_m.id, field_z.id]
     end
 
     test "handle_params parses bf_<id> values correctly", %{conn: conn} do
       conn = conn_with_oidc_user(conn)
       boolean_field = create_boolean_custom_field()
 
-      # Test true value
-      {:ok, view1, _html} =
-        live(conn, "/members?bf_#{boolean_field.id}=true")
+      # Test true value: the "Yes" radio is checked (the boolean true, not the string "true").
+      {:ok, view1, _html} = live(conn, "/members?bf_#{boolean_field.id}=true")
+      open_member_filter(view1)
+      assert has_element?(view1, "##{"custom-boolean-filter-#{boolean_field.id}-true"}[checked]")
+      refute has_element?(view1, "##{"custom-boolean-filter-#{boolean_field.id}-all"}[checked]")
 
-      state1 = :sys.get_state(view1.pid)
-      filters1 = state1.socket.assigns.boolean_custom_field_filters
-      assert filters1[boolean_field.id] == true
-      refute filters1[boolean_field.id] == "true"
-
-      # Test false value
-      {:ok, view2, _html} =
-        live(conn, "/members?bf_#{boolean_field.id}=false")
-
-      state2 = :sys.get_state(view2.pid)
-      filters2 = state2.socket.assigns.boolean_custom_field_filters
-      assert filters2[boolean_field.id] == false
-      refute filters2[boolean_field.id] == "false"
+      # Test false value: the "No" radio is checked.
+      {:ok, view2, _html} = live(conn, "/members?bf_#{boolean_field.id}=false")
+      open_member_filter(view2)
+      assert has_element?(view2, "##{"custom-boolean-filter-#{boolean_field.id}-false"}[checked]")
+      refute has_element?(view2, "##{"custom-boolean-filter-#{boolean_field.id}-all"}[checked]")
     end
 
     test "handle_params ignores non-existent custom field IDs", %{conn: conn} do
       conn = conn_with_oidc_user(conn)
       fake_id = Ecto.UUID.generate()
 
-      {:ok, view, _html} =
-        live(conn, "/members?bf_#{fake_id}=true")
+      {:ok, view, _html} = live(conn, "/members?bf_#{fake_id}=true")
+      open_member_filter(view)
 
-      state = :sys.get_state(view.pid)
-      filters = state.socket.assigns.boolean_custom_field_filters
-
-      # Filter should not be added for non-existent custom field
-      refute Map.has_key?(filters, fake_id)
-      assert filters == %{}
+      # No filter control exists for a non-existent field, and no active-filter badge appears.
+      refute has_element?(view, "##{"custom-boolean-filter-#{fake_id}-true"}")
+      refute has_element?(view, ~s(button[aria-label="Filter members"].btn-active))
     end
 
     test "handle_params ignores non-boolean custom fields", %{conn: conn} do
       conn = conn_with_oidc_user(conn)
       string_field = create_string_custom_field()
 
-      {:ok, view, _html} =
-        live(conn, "/members?bf_#{string_field.id}=true")
+      {:ok, view, _html} = live(conn, "/members?bf_#{string_field.id}=true")
+      open_member_filter(view)
 
-      state = :sys.get_state(view.pid)
-      filters = state.socket.assigns.boolean_custom_field_filters
-
-      # Filter should not be added for non-boolean custom field
-      refute Map.has_key?(filters, string_field.id)
-      assert filters == %{}
+      # A string field is never rendered as a boolean filter, and no filter becomes active.
+      refute has_element?(view, "##{"custom-boolean-filter-#{string_field.id}-true"}")
+      refute has_element?(view, ~s(button[aria-label="Filter members"].btn-active))
     end
 
     test "handle_params ignores invalid filter values", %{conn: conn} do
@@ -1453,15 +1446,12 @@ defmodule MvWeb.MemberLive.IndexTest do
       invalid_values = ["1", "0", "yes", "no", "True", "False", "", "invalid", "null"]
 
       for invalid_value <- invalid_values do
-        {:ok, view, _html} =
-          live(conn, "/members?bf_#{boolean_field.id}=#{invalid_value}")
+        {:ok, view, _html} = live(conn, "/members?bf_#{boolean_field.id}=#{invalid_value}")
+        open_member_filter(view)
 
