diff --git a/app/models/formations.py b/app/models/formations.py
index 55de77f7a0..3abbf38820 100644
--- a/app/models/formations.py
+++ b/app/models/formations.py
@@ -2,11 +2,12 @@
 """
 
 from app import db
+from app.comp import df_cache
 from app.models import SHORT_STR_LEN
 from app.scodoc import notesdb as ndb
-from app.scodoc import sco_utils as scu
+from app.scodoc import sco_cache
 from app.scodoc import sco_codes_parcours
-from app.comp import df_cache
+from app.scodoc import sco_utils as scu
 
 
 class Formation(db.Model):
@@ -76,6 +77,10 @@ class Formation(db.Model):
             df_cache.ModuleCoefsCache.set(key, modules_coefficients)
         return modules_coefficients
 
+    def has_locked_sems(self):
+        "True if there is a locked formsemestre in this formation"
+        return len(self.formsemestres.filter_by(etat=False).all()) > 0
+
     def invalidate_module_coefs(self, semestre_idx: int = None):
         """Invalide les coefficients de modules cachés.
         Si semestre_idx est None, invalide tous les semestres,
@@ -86,6 +91,36 @@ class Formation(db.Model):
         else:
             keys = f"{self.id}.{semestre_idx}"
         df_cache.ModuleCoefsCache.delete_many(keys | {f"{self.id}"})
+        sco_cache.invalidate_formsemestre()
+
+    def invalidate_cached_sems(self):
+        for sem in self.formsemestres:
+            sco_cache.invalidate_formsemestre(formsemestre_id=sem.id)
+
+    def force_semestre_modules_aux_ues(self) -> None:
+        """
+        Affecte à chaque module de cette formation le semestre de son UE de rattachement,
+        si elle en a une.
+        Devrait être appelé lorsqu'on change le type de formation vers le BUT, et aussi
+        lorsqu'on change le semestre d'une UE BUT.
+        Utile pour la migration des anciennes formations vers le BUT.
+        Invalide les caches coefs/poids.
+        """
+        if not self.is_apc():
+            return
+        change = False
+        for mod in self.modules:
+            if (
+                mod.ue.semestre_idx is not None
+                and mod.ue.semestre_idx > 0
+                and mod.semestre_id != mod.ue.semestre_idx
+            ):
+                mod.semestre_id = mod.ue.semestre_idx
+                db.session.add(mod)
+                change = True
+        db.session.commit()
+        if change:
+            self.invalidate_module_coefs()
 
 
 class Matiere(db.Model):
diff --git a/app/models/modules.py b/app/models/modules.py
index d1affad024..00a6d4c9ba 100644
--- a/app/models/modules.py
+++ b/app/models/modules.py
@@ -27,6 +27,7 @@ class Module(db.Model):
     formation_id = db.Column(db.Integer, db.ForeignKey("notes_formations.id"))
     matiere_id = db.Column(db.Integer, db.ForeignKey("notes_matieres.id"))
     # pas un id mais le numéro du semestre: 1, 2, ...
+    # note: en APC, le semestre qui fait autorité est celui de l'UE
     semestre_id = db.Column(db.Integer, nullable=False, default=1, server_default="1")
     numero = db.Column(db.Integer)  # ordre de présentation
     # id de l'element pedagogique Apogee correspondant:
diff --git a/app/scodoc/sco_edit_formation.py b/app/scodoc/sco_edit_formation.py
index a609a84182..f532758435 100644
--- a/app/scodoc/sco_edit_formation.py
+++ b/app/scodoc/sco_edit_formation.py
@@ -33,6 +33,7 @@ from flask import g, url_for, request
 
 from app import db
 from app import log
+from app.models.formations import Formation
 from app.models.modules import Module
 
 import app.scodoc.notesdb as ndb
@@ -301,17 +302,9 @@ def do_formation_edit(args):
 
