feat: auto-register existing TTS backends

- Add create_kokoro_backend() factory in kokoro.py
- Add create_supertonic_backend() factory in supertonic.py
- Auto-discover backend modules in __init__.py via pkgutil
- Both backends register themselves on import
- Tests verify registration and factory callables

abogen/tts_backends/__init__.py

@@ -0,0 +1,20 @@
+"""TTS backends package.
+
+Backend modules are auto-discovered and imported here.
+Each backend module registers itself with the global registry
+when imported.
+"""
+
+import importlib
+import pkgutil
+
+
+def _discover_backends():
+    """Import all modules in this package to trigger their registration."""
+    package = __name__
+    for _importer, modname, _ispkg in pkgutil.iter_modules(path=__path__):
+        importlib.import_module(f"{package}.{modname}")
+
+
+_discover_backends()
+

abogen/tts_backends/kokoro.py

@@ -3,3 +3,35 @@ def load_numpy_kpipeline():
     from kokoro import KPipeline  # type: ignore[import-not-found]
 
     return np, KPipeline
+
+
+def create_kokoro_backend(**kwargs):
+    """Create a Kokoro TTS backend instance.
+
+    Args:
+        lang_code: Language code (e.g. "a" for American English).
+        repo_id: HuggingFace repo id. Defaults to "hexgrad/Kokoro-82M".
+        device: Device to use ("cpu", "cuda", "mps"). Defaults to "cpu".
+
+    Returns:
+        KPipeline instance.
+    """
+    _np, KPipeline = load_numpy_kpipeline()
+    return KPipeline(
+        lang_code=kwargs["lang_code"],
+        repo_id=kwargs.get("repo_id", "hexgrad/Kokoro-82M"),
+        device=kwargs.get("device", "cpu"),
+    )
+
+
+from abogen.tts_backend import TTSBackendMetadata
+from abogen.tts_backend_registry import register_backend
+
+register_backend(
+    metadata=TTSBackendMetadata(
+        id="kokoro",
+        name="Kokoro",
+        description="Kokoro TTS engine",
+    ),
+    factory=create_kokoro_backend,
+)

abogen/tts_backends/supertonic.py

@@ -273,3 +273,34 @@ class SupertonicPipeline:
                 audio = _resample_linear(audio, src_rate, self.sample_rate)
 
             yield SupertonicSegment(graphemes=chunk_to_speak, audio=audio)
+
+
+def create_supertonic_backend(**kwargs):
+    """Create a SuperTonic TTS backend instance.
+
+    Args:
+        sample_rate: Audio sample rate. Defaults to 24000.
+        auto_download: Auto-download models. Defaults to True.
+        total_steps: Inference steps. Defaults to 5.
+
+    Returns:
+        SupertonicPipeline instance.
+    """
+    return SupertonicPipeline(
+        sample_rate=kwargs.get("sample_rate", 24000),
+        auto_download=kwargs.get("auto_download", True),
+        total_steps=kwargs.get("total_steps", 5),
+    )
+
+
+from abogen.tts_backend import TTSBackendMetadata
+from abogen.tts_backend_registry import register_backend
+
+register_backend(
+    metadata=TTSBackendMetadata(
+        id="supertonic",
+        name="SuperTonic",
+        description="SuperTonic TTS engine",
+    ),
+    factory=create_supertonic_backend,
+)

tests/test_tts_backend.py

@@ -97,3 +97,53 @@ class TestTTSBackendRegistry:
         result = registry.get_metadata("x")
         assert result.name == "V2"
         assert registry.create_backend("x") == "v2"
+
+
+class TestBackendRegistration:
+    """Tests that existing backends are auto-registered."""
+
+    def test_import_triggers_registration(self):
+        import abogen.tts_backends  # noqa: F401
+
+        from abogen.tts_backend_registry import _registry
+
+        backends = _registry.list_backends()
+        ids = [b.id for b in backends]
+        assert "kokoro" in ids
+        assert "supertonic" in ids
+
+    def test_kokoro_metadata(self):
+        import abogen.tts_backends  # noqa: F401
+
+        from abogen.tts_backend_registry import _registry
+
+        meta = _registry.get_metadata("kokoro")
+        assert meta.id == "kokoro"
+        assert meta.name == "Kokoro"
+        assert "Kokoro" in meta.description
+
+    def test_supertonic_metadata(self):
+        import abogen.tts_backends  # noqa: F401
+
+        from abogen.tts_backend_registry import _registry
+
+        meta = _registry.get_metadata("supertonic")
+        assert meta.id == "supertonic"
+        assert meta.name == "SuperTonic"
+        assert "SuperTonic" in meta.description
+
+    def test_kokoro_factory_callable(self):
+        import abogen.tts_backends  # noqa: F401
+
+        from abogen.tts_backend_registry import _registry
+
+        factory = _registry._factories["kokoro"]
+        assert callable(factory)
+
+    def test_supertonic_factory_callable(self):
+        import abogen.tts_backends  # noqa: F401
+
+        from abogen.tts_backend_registry import _registry
+
+        factory = _registry._factories["supertonic"]
+        assert callable(factory)