-        state = :sys.get_state(view.pid)
-        filters = state.socket.assigns.boolean_custom_field_filters
-
-        # Invalid values should not be added to filters
-        refute Map.has_key?(filters, boolean_field.id),
-               "Invalid value '#{invalid_value}' should not be added to filters"
+        # An invalid value leaves the field's filter at "All" (no filter applied).
+        assert has_element?(view, "##{"custom-boolean-filter-#{boolean_field.id}-all"}[checked]"),
+               "Invalid value '#{invalid_value}' should leave the filter at All"
       end
     end
 
@@ -1476,12 +1466,16 @@ defmodule MvWeb.MemberLive.IndexTest do
           "/members?bf_#{boolean_field1.id}=true&bf_#{boolean_field2.id}=false"
         )
 
-      state = :sys.get_state(view.pid)
-      filters = state.socket.assigns.boolean_custom_field_filters
+      open_member_filter(view)
 
-      assert filters[boolean_field1.id] == true
-      assert filters[boolean_field2.id] == false
-      assert map_size(filters) == 2
+      # Both filters are reflected: field1 at "Yes", field2 at "No", and the
+      # active-filter count badge shows 2.
+      assert has_element?(view, "##{"custom-boolean-filter-#{boolean_field1.id}-true"}[checked]")
+      assert has_element?(view, "##{"custom-boolean-filter-#{boolean_field2.id}-false"}[checked]")
+
+      assert view
+             |> element(~s(button[aria-label="Filter members"] .badge), "2")
+             |> has_element?()
     end
 
     test "build_query_params includes active boolean filters and excludes nil filters", %{
@@ -1555,12 +1549,12 @@ defmodule MvWeb.MemberLive.IndexTest do
           "/members?cycle_status_filter=paid&bf_#{boolean_field.id}=true"
         )
 
-      state = :sys.get_state(view.pid)
-      filters = state.socket.assigns.boolean_custom_field_filters
+      open_member_filter(view)
 
-      # Both filters should be set
-      assert filters[boolean_field.id] == true
-      assert state.socket.assigns.cycle_status_filter == :paid
+      # Both filters are reflected in the rendered controls: the boolean field at
+      # "Yes" and the payment-status filter at "paid".
+      assert has_element?(view, "##{"custom-boolean-filter-#{boolean_field.id}-true"}[checked]")
+      assert has_element?(view, "#payment-filter-paid[checked]")
 
       # Both should be in URL when triggering search
       view
@@ -1581,9 +1575,8 @@ defmodule MvWeb.MemberLive.IndexTest do
       {:ok, view, _html} =
         live(conn, "/members?bf_#{boolean_field.id}=true")
 
-      state_before = :sys.get_state(view.pid)
-      filters_before = state_before.socket.assigns.boolean_custom_field_filters
-      assert filters_before[boolean_field.id] == true
+      open_member_filter(view)
+      assert has_element?(view, "##{"custom-boolean-filter-#{boolean_field.id}-true"}[checked]")
 
       # Delete the custom field (requires actor with destroy permission)
       Ash.destroy!(boolean_field, actor: system_actor)
@@ -1592,12 +1585,11 @@ defmodule MvWeb.MemberLive.IndexTest do
       {:ok, view2, _html} =
         live(conn, "/members?bf_#{boolean_field.id}=true")
 
-      state_after = :sys.get_state(view2.pid)
-      filters_after = state_after.socket.assigns.boolean_custom_field_filters
+      open_member_filter(view2)
 
-      # Filter should not be present for deleted custom field
-      refute Map.has_key?(filters_after, boolean_field.id)
-      assert filters_after == %{}
+      # The deleted field renders no filter control and no filter is active.
+      refute has_element?(view2, "##{"custom-boolean-filter-#{boolean_field.id}-true"}")
+      refute has_element?(view2, ~s(button[aria-label="Filter members"].btn-active))
     end
 
     test "handle_params handles URL-encoded custom field IDs correctly", %{conn: conn} do
@@ -1610,12 +1602,11 @@ defmodule MvWeb.MemberLive.IndexTest do
       {:ok, view, _html} =
         live(conn, "/members?bf_#{encoded_id}=true")
 
-      state = :sys.get_state(view.pid)
-      filters = state.socket.assigns.boolean_custom_field_filters
+      open_member_filter(view)
 
