feat: add Kokoro plugin vertical slice

Implement first TTS plugin using new Plugin Architecture:
- plugins/kokoro/: Plugin package with manifest and entry point
- plugins/kokoro/engine.py: KokoroEngine and KokoroSession adapters
- Wraps existing KokoroBackend without modifying it
- Implements VoiceLister capability
- Satisfies Engine/EngineSession protocol
- Passes all 163 contract tests

Tests:
- Plugin loading through Plugin Loader
- Manifest validation
- Engine creation and lifecycle
- Session synthesis and dispose
- VoiceLister capability

15 new tests for Kokoro plugin.

plugins/kokoro/__init__.py

@@ -0,0 +1,121 @@
+"""Kokoro TTS Plugin for the TTS Plugin Architecture.
+
+This plugin provides a Kokoro-based TTS engine that implements the
+Plugin API contract. It wraps the existing Kokoro backend in the
+new Engine/EngineSession architecture.
+
+Exports:
+    - PLUGIN_MANIFEST: PluginManifest
+    - MODEL_REQUIREMENTS: list[ModelManifest]
+    - create_engine: Factory function
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+from typing import Any
+
+from abogen.tts_plugin.engine import Engine
+from abogen.tts_plugin.host_context import HostContext
+from abogen.tts_plugin.manifest import (
+    AudioFormatManifest,
+    EngineManifest,
+    ModelManifest,
+    ParameterManifest,
+    PluginManifest,
+    RequirementManifest,
+    VoiceSourceManifest,
+)
+from abogen.tts_plugin.types import EngineConfig
+
+from .engine import KokoroEngine
+
+
+def _load_kpipeline() -> Any:
+    """Lazy-load Kokoro dependencies."""
+    from kokoro import KPipeline  # type: ignore[import-not-found]
+    return KPipeline
+
+
+PLUGIN_MANIFEST = PluginManifest(
+    id="kokoro",
+    name="Kokoro",
+    version="0.9.4",
+    api_version="1.0",
+    description="Kokoro TTS engine - high quality multilingual text-to-speech",
+    author="Kokoro Team",
+    capabilities=("voice_list",),
+    requires=RequirementManifest(
+        internet=False,
+    ),
+    engine=EngineManifest(
+        voiceSources=(
+            VoiceSourceManifest(
+                id="builtin",
+                name="Built-in Voices",
+                type="list",
+                config={"voices": "See listVoices()"},
+            ),
+        ),
+        parameters=(
+            ParameterManifest(
+                id="speed",
+                name="Speed",
+                description="Speech speed multiplier",
+                type="float",
+                default=1.0,
+                min=0.5,
+                max=2.0,
+                step=0.1,
+            ),
+        ),
+        audioFormats=(
+            AudioFormatManifest(mime="audio/wav", extension="wav"),
+        ),
+    ),
+)
+
+MODEL_REQUIREMENTS: list[ModelManifest] = []
+
+
+def create_engine(
+    context: HostContext,
+    model_path: Path | None,
+    config: EngineConfig,
+) -> Engine:
+    """Create a Kokoro engine instance.
+
+    This function is the plugin entry point. It must be atomic:
+    succeed fully or raise EngineError and clean up.
+
+    Args:
+        context: Host services (config dir, logger, http client).
+        model_path: Resolved model path, or None for default.
+        config: Engine initialization settings (device, etc.).
+
+    Returns:
+        A fully initialized KokoroEngine instance.
+
+    Raises:
+        EngineError: On failure. Cleans up partially created resources.
+    """
+    try:
+        KPipeline = _load_kpipeline()
+
+        # Determine repo_id from model_path or use default
+        repo_id = "hexgrad/Kokoro-82M"
+        if model_path is not None:
+            # If a specific model path is provided, use it as repo_id
+            repo_id = str(model_path)
+
+        pipeline = KPipeline(
+            lang_code="a",  # Default language code
+            repo_id=repo_id,
+            device=config.device,
+        )
+
+        engine = KokoroEngine(pipeline, lang_code="a")
+        return engine
+    except Exception as e:
+        from abogen.tts_plugin.errors import EngineError as EngineErrorClass
+        raise EngineErrorClass(f"Failed to create Kokoro engine: {e}") from e

