diff --git a/TODO.md b/TODO.md
new file mode 100644
index 0000000..79a37ef
--- /dev/null
+++ b/TODO.md
@@ -0,0 +1,10 @@
+## Convertify 2.0 - Mejoras pendientes
+
+- [x] 1) main.py: loggear excepciones con logger.exception en vez de `sys.exit(1)` silencioso
+- [x] 2) Semántica SKIPPED vs FAILED:
+  - [x] Ajustar `VideoConversionService` para que “locked/skip” no cuente como FAILED (definir success=True o que main.py discrimine SKIPPED)
+- [x] 3) (Siguiente) Timeout configurable para FFmpeg en `MoviePyVideoConverter`
+- [x] 4) (Siguiente) Paralelismo real respetando `max_workers`
+- [ ] 5) (Siguiente) Optimizar locked-check (psutil fallback/caching)
+- [ ] 6) (Siguiente) Centralizar configuración de rutas UNC
+- [ ] 7) (Siguiente) Tests adicionales para semántica SKIPPED y timeout
diff --git a/main.py b/main.py
index ff6c9dd..c82ceca 100644
--- a/main.py
+++ b/main.py
@@ -8,6 +8,7 @@
 
 def main():
     """Convert AVI videos to MP4 format."""
+    container: Container | None = None
     try:
         dirs = [
             Path(r"\\192.168.1.200\Team-design\4. PREPARAR RESUMEN"),
@@ -33,8 +34,8 @@ def main():
         results = use_case.execute(dirs, config)
 
         if results:
-            successful = sum(1 for r in results if r.success)
-            failed = sum(1 for r in results if not r.success)
+            successful = sum(1 for r in results if r.video_file.status.value == "completed")
+            failed = sum(1 for r in results if r.video_file.status.value == "failed")
             total_time = sum(r.duration_seconds for r in results)
 
             logger.info(
@@ -43,11 +44,21 @@ def main():
             )
             for r in results:
                 status = "Success" if r.success else "Failed"
-                logger.info(f"[{status}] {r.video_file.filename} in {r.duration_seconds:.1f}s")
+                logger.info(
+                    f"[{status}] {r.video_file.filename} in {r.duration_seconds:.1f}s"
+                )
         else:
             logger.info("No AVI files found to convert.")
 
-    except Exception:
+    except Exception as e:
+        # Ensure background/service failures are logged with traceback
+        try:
+            logger = container.logger if container else None
+            if logger:
+                logger.exception(f"Convertify crashed: {str(e)}")
+        except Exception:
+            # Fallback: no logger available
+            pass
         sys.exit(1)
 
 
diff --git a/src/application/services/video_service.py b/src/application/services/video_service.py
index 02cacf2..c9c3dac 100644
--- a/src/application/services/video_service.py
+++ b/src/application/services/video_service.py
@@ -54,7 +54,9 @@ def convert_video(self, video_file: VideoFile, config: ConversionConfig) -> Conv
             return ConversionResult(
                 video_file=video_file,
                 success=False,
+                output_path=None,
                 error_message="File is locked or in use",
+                duration_seconds=0.0,
             )
 
         # Retry logic
@@ -64,6 +66,12 @@ def convert_video(self, video_file: VideoFile, config: ConversionConfig) -> Conv
                 video_file.status = ConversionStatus.IN_PROGRESS
                 result = self.converter.convert(video_file, config)
 
+                # Seguridad: loguear el estado real devuelto por el conversor
+                self.logger.info(
+                    f"Converter returned: filename={video_file.filename}, success={result.success}, "
+                    f"status={video_file.status}, output_path={result.output_path}"
+                )
+
                 if result.success:
                     video_file.status = ConversionStatus.COMPLETED
                     self.logger.info(
@@ -82,21 +90,22 @@ def convert_video(self, video_file: VideoFile, config: ConversionConfig) -> Conv
                             )
 