-      # Filter should work with URL-encoded ID
-      # Phoenix should decode it automatically, so we check with original ID
-      assert filters[boolean_field.id] == true
+      # Phoenix decodes the param, so the filter applies under the original ID:
+      # the "Yes" radio for the field is checked.
+      assert has_element?(view, "##{"custom-boolean-filter-#{boolean_field.id}-true"}[checked]")
     end
 
     test "handle_params ignores malformed prefix (bf_bf_<uuid>)", %{conn: conn} do
@@ -1626,12 +1617,12 @@ defmodule MvWeb.MemberLive.IndexTest do
       {:ok, view, _html} =
         live(conn, "/members?bf_bf_#{boolean_field.id}=true")
 
-      state = :sys.get_state(view.pid)
-      filters = state.socket.assigns.boolean_custom_field_filters
+      open_member_filter(view)
 
-      # Should not parse as valid filter (UUID validation should fail)
-      refute Map.has_key?(filters, boolean_field.id)
-      assert filters == %{}
+      # The double-prefixed param is not a valid filter: the field stays at "All"
+      # and no filter is active.
+      assert has_element?(view, "##{"custom-boolean-filter-#{boolean_field.id}-all"}[checked]")
+      refute has_element?(view, ~s(button[aria-label="Filter members"].btn-active))
     end
 
     test "handle_params limits number of boolean filters to prevent DoS", %{conn: conn} do
@@ -1646,17 +1637,11 @@ defmodule MvWeb.MemberLive.IndexTest do
 
       {:ok, view, _html} = live(conn, "/members?#{filter_params}")
 
-      state = :sys.get_state(view.pid)
-      filters = state.socket.assigns.boolean_custom_field_filters
-
-      # Should limit to maximum 50 filters
-      assert map_size(filters) <= 50
-      # All filters in the result should be valid
-      Enum.each(filters, fn {id, value} ->
-        assert value in [true, false]
-        # Verify the ID corresponds to one of our boolean fields
-        assert id in Enum.map(boolean_fields, &to_string(&1.id))
-      end)
+      # The active-filter count badge is the observable carrier of the filter count.
+      # With 60 requested filters, the DoS cap clamps it to exactly 50.
+      assert view
+             |> element(~s(button[aria-label="Filter members"] .badge), "50")
+             |> has_element?()
     end
 
     test "handle_params ignores extremely long custom field IDs", %{conn: conn} do
@@ -1669,14 +1654,12 @@ defmodule MvWeb.MemberLive.IndexTest do
       {:ok, view, _html} =
         live(conn, "/members?bf_#{fake_long_id}=true")
 
-      state = :sys.get_state(view.pid)
-      filters = state.socket.assigns.boolean_custom_field_filters
+      open_member_filter(view)
 
-      # Should not accept the extremely long ID
-      refute Map.has_key?(filters, fake_long_id)
-      # Valid boolean field should still work
-      refute Map.has_key?(filters, boolean_field.id)
-      assert filters == %{}
+      # The over-long ID is rejected: the real field stays at "All" and no filter
+      # is active.
+      assert has_element?(view, "##{"custom-boolean-filter-#{boolean_field.id}-all"}[checked]")
+      refute has_element?(view, ~s(button[aria-label="Filter members"].btn-active))
     end
 
     # Helper to create a member with a boolean custom field value
@@ -2197,7 +2180,7 @@ defmodule MvWeb.MemberLive.IndexTest do
       create_cycle(
         member_paid_true,
         fee_type,
-        %{cycle_start: last_year_start, status: :paid},
+        %{cycle_start: last_year_start, status: :paid, replace_existing: true},
         system_actor
       )
 
@@ -2225,7 +2208,7 @@ defmodule MvWeb.MemberLive.IndexTest do
       create_cycle(
         member_unpaid_true,
         fee_type,
-        %{cycle_start: last_year_start, status: :unpaid},
+        %{cycle_start: last_year_start, status: :unpaid, replace_existing: true},
         system_actor
       )
 
