diff --git a/autotests/folding/highlight.cpp.fold b/autotests/folding/highlight.cpp.fold
--- a/autotests/folding/highlight.cpp.fold
+++ b/autotests/folding/highlight.cpp.fold
@@ -428,21 +428,19 @@

 // Attributes

-int f(int i) [[expects: i > 0]] [[ensures audit x: x < 1]];
-
 [[noreturn]] void foo();
 [[deprecated]] void foo();
 [[deprecated("because")]] void foo();
 void foo([[carries_dependency]] int);

 [[opt(1), debug]]
 [[using CC: opt(1), debug]] // c++17
 [[using CC: CC::opt(1)]] // c++17

 [[gnu::assume_aligned(3'2l,2)]] void* f();
 [[using gnu: assume_aligned(3)]]
 [[clang::assume_aligned(3)]]

 void f([[maybe_unused]] int val)
 <beginfold id='1'>{</beginfold id='1'>
     [[maybe_unused]] int x;
diff --git a/autotests/html/highlight.cpp.html b/autotests/html/highlight.cpp.html
--- a/autotests/html/highlight.cpp.html
+++ b/autotests/html/highlight.cpp.html
@@ -434,21 +434,19 @@

 <span style="color:#898887;">// Attributes</span>

-<span style="color:#0057ae;">int</span> f(<span style="color:#0057ae;">int</span> i) [[<span style="color:#0057ae;font-style:italic;">expects</span>:<span style="color:#0057ae;font-style:italic;"> i </span>&gt;<span style="color:#0057ae;font-style:italic;"> </span><span style="color:#b08000;">0</span>]] [[<span style="color:#0057ae;font-style:italic;">ensures</span><span style="color:#0057ae;font-style:italic;"> </span><span style="color:#0057ae;font-style:italic;">audit</span><span style="color:#0057ae;font-style:italic;"> x</span>:<span style="color:#0057ae;font-style:italic;"> x </span>&lt;<span style="color:#0057ae;font-style:italic;"> </span><span style="color:#b08000;">1</span>]];
-
 [[<span style="color:#0057ae;font-style:italic;">noreturn</span>]] <span style="color:#0057ae;">void</span> foo();
 [[<span style="color:#0057ae;font-style:italic;">deprecated</span>]] <span style="color:#0057ae;">void</span> foo();
 [[<span style="color:#0057ae;font-style:italic;">deprecated</span>(<span style="color:#bf0303;">&quot;because&quot;</span>)]] <span style="color:#0057ae;">void</span> foo();
 <span style="color:#0057ae;">void</span> foo([[<span style="color:#0057ae;font-style:italic;">carries_dependency</span>]] <span style="color:#0057ae;">int</span>);

 [[<span style="color:#0057ae;font-style:italic;">opt</span>(<span style="color:#b08000;">1</span>),<span style="color:#0057ae;font-style:italic;"> debug</span>]]
 [[<span style="font-weight:bold;">using</span><span style="color:#0057ae;font-style:italic;"> CC</span>:<span style="color:#0057ae;font-style:italic;"> opt</span>(<span style="color:#b08000;">1</span>),<span style="color:#0057ae;font-style:italic;"> debug</span>]] <span style="color:#898887;">// c++17</span>
 [[<span style="font-weight:bold;">using</span><span style="color:#0057ae;font-style:italic;"> CC</span>:<span style="color:#0057ae;font-style:italic;"> CC</span>::<span style="color:#0057ae;font-style:italic;">opt</span>(<span style="color:#b08000;">1</span>)]] <span style="color:#898887;">// c++17</span>

 [[<span style="color:#0095ff;font-weight:bold;font-style:italic;">gnu::assume_aligned</span>(<span style="color:#b08000;">3'2</span><span style="color:#644a9b;font-weight:bold;">l</span>,<span style="color:#b08000;">2</span>)]] <span style="color:#0057ae;">void</span>* f();
 [[<span style="font-weight:bold;">using</span><span style="color:#0057ae;font-style:italic;"> </span><span style="color:#0095ff;font-weight:bold;font-style:italic;">gnu</span>:<span style="color:#0057ae;font-style:italic;"> assume_aligned</span>(<span style="color:#b08000;">3</span>)]]
 [[<span style="color:#0095ff;font-weight:bold;font-style:italic;">clang::assume_aligned</span>(<span style="color:#b08000;">3</span>)]]

 <span style="color:#0057ae;">void</span> f([[<span style="color:#0057ae;font-style:italic;">maybe_unused</span>]] <span style="color:#0057ae;">int</span> val)
 {
     [[<span style="color:#0057ae;font-style:italic;">maybe_unused</span>]] <span style="color:#0057ae;">int</span> x;
diff --git a/autotests/input/highlight.cpp b/autotests/input/highlight.cpp
--- a/autotests/input/highlight.cpp
+++ b/autotests/input/highlight.cpp
@@ -428,21 +428,19 @@

