diff --git a/app/workers/work_packages/automatic_mode/migrate_values_job.rb b/app/workers/work_packages/automatic_mode/migrate_values_job.rb
index 39293396afe6..0fee67054806 100644
--- a/app/workers/work_packages/automatic_mode/migrate_values_job.rb
+++ b/app/workers/work_packages/automatic_mode/migrate_values_job.rb
@@ -28,10 +28,8 @@
 
 class WorkPackages::AutomaticMode::MigrateValuesJob < ApplicationJob
   def perform
-    with_temporary_table do
-      change_scheduling_mode_to_manual
-      change_scheduling_mode_to_automatic_for_followers
-      change_scheduling_mode_to_automatic_for_parents
+    with_temporary_tables do
+      change_independent_childless_work_packages_scheduling_mode_to_manual
       set_lags_for_follows_relations
       copy_values_to_work_packages_and_update_journals
     end
@@ -39,16 +37,16 @@ def perform
 
   private
 
-  def with_temporary_table
+  def with_temporary_tables
     WorkPackage.transaction do
-      create_temporary_table
+      create_temporary_tables
       yield
     ensure
-      drop_temporary_table
+      drop_temporary_tables
     end
   end
 
-  def create_temporary_table
+  def create_temporary_tables
     execute(<<~SQL.squish)
       CREATE UNLOGGED TABLE temp_wp_values
       AS SELECT
@@ -58,42 +56,44 @@ def create_temporary_table
         schedule_manually
       FROM work_packages
     SQL
-  end
-
-  def drop_temporary_table
     execute(<<~SQL.squish)
-      DROP TABLE temp_wp_values
+      CREATE MATERIALIZED VIEW follows_relations
+      AS SELECT
+        relations.id as id,
+        relations.from_id as succ_id,
+        COALESCE(wp_pred.due_date, wp_pred.start_date) as pred_date,
+        COALESCE(wp_succ.start_date, wp_succ.due_date) as succ_date,
+        wp_succ.schedule_manually as succ_schedule_manually
+      FROM relations
+      LEFT JOIN work_packages wp_pred ON relations.to_id = wp_pred.id
+      LEFT JOIN work_packages wp_succ ON relations.from_id = wp_succ.id
+      WHERE relation_type = 'follows'
     SQL
+    execute("CREATE INDEX ON follows_relations (succ_id)")
   end
 
-  def change_scheduling_mode_to_manual
-    execute(<<~SQL.squish)
-      UPDATE temp_wp_values
-      SET schedule_manually = true
-    SQL
+  def drop_temporary_tables
+    execute("DROP TABLE temp_wp_values")
+    execute("DROP MATERIALIZED VIEW follows_relations")
   end
 
