fix: language enum coercion, preview logging, file picker

- form.py: convert language string to Language enum at all entry points
- conversion_request.py: add _coerce_enums() for defense-in-depth
- synthesize.py: fix NameError (lang -> language) in preview pipeline
- voice.py: render LANGUAGE_DESCRIPTIONS keys as .value strings for Jinja
- dashboard.js: open file picker on dropzone click
- api.py: add logging to preview endpoint for debugging

abogen/application/conversion_request.py

@@ -105,6 +105,7 @@ class ConversionRequest:
         _apply_none_defaults(self)
         if not self.tts_provider:
             self.tts_provider = "kokoro"
+        _coerce_enums(self)
         _clamp_numerics(self)
 
 
@@ -119,6 +120,25 @@ def _apply_none_defaults(obj: ConversionRequest) -> None:
             setattr(obj, f.name, f.default_factory())
 
 
+# Enum fields that accept string coercion: attr -> (enum_class, fallback)
+_ENUM_COERCIONS: dict[str, tuple[type, Any]] = {
+    "language": (Language, Language.EN_US),
+    "output_format": (OutputFormat, OutputFormat.WAV),
+}
+
+
+def _coerce_enums(obj: ConversionRequest) -> None:
+    """Coerce string values to their expected enum types."""
+    for attr, (enum_cls, fallback) in _ENUM_COERCIONS.items():
+        val = getattr(obj, attr)
+        if isinstance(val, enum_cls):
+            continue
+        try:
+            setattr(obj, attr, enum_cls.from_str(str(val)))
+        except (ValueError, AttributeError):
+            setattr(obj, attr, fallback)
+
+
 def _clamp_numerics(obj: ConversionRequest) -> None:
     """Clamp numeric fields to valid ranges."""
     for attr, (min_v, max_v) in _NUMERIC_CONSTRAINTS.items():

abogen/webui/routes/api.py

@@ -184,6 +184,11 @@ def api_voice_profiles_preview() -> ResponseReturnValue:
     voice_spec = ""
     resolved_provider = provider or "kokoro"
 
+    current_app.logger.info(
+        "[preview] provider=%s language=%s speed=%.2f profile=%s formula=%s",
+        resolved_provider, language, speed, profile_name or "-", formula or "-",
+    )
+
     profiles = load_profiles()
     if resolved_provider == "supertonic" and not profile_name:
         voice_spec = str(payload.get("voice") or payload.get("supertonic_voice") or "M1").strip() or "M1"
@@ -214,7 +219,13 @@ def api_voice_profiles_preview() -> ResponseReturnValue:
         voice_spec = formula_from_profile(normalized_entry) or ""
         resolved_provider = "kokoro"
 
+    current_app.logger.info(
+        "[preview] resolved: provider=%s voice_spec=%s",
+        resolved_provider, voice_spec[:80] if voice_spec else "-",
+    )
+
     if not voice_spec:
+        current_app.logger.warning("[preview] empty voice_spec, returning 400")
         return jsonify({"error": "Unable to resolve preview voice"}), 400
 
     try:
@@ -229,6 +240,7 @@ def api_voice_profiles_preview() -> ResponseReturnValue:
             max_seconds=max_seconds,
         )
     except Exception as exc:
+        current_app.logger.exception("[preview] synthesis failed: %s", exc)
         return jsonify({"error": str(exc)}), 500
 
 @api_bp.post("/speaker-preview")

abogen/webui/routes/utils/form.py

@@ -4,6 +4,7 @@ from typing import Any, Dict, Iterable, List, Mapping, Optional, Tuple, cast
 from flask import request, render_template, jsonify
 from flask.typing import ResponseReturnValue
 
+from abogen.domain.enums import Language
 from abogen.domain.chapter_classification import (
     supplement_score,
     should_preselect_chapter,
@@ -346,7 +347,10 @@ def apply_book_step_form(
     language_fallback = pending.language or settings.get("language", "en")
     raw_language = (form.get("language") or language_fallback or "en").strip()
     if raw_language:
-        pending.language = raw_language
+        try:
+            pending.language = Language.from_str(raw_language)
+        except (ValueError, AttributeError):
+            pending.language = Language.EN_US
 
     subtitle_mode = (form.get("subtitle_mode") or pending.subtitle_mode or "Disabled").strip()
     if subtitle_mode:
@@ -513,7 +517,10 @@ def apply_book_step_form(
     )
 
     if resolved_language:
-        pending.language = resolved_language
+        try:
+            pending.language = Language.from_str(str(resolved_language))
+        except (ValueError, AttributeError):
+            pass  # keep existing language
 
     if profile_selection == "__formula" and custom_formula_raw:
         pending.voice = custom_formula_raw
@@ -666,7 +673,11 @@ def build_pending_job_from_extraction(
 
     ensure_at_least_one_chapter_enabled(chapters_payload)
 
-    language = str(form.get("language") or "a").strip() or "a"
+    raw_language = str(form.get("language") or "a").strip() or "a"
+    try:
+        language = Language.from_str(raw_language)
+    except (ValueError, AttributeError):
+        language = Language.EN_US
     profiles_map = dict(profiles) if isinstance(profiles, Mapping) else dict(profiles or {})
     default_voice_setting = settings.get("default_voice") or ""
     resolved_default_voice, inferred_profile, inferred_language = resolve_voice_setting(

abogen/webui/routes/utils/synthesize.py

@@ -58,7 +58,7 @@ def get_preview_pipeline(language: Language, device: str) -> Any:
             return pipeline
         from abogen.tts_plugin.utils import create_pipeline
 
-        pipeline = create_pipeline("kokoro", language=lang, device=device)
+        pipeline = create_pipeline("kokoro", language=language, device=device)
         _preview_pipelines[key] = pipeline
         return pipeline
 

abogen/webui/routes/utils/voice.py

@@ -578,7 +578,7 @@ def template_options() -> Dict[str, Any]:
         )
     voice_catalog = build_voice_catalog()
     return {
-        "languages": LANGUAGE_DESCRIPTIONS,
+        "languages": {lang.value: label for lang, label in LANGUAGE_DESCRIPTIONS.items()},
         "voices": get_voices("kokoro"),
         "subtitle_formats": SUBTITLE_FORMATS,
         "supported_langs_for_subs": SUPPORTED_LANGUAGES_FOR_SUBTITLE_GENERATION,

abogen/webui/static/dashboard.js

@@ -452,6 +452,9 @@ const initDashboard = () => {
         return;
       }
       openUploadModal(dropzone);
+      if (sourceFileInput) {
+        sourceFileInput.click();
+      }
     });
 
     dropzone.addEventListener("keydown", (event) => {