@@ -2324,24 +2307,20 @@ defmodule MvWeb.MemberLive.IndexTest do
 
       # Start with no boolean custom fields
       {:ok, view, _html} = live(conn, "/members")
+      open_member_filter(view)
 
-      state_before = :sys.get_state(view.pid)
-      boolean_fields_before = state_before.socket.assigns.boolean_custom_fields
-      assert boolean_fields_before == []
+      # No boolean field control is rendered yet.
+      refute has_element?(view, ~s(input[name^="custom_boolean"]))
 
       # Create a new boolean custom field
       new_boolean_field = create_boolean_custom_field(%{name: "Newly Added Field"})
 
-      # Navigate again - the new field should appear
+      # Navigate again - the new field should appear in the filter dropdown.
       {:ok, view2, _html} = live(conn, "/members")
+      html_after = member_filter_html(view2)
 
-      state_after = :sys.get_state(view2.pid)
-      boolean_fields_after = state_after.socket.assigns.boolean_custom_fields
-
-      # New boolean field should be present
-      assert length(boolean_fields_after) == 1
-      assert Enum.any?(boolean_fields_after, &(&1.id == new_boolean_field.id))
-      assert Enum.any?(boolean_fields_after, &(&1.name == "Newly Added Field"))
+      assert has_element?(view2, "##{"custom-boolean-filter-#{new_boolean_field.id}-all"}")
+      assert html_after =~ "Newly Added Field"
     end
 
     @tag :slow
diff --git a/test/mv_web/member_live/membership_fee_integration_test.exs b/test/mv_web/member_live/membership_fee_integration_test.exs
index ac60220..16f1064 100644
--- a/test/mv_web/member_live/membership_fee_integration_test.exs
+++ b/test/mv_web/member_live/membership_fee_integration_test.exs
@@ -5,29 +5,12 @@ defmodule MvWeb.MemberLive.MembershipFeeIntegrationTest do
   use MvWeb.ConnCase, async: false
 
   import Phoenix.LiveViewTest
+  import Mv.Fixtures, only: [create_fee_type: 1]
 
   alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
 
   require Ash.Query
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs) do
-    system_actor = Mv.Helpers.SystemActor.get_system_actor()
-
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: system_actor)
-  end
-
   # Helper to create a member
   defp create_member(attrs) do
     system_actor = Mv.Helpers.SystemActor.get_system_actor()
diff --git a/test/mv_web/member_live/show_groups_display_test.exs b/test/mv_web/member_live/show_groups_display_test.exs
index ea9cf52..a40ed2f 100644
--- a/test/mv_web/member_live/show_groups_display_test.exs
+++ b/test/mv_web/member_live/show_groups_display_test.exs
@@ -10,8 +10,10 @@ defmodule MvWeb.MemberLive.ShowGroupsDisplayTest do
   - Accessibility: group links have aria-label for screen readers
 
   ## Note on async
-  async: false to avoid PostgreSQL deadlocks when creating members and groups
-  in the same test run (same as IndexGroupsDisplayTest).
+  Kept async: false as a deferred scope decision. The deferrable-FK migration
+  removed the concurrent-create_member deadlock that previously forced this, so
+  re-flipping this members/groups suite to async is a possible follow-up rather
+  than part of the original change.
   """
   use MvWeb.ConnCase, async: false
   use Gettext, backend: MvWeb.Gettext
diff --git a/test/mv_web/member_live/show_membership_fees_test.exs b/test/mv_web/member_live/show_membership_fees_test.exs
index 394d743..9c1b73f 100644
--- a/test/mv_web/member_live/show_membership_fees_test.exs
+++ b/test/mv_web/member_live/show_membership_fees_test.exs
@@ -5,56 +5,12 @@ defmodule MvWeb.MemberLive.ShowMembershipFeesTest do
   use MvWeb.ConnCase, async: false
 
   import Phoenix.LiveViewTest
+  import Mv.Fixtures, only: [create_fee_type: 1, create_cycle: 3]
 
   alias Mv.MembershipFees.MembershipFeeCycle
-  alias Mv.MembershipFees.MembershipFeeType
 
