From cd9f5911465407b10fccba591dc423250f0f57c4 Mon Sep 17 00:00:00 2001
From: Augustin Bozzetto <84289411+augboz@users.noreply.github.com>
Date: Sun, 28 Jun 2026 16:28:59 +0200
Subject: [PATCH 1/2] Detach stdin when running badfiles checker commands

The `badfiles` checker commands (mp3val, flac, custom) are non-interactive,
but were launched with the parent process's stdin still attached to the
controlling terminal. A checker could leave the TTY in a modified state
(e.g. with input echo disabled), so after `beet bad` the terminal stopped
echoing typed input until `reset` or `stty sane` was run.

Pass `stdin=DEVNULL` to `check_output` so the checkers cannot read from or
modify the terminal. Adds a regression test asserting `run_command`
detaches stdin, plus a changelog entry.

Closes #6750
---
 beetsplug/badfiles.py         | 13 +++++++++++--
 docs/changelog.rst            |  4 ++++
 test/plugins/test_badfiles.py | 14 ++++++++++++++
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/beetsplug/badfiles.py b/beetsplug/badfiles.py
index beec8eae33..2f58ac6d1d 100644
--- a/beetsplug/badfiles.py
+++ b/beetsplug/badfiles.py
@@ -18,7 +18,13 @@
 import os
 import shlex
 import sys
-from subprocess import STDOUT, CalledProcessError, check_output, list2cmdline
+from subprocess import (
+    DEVNULL,
+    STDOUT,
+    CalledProcessError,
+    check_output,
+    list2cmdline,
+)
 from typing import Literal
 
 import confuse
@@ -66,7 +72,10 @@ def run_command(self, cmd):
             "running command: {}", displayable_path(list2cmdline(cmd))
         )
         try:
-            output = check_output(cmd, stderr=STDOUT)
+            # The checker commands are non-interactive, so detach stdin from
+            # the controlling terminal. Otherwise a checker may leave the TTY
+            # in a modified state (e.g. with echo disabled). See #6750.
+            output = check_output(cmd, stderr=STDOUT, stdin=DEVNULL)
             errors = 0
             status = 0
         except CalledProcessError as e:
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 2609ce8fa9..8cd718f346 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -34,6 +34,10 @@ Bug fixes
   example a multi-disc album whose cover lives in the album root rather than a
   per-disc directory); the missing art is skipped instead. :bug:`4692`
 - :doc:`plugins/tidal`: Normalize Tidal album types to lowercase.
+- :doc:`plugins/badfiles`: Detach stdin from the controlling terminal when
+  running checker commands, so a checker can no longer leave the terminal in a
+  modified state (e.g. with input echo disabled) after ``beet bad``.
+  :bug:`6750`
 
 ..
     For plugin developers
diff --git a/test/plugins/test_badfiles.py b/test/plugins/test_badfiles.py
index 8b88f72041..6aec21c45c 100644
--- a/test/plugins/test_badfiles.py
+++ b/test/plugins/test_badfiles.py
@@ -14,6 +14,7 @@
 
 """Tests for the 'badfiles' plugin."""
 
+from subprocess import DEVNULL
 from types import SimpleNamespace
 from unittest.mock import patch
 
@@ -46,3 +47,16 @@ def test_non_quiet_import_calls_prompt(self):
             result = plugin.on_import_task_before_choice(task, session=None)
 
         assert result == importer.Action.SKIP
+
+    def test_run_command_detaches_stdin(self):
+        # The checker commands are non-interactive; run_command must detach
+        # stdin from the terminal so a checker cannot leave the TTY in a
+        # modified state (e.g. with echo disabled). See #6750.
+        plugin = BadFiles()
+
+        with patch(
+            "beetsplug.badfiles.check_output", return_value=b""
+        ) as mock_check_output:
+            plugin.run_command(["mp3val", "foo.mp3"])
+
+        assert mock_check_output.call_args.kwargs["stdin"] is DEVNULL

From 2c011fe49d39ea4d925bdabec367cec67aedc2d3 Mon Sep 17 00:00:00 2001
From: Augustin Bozzetto <84289411+augboz@users.noreply.github.com>
Date: Sun, 28 Jun 2026 16:41:34 +0200
Subject: [PATCH 2/2] Reflow changelog entry to satisfy docstrfmt (line-length
 80)

---
 docs/changelog.rst | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 8cd718f346..b989ac0fa2 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -36,8 +36,7 @@ Bug fixes
 - :doc:`plugins/tidal`: Normalize Tidal album types to lowercase.
 - :doc:`plugins/badfiles`: Detach stdin from the controlling terminal when
   running checker commands, so a checker can no longer leave the terminal in a
-  modified state (e.g. with input echo disabled) after ``beet bad``.
-  :bug:`6750`
+  modified state (e.g. with input echo disabled) after ``beet bad``. :bug:`6750`
 
 ..
     For plugin developers