gh-157788: Fix python -m asyncio ps failing on long task names

Lib/test/test_external_inspection.py

@@ -1,3 +1,4 @@
+import asyncio
 import unittest
 import os
 import textwrap
@@ -440,6 +441,22 @@ def _extract_coroutine_stacks_lineno_only(self, stack_trace):
 
 @requires_remote_subprocess_debugging()
 class TestSelfStackTrace(RemoteInspectionTestBase):
+    @skip_if_not_supported
+    def test_long_task_name_is_truncated(self):
+        # gh-157788
+        async def main():
+            asyncio.create_task(asyncio.sleep(10_000), name="x" * 300)
+            await asyncio.sleep(0)
+            return [
+                task.task_name
+                for info in RemoteUnwinder(os.getpid()).get_all_awaited_by()
+                for task in info.awaited_by
+            ]
+
+        names = asyncio.run(main())
+        self.assertIn("Task-1", names)
+        self.assertEqual([len(n) for n in names if n.startswith("x")], [255])
+
     @skip_if_not_supported
     @unittest.skipIf(
         sys.platform == "linux" and not PROCESS_VM_READV_SUPPORTED,

Misc/NEWS.d/next/Library/2026-09-19-14-10-18.gh-issue-157788.v70Lxd.rst

@@ -0,0 +1,2 @@
+Fix ``python -m asyncio ps`` failing on a process that has a task with a
+name longer than 255 characters.

Modules/_remote_debugging/object_reading.c

@@ -64,12 +64,16 @@ read_py_str(
     }
 
     Py_ssize_t len = GET_MEMBER(Py_ssize_t, unicode_obj, unwinder->debug_offsets.unicode_object.length);
-    if (len < 0 || len > max_len) {
+    if (len < 0) {
         PyErr_Format(PyExc_RuntimeError,
                      "Invalid string length (%zd) at 0x%lx", len, address);
         set_exception_cause(unwinder, PyExc_RuntimeError, "Invalid string length in remote Unicode object");
         return NULL;
     }
+    if (len > max_len) {
+        // gh-157788: a long name must not fail the whole read
+        len = max_len;
+    }
 
     // Inspect state to pick the right data offset and character width.
     // We rely on the remote process sharing this Python version's