diff --git a/src/common/generators/generators.h b/src/common/generators/generators.h
index c8c0c1b2..96d967ce 100644
--- a/src/common/generators/generators.h
+++ b/src/common/generators/generators.h
@@ -359,6 +359,8 @@ std::unique_ptr<DiagramModel> generate(const common::compilation_database &db,
 
     diagram->set_complete(true);
 
+    diagram->finalize();
+
     return diagram;
 }
 
diff --git a/src/common/model/diagram.cc b/src/common/model/diagram.cc
index 907a3902..22f8e290 100644
--- a/src/common/model/diagram.cc
+++ b/src/common/model/diagram.cc
@@ -59,6 +59,8 @@ void diagram::set_complete(bool complete) { complete_ = complete; }
 
 bool diagram::complete() const { return complete_; }
 
+void diagram::finalize() { }
+
 bool diagram::should_include(const element &e) const
 {
     if (filter_.get() == nullptr)
diff --git a/src/common/model/diagram.h b/src/common/model/diagram.h
index ae78914a..61b10bde 100644
--- a/src/common/model/diagram.h
+++ b/src/common/model/diagram.h
@@ -124,12 +124,24 @@ public:
     void set_complete(bool complete);
 
     /**
-     * Whether the diagram is complete.
+     * @brief Whether the diagram is complete.
+     *
+     * This flag is set to true, when all translation units for this diagram
+     * have been visited.
      *
      * @return Diagram completion status.
      */
     bool complete() const;
 
+    /**
+     * @brief Once the diagram is complete, run any final processing.
+     *
+     * This method should be overriden by specific diagram models to do some
+     * final tasks like cleaning up the model (e.g. some filters only work
+     * on completed diagrams).
+     */
+    virtual void finalize();
+
     // TODO: refactor to a template method
     bool should_include(const element &e) const;
     bool should_include(const namespace_ &ns) const;
diff --git a/src/common/model/diagram_filter.cc b/src/common/model/diagram_filter.cc
index 98a03cf9..560a427a 100644
--- a/src/common/model/diagram_filter.cc
+++ b/src/common/model/diagram_filter.cc
@@ -376,6 +376,7 @@ tvl::value_t callee_filter::match(
     const diagram &d, const sequence_diagram::model::participant &p) const
 {
     using sequence_diagram::model::class_;
+    using sequence_diagram::model::function;
     using sequence_diagram::model::method;
     using sequence_diagram::model::participant;
 
@@ -391,6 +392,10 @@ tvl::value_t callee_filter::match(
 
     tvl::value_t res = tvl::any_of(
         callee_types_.begin(), callee_types_.end(), [&p, is_lambda](auto ct) {
+            auto is_function = [](const participant *p) {
+                return dynamic_cast<const function *>(p) != nullptr;
+            };
+
             switch (ct) {
             case config::callee_type::method:
                 return p.type_name() == "method";
@@ -401,12 +406,12 @@ tvl::value_t callee_filter::match(
                 return p.type_name() == "method" &&
                     ((method &)p).is_assignment();
             case config::callee_type::operator_:
-                return p.type_name() == "method" && ((method &)p).is_operator();
+                return is_function(&p) && ((function &)p).is_operator();
             case config::callee_type::defaulted:
                 return p.type_name() == "method" &&
                     ((method &)p).is_defaulted();
             case config::callee_type::static_:
-                return p.type_name() == "method" && ((method &)p).is_static();
+                return is_function(&p) && ((function &)p).is_static();
             case config::callee_type::function:
                 return p.type_name() == "function";
             case config::callee_type::function_template:
diff --git a/src/sequence_diagram/generators/json/sequence_diagram_generator.cc b/src/sequence_diagram/generators/json/sequence_diagram_generator.cc
index 1c0e7d84..33f298cb 100644
--- a/src/sequence_diagram/generators/json/sequence_diagram_generator.cc
+++ b/src/sequence_diagram/generators/json/sequence_diagram_generator.cc
@@ -252,16 +252,6 @@ nlohmann::json &generator::current_block_statement() const
 void generator::process_call_message(const model::message &m,
     std::vector<common::model::diagram_element::id_t> &visited) const
 {
-    const auto &to = m_model.get_participant<model::participant>(m.to());
-
-    if (!to || to.value().skip())
-        return;
-
-    if (!m_model.should_include(to.value())) {
-        LOG_DBG("Excluding call from '{}' to '{}'", m.from(), m.to());
-        return;
-    }
-
     visited.push_back(m.from());
 
