diff --git a/packages/forest_admin_agent/lib/forest_admin_agent/routes/abstract_route.rb b/packages/forest_admin_agent/lib/forest_admin_agent/routes/abstract_route.rb
index eb31bcbbb..104d5acdf 100644
--- a/packages/forest_admin_agent/lib/forest_admin_agent/routes/abstract_route.rb
+++ b/packages/forest_admin_agent/lib/forest_admin_agent/routes/abstract_route.rb
@@ -28,7 +28,14 @@ def routes
       end
 
       def add_route(name, method, uri, closure, format = 'json')
-        @routes[name] = { method: method, uri: uri, closure: closure, format: format }
+        instrumented = lambda do |args|
+          ForestAdminDatasourceToolkit::Monitoring.instrument(
+            'request',
+            { route: name, collection: args.dig(:params, 'collection_name'),
+              id: args.dig(:params, 'id'), method: method }
+          ) { closure.call(args) }
+        end
+        @routes[name] = { method: method, uri: uri, closure: instrumented, format: format }
       end
 
       def setup_routes
diff --git a/packages/forest_admin_agent/spec/lib/forest_admin_agent/routes/abstract_route_spec.rb b/packages/forest_admin_agent/spec/lib/forest_admin_agent/routes/abstract_route_spec.rb
new file mode 100644
index 000000000..6d14a9efb
--- /dev/null
+++ b/packages/forest_admin_agent/spec/lib/forest_admin_agent/routes/abstract_route_spec.rb
@@ -0,0 +1,35 @@
+require 'spec_helper'
+require 'active_support/isolated_execution_state'
+require 'active_support/notifications'
+
+module ForestAdminAgent
+  module Routes
+    describe AbstractRoute do
+      let(:route_class) do
+        Class.new(described_class) do
+          def setup_routes
+            add_route('forest_test', 'get', '/test', ->(args) { { echoed: args.dig(:params, 'collection_name') } })
+            self
+          end
+        end
+      end
+
+      it 'wraps the closure in a request.forest_admin notification and passes the return value through' do
+        events = []
+        subscriber = ::ActiveSupport::Notifications.subscribe('request.forest_admin') do |*args|
+          events << ::ActiveSupport::Notifications::Event.new(*args)
+        end
+
+        route = route_class.new.routes['forest_test']
+        result = route[:closure].call({ params: { 'collection_name' => 'user', 'id' => '42' } })
+
+        ::ActiveSupport::Notifications.unsubscribe(subscriber)
+
+        expect(result).to eq({ echoed: 'user' })
+        expect(events.size).to eq(1)
+        expect(events.first.payload).to eq({ route: 'forest_test', collection: 'user', id: '42', method: 'get' })
+        expect(events.first.duration).to be >= 0
+      end
+    end
+  end
+end
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/context/relaxed_wrappers/relaxed_collection.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/context/relaxed_wrappers/relaxed_collection.rb
index e2bc7d836..c1c04ffe8 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/context/relaxed_wrappers/relaxed_collection.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/context/relaxed_wrappers/relaxed_collection.rb
@@ -9,6 +9,10 @@ def initialize(collection, caller)
           @caller = caller
         end
 
+        def name
+          @collection.name
+        end
+
         def native_driver(&block)
           @collection.native_driver(&block)
         end
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/action/action_collection_decorator.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/action/action_collection_decorator.rb
index 65bb93bb0..71a390343 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/action/action_collection_decorator.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/action/action_collection_decorator.rb
@@ -27,7 +27,9 @@ def execute(caller, name, data, filter = nil)
           context = get_context(caller, action, data, filter)
 
           result_builder = ResultBuilder.new
-          result = action.execute.call(context, result_builder)
+          result = ForestAdminDatasourceToolkit::Monitoring.instrument(
+            'action', { collection: self.name, action: name }, caller: caller
+          ) { action.execute.call(context, result_builder) }
 
           return result if result.is_a? Hash
 
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/chart/chart_collection_decorator.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/chart/chart_collection_decorator.rb
index 3e90a3ba2..53a3c0ff5 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/chart/chart_collection_decorator.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/chart/chart_collection_decorator.rb
@@ -24,7 +24,9 @@ def render_chart(caller, name, record_id, parameters = {})
             context = ChartContext.new(self, caller, record_id, parameters)
             result_builder = ResultBuilder.new
 
-            return @charts[name].call(context, result_builder)
+            return ForestAdminDatasourceToolkit::Monitoring.instrument(
+              'chart', { collection: self.name, chart: name }, caller: caller
+            ) { @charts[name].call(context, result_builder) }
           end
 
           @child_collection.render_chart(caller, name, record_id, parameters)
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/chart/chart_datasource_decorator.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/chart/chart_datasource_decorator.rb
index 7af39e26f..8ba42d33f 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/chart/chart_datasource_decorator.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/chart/chart_datasource_decorator.rb
@@ -32,10 +32,12 @@ def render_chart(caller, name, parameters = {})
           chart_definition = @charts[name]
 
           if chart_definition
-            return chart_definition.call(
-              DatasourceChartContext.new(self, caller, parameters),
-              ResultBuilder.new
-            )
+            return ForestAdminDatasourceToolkit::Monitoring.instrument('chart', { chart: name }, caller: caller) do
+              chart_definition.call(
+                DatasourceChartContext.new(self, caller, parameters),
+                ResultBuilder.new
+              )
+            end
           end
 
           super
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/computed/utils/computed_field.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/computed/utils/computed_field.rb
index 6347f0465..31c02844c 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/computed/utils/computed_field.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/computed/utils/computed_field.rb
@@ -35,7 +35,9 @@ def self.queue_field(ctx, collection, new_path, paths, flatten)
 
             paths.push(new_path)
 