-  def change_scheduling_mode_to_automatic_for_followers
+  # Change the scheduling mode to manual for:
+  # - non-successor (independent) and non-parent (childless) work packages
+  # - successor work packages with dates but without any predecessor with dates
+  def change_independent_childless_work_packages_scheduling_mode_to_manual
     execute(<<~SQL.squish)
       UPDATE temp_wp_values
-      SET schedule_manually = false
-      WHERE EXISTS (
+      SET schedule_manually = true
+      WHERE NOT EXISTS (
+        SELECT 1
+        FROM follows_relations
+        WHERE follows_relations.succ_id = temp_wp_values.id
+          AND (follows_relations.pred_date IS NOT NULL
+               OR follows_relations.succ_date IS NULL)
+      ) AND NOT EXISTS (
         SELECT 1
-        FROM relations
-        WHERE relations.from_id = temp_wp_values.id
-          AND relations.relation_type = 'follows'
-      )
-    SQL
-  end
-
-  def change_scheduling_mode_to_automatic_for_parents
-    execute(<<~SQL.squish)
-      UPDATE temp_wp_values
-      SET schedule_manually = false
-      WHERE id IN (
-        SELECT DISTINCT parent_id
         FROM work_packages
-        WHERE parent_id IS NOT NULL
+        WHERE work_packages.parent_id = temp_wp_values.id
       )
     SQL
   end
@@ -109,32 +109,21 @@ def set_lags_for_follows_relations
     # - Use both information to count the number of working days between
     #   predecessor and successor dates and update the lag with it
     execute(<<~SQL.squish)
-      WITH follows_relations_with_dates AS (
-        SELECT
-          relations.id as id,
-          relations.from_id as succ_id,
-          COALESCE(wp_pred.due_date, wp_pred.start_date) as pred_date,
-          COALESCE(wp_succ.start_date, wp_succ.due_date) as succ_date
-        FROM relations
-        LEFT JOIN work_packages wp_pred ON relations.to_id = wp_pred.id
-        LEFT JOIN work_packages wp_succ ON relations.from_id = wp_succ.id
-        WHERE relation_type = 'follows'
-          AND COALESCE(wp_pred.due_date, wp_pred.start_date) IS NOT NULL
-          AND COALESCE(wp_succ.start_date, wp_succ.due_date) IS NOT NULL
-      ),
-      closest_follows_relations_with_dates AS (
+      WITH closest_follows_relations_with_dates AS (
         SELECT DISTINCT ON (succ_id)
           id,
           pred_date,
           succ_date
-        FROM follows_relations_with_dates
+        FROM follows_relations
+        WHERE pred_date IS NOT NULL
+          AND succ_date IS NOT NULL
         ORDER BY succ_id, pred_date DESC
       ),
       working_dates AS (
         SELECT date::date
         FROM generate_series(
-          (SELECT MIN(pred_date) FROM follows_relations_with_dates),
-          (SELECT MAX(succ_date) FROM follows_relations_with_dates),
+          (SELECT MIN(pred_date) FROM closest_follows_relations_with_dates),
+          (SELECT MAX(succ_date) FROM closest_follows_relations_with_dates),
           '1 day'::interval
         ) AS date
         WHERE EXTRACT(ISODOW FROM date)::integer IN (#{working_days.join(',')})
diff --git a/spec/migrations/update_scheduling_mode_and_lags_spec.rb b/spec/migrations/update_scheduling_mode_and_lags_spec.rb
index 0dcf3ae5209a..bab471f28052 100644
--- a/spec/migrations/update_scheduling_mode_and_lags_spec.rb
+++ b/spec/migrations/update_scheduling_mode_and_lags_spec.rb
@@ -94,8 +94,11 @@
     end
   end
 
-  # spec from #42388, "Migration from an earlier version" section
-  context "for work packages with no predecessors" do
+  # spec from #59539, "Migration from an earlier version" section:
+  #
+  # > - For work packages with no predecessors (or with no relations at all), they will be
+  # >   switched to manual scheduling.
+  context "for work packages with no predecessors nor children" do
     let_work_packages(<<~TABLE)
       subject        | start date | due date   | scheduling mode
       wp automatic 1 | 2024-11-20 | 2024-11-21 | automatic
@@ -115,43 +118,110 @@
     end
   end
 
