Add changelog for 2025-06-11 (#504)

Author: quantstruct-bot

fern/changelog/2025-06-11.mdx

@@ -0,0 +1,29 @@
+# Assembly AI Transcriber Improvements, chat cost tracking, and API tool enhancements
+
+1. **Chat Cost Tracking**: You can now access detailed cost information per [Chat](https://api.vapi.ai/api#:~:text=FunctionCall-,Chat,-CreateChatDTO) and [Call](https://api.vapi.ai/api#:~:text=SchedulePlan-,Call,-CallBatchError), including total and per-component breakdowns. Use `Call.cost` and `Chat.cost` to get the total cost, and `Call.costs` and `Chat.costs` to get the breakdown.`
+
+  <CodeBlocks>
+  ```json title="Chat Schema (excerpt)"
+  {
+    "cost": 0.12,
+    "costs": [
+      { "type": "model", "cost": 0.22 },
+      { "type": "chat", "cost": 0.10 },
+    ]
+  }
+  ```
+  </CodeBlocks>
+
+2. **Enhanced AssemblyAI Transcriber Configuration**: You can now fine-tune the AssemblyAI transcriber with:
+  - `maxTurnSilence`: The maximum amount of silence in milliseconds before a turn is considered complete.
+  - `endOfTurnConfidenceThreshold`: The confidence threshold for determining the end of a turn.
+  - `minEndOfTurnSilenceWhenConfident`: The minimum amount of silence in milliseconds before a turn is considered complete when the confidence is high.
+  - `wordFinalizationMaxWaitTime`: The maximum amount of time in milliseconds to wait for word finalization.
+
+3. **New Cartesia Transcriber Option**: You can now use the [Cartesia "Ink Whisper" transcriber](https://api.vapi.ai/api#:~:text=CartesiaTranscriber) for your for assistants and workflow nodes using `Assistant.transcriber` and `ConversationNode.transcriber`. Set this in your [Vapi Assistant dashboard today](https://dashboard.vapi.ai/assistants#:~:text=Transcriber).
+
+<Frame caption="Cartesia Transcriber">
+    <img src="../static/images/changelog/cartesia-transcriber.png" alt="Cartesia Transcriber" />
+</Frame>
+
+4. **API Request Tool Variable Extraction**: You can now use [`assistant.model.tools[type=apiRequest].variableExtractionPlan`](https://api.vapi.ai/api#:~:text=VariableExtractionPlan) to extract and validate variables from API responses by defining a variable schema.