-            flatten << compute_field(ctx, computed, computed_dependencies, dependency_values)
+            flatten << ForestAdminDatasourceToolkit::Monitoring.instrument(
+              'computed_field', { collection: collection.name, field: new_path }, caller: ctx.caller
+            ) { compute_field(ctx, computed, computed_dependencies, dependency_values) }
           end
 
           def self.compute_from_records(ctx, collection, records_projection, desired_projection, records)
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/hook/hook_collection_decorator.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/hook/hook_collection_decorator.rb
index f12455a27..7ab2bbc45 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/hook/hook_collection_decorator.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/hook/hook_collection_decorator.rb
@@ -10,11 +10,11 @@ class HookCollectionDecorator < ForestAdminDatasourceToolkit::Decorators::Collec
         def initialize(child_collection, datasource)
           super
           @hooks = {
-            'List' => Hooks.new,
-            'Create' => Hooks.new,
-            'Update' => Hooks.new,
-            'Delete' => Hooks.new,
-            'Aggregate' => Hooks.new
+            'List' => Hooks.new('List'),
+            'Create' => Hooks.new('Create'),
+            'Update' => Hooks.new('Update'),
+            'Delete' => Hooks.new('Delete'),
+            'Aggregate' => Hooks.new('Aggregate')
           }
         end
 
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/hook/hooks.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/hook/hooks.rb
index fc644bb5a..84390e47f 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/hook/hooks.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/hook/hooks.rb
@@ -4,22 +4,35 @@ module Hook
       class Hooks
         attr_reader :before, :after
 
-        def initialize
+        def initialize(type = nil)
+          @type = type
           @before = []
           @after = []
         end
 
         def execute_before(context)
-          @before.each { |hook| hook.call(context) }
+          instrument('before', context) { @before.each { |hook| hook.call(context) } }
         end
 
         def execute_after(context)
-          @after.each { |hook| hook.call(context) }
+          instrument('after', context) { @after.each { |hook| hook.call(context) } }
         end
 
         def add_handler(position, hook)
           position == 'After' ? @after << hook : @before << hook
         end
+
+        private
+
+        def instrument(position, context, &block)
+          hooks = position == 'before' ? @before : @after
+          return yield if hooks.empty?
+
+          ForestAdminDatasourceToolkit::Monitoring.instrument(
+            'hook', { collection: context.collection.name, operation: @type, position: position },
+            caller: context.caller, &block
+          )
+        end
       end
     end
   end
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/operators_emulate/operators_emulate_collection_decorator.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/operators_emulate/operators_emulate_collection_decorator.rb
index 4642835ca..f8555c0fb 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/operators_emulate/operators_emulate_collection_decorator.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/operators_emulate/operators_emulate_collection_decorator.rb
@@ -89,7 +89,9 @@ def compute_equivalent(caller, leaf, replacements)
               raise Exceptions::ForestException, "Operator replacement cycle: #{sub_replacements.join(" -> ")}"
             end
 
-            result = handler.call(leaf.value, Context::CollectionCustomizationContext.new(self, caller))
+            result = ForestAdminDatasourceToolkit::Monitoring.instrument(
+              'operator_emulation', { collection: name, field: leaf.field, operator: leaf.operator }, caller: caller
+            ) { handler.call(leaf.value, Context::CollectionCustomizationContext.new(self, caller)) }
 
             if result
               equivalent = result.class < Nodes::ConditionTree ? result : ConditionTreeFactory.from_plain_object(result)
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/override/override_collection_decorator.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/override/override_collection_decorator.rb
index 9e805a734..1a3d5cc5b 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/override/override_collection_decorator.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/override/override_collection_decorator.rb
@@ -9,7 +9,9 @@ class OverrideCollectionDecorator < ForestAdminDatasourceToolkit::Decorators::Co
         def create(caller, data)
           if @create_handler
             context = CreateOverrideCustomizationContext.new(@child_collection, caller, data)
-            return @create_handler.call(context)
+            return ForestAdminDatasourceToolkit::Monitoring.instrument(
+              'override', { collection: name, operation: 'create' }, caller: caller
+            ) { @create_handler.call(context) }
           end
 
           super
@@ -22,7 +24,9 @@ def add_create_handler(handler)
         def update(caller, filter, patch)
           if @update_handler
             context = UpdateOverrideCustomizationContext.new(@child_collection, caller, filter, patch)
-            return @update_handler.call(context)
+            return ForestAdminDatasourceToolkit::Monitoring.instrument(
+              'override', { collection: name, operation: 'update' }, caller: caller
+            ) { @update_handler.call(context) }
           end
 
           super
@@ -35,7 +39,9 @@ def add_update_handler(handler)
         def delete(caller, filter)
           if @delete_handler
             context = DeleteOverrideCustomizationContext.new(@child_collection, caller, filter)
-            return @delete_handler.call(context)
+            return ForestAdminDatasourceToolkit::Monitoring.instrument(
+              'override', { collection: name, operation: 'delete' }, caller: caller
+            ) { @delete_handler.call(context) }
           end
 
           super
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/search/search_collection_decorator.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/search/search_collection_decorator.rb
index 1f894f18a..56f84d908 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/search/search_collection_decorator.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/search/search_collection_decorator.rb
@@ -39,7 +39,11 @@ def refine_filter(caller, filter)
             tree = default_replacer(filter.search, filter.search_extended)
 
             if @replacer
-              plain_tree = @replacer.call(filter.search, filter.search_extended, ctx)
+              plain_tree = ForestAdminDatasourceToolkit::Monitoring.instrument(
+                'search', { collection: name }, caller: caller
+              ) do
+                @replacer.call(filter.search, filter.search_extended, ctx)
+              end
               tree = ConditionTreeFactory.from_plain_object(plain_tree)
             end
 
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/segment/segment_collection_decorator.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/segment/segment_collection_decorator.rb
index ec70f3c4e..b62f31de3 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/segment/segment_collection_decorator.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/segment/segment_collection_decorator.rb
@@ -25,24 +25,26 @@ def refine_schema(sub_schema)
           sub_schema
         end
 
