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Cost Tracking

Arkenos tracks the cost of every API call made during voice sessions — STT minutes, LLM tokens, and TTS characters.

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How Costs Are Tracked

  1. The agent worker logs usage events in real-time via POST /api/usage/events
  2. Each event records the provider, service type, units consumed, and calculated cost
  3. The backend aggregates costs for dashboards and reports

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Provider Rates

Rates are defined in backend/app/cost_rates.py and can be updated in one place.
ServiceProviderUnitRateHourly Equivalent
STTDeepgramper minute$0.0077$0.46/hr
STTAssemblyAIper minute$0.0078$0.47/hr
STTElevenLabsper minute$0.0167$1.00/hr
LLMGoogle Gemini 2.5 Flashper 1K tokens (blended)$0.00086~$0.86/1M tokens
TTSResemble AIper character$0.00004$40/1M chars
The Gemini rate is a blended estimate assuming a ~3:1 input-to-output token ratio. Actual rates: 0.30/1Minputtokens,0.30/1M input tokens, 2.50/1M output tokens.

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Usage Event Structure

{
  "session_id": "uuid",
  "user_id": "user-id",
  "agent_id": "agent-uuid",
  "provider": "assemblyai",
  "event_type": "stt_minutes",
  "quantity": 2.5,
  "unit_cost": 0.0078,
  "total_cost": 0.0195
}

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Dashboard Views

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Cost Summary

Dashboard → Costs shows:
  • Total cost across all sessions
  • This month’s cost
  • Breakdown by provider (pie chart)

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Cost Timeline

View costs over time with daily, weekly, or monthly granularity.

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Cost by Agent

See which agents cost the most, helping you optimize prompts and configurations.

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Per-Session Breakdown

Dashboard → Call Logs → [Session] shows the cost breakdown for a single call:
ProviderServiceUnitsCost
AssemblyAISTT2.5 minutes$0.0195
Google GeminiLLM1,250 tokens$0.0011
Resemble AITTS450 characters$0.0180
Total$0.0386

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What’s Not Tracked

Arkenos currently does not track costs for:
  • LiveKit — connection minutes (~$0.0005/min per participant). These are billed by LiveKit directly.
  • Twilio — per-minute telephony charges for inbound/outbound calls. These are billed by Twilio directly.
These costs are external to the voice pipeline and must be monitored in each provider’s billing dashboard.

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API Endpoints

# Cost summary
curl -H "x-user-id: your-user-id" http://localhost:8000/api/costs/summary

# Cost timeline (daily/weekly/monthly)
curl -H "x-user-id: your-user-id" "http://localhost:8000/api/costs/timeline?period=daily"

# Cost by agent
curl -H "x-user-id: your-user-id" http://localhost:8000/api/costs/by-agent