diff --git a/src/Makefile.sources b/src/Makefile.sources
index a3fb92bac..14c6ed346 100644
--- a/src/Makefile.sources
+++ b/src/Makefile.sources
@@ -353,6 +353,7 @@ HB_SUBSET_sources = \
 	graph/gsubgpos-context.cc \
 	graph/pairpos-graph.hh \
 	graph/coverage-graph.hh \
+	graph/classdef-graph.hh \
 	graph/pairpos-graph.hh \
 	graph/serialize.hh \
 	$(NULL)
diff --git a/src/graph/classdef-graph.hh b/src/graph/classdef-graph.hh
new file mode 100644
index 000000000..e81cd6ec4
--- /dev/null
+++ b/src/graph/classdef-graph.hh
@@ -0,0 +1,141 @@
+/*
+ * Copyright © 2022  Google, Inc.
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Google Author(s): Garret Rieger
+ */
+
+#include "graph.hh"
+#include "../hb-ot-layout-common.hh"
+
+#ifndef GRAPH_CLASSDEF_GRAPH_HH
+#define GRAPH_CLASSDEF_GRAPH_HH
+
+namespace graph {
+
+struct ClassDefFormat1 : public OT::ClassDefFormat1_3<SmallTypes>
+{
+  bool sanitize (graph_t::vertex_t& vertex) const
+  {
+    int64_t vertex_len = vertex.obj.tail - vertex.obj.head;
+    constexpr unsigned min_size = OT::ClassDefFormat1_3<SmallTypes>::min_size;
+    if (vertex_len < min_size) return false;
+    return vertex_len >= min_size + classValue.get_size () - classValue.len.get_size ();
+  }
+};
+
+struct ClassDefFormat2 : public OT::ClassDefFormat2_4<SmallTypes>
+{
+  bool sanitize (graph_t::vertex_t& vertex) const
+  {
+    int64_t vertex_len = vertex.obj.tail - vertex.obj.head;
+    constexpr unsigned min_size = OT::ClassDefFormat2_4<SmallTypes>::min_size;
+    if (vertex_len < min_size) return false;
+    return vertex_len >= min_size + rangeRecord.get_size () - rangeRecord.len.get_size ();
+  }
+};
+
+struct ClassDef : public OT::ClassDef
+{
+  template<typename It>
+  static bool clone_class_def (gsubgpos_graph_context_t& c,
+                               unsigned class_def_id,
+                               unsigned new_parent_id,
+                               unsigned link_position,
+                               It glyphs)
+  {
+    unsigned class_def_size = c.graph.vertices_[class_def_id].table_size ();
+    auto& class_def_v = c.graph.vertices_[class_def_id];
+    ClassDef* class_def_table = (ClassDef*) class_def_v.obj.head;
+    if (!class_def_table->sanitize (class_def_v))
+      return false;
+
+    auto new_class_def =
+        + glyphs
+        | hb_map_retains_sorting ([&] (hb_codepoint_t gid) {
+          return hb_pair (gid, class_def_table[gid]);
+        })
+        ;
+
+    unsigned class_def_prime_id = c.graph.new_node (nullptr, nullptr);
+    auto& class_def_prime_vertex = c.graph.vertices_[class_def_prime_id];
+    if (!make_class_def (c, new_class_def, class_def_prime_id, class_def_size))
+      return false;
+
+    auto* class_def_link = c.graph.vertices_[new_parent_id].obj.real_links.push ();
+    class_def_link->width = SmallTypes::size;
+    class_def_link->objidx = class_def_prime_id;
+    class_def_link->position = link_position;
+    class_def_prime_vertex.parents.push (new_parent_id);
+
+    return true;
+  }
+
+  template<typename It>
+  static bool make_class_def (gsubgpos_graph_context_t& c,
+                              It glyph_and_class,
+                              unsigned dest_obj,
+                              unsigned max_size)
+  {
+    char* buffer = (char*) hb_calloc (1, max_size);
+    hb_serialize_context_t serializer (buffer, max_size);
+    ClassDef_serialize (&serializer, glyph_and_class);
+    serializer.end_serialize ();
+    if (serializer.in_error ())
+    {
+      hb_free (buffer);
+      return false;
+    }
+
+    hb_bytes_t class_def_copy = serializer.copy_bytes ();
+    c.add_buffer ((char *) class_def_copy.arrayZ); // Give ownership to the context, it will cleanup the buffer.
+
+    auto& obj = c.graph.vertices_[dest_obj].obj;
+    obj.head = (char *) class_def_copy.arrayZ;
+    obj.tail = obj.head + class_def_copy.length;
+
+    hb_free (buffer);
+    return true;
+  }
+
+  bool sanitize (graph_t::vertex_t& vertex) const
+  {
+    int64_t vertex_len = vertex.obj.tail - vertex.obj.head;
+    if (vertex_len < OT::ClassDef::min_size) return false;
+    switch (u.format)
+    {
+    case 1: return ((ClassDefFormat1*)this)->sanitize (vertex);
+    case 2: return ((ClassDefFormat2*)this)->sanitize (vertex);
+#ifndef HB_NO_BORING_EXPANSION
+    // Not currently supported
+    case 3:
+    case 4:
+#endif
+    default: return false;
+    }
+  }
+};
+
+
+}
+
+#endif  // GRAPH_CLASSDEF_GRAPH_HH
diff --git a/src/graph/coverage-graph.hh b/src/graph/coverage-graph.hh
index c18b4f112..28ceed945 100644
--- a/src/graph/coverage-graph.hh
+++ b/src/graph/coverage-graph.hh
@@ -85,7 +85,7 @@ struct Coverage : public OT::Layout::Common::Coverage
     auto* coverage_link = c.graph.vertices_[new_parent_id].obj.real_links.push ();
     coverage_link->width = SmallTypes::size;
     coverage_link->objidx = coverage_prime_id;
-    coverage_link->position = 2;
+    coverage_link->position = link_position;
     coverage_prime_vertex.parents.push (new_parent_id);
 