     cnx = ndb.GetDBConnexion()
     sco_formations._formationEditor.edit(cnx, args)
-    invalidate_sems_in_formation(args["formation_id"])
-
-
-def invalidate_sems_in_formation(formation_id):
-    "Invalide les semestres utilisant cette formation"
-    for sem in sco_formsemestre.do_formsemestre_list(
-        args={"formation_id": formation_id}
-    ):
-        sco_cache.invalidate_formsemestre(
-            formsemestre_id=sem["formsemestre_id"]
-        )  # > formation modif.
+    formation = Formation.query.get(args["formation_id"])
+    formation.invalidate_cached_sems()
+    formation.force_semestre_modules_aux_ues()
 
 
 def objects_renumber(obj_list) -> None:
diff --git a/app/scodoc/sco_edit_matiere.py b/app/scodoc/sco_edit_matiere.py
index f07b9b588a..8e957ab8b4 100644
--- a/app/scodoc/sco_edit_matiere.py
+++ b/app/scodoc/sco_edit_matiere.py
@@ -34,6 +34,7 @@ from flask import g, url_for, request
 import app.scodoc.notesdb as ndb
 import app.scodoc.sco_utils as scu
 from app import log
+from app.models import Formation
 from app.scodoc.TrivialFormulator import TrivialFormulator, tf_error_message
 from app.scodoc.sco_exceptions import ScoValueError, ScoLockedFormError
 from app.scodoc import html_sco_header
@@ -66,7 +67,7 @@ def do_matiere_edit(*args, **kw):
     # edit
     _matiereEditor.edit(cnx, *args, **kw)
     formation_id = sco_edit_ue.ue_list({"ue_id": mat["ue_id"]})[0]["formation_id"]
-    sco_edit_formation.invalidate_sems_in_formation(formation_id)
+    Formation.query.get(formation_id).invalidate_cached_sems()
 
 
 def do_matiere_create(args):
diff --git a/app/scodoc/sco_edit_module.py b/app/scodoc/sco_edit_module.py
index 5e804b3244..24232164a7 100644
--- a/app/scodoc/sco_edit_module.py
+++ b/app/scodoc/sco_edit_module.py
@@ -39,6 +39,7 @@ import app.scodoc.sco_utils as scu
 from app.scodoc.sco_utils import ModuleType
 from app import log
 from app import models
+from app.models import Formation
 from app.scodoc.TrivialFormulator import TrivialFormulator
 from app.scodoc.sco_permissions import Permission
 from app.scodoc.sco_exceptions import ScoValueError, ScoLockedFormError, ScoGenError
@@ -411,7 +412,7 @@ def do_module_edit(val):
     # edit
     cnx = ndb.GetDBConnexion()
     _moduleEditor.edit(cnx, val)
-    sco_edit_formation.invalidate_sems_in_formation(mod["formation_id"])
+    Formation.query.get(mod["formation_id"]).invalidate_cached_sems()
 
 
 def check_module_code_unicity(code, field, formation_id, module_id=None):
diff --git a/app/scodoc/sco_edit_ue.py b/app/scodoc/sco_edit_ue.py
index 6e05fc4a99..cd5dcb7e3b 100644
--- a/app/scodoc/sco_edit_ue.py
+++ b/app/scodoc/sco_edit_ue.py
@@ -1155,9 +1155,11 @@ def do_ue_edit(args, bypass_lock=False, dont_invalidate_cache=False):
     cnx = ndb.GetDBConnexion()
     _ueEditor.edit(cnx, args)
 
+    formation = Formation.query.get(ue["formation_id"])
     if not dont_invalidate_cache:
         # Invalide les semestres utilisant cette formation:
-        sco_edit_formation.invalidate_sems_in_formation(ue["formation_id"])
+        formation.invalidate_cached_sems()
+    formation.force_semestre_modules_aux_ues()
 
