diff --git a/Lib/test/test_pep669_monitoring_aug.py b/Lib/test/test_pep669_monitoring_aug.py
new file mode 100644
--- /dev/null
+++ b/Lib/test/test_pep669_monitoring_aug.py
@@ -0,0 +1,549 @@
+import sys
+import unittest
+from contextlib import suppress
+
+
+TOOL = 4
+TOOL2 = 3
+TOOL3 = 5
+E = sys.monitoring.events
+
+
+def _clear_tool(tool):
+    with suppress(Exception):
+        sys.monitoring.set_events(tool, 0)
+    for event in (
+        E.PY_START, E.PY_RESUME, E.PY_RETURN, E.PY_YIELD,
+        E.PY_UNWIND, E.PY_THROW, E.CALL, E.C_RAISE, E.C_RETURN,
+        E.RAISE, E.EXCEPTION_HANDLED, E.LINE, E.INSTRUCTION,
+        E.JUMP, E.BRANCH, E.STOP_ITERATION,
+    ):
+        with suppress(Exception):
+            sys.monitoring.register_callback(tool, event, None)
+    with suppress(Exception):
+        sys.monitoring.free_tool_id(tool)
+
+
+class MonitoringAugTest(unittest.TestCase):
+    def setUp(self):
+        _clear_tool(TOOL)
+        _clear_tool(TOOL2)
+        _clear_tool(TOOL3)
+
+    def tearDown(self):
+        _clear_tool(TOOL)
+        _clear_tool(TOOL2)
+        _clear_tool(TOOL3)
+
+    def claim(self, tool=TOOL, name="pep669-aug"):
+        sys.monitoring.use_tool_id(tool, name)
+        self.addCleanup(_clear_tool, tool)
+        return tool
+
+    def test_public_constants_are_power_of_two_and_tool_lifecycle(self):
+        events = [
+            "PY_START", "PY_RESUME", "PY_RETURN", "PY_YIELD",
+            "PY_UNWIND", "PY_THROW", "CALL", "C_RAISE", "C_RETURN",
+            "RAISE", "EXCEPTION_HANDLED", "LINE", "INSTRUCTION",
+            "JUMP", "BRANCH", "STOP_ITERATION",
+        ]
+        values = [getattr(E, name) for name in events]
+        self.assertEqual(len(values), len(set(values)))
+        for value in values:
+            self.assertGreater(value, 0)
+            self.assertEqual(value & (value - 1), 0)
+
+        self.assertEqual(sys.monitoring.DEBUGGER_ID, 0)
+        self.assertEqual(sys.monitoring.COVERAGE_ID, 1)
+        self.assertEqual(sys.monitoring.PROFILER_ID, 2)
+        self.assertEqual(sys.monitoring.OPTIMIZER_ID, 5)
+        self.assertIs(sys.monitoring.DISABLE, sys.monitoring.DISABLE)
+        self.assertIs(sys.monitoring.MISSING, sys.monitoring.MISSING)
+        # DISABLE and MISSING are distinct documented sentinels — neither may
+        # alias the other.