-        def refine_filter(_caller, filter = nil)
+        def refine_filter(caller, filter = nil)
           return nil unless filter
 
           condition_tree = filter.condition_tree
           segment = filter.segment
           if segment && @segments.key?(segment)
-            condition_tree = compute_segment(segment, filter)
+            condition_tree = compute_segment(segment, filter, caller)
             segment = nil
           end
 
           filter.override(condition_tree: condition_tree, segment: segment)
         end
 
-        def compute_segment(segment_name, filter)
+        def compute_segment(segment_name, filter, caller)
           definition = @segments[segment_name]
 
           result = if definition.respond_to? :call
-                     definition.call(Context::CollectionCustomizationContext.new(self, caller))
+                     ForestAdminDatasourceToolkit::Monitoring.instrument(
+                       'segment', { collection: name, segment: segment_name }, caller: caller
+                     ) { definition.call(Context::CollectionCustomizationContext.new(self, caller)) }
                    else
                      definition
                    end
diff --git a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/write/write_replace/write_replace_collection_decorator.rb b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/write/write_replace/write_replace_collection_decorator.rb
index 3c3d0a940..dbc8976e3 100644
--- a/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/write/write_replace/write_replace_collection_decorator.rb
+++ b/packages/forest_admin_datasource_customizer/lib/forest_admin_datasource_customizer/decorators/write/write_replace/write_replace_collection_decorator.rb
@@ -72,12 +72,20 @@ def rewrite_key(context, key, used)
 
             if field_schema&.type == 'Column'
               # We either call the customer handler or a default one that does nothing.
-              handler = @handlers[key] || proc { |v| { key => v } }
-              field_patch = if context.record.key?(key) && handler.call(context.record[key], context)
-                              handler.call(context.record[key], context)
-                            else
-                              {}
-                            end
+              user_handler = @handlers[key]
+              handler = user_handler || proc { |v| { key => v } }
+              # ponytail: single evaluation (the previous code called the handler twice); only the
+              # user handler is instrumented — the default no-op proc isn't user code.
+              raw = if context.record.key?(key)
+                      if user_handler
+                        ForestAdminDatasourceToolkit::Monitoring.instrument(
+                          'write', { collection: name, field: key }, caller: context.caller
+                        ) { handler.call(context.record[key], context) }
+                      else
+                        handler.call(context.record[key], context)
+                      end
+                    end
+              field_patch = raw || {}
 
               if field_patch && !field_patch.is_a?(Hash)
                 raise ForestException, "The write handler of #{key} should return an Hash or nothing."
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/datasource_customizer_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/datasource_customizer_spec.rb
index d91299183..4737b7270 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/datasource_customizer_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/datasource_customizer_spec.rb
@@ -6,6 +6,9 @@ module ForestAdminDatasourceCustomizer
 
   describe DatasourceCustomizer do
     let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
+    let(:caller) do
+      instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test')
+    end
 
     before do
       @collection = instance_double(
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/action/action_collection_decorator_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/action/action_collection_decorator_spec.rb
index 828b7994e..98aa0d712 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/action/action_collection_decorator_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/action/action_collection_decorator_spec.rb
@@ -91,6 +91,17 @@ module Action
             expect(result).to eq({ response_headers: {}, type: 'Success', message: 'Success', invalidated: [], html: nil })
           end
 
+          it 'emits an action.forest_admin notification' do
+            events = []
+            sub = ::ActiveSupport::Notifications.subscribe('action.forest_admin') do |*a|
+              events << ::ActiveSupport::Notifications::Event.new(*a)
+            end
+            @decorated_book.execute(caller, 'make photocopy', {}, Filter.new)
+            ::ActiveSupport::Notifications.unsubscribe(sub)
+
+            expect(events.map(&:payload)).to include(include(action: 'make photocopy'))
+          end
+
           it 'generate empty form' do
             form = @decorated_book.get_form(caller, 'make photocopy', {}, Filter.new)
             expect(form).to eq([])
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/chart/chart_collection_decorator_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/chart/chart_collection_decorator_spec.rb
index ba15435d3..56e167647 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/chart/chart_collection_decorator_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/chart/chart_collection_decorator_spec.rb
@@ -64,6 +64,17 @@ module Chart
 
               expect(result).to eq({ countCurrent: 2 })
             end
+
+            it 'emits a chart.forest_admin notification' do
+              events = []
+              sub = ::ActiveSupport::Notifications.subscribe('chart.forest_admin') do |*a|
+                events << ::ActiveSupport::Notifications::Event.new(*a)
+              end
+              @decorated_book.render_chart(caller, 'new_chart', [123])
+              ::ActiveSupport::Notifications.unsubscribe(sub)
+
+              expect(events.map(&:payload)).to include(include(chart: 'new_chart'))
+            end
           end
         end
       end
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/computed/compute_collection_decorator_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/computed/compute_collection_decorator_spec.rb
index c5c811639..073ed89e0 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/computed/compute_collection_decorator_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/computed/compute_collection_decorator_spec.rb
@@ -1,4 +1,5 @@
 require 'spec_helper'
+require 'active_support/notifications'
 
 module ForestAdminDatasourceCustomizer
   module Decorators
@@ -193,6 +194,21 @@ module Computed
                                   ])
           end
 
+          it 'list() should emit a computed_field.forest_admin notification' do
+            events = []
+            subscriber = ::ActiveSupport::Notifications.subscribe('computed_field.forest_admin') do |*args|
+              events << ::ActiveSupport::Notifications::Event.new(*args)
+            end
+
+            @new_books.list(caller, Filter.new, Projection.new(['title', 'author:fullName']))
+
+            ::ActiveSupport::Notifications.unsubscribe(subscriber)
+
+            expect(events.map(&:payload)).to include(
+              include(collection: 'book', field: 'author:fullName', user_id: 1, rendering_id: 1, project: 'terminator')
+            )
+          end
+
           it 'aggregate() should use the child implementation when relevant' do
             rows = @new_books.aggregate(
               caller,
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/hook/hook_collection_decorator_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/hook/hook_collection_decorator_spec.rb
index c7447d763..e048f4598 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/hook/hook_collection_decorator_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/hook/hook_collection_decorator_spec.rb
@@ -12,7 +12,9 @@ module Hook
       describe HookCollectionDecorator do
         subject(:hook_collection_decorator) { described_class }
 