 // Attributes

-int f(int i) [[expects: i > 0]] [[ensures audit x: x < 1]];
-
 [[noreturn]] void foo();
 [[deprecated]] void foo();
 [[deprecated("because")]] void foo();
 void foo([[carries_dependency]] int);

 [[opt(1), debug]]
 [[using CC: opt(1), debug]] // c++17
 [[using CC: CC::opt(1)]] // c++17

 [[gnu::assume_aligned(3'2l,2)]] void* f();
 [[using gnu: assume_aligned(3)]]
 [[clang::assume_aligned(3)]]

 void f([[maybe_unused]] int val)
 {
     [[maybe_unused]] int x;
diff --git a/autotests/reference/highlight.cpp.ref b/autotests/reference/highlight.cpp.ref
--- a/autotests/reference/highlight.cpp.ref
+++ b/autotests/reference/highlight.cpp.ref
@@ -428,8 +428,6 @@
 <Normal Text></Normal Text><br/>
 <Comment>// Attributes</Comment><br/>
 <Normal Text></Normal Text><br/>
-<Data Type>int</Data Type><Normal Text> f</Normal Text><Symbol>(</Symbol><Data Type>int</Data Type><Normal Text> i</Normal Text><Symbol>)</Symbol><Normal Text> </Normal Text><Symbol>[[</Symbol><Standard Attribute>expects</Standard Attribute><Symbol>:</Symbol><Attribute> i </Attribute><Symbol>></Symbol><Attribute> </Attribute><Decimal>0</Decimal><Symbol>]]</Symbol><Normal Text> </Normal Text><Symbol>[[</Symbol><Standard Attribute>ensures</Standard Attribute><Attribute> </Attribute><Standard Attribute>audit</Standard Attribute><Attribute> x</Attribute><Symbol>:</Symbol><Attribute> x </Attribute><Symbol><</Symbol><Attribute> </Attribute><Decimal>1</Decimal><Symbol>]]</Symbol><Separator Symbol>;</Separator Symbol><br/>
-<Normal Text></Normal Text><br/>
 <Symbol>[[</Symbol><Standard Attribute>noreturn</Standard Attribute><Symbol>]]</Symbol><Normal Text> </Normal Text><Data Type>void</Data Type><Normal Text> foo</Normal Text><Symbol>()</Symbol><Separator Symbol>;</Separator Symbol><br/>
 <Symbol>[[</Symbol><Standard Attribute>deprecated</Standard Attribute><Symbol>]]</Symbol><Normal Text> </Normal Text><Data Type>void</Data Type><Normal Text> foo</Normal Text><Symbol>()</Symbol><Separator Symbol>;</Separator Symbol><br/>
 <Symbol>[[</Symbol><Standard Attribute>deprecated</Standard Attribute><Symbol>(</Symbol><String>"because"</String><Symbol>)]]</Symbol><Normal Text> </Normal Text><Data Type>void</Data Type><Normal Text> foo</Normal Text><Symbol>()</Symbol><Separator Symbol>;</Separator Symbol><br/>
diff --git a/data/syntax/isocpp.xml b/data/syntax/isocpp.xml
--- a/data/syntax/isocpp.xml
+++ b/data/syntax/isocpp.xml
@@ -22,7 +22,7 @@
 <language
     name="ISO C++"
     section="Sources"
-    version="15"
+    version="16"
     kateversion="5.0"
     indenter="cstyle"
     style="C++"
@@ -110,7 +110,7 @@
       <item>or_eq</item>
       <item>xor</item>
       <item>xor_eq</item>
-      <!-- Contract -->
+      <!-- Concept -->
       <item>concept</item>
       <item>requires</item>
       <!-- TM TS -->
@@ -158,26 +158,14 @@
       <!-- TM TS -->
       <!-- <item>optimize_for_synchronized</item> -->
     </list>
-    <list name="contractAttributes">
-      <!-- C++20 -->
-      <item>assert</item>
-      <item>ensures</item>
-      <item>expects</item>
-    </list>
-    <list name="contractLevel">
-      <!-- C++20 -->
-      <item>default</item>
-      <item>audit</item>
-      <item>axiom</item>
-    </list>
     <!-- This keyword may appear in Attribute context. For example in code:
     [[using CC: opt(1), debug]]
     and it should be displayed as keyword, not like part of attribute...
     -->
     <list name="using">
       <item>using</item>
     </list>