+        self.assertIsNot(sys.monitoring.DISABLE, sys.monitoring.MISSING)
+
+        self.assertIsNone(sys.monitoring.get_tool(TOOL))
+        sys.monitoring.use_tool_id(TOOL, "first")
+        self.assertEqual(sys.monitoring.get_tool(TOOL), "first")
+        with self.assertRaises(ValueError):
+            sys.monitoring.use_tool_id(TOOL, "second")
+        with self.assertRaises(ValueError):
+            sys.monitoring.use_tool_id(6, "outside-range")
+        with self.assertRaises((TypeError, ValueError)):
+            sys.monitoring.use_tool_id(TOOL2, object())
+        sys.monitoring.free_tool_id(TOOL)
+        self.assertIsNone(sys.monitoring.get_tool(TOOL))
+
+    def test_register_callback_replaces_previous_and_rejects_event_sets(self):
+        self.claim()
+
+        def callback_one(*args):
+            return None
+
+        def callback_two(*args):
+            return None
+
+        self.assertIsNone(
+            sys.monitoring.register_callback(TOOL, E.PY_START, callback_one)
+        )
+        self.assertIs(
+            sys.monitoring.register_callback(TOOL, E.PY_START, callback_two),
+            callback_one,
+        )
+        with self.assertRaises(ValueError):
+            sys.monitoring.register_callback(
+                TOOL, E.PY_START | E.PY_RETURN, callback_one
+            )
+        self.assertIs(
+            sys.monitoring.register_callback(TOOL, E.PY_START, None),
+            callback_two,
+        )
+
+    def test_set_events_requires_claimed_tool_and_call_group(self):
+        with self.assertRaises(ValueError):
+            sys.monitoring.set_events(TOOL, E.PY_START)
+
+        self.claim()
+        with self.assertRaises(ValueError):
+            sys.monitoring.set_events(TOOL, E.C_RETURN)
+        with self.assertRaises(ValueError):
+            sys.monitoring.set_events(TOOL, E.C_RAISE)
+
+        seen = []
+
+        def call_cb(code, offset, func, arg):
+            seen.append(("call", getattr(func, "__name__", type(func).__name__), arg))
+
+        def return_cb(code, offset, func, arg):
+            seen.append(("return", getattr(func, "__name__", type(func).__name__), arg))
+
+        def raise_cb(code, offset, func, arg):
+            seen.append(("raise", getattr(func, "__name__", type(func).__name__), arg))
+
+        sys.monitoring.register_callback(TOOL, E.CALL, call_cb)
+        sys.monitoring.register_callback(TOOL, E.C_RETURN, return_cb)
+        sys.monitoring.register_callback(TOOL, E.C_RAISE, raise_cb)
+        mask = E.CALL | E.C_RETURN | E.C_RAISE
+        sys.monitoring.set_events(TOOL, mask)
+        self.assertEqual(sys.monitoring.get_events(TOOL), E.CALL)
+
+        len([])
+        with suppress(ValueError):
+            int("not-an-int")
+        sys.monitoring.set_events(TOOL, 0)
+
+        names = [item[1] for item in seen]
+        self.assertIn("len", names)
+        self.assertIn("int", names)
+        self.assertTrue(any(kind == "return" and name == "len"
+                            for kind, name, arg in seen))
+        self.assertTrue(any(kind == "raise" and name == "int"
+                            for kind, name, arg in seen))
+
+    def test_local_line_events_are_scoped_to_one_code_object(self):
+        self.claim()
+        seen = []
+
+        def target():
+            value = 1
+            value += 2
+            return value
+
+        def other():
+            value = 5
+            return value
+
+        def line_cb(code, line):
+            seen.append((code.co_name, line - code.co_firstlineno))
+
+        sys.monitoring.register_callback(TOOL, E.LINE, line_cb)
+        self.assertEqual(sys.monitoring.get_events(TOOL), 0)
+        sys.monitoring.set_local_events(TOOL, target.__code__, E.LINE)
+        self.assertEqual(
+            sys.monitoring.get_local_events(TOOL, target.__code__), E.LINE
+        )
+
+        self.assertEqual(target(), 3)
+        self.assertEqual(other(), 5)
+        sys.monitoring.set_local_events(TOOL, target.__code__, 0)
+        before = list(seen)
+        target()
+        self.assertEqual(seen, before)