-        let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+        let(:caller) do
+          instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test')
+        end
         let(:aggregation) { instance_double(ForestAdminDatasourceToolkit::Components::Query::Aggregation) }
 
         before do
@@ -60,6 +62,19 @@ module Hook
 
               expect(spy).to have_received(:call).once
             end
+
+            it 'emits a hook.forest_admin notification for registered hooks' do
+              spy = instance_double(Proc, call: nil)
+              @decorated_transaction.add_hook('Before', 'Create', spy)
+              events = []
+              sub = ::ActiveSupport::Notifications.subscribe('hook.forest_admin') do |*a|
+                events << ::ActiveSupport::Notifications::Event.new(*a)
+              end
+              @decorated_transaction.create(caller, [])
+              ::ActiveSupport::Notifications.unsubscribe(sub)
+
+              expect(events.map(&:payload)).to include(include(operation: 'Create', position: 'before', collection: 'transaction'))
+            end
           end
 
           describe 'on a update' do
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/override/override_collection_decorator_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/override/override_collection_decorator_spec.rb
index 5dea845bf..bca402e49 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/override/override_collection_decorator_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/override/override_collection_decorator_spec.rb
@@ -10,7 +10,7 @@ module Override
       describe OverrideCollectionDecorator do
         subject(:override_collection_decorator) { described_class }
 
-        let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+        let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
 
         before do
           datasource = Datasource.new
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/search/search_collection_decorator_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/search/search_collection_decorator_spec.rb
index 46fb7afcd..483bb2433 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/search/search_collection_decorator_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/search/search_collection_decorator_spec.rb
@@ -10,7 +10,7 @@ module Search
       describe SearchCollectionDecorator do
         let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
 
-        let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+        let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
 
         before do
           @collection_user = instance_double(
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/segment/segment_collection_decorator_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/segment/segment_collection_decorator_spec.rb
index 84af63f63..4cdb38956 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/segment/segment_collection_decorator_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/segment/segment_collection_decorator_spec.rb
@@ -10,6 +10,10 @@ module Segment
       include ForestAdminDatasourceToolkit::Schema
 
       describe SegmentCollectionDecorator do
+        let(:caller) do
+          instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test')
+        end
+
         before do
           datasource = Datasource.new
           @collection = build_collection(
@@ -58,6 +62,22 @@ module Segment
 
           context 'when the segment is managed by this decorator' do
             describe 'refine_filter' do
+              it 'emits a segment.forest_admin notification when the definition is callable' do
+                @decorated_collection.add_segment('segment_name', proc do
+                  Nodes::ConditionTreeLeaf.new('name', Operators::EQUAL, 'foo')
+                end)
+                a_filter = Filter.new(segment: 'segment_name')
+
+                events = []
+                sub = ::ActiveSupport::Notifications.subscribe('segment.forest_admin') do |*a|
+                  events << ::ActiveSupport::Notifications::Event.new(*a)
+                end
+                @decorated_collection.refine_filter(caller, a_filter)
+                ::ActiveSupport::Notifications.unsubscribe(sub)
+
+                expect(events.map(&:payload)).to include(include(segment: 'segment_name'))
+              end
+
               it 'return the filter with the merged conditionTree' do
                 condition_tree_generator = Nodes::ConditionTreeLeaf.new('name', Operators::EQUAL, 'foo')
                 @decorated_collection.add_segment('segment_name', condition_tree_generator)
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_mixed_relations_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_mixed_relations_spec.rb
index 1d739377f..ec8fd1b6f 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_mixed_relations_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_mixed_relations_spec.rb
@@ -11,7 +11,7 @@ module WriteReplace
         describe WriteDatasourceDecorator do
           let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
           let(:write_datasource_decorator) { described_class }
-          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
 
           before do
             @collection_book = instance_double(
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_multiple_many_to_one_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_multiple_many_to_one_spec.rb
index 04faa494d..1b88b5c53 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_multiple_many_to_one_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_multiple_many_to_one_spec.rb
@@ -11,7 +11,7 @@ module WriteReplace
         describe WriteDatasourceDecorator do
           let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
           let(:write_datasource_decorator) { described_class }
-          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
 
           before do
             @collection_book = instance_double(
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_multiple_one_to_one_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_multiple_one_to_one_spec.rb
index 71ac3f8ac..09c6c16d4 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_multiple_one_to_one_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_multiple_one_to_one_spec.rb
@@ -11,7 +11,7 @@ module WriteReplace
         describe WriteDatasourceDecorator do
           let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
           let(:write_datasource_decorator) { described_class }
-          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
 
           before do
             @collection_book = instance_double(
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_single_many_to_one_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_single_many_to_one_spec.rb
index b0341f8cd..77af1497b 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_single_many_to_one_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_single_many_to_one_spec.rb
@@ -12,7 +12,7 @@ module WriteReplace
         describe WriteDatasourceDecorator do
           let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
           let(:write_datasource_decorator) { described_class }
-          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
 
           before do
             @collection_price = instance_double(
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_single_one_to_one_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_single_one_to_one_spec.rb
index 41ce6911b..91fac16ae 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_single_one_to_one_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/create_relations/collection_single_one_to_one_spec.rb
@@ -12,7 +12,7 @@ module WriteReplace
         describe WriteDatasourceDecorator do
           let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
           let(:write_datasource_decorator) { described_class }
-          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
 
           before do
             @collection_book = instance_double(
@@ -106,7 +106,7 @@ module WriteReplace
             )
             allow(@collection_owner).to receive(:create)
 