   require Ash.Query
 
-  # Helper to create a membership fee type
-  defp create_fee_type(attrs) do
-    system_actor = Mv.Helpers.SystemActor.get_system_actor()
-
-    default_attrs = %{
-      name: "Test Fee Type #{System.unique_integer([:positive])}",
-      amount: Decimal.new("50.00"),
-      interval: :yearly
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeType
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: system_actor)
-  end
-
-  # Helper to create a cycle
-  defp create_cycle(member, fee_type, attrs) do
-    system_actor = Mv.Helpers.SystemActor.get_system_actor()
-
-    # Delete any auto-generated cycles first to avoid conflicts
-    existing_cycles =
-      MembershipFeeCycle
-      |> Ash.Query.filter(member_id == ^member.id)
-      |> Ash.read!(actor: system_actor)
-
-    Enum.each(existing_cycles, fn cycle -> Ash.destroy!(cycle, actor: system_actor) end)
-
-    default_attrs = %{
-      cycle_start: ~D[2023-01-01],
-      amount: Decimal.new("50.00"),
-      member_id: member.id,
-      membership_fee_type_id: fee_type.id,
-      status: :unpaid
-    }
-
-    attrs = Map.merge(default_attrs, attrs)
-
-    MembershipFeeCycle
-    |> Ash.Changeset.for_create(:create, attrs)
-    |> Ash.create!(actor: system_actor)
-  end
-
   describe "cycle-regeneration control tooltip (§3.5 icon/tooltip audit)" do
     test "the regenerate_cycles control carries a tooltip and accessible label", %{conn: conn} do
       fee_type = create_fee_type(%{interval: :yearly})
@@ -76,8 +32,19 @@ defmodule MvWeb.MemberLive.ShowMembershipFeesTest do
       fee_type = create_fee_type(%{interval: :yearly})
       member = Mv.Fixtures.member_fixture(%{membership_fee_type_id: fee_type.id})
 
-      _cycle1 = create_cycle(member, fee_type, %{cycle_start: ~D[2022-01-01], status: :paid})
-      _cycle2 = create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :unpaid})
+      _cycle1 =
+        create_cycle(member, fee_type, %{
+          cycle_start: ~D[2022-01-01],
+          status: :paid,
+          replace_existing: true
+        })
+
+      _cycle2 =
+        create_cycle(member, fee_type, %{
+          cycle_start: ~D[2023-01-01],
+          status: :unpaid,
+          replace_existing: true
+        })
 
       {:ok, view, _html} = live(conn, "/members/#{member.id}")
 
@@ -101,7 +68,8 @@ defmodule MvWeb.MemberLive.ShowMembershipFeesTest do
       create_cycle(member, fee_type, %{
         cycle_start: ~D[2023-01-01],
         amount: Decimal.new("60.00"),
-        status: :paid
+        status: :paid,
+        replace_existing: true
       })
 
       {:ok, view, _html} = live(conn, "/members/#{member.id}")
@@ -158,7 +126,12 @@ defmodule MvWeb.MemberLive.ShowMembershipFeesTest do
       fee_type = create_fee_type(%{interval: :yearly})
       member = Mv.Fixtures.member_fixture(%{membership_fee_type_id: fee_type.id})
 
-      cycle = create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :unpaid})
+      cycle =
+        create_cycle(member, fee_type, %{
+          cycle_start: ~D[2023-01-01],
+          status: :unpaid,
+          replace_existing: true
+        })
 
       {:ok, view, _html} = live(conn, "/members/#{member.id}")
 
@@ -189,7 +162,12 @@ defmodule MvWeb.MemberLive.ShowMembershipFeesTest do
       fee_type = create_fee_type(%{interval: :yearly})
       member = Mv.Fixtures.member_fixture(%{membership_fee_type_id: fee_type.id})
 
-      cycle = create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :unpaid})
+      cycle =
+        create_cycle(member, fee_type, %{
+          cycle_start: ~D[2023-01-01],
+          status: :unpaid,
+          replace_existing: true
+        })
 
       {:ok, view, _html} = live(conn, "/members/#{member.id}")
 
@@ -220,7 +198,12 @@ defmodule MvWeb.MemberLive.ShowMembershipFeesTest do
       fee_type = create_fee_type(%{interval: :yearly})
       member = Mv.Fixtures.member_fixture(%{membership_fee_type_id: fee_type.id})
 
-      cycle = create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :paid})
+      cycle =
+        create_cycle(member, fee_type, %{
+          cycle_start: ~D[2023-01-01],
+          status: :paid,
+          replace_existing: true
+        })
 
       {:ok, view, _html} = live(conn, "/members/#{member.id}")
 