+        self.assertGreaterEqual(len([name for name, line in seen
+                                     if name == "target"]), 3)
+        self.assertFalse(any(name == "other" for name, line in seen))
+
+    def test_instruction_and_branch_events_report_offsets(self):
+        self.claim()
+        instructions = []
+        branches = []
+
+        def target(flag):
+            if flag:
+                return "yes"
+            return "no"
+
+        def instruction_cb(code, offset):
+            if code is target.__code__:
+                instructions.append(offset)
+
+        def branch_cb(code, offset, destination):
+            if code is target.__code__:
+                branches.append((offset, destination))
+
+        sys.monitoring.register_callback(TOOL, E.INSTRUCTION, instruction_cb)
+        sys.monitoring.register_callback(TOOL, E.BRANCH, branch_cb)
+        sys.monitoring.set_local_events(
+            TOOL, target.__code__, E.INSTRUCTION | E.BRANCH
+        )
+        self.assertEqual(target(True), "yes")
+        self.assertEqual(target(False), "no")
+        sys.monitoring.set_local_events(TOOL, target.__code__, 0)
+
+        self.assertGreater(len(instructions), 4)
+        self.assertGreaterEqual(len(branches), 2)
+        self.assertTrue(all(isinstance(offset, int) and isinstance(dest, int)
+                            for offset, dest in branches))
+
+    def test_exception_unwind_and_handled_events_are_distinct(self):
+        self.claim()
+        seen = []
+
+        def raise_cb(code, offset, exc):
+            seen.append(("raise", code.co_name, type(exc)))
+
+        def unwind_cb(code, offset):
+            seen.append(("unwind", code.co_name))
+
+        def handled_cb(code, offset, exc):
+            seen.append(("handled", code.co_name, type(exc)))
+
+        def leaf():
+            raise KeyError("pep669")
+
+        def target():
+            try:
+                leaf()
+            except KeyError:
+                return "handled"
+
+        sys.monitoring.register_callback(TOOL, E.RAISE, raise_cb)
+        sys.monitoring.register_callback(TOOL, E.PY_UNWIND, unwind_cb)
+        sys.monitoring.register_callback(TOOL, E.EXCEPTION_HANDLED, handled_cb)
+        sys.monitoring.set_events(
+            TOOL, E.RAISE | E.PY_UNWIND | E.EXCEPTION_HANDLED
+        )
+        self.assertEqual(target(), "handled")
+        sys.monitoring.set_events(TOOL, 0)
+
+        self.assertIn(("raise", "leaf", KeyError), seen)
+        self.assertIn(("unwind", "leaf"), seen)
+        self.assertTrue(any(item[0] == "handled" and item[2] is KeyError
+                            for item in seen if len(item) == 3))
+
+    def test_disable_return_value_and_restart_events(self):
+        self.claim()
+        seen = []
+
+        def target():
+            first = 1
+            second = 2
+            return first + second
+
+        def line_once(code, line):
+            if code is target.__code__:
+                seen.append(line)
+                return sys.monitoring.DISABLE
+
+        sys.monitoring.register_callback(TOOL, E.LINE, line_once)
+        sys.monitoring.set_local_events(TOOL, target.__code__, E.LINE)
+        target()
+        first_count = len(seen)
+        target()
+        self.assertEqual(len(seen), first_count)
+        sys.monitoring.restart_events()
+        target()
+        self.assertGreater(len(seen), first_count)
+        sys.monitoring.set_local_events(TOOL, target.__code__, 0)
+
+    def test_stop_iteration_event_is_separate_from_raise(self):
+        self.claim()
+        seen = []
+
+        def stop_cb(code, offset, exc):
+            seen.append(("stop", code.co_name, type(exc)))
+
+        def raise_cb(code, offset, exc):
+            seen.append(("raise", code.co_name, type(exc)))
+
+        def gen():
+            yield 1
+            return 2
+
+        def consume():
+            for _ in gen():
+                pass
+
+        sys.monitoring.register_callback(TOOL, E.STOP_ITERATION, stop_cb)
+        sys.monitoring.register_callback(TOOL, E.RAISE, raise_cb)