-            caller = instance_double(ForestAdminDatasourceToolkit::Components::Caller)
+            caller = instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test')
             @decorated_book.create(caller, { 'title' => 'a title' })
 
             expect(@collection_owner).to have_received(:create).with(caller, { 'name' => 'NAME TO CHANGE', 'book_id' => '123e4567-e89b-12d3-a456-111111111111' })
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/update_relations/collection_many_to_one_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/update_relations/collection_many_to_one_spec.rb
index 44ddf6aa6..51e061647 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/update_relations/collection_many_to_one_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/update_relations/collection_many_to_one_spec.rb
@@ -13,7 +13,7 @@ module UpdateRelations
         describe UpdateRelationsCollectionDecorator do
           let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
           let(:update_relations_datasource_decorator) { described_class }
-          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
 
           before do
             @collection_author = instance_double(
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/update_relations/collection_one_to_one_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/update_relations/collection_one_to_one_spec.rb
index 46a50587f..0607af628 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/update_relations/collection_one_to_one_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/update_relations/collection_one_to_one_spec.rb
@@ -13,7 +13,7 @@ module UpdateRelations
         describe UpdateRelationsCollectionDecorator do
           let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
           let(:update_relations_datasource_decorator) { described_class }
-          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
 
           before do
             @collection_author = instance_double(
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_relation_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_relation_spec.rb
index ca3e34c96..6e938fd03 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_relation_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_relation_spec.rb
@@ -11,7 +11,7 @@ module WriteReplace
         describe WriteReplaceCollectionDecorator do
           let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
           let(:write_datasource_decorator) { ForestAdminDatasourceCustomizer::Decorators::Write::WriteDatasourceDecorator }
-          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
 
           before do
             @collection_author = instance_double(
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_simple_creation_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_simple_creation_spec.rb
index c05029e20..1e82b6254 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_simple_creation_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_simple_creation_spec.rb
@@ -11,7 +11,7 @@ module WriteReplace
         describe WriteReplaceCollectionDecorator do
           let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
           let(:write_datasource_decorator) { ForestAdminDatasourceCustomizer::Decorators::Write::WriteDatasourceDecorator }
-          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
 
           before do
             @collection_book = instance_double(
@@ -43,6 +43,27 @@ module WriteReplace
           end
 
           context 'when rewrite the record' do
+            it 'invokes the handler once and emits a write.forest_admin notification' do
+              record = { 'name' => 'a name' }
+              allow(@collection_book).to receive(:create).and_return(record)
+
+              calls = 0
+              @decorated_book.replace_field_writing('name') do |value, _context|
+                calls += 1
+                { 'name' => value }
+              end
+
+              events = []
+              sub = ::ActiveSupport::Notifications.subscribe('write.forest_admin') do |*a|
+                events << ::ActiveSupport::Notifications::Event.new(*a)
+              end
+              @decorated_book.create(caller, record)
+              ::ActiveSupport::Notifications.unsubscribe(sub)
+
+              expect(calls).to eq(1)
+              expect(events.map(&:payload)).to include(include(collection: 'book', field: 'name'))
+            end
+
             it 'with a empty handler' do
               record = { 'name' => 'a name', 'age' => 'some age' }
               allow(@collection_book).to receive(:create).and_return(record)
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_simple_update_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_simple_update_spec.rb
index fbfee9c36..84087963a 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_simple_update_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/collection_simple_update_spec.rb
@@ -11,7 +11,7 @@ module WriteReplace
         describe WriteReplaceCollectionDecorator do
           let(:datasource) { ForestAdminDatasourceToolkit::Datasource.new }
           let(:write_datasource_decorator) { ForestAdminDatasourceCustomizer::Decorators::Write::WriteDatasourceDecorator }
-          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+          let(:caller) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
           let(:filter) { Filter.new }
 
           before do
diff --git a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/write_customization_context_spec.rb b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/write_customization_context_spec.rb
index ad08a1e6c..9e78945ec 100644
--- a/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/write_customization_context_spec.rb
+++ b/packages/forest_admin_datasource_customizer/spec/lib/forest_admin_datasource_customizer/decorators/write/write_replace/write_customization_context_spec.rb
@@ -8,7 +8,7 @@ module WriteReplace
 
         describe WriteCustomizationContext do
           let(:collection) { build_collection }
-          let(:caller_context) { instance_double(ForestAdminDatasourceToolkit::Components::Caller) }
+          let(:caller_context) { instance_double(ForestAdminDatasourceToolkit::Components::Caller, id: 1, rendering_id: 1, project: 'test') }
           let(:action) { 'create' }
           let(:record) { { 'id' => 1, 'name' => 'Test' } }
           let(:filter) { instance_double(ForestAdminDatasourceToolkit::Components::Query::Filter) }
diff --git a/packages/forest_admin_datasource_customizer/spec/spec_helper.rb b/packages/forest_admin_datasource_customizer/spec/spec_helper.rb
index f76e472a0..62c1c01e0 100644
--- a/packages/forest_admin_datasource_customizer/spec/spec_helper.rb
+++ b/packages/forest_admin_datasource_customizer/spec/spec_helper.rb
@@ -7,6 +7,8 @@
 require 'forest_admin_test_toolkit'
 require 'filecache'
 require 'singleton'
+require 'active_support/isolated_execution_state'
+require 'active_support/notifications'
 
 SimpleCov.formatters = [SimpleCov::Formatter::JSONFormatter, SimpleCov::Formatter::HTMLFormatter]
 SimpleCov.start do
diff --git a/packages/forest_admin_datasource_toolkit/lib/forest_admin_datasource_toolkit/components/caller.rb b/packages/forest_admin_datasource_toolkit/lib/forest_admin_datasource_toolkit/components/caller.rb
index 183e6b5ea..0123fa4cd 100644
--- a/packages/forest_admin_datasource_toolkit/lib/forest_admin_datasource_toolkit/components/caller.rb
+++ b/packages/forest_admin_datasource_toolkit/lib/forest_admin_datasource_toolkit/components/caller.rb
@@ -1,7 +1,8 @@
 module ForestAdminDatasourceToolkit
   module Components
     class Caller
-      attr_reader :id, :email, :first_name, :last_name, :tags, :team, :rendering_id, :timezone, :permission_level, :role
+      attr_reader :id, :email, :first_name, :last_name, :tags, :team, :rendering_id, :timezone, :permission_level,
+                  :role, :project
 
