diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 90fe1a2..cd11833 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,12 +19,14 @@ jobs:
     strategy:
       fail-fast: false
       # Mirrors CppInterOp's cppyy PR cells: clang-repl on the same OS/arch/LLVM
-      # /valgrind combos at Python 3.14, plus a cling cell. Breadth (3.12/3.13,
-      # C++17, LLVM 20, arm) lives in nightly.
+      # /valgrind combos at Python 3.14, plus a cling cell and a C++23 cell
+      # (test_cpp23features runs only there). Breadth (3.12/3.13, C++17, LLVM
+      # 20, arm) lives in nightly.
       matrix:
         include:
           - { os: ubuntu-24.04,   llvm: '21', flavor: system, py: '3.14', cxx: '20', vg: true }
           - { os: ubuntu-24.04,   llvm: '22', flavor: '',     py: '3.14', cxx: '20' }
+          - { os: ubuntu-24.04,   llvm: '22', flavor: '',     py: '3.14', cxx: '23' }
           - { os: macos-26,       llvm: '21', flavor: system, py: '3.14', cxx: '20' }
           - { os: macos-26-intel, llvm: '21', flavor: system, py: '3.14', cxx: '20' }
           # cling backend, against the cached llvm-root (cling-llvm22) recipe cell.
diff --git a/.github/workflows/nightly.yml b/.github/workflows/nightly.yml
index 88d40d6..a452156 100644
--- a/.github/workflows/nightly.yml
+++ b/.github/workflows/nightly.yml
@@ -25,12 +25,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # Superset of the PR matrix + breadth (py 3.12/3.13, C++17, LLVM 20, arm)
-        # and one cling cell. valgrind only where a supp is vendored: the LLVM 21
-        # cells (clang21) and the arm LLVM 22 cell (clang22), both under
+        # Superset of the PR matrix + breadth (py 3.12/3.13, C++17/23, LLVM 20,
+        # arm) and one cling cell. valgrind only where a supp is vendored: the
+        # LLVM 21 cells (clang21) and the arm LLVM 22 cell (clang22), both under
         # .github/valgrind/.
         include:
           - { os: ubuntu-24.04,     llvm: '20', flavor: system, py: '3.12', cxx: '17' }
+          - { os: ubuntu-24.04,     llvm: '22', flavor: '',     py: '3.14', cxx: '23' }
           - { os: ubuntu-24.04,     llvm: '21', flavor: system, py: '3.13', cxx: '20', vg: true }
           - { os: ubuntu-24.04,     llvm: '21', flavor: system, py: '3.14', cxx: '20', vg: true }
           - { os: ubuntu-24.04,     llvm: '22', flavor: '',     py: '3.14', cxx: '20' }
@@ -38,6 +39,7 @@ jobs:
           - { os: ubuntu-24.04-arm, llvm: '22', flavor: '',     py: '3.13', cxx: '20', vg: true }
           - { os: ubuntu-24.04-arm, llvm: '20', flavor: system, py: '3.12', cxx: '17' }
           - { os: macos-26,         llvm: '21', flavor: system, py: '3.12', cxx: '20' }
+          - { os: macos-26,         llvm: '21', flavor: system, py: '3.14', cxx: '23' }
           - { os: macos-26-intel,   llvm: '21', flavor: system, py: '3.12', cxx: '20' }
           # cling backend, against the cached llvm-root (cling-llvm22) recipe cell.
           - { os: ubuntu-24.04,     llvm: '22', flavor: cling,  flavor_version: cling-llvm22, py: '3.13', cxx: '20' }
diff --git a/test/support.py b/test/support.py
index 34b9f9a..5d1e74e 100644
--- a/test/support.py
+++ b/test/support.py
@@ -94,4 +94,12 @@ def setup_make(targetname):
     == 1
 )
 IS_CLING = not IS_CLANG_REPL
+IS_CPP23 = (
+    cppjit.evaluate("""#if __cplusplus >= 202302L
+                                            true
+                                            #else
+                                            false
+                                            #endif\n""")
+    == 1
+)
 IS_VALGRIND = True if os.getenv("IS_VALGRIND") else False
diff --git a/test/test_cpp23features.py b/test/test_cpp23features.py
index 0d2925a..16b5423 100644
--- a/test/test_cpp23features.py
+++ b/test/test_cpp23features.py
@@ -1,39 +1,23 @@
-import os
-import subprocess
-import sys
-
 from pytest import mark
+from support import IS_CPP23
 
