add runtime language-model compatibility check with fallback to auto-detect

internal/transcriber/transcriber.go

@@ -3,9 +3,12 @@ package transcriber
 import (
 	"context"
 	"fmt"
+	"log"
 	"strings"
 
+	"github.com/leonardotrapani/hyprvoice/internal/language"
 	"github.com/leonardotrapani/hyprvoice/internal/models/whisper"
+	"github.com/leonardotrapani/hyprvoice/internal/notify"
 	"github.com/leonardotrapani/hyprvoice/internal/provider"
 	"github.com/leonardotrapani/hyprvoice/internal/recording"
 )
@@ -95,6 +98,20 @@ func NewTranscriber(config Config) (Transcriber, error) {
 		return nil, fmt.Errorf("model %s is not a transcription model", config.Model)
 	}
 
+	// runtime language-model compatibility check with fallback
+	// primary validation happens at config time (hard error), this is a safety net
+	if config.Language != "" && !model.SupportsLanguage(config.Language) {
+		langName := language.FromCode(config.Language).Name
+		log.Printf("warning: model %s does not support language %s, falling back to auto-detect", model.ID, langName)
+
+		// send desktop notification to alert user
+		notifier := notify.NewDesktop(nil)
+		notifier.Error(fmt.Sprintf("Model %s does not support %s. Using auto-detect.", model.Name, langName))
+
+		// override language to auto for this session
+		config.Language = ""
+	}
+
 	// streaming models use StreamingTranscriber
 	if model.Streaming {
 		var streamingAdapter StreamingAdapter

internal/transcriber/transcriber_test.go

@@ -994,3 +994,85 @@ func TestStreamingTranscriber_GetFinalTranscriptionSafe(t *testing.T) {
 		t.Errorf("Stop() error = %v", err)
 	}
 }
+
+func TestNewTranscriber_LanguageFallback(t *testing.T) {
+	// test that incompatible language falls back to auto-detect (no error)
+	// distil-whisper-large-v3-en only supports English
+	config := Config{
+		Provider: "groq-transcription",
+		APIKey:   "test-key",
+		Language: "es", // Spanish not supported by English-only model
+		Model:    "distil-whisper-large-v3-en",
+	}
+
+	// should succeed (fallback to auto), not error
+	transcriber, err := NewTranscriber(config)
+	if err != nil {
+		t.Errorf("NewTranscriber() should fall back to auto, got error: %v", err)
+		return
+	}
+
+	if transcriber == nil {
+		t.Errorf("NewTranscriber() returned nil transcriber")
+	}
+}
+
+func TestNewTranscriber_AutoLanguageNoFallback(t *testing.T) {
+	// test that auto language never triggers warning/fallback
+	config := Config{
+		Provider: "groq-transcription",
+		APIKey:   "test-key",
+		Language: "", // auto
+		Model:    "distil-whisper-large-v3-en",
+	}
+
+	transcriber, err := NewTranscriber(config)
+	if err != nil {
+		t.Errorf("NewTranscriber() error = %v", err)
+		return
+	}
+
+	if transcriber == nil {
+		t.Errorf("NewTranscriber() returned nil transcriber")
+	}
+}
+
+func TestNewTranscriber_CompatibleLanguageNoFallback(t *testing.T) {
+	// test that compatible language works normally
+	config := Config{
+		Provider: "groq-transcription",
+		APIKey:   "test-key",
+		Language: "en", // English supported by English-only model
+		Model:    "distil-whisper-large-v3-en",
+	}
+
+	transcriber, err := NewTranscriber(config)
+	if err != nil {
+		t.Errorf("NewTranscriber() error = %v", err)
+		return
+	}
+
+	if transcriber == nil {
+		t.Errorf("NewTranscriber() returned nil transcriber")
+	}
+}
+
+func TestNewTranscriber_MultilingualModelAllLanguages(t *testing.T) {
+	// test that multilingual model accepts any language without fallback
+	config := Config{
+		Provider: "groq-transcription",
+		APIKey:   "test-key",
+		Language: "es",               // Spanish
+		Model:    "whisper-large-v3", // multilingual
+	}
+
+	transcriber, err := NewTranscriber(config)
+	if err != nil {
+		t.Errorf("NewTranscriber() error = %v", err)
+		return
+	}
+
+	if transcriber == nil {
+		t.Errorf("NewTranscriber() returned nil transcriber")
+	}
+}

progress.txt

@@ -459,3 +459,13 @@ Started: Sun Feb  1 12:22:47 AM CET 2026
 - Removed old hardcoded `isValidLanguageCode()` function
 - Updated tests: replaced TestIsValidLanguageCode with TestValidateModelLanguageCompatibility
 - All tests passing, typecheck passes
+
+### Task 42: Add runtime language-model compatibility check with fallback
+- Updated `internal/transcriber/transcriber.go` NewTranscriber()
+- Added runtime check after model lookup: `if config.Language != "" && !model.SupportsLanguage(config.Language)`
+- Logs warning with model ID and language name
+- Sends desktop notification via `notify.NewDesktop(nil).Error(...)` alerting user of fallback
+- Overrides `config.Language = ""` (auto) for this transcription session
+- This is a safety net for manually-edited configs; primary validation is at config-time (hard error)
+- Added 4 tests: LanguageFallback, AutoLanguageNoFallback, CompatibleLanguageNoFallback, MultilingualModelAllLanguages
+- All tests passing with -race flag, typecheck passes

tasks/prd.jsonc

@@ -992,7 +992,7 @@
 				"NewTranscriber with compatible language works normally",
 				"Typecheck passes"
 			],
-			"passes": false
+			"passes": true
 		},
 		{
 			"title": "Add DEEPGRAM_API_KEY env var support",