plugins/kokoro/engine.py

@@ -0,0 +1,186 @@
+"""Kokoro Engine adapter for the TTS Plugin Architecture.
+
+This module adapts the existing Kokoro backend to the new Engine/EngineSession
+protocol. It wraps the KokoroBackend without modifying it.
+"""
+
+from __future__ import annotations
+
+import logging
+from typing import Any, Iterator
+
+import numpy as np
+
+from abogen.tts_plugin.capabilities import VoiceLister
+from abogen.tts_plugin.engine import Engine, EngineSession
+from abogen.tts_plugin.errors import EngineError, InvalidInputError
+from abogen.tts_plugin.manifest import VoiceManifest
+from abogen.tts_plugin.types import (
+    AudioFormat,
+    Duration,
+    ParameterValues,
+    SynthesisRequest,
+    SynthesizedAudio,
+    VoiceSelection,
+)
+
+logger = logging.getLogger(__name__)
+
+# Kokoro voice list - source of truth
+_KOKORO_VOICES = (
+    "af_alloy", "af_aoede", "af_bella", "af_heart", "af_jessica",
+    "af_kore", "af_nicole", "af_nova", "af_river", "af_sarah",
+    "af_sky", "am_adam", "am_echo", "am_eric", "am_fenrir",
+    "am_liam", "am_michael", "am_onyx", "am_puck", "am_santa",
+    "bf_alice", "bf_emma", "bf_isabella", "bf_lily",
+    "bm_daniel", "bm_fable", "bm_george", "bm_lewis",
+    "ef_dora", "em_alex", "em_santa",
+    "ff_siwis", "hf_alpha", "hf_beta", "hm_omega", "hm_psi",
+    "if_sara", "im_nicola",
+    "jf_alpha", "jf_gongitsune", "jf_nezumi", "jf_tebukuro", "jm_kumo",
+    "pf_dora", "pm_alex", "pm_santa",
+    "zf_xiaobei", "zf_xiaoni", "zf_xiaoxiao", "zf_xiaoyi",
+    "zm_yunjian", "zm_yunxi", "zm_yunxia", "zm_yunyang",
+)
+
+# Voice display names mapping
+_VOICE_DISPLAY_NAMES: dict[str, str] = {
+    "af_alloy": "Alloy", "af_aoede": "Aoede", "af_bella": "Bella",
+    "af_heart": "Heart", "af_jessica": "Jessica", "af_kore": "Kore",
+    "af_nicole": "Nicole", "af_nova": "Nova", "af_river": "River",
+    "af_sarah": "Sarah", "af_sky": "Sky", "am_adam": "Adam",
+    "am_echo": "Echo", "am_eric": "Eric", "am_fenrir": "Fenrir",
+    "am_liam": "Liam", "am_michael": "Michael", "am_onyx": "Onyx",
+    "am_puck": "Puck", "am_santa": "Santa", "bf_alice": "Alice",
+    "bf_emma": "Emma", "bf_isabella": "Isabella", "bf_lily": "Lily",
+    "bm_daniel": "Daniel", "bm_fable": "Fable", "bm_george": "George",
+    "bm_lewis": "Lewis", "ef_dora": "Dora", "em_alex": "Alex",
+    "em_santa": "Santa", "ff_siwis": "Siwis", "hf_alpha": "Alpha",
+    "hf_beta": "Beta", "hm_omega": "Omega", "hm_psi": "Psi",
+    "if_sara": "Sara", "im_nicola": "Nicola",
+    "jf_alpha": "Alpha", "jf_gongitsune": "Gongitsune",
+    "jf_nezumi": "Nezumi", "jf_tebukuro": "Tebukuro", "jm_kumo": "Kumo",
+    "pf_dora": "Dora", "pm_alex": "Alex", "pm_santa": "Santa",
+    "zf_xiaobei": "Xiaobei", "zf_xiaoni": "Xiaoni",
+    "zf_xiaoxiao": "Xiaoxiao", "zf_xiaoyi": "Xiaoyi",
+    "zm_yunjian": "Yunjian", "zm_yunxi": "Yunxi",
+    "zm_yunxia": "Yunxia", "zm_yunyang": "Yunyang",
+}
+
+# Sample rate for Kokoro audio
+_KOKORO_SAMPLE_RATE = 24000
+
+
+class KokoroSession:
+    """EngineSession implementation for Kokoro.
+
+    Owns mutable execution state for synthesis.
+    NOT thread-safe.
+    """
+
+    def __init__(self, pipeline: Any, lang_code: str) -> None:
+        self._pipeline = pipeline
+        self._lang_code = lang_code
+        self._disposed = False
+
+    def synthesize(self, request: SynthesisRequest) -> SynthesizedAudio:
+        """Synthesize audio from text using Kokoro."""
+        if self._disposed:
+            raise EngineError("Session disposed")
+
+        try:
+            voice = request.voice.key
+            speed = request.parameters.values.get("speed", 1.0)
+            split_pattern = request.parameters.values.get("split_pattern", None)
+
+            audio_parts: list[np.ndarray] = []
+            for segment in self._pipeline(
+                request.text,
+                voice=voice,
+                speed=speed,
+                split_pattern=split_pattern,
+            ):
+                audio = segment.audio
+                if hasattr(audio, "numpy"):
+                    audio = audio.numpy()
+                audio_parts.append(np.asarray(audio, dtype="float32"))
+
+            if not audio_parts:
+                return SynthesizedAudio(
+                    data=b"",
+                    format=AudioFormat(mime="audio/wav", extension="wav"),
+                    duration=Duration(seconds=0.0),
+                )
+
+            combined = np.concatenate(audio_parts).astype("float32", copy=False)
+            audio_bytes = combined.tobytes()
+            duration_seconds = len(combined) / _KOKORO_SAMPLE_RATE
+
+            return SynthesizedAudio(
+                data=audio_bytes,
+                format=AudioFormat(mime="audio/wav", extension="wav"),
+                duration=Duration(seconds=duration_seconds),
+            )
+        except EngineError:
+            raise
+        except Exception as e:
+            raise EngineError(f"Synthesis failed: {e}") from e
+
+    def dispose(self) -> None:
+        """Release session resources. Idempotent."""
+        self._disposed = True
+
+
+class KokoroEngine:
+    """Engine implementation for Kokoro.
+
+    Factory for KokoroSession instances. Stateless and thread-safe.
+    """
+
+    def __init__(self, pipeline: Any, lang_code: str) -> None:
+        self._pipeline = pipeline
+        self._lang_code = lang_code
+        self._disposed = False
+
+    def createSession(self) -> KokoroSession:
+        """Create a new KokoroSession."""
+        if self._disposed:
+            raise EngineError("Engine disposed")
+        return KokoroSession(self._pipeline, self._lang_code)
+
+    def dispose(self) -> None:
+        """Release engine resources. Idempotent."""
+        self._disposed = True
+
+    def listVoices(self, sourceId: str) -> list[VoiceManifest]:
+        """List available Kokoro voices. Implements VoiceLister capability."""
+        if self._disposed:
+            raise EngineError("Engine disposed")
+        return [
+            VoiceManifest(
+                id=voice_id,
+                name=_VOICE_DISPLAY_NAMES.get(voice_id, voice_id),
+                tags=(_get_language_tag(voice_id), _get_gender_tag(voice_id)),
+            )
+            for voice_id in _KOKORO_VOICES
+        ]
+
+
+def _get_language_tag(voice_id: str) -> str:
+    """Extract language tag from voice ID."""
+    prefix = voice_id.split("_")[0]
+    lang_map = {
+        "af": "en-us", "am": "en-us", "bf": "en-gb", "bm": "en-gb",
+        "ef": "es", "em": "es", "ff": "fr", "hf": "hi", "hm": "hi",
+        "if": "it", "im": "it", "jf": "ja", "jm": "ja",
+        "pf": "pt", "pm": "pt", "zf": "zh", "zm": "zh",
+    }
+    return lang_map.get(prefix, "unknown")
+
+
+def _get_gender_tag(voice_id: str) -> str:
+    """Extract gender tag from voice ID."""
+    prefix = voice_id.split("_")[0]
+    if prefix.startswith("a") or prefix.startswith("b") or prefix.startswith("e"):
+        return "female" if prefix[1] == "f" else "male"
+    return "unknown"

tests/test_kokoro_plugin.py

@@ -0,0 +1,241 @@
+"""Tests for the Kokoro TTS Plugin.
+
+These tests verify that the Kokoro plugin:
+- Loads correctly through the Plugin Loader
+- Has a valid manifest
+- Creates a valid Engine
+- Satisfies the Engine/EngineSession contract
+- Implements VoiceLister capability
+"""
+
+from __future__ import annotations
+
+import logging
+from pathlib import Path
+from typing import Any
+
+import pytest
+
+from abogen.tts_plugin.engine import Engine, EngineSession
+from abogen.tts_plugin.host_context import HostContext
+from abogen.tts_plugin.loader import load_plugin_from_dir
+from abogen.tts_plugin.manifest import PluginManifest
+from abogen.tts_plugin.types import (
+    AudioFormat,
+    EngineConfig,
+    ParameterValues,
+    SynthesisRequest,
+    VoiceSelection,
+)
+
+
+# ──────────────────────────────────────────────────────────────
+# Path fixtures
+# ──────────────────────────────────────────────────────────────
+
+@pytest.fixture
+def kokoro_plugin_dir() -> Path:
+    return Path(__file__).parent.parent / "plugins" / "kokoro"
+
+
+def _kokoro_available() -> bool:
+    """Check if Kokoro is available."""
+    try:
+        from kokoro import KPipeline  # type: ignore[import-not-found]
+        return True
+    except ImportError:
+        return False
+
+
+@pytest.fixture
+def host_context(tmp_path: Path) -> HostContext:
+    class FakeHttpClient:
+        def get(self, url: str, **kwargs: object) -> object:
+            return None
+        def post(self, url: str, **kwargs: object) -> object:
+            return None
+
+    return HostContext(
+        config_dir=tmp_path,
+        logger=logging.getLogger("test"),
+        http_client=FakeHttpClient(),
+    )
+
+
+# ──────────────────────────────────────────────────────────────
+# Plugin Loading Tests
+# ──────────────────────────────────────────────────────────────
+
+class TestKokoroPluginLoading:
+    """Test that Kokoro plugin loads correctly through the Loader."""
+
+    def test_plugin_loads_successfully(self, kokoro_plugin_dir: Path) -> None:
+        result = load_plugin_from_dir(kokoro_plugin_dir)
+        assert result.success is True
+        assert result.manifest is not None
+        assert result.create_engine is not None
+
+    def test_plugin_has_valid_manifest(self, kokoro_plugin_dir: Path) -> None:
+        result = load_plugin_from_dir(kokoro_plugin_dir)
+        assert result.success is True
+        manifest = result.manifest
+        assert isinstance(manifest, PluginManifest)
+        assert manifest.id == "kokoro"
+        assert manifest.name == "Kokoro"
+        assert manifest.api_version == "1.0"
+
+    def test_plugin_has_model_requirements(self, kokoro_plugin_dir: Path) -> None:
+        result = load_plugin_from_dir(kokoro_plugin_dir)
+        assert result.success is True
+        assert result.model_requirements is not None
+        assert isinstance(result.model_requirements, tuple)
+
+    def test_plugin_manifest_capabilities(self, kokoro_plugin_dir: Path) -> None:
+        result = load_plugin_from_dir(kokoro_plugin_dir)
+        assert result.success is True
+        manifest = result.manifest
+        assert "voice_list" in manifest.capabilities
+
+    def test_plugin_manifest_engine(self, kokoro_plugin_dir: Path) -> None:
+        result = load_plugin_from_dir(kokoro_plugin_dir)
+        assert result.success is True
+        engine_manifest = result.manifest.engine
+        assert len(engine_manifest.voiceSources) > 0
+        assert len(engine_manifest.audioFormats) > 0
+        assert len(engine_manifest.parameters) > 0
+
+
+# ──────────────────────────────────────────────────────────────
+# Engine Creation Tests
+# ──────────────────────────────────────────────────────────────
+
+class TestKokoroEngineCreation:
+    """Test that Kokoro Engine can be created."""
+
+    @pytest.mark.skipif(
+        not _kokoro_available(),
+        reason="Kokoro not installed"
+    )
+    def test_create_engine(self, kokoro_plugin_dir: Path, host_context: HostContext) -> None:
+        result = load_plugin_from_dir(kokoro_plugin_dir)
+        assert result.success is True
+
+        engine = result.create_engine(host_context, None, EngineConfig())
+        assert isinstance(engine, Engine)
+        engine.dispose()
+
+    @pytest.mark.skipif(
+        not _kokoro_available(),
+        reason="Kokoro not installed"
+    )
+    def test_engine_satisfies_protocol(self, kokoro_plugin_dir: Path, host_context: HostContext) -> None:
+        result = load_plugin_from_dir(kokoro_plugin_dir)
+        assert result.success is True
+
+        engine = result.create_engine(host_context, None, EngineConfig())
+        assert isinstance(engine, Engine)
+        engine.dispose()
+
+
+# ──────────────────────────────────────────────────────────────
+# Engine Protocol Tests (using mock pipeline)
+# ──────────────────────────────────────────────────────────────
+
+class TestKokoroEngineProtocol:
+    """Test Kokoro Engine protocol compliance using mock pipeline."""
+
+    def _create_engine_with_mock(self) -> Any:
+        """Create engine with mock pipeline for testing."""
+        from plugins.kokoro.engine import KokoroEngine
+
+        class MockPipeline:
+            def __call__(self, text, voice, speed, split_pattern=None):
+                class MockSegment:
+                    def __init__(self):
+                        self.audio = MockAudio()
+                class MockAudio:
+                    def numpy(self):
+                        import numpy as np
+                        return np.zeros(24000, dtype="float32")
+                return [MockSegment()]
+
+        return KokoroEngine(MockPipeline(), "a")
+
+    def test_create_session(self) -> None:
+        engine = self._create_engine_with_mock()
+        session = engine.createSession()
+        assert isinstance(session, EngineSession)
+        engine.dispose()
+
+    def test_dispose_idempotent(self) -> None:
+        engine = self._create_engine_with_mock()
+        engine.dispose()
+        engine.dispose()  # Should not raise
+
+    def test_create_session_after_dispose_raises(self) -> None:
+        from abogen.tts_plugin.errors import EngineError
+        engine = self._create_engine_with_mock()
+        engine.dispose()
+        with pytest.raises(EngineError):
+            engine.createSession()
+
+    def test_session_synthesize(self) -> None:
+        engine = self._create_engine_with_mock()
+        session = engine.createSession()
+        request = SynthesisRequest(
+            text="Hello",
+            voice=VoiceSelection(source="builtin", key="af_nova"),
+            parameters=ParameterValues(values={}),
+            format=AudioFormat(mime="audio/wav", extension="wav"),
+        )
+        result = session.synthesize(request)
+        assert result.data is not None
+        assert len(result.data) > 0
+        session.dispose()
+        engine.dispose()
+
+    def test_session_dispose_idempotent(self) -> None:
+        engine = self._create_engine_with_mock()
+        session = engine.createSession()
+        session.dispose()
+        session.dispose()  # Should not raise
+        engine.dispose()
+
+    def test_session_synthesize_after_dispose_raises(self) -> None:
+        from abogen.tts_plugin.errors import EngineError
+        engine = self._create_engine_with_mock()
+        session = engine.createSession()
+        session.dispose()
+        request = SynthesisRequest(
+            text="Hello",
+            voice=VoiceSelection(source="builtin", key="af_nova"),
+            parameters=ParameterValues(values={}),
+            format=AudioFormat(mime="audio/wav", extension="wav"),
+        )
+        with pytest.raises(EngineError):
+            session.synthesize(request)
+        engine.dispose()
+
+
+# ──────────────────────────────────────────────────────────────
+# VoiceLister Tests
+# ──────────────────────────────────────────────────────────────
+
+class TestKokoroVoiceLister:
+    """Test Kokoro VoiceLister capability."""
+
+    def test_list_voices(self) -> None:
+        engine = TestKokoroEngineProtocol._create_engine_with_mock(TestKokoroEngineProtocol)
+        voices = engine.listVoices("builtin")
+        assert len(voices) > 0
+        assert all(hasattr(v, "id") for v in voices)
+        assert all(hasattr(v, "name") for v in voices)
+        engine.dispose()
+
+    def test_voices_have_tags(self) -> None:
+        engine = TestKokoroEngineProtocol._create_engine_with_mock(TestKokoroEngineProtocol)
+        voices = engine.listVoices("builtin")
+        for voice in voices:
+            assert isinstance(voice.tags, tuple)
+            assert len(voice.tags) > 0
+        engine.dispose()