diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index 9bd8528..4106ace 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -1,4 +1,8 @@
 ## 2025-02-21 - Path Traversal in Mix Endpoint API Parameter
 **Vulnerability:** The `/projects/{project_id}/mix` API endpoint in `src/audioformation/server/routes.py` accepted a `music` parameter (meant to specify a filename within the `05_MUSIC/generated` directory) but directly passed it to `mix_project` without sanitization. This allowed directory traversal payloads like `../../../etc/passwd` to be used for background music resolution.
 **Learning:** Even internal API inputs that map strictly to filenames inside an expected directory must be sanitized. A simple check for file existence (`if not bg_music_path.exists():`) is insufficient as it confirms existence but allows looking outside the bounded directory.
-**Prevention:** Always use established sanitization helpers (like `sanitize_filename`) or bound checks (like `validate_path_within`) for any user-supplied string that forms part of a filesystem path. Ensure bypass parameters like `FORCE_NO_MUSIC` are handled before and mutually exclusively from sanitization.
\ No newline at end of file
+**Prevention:** Always use established sanitization helpers (like `sanitize_filename`) or bound checks (like `validate_path_within`) for any user-supplied string that forms part of a filesystem path. Ensure bypass parameters like `FORCE_NO_MUSIC` are handled before and mutually exclusively from sanitization.
+## 2025-02-21 - Exception and Parameter Data Leakage in API Endpoints
+**Vulnerability:** Several API endpoints in `src/audioformation/server/routes.py` included raw user input or internal exception strings (`e`) directly within `HTTPException` detail responses. This could leak internal stack/state or echo unescaped user input back to the client.
+**Learning:** Returning unescaped dynamic parameters or internal exception details directly via HTTP responses bypasses defense-in-depth and violates secure error handling standards. Log the specifics on the backend instead.
+**Prevention:** Always log specific error details (`logger.error()`) internally, and return generic, static error messages to the client within `HTTPException`.
diff --git a/src/audioformation/server/routes.py b/src/audioformation/server/routes.py
index 34c9bec..0d71fd7 100644
--- a/src/audioformation/server/routes.py
+++ b/src/audioformation/server/routes.py
@@ -109,9 +109,8 @@ async def create_new_project(request: ProjectCreateRequest):
     """Create a new project."""
     project_id = request.id
     if project_exists(project_id):
-        raise HTTPException(
-            status_code=409, detail=f"Project '{project_id}' already exists."
-        )
+        logger.warning(f"Project '{project_id}' already exists.")
+        raise HTTPException(status_code=409, detail="Project already exists.")
 
     try:
         path = create_project(project_id)
@@ -185,7 +184,8 @@ async def ingest_files(
                 shutil.copyfileobj(file.file, buffer)
     except Exception as e:
         shutil.rmtree(tmp_dir, ignore_errors=True)
-        raise HTTPException(status_code=500, detail=f"Upload failed: {e}")
+        logger.error(f"Upload failed: {e}")
+        raise HTTPException(status_code=500, detail="Upload failed")
 
     background_tasks.add_task(
         _run_with_status,
@@ -244,9 +244,8 @@ async def preview_voice(project_id: str, request: PreviewRequest):
     try:
         engine = registry.get(request.engine)
     except KeyError:
-        raise HTTPException(
-            status_code=400, detail=f"Engine '{request.engine}' not found"
-        )
+        logger.warning(f"Engine '{request.engine}' not found")
+        raise HTTPException(status_code=400, detail="Engine not found")
 
     # Resolve reference audio if present
     ref_path = None
@@ -739,7 +738,8 @@ async def list_engine_voices(name: str, lang: Optional[str] = None):
         voices = await engine.list_voices(language=lang)
         return voices
     except KeyError:
-        raise HTTPException(status_code=404, detail=f"Engine '{name}' not found")
+        logger.warning(f"Engine '{name}' not found")
+        raise HTTPException(status_code=404, detail="Engine not found")
     except Exception as e:
         logger.error(f"Failed to list voices for engine {name}: {e}")
         raise HTTPException(status_code=500, detail="Internal server error")