config: add threads auto-detection and whisper-cpp validation

internal/config/config_test.go

@@ -3,6 +3,7 @@ package config
 import (
 	"os"
 	"path/filepath"
+	"runtime"
 	"testing"
 	"time"
 
@@ -1770,3 +1771,164 @@ func TestConfig_LLMDefaultsPreserveExplicit(t *testing.T) {
 		t.Error("AddPunctuation should remain false (explicit)")
 	}
 }
+
+func TestConfig_Validate_WhisperCpp(t *testing.T) {
+	baseConfig := func() *Config {
+		return &Config{
+			Recording: RecordingConfig{
+				SampleRate:        16000,
+				Channels:          1,
+				Format:            "s16",
+				BufferSize:        8192,
+				ChannelBufferSize: 30,
+				Timeout:           time.Minute,
+			},
+			Injection: InjectionConfig{
+				Backends:         []string{"clipboard"},
+				YdotoolTimeout:   5 * time.Second,
+				WtypeTimeout:     5 * time.Second,
+				ClipboardTimeout: 3 * time.Second,
+			},
+			Notifications: NotificationsConfig{Type: "log"},
+		}
+	}
+
+	t.Run("whisper-cpp valid without API key", func(t *testing.T) {
+		config := baseConfig()
+		config.Transcription = TranscriptionConfig{
+			Provider: "whisper-cpp",
+			Model:    "base.en",
+			// No API key required
+		}
+
+		err := config.Validate()
+		if err != nil {
+			t.Errorf("Validate() should pass for whisper-cpp without API key: %v", err)
+		}
+	})
+
+	t.Run("whisper-cpp valid multilingual model", func(t *testing.T) {
+		config := baseConfig()
+		config.Transcription = TranscriptionConfig{
+			Provider: "whisper-cpp",
+			Model:    "large-v3",
+		}
+
+		err := config.Validate()
+		if err != nil {
+			t.Errorf("Validate() should pass for whisper-cpp with large-v3: %v", err)
+		}
+	})
+
+	t.Run("whisper-cpp invalid model", func(t *testing.T) {
+		config := baseConfig()
+		config.Transcription = TranscriptionConfig{
+			Provider: "whisper-cpp",
+			Model:    "invalid-model",
+		}
+
+		err := config.Validate()
+		if err == nil {
+			t.Error("Validate() should fail for whisper-cpp with invalid model")
+		}
+	})
+
+	t.Run("whisper-cpp invalid language", func(t *testing.T) {
+		config := baseConfig()
+		config.Transcription = TranscriptionConfig{
+			Provider: "whisper-cpp",
+			Model:    "base.en",
+			Language: "invalid-lang",
+		}
+
+		err := config.Validate()
+		if err == nil {
+			t.Error("Validate() should fail for whisper-cpp with invalid language")
+		}
+	})
+
+	t.Run("whisper-cpp valid with language", func(t *testing.T) {
+		config := baseConfig()
+		config.Transcription = TranscriptionConfig{
+			Provider: "whisper-cpp",
+			Model:    "base",
+			Language: "en",
+		}
+
+		err := config.Validate()
+		if err != nil {
+			t.Errorf("Validate() should pass for whisper-cpp with valid language: %v", err)
+		}
+	})
+}
+
+func TestConfig_ThreadsDefault(t *testing.T) {
+	t.Run("threads defaults to NumCPU-1", func(t *testing.T) {
+		config := &Config{
+			Transcription: TranscriptionConfig{
+				Provider: "whisper-cpp",
+				Model:    "base.en",
+				Threads:  0, // Not set
+			},
+		}
+
+		config.applyThreadsDefault()
+
+		expectedThreads := runtime.NumCPU() - 1
+		if expectedThreads < 1 {
+			expectedThreads = 1
+		}
+
+		if config.Transcription.Threads != expectedThreads {
+			t.Errorf("Threads = %d, want %d", config.Transcription.Threads, expectedThreads)
+		}
+	})
+
+	t.Run("explicit threads preserved", func(t *testing.T) {
+		config := &Config{
+			Transcription: TranscriptionConfig{
+				Provider: "whisper-cpp",
+				Model:    "base.en",
+				Threads:  2, // Explicitly set
+			},
+		}
+
+		config.applyThreadsDefault()
+
+		if config.Transcription.Threads != 2 {
+			t.Errorf("Threads = %d, want 2", config.Transcription.Threads)
+		}
+	})
+
+	t.Run("threads minimum is 1", func(t *testing.T) {
+		config := &Config{
+			Transcription: TranscriptionConfig{
+				Provider: "whisper-cpp",
+				Model:    "base.en",
+				Threads:  0,
+			},
+		}
+
+		config.applyThreadsDefault()
+
+		if config.Transcription.Threads < 1 {
+			t.Errorf("Threads = %d, should be at least 1", config.Transcription.Threads)
+		}
+	})
+}
+
+func TestConfig_ToTranscriberConfig_Threads(t *testing.T) {
+	config := &Config{
+		Transcription: TranscriptionConfig{
+			Provider: "whisper-cpp",
+			Model:    "base.en",
+			Threads:  4,
+		},
+	}
+
+	transcriberConfig := config.ToTranscriberConfig()
+
+	if transcriberConfig.Threads != 4 {
+		t.Errorf("Threads = %d, want 4", transcriberConfig.Threads)
+	}
+}

