Metrics & Cost Tracking

Per-call cost breakdown, latency analytics, and real-time metrics.

Metrics & Cost Tracking

Patter automatically tracks cost and latency for every call, broken down by provider component (STT, TTS, LLM, telephony).

How It Works

Metrics are collected automatically during calls. When a call ends, the onCallEnd callback receives a CallMetrics object with the full breakdown:

await phone.serve({
  agent,
  port: 8000,
  onCallEnd: async (event) => {
    const metrics = event.metrics;
    if (metrics) {
      console.log(`Duration: ${metrics.duration_seconds}s`);
      console.log(`Total cost: $${metrics.cost.total.toFixed(4)}`);
      console.log(`  STT: $${metrics.cost.stt.toFixed(4)}`);
      console.log(`  TTS: $${metrics.cost.tts.toFixed(4)}`);
      console.log(`  LLM: $${metrics.cost.llm.toFixed(4)}`);
      console.log(`  Telephony: $${metrics.cost.telephony.toFixed(4)}`);
      console.log(`Avg latency: ${metrics.latency_avg.total_ms}ms`);
      console.log(`P95 latency: ${metrics.latency_p95.total_ms}ms`);
    }
  },
});

Cost Breakdown

The CostBreakdown object provides per-component costs in USD:

Field	Description
stt	Speech-to-text cost (Deepgram, Whisper).
tts	Text-to-speech cost (ElevenLabs, OpenAI TTS).
llm	LLM cost (OpenAI Realtime tokens).
telephony	Telephony cost (Twilio, Telnyx per-minute).
total	Sum of all components.

Latency Breakdown

The LatencyBreakdown object provides per-component latency in milliseconds:

Field	Description
stt_ms	Time from user speech to transcript.
endpoint_ms	Time the endpointer waited after the last word before declaring end-of-utterance.
llm_ttft_ms	Time from end-of-utterance to the first LLM token.
llm_total_ms	Time from end-of-utterance to the last LLM token (full response).
llm_ms	Alias for llm_ttft_ms (kept for back-compat).
tts_ms	Time from first LLM token to first TTS audio byte.
tts_total_ms	Time from first LLM token to last TTS audio byte.
bargein_ms	Time from caller voice detected to TTS playback cancelled (only set on barge-in turns).
total_ms	End-to-end latency (user speech to first audio).

CallMetrics exposes the full distribution: latency_avg, latency_p50 (median / typical UX), latency_p90 (steady-state outliers), latency_p95 (SLA), and latency_p99 (cold-start outliers).

Per-Turn Metrics

Each conversation turn is tracked individually:

await phone.serve({
  agent,
  port: 8000,
  onCallEnd: async (event) => {
    const metrics = event.metrics;
    if (metrics) {
      for (const turn of metrics.turns) {
        console.log(`Turn ${turn.turn_index}:`);
        console.log(`  User: ${turn.user_text}`);
        console.log(`  Agent: ${turn.agent_text}`);
        console.log(`  Latency: ${turn.latency.total_ms}ms`);
      }
    }
  },
});

Custom Pricing

Override default provider pricing estimates:

TypeScript

await phone.serve({
  agent,
  port: 8000,
  pricing: {
    deepgram: { price: 0.005 },      // Override STT price per minute
    elevenlabs: { price: 0.15 },      // Override TTS price per 1k chars
    twilio: { price: 0.015 },         // Override telephony price per minute
  },
});

PricingUnit

The pricing tables expose a PricingUnit constant so overrides don’t depend on raw strings:

import { PricingUnit } from "getpatter";

PricingUnit.MINUTE;          // "minute" — per minute of audio (STT, telephony)
PricingUnit.THOUSAND_CHARS;  // "1k_chars" — per thousand characters synthesised (TTS)
PricingUnit.TOKEN;           // "token" — per token (LLM / Realtime)

Shipped as a const object plus value-union type so it is tree-shakeable. Mirrored byte-for-byte by the Python PricingUnit StrEnum.

