diff --git a/app/models/dossier.rb b/app/models/dossier.rb
index 39dc2c7ae..93327302c 100644
--- a/app/models/dossier.rb
+++ b/app/models/dossier.rb
@@ -288,7 +288,7 @@ class Dossier < ApplicationRecord
   def passer_automatiquement_en_instruction!
     en_instruction!
 
-    log_dossier_operation(nil, :passer_en_instruction, automatic_operation: true)
+    log_automatic_dossier_operation(:passer_en_instruction)
   end
 
   def repasser_en_construction!(gestionnaire)
@@ -311,7 +311,7 @@ class Dossier < ApplicationRecord
     end
 
     NotificationMailer.send_closed_notification(self).deliver_later
-    log_dossier_operation(gestionnaire, :accepter)
+    log_dossier_operation(gestionnaire, :accepter, self)
   end
 
   def accepter_automatiquement!
@@ -324,14 +324,14 @@ class Dossier < ApplicationRecord
     end
 
     NotificationMailer.send_closed_notification(self).deliver_later
-    log_dossier_operation(nil, :accepter, automatic_operation: true)
+    log_automatic_dossier_operation(:accepter, self)
   end
 
   def hide!(administration)
     update(hidden_at: Time.zone.now)
 
-    log_administration_dossier_operation(administration, :supprimer)
     DeletedDossier.create_from_dossier(self)
+    log_dossier_operation(administration, :supprimer, self)
   end
 
   def refuser!(gestionnaire, motivation, justificatif = nil)
@@ -343,7 +343,7 @@ class Dossier < ApplicationRecord
     refuse!
 
     NotificationMailer.send_refused_notification(self).deliver_later
-    log_dossier_operation(gestionnaire, :refuser)
+    log_dossier_operation(gestionnaire, :refuser, self)
   end
 
   def classer_sans_suite!(gestionnaire, motivation, justificatif = nil)
@@ -355,7 +355,7 @@ class Dossier < ApplicationRecord
     sans_suite!
 
     NotificationMailer.send_without_continuation_notification(self).deliver_later
-    log_dossier_operation(gestionnaire, :classer_sans_suite)
+    log_dossier_operation(gestionnaire, :classer_sans_suite, self)
   end
 
   def check_mandatory_champs
@@ -368,18 +368,21 @@ class Dossier < ApplicationRecord
 
   private
 
-  def log_dossier_operation(gestionnaire, operation, automatic_operation: false)
-    dossier_operation_logs.create(
-      gestionnaire: gestionnaire,
+  def log_dossier_operation(author, operation, subject = nil)
+    DossierOperationLog.create_and_serialize(
+      dossier: self,
       operation: DossierOperationLog.operations.fetch(operation),
-      automatic_operation: automatic_operation
+      author: author,
+      subject: subject
     )
   end
 
-  def log_administration_dossier_operation(administration, operation)
-    dossier_operation_logs.create(
-      administration: administration,
-      operation: DossierOperationLog.operations.fetch(operation)
+  def log_automatic_dossier_operation(operation, subject = nil)
+    DossierOperationLog.create_and_serialize(
+      dossier: self,
+      operation: DossierOperationLog.operations.fetch(operation),
+      automatic_operation: true,
+      subject: subject
     )
   end
 
diff --git a/app/models/dossier_operation_log.rb b/app/models/dossier_operation_log.rb
index 6dced86b6..8cda68fde 100644
--- a/app/models/dossier_operation_log.rb
+++ b/app/models/dossier_operation_log.rb
@@ -9,6 +9,57 @@ class DossierOperationLog < ApplicationRecord
   }
 