@@ -316,7 +299,13 @@ defmodule MvWeb.MemberLive.ShowMembershipFeesTest do
          } do
       fee_type = create_fee_type(%{interval: :yearly})
       member = Mv.Fixtures.member_fixture(%{membership_fee_type_id: fee_type.id})
-      _cycle = create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :unpaid})
+
+      _cycle =
+        create_cycle(member, fee_type, %{
+          cycle_start: ~D[2023-01-01],
+          status: :unpaid,
+          replace_existing: true
+        })
 
       {:ok, view, _html} = live(conn, "/members/#{member.id}")
 
@@ -335,7 +324,13 @@ defmodule MvWeb.MemberLive.ShowMembershipFeesTest do
     } do
       fee_type = create_fee_type(%{interval: :yearly})
       member = Mv.Fixtures.member_fixture(%{membership_fee_type_id: fee_type.id})
-      cycle = create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :unpaid})
+
+      cycle =
+        create_cycle(member, fee_type, %{
+          cycle_start: ~D[2023-01-01],
+          status: :unpaid,
+          replace_existing: true
+        })
 
       {:ok, view, _html} = live(conn, "/members/#{member.id}")
 
@@ -361,7 +356,13 @@ defmodule MvWeb.MemberLive.ShowMembershipFeesTest do
       # This test verifies that Ash.destroy(cycle, actor: read_only_user) returns Forbidden.
       fee_type = create_fee_type(%{interval: :yearly})
       member = Mv.Fixtures.member_fixture(%{membership_fee_type_id: fee_type.id})
-      cycle = create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :unpaid})
+
+      cycle =
+        create_cycle(member, fee_type, %{
+          cycle_start: ~D[2023-01-01],
+          status: :unpaid,
+          replace_existing: true
+        })
 
       assert {:error, %Ash.Error.Forbidden{}} =
                Ash.destroy(cycle, domain: Mv.MembershipFees, actor: read_only_user)
@@ -389,8 +390,20 @@ defmodule MvWeb.MemberLive.ShowMembershipFeesTest do
 
       fee_type = create_fee_type(%{interval: :yearly})
       member = Mv.Fixtures.member_fixture(%{membership_fee_type_id: fee_type.id})
-      _c1 = create_cycle(member, fee_type, %{cycle_start: ~D[2022-01-01], status: :paid})
-      _c2 = create_cycle(member, fee_type, %{cycle_start: ~D[2023-01-01], status: :unpaid})
+
+      _c1 =
+        create_cycle(member, fee_type, %{
+          cycle_start: ~D[2022-01-01],
+          status: :paid,
+          replace_existing: true
+        })
+
+      _c2 =
+        create_cycle(member, fee_type, %{
+          cycle_start: ~D[2023-01-01],
+          status: :unpaid,
+          replace_existing: true
+        })
 
       {:ok, view, _html} = live(conn, "/members/#{member.id}")
 
diff --git a/test/mv_web/user_live/form_test.exs b/test/mv_web/user_live/form_test.exs
index a22c230..63649e4 100644
--- a/test/mv_web/user_live/form_test.exs
+++ b/test/mv_web/user_live/form_test.exs
@@ -1,5 +1,8 @@
 defmodule MvWeb.UserLive.FormTest do
-  # async: false to prevent PostgreSQL deadlocks when creating members and users
+  # Kept async: false as a deferred scope decision. The deferrable-FK migration
+  # removed the concurrent-create_member deadlock that previously forced this, so
+  # re-flipping this members/users suite to async is a possible follow-up rather
+  # than part of the original change.
   use MvWeb.ConnCase, async: false
   import Phoenix.LiveViewTest
 
diff --git a/test/seeds_test.exs b/test/seeds_test.exs
index c729dbb..2721d13 100644
--- a/test/seeds_test.exs
+++ b/test/seeds_test.exs
@@ -24,21 +24,11 @@ defmodule Mv.SeedsTest do
 
   require Ash.Query
 
-  # Module attribute to track if seeds have been run
-  # This allows us to run seeds once per test module while respecting sandbox isolation
-  @seeds_run_key :seeds_test_run
-
   setup do
     system_actor = Mv.Helpers.SystemActor.get_system_actor()
 