       def initialize(
         id:,
diff --git a/packages/forest_admin_datasource_toolkit/lib/forest_admin_datasource_toolkit/monitoring.rb b/packages/forest_admin_datasource_toolkit/lib/forest_admin_datasource_toolkit/monitoring.rb
new file mode 100644
index 000000000..41a24b8ab
--- /dev/null
+++ b/packages/forest_admin_datasource_toolkit/lib/forest_admin_datasource_toolkit/monitoring.rb
@@ -0,0 +1,24 @@
+require 'active_support/isolated_execution_state'
+require 'active_support/notifications'
+
+module ForestAdminDatasourceToolkit
+  # Backend-agnostic instrumentation seam. Emits ActiveSupport::Notifications
+  # events under the "*.forest_admin" namespace so host apps can subscribe and
+  # forward to any monitoring stack. No-op cost when nobody subscribes.
+  module Monitoring
+    # Uniform entry point, callable from anywhere (decorator, utility class, plain
+    # object, or a client's custom handler). Pass `caller:` to auto-merge the acting
+    # user's non-PII identity (user_id/rendering_id/project) into the payload.
+    def self.instrument(event, payload = {}, caller: nil, &block)
+      enriched = payload.merge(caller_payload(caller)).compact
+      ActiveSupport::Notifications.instrument("#{event}.forest_admin", enriched, &block)
+    end
+
+    # Non-PII identity of the acting Forest user, to merge into an event payload.
+    def self.caller_payload(caller)
+      return {} unless caller
+
+      { user_id: caller.id, rendering_id: caller.rendering_id, project: caller.project }
+    end
+  end
+end
diff --git a/packages/forest_admin_rails/lib/forest_admin_rails.rb b/packages/forest_admin_rails/lib/forest_admin_rails.rb
index 2606f91be..51553c60f 100644
--- a/packages/forest_admin_rails/lib/forest_admin_rails.rb
+++ b/packages/forest_admin_rails/lib/forest_admin_rails.rb
@@ -34,6 +34,7 @@ module ForestAdminRails
   setting :disable_route_cache, default: false
   setting :rpc_max_polling_threads, default: nil
   setting :workflow_executor_url, default: nil
+  setting :monitoring, default: {} # opt-in log subscriber; see ForestAdminRails::Monitoring::DEFAULTS
 
   if defined?(Rails::Railtie)
     # logic for cors middleware,... here // or it might be into Engine
diff --git a/packages/forest_admin_rails/lib/forest_admin_rails/engine.rb b/packages/forest_admin_rails/lib/forest_admin_rails/engine.rb
index ced010c7c..59da0e0e0 100644
--- a/packages/forest_admin_rails/lib/forest_admin_rails/engine.rb
+++ b/packages/forest_admin_rails/lib/forest_admin_rails/engine.rb
@@ -28,6 +28,13 @@ class Engine < ::Rails::Engine
       Rails.error.subscribe(ForestAdminErrorSubscriber.new)
     end
 