+        sys.monitoring.set_events(TOOL, E.STOP_ITERATION | E.RAISE)
+        consume()
+        sys.monitoring.set_events(TOOL, 0)
+
+        self.assertIn(("stop", "consume", StopIteration), seen)
+        self.assertNotIn(("raise", "consume", StopIteration), seen)
+
+    def test_multiple_tools_receive_same_event_and_disable_is_per_tool(self):
+        self.claim(TOOL, "pep669-aug-one")
+        self.claim(TOOL2, "pep669-aug-two")
+        counts = {"first": 0, "second": 0}
+
+        def target():
+            return "target"
+
+        def first(code, *args):
+            if code is target.__code__:
+                counts["first"] += 1
+                return sys.monitoring.DISABLE
+
+        def second(code, *args):
+            if code is target.__code__:
+                counts["second"] += 1
+
+        sys.monitoring.register_callback(TOOL, E.PY_START, first)
+        sys.monitoring.register_callback(TOOL2, E.PY_START, second)
+        sys.monitoring.set_events(TOOL, E.PY_START)
+        sys.monitoring.set_events(TOOL2, E.PY_START)
+        target()
+        target()
+        self.assertEqual(counts["first"], 1)
+        self.assertGreaterEqual(counts["second"], 2)
+
+        sys.monitoring.restart_events()
+        target()
+        self.assertEqual(counts["first"], 2)
+
+    def test_global_line_events_cover_loop_branch_and_exception_paths(self):
+        self.claim()
+        seen = []
+
+        def loop_branch(limit):
+            total = 0
+            for item in range(limit):
+                if item % 2:
+                    total += item
+                else:
+                    total -= item
+            return total
+
+        def exception_path():
+            try:
+                raise LookupError("tracked")
+            except LookupError:
+                return "handled"
+
+        def line_cb(code, line):
+            if code.co_name in {"loop_branch", "exception_path"}:
+                seen.append((code.co_name, line - code.co_firstlineno))
+
+        sys.monitoring.register_callback(TOOL, E.LINE, line_cb)
+        sys.monitoring.set_events(TOOL, E.LINE)
+        self.assertEqual(loop_branch(4), 2)
+        self.assertEqual(exception_path(), "handled")
+        sys.monitoring.set_events(TOOL, 0)
+
+        names = {name for name, _line in seen}
+        self.assertEqual(names, {"loop_branch", "exception_path"})
+        self.assertGreaterEqual(len([item for item in seen if item[0] == "loop_branch"]), 6)
+
+    def test_global_call_group_reports_c_return_and_c_raise(self):
+        self.claim()
+        seen = []
+
+        def call_cb(code, offset, func, arg):
+            seen.append(("call", getattr(func, "__name__", type(func).__name__)))
+
+        def return_cb(code, offset, func, arg):
+            seen.append(("return", getattr(func, "__name__", type(func).__name__)))
+
+        def c_raise_cb(code, offset, func, arg):
+            seen.append(("c_raise", getattr(func, "__name__", type(func).__name__)))
+
+        def workload():
+            data = []
+            data.append(1)
+            try:
+                int("not-an-int")
+            except ValueError:
+                pass
+            return len(data)
+
+        sys.monitoring.register_callback(TOOL, E.CALL, call_cb)
+        sys.monitoring.register_callback(TOOL, E.C_RETURN, return_cb)
+        sys.monitoring.register_callback(TOOL, E.C_RAISE, c_raise_cb)
+        sys.monitoring.set_events(TOOL, E.CALL)
+        self.assertEqual(workload(), 1)
+        sys.monitoring.set_events(TOOL, 0)
+
+        self.assertIn(("return", "append"), seen)
+        self.assertIn(("c_raise", "int"), seen)
+
+    def test_local_many_events_are_limited_to_target_code_object(self):
+        self.claim()
+        seen = []
+
+        def target(flag):
+            data = []
+            data.append(1)
+            try:
+                if flag:
+                    raise KeyError("flag")
+            except KeyError:
+                data.append(2)
+            return len(data)
+
+        def other():
+            return target(True)
+
