diff --git a/libcxx/cmake/caches/Generic-debug.cmake b/libcxx/cmake/caches/Generic-debug.cmake
new file mode 100644
--- /dev/null
+++ b/libcxx/cmake/caches/Generic-debug.cmake
@@ -0,0 +1,2 @@
+set(LIBCXX_TEST_PARAMS "std=c++2b" "debug_level=1" "additional_features=LIBCXX-DEBUG-FIXME" CACHE STRING "")
+set(LIBCXXABI_TEST_PARAMS "${LIBCXX_TEST_PARAMS}" CACHE STRING "")
diff --git a/libcxx/test/libcxx/containers/sequences/vector/robust_against_adl.pass.cpp b/libcxx/test/libcxx/containers/sequences/vector/robust_against_adl.pass.cpp
--- a/libcxx/test/libcxx/containers/sequences/vector/robust_against_adl.pass.cpp
+++ b/libcxx/test/libcxx/containers/sequences/vector/robust_against_adl.pass.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03
+// UNSUPPORTED: debug_level_0, debug_level_1
 
 // <vector>
 
diff --git a/libcxx/test/libcxx/diagnostics/nodiscard_extensions.pass.cpp b/libcxx/test/libcxx/diagnostics/nodiscard_extensions.pass.cpp
--- a/libcxx/test/libcxx/diagnostics/nodiscard_extensions.pass.cpp
+++ b/libcxx/test/libcxx/diagnostics/nodiscard_extensions.pass.cpp
@@ -18,6 +18,8 @@
 // UNSUPPORTED: apple-clang-9
 // UNSUPPORTED: gcc-5
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // All entities to which libc++ applies [[nodiscard]] as an extension should
 // be tested here and in nodiscard_extensions.fail.cpp. They should also
 // be listed in `UsingLibcxx.rst` in the documentation for the extension.
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.merge/inplace_merge_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.merge/inplace_merge_comp.pass.cpp
--- a/libcxx/test/std/algorithms/alg.sorting/alg.merge/inplace_merge_comp.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.merge/inplace_merge_comp.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // <algorithm>
 
 // template<BidirectionalIterator Iter, StrictWeakOrder<auto, Iter::value_type> Compare>
diff --git a/libcxx/test/std/containers/views/span.cons/deduct.pass.cpp b/libcxx/test/std/containers/views/span.cons/deduct.pass.cpp
--- a/libcxx/test/std/containers/views/span.cons/deduct.pass.cpp
+++ b/libcxx/test/std/containers/views/span.cons/deduct.pass.cpp
@@ -7,6 +7,7 @@
 //
 //===---------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: LIBCXX-DEBUG-FIXME
 
 // <span>
 
diff --git a/libcxx/test/std/containers/views/span.iterators/begin.pass.cpp b/libcxx/test/std/containers/views/span.iterators/begin.pass.cpp
--- a/libcxx/test/std/containers/views/span.iterators/begin.pass.cpp
+++ b/libcxx/test/std/containers/views/span.iterators/begin.pass.cpp
@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: LIBCXX-DEBUG-FIXME
 
 // <span>
 
diff --git a/libcxx/test/std/containers/views/span.iterators/end.pass.cpp b/libcxx/test/std/containers/views/span.iterators/end.pass.cpp
--- a/libcxx/test/std/containers/views/span.iterators/end.pass.cpp
+++ b/libcxx/test/std/containers/views/span.iterators/end.pass.cpp
@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: LIBCXX-DEBUG-FIXME
 
 // <span>
 
diff --git a/libcxx/test/std/containers/views/span.iterators/rbegin.pass.cpp b/libcxx/test/std/containers/views/span.iterators/rbegin.pass.cpp
--- a/libcxx/test/std/containers/views/span.iterators/rbegin.pass.cpp
+++ b/libcxx/test/std/containers/views/span.iterators/rbegin.pass.cpp
@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: LIBCXX-DEBUG-FIXME
 
 // <span>
 
diff --git a/libcxx/test/std/containers/views/span.iterators/rend.pass.cpp b/libcxx/test/std/containers/views/span.iterators/rend.pass.cpp
--- a/libcxx/test/std/containers/views/span.iterators/rend.pass.cpp
+++ b/libcxx/test/std/containers/views/span.iterators/rend.pass.cpp
@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: LIBCXX-DEBUG-FIXME
 
 // <span>
 
diff --git a/libcxx/test/std/containers/views/span.sub/first.pass.cpp b/libcxx/test/std/containers/views/span.sub/first.pass.cpp
--- a/libcxx/test/std/containers/views/span.sub/first.pass.cpp
+++ b/libcxx/test/std/containers/views/span.sub/first.pass.cpp
@@ -7,6 +7,7 @@
 //
 //===---------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: LIBCXX-DEBUG-FIXME
 
 // <span>
 
diff --git a/libcxx/test/std/containers/views/span.sub/last.pass.cpp b/libcxx/test/std/containers/views/span.sub/last.pass.cpp
--- a/libcxx/test/std/containers/views/span.sub/last.pass.cpp
+++ b/libcxx/test/std/containers/views/span.sub/last.pass.cpp
@@ -7,6 +7,7 @@
 //
 //===---------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: LIBCXX-DEBUG-FIXME
 