     <!-- https://en.cppreference.com/w/cpp/keyword -->
     <list name="types">
       <item>bool</item>
@@ -530,7 +518,6 @@
       <context name="Attribute" attribute="Attribute" lineEndContext="#stay">
         <DetectSpaces/>
         <keyword attribute="Standard Attribute" context="#stay" String="attributes" />
-        <keyword attribute="Standard Attribute" context="Contract Attribute" String="contractAttributes" />
         <Detect2Chars attribute="Symbol" context="#pop" char="]" char1="]" />
         <DetectChar attribute="Separator Symbol" context="#stay" char="," />
         <AnyChar attribute="Symbol" context="#stay" String="&punctuators;" />
@@ -543,90 +530,85 @@
         <DetectIdentifier />
       </context>

-      <context name="Contract Attribute" attribute="Attribute" lineEndContext="#pop" fallthrough="true" fallthroughContext="#pop">
-        <DetectSpaces/>
-        <keyword attribute="Standard Attribute" context="#pop" String="contractLevel" />
-      </context>
-
       <context name="Attribute In PP" attribute="Attribute" lineEndContext="#pop">
         <IncludeRules context="InPreprocessor" />
         <IncludeRules context="Attribute" />
       </context>

       <context name="AttributeNamespace" attribute="Attribute" lineEndContext="#stay" fallthrough="true" fallthroughContext="#pop">
         <DetectSpaces />
         <IncludeRules context="DetectNamespaceGccAttributes##GCCExtensions" />
         <DetectIdentifier />
       </context>

       <context name="RawString" attribute="String" lineEndContext="#stay" fallthrough="true" fallthroughContext="#pop!LineError">
         <RegExpr attribute="String" context="#pop!InRawString" String="([^\(]{0,16})\(" />
       </context>

       <context name="InRawString" attribute="String" lineEndContext="#stay" dynamic="true">
         <!-- fast way, can be replaced by a `UntilChars` rule if it exists -->
         <RegExpr attribute="String" context="#stay" String="[^%)]+" />
         <RegExpr attribute="String Char" context="#stay" String="&printf_like;" />
         <StringDetect attribute="String" context="#pop" String=")%1&quot;" dynamic="true"/>
       </context>

       <context name="Region Marker" attribute="Region Marker" lineEndContext="#pop" />

       <context name="DetectNSEnd" attribute="Normal Text" lineEndContext="#stay">
         <keyword attribute="Keyword" context="#stay" String="template" />
         <DetectIdentifier context="#stay" />
         <AnyChar attribute="Separator Symbol" context="#pop" String="&separators;" />
         <AnyChar attribute="Symbol" context="#pop" String="&ns_punctuators; &#9;" />
       </context>

       <context name="Standard Classes" attribute="Standard Classes" lineEndContext="#stay">
         <IncludeRules context="DetectNSEnd" />
       </context>

       <context name="Boost Stuff" attribute="Boost Stuff" lineEndContext="#stay">
         <IncludeRules context="DetectNSEnd" />
       </context>

       <context name="InternalsNS" attribute="Internals" lineEndContext="#stay">
         <IncludeRules context="DetectNSEnd" />
       </context>

       <context name="Standard Classes In PP" attribute="Standard Classes" lineEndContext="#pop">
         <IncludeRules context="InPreprocessor" />
         <IncludeRules context="DetectNSEnd" />
       </context>

       <context name="Boost Stuff In PP" attribute="Boost Stuff" lineEndContext="#pop">
         <IncludeRules context="InPreprocessor" />
         <IncludeRules context="DetectNSEnd" />
       </context>

       <context name="InternalsNS In PP" attribute="Internals" lineEndContext="#pop">
         <IncludeRules context="InPreprocessor" />
         <IncludeRules context="DetectNSEnd" />
       </context>

       <context name="Comment 1" attribute="Comment" lineEndContext="#pop">
         <LineContinue attribute="Error" context="#stay" />
         <DetectSpaces />
         <IncludeRules context="##Alerts" />
         <IncludeRules context="##Modelines" />
         <DetectIdentifier />
       </context>

       <context name="Comment 2" attribute="Comment" lineEndContext="#stay">
         <DetectSpaces />
         <LineContinue attribute="Comment" context="#stay" />
         <Detect2Chars attribute="Comment" context="#pop" char="*" char1="/" endRegion="Comment" />
         <IncludeRules context="##Alerts" />
         <IncludeRules context="##Modelines" />
         <DetectIdentifier />
       </context>

       <context name="AfterHash" attribute="Error" lineEndContext="#pop" fallthrough="true" fallthroughContext="#pop!AfterHashLineError">
         <RegExpr attribute="Preprocessor" context="#pop!PreprocessorCmd" String="&pphash;(?=.)" firstNonSpace="true" />
       </context>

       <context name="AfterHashLineError" attribute="Region Marker" lineEndContext="#pop">
         <LineContinue attribute="Error" context="#stay" />
         <RegExpr attribute="Error" context="#pop!LineError" String="[^\\]+" />