VOICE
ElevenLabs API
Handles both STT (speech-to-text) and TTS (text-to-speech). Streaming TTS keeps conversational latency under 600ms response time.
REASONING
GPT-4
Two GPT-4 instances: one as Interviewer (question generation) and one as Evaluator (answer scoring). Separated for clear role boundaries.
DECISIONING
Decision Model
Custom Python scoring model. Weighted average of 4 GPT-4 evaluation dimensions. Binary threshold tuned per job role requirements.
BACKEND
FastAPI + Python
Session orchestrator. Manages conversation state, queues follow-up questions, and coordinates between STT, LLM, and TTS services.
DISPATCH
Webhooks
Signed POST webhooks deliver the final decision payload — candidate ID, score breakdown, decision label, and full transcript — to the HR system.
SDK
OpenAI SDK
Function calling enforces structured JSON output from the Evaluator agent, ensuring consistent score schema for the Decision Model.