stephenvapiai · Oct 22, 2026 · Oct 22, 2026 · Oct 22, 2026
diff --git a/fern/changelog/2026-10-19.mdx b/fern/changelog/2026-10-19.mdx
@@ -0,0 +1,18 @@
+# What's New: Week of October 19, 2026
+
+## New Models and Voices
+
+1. **Claude Haiku 5.5**: The [`claude-haiku-5-5`](/providers/model/anthropic) model is now available for assistants and squads, with a reasoning-effort control, and it can be selected as an eval judge model.
+2. **Gemini 3.8 Flash**: The [`gemini-3.8-flash`](/providers/model/gemini) model is now available on the Google provider.
+3. **Cartesia Sonic-3.6**: The Cartesia [`sonic-3.6`](/providers/voice/cartesia) voice is now available in the dashboard voice settings.
+
+## Features
+
+1. **Priority processing (OpenAI Fast mode)**: A new [Priority processing](/providers/model/openai#service-tier) switch in the assistant editor runs supported OpenAI models in OpenAI's Fast service tier, billed at OpenAI's Fast rates, and the served service tier now appears in `call.costs`.
+2. **Monitor failed server messages**: You can now add a "Server message failed" monitor that alerts you when a server message (webhook) fails to deliver, filterable by message type, URL, status code, and failure reason.
+
+## Fixes and Improvements
+
+1. **Twilio SIP warm-transfer fix**: On Twilio SIP calls, the warm-transfer URL is now set on the `<Sip>` verb instead of `<Dial>`.
+2. **GPT-Live silence fix**: GPT-Live now drops queued silence so voice simulations no longer overflow.
+3. **Call recording reliability**: Recording update and token creation on the Daily media provider are now retried, so video recordings are more reliable.
diff --git a/fern/providers/model/anthropic.mdx b/fern/providers/model/anthropic.mdx
@@ -35,6 +35,7 @@ For additional API configuration options, review the [`AnthropicModel` fields](/
 | Claude Sonnet 5 | `claude-sonnet-5` |
 | Claude Sonnet 4.6 | `claude-sonnet-4-6` |
 | Claude Sonnet 4.5 | `claude-sonnet-4-5-20250929` |
+| Claude Haiku 5.5 | `claude-haiku-5-5` |
 | Claude Haiku 4.5 | `claude-haiku-4-5-20251001` |
 
 ## Related

diff --git a/fern/providers/model/gemini.mdx b/fern/providers/model/gemini.mdx
@@ -32,6 +32,7 @@ For additional API configuration options, review the [`GoogleModel` fields](/api
 
 | Model | Model ID |
 | --- | --- |
+| Gemini 3.8 Flash | `gemini-3.8-flash` |
 | Gemini 3.5 Flash | `gemini-3.5-flash` |
 | Gemini 3.1 Flash Lite | `gemini-3.1-flash-lite` |
 | Gemini 3 Flash | `gemini-3-flash-preview` |

diff --git a/fern/providers/model/openai.mdx b/fern/providers/model/openai.mdx
@@ -57,15 +57,15 @@ For additional API configuration options, review the [`OpenAIModel` fields](/api
 
 ## Service tier
 
-For latency-sensitive assistants, you can request OpenAI's faster processing tier by setting `model.serviceTier` on a supported model.
+For latency-sensitive assistants, you can run supported OpenAI models in OpenAI's faster processing tier. In the assistant's model settings, turn on **Priority processing**. Through the API, set `model.serviceTier` on a supported model.
 
 | Value | Behavior |
 | --- | --- |
-| `fast` | Requests OpenAI's fast processing tier for lower latency, billed at OpenAI's fast-tier rates. If OpenAI downgrades the request under load, the call is billed at standard rates. |
+| `fast` | Requests OpenAI's fast processing tier for lower latency, billed at OpenAI's fast-tier rates. If OpenAI downgrades the request under load, the call is billed at standard rates. The **Priority processing** switch sets this value. |
 | `auto` | Uses the service tier configured for your OpenAI project. |
 | `default` | Standard processing and billing. |
 
-`serviceTier` applies only to models that support fast processing: `gpt-6-luna`, `gpt-5.6-sol`, `gpt-5.6-terra`, `gpt-5.6-luna`, and `gpt-5.5`. It is ignored for other models. When unset, Vapi uses the service tier configured for your OpenAI project. See [OpenAI's pricing](https://openai.com/api/pricing) for fast-tier rates.
+`serviceTier` applies only to models that support fast processing: `gpt-6-luna`, `gpt-5.6-sol`, `gpt-5.6-terra`, `gpt-5.6-luna`, and `gpt-5.5`. It is ignored for other models. When unset, Vapi uses the service tier configured for your OpenAI project. See [OpenAI's pricing](https://openai.com/api/pricing) for fast-tier rates, and the [`OpenAIModel` fields](/api-reference/assistants/create#request.body.model.OpenAIModel) in the Create Assistant API reference.
 
 ```bash
 curl -X PATCH "https://api.vapi.ai/assistant/ASSISTANT_ID" \
@@ -76,6 +76,8 @@ curl -X PATCH "https://api.vapi.ai/assistant/ASSISTANT_ID" \
   }'
 ```
 
+When OpenAI reports the tier it served for a Fast-mode request, the model's cost in the call includes a `serviceTierBreakdown` that splits usage by served tier.
+
 ## Related
 