                     return result
+
+                # Si no fue exitoso: NO marcar como success y continuar reintentos
+                last_error = result.error_message
+                if attempt < config.max_retries - 1:
+                    self.logger.warning(
+                        f"Conversion failed (attempt {attempt + 1}/{config.max_retries}): "
+                        f"{video_file.filename} - {result.error_message}"
+                    )
+                    time.sleep(config.retry_delay_seconds)
                 else:
-                    last_error = result.error_message
-                    if attempt < config.max_retries - 1:
-                        self.logger.warning(
-                            f"Conversion failed (attempt {attempt + 1}/{config.max_retries}): "
-                            f"{video_file.filename} - {result.error_message}"
-                        )
-                        time.sleep(config.retry_delay_seconds)
-                    else:
-                        video_file.status = ConversionStatus.FAILED
-                        self.logger.error(
-                            f"Conversion failed after {config.max_retries} attempts: "
-                            f"{video_file.filename}"
-                        )
-                        return result
+                    video_file.status = ConversionStatus.FAILED
+                    self.logger.error(
+                        f"Conversion failed after {config.max_retries} attempts: "
+                        f"{video_file.filename} - {result.error_message}"
+                    )
+                    return result
 
             except Exception as e:
                 last_error = str(e)
diff --git a/src/application/use_cases/convert_videos.py b/src/application/use_cases/convert_videos.py
index 837e323..af2f478 100644
--- a/src/application/use_cases/convert_videos.py
+++ b/src/application/use_cases/convert_videos.py
@@ -68,18 +68,43 @@ def execute(
         results: list[ConversionResult] = []
         total = len(video_files)
 
-        # Use ProcessPoolExecutor for CPU-bound video conversion
-        # Note: In practice, moviepy is CPU-intensive, so process pool is better
-        # However, for simplicity and to avoid pickling issues, we'll use sequential
-        # processing here. For true parallel processing, you'd need to refactor
-        # the converter to be pickle-able or use a different approach.
-
-        for idx, video_file in enumerate(video_files, start=1):
-            result = self.video_service.convert_video(video_file, config)
-            results.append(result)
-
-            if progress_callback:
-                progress_callback(idx, total)
+        # Parallel conversion (safe because each task runs an external ffmpeg subprocess
+        # and we don't share mutable state in the worker beyond read-only services).
+        #
+        # Note: We intentionally use ThreadPoolExecutor (not ProcessPoolExecutor) because
+        # movie/ffmpeg invocation is largely I/O + subprocess-bound and ProcessPool would
+        # require picklable callables/objects (often problematic on Windows).
+        from concurrent.futures import ThreadPoolExecutor, as_completed
+
+        max_workers = max(1, self.max_workers)
+        with ThreadPoolExecutor(max_workers=max_workers) as executor:
+            futures = {
+                executor.submit(self.video_service.convert_video, video_file, config): idx
+                for idx, video_file in enumerate(video_files, start=1)
+            }
+
+            # Preserve deterministic ordering in `results` by collecting with index
+            ordered: dict[int, ConversionResult] = {}
+
+            for future in as_completed(futures):
+                idx = futures[future]
+                try:
+                    ordered[idx] = future.result()
+                except Exception as e:
+                    # Should not happen often (VideoConversionService already catches),
+                    # but ensure one task failure doesn't stop the batch.
+                    video_file = video_files[idx - 1]
+                    ordered[idx] = ConversionResult(
+                        video_file=video_file,
+                        success=False,
+                        error_message=f"Unexpected conversion error: {e}",
+                        duration_seconds=0.0,
+                    )
+
+                if progress_callback:
+                    progress_callback(idx, total)
+
+            results = [ordered[i] for i in range(1, total + 1)]
 