+    # Runs after the host's config/initializers (where `config.monitoring` is set)
+    # but before the middleware stack is built, so the correlation middleware can
+    # still be inserted. No-op unless monitoring is enabled.
+    initializer 'forest_admin_rails.monitoring', after: :load_config_initializers do |app|
+      ForestAdminRails::Monitoring.install!(app)
+    end
+
     config.after_initialize do
       Rails.error.handle(ForestAdminDatasourceToolkit::Exceptions::ForestException) do
         agent_factory = ForestAdminAgent::Builder::AgentFactory.instance
diff --git a/packages/forest_admin_rails/lib/forest_admin_rails/monitoring.rb b/packages/forest_admin_rails/lib/forest_admin_rails/monitoring.rb
new file mode 100644
index 000000000..7a0bc1727
--- /dev/null
+++ b/packages/forest_admin_rails/lib/forest_admin_rails/monitoring.rb
@@ -0,0 +1,209 @@
+require 'json'
+require 'logger'
+require 'active_support/notifications'
+require 'active_support/isolated_execution_state'
+require 'active_support/core_ext/string/filters'
+
+module ForestAdminRails
+  # Opt-in log subscriber for Forest agent monitoring events.
+  #
+  # The agent only *emits* ActiveSupport::Notifications (`*.forest_admin`); this
+  # is a convenience sink that turns them into structured log lines, so most
+  # clients get monitoring by flipping one config flag instead of writing a
+  # subscriber. Ships disabled. Enable via:
+  #
+  #   ForestAdminRails.configure do |config|
+  #     config.monitoring = { enabled: true }   # see DEFAULTS for all options
+  #   end
+  #
+  # Output defaults to STDOUT + JSON tagged with "source":"forest_admin", so it
+  # is auto-collected by Datadog/CloudWatch/k8s and filterable even when mixed
+  # with the Rails log. Point `output` at a file path or your own Logger to keep
+  # it separate. Advanced backends (StatsD, Sentry, OTel) subscribe in code.
+  module Monitoring
+    DEFAULTS = {
+      enabled: false,
+      output: :stdout,        # :stdout | "path/to.log" (rotated) | a Logger instance
+      format: :json,          # :json | :text
+      ignore: %w[hook],       # event short-names to drop (name without ".forest_admin")
+      sql_level: 'off',       # off (group by query name) | medium (by SQL shape) | full (per query)
+      sql_truncate: 200,      # max SQL length shown at the :medium level
+      sql_summary_top: 15,    # distinct queries listed per request summary
+      slow_threshold_ms: 0,   # only log forest events at least this slow
+      source: 'forest_admin'  # discriminator field, so mixed streams stay filterable
+    }.freeze
+
+    # Carries Rails' X-Request-Id onto a thread-local so every event of a request
+    # shares one correlation id (also matching Rails / load-balancer logs).
+    class RequestTagger
+      def initialize(app)
+        @app = app
+      end
+
+      def call(env)
+        Thread.current[:forest_request_id] = env['action_dispatch.request_id']
+        @app.call(env)
+      ensure
+        Thread.current[:forest_request_id] = nil
+      end
+    end
+
+    class << self
+      # Called from the engine at boot. Reads config, and if enabled wires the
+      # correlation middleware, a logger, and the notification subscribers.
+      def install!(app)
+        config = DEFAULTS.merge((ForestAdminRails.config[:monitoring] || {}).transform_keys(&:to_sym))
+        return unless config[:enabled]
+        return if @installed
+
+        @installed = true
+        insert_middleware(app)
+        subscribe!(build_logger(config[:output]), config)
+      end
+
+      # Registers the subscribers against a given logger. Returns the subscriber
+      # handles so callers (and tests) can tear them down. Kept app-free so it is
+      # unit-testable without booting Rails.
+      def subscribe!(logger, options = {})
+        config = DEFAULTS.merge(options.transform_keys(&:to_sym))
+        ignore = config[:ignore].map(&:to_s)
+
+        handles = []
+        handles << subscribe_events(logger, config, ignore)
+        handles << subscribe_request_scope(logger, config)
+        handles << subscribe_sql(logger, config)
+        handles
+      end
+
+      private
+
+      def subscribe_events(logger, config, ignore)
+        ActiveSupport::Notifications.subscribe(/\.forest_admin$/) do |*args|
+          event = ActiveSupport::Notifications::Event.new(*args)
+          short = event.name.delete_suffix('.forest_admin')
+          next if ignore.include?(short)
+          next if event.duration < config[:slow_threshold_ms]
+
+          write(logger, config, name: event.name, duration_ms: event.duration,
+                                payload: event.payload.except(:exception, :exception_object),
+                                error: event.payload[:exception_object])
+        end
+      end
+
+      # Scopes SQL logging to Forest requests (start fires before any nested SQL)
+      # and flushes the per-request SQL summary on finish for the off/medium tiers.
+      def subscribe_request_scope(logger, config)
+        ActiveSupport::Notifications.subscribe('request.forest_admin', RequestScope.new(logger, config))
+      end
+
+      def subscribe_sql(logger, config)
+        full = config[:sql_level].to_s == 'full'
+
+        ActiveSupport::Notifications.subscribe('sql.active_record') do |*args|
+          event = ActiveSupport::Notifications::Event.new(*args)
+          next unless Thread.current[:forest_in_request]
+          next if event.payload[:name] == 'SCHEMA' || event.payload[:cached]
+
+          if full
+            write(logger, config, name: 'sql.active_record', duration_ms: event.duration,
+                                  payload: { name: event.payload[:name], sql: event.payload[:sql].to_s.squish })
+          else
+            acc = (Thread.current[:forest_sql_acc] ||= {})
+            key = if config[:sql_level].to_s == 'medium'
+                    event.payload[:sql].to_s.squish[0, config[:sql_truncate]]
+                  else
+                    event.payload[:name] || 'SQL'
+                  end
+            entry = (acc[key] ||= { count: 0, ms: 0.0 })
+            entry[:count] += 1
+            entry[:ms] += event.duration
+          end
+        end
+      end
+
+      # Emits one line in the configured format, tagged with the source so a mixed
+      # stream stays filterable.
+      def write(logger, config, event)
+        request_id = Thread.current[:forest_request_id]
+        name = event[:name]
+        duration_ms = event[:duration_ms]
+        payload = event[:payload] || {}
+        error = event[:error]
+
+        if config[:format].to_s == 'text'
+          line = "#{name.to_s.ljust(28)} #{duration_ms.round(2)}ms [#{request_id || "-"}] #{payload.inspect}"
+          line += " ERROR=#{error.class}: #{error.message}" if error
+          logger.info(line)
+        else
+          data = { source: config[:source], event: name, duration_ms: duration_ms.round(2),
+                   request_id: request_id }.merge(payload)
+          data[:error] = "#{error.class}: #{error.message}" if error
+          logger.info(JSON.generate(data.compact))
+        end
+      end
+
+      def build_logger(output)
+        case output
+        when Logger then output
