fix(security): redact key detector dependency failures

CHANGELOG.md

@@ -7,6 +7,10 @@
 - Display the analyzed song tempo (BPM) as a badge in the rehearsal workspace.
 - 각 합주 역할(Role)별 개인 연습 진행도를 0~100% 범위로 기록 및 시각화할 수 있는 연습 진척도(`practiceProgress`) 트래커 기능 추가. UI 컨트롤(슬라이더 및 +/- 버튼)과 한/영 다국어 지원 포함.
 
+### Fixed
+
+- Keep unexpected key-detection dependency failures out of routine log payloads while retaining bounded operation and exception-class diagnostics.
+
 ## [0.1.3] - 2026-04-29
 
 ### Fixed

services/analysis-engine/src/bandscope_analysis/chords/key_detector.py

@@ -60,6 +60,8 @@ class KeyDetector:
     - Bounded by the size of the passed input array.
     - Safe failure: degenerate input returns an empty result and no exception
       is allowed to escape ``detect``.
+    - Unexpected dependency failures log only the operation and exception
+      class; dependency messages and tracebacks stay out of routine logs.
     """
 
     def detect(self, audio: np.ndarray, sr: int) -> KeyResult:
@@ -83,8 +85,11 @@ def detect(self, audio: np.ndarray, sr: int) -> KeyResult:
             # detection deterministic and avoids an unstable native pitch-track
             # code path on pure synthetic tones.
             chroma = librosa.feature.chroma_cqt(y=audio, sr=sr, tuning=0.0)
-        except Exception:  # noqa: BLE001 - safe failure: never raise to caller.
-            logger.exception("chroma_cqt failed during key detection")
+        except Exception as error:  # noqa: BLE001 - safe failure: never raise to caller.
+            logger.error(
+                "chroma_cqt failed during key detection: %s",
+                type(error).__name__,
+            )
             return _empty_result()
 
         if chroma.size == 0:

services/analysis-engine/tests/test_key_detector.py

@@ -3,6 +3,7 @@
 from unittest.mock import patch
 
 import numpy as np
+import pytest
 
 from bandscope_analysis.chords.key_detector import (
     KeyDetector,
@@ -85,12 +86,18 @@ def test_detect_empty_audio() -> None:
     assert result == {"key": "", "tonic": "", "mode": "", "confidence": 0.0}
 
 
-def test_detect_chroma_cqt_exception() -> None:
-    """A failure inside chroma_cqt yields the empty result and never raises."""
+def test_detect_chroma_cqt_exception(caplog: pytest.LogCaptureFixture) -> None:
+    """A dependency failure stays payload-safe in routine key-detection logs."""
     audio = _tone(_NOTE_FREQS["C"], 1.0)
-    with patch("librosa.feature.chroma_cqt", side_effect=RuntimeError("boom")):
+    sensitive_detail = "/Users/Alice/private-song.wav token=super-secret"
+    with patch("librosa.feature.chroma_cqt", side_effect=RuntimeError(sensitive_detail)):
         result = KeyDetector().detect(audio, SAMPLE_RATE)
+
     assert result == _empty_result()
+    assert "chroma_cqt failed during key detection" in caplog.text
+    assert "/Users/Alice" not in caplog.text
+    assert "private-song.wav" not in caplog.text
+    assert "super-secret" not in caplog.text
 
 
 def test_detect_empty_chroma() -> None: