[CI] (.github/workflows, scripts/ci, tools/trace_replay): check the verify control's reason in one script

- scripts/ci/retrace_verify_reason.py holds the retrace-verify control's reason check, a plain search for Fatal{PipeVerifyDiffer, "GetRenderStateParameters@ (run_trace_case.cmake prints the library log through message(STATUS), which never re-wraps, so the old prefix stripping and whitespace collapse are gone); the workflow step and test_run_trace_case.py both run it, so the test can no longer pass on a copy
- canned reds carrying a different Fatal (Fatal{UnmigratedPipeInput, "GetPixelStoreParameters@ReadPixels"}) or the comparator's divergence on another field (Fatal{PipeVerifyDiffer, "GetPixelStoreParameters@ReadPixels"}) must fail the check

.github/workflows/test.yml

@@ -3287,12 +3287,9 @@ jobs:
             echo "::error::MOBILEGL_PIPE_VERIFY_CORRUPT=GetRenderStateParameters left the OpenRA retrace GREEN, so the comparator is not comparing and the whole verify retrace lane proves nothing."
             exit 1
           fi
-          # Its own red: ctest -V prefixes every line with the test number, and CMake re-wraps text.
-          if ! sed -E 's/^[0-9]+: //' "${RUNNER_TEMP}/verify-control.txt" | tr -s '[:space:]' ' ' \
-               | grep -qF 'Fatal{PipeVerifyDiffer, "GetRenderStateParameters@'; then
-            echo "::error::the corrupted-snapshot retrace went red without Fatal{PipeVerifyDiffer, \"GetRenderStateParameters@...\"}: something other than the comparator failed it"
-            exit 1
-          fi
+          # Its red must carry the comparator's divergence on the corrupted field
+          # (scripts/ci/retrace_verify_reason.py, which test_run_trace_case.py runs on canned output).
+          python3 "${GITHUB_WORKSPACE}/scripts/ci/retrace_verify_reason.py" "${RUNNER_TEMP}/verify-control.txt"
           echo "the corrupted field turned the retrace red, as it must (ctest exit ${control_rc})"
 
       - name: Upload core dumps

scripts/ci/retrace_verify_reason.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+# MobileGL - scripts/ci/retrace_verify_reason.py
+# Copyright (c) 2025-2026 MobileGL-Dev
+# Licensed under the GNU Lesser General Public License v3.0:
+#   https://www.gnu.org/licenses/gpl-3.0.txt
+#   https://www.gnu.org/licenses/lgpl-3.0.txt
+# SPDX-License-Identifier: LGPL-3.0-only
+# End of Source File Header
+
+"""Whether retrace-verify's corrupted-snapshot control went red for its own reason.
+
+The control replays OpenRA with MOBILEGL_PIPE_VERIFY_CORRUPT=GetRenderStateParameters and must go
+red with the comparator's divergence on that field: a red without it (another Fatal, a divergence
+on another field) proves nothing about the comparator. The check requires that divergence in the
+transcript; it does not rule out other failures beside it. run_trace_case.cmake prints the library
+log through message(STATUS), which never re-wraps, so each log line stays one transcript line.
+
+Usage: retrace_verify_reason.py TRANSCRIPT    (the control run's ctest -V output)
+Exit 0 when the divergence is there, 1 when it is not, 2 when the transcript cannot be read.
+"""
+import sys
+
+REASON = 'Fatal{PipeVerifyDiffer, "GetRenderStateParameters@'
+
+
+def carries_reason(text):
+    return REASON in text
+
+
+def main(argv=None):
+    argv = sys.argv[1:] if argv is None else argv
+    if len(argv) != 1:
+        print(__doc__)
+        return 2
+    try:
+        text = open(argv[0], encoding='utf-8', errors='replace').read()
+    except OSError as error:
+        print(f'::error::retrace_verify_reason: cannot read {argv[0]}: {error}')
+        return 2
+    if carries_reason(text):
+        print(f'retrace_verify_reason: the red carries {REASON}...')
+        return 0
+    print(f'::error::the corrupted-snapshot retrace went red without {REASON}...: '
+          'something other than the comparator failed it')
+    return 1
+
+
+if __name__ == '__main__':
+    sys.exit(main())

