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Speko continuously benchmarks every supported STT, LLM, and TTS provider across language, vertical, and three performance axes (accuracy, latency, cost). Every API call carries a RoutingIntent. The router scores candidates against that intent, picks the top-ranked provider, and falls back through runners-up if the primary fails.

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Intent

type RoutingIntent = {
  language: string;          // BCP-47, e.g. "en-US", "es-MX"
  vertical: 'general' | 'healthcare' | 'finance' | 'legal';
  optimizeFor?: 'balanced' | 'accuracy' | 'latency' | 'cost'; // default: balanced
};
language is required. vertical selects the benchmark slice. optimizeFor chooses a weight preset:
PresetAccuracyLatencyCost
balanced (default)0.50.30.2
accuracy0.80.150.05
latency0.20.70.1
cost0.150.150.7

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Selection

For each modality (STT / LLM / TTS) the selector:
  1. Filters the benchmark set to providers with data for (language, vertical).
  2. Drops any provider whose recent error rate exceeds 50 %.
  3. Computes a weighted score per candidate using the chosen preset.
  4. Returns a SelectedCandidate (providerId, modelId, score) plus an ordered runnersUp list.
Each call also returns a scoresRunId — the benchmark snapshot the decision was based on. Useful for audit and bug repro.

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Failover

The runners-up are not fallbacks of last resort — they are the next-best provider for your exact intent. If the primary throws, Speko transparently retries the same request against the next candidate. The response includes failoverCount (how many providers it tried before one succeeded) and provider / model (what actually ran). If every candidate fails, the call returns ALL_PROVIDERS_FAILED.

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Constraints

Pin or restrict the candidate pool per modality: 
{
  "constraints": {
    "allowedProviders": {
      "stt": ["deepgram"],
      "tts": ["cartesia"]
    }
  }
}
Speko still ranks by score — it just picks the highest-ranking candidate that’s in your allow-list. Use this to:
  • Pin a provider while debugging.
  • Honor compliance constraints (data residency, BAA coverage).
  • Cap costs by excluding premium providers.

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Preview before you ship

Hit GET /v1/routing/preview?language=en-US&vertical=healthcare&optimize_for=accuracy to see what the router would pick, including runners-up and scoresRunId. No usage is recorded.

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Headers on every response

Every /v1/transcribe, /v1/synthesize, /v1/complete response carries:
  • X-Speko-Provider — provider that handled the request
  • X-Speko-Model — specific model
  • X-Speko-Failover-Count — how many providers we tried
  • X-Speko-Scores-Run-Id — benchmark snapshot id
Log these. They’re how you correlate prod behavior with the routing decision.