     LOG_DBG("Generating message {} --> {}", m.from(), m.to());
diff --git a/src/sequence_diagram/generators/plantuml/sequence_diagram_generator.cc b/src/sequence_diagram/generators/plantuml/sequence_diagram_generator.cc
index 3d59ac90..03b31fb4 100644
--- a/src/sequence_diagram/generators/plantuml/sequence_diagram_generator.cc
+++ b/src/sequence_diagram/generators/plantuml/sequence_diagram_generator.cc
@@ -139,14 +139,6 @@ void generator::generate_activity(const activity &a, std::ostream &ostr,
         if (m.type() == message_t::kCall) {
             const auto &to =
                 m_model.get_participant<model::participant>(m.to());
-            if (!to || to.value().skip())
-                continue;
-
-            if (!m_model.should_include(to.value())) {
-                LOG_DBG("Excluding call from [{}] to {} [{}]", m.from(),
-                    to.value().full_name(false), m.to());
-                continue;
-            }
 
             visited.push_back(m.from());
 
diff --git a/src/sequence_diagram/model/diagram.cc b/src/sequence_diagram/model/diagram.cc
index b009d9f2..9cb1ed81 100644
--- a/src/sequence_diagram/model/diagram.cc
+++ b/src/sequence_diagram/model/diagram.cc
@@ -248,6 +248,81 @@ void diagram::fold_or_end_block_statement(message &&m,
         current_messages.emplace_back(std::move(m));
     }
 }
+
+void diagram::finalize()
+{
+    // Apply diagram filters and remove any empty block statements
+    using common::model::message_t;
+
+    // First in each sequence (activity) filter out any remaining
+    // uninteresting calls
+    for (auto &[id, act] : sequences_) {
+        util::erase_if(act.messages(), [this](auto &m) {
+            if (m.type() != message_t::kCall)
+                return false;
+
+            const auto &to = get_participant<model::participant>(m.to());
+            if (!to || to.value().skip())
+                return true;
+
+            if (!should_include(to.value())) {
+                LOG_DBG("Excluding call from [{}] to {} [{}]", m.from(),
+                    to.value().full_name(false), m.to());
+                return true;
+            }
+
+            return false;
+        });
+    }
+
+    // Now remove any empty block statements, e.g. if/endif
+    for (auto &[id, act] : sequences_) {
+        int64_t block_nest_level{0};
+        std::vector<std::vector<message>> block_message_stack;
+        // Add first stack level - this level will contain the filtered
+        // message sequence
+        block_message_stack.emplace_back();
+
+        // First create a recursive stack from the messages and
+        // message blocks (e.g. if statements)
+        for (auto &m : act.messages()) {
+            if (is_begin_block_message(m.type())) {
+                block_nest_level++;
+                block_message_stack.push_back({m});
+            }
+            else if (is_end_block_message(m.type())) {
+                block_nest_level--;
+
+                block_message_stack.back().push_back(m);
+
+                // Check the last stack for any calls, if yes, collapse it
+                // on the previous stack
+                if (std::count_if(block_message_stack.back().begin(),
+                        block_message_stack.back().end(), [](auto &m) {
+                            return m.type() == message_t::kCall;
+                        }) > 0) {
+                    std::copy(block_message_stack.back().begin(),
+                        block_message_stack.back().end(),
+                        std::back_inserter(
+                            block_message_stack.at(block_nest_level)));
+                }
+
+                block_message_stack.pop_back();
+
+                assert(block_nest_level >= 0);
+            }
+            else {
+                block_message_stack.back().push_back(m);
+            }
+        }
+
+        act.messages().clear();
+
+        for (auto &m : block_message_stack[0]) {
+            act.add_message(m);
+        }
+    }
+}
 } // namespace clanguml::sequence_diagram::model
 
 namespace clanguml::common::model {
diff --git a/src/sequence_diagram/model/diagram.h b/src/sequence_diagram/model/diagram.h
index 78ca2fdf..d5bf0f20 100644
--- a/src/sequence_diagram/model/diagram.h
+++ b/src/sequence_diagram/model/diagram.h
@@ -212,6 +212,15 @@ public:
      */
     bool should_include(const sequence_diagram::model::participant &p) const;
 
