diff --git a/internal/language/language.go b/internal/language/language.go
index a821a4f..eeaed99 100644
--- a/internal/language/language.go
+++ b/internal/language/language.go
@@ -118,3 +118,49 @@ func IsValidCode(code string) bool {
 	_, ok := codeIndex[code]
 	return ok
 }
+
+// ToProviderFormat converts a canonical language code to the format expected by a specific provider.
+// Each provider may have different expectations:
+//   - whisper-cpp: uses standard codes like 'en', 'auto' for auto-detect
+//   - openai: uses standard codes like 'en', empty string for auto-detect
+//   - groq: same as openai (OpenAI-compatible)
+//   - mistral: same as openai (OpenAI-compatible)
+//   - deepgram: uses locale codes like 'en-US', 'es' for Spanish
+//   - elevenlabs: uses standard codes or full names depending on API version
+func ToProviderFormat(code string, providerName string) string {
+	// handle auto-detect (empty code)
+	if code == "" {
+		switch providerName {
+		case "whisper-cpp":
+			return "auto"
+		default:
+			// most providers use empty string or omit the parameter
+			return ""
+		}
+	}
+
+	switch providerName {
+	case "deepgram":
+		// deepgram prefers locale codes for some languages
+		return toDeepgramFormat(code)
+	default:
+		// whisper-cpp, openai, groq, mistral, elevenlabs use standard codes
+		return code
+	}
+}
+
+// toDeepgramFormat maps standard codes to Deepgram's preferred format
+func toDeepgramFormat(code string) string {
+	// deepgram uses locale codes for English variants, standard for most others
+	deepgramMappings := map[string]string{
+		"en": "en-US",
+		"es": "es",    // Spanish uses base code
+		"pt": "pt-BR", // Portuguese defaults to Brazilian
+		"zh": "zh-CN", // Chinese defaults to Simplified
+	}
+
+	if mapped, ok := deepgramMappings[code]; ok {
+		return mapped
+	}
+	return code
+}
diff --git a/internal/language/language_test.go b/internal/language/language_test.go
index 7eda70e..2f21a4b 100644
--- a/internal/language/language_test.go
+++ b/internal/language/language_test.go
@@ -117,3 +117,49 @@ func TestAuto(t *testing.T) {
 		t.Errorf("Auto.Name = %q, want 'Auto-detect'", Auto.Name)
 	}
 }
+
+func TestToProviderFormat(t *testing.T) {
+	tests := []struct {
+		code     string
+		provider string
+		want     string
+	}{
+		// whisper-cpp
+		{"en", "whisper-cpp", "en"},
+		{"es", "whisper-cpp", "es"},
+		{"", "whisper-cpp", "auto"},
+
+		// openai
+		{"en", "openai", "en"},
+		{"", "openai", ""},
+
+		// groq (openai-compatible)
+		{"en", "groq", "en"},
+		{"", "groq", ""},
+
+		// mistral (openai-compatible)
+		{"en", "mistral", "en"},
+		{"", "mistral", ""},
+
+		// deepgram (uses locale codes)
+		{"en", "deepgram", "en-US"},
+		{"es", "deepgram", "es"},
+		{"pt", "deepgram", "pt-BR"},
+		{"zh", "deepgram", "zh-CN"},
+		{"fr", "deepgram", "fr"}, // no special mapping, passthrough
+		{"", "deepgram", ""},
+
+		// elevenlabs
+		{"en", "elevenlabs", "en"},
+		{"", "elevenlabs", ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.code+"_"+tt.provider, func(t *testing.T) {
+			got := ToProviderFormat(tt.code, tt.provider)
+			if got != tt.want {
+				t.Errorf("ToProviderFormat(%q, %q) = %q, want %q", tt.code, tt.provider, got, tt.want)
+			}
+		})
+	}
+}
diff --git a/progress.txt b/progress.txt
index ddd2bd0..f54700e 100644
--- a/progress.txt
+++ b/progress.txt
@@ -9,3 +9,10 @@ Started: Sun Feb  1 12:22:47 AM CET 2026
 - Implemented FromCode, List, Codes, AllLanguageCodes, IsValidCode
 - Full 57 language list from OpenAI Whisper
 - All tests passing, typecheck passes
+
+### Task 2: Add language list and provider-specific mappings