 
 # essai edition en ligne:
diff --git a/app/scodoc/sco_formations.py b/app/scodoc/sco_formations.py
index 81dede6307..b2eaef9817 100644
--- a/app/scodoc/sco_formations.py
+++ b/app/scodoc/sco_formations.py
@@ -86,12 +86,10 @@ def formation_list(formation_id=None, args={}):
     return r
 
 
-def formation_has_locked_sems(formation_id):
-    "True if there is a locked formsemestre in this formation"
-    sems = sco_formsemestre.do_formsemestre_list(
-        args={"formation_id": formation_id, "etat": False}
-    )
-    return sems
+def formation_has_locked_sems(formation_id):  # XXX to remove
+    "backward compat: True if there is a locked formsemestre in this formation"
+    formation = Formation.query.get(formation_id)
+    return formation.has_locked_sems()
 
 
 def formation_export(
diff --git a/app/static/css/scodoc.css b/app/static/css/scodoc.css
index ac0751281a..4de3920925 100644
--- a/app/static/css/scodoc.css
+++ b/app/static/css/scodoc.css
@@ -1619,6 +1619,9 @@ li.module_malus span.formation_module_tit {
   text-decoration: underline;
 }
 
+span.formation_module_ue {
+  background-color: #b7d2fa;
+}
 span.notes_module_list_buts {
   margin-right: 5px;
 }
diff --git a/app/templates/pn/form_mods.html b/app/templates/pn/form_mods.html
index 045491f6e2..90faee024b 100644
--- a/app/templates/pn/form_mods.html
+++ b/app/templates/pn/form_mods.html
@@ -46,11 +46,13 @@
         </a>
         {% endif %}
 
+        (<span class="formation_module_ue"><a title="UE de rattachement">{{mod.ue.acronyme}}</a></span>),
         {{formation.get_parcours().SESSION_NAME}} {{mod.semestre_id}}
 
-        ({{mod.heures_cours|default("&nbsp;",true)|safe}}/{{mod.heures_td|default("&nbsp;",true)|safe}}/{{mod.heures_tp|default("&nbsp;",true)|safe}}, 
-        
-        Apo:<span class="{% if editable %}span_apo_edit{% endif %}"
+        {% if mod.heures_cours or mod.heures_td or mod.heures_tp %}
+            ({{mod.heures_cours|default("&nbsp;",true)|safe}}/{{mod.heures_td|default("&nbsp;",true)|safe}}/{{mod.heures_tp|default("&nbsp;",true)|safe}}, 
+        {% else %}
+        ({% endif %}Apo:<span class="{% if editable %}span_apo_edit{% endif %}"
         data-url="edit_module_set_code_apogee" 
         id="{{mod.id}}" 
         data-placeholder="{{scu.APO_MISSING_CODE_STR}}">
diff --git a/app/views/notes.py b/app/views/notes.py
index 9a8797e61c..8ec4702bb9 100644
--- a/app/views/notes.py
+++ b/app/views/notes.py
@@ -402,7 +402,8 @@ def ue_set_internal(ue_id):
     db.session.add(ue)
     db.session.commit()
     # Invalide les semestres de cette formation
-    sco_edit_formation.invalidate_sems_in_formation(ue.formation_id)
+    ue.formation.invalidate_cached_sems()
+
     return redirect(
         url_for(
             "notes.ue_table", scodoc_dept=g.scodoc_dept, formation_id=ue.formation_id
diff --git a/app/views/pn_modules.py b/app/views/pn_modules.py
index 0dc52d1bbd..c3b18f3556 100644
--- a/app/views/pn_modules.py
+++ b/app/views/pn_modules.py
@@ -144,7 +144,8 @@ def set_module_ue_coef():
         return scu.json_error(f"UE not found ({ue_id})", 404)
     module.set_ue_coef(ue, coef)
     db.session.commit()
-    sco_edit_formation.invalidate_sems_in_formation(module.formation_id)
+    module.formation.invalidate_cached_sems()
+
     return scu.json_error("ok", success=True, status=201)