diff --git a/app/components/dossiers/errors_full_messages_component.rb b/app/components/dossiers/errors_full_messages_component.rb
new file mode 100644
index 000000000..760cd3aa6
--- /dev/null
+++ b/app/components/dossiers/errors_full_messages_component.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+class Dossiers::ErrorsFullMessagesComponent < ApplicationComponent
+  ErrorDescriptor = Data.define(:anchor, :label, :error_message)
+
+  def initialize(dossier:, errors:)
+    @dossier = dossier
+    @errors = errors
+  end
+
+  def dedup_and_partitioned_errors
+    formated_errors = @errors.to_enum # ActiveModel::Errors.to_a is an alias to full_messages, we don't want that
+      .to_a # but enum.to_a gives back an array
+      .uniq { |error| [error.inner_error.base] } # dedup cumulated errors from dossier.champs, dossier.champs_public, dossier.champs_private which run the validator one time per association
+      .map { |error| to_error_descriptor(error.message, error.inner_error.base) }
+    yield(Array(formated_errors[0..2]), Array(formated_errors[3..]))
+  end
+
+  def to_error_descriptor(str_error, model)
+    ErrorDescriptor.new("##{model.labelledby_id}", model.libelle.truncate(200), str_error)
+  end
+
+  def render?
+    !@errors.empty?
+  end
+end
diff --git a/app/components/dossiers/errors_full_messages_component/errors_full_messages_component.en.yml b/app/components/dossiers/errors_full_messages_component/errors_full_messages_component.en.yml
new file mode 100644
index 000000000..3fab8164d
--- /dev/null
+++ b/app/components/dossiers/errors_full_messages_component/errors_full_messages_component.en.yml
@@ -0,0 +1,8 @@
+---
+en:
+  sumup_html:
+    one: |
+      Your file has 1 error. <a href="%{url}">Fix-it</a> to continue :
+    other: |
+      Your file has %{count} errors. <a href="%{url}">Fix-them</a> to continue :
+  see_more: Show all errors
diff --git a/app/components/dossiers/errors_full_messages_component/errors_full_messages_component.fr.yml b/app/components/dossiers/errors_full_messages_component/errors_full_messages_component.fr.yml
new file mode 100644
index 000000000..1fd0e7f8c
--- /dev/null
+++ b/app/components/dossiers/errors_full_messages_component/errors_full_messages_component.fr.yml
@@ -0,0 +1,8 @@
+---
+fr:
+  sumup_html:
+    one: |
+      Votre dossier contient 1 champ en erreur. <a href="%{url}">Corrigez-la</a> pour poursuivre :
+    other: |
+      Votre dossier contient  %{count} champs en erreurs. <a href="%{url}">Corrigez-les</a> pour poursuivre :
+  see_more: Afficher toutes les erreurs
diff --git a/app/components/dossiers/errors_full_messages_component/errors_full_messages_component.html.haml b/app/components/dossiers/errors_full_messages_component/errors_full_messages_component.html.haml
new file mode 100644
index 000000000..269286402
--- /dev/null
+++ b/app/components/dossiers/errors_full_messages_component/errors_full_messages_component.html.haml
@@ -0,0 +1,16 @@
+.fr-alert.fr-alert--error.fr-mb-3w{ role: "alertdialog" }
+  - dedup_and_partitioned_errors do |head, tail|
+    %p#sumup-errors= t('.sumup_html', count: head.size + tail.size, url: head.first.anchor)
+    %ul.fr-mb-0#head-errors
+      - head.each do |error_descriptor|
+        %li
+          = link_to error_descriptor.label, error_descriptor.anchor, class: 'error-anchor'
+          = error_descriptor.error_message
+    - if tail.size > 0
+      %button{ type: "button", "aria-controls": 'tail-errors', "aria-expanded": "false", class: "fr-btn fr-btn--sm fr-btn--tertiary-no-outline" }= t('.see_more')
+      %ul#tail-errors.fr-collapse.fr-mt-0
+        - tail.each do |error_descriptor|
+          %li
+            = link_to error_descriptor.label, error_descriptor.anchor, class: 'error-anchor'
+            = "(#{error_descriptor.error_message})"
+
diff --git a/app/controllers/users/dossiers_controller.rb b/app/controllers/users/dossiers_controller.rb
index 9debbec4e..5a77cd75e 100644
--- a/app/controllers/users/dossiers_controller.rb
+++ b/app/controllers/users/dossiers_controller.rb
@@ -207,9 +207,9 @@ module Users
 
     def submit_brouillon
       @dossier = dossier_with_champs(pj_template: false)
-      errors = submit_dossier_and_compute_errors
+      @errors = submit_dossier_and_compute_errors
 