internal/config/load.go

@@ -5,6 +5,7 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"runtime"
 	"time"
 
 	"github.com/BurntSushi/toml"
@@ -76,11 +77,23 @@ func Load() (*Config, error) {
 	}
 
 	config.applyLLMDefaults()
+	config.applyThreadsDefault()
 
 	log.Printf("Config: configuration loaded successfully")
 	return &config, nil
 }
 
+// applyThreadsDefault sets default threads for local transcription if not explicitly set
+func (c *Config) applyThreadsDefault() {
+	if c.Transcription.Threads == 0 {
+		threads := runtime.NumCPU() - 1
+		if threads < 1 {
+			threads = 1
+		}
+		c.Transcription.Threads = threads
+	}
+}
+
 // migrateTranscriptionAPIKey migrates old transcription.api_key to providers map
 func (c *Config) migrateTranscriptionAPIKey(apiKey string) {
 	if c.Providers == nil {

internal/config/validate.go

@@ -93,8 +93,22 @@ func (c *Config) Validate() error {
 			return fmt.Errorf("invalid model for elevenlabs: %s (must be scribe_v1 or scribe_v2)", c.Transcription.Model)
 		}
 
+	case "whisper-cpp":
+		// whisper-cpp is local, no API key required
+		if c.Transcription.Language != "" && !isValidLanguageCode(c.Transcription.Language) {
+			return fmt.Errorf("invalid transcription.language: %s (use empty string for auto-detect or ISO-639-1 codes like 'en', 'es', 'fr')", c.Transcription.Language)
+		}
+
+		validWhisperModels := map[string]bool{
+			"tiny.en": true, "base.en": true, "small.en": true, "medium.en": true,
+			"tiny": true, "base": true, "small": true, "medium": true, "large-v3": true,
+		}
+		if c.Transcription.Model != "" && !validWhisperModels[c.Transcription.Model] {
+			return fmt.Errorf("invalid model for whisper-cpp: %s (must be tiny.en, base.en, small.en, medium.en, tiny, base, small, medium, or large-v3)", c.Transcription.Model)
+		}
+
 	default:
-		return fmt.Errorf("unsupported transcription.provider: %s (must be openai, groq-transcription, groq-translation, mistral-transcription, or elevenlabs)", c.Transcription.Provider)
+		return fmt.Errorf("unsupported transcription.provider: %s (must be openai, groq-transcription, groq-translation, mistral-transcription, elevenlabs, or whisper-cpp)", c.Transcription.Provider)
 	}
 
 	if c.Transcription.Model == "" {

progress.txt

@@ -226,3 +226,12 @@ Started: Sun Feb  1 12:22:47 AM CET 2026
 - Returns error if whisper model ID is unknown
 - Added tests for whisper-cpp factory cases: valid config, no API key required, unknown model error
 - All tests passing, typecheck passes
+
+### Task 23: Update config for local transcription
+- Added `applyThreadsDefault()` to config.Load() - sets Threads to max(1, NumCPU-1) when 0
+- Added whisper-cpp case to config validation (no API key required)
+- Validates whisper model names: tiny.en, base.en, small.en, medium.en, tiny, base, small, medium, large-v3
+- Validates language codes for whisper-cpp same as other providers
+- Note: Threads field, ToTranscriberConfig, and template were already done in Task 16
+- Added comprehensive tests for whisper-cpp validation and threads auto-detection
+- All tests passing, typecheck passes

tasks/prd.jsonc

@@ -550,7 +550,7 @@
 				"Config round-trips correctly with threads field",
 				"Typecheck passes"
 			],
-			"passes": false
+			"passes": true
 		},
 		// ============================================================================
 		// PHASE 5: MODEL CLI COMMANDS