 // <span>
 
diff --git a/libcxx/test/std/containers/views/span.sub/subspan.pass.cpp b/libcxx/test/std/containers/views/span.sub/subspan.pass.cpp
--- a/libcxx/test/std/containers/views/span.sub/subspan.pass.cpp
+++ b/libcxx/test/std/containers/views/span.sub/subspan.pass.cpp
@@ -7,6 +7,7 @@
 //
 //===---------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: LIBCXX-DEBUG-FIXME
 
 // <span>
 
diff --git a/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/path.factory.pass.cpp b/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/path.factory.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/path.factory.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.path/path.nonmember/path.factory.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // UNSUPPORTED: c++03
 // ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DISABLE_DEPRECATION_WARNINGS
 
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.proximate/proximate.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.proximate/proximate.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.proximate/proximate.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.proximate/proximate.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // UNSUPPORTED: c++03
 
 // <filesystem>
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/robust_against_adl.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/robust_against_adl.pass.cpp
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/robust_against_adl.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/robust_against_adl.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // <iterator>
 
 #include <iterator>
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/iterator.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/iterator.pass.cpp
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/iterator.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/iterator.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // <string>
 
 // template<class InputIterator>
diff --git a/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/copy.pass.cpp b/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/copy.pass.cpp
--- a/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/copy.pass.cpp
+++ b/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/copy.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // UNSUPPORTED: clang-8
 
 // <string>
diff --git a/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/copy.pass.cpp b/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/copy.pass.cpp
--- a/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/copy.pass.cpp
+++ b/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/copy.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // <string>
 
 // template<> struct char_traits<char16_t>
diff --git a/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/copy.pass.cpp b/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/copy.pass.cpp
--- a/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/copy.pass.cpp
+++ b/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/copy.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // <string>
 
 // template<> struct char_traits<char32_t>
diff --git a/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/copy.pass.cpp b/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/copy.pass.cpp
--- a/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/copy.pass.cpp
+++ b/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/copy.pass.cpp
@@ -9,6 +9,8 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: clang-8
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // <string>
 
 // template<> struct char_traits<char8_t>
diff --git a/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/copy.pass.cpp b/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/copy.pass.cpp
--- a/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/copy.pass.cpp
+++ b/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/copy.pass.cpp
@@ -8,6 +8,8 @@
 
 // UNSUPPORTED: clang-8
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // <string>
 
 // template<> struct char_traits<wchar_t>
diff --git a/libcxx/test/std/strings/string.view/string.view.ops/copy.pass.cpp b/libcxx/test/std/strings/string.view/string.view.ops/copy.pass.cpp
--- a/libcxx/test/std/strings/string.view/string.view.ops/copy.pass.cpp
+++ b/libcxx/test/std/strings/string.view/string.view.ops/copy.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: LIBCXX-DEBUG-FIXME
+
 // XFAIL: gcc-10
 //     GCC's __builtin_strlen isn't constexpr yet
 
diff --git a/libcxx/utils/ci/buildkite-pipeline.yml b/libcxx/utils/ci/buildkite-pipeline.yml
--- a/libcxx/utils/ci/buildkite-pipeline.yml
+++ b/libcxx/utils/ci/buildkite-pipeline.yml
@@ -125,6 +125,18 @@
         - exit_status: -1  # Agent was lost
           limit: 2
 
+  - label: "Debug iterators"
+    command: "libcxx/utils/ci/run-buildbot generic-debug"
+    artifact_paths:
+      - "**/test-results.xml"
+      - "**/*.abilist"
+    agents:
+      queue: "libcxx-builders"
+    retry:
+      automatic:
+        - exit_status: -1  # Agent was lost
+          limit: 2
+
   - label: "MacOS C++20"
     command: "libcxx/utils/ci/run-buildbot generic-cxx20"
     artifact_paths:
diff --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -514,6 +514,14 @@
     echo "+++ Running the libc++ tests"
     ${NINJA} -vC "${BUILD_DIR}" check-cxx
 ;;
+generic-debug)
+    export CC=clang-tot
+    export CXX=clang++-tot
+    clean
+    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-debug.cmake"
+    check-cxx-cxxabi
+    check-abi-list
+;;
 *)
     echo "${BUILDER} is not a known configuration"
     exit 1
diff --git a/libcxx/utils/libcxx/test/config.py b/libcxx/utils/libcxx/test/config.py
--- a/libcxx/utils/libcxx/test/config.py
+++ b/libcxx/utils/libcxx/test/config.py
@@ -481,6 +481,7 @@
             self.lit_config.fatal('Invalid value for debug_level "%s".'
                                   % debug_level)
         self.cxx.compile_flags += ['-D_LIBCPP_DEBUG=%s' % debug_level]
+        self.config.available_features.add('debug_level_%s' % debug_level)
 
     def configure_sanitizer(self):
         san = self.get_lit_conf('use_sanitizer', '').strip()