-# C++23 isn't the stack's default and the interpreter is a process-wide
-# singleton pinned at the first `import cppjit`. So TestCPP23Driver re-runs the
-# whole class once in a child process that selects C++23 before import
-# (EXTRA_CLING_ARGS for cling, CPPINTEROP_EXTRA_INTERPRETER_ARGS for clang-repl);
-# all tests then share that one interpreter. To iterate locally, run the tests
-# directly in "child mode":
+# The interpreter is a process-wide singleton whose C++ standard is pinned at
+# the first `import cppjit`, so these tests only run when the suite itself is
+# under C++23 (the cxx-standard=23 CI cells). To run them locally (the env var
+# reaches CreateInterpreter for both clang-repl and cling):
 #
-#     CPPJIT_TEST_CPP23_CHILD=1 EXTRA_CLING_ARGS=-std=c++23 \
-#     CPPINTEROP_EXTRA_INTERPRETER_ARGS=-std=c++23 \
-#     pytest -v test_cpp23features.py
-
-_CPP23_CHILD = "CPPJIT_TEST_CPP23_CHILD"
-_IN_CHILD = bool(os.environ.get(_CPP23_CHILD))
+#     CPPINTEROP_EXTRA_INTERPRETER_ARGS=-std=c++23 pytest -v test_cpp23features.py
 
 
 @mark.skipif(
-    not _IN_CHILD,
-    reason="C++23 tests run in the child interpreter launched by TestCPP23Driver",
+    not IS_CPP23,
+    reason="C++23 tests need the interpreter to run under -std=c++23",
 )
 class TestCPP23FEATURES:
-    """C++23 features driven via cppjit.cppdef through the JIT (clang-repl/cling).
-
-    The class owns one C++23 interpreter (booted in setup_class); tests share
-    it via ``self.cppjit``.
-    """
+    """C++23 features driven via cppjit.cppdef through the JIT (clang-repl/cling)."""
 
     @classmethod
     def setup_class(cls):
-        # In the child process C++23 is already selected, so this one-time boot
-        # is the C++23 interpreter every test shares.
         import cppjit
 
         cls.cppjit = cppjit
@@ -442,33 +426,3 @@ def test21_blog_sfinae_friendly_transform(self):
         """)
 
         assert cppjit.gbl.Cpp23DeducingThis.drive_transform() == 42
-
-
-@mark.skipif(_IN_CHILD, reason="launcher runs only in the parent process")
-class TestCPP23Driver:
-    """Re-run TestCPP23FEATURES once in a child interpreter pinned to C++23."""
-
-    def test_run_under_cpp23(self):
-        env = dict(os.environ)
-        env[_CPP23_CHILD] = "1"
-        env["EXTRA_CLING_ARGS"] = "-std=c++23"  # cling
-        env["CPPINTEROP_EXTRA_INTERPRETER_ARGS"] = "-std=c++23"  # clang-repl
-        proc = subprocess.run(
-            [
-                sys.executable,
-                "-m",
-                "pytest",
-                "-q",
-                "-p",
-                "no:cacheprovider",
-                os.path.basename(__file__),
-            ],
-            cwd=os.path.dirname(os.path.abspath(__file__)),
-            env=env,
-            capture_output=True,
-            text=True,
-        )
-        assert proc.returncode == 0, (
-            "C++23 child run failed (rc=%d)\n--- stdout ---\n%s\n--- stderr ---\n%s"
-            % (proc.returncode, proc.stdout, proc.stderr)
-        )
diff --git a/test/test_datatypes.py b/test/test_datatypes.py
index eed3b3a..89df961 100644
--- a/test/test_datatypes.py
+++ b/test/test_datatypes.py
@@ -2,7 +2,7 @@
 
 import py
 from pytest import mark, raises, skip
-from support import IS_CLANG_REPL, IS_MAC, pylong, pyunicode, setup_make
+from support import IS_CLANG_REPL, IS_CPP23, IS_MAC, pylong, pyunicode, setup_make
 
 currpath = py.path.local(__file__).dirpath()
 test_dct = str(currpath.join("cpp/datatypesDict"))
@@ -20,6 +20,12 @@ def setup_class(cls):
         cls.datatypes = cppjit.load_reflection_info(cls.test_dct)
         cls.N = 5  # cppjit.gbl.N
 
+    @mark.xfail(
+        condition=IS_CPP23,
+        reason="since C++23 (P1467) the narrowing std::complex<double> to "
+        "complex<float> constructor is explicit, breaking the implicit "
+        "conversion of Python complex arguments",
+    )
     def test01_instance_data_read_access(self):
         """Read access to instance public data and verify values"""