     return true;
diff --git a/src/graph/pairpos-graph.hh b/src/graph/pairpos-graph.hh
index dce38cd6b..d52d3bb09 100644
--- a/src/graph/pairpos-graph.hh
+++ b/src/graph/pairpos-graph.hh
@@ -28,6 +28,7 @@
 #define GRAPH_PAIRPOS_GRAPH_HH
 
 #include "coverage-graph.hh"
+#include "classdef-graph.hh"
 #include "../OT/Layout/GPOS/PairPos.hh"
 #include "../OT/Layout/GPOS/PosLookupSubTable.hh"
 
@@ -308,10 +309,19 @@ struct PairPosFormat2 : public OT::Layout::GPOS_impl::PairPosFormat2_4<SmallType
     pair_pos_prime->class2Count = this->class2Count;
     clone_class1_records (split_context, pair_pos_prime, start, end);
 
+    unsigned coverage_id =
+        split_context.c.graph.index_for_offset (split_context.this_index, &coverage);
+    if (!Coverage::clone_coverage (split_context.c,
+                                   coverage_id,
+                                   pair_pos_prime_id,
+                                   2,
+                                   start, end))
+      return -1;
 
+    // TODO: class def 1 (clone_classdef (start, end))
+    // TODO: class def 2 (just link to existing)
 
-    // TODO
-    return -1;
+    return -1; // TODO
   }
 
   void clone_class1_records (split_context& split_context,
diff --git a/src/meson.build b/src/meson.build
index 1f1105cae..2118eb57c 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -350,6 +350,7 @@ hb_subset_sources = files(
   'graph/gsubgpos-graph.hh',
   'graph/pairpos-graph.hh',
   'graph/coverage-graph.hh',
+  'graph/classdef-graph.hh',
   'hb-subset.cc',
   'hb-subset.hh',
 )