+    /**
+     * @brief Once the diagram is complete, run any final processing.
+     *
+     * This method should be overriden by specific diagram models to do some
+     * final tasks like cleaning up the model (e.g. some filters only work
+     * on completed diagrams).
+     */
+    void finalize() override;
+
 private:
     /**
      * This method checks the last messages in sequence (current_messages),
@@ -233,6 +242,27 @@ private:
         common::model::message_t statement_begin,
         std::vector<message> &current_messages) const;
 
+    bool is_begin_block_message(common::model::message_t mt)
+    {
+        using common::model::message_t;
+        static std::set<message_t> block_begin_types{message_t::kIf,
+            message_t::kWhile, message_t::kDo, message_t::kFor, message_t::kTry,
+            message_t::kSwitch, message_t::kConditional};
+
+        return block_begin_types.count(mt) > 0;
+    };
+
+    bool is_end_block_message(common::model::message_t mt)
+    {
+        using common::model::message_t;
+        static std::set<message_t> block_end_types{message_t::kIfEnd,
+            message_t::kWhileEnd, message_t::kDoEnd, message_t::kForEnd,
+            message_t::kTryEnd, message_t::kSwitchEnd,
+            message_t::kConditionalEnd};
+
+        return block_end_types.count(mt) > 0;
+    };
+
     bool started_{false};
 
     std::map<common::model::diagram_element::id_t, activity> sequences_;
diff --git a/src/sequence_diagram/model/participant.cc b/src/sequence_diagram/model/participant.cc
index f189bcd9..3772b891 100644
--- a/src/sequence_diagram/model/participant.cc
+++ b/src/sequence_diagram/model/participant.cc
@@ -143,6 +143,10 @@ bool function::is_static() const { return is_static_; }
 
 void function::is_static(bool s) { is_static_ = s; }
 
+bool function::is_operator() const { return is_operator_; }
+
+void function::is_operator(bool o) { is_operator_ = o; }
+
 void function::add_parameter(const std::string &a) { parameters_.push_back(a); }
 
 const std::vector<std::string> &function::parameters() const
@@ -176,10 +180,6 @@ bool method::is_assignment() const { return is_assignment_; }
 
 void method::is_assignment(bool a) { is_assignment_ = a; }
 
-bool method::is_operator() const { return is_operator_; }
-
-void method::is_operator(bool o) { is_operator_ = o; }
-
 void method::set_method_name(const std::string &name) { method_name_ = name; }
 
 void method::set_class_id(diagram_element::id_t id) { class_id_ = id; }
diff --git a/src/sequence_diagram/model/participant.h b/src/sequence_diagram/model/participant.h
index f7d710cd..7cf80cd1 100644
--- a/src/sequence_diagram/model/participant.h
+++ b/src/sequence_diagram/model/participant.h
@@ -277,6 +277,20 @@ struct function : public participant {
      */
     void is_static(bool s);
 
+    /**
+     * @brief Check, if the method is an operator
+     *
+     * @return True, if the method is an operator
+     */
+    bool is_operator() const;
+
+    /**
+     * @brief Set whether the method is an operator
+     *
+     * @param v True, if the method is an operator
+     */
+    void is_operator(bool o);
+
     /**
      * @brief Add a function parameter
      *
@@ -298,6 +312,7 @@ private:
     bool is_const_{false};
     bool is_void_{false};
     bool is_static_{false};
+    bool is_operator_{false};
     std::vector<std::string> parameters_;
 };
 
@@ -429,20 +444,6 @@ struct method : public function {
      */
     void is_assignment(bool a);
 
-    /**
-     * @brief Check, if the method is an operator
-     *
-     * @return True, if the method is an operator
-     */
-    bool is_operator() const;
-
-    /**
-     * @brief Set whether the method is an operator
-     *
-     * @param v True, if the method is an operator
-     */
-    void is_operator(bool o);
-
 private:
     diagram_element::id_t class_id_{};
     std::string method_name_;
@@ -450,7 +451,6 @@ private:
     bool is_constructor_{false};
     bool is_defaulted_{false};
     bool is_assignment_{false};
-    bool is_operator_{false};
 };
 