+        def record(name):
+            def callback(code, *args):
+                if code.co_name in {"target", "other"}:
+                    seen.append((name, code.co_name))
+            return callback
+
+        for event, name in (
+            (E.LINE, "line"),
+            (E.INSTRUCTION, "instruction"),
+            (E.CALL, "call"),
+            (E.C_RETURN, "c_return"),
+            (E.RAISE, "raise"),
+            (E.EXCEPTION_HANDLED, "handled"),
+        ):
+            sys.monitoring.register_callback(TOOL, event, record(name))
+
+        mask = E.LINE | E.INSTRUCTION | E.CALL | E.RAISE | E.EXCEPTION_HANDLED
+        sys.monitoring.set_local_events(TOOL, target.__code__, mask)
+        self.assertEqual(other(), 2)
+        sys.monitoring.set_local_events(TOOL, target.__code__, 0)
+
+        self.assertIn(("line", "target"), seen)
+        self.assertIn(("instruction", "target"), seen)
+        self.assertIn(("call", "target"), seen)
+        self.assertIn(("c_return", "target"), seen)
+        self.assertIn(("raise", "target"), seen)
+        self.assertIn(("handled", "target"), seen)
+        self.assertNotIn(("line", "other"), seen)
+
+    def test_generator_resume_yield_throw_and_unwind_events(self):
+        self.claim()
+        seen = []
+
+        def managed_gen():
+            try:
+                yield "first"
+                yield "second"
+            except KeyError:
+                raise
+
+        def callback(name):
+            def record(code, *args):
+                if code.co_name == "managed_gen":
+                    seen.append(name)
+            return record
+
+        for event, name in (
+            (E.PY_START, "start"),
+            (E.PY_RESUME, "resume"),
+            (E.PY_YIELD, "yield"),
+            (E.PY_THROW, "throw"),
+            (E.PY_UNWIND, "unwind"),
+        ):
+            sys.monitoring.register_callback(TOOL, event, callback(name))
+
+        mask = E.PY_START | E.PY_RESUME | E.PY_YIELD | E.PY_THROW | E.PY_UNWIND
+        sys.monitoring.set_local_events(TOOL, managed_gen.__code__, mask)
+        iterator = managed_gen()
+        self.assertEqual(next(iterator), "first")
+        with self.assertRaises(KeyError):
+            iterator.throw(KeyError)
+        sys.monitoring.set_local_events(TOOL, managed_gen.__code__, 0)
+
+        self.assertIn("start", seen)
+        self.assertIn("yield", seen)
+        self.assertIn("throw", seen)
+        self.assertIn("unwind", seen)
+
+    def test_overlapping_local_line_events_for_two_tools(self):
+        self.claim(TOOL, "pep669-aug-line-one")
+        self.claim(TOOL2, "pep669-aug-line-two")
+        counts = {"first": 0, "second": 0}
+
+        def target():
+            total = 0
+            for item in (1, 2, 3):
+                total += item
+            return total
+
+        def first(code, line):
+            if code.co_name == "target":
+                counts["first"] += 1
+
+        def second(code, line):
+            if code.co_name == "target":
+                counts["second"] += 1
+
+        sys.monitoring.register_callback(TOOL, E.LINE, first)
+        sys.monitoring.register_callback(TOOL2, E.LINE, second)
+        sys.monitoring.set_local_events(TOOL, target.__code__, E.LINE)
+        sys.monitoring.set_local_events(TOOL2, target.__code__, E.LINE)
+        self.assertEqual(target(), 6)
+        sys.monitoring.set_local_events(TOOL, target.__code__, 0)
+        sys.monitoring.set_local_events(TOOL2, target.__code__, 0)
+
+        self.assertGreater(counts["first"], 2)
+        self.assertEqual(counts["first"], counts["second"])
+
+    def test_set_local_events_forces_reinstrumentation_when_up_to_date(self):
+        # Adding a local event to a code object that is ALREADY instrumented
+        # at the current monitoring version must still take effect: set_local_events
+        # has to force a re-instrumentation pass. The first call instruments the
+        # code (bringing its version up to date); the second adds INSTRUCTION
+        # while it is up to date, which must fire on the next call.
