diff --git a/src/koru/queue/ticket.py b/src/koru/queue/ticket.py
index 03a44eb7..9a5b7319 100644
--- a/src/koru/queue/ticket.py
+++ b/src/koru/queue/ticket.py
@@ -14,6 +14,7 @@
 from pathlib import Path
 from typing import Any
 
+from koru.queue.runners import _decode_subprocess_output
 from koru.queue.types import CommandResult
 
 
@@ -207,7 +208,7 @@ def _python_has_planfile_cli(python: str) -> bool:
                 ),
             ],
             capture_output=True,
-            text=True,
+            text=False,
             timeout=5,
             check=False,
         )
@@ -247,12 +248,15 @@ def _planfile_supports_structured_queue_json(executable: str) -> bool:
             [executable, "--version"],
             check=False,
             capture_output=True,
-            text=True,
+            text=False,
             timeout=2,
         )
     except (OSError, subprocess.SubprocessError):
         return True
-    version = _parse_version_tuple(f"{result.stdout}\n{result.stderr}")
+    version = _parse_version_tuple(
+        f"{_decode_subprocess_output(result.stdout)}\n"
+        f"{_decode_subprocess_output(result.stderr)}"
+    )
     if version is None:
         return True
     return version >= _MIN_STRUCTURED_QUEUE_PLANFILE_VERSION
@@ -330,7 +334,7 @@ def _configured_planfile_cmd_usable(configured: str) -> bool:
         proc = subprocess.run(
             [*parts, "--version"],
             capture_output=True,
-            text=True,
+            text=False,
             timeout=5,
             check=False,
         )
@@ -338,7 +342,10 @@ def _configured_planfile_cmd_usable(configured: str) -> bool:
         return True
     if proc.returncode == 0:
         return True
-    text = f"{proc.stdout}\n{proc.stderr}".lower()
+    text = (
+        f"{_decode_subprocess_output(proc.stdout)}\n"
+        f"{_decode_subprocess_output(proc.stderr)}"
+    ).lower()
     return not any(marker in text for marker in _PLANFILE_MODULE_MISSING_MARKERS)
 
 
diff --git a/tests/test_planfile_queue.py b/tests/test_planfile_queue.py
index 089d2b1e..22f5df74 100644
--- a/tests/test_planfile_queue.py
+++ b/tests/test_planfile_queue.py
@@ -13,7 +13,12 @@
 
 from koru.cqrs.event_store import JsonlEventStore
 from koru.queue import run_next_planfile_task
-from koru.queue.ticket import parse_next_ticket, planfile_command
+from koru.queue.ticket import (
+    _configured_planfile_cmd_usable,
+    _planfile_supports_structured_queue_json,
+    parse_next_ticket,
+    planfile_command,
+)
 from tests import _repolab
 
 
@@ -27,6 +32,52 @@ def _ticket_args(command: list[str]) -> list[str]:
 
 
 class TestPlanfileCommand(unittest.TestCase):
+    def test_structured_queue_probe_handles_non_utf8_bytes(self) -> None:
+        _planfile_supports_structured_queue_json.cache_clear()
+        with patch(
+            "koru.queue.ticket.subprocess.run",
+            return_value=SimpleNamespace(
+                returncode=0,
+                stdout=b"planfile wersja \xf3 0.1.101",
+                stderr=b"",
+            ),
+        ) as run:
+            self.assertTrue(_planfile_supports_structured_queue_json("/tmp/planfile"))
+        self.assertFalse(run.call_args.kwargs["text"])
+        _planfile_supports_structured_queue_json.cache_clear()
+        with patch(
+            "koru.queue.ticket.subprocess.run",
+            return_value=SimpleNamespace(
+                returncode=0,
+                stdout=b"planfile wersja \xf3 0.1.99",
+                stderr=b"",
+            ),
+        ):
+            self.assertFalse(_planfile_supports_structured_queue_json("/tmp/planfile-old"))
+
+    def test_configured_command_probe_handles_non_utf8_module_missing_marker(self) -> None:
+        _configured_planfile_cmd_usable.cache_clear()
+        with patch(
+            "koru.queue.ticket.subprocess.run",
+            return_value=SimpleNamespace(
+                returncode=1,
+                stdout=b"",
+                stderr=b"\xf3 no module named 'planfile.cli'",
+            ),
+        ) as run:
+            self.assertFalse(_configured_planfile_cmd_usable("/tmp/venv/bin/python -m planfile.cli"))
+        self.assertFalse(run.call_args.kwargs["text"])
+        _configured_planfile_cmd_usable.cache_clear()
+        with patch(
+            "koru.queue.ticket.subprocess.run",
+            return_value=SimpleNamespace(
+                returncode=0,
+                stdout=b"\xf3 planfile 0.1.101",
+                stderr=b"",
+            ),
+        ):
+            self.assertTrue(_configured_planfile_cmd_usable("/tmp/venv/bin/python -m planfile.cli"))
+
     def test_prefers_local_planfile_before_importable_module_from_active_env(self) -> None:
         with tempfile.TemporaryDirectory() as tmp_dir:
             root = Path(tmp_dir)