-    # Run seeds once per test process (due to sandbox isolation, each test runs in its own process)
-    # Process.get/put ensures seeds are only executed once per test process, not once per test
-    # Note: With async: false and sandbox isolation, this effectively runs seeds once per test,
-    # but the guard prevents multiple executions within the same test process if setup is called multiple times
-    unless Process.get(@seeds_run_key) do
-      Code.eval_file("priv/repo/seeds.exs")
-      Process.put(@seeds_run_key, true)
-    end
+    # Each test runs in its own sandbox-owned process, so seeds are loaded once per test.
+    Code.eval_file("priv/repo/seeds.exs")
 
     %{actor: system_actor}
   end
diff --git a/test/support/fixtures.ex b/test/support/fixtures.ex
index 73bf12a..e022600 100644
--- a/test/support/fixtures.ex
+++ b/test/support/fixtures.ex
@@ -335,4 +335,82 @@ defmodule Mv.Fixtures do
     {:ok, request} = Membership.confirm_join_request(token, actor: nil)
     request
   end
+
+  @doc """
+  Creates a membership fee type with default or custom attributes.
+
+  Defaults: a unique `name`, `amount` 50.00, `interval` :yearly.
+
+  ## Parameters
+    - `attrs` - Map of attributes to override defaults (e.g. `%{interval: :monthly}`).
+    - `actor` - the authorization actor; defaults to the system actor when omitted/nil.
+
+  ## Returns
+    - MembershipFeeType struct.
+
+  ## Examples
+
+      iex> create_fee_type(%{interval: :monthly})
+      %Mv.MembershipFees.MembershipFeeType{interval: :monthly, ...}
+
+      iex> create_fee_type(%{amount: Decimal.new("10.00")}, admin)
+      %Mv.MembershipFees.MembershipFeeType{...}
+  """
+  def create_fee_type(attrs \\ %{}, actor \\ nil) do
+    actor = actor || SystemActor.get_system_actor()
+
+    default_attrs = %{
+      name: "Test Fee Type #{System.unique_integer([:positive])}",
+      amount: Decimal.new("50.00"),
+      interval: :yearly
+    }
+
+    Mv.MembershipFees.MembershipFeeType
+    |> Ash.Changeset.for_create(:create, Map.merge(default_attrs, attrs))
+    |> Ash.create!(actor: actor)
+  end
+
+  @doc """
+  Creates a membership fee cycle for the given member and fee type.
+
+  Defaults: `cycle_start` ~D[2024-01-01], `amount` 50.00, `status` :unpaid,
+  with `member_id`/`membership_fee_type_id` derived from the passed structs.
+
+  ## Parameters
+    - `member` - the Member struct the cycle belongs to.
+    - `fee_type` - the MembershipFeeType struct the cycle references.
+    - `attrs` - Map overriding the cycle defaults (e.g. `%{cycle_start: ~D[2023-01-01], status: :paid}`).
+      A reserved `:replace_existing` key (truthy) deletes any pre-existing cycles for the member
+      before creating the new one (used where auto-generated cycles would otherwise conflict);
+      it is stripped from the attrs and never passed to the create action. Defaults to absent/false.
+    - `actor` - the authorization actor; defaults to the system actor when omitted/nil.
+
+  ## Returns
+    - MembershipFeeCycle struct.
+  """
+  def create_cycle(member, fee_type, attrs \\ %{}, actor \\ nil) do
+    actor = actor || SystemActor.get_system_actor()
+    {replace_existing, attrs} = Map.pop(attrs, :replace_existing, false)
+
+    if replace_existing do
+      require Ash.Query
+
+      Mv.MembershipFees.MembershipFeeCycle
+      |> Ash.Query.filter(member_id == ^member.id)
+      |> Ash.read!(actor: actor)
+      |> Enum.each(&Ash.destroy!(&1, actor: actor))
+    end
+
+    default_attrs = %{
+      cycle_start: ~D[2024-01-01],
+      amount: Decimal.new("50.00"),
+      member_id: member.id,
+      membership_fee_type_id: fee_type.id,
+      status: :unpaid
+    }
+
+    Mv.MembershipFees.MembershipFeeCycle
+    |> Ash.Changeset.for_create(:create, Map.merge(default_attrs, attrs))
+    |> Ash.create!(actor: actor)
+  end
 end