chore: add changelog for 2025-06-23 with breaking schema removals and developer guidance

fern/changelog/2025-06-21.mdx

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+---
+title: "Changelog – 2025-06-21"
+description: "Vapi API and Workflow changes released on June 21, 2025."
+---
+
+# 2025-06-21 Changelog
+
+## Major Breaking Changes
+
+### Removal of Assistant, Tool, and Chat Schema Properties
+- Numerous properties and schema paths have been **removed** from the API, including many related to `Assistant`, `AssistantOverrides`, `Chat`, `Workflow`, `Credential` types, and various `ServerMessage*` objects. This includes:
+  - Removal of background denoising and speech denoising plans from assistants and workflows
+  - Removal of several properties from credential objects (e.g., fallbackIndex, region)
+  - Significant reduction in `chat`-related properties from server message schemas
+  - Removal of API Request Tool discriminator mappings from multiple endpoints
+  - Removal of variable extraction plan, name patterns, and other properties from tool creation
+
+> **Action Required:**
+> - If your integration relies on any of the removed properties or schemas, update your code to avoid referencing them. Calls using deprecated fields will now fail validation.
+
+### AssemblyAITranscriber and FallbackAssemblyAITranscriber
+- The following properties were **removed**: `formatTurns`, `maxTurnSilence`, `wordFinalizationMaxWaitTime`, `endOfTurnConfidenceThreshold`, `minEndOfTurnSilenceWhenConfident`.
+
+## Additions
+
+### Workflow Enhancements
+- New schema properties and definitions have been **added** for Workflows:
+  - `Workflow.model`: Now supports specifying a model at the workflow level. Accepts `WorkflowOpenAIModel` or `WorkflowAnthropicModel`.
+  - New edge condition types: `LogicEdgeCondition` and `FailedEdgeCondition` are now supported in workflow edges. `LogicEdgeCondition` uses a `liquid` template string for advanced branching.
+
+> **For Developers:**
+> - You can now specify a model for the entire workflow, providing greater flexibility and control over LLM selection.
+> - Use `LogicEdgeCondition` for complex, liquid-based conditional branching in workflow edges.
+
+## Migration Guidance
+- Review all usage of removed properties and schemas, especially if you use advanced assistant, tool, or workflow customization features.
+- Migrate workflow branching logic to use the new `LogicEdgeCondition` and `FailedEdgeCondition` schemas where applicable.
+- Update your workflow definitions to optionally include the new `model` property for global LLM configuration.
+
+---
+
+For questions or migration help, please reach out to the Vapi team or open an issue in the repository.