 /**
diff --git a/src/sequence_diagram/visitor/translation_unit_visitor.cc b/src/sequence_diagram/visitor/translation_unit_visitor.cc
index 4136e698..c295bfea 100644
--- a/src/sequence_diagram/visitor/translation_unit_visitor.cc
+++ b/src/sequence_diagram/visitor/translation_unit_visitor.cc
@@ -330,6 +330,8 @@ bool translation_unit_visitor::VisitFunctionDecl(
 
     function_model_ptr->is_void(declaration->getReturnType()->isVoidType());
 
+    function_model_ptr->is_operator(declaration->isOverloadedOperator());
+
     context().update(declaration);
 
     context().set_caller_id(function_model_ptr->id());
@@ -373,6 +375,9 @@ bool translation_unit_visitor::VisitFunctionTemplateDecl(
     function_template_model->set_id(
         common::to_id(function_template_model->full_name(false)));
 
+    function_template_model->is_operator(
+        declaration->getAsFunction()->isOverloadedOperator());
+
     context().update(declaration);
 
     context().set_caller_id(function_template_model->id());
@@ -2260,6 +2265,7 @@ void translation_unit_visitor::finalize()
 {
     std::set<common::model::diagram_element::id_t> active_participants_unique;
 
+    // Change all active participants AST local ids to diagram global ids
     for (auto id : diagram().active_participants()) {
         if (local_ast_id_map_.find(id) != local_ast_id_map_.end()) {
             active_participants_unique.emplace(local_ast_id_map_.at(id));
@@ -2271,6 +2277,7 @@ void translation_unit_visitor::finalize()
 
     diagram().active_participants() = std::move(active_participants_unique);
 
+    // Change all message callees AST local ids to diagram global ids
     for (auto &[id, activity] : diagram().sequences()) {
         for (auto &m : activity.messages()) {
             if (local_ast_id_map_.find(m.to()) != local_ast_id_map_.end()) {
diff --git a/src/sequence_diagram/visitor/translation_unit_visitor.h b/src/sequence_diagram/visitor/translation_unit_visitor.h
index beb52f65..ed314b7b 100644
--- a/src/sequence_diagram/visitor/translation_unit_visitor.h
+++ b/src/sequence_diagram/visitor/translation_unit_visitor.h
@@ -252,7 +252,7 @@ public:
         int64_t local_id) const;
 
     /**
-     * @brief Finalize diagram model
+     * @brief Finalize diagram model for this translation unit
      */
     void finalize();
 
diff --git a/uml/sequence/class_diagram_generator_sequence.yml b/uml/sequence/class_diagram_generator_sequence.yml
index ffad3a03..6bb3c7a7 100644
--- a/uml/sequence/class_diagram_generator_sequence.yml
+++ b/uml/sequence/class_diagram_generator_sequence.yml
@@ -10,4 +10,4 @@ plantuml:
   before:
     - 'title clang-uml clanguml::class_diagram::generators::plantuml::generator sequence diagram'
 start_from:
-  - function: "clanguml::class_diagram::generators::plantuml::generator::generate(std::ostream &)"
\ No newline at end of file
+  - function: "clanguml::class_diagram::generators::plantuml::generator::generate(std::ostream &) const"
\ No newline at end of file
diff --git a/uml/sequence/cli_handle_options_sequence.yml b/uml/sequence/cli_handle_options_sequence.yml
index 8d146175..2aea8c7e 100644
--- a/uml/sequence/cli_handle_options_sequence.yml
+++ b/uml/sequence/cli_handle_options_sequence.yml
@@ -1,6 +1,7 @@
 type: sequence
 combine_free_functions_into_file_participants: true
 generate_method_arguments: none
+debug_mode: true
 glob:
   - src/cli/cli_handler.cc
   - src/config/config.cc
@@ -14,6 +15,8 @@ exclude:
     - r: "clanguml::config::option.*"
   paths:
     - src/util/util.h
+  callee_types:
+    - operator
 using_namespace:
   - clanguml
 start_from:
diff --git a/uml/sequence/diagram_generate_generic_sequence.yml b/uml/sequence/diagram_generate_generic_sequence.yml
index c6950c7c..257c97b7 100644
--- a/uml/sequence/diagram_generate_generic_sequence.yml
+++ b/uml/sequence/diagram_generate_generic_sequence.yml
@@ -7,12 +7,8 @@ using_namespace:
   - clanguml
 include:
   namespaces:
-    - clang
     - clanguml::common::generators
 exclude:
-  namespaces:
-    - clanguml::model::tvl
-    - clanguml::decorators
   paths:
     - src/common/model/source_location.h
 start_from: