diff --git a/abogen/webui/conversion_adapter.py b/abogen/webui/conversion_adapter.py
new file mode 100644
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+++ b/abogen/webui/conversion_adapter.py
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+"""WebUI adapter: Job -> ConversionRequest.
+
+Converts a WebUI Job into a ConversionRequest that the application layer can process.
+This adapter is the bridge between the WebUI layer and the application/domain layer.
+
+The adapter is responsible for:
+- Mapping Job fields to ConversionRequest fields
+- Handling UI-specific state (logs, progress, cancellation)
+- Providing PipelineProvider and VoiceResolver implementations
+
+All conversions happen through this adapter — the application layer
+never accesses Job directly.
+"""
+
+from __future__ import annotations
+
+import threading
+import time
+from typing import Any, Callable, Dict, List, Optional
+
+from abogen.application.conversion_request import ConversionRequest
+from abogen.application.conversion_ports import ResolvedVoice
+
+
+def build_conversion_request_from_job(job: Any) -> ConversionRequest:
+    """Convert a WebUI Job into a ConversionRequest.
+
+    This is the primary function that maps Job fields to ConversionRequest.
+    All fields are copied — the request is independent of the Job.
+
+    Args:
+        job: WebUI Job instance
+
+    Returns:
+        ConversionRequest with all Job data mapped
+    """
+    return ConversionRequest(
+        # Source
+        source_path=job.stored_path,
+        original_filename=job.original_filename,
+        # TTS Settings
+        language=job.language or "a",
+        tts_provider=job.tts_provider or "kokoro",
+        voice=job.voice or "M1",
+        voice_profile=job.voice_profile,
+        speed=job.speed or 1.0,
+        use_gpu=job.use_gpu,
+        supertonic_total_steps=job.supertonic_total_steps or 5,
+        # Output Format
+        output_format=job.output_format or "wav",
+        subtitle_mode=job.subtitle_mode or "Disabled",
+        subtitle_format=job.subtitle_format or "srt",
+        max_subtitle_words=job.max_subtitle_words or 50,
+        # Save Options
+        save_mode=job.save_mode or "save_next_to_input",
+        output_folder=job.output_folder,
+        save_chapters_separately=job.save_chapters_separately,
+        merge_chapters_at_end=job.merge_chapters_at_end,
+        separate_chapters_format=job.separate_chapters_format or "wav",
+        save_as_project=job.save_as_project,
+        # Timing
+        silence_between_chapters=job.silence_between_chapters or 2.0,
+        chapter_intro_delay=job.chapter_intro_delay or 0.0,
+        # Content Processing
+        replace_single_newlines=job.replace_single_newlines,
+        read_title_intro=job.read_title_intro,
+        read_closing_outro=job.read_closing_outro,
+        auto_prefix_chapter_titles=job.auto_prefix_chapter_titles,
+        normalize_chapter_opening_caps=job.normalize_chapter_opening_caps,
+        # Pronunciation / Normalization
+        pronunciation_overrides=job.pronunciation_overrides or [],
+        manual_overrides=job.manual_overrides or [],
+        heteronym_overrides=job.heteronym_overrides or [],
+        normalization_overrides=job.normalization_overrides or {},
+        # Chapter/Chunk Configuration
+        chapter_overrides=job.chapters or [],
+        chunks=job.chunks or [],
+        chunk_level=job.chunk_level or "paragraph",
+        speaker_mode=job.speaker_mode or "single",
+        speakers=job.speakers or {},
+        # Metadata
+        metadata_tags=job.metadata_tags or {},
+        # Artifacts
+        cover_image_path=job.cover_image_path,
+        cover_image_mime=job.cover_image_mime,
+        generate_epub3=job.generate_epub3,
+    )
+
+
+class WebJobEvents:
+    """WebUI implementation of ConversionEvents protocol.
+
+    Wraps a Job to provide logging, progress, and cancellation.
+    """
+
+    def __init__(self, job: Any):
+        self._job = job
+
+    def log(self, message: str, level: str = "info") -> None:
+        """Log a message to the Job."""
+        self._job.add_log(message, level=level)
+
+    def progress(self, pct: int, etr: str) -> None:
+        """Update progress on the Job."""
+        self._job.progress = pct / 100.0
+        self._job.etr_str = etr
+
+    def check_cancelled(self) -> None:
+        """Check if the Job was cancelled.
+
+        Raises:
+            ConversionCancelled: If cancellation was requested
+        """
+        if self._job.cancel_requested:
+            raise ConversionCancelled("Job cancelled by user")
+
+
+class ConversionCancelled(Exception):
+    """Raised when conversion is cancelled."""
+    pass
+
+
+class WebPipelineProvider:
+    """WebUI implementation of PipelineProvider protocol.
+
+    Wraps PipelinePool to provide TTS backends.
+    """
+
+    def __init__(self, pipeline_pool: Any):
+        self._pool = pipeline_pool
+
+    def get(self, provider: str, language: str, use_gpu: bool) -> Any:
+        """Get a TTS backend instance."""
+        return self._pool.get(provider, language, use_gpu)
+
+    def dispose_all(self) -> None:
+        """Dispose all backend resources."""
+        self._pool.dispose_all()
+
+
+class WebVoiceResolver:
+    """WebUI implementation of VoiceResolver protocol.
+
+    Wraps the voice resolution logic from conversion_runner.py.
+    """
+
+    def __init__(
+        self,
+        resolve_fn: Callable[[str], tuple[str, str, Any, Optional[float], Optional[int]]],
+    ):
+        """Initialize with a voice resolution function.
+
+        Args:
+            resolve_fn: Function that takes a voice_spec and returns
+                (provider, resolved_spec, voice_choice, speed, steps)
+        """
+        self._resolve_fn = resolve_fn
+
+    def resolve(self, voice_spec: str) -> ResolvedVoice:
+        """Resolve a voice spec into a loaded voice."""
+        provider, resolved_spec, voice, speed, steps = self._resolve_fn(voice_spec)
+        return ResolvedVoice(
+            provider=provider,
+            resolved_spec=resolved_spec,
+            voice=voice,
+            speed=speed or 1.0,
+            supertonic_steps=steps or 5,
+        )