From 51f0be9cc8281e98e6baab1e2dcb69d7f5f00650 Mon Sep 17 00:00:00 2001
From: waleed <walif6@gmail.com>
Date: Wed, 10 Jun 2026 08:53:45 -0700
Subject: [PATCH 1/2] improvement(chat-voice): modernize ElevenLabs TTS to
 Flash v2.5

- Switch default TTS model from eleven_turbo_v2_5 to eleven_flash_v2_5 (ElevenLabs recommends Flash over Turbo in all cases; ~75ms latency)
- Drop deprecated optimize_streaming_latency knob plus legacy use_pvc_as_ivc / enable_ssml_parsing flags
- Move output_format to the query string and raise it from mp3_22050_32 to mp3_44100_128 for higher audio quality
- Switch apply_text_normalization from off to auto for correct number/date pronunciation
---
 apps/sim/app/api/proxy/tts/stream/route.ts     | 9 +++------
 apps/sim/app/chat/hooks/use-audio-streaming.ts | 2 +-
 apps/sim/lib/api/contracts/media/tts-stream.ts | 2 +-
 3 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/apps/sim/app/api/proxy/tts/stream/route.ts b/apps/sim/app/api/proxy/tts/stream/route.ts
index d8ea97d39c..39d561522a 100644
--- a/apps/sim/app/api/proxy/tts/stream/route.ts
+++ b/apps/sim/app/api/proxy/tts/stream/route.ts
@@ -92,7 +92,8 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
       return new Response('ElevenLabs service not configured', { status: 503 })
     }
 
-    const endpoint = `https://api.elevenlabs.io/v1/text-to-speech/${voiceId}/stream`
+    const query = new URLSearchParams({ output_format: 'mp3_44100_128' })
+    const endpoint = `https://api.elevenlabs.io/v1/text-to-speech/${voiceId}/stream?${query.toString()}`
 
     const response = await fetch(endpoint, {
       method: 'POST',
@@ -104,17 +105,13 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
       body: JSON.stringify({
         text,
         model_id: modelId,
-        optimize_streaming_latency: 4,
-        output_format: 'mp3_22050_32', // Fastest format
         voice_settings: {
           stability: 0.5,
           similarity_boost: 0.8,
           style: 0.0,
           use_speaker_boost: false,
         },
-        enable_ssml_parsing: false,
-        apply_text_normalization: 'off',
-        use_pvc_as_ivc: false,
+        apply_text_normalization: 'auto',
       }),
     })
 
diff --git a/apps/sim/app/chat/hooks/use-audio-streaming.ts b/apps/sim/app/chat/hooks/use-audio-streaming.ts
index 6ba5b5d9aa..51db697440 100644
--- a/apps/sim/app/chat/hooks/use-audio-streaming.ts
+++ b/apps/sim/app/chat/hooks/use-audio-streaming.ts
@@ -79,7 +79,7 @@ export function useAudioStreaming(sharedAudioContextRef?: RefObject<AudioContext
     const { text, options } = item
     const {
       voiceId,
-      modelId = 'eleven_turbo_v2_5',
+      modelId = 'eleven_flash_v2_5',
       chatId,
       onAudioStart,
       onAudioEnd,
diff --git a/apps/sim/lib/api/contracts/media/tts-stream.ts b/apps/sim/lib/api/contracts/media/tts-stream.ts
index 4b7433c82e..d692d933f9 100644
--- a/apps/sim/lib/api/contracts/media/tts-stream.ts
+++ b/apps/sim/lib/api/contracts/media/tts-stream.ts
@@ -5,7 +5,7 @@ export const ttsStreamBodySchema = z
   .object({
     text: z.string().min(1),
     voiceId: z.string().min(1),
-    modelId: z.string().optional().default('eleven_turbo_v2_5'),
+    modelId: z.string().optional().default('eleven_flash_v2_5'),
     chatId: z.string().min(1),
   })
   .passthrough()

From 8d23fec072846b6cc7848a071fec1470a7671c0a Mon Sep 17 00:00:00 2001
From: waleed <walif6@gmail.com>
Date: Wed, 10 Jun 2026 09:00:18 -0700
Subject: [PATCH 2/2] improvement(chat-voice): default to Jessica voice (Flash
 v2.5-optimized)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Replace the legacy Sarah default (EXAVITQu4vr4xnSDxMaL), which has no high-quality
eleven_flash_v2_5 base, with Jessica (cgSgspJ2msm6clMCkdW9) — a current premade
conversational voice verified against the live account and optimized for Flash v2.5.
---
 apps/sim/app/chat/[identifier]/chat.tsx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/apps/sim/app/chat/[identifier]/chat.tsx b/apps/sim/app/chat/[identifier]/chat.tsx
index f5678291c8..891727d578 100644
--- a/apps/sim/app/chat/[identifier]/chat.tsx
+++ b/apps/sim/app/chat/[identifier]/chat.tsx
@@ -44,7 +44,7 @@ interface ChatRequestPayload {
 }
 
 const DEFAULT_VOICE_SETTINGS = {
-  voiceId: 'EXAVITQu4vr4xnSDxMaL', // Default ElevenLabs voice (Bella)
+  voiceId: 'cgSgspJ2msm6clMCkdW9', // Default ElevenLabs voice (Jessica) — Flash v2.5-optimized
 }
 
 /**