diff --git a/src/lib/diff/tree-mutator.hpp b/src/lib/diff/tree-mutator.hpp
index b7a5120bc..0fd5ab3f0 100644
--- a/src/lib/diff/tree-mutator.hpp
+++ b/src/lib/diff/tree-mutator.hpp
@@ -385,6 +385,9 @@ namespace diff{
         template<class CLO>
         using Change = ChangeOperation<PAR,CLO>;
         
+        template<class CLO>
+        using MutateAttrib = MutationOperation<PAR,CLO>;
+        
         template<class BIN>
         using Collection = ChildCollectionMutator<PAR,BIN>;
         
@@ -419,6 +422,17 @@ namespace diff{
             return Change<CLO> (attributeID, setterClosure, move(*this));
           }
         
+        ///////////////////////////////////////TODO documentation
+        template<typename CLO>
+        Builder<MutateAttrib<CLO>>
+        mutateAttrib (Symbol attributeID, CLO mutatorBuilderClosure)
+          {
+            idi::EntryID<Rec> key{attributeID};
+            return MutateAttrib<CLO> (key, mutatorBuilderClosure, move(*this));
+          }
+        
+        ///////////////////////////////////////TODO define variant taking a GenNode::ID
+        
         /** set up a binding to a structure of "child objects",
          *  implemented through a typical STL container
          * @param collectionBindingSetup as created by invoking a nested DSL,
diff --git a/tests/library/diff/tree-mutator-binding-test.cpp b/tests/library/diff/tree-mutator-binding-test.cpp
index f94dc0abe..8a782a732 100644
--- a/tests/library/diff/tree-mutator-binding-test.cpp
+++ b/tests/library/diff/tree-mutator-binding-test.cpp
@@ -833,6 +833,19 @@ namespace test{
               {
                 LOG_SETTER ("gamma")
                 gamma = val;
+              })
+            .mutateAttrib("δ", [&](TreeMutator::MutatorBuffer buff)
+              {
+                // NOTE: we use "implementation inside knowledge" regarding the nested scope,
+                //       which is here represented as TestMutationTarget
+                buff.create (
+                  TreeMutator::build()
+                    .attachDummy (delta));
+                
+                // NOTE: when this closure is invoked, we're about to open the sub scope,
+                //       while mutation has not happened yet
+                cout << "openSub()...\n"
+                     << join(delta.getLog(), "\n") <<endl;
               });
           
 #if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
@@ -871,6 +884,7 @@ namespace test{
           // It is implemented as `TestMutationTarget delta`, which allows us to verify a fully operational nested mutator.
           
           const size_t BUFF_SIZ = sizeof(TreeMutator::build().attachDummy (delta));
+          // just use some suitable size, not the point in focus for this test
           
           InPlaceBuffer<TreeMutator, BUFF_SIZ> subMutatorBuffer;
           TreeMutator::MutatorBuffer placementHandle(subMutatorBuffer);
@@ -889,7 +903,9 @@ namespace test{
           
           CHECK (not isnil (delta));                      // ...and "magically" these instructions happened to insert
           cout << "Sub|" << delta.showContent() <<endl;  //  some new content into our implementation defined sub scope!
-          cout << delta <<endl;
+          cout << "____Mutation-Log(nested)______\n"
+               << join(delta.getLog(), "\n")
+               << "\n───╼━━━━━━━━━╾────────────────"<<endl;
           
           // verify contents of nested scope after mutation
           CHECK (delta.showContent() == "type = ξ, β = 2, b, a");
diff --git a/wiki/renderengine.html b/wiki/renderengine.html
index cde57af36..cf3da5509 100644
--- a/wiki/renderengine.html
+++ b/wiki/renderengine.html
@@ -8214,7 +8214,7 @@ On receiving the terms of this &quot;diff language&quot;, it is possible to gene
 i.e. a ''unified diff'' or the ''predicate notation'' used above to describe the list diffing algorithm, just by accumulating changes.
 </pre>
 </div>
-<div title="TreeMutator" creator="Ichthyostega" modifier="Ichthyostega" created="201503292115" modified="201606041215" tags="Model Concepts GuiPattern design draft" changecount="86">
+<div title="TreeMutator" creator="Ichthyostega" modifier="Ichthyostega" created="201503292115" modified="201606051455" tags="Model Concepts GuiPattern design draft" changecount="87">
 <pre>The TreeMutator is an intermediary to translate a generic structure pattern into heterogeneous local invocation sequences.
 within the [[diff framework|TreeDiffModel]], this is a crucial joint, since here the abstract, generic, ~DOM-like ExternalTreeDescription meeds opaque, local and undisclosed data structures.
 
@@ -8341,13 +8341,13 @@ attached to a clip, or the mixture of clips, effects and labels found within a [
 :any re-ordering, inserting and deleting of fields is ''prohibited'', while defaultable optional fields are tolerated
 :there is only one common »binding layer« for object fields (i.e. we don't offer a customisable selector)
 :binding is created ''alternatively'' through the following closures
-:* &quot;key&quot;, lambda {{{change: void(T val)}}}
+:* ''change'': &quot;key&quot;, setter lambda {{{void(T val)}}}
 :** binding for a regular setter to assign a new value
 :** the value type is picked up from the provided lambda
 :** possible value types are restricted to the selection of GenNode payload types
 :** any further type conversions are to be handled by the closure and thus the client code
-:* &quot;key&quot;, lambda {{{mutateAttrib: void(TreeMutator::MutatorBuffer)}}}
-:** fabricate a recursive sub-TreeMutator to handle an &quot;object valued&quot; attribute
+:* ''mutateAttrib'': &quot;key&quot;, mutator-builder lambda {{{void(TreeMutator::MutatorBuffer)}}}
+:** fabricate a recursive sub-TreeMutator to handle an //object valued// attribute
 :** implicit typing -- the fabricated sub-TreeMutator just needs to be able to deal with the bound attribute
 
 
diff --git a/wiki/thinkPad.ichthyo.mm b/wiki/thinkPad.ichthyo.mm
index bfe9777c2..ff4758d47 100644
--- a/wiki/thinkPad.ichthyo.mm
+++ b/wiki/thinkPad.ichthyo.mm
@@ -4173,6 +4173,26 @@
 </richcontent>
 <icon BUILTIN="idea"/>
 </node>
+<node CREATED="1465139405203" ID="ID_103737978" MODIFIED="1465139492329" TEXT="...hey, der Typ ist implizit klar! es ist immer Rec">
+<richcontent TYPE="NOTE"><html>
+  <head>
+    
+  </head>
+  <body>
+    <p>
+      ...die offensichtlichsten Dinge &#252;bersieht man nur zu leicht!!!!!
+    </p>
+    <p>
+      Da es ein nested scope ist, ist es immer ein Objekt,
+    </p>
+    <p>
+      also repr&#228;sentiert als Rec&lt;GenNode&gt;
+    </p>
+  </body>
+</html>
+</richcontent>
+<icon BUILTIN="idea"/>
+</node>
 </node>
 </node>
 </node>