   belongs_to :dossier
-  belongs_to :gestionnaire
-  belongs_to :administration
+  has_one_attached :serialized
+
+  def self.create_and_serialize(params)
+    dossier = params.fetch(:dossier)
+
+    operation_log = new(operation: params.fetch(:operation),
+      dossier_id: dossier.id,
+      keep_until: dossier.procedure.keep_until,
+      executed_at: Time.zone.now,
+      automatic_operation: !!params[:automatic_operation])
+
+    serialized = {
+      operation: operation_log.operation,
+      dossier_id: operation_log.dossier_id,
+      author: self.serialize_author(params[:author]),
+      subject: self.serialize_subject(params[:subject]),
+      automatic_operation: operation_log.automatic_operation?,
+      executed_at: operation_log.executed_at.iso8601
+    }.compact.to_json
+
+    operation_log.digest = Digest::SHA256.hexdigest(serialized)
+
+    operation_log.serialized.attach(
+      io: StringIO.new(serialized),
+      filename: "operation-#{operation_log.digest}.json",
+      content_type: 'application/json',
+      # we don't want to run virus scanner on this file
+      metadata: { virus_scan_result: ActiveStorage::VirusScanner::SAFE }
+    )
+
+    operation_log.save!
+  end
+
+  def self.serialize_author(author)
+    if author.nil?
+      nil
+    else
+      OperationAuthorSerializer.new(author).as_json
+    end
+  end
+
+  def self.serialize_subject(subject)
+    if subject.nil?
+      nil
+    elsif !Flipflop.operation_log_serialize_subject?
+      { id: subject.id }
+    else
+      case subject
+      when Dossier
+        DossierSerializer.new(subject).as_json
+      end
+    end
+  end
 end
diff --git a/app/serializers/operation_author_serializer.rb b/app/serializers/operation_author_serializer.rb
new file mode 100644
index 000000000..0856a1e90
--- /dev/null
+++ b/app/serializers/operation_author_serializer.rb
@@ -0,0 +1,18 @@
+class OperationAuthorSerializer < ActiveModel::Serializer
+  attributes :id, :email
+
+  def id
+    case object
+    when User
+      "Usager##{object.id}"
+    when Gestionnaire
+      "Instructeur##{object.id}"
+    when Administrateur
+      "Administrateur##{object.id}"
+    when Administration
+      "Manager##{object.id}"
+    else
+      nil
+    end
+  end
+end
diff --git a/config/features.rb b/config/features.rb
index f42abcf32..13f6d592a 100644
--- a/config/features.rb
+++ b/config/features.rb
@@ -17,6 +17,8 @@ Flipflop.configure do
   feature :enable_email_login_token
   feature :new_champs_editor
 
+  feature :operation_log_serialize_subject
+
   group :production do
     feature :remote_storage,
       default: ENV['FOG_ENABLED'] == 'enabled'
diff --git a/spec/jobs/auto_archive_procedure_job_spec.rb b/spec/jobs/auto_archive_procedure_job_spec.rb
index 2103f8a8a..8e0225357 100644
--- a/spec/jobs/auto_archive_procedure_job_spec.rb
+++ b/spec/jobs/auto_archive_procedure_job_spec.rb
@@ -27,6 +27,7 @@ RSpec.describe AutoArchiveProcedureJob, type: :job do
     let!(:dossier7) { create(:dossier, procedure: procedure_hier, state: Dossier.states.fetch(:refuse), archived: false) }
     let!(:dossier8) { create(:dossier, procedure: procedure_hier, state: Dossier.states.fetch(:sans_suite), archived: false) }
     let!(:dossier9) { create(:dossier, procedure: procedure_aujourdhui, state: Dossier.states.fetch(:en_construction), archived: false) }
+    let(:last_operation) { dossier2.dossier_operation_logs.last }
 
     before do
       subject
@@ -40,7 +41,8 @@ RSpec.describe AutoArchiveProcedureJob, type: :job do
     it {
       expect(dossier1.state).to eq Dossier.states.fetch(:brouillon)
       expect(dossier2.state).to eq Dossier.states.fetch(:en_instruction)
-      expect(dossier2.dossier_operation_logs.pluck(:gestionnaire_id, :operation, :automatic_operation)).to match([[nil, 'passer_en_instruction', true]])
+      expect(last_operation.operation).to eq('passer_en_instruction')
+      expect(last_operation.automatic_operation?).to be_truthy
       expect(dossier3.state).to eq Dossier.states.fetch(:en_instruction)
       expect(dossier4.state).to eq Dossier.states.fetch(:en_instruction)
       expect(dossier5.state).to eq Dossier.states.fetch(:en_instruction)
diff --git a/spec/jobs/auto_receive_dossiers_for_procedure_job_spec.rb b/spec/jobs/auto_receive_dossiers_for_procedure_job_spec.rb
index a2ab0a799..517a6dde9 100644
--- a/spec/jobs/auto_receive_dossiers_for_procedure_job_spec.rb
+++ b/spec/jobs/auto_receive_dossiers_for_procedure_job_spec.rb
@@ -31,11 +31,13 @@ RSpec.describe AutoReceiveDossiersForProcedureJob, type: :job do
     context "with some dossiers" do
       context "en_construction" do
         let(:state) { Dossier.states.fetch(:en_instruction) }
+        let(:last_operation) { nouveau_dossier1.dossier_operation_logs.last }
 
         it {
           expect(nouveau_dossier1.en_instruction?).to be true
           expect(nouveau_dossier1.en_instruction_at).to eq(date)
-          expect(nouveau_dossier1.dossier_operation_logs.pluck(:gestionnaire_id, :operation, :automatic_operation)).to match([[nil, 'passer_en_instruction', true]])
+          expect(last_operation.operation).to eq('passer_en_instruction')
+          expect(last_operation.automatic_operation?).to be_truthy
 
           expect(nouveau_dossier2.en_instruction?).to be true
           expect(nouveau_dossier2.en_instruction_at).to eq(date)
@@ -50,13 +52,15 @@ RSpec.describe AutoReceiveDossiersForProcedureJob, type: :job do
 
       context "accepte" do
         let(:state) { Dossier.states.fetch(:accepte) }
+        let(:last_operation) { nouveau_dossier1.dossier_operation_logs.last }
 
         it {
           expect(nouveau_dossier1.accepte?).to be true
           expect(nouveau_dossier1.en_instruction_at).to eq(date)
           expect(nouveau_dossier1.processed_at).to eq(date)
           expect(nouveau_dossier1.attestation).to be_present
-          expect(nouveau_dossier1.dossier_operation_logs.pluck(:gestionnaire_id, :operation, :automatic_operation)).to match([[nil, 'accepter', true]])
+          expect(last_operation.operation).to eq('accepter')
+          expect(last_operation.automatic_operation?).to be_truthy
 
           expect(nouveau_dossier2.accepte?).to be true
           expect(nouveau_dossier2.en_instruction_at).to eq(date)
diff --git a/spec/models/dossier_spec.rb b/spec/models/dossier_spec.rb
index ea85160af..a39b96117 100644
--- a/spec/models/dossier_spec.rb
+++ b/spec/models/dossier_spec.rb
@@ -764,6 +764,8 @@ describe Dossier do
 
   describe '#accepter!' do
     let(:dossier) { create(:dossier) }
+    let(:last_operation) { dossier.dossier_operation_logs.last }
+    let(:operation_serialized) { JSON.parse(last_operation.serialized.download) }
     let!(:gestionnaire) { create(:gestionnaire) }
     let!(:now) { Time.zone.parse('01/01/2100') }
     let(:attestation) { Attestation.new }
@@ -783,13 +785,18 @@ describe Dossier do
     it { expect(dossier.en_instruction_at).to eq(now) }
     it { expect(dossier.processed_at).to eq(now) }
     it { expect(dossier.state).to eq('accepte') }
-    it { expect(dossier.dossier_operation_logs.pluck(:gestionnaire_id, :operation, :automatic_operation)).to match([[gestionnaire.id, 'accepter', false]]) }
+    it { expect(last_operation.operation).to eq('accepter') }
+    it { expect(last_operation.automatic_operation?).to be_falsey }
+    it { expect(operation_serialized['operation']).to eq('accepter') }
+    it { expect(operation_serialized['dossier_id']).to eq(dossier.id) }
+    it { expect(operation_serialized['executed_at']).to eq(last_operation.executed_at.iso8601) }
     it { expect(NotificationMailer).to have_received(:send_closed_notification).with(dossier) }
     it { expect(dossier.attestation).to eq(attestation) }
   end
 
   describe '#accepter_automatiquement!' do
     let(:dossier) { create(:dossier) }
+    let(:last_operation) { dossier.dossier_operation_logs.last }
     let!(:now) { Time.zone.parse('01/01/2100') }
     let(:attestation) { Attestation.new }
 
@@ -808,30 +815,43 @@ describe Dossier do
     it { expect(dossier.en_instruction_at).to eq(now) }
     it { expect(dossier.processed_at).to eq(now) }
     it { expect(dossier.state).to eq('accepte') }
-    it { expect(dossier.dossier_operation_logs.pluck(:gestionnaire_id, :operation, :automatic_operation)).to match([[nil, 'accepter', true]]) }
+    it { expect(last_operation.operation).to eq('accepter') }
+    it { expect(last_operation.automatic_operation?).to be_truthy }
     it { expect(NotificationMailer).to have_received(:send_closed_notification).with(dossier) }
     it { expect(dossier.attestation).to eq(attestation) }
   end
 
   describe '#passer_en_instruction!' do
     let(:dossier) { create(:dossier) }
+    let(:last_operation) { dossier.dossier_operation_logs.last }
+    let(:operation_serialized) { JSON.parse(last_operation.serialized.download) }
     let(:gestionnaire) { create(:gestionnaire) }
 
     before { dossier.passer_en_instruction!(gestionnaire) }
 
     it { expect(dossier.state).to eq('en_instruction') }
     it { expect(dossier.followers_gestionnaires).to include(gestionnaire) }
-    it { expect(dossier.dossier_operation_logs.pluck(:gestionnaire_id, :operation)).to match([[gestionnaire.id, 'passer_en_instruction']]) }
+    it { expect(last_operation.operation).to eq('passer_en_instruction') }
+    it { expect(last_operation.automatic_operation?).to be_falsey }
+    it { expect(operation_serialized['operation']).to eq('passer_en_instruction') }
+    it { expect(operation_serialized['dossier_id']).to eq(dossier.id) }
+    it { expect(operation_serialized['executed_at']).to eq(last_operation.executed_at.iso8601) }
   end
 
   describe '#passer_automatiquement_en_instruction!' do
     let(:dossier) { create(:dossier) }
+    let(:last_operation) { dossier.dossier_operation_logs.last }
+    let(:operation_serialized) { JSON.parse(last_operation.serialized.download) }
     let(:gestionnaire) { create(:gestionnaire) }
 
     before { dossier.passer_automatiquement_en_instruction! }
 
     it { expect(dossier.followers_gestionnaires).not_to include(gestionnaire) }
-    it { expect(dossier.dossier_operation_logs.pluck(:gestionnaire_id, :operation, :automatic_operation)).to match([[nil, 'passer_en_instruction', true]]) }
+    it { expect(last_operation.operation).to eq('passer_en_instruction') }
+    it { expect(last_operation.automatic_operation?).to be_truthy }
+    it { expect(operation_serialized['operation']).to eq('passer_en_instruction') }
+    it { expect(operation_serialized['dossier_id']).to eq(dossier.id) }
+    it { expect(operation_serialized['executed_at']).to eq(last_operation.executed_at.iso8601) }
   end
 
   describe "#check_mandatory_champs" do
@@ -934,6 +954,6 @@ describe Dossier do
 
     it { expect(dossier.hidden_at).to eq(Time.zone.now) }
     it { expect(last_operation.operation).to eq('supprimer') }
-    it { expect(last_operation.administration).to eq(administration) }
+    it { expect(last_operation.automatic_operation?).to be_falsey }
   end
 end