tools/trace_replay/test_run_trace_case.py

@@ -29,6 +29,7 @@ import unittest
 HERE = Path(__file__).resolve().parent
 SCRIPT = HERE / 'run_trace_case.cmake'
 CHECKER = HERE.parents[1] / 'scripts' / 'ci' / 'retrace_split_evidence.py'
+VERIFY_REASON = HERE.parents[1] / 'scripts' / 'ci' / 'retrace_verify_reason.py'
 sys.path.insert(0, str(CHECKER.parent))
 import retrace_split_evidence as checker  # noqa: E402
 
@@ -60,10 +61,6 @@ with open(os.path.join(out, 'result.json'), 'w') as result:
     json.dump({'passed': True, 'ssim': 1.0}, result)
 '''
 
-# The retrace-verify control's reason check, as the workflow runs it on the tee'd ctest -V output.
-VERIFY_CONTROL_REASON = ("sed -E 's/^[0-9]+: //' \"$1\" | tr -s '[:space:]' ' ' "
-                         "| grep -qF 'Fatal{PipeVerifyDiffer, \"GetRenderStateParameters@'")
-
 PREFIX = '[12:00:00] [Linux mobilegl_trace_/INFO]: '
 MARKER = {
     'inproc': 'Config: MOBILEGL_TRANSPORT=inproc - the MGPipe record stream crosses a real ring to an apply thread',
@@ -307,17 +304,24 @@ class RunTraceCaseTests(unittest.TestCase):
 
     def test_v4_an_aborted_verify_run_names_its_divergence(self):
         # The comparator aborts the replay before result.json, so the script dumps the library log;
-        # the retrace-verify control requires that dump to carry the divergence it caused.
+        # the retrace-verify control requires that dump to carry the divergence it caused, through
+        # the same scripts/ci/retrace_verify_reason.py the workflow runs. Another Fatal is not it,
+        # and neither is the comparator's divergence on a field the control did not corrupt.
         fatal = 'MGPipe: Fatal{PipeVerifyDiffer, "GetRenderStateParameters@Clear"} field=3 where=entry'
+        other = 'MGPipe: Fatal{UnmigratedPipeInput, "GetPixelStoreParameters@ReadPixels"}'
+        other_field = 'MGPipe: Fatal{PipeVerifyDiffer, "GetPixelStoreParameters@ReadPixels"} field=1 where=entry'
         env = {'MOBILEGL_PIPE_VERIFY': '1', 'STUB_ABORT': '1'}
         rc, output = self.run_case(env, {'mobilegl.log': lines('MGPipe: verify armed', fatal)})
         self.assertNotEqual(rc, 0, output)
         transcript = self.root / 'control.txt'
-        for log, expected in ((lines('MGPipe: verify armed', fatal), 0), (lines('MGPipe: verify armed'), 1)):
+        for log, expected in ((lines('MGPipe: verify armed', fatal), 0), (lines('MGPipe: verify armed'), 1),
+                              (lines('MGPipe: verify armed', other), 1),
+                              (lines('MGPipe: verify armed', other_field), 1)):
             _, raw = self.run_case(env, {'mobilegl.log': log}, squashed=False)
             transcript.write_text(''.join('1: ' + row + '\n' for row in raw.splitlines()))
-            check = subprocess.run(['bash', '-c', VERIFY_CONTROL_REASON, 'reason', str(transcript)])
-            self.assertEqual(check.returncode, expected, raw)
+            check = subprocess.run([sys.executable, str(VERIFY_REASON), str(transcript)],
+                                   capture_output=True, text=True)
+            self.assertEqual(check.returncode, expected, raw + check.stdout)
 
     def test_v3_verify_green(self):
         rc, output = self.run_case({'MOBILEGL_PIPE_VERIFY': '1'}, {'mobilegl.log': lines('MGPipe: verify armed')})