diff --git a/Lib/profiling/sampling/stack_collector.py b/Lib/profiling/sampling/stack_collector.py
index 8de460856666d7f..60ff5d7776b061d 100644
--- a/Lib/profiling/sampling/stack_collector.py
+++ b/Lib/profiling/sampling/stack_collector.py
@@ -60,7 +60,8 @@ def export(self, filename):
 
         lines.sort(key=lambda x: (-x[1], x[0]))
 
-        with open(filename, "w") as f:
+        with open(filename, "w",
+                  encoding="utf-8", errors="surrogatepass") as f:
             for stack, count in lines:
                 f.write(f"{stack} {count}\n")
         print(f"Collapsed stack output written to {filename}")
diff --git a/Lib/test/libregrtest/utils.py b/Lib/test/libregrtest/utils.py
index dfec7a59b02583b..6de2d07bcbb3b38 100644
--- a/Lib/test/libregrtest/utils.py
+++ b/Lib/test/libregrtest/utils.py
@@ -330,9 +330,6 @@ def get_build_info():
     # Get most important configure and build options as a list of strings.
     # Example: ['debug', 'ASAN+MSAN'] or ['release', 'LTO+PGO'].
 
-    config_args = sysconfig.get_config_var('CONFIG_ARGS') or ''
-    cflags = sysconfig.get_config_var('PY_CFLAGS') or ''
-    cflags += ' ' + (sysconfig.get_config_var('PY_CFLAGS_NODIST') or '')
     ldflags_nodist = sysconfig.get_config_var('PY_LDFLAGS_NODIST') or ''
 
     build = []
@@ -351,18 +348,16 @@ def get_build_info():
             free_threading = f"{free_threading} GIL={int(PYTHON_GIL)}"
         build.append(free_threading)
 
-    if hasattr(sys, 'gettotalrefcount'):
+    if support.Py_DEBUG:
         # --with-pydebug
         build.append('debug')
 
-        if '-DNDEBUG' in cflags:
+        if not support.built_with_c_assertions():
             build.append('without_assert')
     else:
         build.append('release')
 
-        if '--with-assertions' in config_args:
-            build.append('with_assert')
-        elif '-DNDEBUG' not in cflags:
+        if support.built_with_c_assertions():
             build.append('with_assert')
 
     # --enable-experimental-jit
diff --git a/Lib/test/pythoninfo.py b/Lib/test/pythoninfo.py
index ea7edb798051567..90b32aaaaf9a40a 100644
--- a/Lib/test/pythoninfo.py
+++ b/Lib/test/pythoninfo.py
@@ -611,14 +611,6 @@ def collect_sysconfig(info_add):
         value = normalize_text(value)
         info_add('sysconfig[%s]' % name, value)
 
-    PY_CFLAGS = sysconfig.get_config_var('PY_CFLAGS')
-    NDEBUG = (PY_CFLAGS and '-DNDEBUG' in PY_CFLAGS)
-    if NDEBUG:
-        text = 'ignore assertions (macro defined)'
-    else:
-        text= 'build assertions (macro not defined)'
-    info_add('build.NDEBUG',text)
-
     for name in (
         'WITH_DOC_STRINGS',
         'WITH_DTRACE',
@@ -844,6 +836,8 @@ def collect_support(info_add):
              support.check_sanitizer(memory=True))
     info_add('support.check_sanitizer(ub=True)',
              support.check_sanitizer(ub=True))
+    info_add('support.built_with_c_assertions',
+             support.built_with_c_assertions())
 
 
 def collect_support_os_helper(info_add):
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index 1c28af08988d9f0..28a0ba6c666629b 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -74,7 +74,7 @@
     "run_no_yield_async_fn", "run_yielding_async_fn", "async_yield",
     "reset_code", "on_github_actions",
     "requires_root_user", "requires_non_root_user",
-    "skip_if_double_rounding",
+    "skip_if_double_rounding", "built_with_c_assertions",
     ]
 
 
@@ -3526,3 +3526,18 @@ def check_immutable_type(testcase, type):
     else:
         flags = type_getflags(type)
         testcase.assertTrue(flags & Py_TPFLAGS_IMMUTABLETYPE)
+
+
+def built_with_c_assertions():
+    """Check if Python was built with C assertions (assert())."""
+
+    if MS_WINDOWS:
+        # On Windows, rely on the Py_DEBUG macro to check for assertions
+        return Py_DEBUG
+
+    # Check if the NDEBUG macro is defined in C compiler flags
+    PY_CFLAGS = (sysconfig.get_config_var('PY_CFLAGS') or '')
+    if '-DNDEBUG' in PY_CFLAGS:
+        return False
+
+    return True
diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
index 4c721c01a34f070..10f2a5dfb505e31 100644
--- a/Lib/test/test_gc.py
+++ b/Lib/test/test_gc.py
@@ -12,7 +12,6 @@
 
 import gc
 import sys
-import sysconfig
 import textwrap
 import threading
 import time
@@ -79,13 +78,6 @@ def __init__(self, partner=None):
     def __tp_del__(self):
         pass
 