-      if errors.blank?
+      if @errors.blank?
         @dossier.passer_en_construction!
         @dossier.process_declarative!
         @dossier.process_sva_svr!
@@ -218,8 +218,6 @@ module Users
         end
         redirect_to merci_dossier_path(@dossier)
       else
-        flash.now.alert = errors
-
         respond_to do |format|
           format.html { render :brouillon }
           format.turbo_stream
@@ -250,9 +248,9 @@ module Users
 
     def submit_en_construction
       @dossier = dossier_with_champs(pj_template: false)
-      errors = submit_dossier_and_compute_errors
+      @errors = submit_dossier_and_compute_errors
 
-      if errors.blank?
+      if @errors.blank?
         pending_correction_confirm = cast_bool(params.dig(:dossier, :pending_correction_confirm))
         editing_fork_origin = @dossier.editing_fork_origin
         editing_fork_origin.merge_fork(@dossier)
@@ -260,8 +258,6 @@ module Users
 
         redirect_to dossier_path(editing_fork_origin)
       else
-        flash.now.alert = errors
-
         respond_to do |format|
           format.html do
             @dossier = @dossier.editing_fork_origin
@@ -279,11 +275,7 @@ module Users
     def update
       @dossier = dossier.en_construction? ? dossier.find_editing_fork(dossier.user) : dossier
       @dossier = dossier_with_champs(pj_template: false)
-      errors = update_dossier_and_compute_errors
-
-      if errors.present?
-        flash.now.alert = errors
-      end
+      @errors = update_dossier_and_compute_errors
 
       respond_to do |format|
         format.turbo_stream do
@@ -531,46 +523,22 @@ module Users
       if @dossier.champs_public_all.any?(&:changed_for_autosave?)
         @dossier.last_champ_updated_at = Time.zone.now
       end
+
       if !@dossier.save(**validation_options)
-        errors += format_errors(errors: @dossier.errors)
+        errors = @dossier.errors
       end
 
       errors
     end
 
     def submit_dossier_and_compute_errors
-      errors = []
-
       @dossier.valid?(**submit_validation_options)
-      errors += format_errors(errors: @dossier.errors)
-      errors += format_errors(errors: @dossier.check_mandatory_and_visible_champs)
-      errors
-    end
 
-    def format_errors(errors:)
-      errors.map do |active_model_error|
-        case active_model_error.class.name
-        when "ActiveModel::NestedError"
-          append_anchor_link(active_model_error.full_message, active_model_error.inner_error.base)
-        when "ActiveModel::Error"
-          append_anchor_link(active_model_error.full_message, active_model_error.base)
-        else # "String"
-          active_model_error
-        end
+      errors = @dossier.errors
+      @dossier.check_mandatory_and_visible_champs.map do |error_on_champ|
+        errors.import(error_on_champ)
       end
-    end
-
-    def append_anchor_link(str_error, model)
-      return str_error.full_message if !model.is_a?(Champ)
-
-      route_helper = @dossier.editing_fork? ? :modifier_dossier_path : :brouillon_dossier_path
-
-      [
-        "Le champ « #{model.libelle.truncate(200)} » #{str_error}",
-        helpers.link_to(t('views.users.dossiers.fix_champ'), public_send(route_helper, anchor: model.labelledby_id), class: 'error-anchor')
-      ].join(", ")
-    rescue # case of invalid type de champ on champ
-      str_error
+      errors
     end
 
     def ensure_ownership!
diff --git a/app/models/champs/date_champ.rb b/app/models/champs/date_champ.rb
index 10fa8602c..d372eecea 100644
--- a/app/models/champs/date_champ.rb
+++ b/app/models/champs/date_champ.rb
@@ -29,7 +29,7 @@ class Champs::DateChamp < Champ
   def iso_8601
     return if parsable_iso8601? || value.blank?
     # i18n-tasks-use t('errors.messages.not_a_date')
-    errors.add :date, errors.generate_message(:value, :not_a_date)
+    errors.add :date, :not_a_date
   end
 