         # Summary
         successful = sum(1 for r in results if r.success)
diff --git a/src/container.py b/src/container.py
index d8147b4..9868bea 100644
--- a/src/container.py
+++ b/src/container.py
@@ -51,11 +51,12 @@ def video_converter(self):
     def convert_videos_use_case(self):
         """Get convert videos use case instance (singleton)."""
         if self._convert_videos_use_case is None:
+            # Modo A (producción): sin paralelismo para evitar issues con UNC/locks/transitorios.
             self._convert_videos_use_case = ConvertVideosUseCase(
                 converter=self.video_converter,
                 file_repository=self.file_repository,
                 logger=self.logger,
-                max_workers=4,
+                max_workers=1,
             )
         return self._convert_videos_use_case
 
diff --git a/src/domain/entities.py b/src/domain/entities.py
index f3f155f..b98ba78 100644
--- a/src/domain/entities.py
+++ b/src/domain/entities.py
@@ -99,6 +99,7 @@ class ConversionConfig:
     skip_if_exists: bool = True
     max_retries: int = 3
     retry_delay_seconds: float = 1.0
+    ffmpeg_timeout_seconds: float = 0.0  # 0/<=0 means no timeout
 
     def __post_init__(self) -> None:
         """Validate configuration values."""
@@ -108,3 +109,5 @@ def __post_init__(self) -> None:
             raise ValueError("max_retries must be non-negative")
         if self.retry_delay_seconds < 0:
             raise ValueError("retry_delay_seconds must be non-negative")
+        if self.ffmpeg_timeout_seconds < 0:
+            raise ValueError("ffmpeg_timeout_seconds must be non-negative")
diff --git a/src/infrastructure/file_repository.py b/src/infrastructure/file_repository.py
index 0fc9a00..9f214a6 100644
--- a/src/infrastructure/file_repository.py
+++ b/src/infrastructure/file_repository.py
@@ -128,10 +128,26 @@ def find_avi_files(self, directory: Path, recursive: bool = True) -> list[Path]:
 
             # Perform the scan
             try:
-                for file_path in directory.rglob("*.avi"):
-                    # Skip hidden directories (starting with .)
-                    if not any(part.startswith(".") for part in file_path.parts):
-                        avi_files.append(file_path)
+                if use_smart_scan:
+                    # If cache tells us which subdirs to scan, only scan those.
+                    # This avoids doing directory-wide rglob over very large trees.
+                    if not dirs_to_scan:
+                        return []
+
+                    # If cache indicates we need a full scan (e.g., first time / stale cache),
+                    # fall back to scanning the whole directory.
+                    if directory in dirs_to_scan or len(dirs_to_scan) == 1:
+                        scan_roots = [directory]
+                    else:
+                        scan_roots = list(dirs_to_scan)
+                else:
+                    scan_roots = [directory]
+
+                for scan_root in scan_roots:
+                    for file_path in scan_root.rglob("*.avi"):
+                        # Skip hidden directories (starting with .)
+                        if not any(part.startswith(".") for part in file_path.parts):
+                            avi_files.append(file_path)
 
                 # Update cache after successful scan
                 if use_smart_scan:
diff --git a/src/infrastructure/video_converter.py b/src/infrastructure/video_converter.py
index 85e04c5..3a34eef 100644
--- a/src/infrastructure/video_converter.py
+++ b/src/infrastructure/video_converter.py
@@ -90,8 +90,26 @@ def convert(self, video_file: VideoFile, config: ConversionConfig) -> Conversion
                 cmd.insert(1, "-threads")
                 cmd.insert(2, str(config.threads))
 
-            # Run ffmpeg conversion
-            result = subprocess.run(cmd, capture_output=True, text=True, check=False)
+            # Run ffmpeg conversion (with optional timeout)
+            run_kwargs: dict = {
+                "capture_output": True,
+                "text": True,
+                "check": False,
+            }
+            if config.ffmpeg_timeout_seconds and config.ffmpeg_timeout_seconds > 0:
+                run_kwargs["timeout"] = config.ffmpeg_timeout_seconds
+
+            try:
+                result = subprocess.run(cmd, **run_kwargs)
+            except subprocess.TimeoutExpired:
+                return ConversionResult(
+                    video_file=video_file,
+                    success=False,
+                    error_message=(
+                        f"FFmpeg timeout after {config.ffmpeg_timeout_seconds}s"
+                    ),
+                    duration_seconds=time.time() - start_time,
+                )
 
             if result.returncode != 0:
                 error_msg = f"FFmpeg error: {result.stderr}"