Model-Aware Pricing

Patter’s pricing tables are model-aware: every entry in DEFAULT_PRICING carries provider-level defaults plus an optional models map keyed by model identifier. When the agent’s adapter exposes a model field, the metrics layer threads it through the cost-calc functions and the dashboard bills with model accuracy out of the box — no manual override required.

import { PRICING_VERSION, PRICING_LAST_UPDATED } from "getpatter";

PRICING_VERSION;       // "2026.3"
PRICING_LAST_UPDATED;  // "2026-05-08"

How resolution works

The cost-calc helpers (calculateSttCost, calculateTtsCost, calculateRealtimeCost, calculateRealtimeCachedSavings) accept an optional final model parameter. The exported resolveProviderRates(config, model) helper merges per-model overrides on top of provider defaults using:

1. Exact match in the provider’s models map.
2. Longest-prefix match — gpt-realtime-2-2026-05-08 resolves against gpt-realtime-2.
3. Provider defaults — fallback when the model is unknown or omitted.

CallMetricsAccumulator auto-tracks sttModel, ttsModel, and realtimeModel from the agent’s adapter model field (agent.stt.model, agent.tts.model, agent.model for Realtime). On every recordRealtimeUsage(usage) call the realtime model is also pulled from the response.done payload itself, overriding the call-level default — so mid-call model switches are billed correctly.

The optional model argument defaults to undefined, which preserves the legacy provider-rate behaviour. Existing callers compile and run unchanged.

Example A — Just select a model

The most common case: pick a model on your adapter, and Patter bills the right rate automatically.

TypeScript

import { Patter, Twilio } from "getpatter";
import { OpenAIRealtimeAdapter, OpenAIRealtimeModel } from "getpatter";

const agent = Patter.agent({
  systemPrompt: "You are a helpful assistant.",
  realtime: new OpenAIRealtimeAdapter({ model: OpenAIRealtimeModel.GPT_REALTIME_2 }),
});

const phone = new Patter({ carrier: new Twilio(), phoneNumber: "[phone]" });
// Billing auto-uses the gpt-realtime-2 rate ($32/M audio in, $64/M audio out).

Example B — Override one model, keep siblings intact

mergePricing overlays the nested models map shallowly. Overriding a single model leaves the other rates inside the same provider untouched.

TypeScript

const phone = new Patter({
  carrier: new Twilio(),
  phoneNumber: "[phone]",
  pricing: {
    // Negotiated a discount on Nova-2 only — Nova-3 / Whisper rates stay default.
    deepgram: { models: { "nova-2": { price: 0.004 } } },
  },
});

Example C — Register a brand-new model rate

Add a model that isn’t in the built-in table without touching SDK source.

TypeScript

const phone = new Patter({
  carrier: new Twilio(),
  phoneNumber: "[phone]",
  pricing: {
    elevenlabs: {
      models: { my_custom_voice: { price: 0.075 } },
    },
  },
});
// When agent.tts.model === "my_custom_voice", calculateTtsCost picks up $0.075/1k.

Default Pricing (2026.3)

Provider-level defaults are listed below. Per-model rates live under DEFAULT_PRICING[provider].models and are auto-resolved when the adapter exposes its model identifier.

Provider	Unit	Default Price (default model)
Deepgram (nova-3 streaming mono)	per minute	$0.0077
OpenAI Whisper (whisper-1)	per minute	$0.006
OpenAI Transcribe (gpt-4o-transcribe)	per minute	$0.006
AssemblyAI	per minute	$0.0025
Cartesia STT (ink-whisper)	per minute	$0.0025
Soniox	per minute	$0.002
Speechmatics (Pro)	per minute	$0.004
ElevenLabs (eleven_flash_v2_5)	per 1k chars	$0.06
OpenAI TTS (tts-1)	per 1k chars	$0.015
Cartesia TTS (sonic-2)	per 1k chars	$0.030
Rime (mistv2)	per 1k chars	$0.030
LMNT (aurora)	per 1k chars	$0.050
Inworld (inworld-tts-2)	per 1k chars	$0.020
OpenAI Realtime (gpt-realtime-mini / gpt-4o-mini-realtime-preview)	per token	$10/M audio in ·$20/M audio out · $0.60/M text in ·$2.40/M text out (cached: $0.30/M audio ·$0.06/M text)
Twilio (US inbound local)	per minute	$0.0085 (rounded up to whole minute, per Twilio)
Telnyx	per minute	$0.007