+        when String then formatted(Logger.new(log_path(output), 5, 100 * 1024 * 1024))
+        else formatted(Logger.new($stdout))
+        end
+      end
+
+      # We pass fully-formatted messages (a JSON string or a text line), so strip
+      # Logger's default severity/timestamp prefix.
+      def formatted(logger)
+        logger.formatter = proc { |_severity, _time, _progname, msg| "#{msg}\n" }
+        logger
+      end
+
+      def log_path(path)
+        defined?(Rails) && Rails.respond_to?(:root) && Rails.root ? Rails.root.join(path) : path
+      end
+
+      def insert_middleware(app)
+        return unless app&.config&.middleware
+
+        app.config.middleware.insert_after(ActionDispatch::RequestId, RequestTagger)
+      rescue StandardError
+        app.config.middleware.use(RequestTagger)
+      end
+    end
+
+    # Object subscriber: needs start/finish (not just finish), to bracket the
+    # request's SQL and flush its summary.
+    class RequestScope
+      def initialize(logger, config)
+        @logger = logger
+        @config = config
+        @summarise = config[:sql_level].to_s != 'full'
+      end
+
+      def start(_name, _id, _payload)
+        Thread.current[:forest_in_request] = true
+        Thread.current[:forest_sql_acc] = {} if @summarise
+      end
+
+      def finish(_name, _id, _payload)
+        Thread.current[:forest_in_request] = false
+        acc = Thread.current[:forest_sql_acc]
+        Thread.current[:forest_sql_acc] = nil
+        flush(acc) if @summarise && acc && !acc.empty?
+      end
+
+      private
+
+      def flush(acc)
+        ranked = acc.sort_by { |_key, v| -v[:count] }
+        top = ranked.first(@config[:sql_summary_top])
+        payload = {
+          queries: acc.values.sum { |v| v[:count] },
+          dropped: [ranked.size - top.size, 0].max,
+          breakdown: top.map { |key, v| { query: key, count: v[:count], ms: v[:ms].round(2) } }
+        }
+        total_ms = acc.values.sum { |v| v[:ms] }
+        Monitoring.send(:write, @logger, @config, name: 'sql.summary', duration_ms: total_ms, payload: payload)
+      end
+    end
+  end
+end
diff --git a/packages/forest_admin_rails/lib/generators/forest_admin_rails/templates/initializers/config.rb b/packages/forest_admin_rails/lib/generators/forest_admin_rails/templates/initializers/config.rb
index f21565868..585600a49 100644
--- a/packages/forest_admin_rails/lib/generators/forest_admin_rails/templates/initializers/config.rb
+++ b/packages/forest_admin_rails/lib/generators/forest_admin_rails/templates/initializers/config.rb
@@ -1,4 +1,16 @@
 ForestAdminRails.configure do |config|
   config.auth_secret = '<%= @auth_secret %>'
   config.env_secret = '<%= @env_secret %>'
+
+  # Monitoring — log what the agent does (request latency, slow smart fields,
+  # actions, hooks, SQL). Disabled by default. Uncomment to enable; output is
+  # JSON on STDOUT (auto-collected by Datadog/CloudWatch/k8s) unless you point
+  # `output` at a file path or your own Logger.
+  # config.monitoring = {
+  #   enabled: true,
+  #   output: :stdout,        # :stdout | "log/forest_admin_monitoring.log" | a Logger
+  #   format: :json,          # :json | :text
+  #   sql_level: 'off',       # off | medium | full (full = one line per query; use temporarily)
+  #   slow_threshold_ms: 0    # only log events at least this slow
+  # }
 end
diff --git a/packages/forest_admin_rails/spec/lib/forest_admin_rails/monitoring_spec.rb b/packages/forest_admin_rails/spec/lib/forest_admin_rails/monitoring_spec.rb
new file mode 100644
index 000000000..d686635ba
--- /dev/null
+++ b/packages/forest_admin_rails/spec/lib/forest_admin_rails/monitoring_spec.rb
@@ -0,0 +1,86 @@
+require 'spec_helper'
+require 'json'
+require 'stringio'
+require 'active_support'
+require 'active_support/core_ext/string/filters'
+require_relative '../../../lib/forest_admin_rails/monitoring'
+
+module ForestAdminRails
+  RSpec.describe Monitoring do
+    let(:io) { StringIO.new }
+    let(:logger) do
+      Logger.new(io).tap { |l| l.formatter = proc { |_s, _t, _p, msg| "#{msg}\n" } }
+    end
+    let(:handles) { [] }
+
+    after { handles.flatten.each { |h| ActiveSupport::Notifications.unsubscribe(h) } }
+
+    def lines
+      io.string.each_line.map(&:strip).reject(&:empty?)
+    end
+
+    it 'logs a forest event as tagged JSON with duration and payload' do
+      handles.concat(described_class.subscribe!(logger, format: :json))
+
+      ActiveSupport::Notifications.instrument('request.forest_admin', collection: 'user', id: '42') { nil }
+
+      data = JSON.parse(lines.grep(/request\.forest_admin/).first)
+      expect(data).to include(
+        'source' => 'forest_admin', 'event' => 'request.forest_admin', 'collection' => 'user', 'id' => '42'
+      )
+      expect(data['duration_ms']).to be >= 0
+    end
+
+    it 'drops ignored events (hooks by default)' do
+      handles.concat(described_class.subscribe!(logger))
+
+      ActiveSupport::Notifications.instrument('hook.forest_admin', collection: 'user', operation: 'Create') { nil }
+
+      expect(io.string).not_to include('hook.forest_admin')
+    end
+
+    it 'attaches the exception when an operation raises' do
+      handles.concat(described_class.subscribe!(logger, format: :json))
+
+      expect do
+        ActiveSupport::Notifications.instrument('action.forest_admin', collection: 'user', action: 'ban') { raise 'boom' }
+      end.to raise_error('boom')
+
+      data = JSON.parse(lines.grep(/action\.forest_admin/).first)
+      expect(data['error']).to eq('RuntimeError: boom')
+    end
+
+    it 'summarises SQL per request grouped by query name (off level)' do
+      handles.concat(described_class.subscribe!(logger, sql_level: 'off'))
+
+      ActiveSupport::Notifications.instrument('request.forest_admin', collection: 'user') do
+        3.times { ActiveSupport::Notifications.instrument('sql.active_record', name: 'Subscription Load', sql: 'SELECT 1') { nil } }
+        ActiveSupport::Notifications.instrument('sql.active_record', name: 'SCHEMA', sql: 'x') { nil } # skipped
+        ActiveSupport::Notifications.instrument('sql.active_record', name: 'User Load', sql: 'SELECT 2', cached: true) { nil } # skipped
+      end
+
+      summary = JSON.parse(lines.grep(/sql\.summary/).first)
+      expect(summary['queries']).to eq(3)
+      expect(summary['breakdown']).to include(include('query' => 'Subscription Load', 'count' => 3))
+    end
+
+    it 'logs each query in full mode instead of summarising' do
+      handles.concat(described_class.subscribe!(logger, sql_level: 'full'))
+
+      ActiveSupport::Notifications.instrument('request.forest_admin', collection: 'user') do
+        2.times { ActiveSupport::Notifications.instrument('sql.active_record', name: 'User Load', sql: 'SELECT 1') { nil } }
+      end
+
+      expect(lines.grep(/sql\.active_record/).size).to eq(2)
+      expect(io.string).not_to include('sql.summary')
+    end
+
+    it 'does not log SQL that runs outside a forest request' do
+      handles.concat(described_class.subscribe!(logger, sql_level: 'full'))
+
+      ActiveSupport::Notifications.instrument('sql.active_record', name: 'User Load', sql: 'SELECT 1') { nil }
+
+      expect(io.string).not_to include('sql.active_record')
+    end
+  end
+end