-if sysconfig.get_config_vars().get('PY_CFLAGS', ''):
-    BUILD_WITH_NDEBUG = ('-DNDEBUG' in sysconfig.get_config_vars()['PY_CFLAGS'])
-else:
-    # Usually, sys.gettotalrefcount() is only present if Python has been
-    # compiled in debug mode. If it's missing, expect that Python has
-    # been released in release mode: with NDEBUG defined.
-    BUILD_WITH_NDEBUG = (not hasattr(sys, 'gettotalrefcount'))
 
 ### Tests
 ###############################################################################
@@ -1422,8 +1414,8 @@ def test_collect_garbage(self):
 
 
     @requires_subprocess()
-    @unittest.skipIf(BUILD_WITH_NDEBUG,
-                     'built with -NDEBUG')
+    @unittest.skipIf(not support.built_with_c_assertions(),
+                     'built without C assertions')
     def test_refcount_errors(self):
         self.preclean()
         # Verify the "handling" of objects with broken refcounts
diff --git a/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py b/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
index 069a72eb1c88a6a..dcfca9a9bceb503 100644
--- a/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
+++ b/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
@@ -466,6 +466,28 @@ def test_collapsed_stack_collector_export(self):
         self.assertIn(stack1_expected, lines)
         self.assertIn(stack2_expected, lines)
 
+    def test_collapsed_stack_collector_export_non_ascii_names(self):
+        # gh-156810: frame names are written verbatim, so the output must be
+        # opened with an encoding that can represent non-ASCII and
+        # surrogate-escaped (undecodable-path) names.
+        collapsed_out = tempfile.NamedTemporaryFile(delete=False)
+        self.addCleanup(close_and_unlink, collapsed_out)
+
+        collector = CollapsedStackCollector(1000)
+        frame = MockFrameInfo("/tmp/ba\udc80d.py", 5, "计算")
+        collector.collect([
+            MockInterpreterInfo(0, [MockThreadInfo(1, [frame])])
+        ])
+
+        with captured_stdout(), captured_stderr():
+            collector.export(collapsed_out.name)
+
+        with open(collapsed_out.name, encoding="utf-8",
+                  errors="surrogatepass") as f:
+            content = f.read()
+        self.assertIn("计算", content)
+        self.assertIn("ba\udc80d.py", content)
+
     def test_flamegraph_collector_basic(self):
         """Test basic FlamegraphCollector functionality."""
         collector = FlamegraphCollector(1000)
diff --git a/Misc/NEWS.d/next/Library/2026-09-02-17-28-16.gh-issue-156810.cLpEnc.rst b/Misc/NEWS.d/next/Library/2026-09-02-17-28-16.gh-issue-156810.cLpEnc.rst
new file mode 100644
index 000000000000000..610b0b4fcdc1baa
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-09-02-17-28-16.gh-issue-156810.cLpEnc.rst
@@ -0,0 +1,4 @@
+Fix a :exc:`UnicodeEncodeError` crash in the sampling profiler's
+collapsed-stack export (``--collapsed``) when a sampled frame's function or
+file name contains non-ASCII or surrogate-escaped characters. The output file
+is now written as UTF-8.
diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
index 5630f0309d98cff..a744a885932cdf5 100644
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -1671,17 +1671,17 @@ _textiowrapper_writeflush(textio *self)
     }
     else {
         assert(PyList_Check(pending));
-        b = PyBytes_FromStringAndSize(NULL, self->pending_bytes_count);
-        if (b == NULL) {
+        PyBytesWriter *writer = PyBytesWriter_Create(self->pending_bytes_count);
+        if (writer == NULL) {
             return -1;
         }
 
-        char *buf = PyBytes_AsString(b);
+        char *buf = PyBytesWriter_GetData(writer);
         Py_ssize_t pos = 0;
 
         for (Py_ssize_t i = 0; i < PyList_GET_SIZE(pending); i++) {
             PyObject *obj = PyList_GET_ITEM(pending, i);
-            char *src;
+            const char *src;
             Py_ssize_t len;
             if (PyUnicode_Check(obj)) {
                 assert(PyUnicode_IS_ASCII(obj));
@@ -1690,15 +1690,18 @@ _textiowrapper_writeflush(textio *self)
             }
             else {
                 assert(PyBytes_Check(obj));
-                if (PyBytes_AsStringAndSize(obj, &src, &len) < 0) {
-                    Py_DECREF(b);
-                    return -1;
-                }
+                src = PyBytes_AS_STRING(obj);
+                len = PyBytes_GET_SIZE(obj);
             }
             memcpy(buf + pos, src, len);
             pos += len;
         }
         assert(pos == self->pending_bytes_count);
+
+        b = PyBytesWriter_Finish(writer);
+        if (b == NULL) {
+            return -1;
+        }
     }
 
     self->pending_bytes_count = 0;