   def likely_iso8601_format?
diff --git a/app/models/champs/datetime_champ.rb b/app/models/champs/datetime_champ.rb
index 08a4c4719..fe1c2ecd7 100644
--- a/app/models/champs/datetime_champ.rb
+++ b/app/models/champs/datetime_champ.rb
@@ -40,7 +40,7 @@ class Champs::DatetimeChamp < Champ
   def iso_8601
     return if valid_iso8601? || value.blank?
     # i18n-tasks-use t('errors.messages.not_a_datetime')
-    errors.add :datetime, errors.generate_message(:value, :not_a_datetime)
+    errors.add :datetime, :not_a_datetime
   end
 
   def valid_iso8601?
diff --git a/app/models/dossier.rb b/app/models/dossier.rb
index 4c68a5fa6..17931f171 100644
--- a/app/models/dossier.rb
+++ b/app/models/dossier.rb
@@ -1148,7 +1148,7 @@ class Dossier < ApplicationRecord
       .filter(&:visible?)
       .filter(&:mandatory_blank?)
       .map do |champ|
-        champ.errors.add(:value, message: champ.errors.generate_message(:value, :missing))
+        champ.errors.add(:value, :missing)
       end
   end
 
diff --git a/app/validators/iban_validator.rb b/app/validators/iban_validator.rb
index 7c27a6daf..5c343005e 100644
--- a/app/validators/iban_validator.rb
+++ b/app/validators/iban_validator.rb
@@ -4,7 +4,7 @@ class IbanValidator < ActiveModel::Validator
   def validate(record)
     if record.value.present?
       unless IBANTools::IBAN.valid?(record.value)
-        record.errors.add :value, message: record.errors.generate_message(:value, :invalid_iban)
+        record.errors.add :value, :invalid_iban
       end
     end
   end
diff --git a/app/views/shared/dossiers/_edit.html.haml b/app/views/shared/dossiers/_edit.html.haml
index 0df412dfe..cac9e73d4 100644
--- a/app/views/shared/dossiers/_edit.html.haml
+++ b/app/views/shared/dossiers/_edit.html.haml
@@ -1,13 +1,17 @@
 - dossier_for_editing = dossier.en_construction? ? dossier.owner_editing_fork : dossier
 
+
 - if dossier.france_connect_information.present?
   - content_for(:notice_info) do
     = render partial: "shared/dossiers/france_connect_informations_notice", locals: { user_information: dossier.france_connect_information }
 
+
 .dossier-edit.container.counter-start-header-section
   = render partial: "shared/dossiers/submit_is_over", locals: { dossier: dossier }
   = render NestedForms::FormOwnerComponent.new
   = form_for dossier_for_editing, url: brouillon_dossier_url(dossier), method: :patch, html: { id: 'dossier-edit-form', class: 'form', multipart: true, novalidate: 'novalidate' } do |f|
+
+    = render Dossiers::ErrorsFullMessagesComponent.new(dossier: @dossier, errors: @errors || [])
     %header.mb-6
       .fr-highlight
         %p.fr-text--sm
diff --git a/config/locales/en.yml b/config/locales/en.yml
index cbbd64245..a199998ea 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -408,7 +408,6 @@ en:
         dossier_not_in_instructor_group: "File no. %{dossier_id} of the “%{procedure_libelle}” procedure corresponds to your search, but it is attached to the “%{groupe_instructeur_label}” instructor group."
     users:
       dossiers:
-        fix_champ: "fill in this field"
         archived_dossier: "Your file will be kept %{duree_conservation_dossiers_dans_ds} more months"
         identite:
           identity_data: Identity data
diff --git a/config/locales/fr.yml b/config/locales/fr.yml
index a8bb3d8cd..f0ec45337 100644
--- a/config/locales/fr.yml
+++ b/config/locales/fr.yml
@@ -410,7 +410,6 @@ fr:
         dossier_not_in_instructor_group: "Le dossier n° %{dossier_id} de la procédure « %{procedure_libelle} » correspond à votre recherche mais il est rattaché au groupe d’instructeurs « %{groupe_instructeur_label} »."
     users:
       dossiers:
-        fix_champ: "corriger l’erreur"
         archived_dossier: "Votre dossier sera conservé %{duree_conservation_dossiers_dans_ds} mois supplémentaire"
         identite:
           identity_data: Données d’identité
diff --git a/spec/controllers/users/dossiers_controller_spec.rb b/spec/controllers/users/dossiers_controller_spec.rb
index c85c9b477..754941ecc 100644
--- a/spec/controllers/users/dossiers_controller_spec.rb
+++ b/spec/controllers/users/dossiers_controller_spec.rb
@@ -370,10 +370,9 @@ describe Users::DossiersController, type: :controller do
 