 <CardGroup cols={2}>

diff --git a/fern/providers/voice/cartesia.mdx b/fern/providers/voice/cartesia.mdx
@@ -40,6 +40,8 @@ For additional API configuration options, review the [`CartesiaVoice` fields](/a
 
 | Model | Model ID |
 | --- | --- |
+| Sonic 3.6 | `sonic-3.6` |
+| Sonic 3.6 (August 27, 2026 snapshot) | `sonic-3.6-2026-08-27` |
 | Sonic 3.5 | `sonic-3.5` |
 | Sonic 3.5 (May 4, 2026 snapshot) | `sonic-3.5-2026-05-04` |
 | Sonic 3 | `sonic-3` |
@@ -53,50 +55,52 @@ For additional API configuration options, review the [`CartesiaVoice` fields](/a
 
 Language support depends on the selected model. The following model and language combinations are currently supported by Vapi. Dated snapshot models (for example, `sonic-3-2026-01-12`) match their base model's language coverage.
 
-| Language | Language code | Sonic 3.5 / Sonic 3 | Sonic 2 | Sonic Preview |
-| --- | --- | --- | --- | --- |
-| Arabic | `ar` | X |  |  |
-| Bangla | `bn` | X |  |  |
-| Bulgarian | `bg` | X |  |  |
-| Chinese | `zh` | X | X |  |
-| Croatian | `hr` | X |  |  |
-| Czech | `cs` | X |  |  |
-| Danish | `da` | X |  |  |
-| Dutch | `nl` | X | X |  |
-| English | `en` | X | X | X |
-| Filipino | `tl` | X |  |  |
-| Finnish | `fi` | X |  |  |
-| French | `fr` | X | X |  |
-| Georgian | `ka` | X |  |  |
-| German | `de` | X | X |  |
-| Greek | `el` | X |  |  |
-| Gujarati | `gu` | X |  |  |
-| Hebrew | `he` | X |  |  |
-| Hindi | `hi` | X | X |  |
-| Hungarian | `hu` | X |  |  |
-| Indonesian | `id` | X |  |  |
-| Italian | `it` | X | X |  |
-| Japanese | `ja` | X | X |  |
-| Kannada | `kn` | X |  |  |
-| Korean | `ko` | X | X |  |
-| Malay | `ms` | X |  |  |
-| Malayalam | `ml` | X |  |  |
-| Marathi | `mr` | X |  |  |
-| Norwegian | `no` | X |  |  |
-| Polish | `pl` | X | X |  |
-| Portuguese | `pt` | X | X |  |
-| Punjabi | `pa` | X |  |  |
-| Romanian | `ro` | X |  |  |
-| Russian | `ru` | X | X |  |
-| Slovak | `sk` | X |  |  |
-| Spanish | `es` | X | X |  |
-| Swedish | `sv` | X | X |  |
-| Tamil | `ta` | X |  |  |
-| Telugu | `te` | X |  |  |
-| Thai | `th` | X |  |  |
-| Turkish | `tr` | X | X |  |
-| Ukrainian | `uk` | X |  |  |
-| Vietnamese | `vi` | X |  |  |
+| Language | Language code | Sonic 3.6 | Sonic 3.5 / Sonic 3 | Sonic 2 | Sonic Preview |
+| --- | --- | --- | --- | --- | --- |
+| Arabic | `ar` | X | X |  |  |
+| Bangla | `bn` | X | X |  |  |
+| Bulgarian | `bg` | X | X |  |  |
+| Chinese | `zh` | X | X | X |  |
+| Croatian | `hr` | X | X |  |  |
+| Czech | `cs` | X | X |  |  |
+| Danish | `da` | X | X |  |  |
+| Dutch | `nl` | X | X | X |  |
+| English | `en` | X | X | X | X |
+| Filipino | `tl` | X | X |  |  |
+| Finnish | `fi` | X | X |  |  |
+| French | `fr` | X | X | X |  |
+| Georgian | `ka` | X | X |  |  |
+| German | `de` | X | X | X |  |
+| Greek | `el` | X | X |  |  |
+| Gujarati | `gu` | X | X |  |  |
+| Hebrew | `he` | X | X |  |  |
+| Hindi | `hi` | X | X | X |  |
+| Hungarian | `hu` | X | X |  |  |
+| Indonesian | `id` | X | X |  |  |
+| Italian | `it` | X | X | X |  |
+| Japanese | `ja` | X | X | X |  |
+| Kannada | `kn` | X | X |  |  |
+| Korean | `ko` | X | X | X |  |
+| Malay | `ms` | X | X |  |  |
+| Malayalam | `ml` | X | X |  |  |
+| Marathi | `mr` | X | X |  |  |
+| Norwegian | `no` | X | X |  |  |
+| Odia | `or` | X |  |  |  |
+| Polish | `pl` | X | X | X |  |
+| Portuguese | `pt` | X | X | X |  |
+| Punjabi | `pa` | X | X |  |  |
+| Romanian | `ro` | X | X |  |  |
+| Russian | `ru` | X | X | X |  |
+| Slovak | `sk` | X | X |  |  |
+| Spanish | `es` | X | X | X |  |
+| Swedish | `sv` | X | X | X |  |
+| Tamil | `ta` | X | X |  |  |
+| Telugu | `te` | X | X |  |  |
+| Thai | `th` | X | X |  |  |
+| Turkish | `tr` | X | X | X |  |
+| Ukrainian | `uk` | X | X |  |  |
+| Urdu | `ur` | X |  |  |  |
+| Vietnamese | `vi` | X | X |  |  |
 
 ## Related