STT — per-model rates

Provider	Model	Price
Deepgram	nova-3 (default)	$0.0077/min
Deepgram	nova-3-multilingual	$0.0092/min
Deepgram	nova-2	$0.0058/min
Deepgram	nova	$0.0043/min
Deepgram	whisper-large / whisper-medium	$0.0048/min
OpenAI Whisper	whisper-1 (default)	$0.006/min
OpenAI Whisper	gpt-4o-transcribe	$0.006/min
OpenAI Whisper	gpt-4o-mini-transcribe	$0.003/min
OpenAI Whisper	gpt-realtime-whisper	$0.017/min
OpenAI Transcribe (openai_transcribe)	gpt-4o-transcribe (default)	$0.006/min
OpenAI Transcribe	gpt-4o-mini-transcribe	$0.003/min
OpenAI Transcribe	whisper-1	$0.006/min

TTS — per-model rates

Provider	Model	Price
ElevenLabs (REST + WebSocket)	eleven_flash_v2_5 (default)	$0.06/1k
ElevenLabs	eleven_turbo_v2_5	$0.05/1k
ElevenLabs	eleven_multilingual_v2 / eleven_monolingual_v1	$0.18/1k
ElevenLabs	eleven_v3	$0.30/1k
OpenAI TTS	tts-1 (default)	$0.015/1k
OpenAI TTS	tts-1-hd	$0.030/1k
OpenAI TTS	gpt-4o-mini-tts	$0.012/1k
Cartesia	sonic-1 / sonic-2 / sonic-english / sonic-multilingual	$0.030/1k
Rime	mistv2 (default) / mist	$0.030/1k
Rime	arcana	$0.040/1k
LMNT	aurora (default) / blizzard	$0.050/1k
Inworld	inworld-tts-2 (default)	$0.020/1k
Inworld	inworld-tts-1.5-max / inworld-tts-1.5	$0.025/1k

OpenAI Realtime — per-model rates

Model	Audio in / out (per token)	Text in / out (per token)	Cached audio / text (per token)
gpt-realtime-mini (default) / gpt-4o-mini-realtime-preview	$0.00001 /$0.00002	$0.0000006 /$0.0000024	$0.0000003 /$0.00000006
gpt-realtime	$0.000032 /$0.000064	$0.000004 /$0.000016	$0.0000004 /$0.0000004
gpt-realtime-2	$0.000032 /$0.000064	$0.000004 /$0.000024	$0.0000004 /$0.0000004
gpt-4o-realtime-preview	$0.0001 /$0.0002	$0.000005 /$0.000020	$0.0000020 /$0.0000025

gpt-4o-realtime-preview is roughly 10x the cost of gpt-realtime-mini for audio. Switching realtime models has direct billing impact — confirm the model on agent.realtime.model matches the rate you expect.

Twilio defaults match US inbound local. Override pricing.twilio.price for US toll-free inbound (~$0.022/min) or US outbound local (~$0.014/min). Default pricing is based on publicly listed provider rates and may become stale — check the provider’s pricing page or pass your own overrides for authoritative numbers.

Real-Time Metrics

Use the onMetrics callback for live cost updates during a call:

await phone.serve({
  agent,
  port: 8000,
  onMetrics: async (data) => {
    const turn = data.turn as Record<string, unknown>;
    const latency = turn.latency as Record<string, number>;
    console.log(`Call ${data.call_id} — turn ${turn.turn_index}`);
    console.log(`  Latency: ${latency.total_ms}ms`);
  },
});

Data Types

import type {
  CallMetrics,
  CostBreakdown,
  LatencyBreakdown,
  TurnMetrics,
} from "getpatter";

CallMetrics

Field	Type	Description
call_id	string	Unique call identifier.
duration_seconds	number	Total call duration.
turns	TurnMetrics[]	Per-turn metrics.
cost	CostBreakdown	Cost breakdown.
latency_avg	LatencyBreakdown	Average latency.
latency_p50	LatencyBreakdown	Median (50th percentile) latency.
latency_p95	LatencyBreakdown	95th percentile latency.
latency_p99	LatencyBreakdown	99th percentile latency (cold-start outliers).
provider_mode	string	Voice mode used.
stt_provider	string	STT provider name.
tts_provider	string	TTS provider name.
llm_provider	string	LLM provider name.
telephony_provider	string	Telephony provider name.

TurnMetrics

Field	Type	Description
turn_index	number	Zero-based turn index.
user_text	string	What the user said.
agent_text	string	What the agent replied.
latency	LatencyBreakdown	Latency for this turn.
stt_audio_seconds	number	Audio duration processed by STT.
tts_characters	number	Characters synthesized by TTS.
timestamp	number	Unix timestamp.