+- Added `ToProviderFormat(code string, providerName string) string` function
+- Handles auto-detect: whisper-cpp uses "auto", others use ""
+- Deepgram locale mappings: en->en-US, pt->pt-BR, zh->zh-CN
+- Added comprehensive test coverage for all provider formats
+- All tests passing, typecheck passes
diff --git a/tasks/prd.jsonc b/tasks/prd.jsonc
index 81e600a..79a19f7 100644
--- a/tasks/prd.jsonc
+++ b/tasks/prd.jsonc
@@ -29,11 +29,11 @@
 			"passes": true
 		},
 		{
-			"title": "Add language list and provider-specific mappings",
+"title": "Add language list and provider-specific mappings",
 			"steps": [
 				"Update internal/language/language.go with full language list",
 				"Master language list derived from OpenAI Whisper's 57 supported languages (source: https://platform.openai.com/docs/guides/speech-to-text#supported-languages)",
-				"Add all 57 languages: af/Afrikaans, ar/Arabic/العربية, hy/Armenian/Հայdelays, az/Azerbaijani/Azərbaycan, be/Belarusian/Беларуская, bs/Bosnian/Bosanski, bg/Bulgarian/Български, ca/Catalan/Català, zh/Chinese/中文, hr/Croatian/Hrvatski, cs/Czech/Čeština, da/Danish/Dansk, nl/Dutch/Nederlands, en/English, et/Estonian/Eesti, fi/Finnish/Suomi, fr/French/Français, gl/Galician/Galego, de/German/Deutsch, el/Greek/Ελληνικά, he/Hebrew/עברית, hi/Hindi/हिन्दी, hu/Hungarian/Magyar, is/Icelandic/Íslenska, id/Indonesian/Bahasa Indonesia, it/Italian/Italiano, ja/Japanese/日本語, kn/Kannada/ಕನ್ನಡ, kk/Kazakh/Қазақ, ko/Korean/한국어, lv/Latvian/Latviešu, lt/Lithuanian/Lietuvių, mk/Macedonian/Македонски, ms/Malay/Bahasa Melayu, mr/Marathi/मराठी, mi/Maori/Māori, ne/Nepali/नेपाली, no/Norwegian/Norsk, fa/Persian/فارسی, pl/Polish/Polski, pt/Portuguese/Português, ro/Romanian/Română, ru/Russian/Русский, sr/Serbian/Српски, sk/Slovak/Slovenčina, sl/Slovenian/Slovenščina, es/Spanish/Español, sw/Swahili/Kiswahili, sv/Swedish/Svenska, tl/Tagalog, ta/Tamil/தமிழ், th/Thai/ไทย, tr/Turkish/Türkçe, uk/Ukrainian/Українська, ur/Urdu/اردو, vi/Vietnamese/Tiếng Việt, cy/Welsh/Cymraeg",
+				"Add all 57 languages: af/Afrikaans, ar/Arabic/العربية, hy/Armenian/Հdelays, az/Azerbaijani/Azərbaycan, be/Belarusian/Беларуская, bs/Bosnian/Bosanski, bg/Bulgarian/Български, ca/Catalan/Català, zh/Chinese/中文, hr/Croatian/Hrvatski, cs/Czech/Čeština, da/Danish/Dansk, nl/Dutch/Nederlands, en/English, et/Estonian/Eesti, fi/Finnish/Suomi, fr/French/Français, gl/Galician/Galego, de/German/Deutsch, el/Greek/Ελληνικά, he/Hebrew/עברית, hi/Hindi/हिन्दी, hu/Hungarian/Magyar, is/Icelandic/Íslenska, id/Indonesian/Bahasa Indonesia, it/Italian/Italiano, ja/Japanese/日本語, kn/Kannada/ಕನ್ನಡ, kk/Kazakh/Қазақ, ko/Korean/한국어, lv/Latvian/Latviešu, lt/Lithuanian/Lietuvių, mk/Macedonian/Македонски, ms/Malay/Bahasa Melayu, mr/Marathi/मराठी, mi/Maori/Māori, ne/Nepali/नेपाली, no/Norwegian/Norsk, fa/Persian/فارسی, pl/Polish/Polski, pt/Portuguese/Português, ro/Romanian/Română, ru/Russian/Русский, sr/Serbian/Српски, sk/Slovak/Slovenčina, sl/Slovenian/Slovenščina, es/Spanish/Español, sw/Swahili/Kiswahili, sv/Swedish/Svenska, tl/Tagalog, ta/Tamil/தமிழ், th/Thai/ไทย, tr/Turkish/Türkçe, uk/Ukrainian/Українська, ur/Urdu/اردو, vi/Vietnamese/Tiếng Việt, cy/Welsh/Cymraeg",
 				"Implement ToProviderFormat(code string, providerName string) string - maps our code to provider-specific format",
 				"Provider mappings: whisper-cpp uses 'en'/'auto', some APIs use 'english', Deepgram uses 'en-US'",
 				"Each provider can handle Auto ('') differently via ToProviderFormat"
@@ -47,7 +47,7 @@
 				"ToProviderFormat('', 'openai') returns '' or appropriate auto value",
 				"Typecheck passes"
 			],
-			"passes": false
+			"passes": true
 		},
 		{
 			"title": "Create Model type with full metadata",