Replace AssemblyAI STT with Inworld STT API

[cherylafichter]

• Create InworldSTTNode using Inworld's REST API (POST /stt/v1/transcribe) with energy-based VAD for end-of-turn detection
• Remove assembly-ai-stt-ws-node.ts and its WebSocket-based streaming logic
• Update ConversationGraphWrapper to hold inworldSTTNode reference
• Update ConversationGraphConfig to accept inworldApiKey (was assemblyAIApiKey)
• Replace ASSEMBLY_AI_API_KEY env var with INWORLD_API_KEY in graph-service, .env.example, and render.yaml (single key for all Inworld services)
• Replace AssemblyAI turn-detection presets in server config with equivalent Inworld STT VAD presets (silenceThresholdMs / minSpeechMs / energyThreshold)
• Rename ASSEMBLY_AI_EAGERNESS env var to INWORLD_STT_EAGERNESS
• Update comments in connection-manager, transcript-extractor-node, server, and audio-processor.js to reflect the new STT provider

https://claude.ai/code/session_01EDqcCeQHNj2f2TVeFb5Dxh

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[Copilot]

Pull request overview

This PR migrates the backend speech-to-text pipeline from AssemblyAI’s streaming WebSocket node to a new Inworld STT REST-based node with energy-based VAD, and removes AssemblyAI-specific configuration/env keys accordingly.

Changes:

• Removed AssemblyAI env/config usage and updated logs/comments to reference Inworld STT.
• Added InworldSTTNode (REST transcription + energy-based VAD) and rewired the conversation graph to use it.
• Updated server config to provide VAD “eagerness” presets for the new STT approach.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
render.yaml	Removes ASSEMBLY_AI_API_KEY from Render env vars.
frontend/public/audio-processor.js	Updates comments to reflect Inworld STT + energy-based VAD chunking rationale.
backend/src/services/graph-service.ts	Switches graph init env validation from AssemblyAI key to INWORLD_API_KEY.
backend/src/server.ts	Updates documentation/log strings to reflect Inworld STT usage.
backend/src/helpers/connection-manager.ts	Updates STT naming + changes session teardown behavior for STT cleanup.
backend/src/graphs/nodes/transcript-extractor-node.ts	Updates node documentation to reference Inworld STT output.
backend/src/graphs/nodes/inworld-stt-node.ts	New node implementing energy-based VAD + REST transcription.
backend/src/graphs/nodes/assembly-ai-stt-ws-node.ts	Removes the AssemblyAI WebSocket STT node implementation.
backend/src/graphs/conversation-graph.ts	Replaces AssemblyAI STT node with InworldSTTNode and updates graph wiring/config.
backend/src/config/server.ts	Replaces AssemblyAI turn-detection presets with Inworld STT VAD presets and env var.
backend/.env.example	Removes ASSEMBLY_AI_API_KEY from the example env file.

Files not reviewed (1)

• backend/package-lock.json: Language not supported

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.