   describe '#submit_brouillon' do
     before { sign_in(user) }
-
     let!(:dossier) { create(:dossier, user: user) }
     let(:first_champ) { dossier.champs_public.first }
-    let(:anchor_to_first_champ) { controller.helpers.link_to I18n.t('views.users.dossiers.fix_champ'), brouillon_dossier_path(anchor: first_champ.labelledby_id), class: 'error-anchor' }
+    let(:anchor_to_first_champ) { controller.helpers.link_to first_champ.libelle, brouillon_dossier_path(anchor: first_champ.labelledby_id), class: 'error-anchor' }
     let(:value) { 'beautiful value' }
     let(:now) { Time.zone.parse('01/01/2100') }
     let(:payload) { { id: dossier.id } }
@@ -409,16 +408,19 @@ describe Users::DossiersController, type: :controller do
     end
 
     context 'when the update fails' do
+      render_views
+      let(:error_message) { 'nop' }
       before do
         expect_any_instance_of(Dossier).to receive(:valid?).and_return(false)
         expect_any_instance_of(Dossier).to receive(:errors).and_return(
-          [double(class: ActiveModel::Error, full_message: 'nop', base: first_champ)]
+          [double(inner_error: double(base: first_champ), message: 'nop')]
         )
         subject
       end
 
       it { expect(response).to render_template(:brouillon) }
-      it { expect(flash.alert).to eq(["Le champ « #{first_champ.libelle} » nop, #{anchor_to_first_champ}"]) }
+      it { expect(response.body).to have_link(first_champ.libelle, href: "##{first_champ.labelledby_id}") }
+      it { expect(response.body).to have_content(error_message) }
 
       it 'does not send an email' do
         expect(NotificationMailer).not_to receive(:send_en_construction_notification)
@@ -428,6 +430,8 @@ describe Users::DossiersController, type: :controller do
     end
 
     context 'when a mandatory champ is missing' do
+      render_views
+
       let(:value) { nil }
 
       before do
@@ -436,7 +440,8 @@ describe Users::DossiersController, type: :controller do
       end
 
       it { expect(response).to render_template(:brouillon) }
-      it { expect(flash.alert).to eq(["Le champ « l » doit être rempli, #{anchor_to_first_champ}"]) }
+      it { expect(response.body).to have_link(first_champ.libelle, href: "##{first_champ.labelledby_id}") }
+      it { expect(response.body).to have_content("doit être rempli") }
     end
 
     context 'when dossier has no champ' do
@@ -515,27 +520,26 @@ describe Users::DossiersController, type: :controller do
       before do
         expect_any_instance_of(Dossier).to receive(:valid?).and_return(false)
         expect_any_instance_of(Dossier).to receive(:errors).and_return(
-          [double(class: ActiveModel::Error, full_message: 'nop', base: first_champ)]
+          [double(inner_error: double(base: first_champ), message: 'nop')]
         )
 
         subject
       end
 
       it { expect(response).to render_template(:modifier) }
-      it { expect(flash.alert).to eq(["Le champ « #{first_champ.libelle} » nop, #{anchor_to_first_champ}"]) }
-      it { expect(response.body).to include("Dossier nº #{dossier.id}") }
     end
 
     context 'when a mandatory champ is missing' do
       let(:value) { nil }
-
+      render_views
       before do
         first_champ.type_de_champ.update(mandatory: true, libelle: 'l')
         subject
       end
 
       it { expect(response).to render_template(:modifier) }
-      it { expect(flash.alert).to eq(["Le champ « l » doit être rempli, #{anchor_to_first_champ}"]) }
+      it { expect(response.body).to have_content("doit être rempli") }
+      it { expect(response.body).to have_link(first_champ.libelle, href: "##{first_champ.labelledby_id}") }
     end
 
     context 'when dossier has no champ' do
@@ -828,41 +832,44 @@ describe Users::DossiersController, type: :controller do
     end
 