-  # spec from #42388, "Migration from an earlier version" section
-  context "for work packages following another one" do
+  # spec from #59539, "Migration from an earlier version" section:
+  #
+  # > - Manually scheduled work packages remain so.
+  context "for manually scheduled work packages following another one" do
     let_work_packages(<<~TABLE)
       subject        | start date | due date   | scheduling mode | properties
-      main           | 2024-11-19 | 2024-11-19 | manual          |
-      wp automatic 1 | 2024-11-20 | 2024-11-21 | automatic       | follows main
-      wp automatic 2 |            | 2024-11-21 | automatic       | follows main
-      wp automatic 3 | 2024-11-20 |            | automatic       | follows main
-      wp automatic 4 |            |            | automatic       | follows main
-      wp manual 1    | 2024-11-20 | 2024-11-21 | manual          | follows main
-      wp manual 2    |            | 2024-11-21 | manual          | follows main
-      wp manual 3    | 2024-11-20 |            | manual          | follows main
-      wp manual 4    |            |            | manual          | follows main
+      main           |            |            | manual          |
+      wp 1           | 2024-11-20 | 2024-11-21 | manual          | follows main
+      wp 2           |            | 2024-11-21 | manual          | follows main
+      wp 3           | 2024-11-20 |            | manual          | follows main
+      wp 4           |            |            | manual          | follows main
+    TABLE
+
+    it "remains manually scheduled" do
+      run_migration
+
+      expect(table_work_packages).to all(be_schedule_manually)
+    end
+  end
+
+  # spec from #59539, "Migration from an earlier version" section
+  #
+  # > - If the successor is in automatic scheduling mode, has dates and some predecessors
+  # >   have dates too:
+  # >   - The successor remains in automatic mode
+  context "for automatically scheduled work packages following another one having dates" do
+    let_work_packages(<<~TABLE)
+      subject            | start date | due date   | scheduling mode | properties
+      pred with dates    | 2024-11-19 | 2024-11-19 | manual          |
+      pred without dates |            |            | manual          |
+      wp 1               | 2024-11-20 | 2024-11-21 | automatic       | follows pred with dates, follows pred without dates
+      wp 2               |            | 2024-11-21 | automatic       | follows pred with dates, follows pred without dates
+      wp 3               | 2024-11-20 |            | automatic       | follows pred with dates, follows pred without dates
+      wp 4               |            |            | automatic       | follows pred with dates, follows pred without dates
+    TABLE
+
+    it "remains automatically scheduled" do
+      run_migration
+
+      expect([wp1, wp2, wp3, wp4]).to all(be_schedule_automatically)
+    end
+  end
+
+  # spec from #59539, "Migration from an earlier version" section
+  # > - If the successor is in automatic scheduling mode and has no dates
+  # >   - The successor remains in automatic mode and continues to have no dates,
+  # >     regardless of having predecessor with dates or not.
+  # > - If the successor is in automatic scheduling mode, has dates and none of the
+  # >   predecessors have any dates
+  # >   - The successor is switched to manual mode to preserve its dates and duration
+  context "for automatically scheduled work packages without dates following another one" do
+    let_work_packages(<<~TABLE)
+      subject            | start date | due date   | scheduling mode | properties
+      pred without dates |            |            | manual          |
+      succ               |            |            | automatic       | follows pred without dates
+    TABLE
+
+    it "remains automatically scheduled and continues to have no dates" do
+      run_migration
+
+      expect(succ).to be_schedule_automatically
+    end
+  end
+
+  # spec from #59539, "Migration from an earlier version" section
+  #
+  # > - If the successor is in automatic scheduling mode, has dates and none of the
+  # >   predecessors have any dates
+  # >   - The successor is switched to manual mode to preserve its dates and duration
+  context "for automatically scheduled work packages following another one having no dates" do
+    let_work_packages(<<~TABLE)
+      subject            | start date | due date   | scheduling mode | properties
+      pred without dates |            |            | manual          |
+      succ 1             | 2024-11-20 | 2024-11-21 | automatic       | follows pred without dates
+      succ 2             |            | 2024-11-21 | automatic       | follows pred without dates
+      succ 3             | 2024-11-20 |            | automatic       | follows pred without dates
     TABLE
 
-    # TODO: should work packages without any dates really be switched to manual like the specs say?
-    it "switches to automatic scheduling" do
+    it "switches to manual scheduling to preserve its dates and duration" do
       run_migration
 
-      expect(main).to be_schedule_manually
-      expect(table_work_packages - [main]).to all(be_schedule_automatically)
+      expect([succ1, succ2, succ3]).to all(be_schedule_manually)
     end
   end
 
   # spec from #42388, "Migration from an earlier version" section
+  #
+  # > - Manually scheduled work packages remain so.
+  # > - If the relationship is parent-child, there are no changes to dates; the parent
+  # >   remains in automatic mode.
   context "for parent work packages" do
     let_work_packages(<<~TABLE)
-      hierarchy | scheduling mode |
-      parent    | manual          |
-        child   | manual          |
+      hierarchy        | scheduling mode |
+      parent_automatic | automatic       |
+        child1         | manual          |
+      parent_manual    | manual          |
+        child2         | manual          |
     TABLE
 
-    it "switches to automatic scheduling" do
+    it "keep their scheduling mode" do
       run_migration
 
-      expect(parent).to be_schedule_automatically
-      expect(child).to be_schedule_manually
+      expect(parent_automatic).to be_schedule_automatically
+      expect(parent_manual).to be_schedule_manually
     end
   end