+        self.claim()
+        lines = []
+        insns = []
+
+        def target():
+            a = 1
+            b = a + 1
+            return b
+
+        sys.monitoring.register_callback(
+            TOOL, E.LINE,
+            lambda code, line: lines.append(line) if code is target.__code__ else None)
+        sys.monitoring.register_callback(
+            TOOL, E.INSTRUCTION,
+            lambda code, off: insns.append(off) if code is target.__code__ else None)
+
+        sys.monitoring.set_local_events(TOOL, target.__code__, E.LINE)
+        target()
+        self.assertTrue(lines)
+        self.assertFalse(insns)
+
+        lines.clear()
+        insns.clear()
+        sys.monitoring.set_local_events(
+            TOOL, target.__code__, E.LINE | E.INSTRUCTION)
+        target()
+        # Clear the local events while the tool is still claimed (the class
+        # tearDown frees the tool, so deferring this to addCleanup would race).
+        sys.monitoring.set_local_events(TOOL, target.__code__, 0)
+        self.assertTrue(
+            insns,
+            "added local INSTRUCTION events did not fire — set_local_events "
+            "failed to force re-instrumentation of an up-to-date code object")
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Lib/test/test_pep669_tracing_stability_aug.py b/Lib/test/test_pep669_tracing_stability_aug.py
new file mode 100644
--- /dev/null
+++ b/Lib/test/test_pep669_tracing_stability_aug.py
@@ -0,0 +1,86 @@
+import sys
+import unittest
+
+
+class TracingStabilityAugTest(unittest.TestCase):
+    def test_settrace_line_events_for_branching_function(self):
+        seen = []
+
+        def tracer(frame, event, arg):
+            if event == "line" and frame.f_code.co_name == "target":
+                seen.append(frame.f_lineno - frame.f_code.co_firstlineno)
+            return tracer
+
+        def target(flag):
+            total = 0
+            if flag:
+                total += 1
+            else:
+                total += 2
+            return total
+
+        old_trace = sys.gettrace()
+        try:
+            sys.settrace(tracer)
+            self.assertEqual(target(True), 1)
+            self.assertEqual(target(False), 2)
+        finally:
+            sys.settrace(old_trace)
+
+        self.assertIn(1, seen)
+        self.assertIn(2, seen)
+        self.assertIn(6, seen)
+        self.assertTrue({3, 5}.issubset(seen))
+
+    def test_setprofile_call_return_exception_shape(self):
+        seen = []
+
+        def profiler(frame, event, arg):
+            if frame.f_code.co_name in {"target", "leaf"}:
+                seen.append((event, frame.f_code.co_name, type(arg).__name__))
+            return profiler
+
+        def leaf():
+            raise RuntimeError("profile")
+
+        def target():
+            try:
+                leaf()
+            except RuntimeError:
+                return "ok"
+
+        old_profile = sys.getprofile()
+        try:
+            sys.setprofile(profiler)
+            self.assertEqual(target(), "ok")
+        finally:
+            sys.setprofile(old_profile)
+
+        self.assertIn(("call", "target", "NoneType"), seen)
+        self.assertIn(("call", "leaf", "NoneType"), seen)
+        self.assertIn(("return", "target", "str"), seen)
+
+    def test_call_tracing_preserves_existing_reentrant_trace_semantics(self):
+        calls = []
+
+        def traced(value):
+            calls.append(value)
+            return value * 2
+
+        self.assertEqual(sys.call_tracing(traced, (21,)), 42)
+        self.assertEqual(calls, [21])
+
+    def test_frame_trace_opcodes_roundtrip_existing_attribute(self):
+        frame = sys._getframe()
+        old_value = frame.f_trace_opcodes
+        try:
+            frame.f_trace_opcodes = True
+            self.assertIs(frame.f_trace_opcodes, True)
+            frame.f_trace_opcodes = False
+            self.assertIs(frame.f_trace_opcodes, False)
+        finally:
+            frame.f_trace_opcodes = old_value
+
+
+if __name__ == "__main__":
+    unittest.main()