     context 'when the update fails' do
-      before do
-        expect_any_instance_of(Dossier).to receive(:save).and_return(false)
-        expect_any_instance_of(Dossier).to receive(:errors).and_return(
-          [double(class: ActiveModel::Error, full_message: 'nop', base: first_champ)]
-        )
-        subject
+      render_views
+
+      context 'classic error' do
+        before do
+          expect_any_instance_of(Dossier).to receive(:save).and_return(false)
+          expect_any_instance_of(Dossier).to receive(:errors).and_return(
+            [message: 'nop', inner_error: double(base: first_champ)]
+          )
+          subject
+        end
+
+        it { expect(response).to render_template(:update) }
+
+        it 'does not update the dossier timestamps' do
+          dossier.reload
+          expect(dossier.updated_at).not_to eq(now)
+          expect(dossier.last_champ_updated_at).not_to eq(now)
+        end
+
+        it 'does not send an email' do
+          expect(NotificationMailer).not_to receive(:send_en_construction_notification)
+
+          subject
+        end
       end
 
-      it { expect(response).to render_template(:update) }
-      it { expect(flash.alert).to eq(["Le champ « #{first_champ.libelle} » nop, #{anchor_to_first_champ}"]) }
+      context 'iban error' do
+        let(:value) { 'abc' }
 
-      it 'does not update the dossier timestamps' do
-        dossier.reload
-        expect(dossier.updated_at).not_to eq(now)
-        expect(dossier.last_champ_updated_at).not_to eq(now)
+        before do
+          first_champ.type_de_champ.update!(type_champ: :iban, mandatory: true, libelle: 'l')
+          dossier.champs_public.first.becomes!(Champs::IbanChamp).save!
+
+          subject
+        end
+
+        it { expect(response).to have_http_status(:success) }
       end
-
-      it 'does not send an email' do
-        expect(NotificationMailer).not_to receive(:send_en_construction_notification)
-
-        subject
-      end
-    end
-
-    context 'when a champ validation fails' do
-      let(:value) { 'abc' }
-
-      before do
-        first_champ.type_de_champ.update!(type_champ: :iban, mandatory: true, libelle: 'l')
-        dossier.champs_public.first.becomes!(Champs::IbanChamp).save!
-
-        subject
-      end
-
-      it { expect(flash.alert).to include("Le champ « l » n’est pas au format IBAN, #{anchor_to_first_champ}") }
     end
 
     context 'when the user has an invitation but is not the owner' do
diff --git a/spec/system/api_particulier/api_particulier_spec.rb b/spec/system/api_particulier/api_particulier_spec.rb
index d72ca120c..554c058a2 100644
--- a/spec/system/api_particulier/api_particulier_spec.rb
+++ b/spec/system/api_particulier/api_particulier_spec.rb
@@ -282,7 +282,7 @@ describe 'fetch API Particulier Data', js: true, retry: 3 do
         wait_until { cnaf_champ.reload.code_postal == 'wrong_code' }
 
         click_on 'Déposer le dossier'
-        expect(page).to have_content(/Le champ « Champs public code postal » doit posséder 5 caractères/)
+        expect(page).to have_content("cnaf doit posséder 5 caractères")
 
         VCR.use_cassette('api_particulier/success/composition_familiale') do
           fill_in 'Le code postal', with: code_postal
@@ -479,7 +479,7 @@ describe 'fetch API Particulier Data', js: true, retry: 3 do
         wait_until { dgfip_champ.reload.reference_avis == 'wrong_code' }
 
         click_on 'Déposer le dossier'
-        expect(page).to have_content(/Le champ « Champs public reference avis » doit posséder 13 ou 14 caractères/)
+        expect(page).to have_content(/dgfip doit posséder 13 ou 14 caractères/)
 
         fill_in "La référence d’avis d’imposition", with: reference_avis
         wait_for_autosave
diff --git a/spec/system/users/brouillon_spec.rb b/spec/system/users/brouillon_spec.rb
index f20ef195f..78e95b5c1 100644
--- a/spec/system/users/brouillon_spec.rb
+++ b/spec/system/users/brouillon_spec.rb
@@ -109,7 +109,7 @@ describe 'The user' do
     fill_individual
     click_on 'Déposer le dossier'
 
-    expect(page).to have_selector("#flash_message")
+    expect(page).to have_selector("#sumup-errors")
     all('.error-anchor').map do |link_element|
       error_anchor = URI(link_element['href'])
       expect(page).to have_selector("##{error_anchor.fragment}")