fern/changelog/2025-06-22.mdx

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+---
+title: Changelog for 2025-06-22
+---
+
+# Changelog — 2025-06-22
+
+## Major API Additions
+
+- **Campaigns API**: New endpoints and schemas for managing outbound calling campaigns. This includes campaign lifecycle management (`/campaign`, `/campaign/{id}`), scheduling, customer lists, call statistics, and campaign status tracking. This enables orchestrating large-scale outbound calling via Vapi.
+- **Credential Management**: New credential types supported for S3, GCP, Azure, Supabase, and Cloudflare. Each credential now supports fallback order (`fallbackIndex`) for robust artifact upload and storage.
+- **New Tool Types**: 
+  - **API Request Tool**: Added endpoints and schemas for defining API request tools, including custom function definitions, variable extraction plans, and retry/backoff strategies.
+  - **MCP Tool**: Added support for MCP (Model-Controlled Plugin) tools with protocol metadata. Webhook server precedence for tool calls is now well-defined.
+
+## Workflow & Assistant Enhancements
+
+- **Background Speech Denoising**: Assistants and workflows now support advanced background speech denoising via Krisp (Smart Denoising) and experimental Fourier denoising. Both can be enabled and configured independently or together.
+- **Transcriber Updates**: Added Cartesia, AssemblyAI, and fallback plans for transcribers, including new configuration options (e.g., `formatTurns`, `maxTurnSilence`, `minEndOfTurnSilenceWhenConfident`).
+- **Voice Model Improvements**: LMNTVoice and FallbackLMNTVoice now support language selection and improved fallback logic.
+- **AssistantOverrides & WorkflowOverrides**: New properties for granular runtime overrides, including background denoising and credential injection.
+
+## Cost Tracking & Observability
+
+- **Cost Breakdown**: Calls and chats now include detailed cost breakdowns for each component (LLM, STT, TTS, transport, Vapi, analysis, etc.).
+- **Langfuse Observability**: Workflows and assistants now support Langfuse for detailed trace and span tracking.
+
+## Minor Improvements & Fixes
+
+- **Compliance & Monitoring**: Workflows and assistants now support compliance plans (HIPAA etc.), monitoring plans for live listening/control, and improved webhook routing.
+- **Artifact & Analysis Plans**: New schema properties for storing and configuring artifacts and analysis at both assistant and workflow levels.
+- **ServerMessage Updates**: All server and client messages now consistently include `chat` and `call` objects for easier integration.
+- **Parameter Extraction**: Variable extraction plans can now be attached to API Request tools, improving structured data extraction from tool results.
+
+## Breaking Changes
+
+- **Removed**: Deprecated properties in Workflow schemas (e.g., `model` at the workflow root level) have been removed. Ensure you use node-level model configuration.
+
+---
+
+**Upgrade Guidance**:
+- Review new credential management and denoising options for enhanced reliability and call quality.
+- Update tool and workflow definitions to leverage new API Request and MCP tool capabilities.
+- For custom integrations, ensure server endpoints handle new webhook payloads and cost breakdowns.
+
+For detailed API reference, see [OpenAPI Spec](../reference).

fern/changelog/2025-06-23.mdx

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+---
+title: Changelog for 2025-06-23
+---
+
+# Changelog — 2025-06-23
+
+## Breaking API Changes
+
+- **Schema Removals:**
+  - Several schemas and properties were removed to simplify and clarify the Vapi API surface:
+    - `McpTool.metadata`, `Chat.assistantOverrides`, `Campaign.callsCounter*`, `LMNTVoice.language`, `FallbackLMNTVoice.language`, `CreateMcpToolDTO.metadata`, `UpdateMcpToolDTO.metadata`, `OpenAIResponsesRequest.assistantOverrides`.
+    - Node-level `model` for tool and workflow nodes (e.g., `call.workflow.nodes[type=conversation].model`) have been removed for custom models. Ensure you configure models at the correct node level.
+    - `assistant.voice`, `call.squad.members.assistant.voice`, `call.squad.members.assistantOverrides.voice`, and related voice model properties have been adjusted, with fallback plans now required in some places.
+
+## Developer Impact
+
+- **Migration Required:**
+  - If your integration or workflow relies on the above properties, update your payloads and workflow definitions to remove deprecated fields and migrate to the new structure. See the [migration guide](../reference) for field mapping examples.
+- **Simplified Tool Configuration:**
+  - MCP Tool and API Request Tool schemas are now more streamlined, with redundant metadata and overrides removed. This makes tool configuration more predictable and reduces ambiguity for tool invocation.
+
+## Why this matters for Vapi developers
+
+- **Cleaner API Contracts:** By removing unused/deprecated fields, Vapi APIs are easier to integrate, validate, and maintain. This leads to fewer surprises and more predictable behavior for custom assistants, campaign management, and workflow automation.
+- **Reduced Error Surface:** Eliminating ambiguous override fields (like `assistantOverrides` in multiple places) prevents accidental misconfiguration and runtime errors.
+- **Next Steps:**
+  - Audit your assistant, tool, workflow, and campaign definitions for the removed fields.
+  - Test against the latest OpenAPI spec to ensure compatibility.
+  - Reach out to support if you need help with migration strategies or have custom use cases impacted by these removals.
+
+---
+
+For a full reference of the latest API, see [OpenAPI Spec](../reference).