Recommended stack

{
  "stt": { "default": { "provider": "soniox", "model": "stt-rt-v4", "language": "ur" } },
  "llm": { "default": { "provider": "openai", "model": "gpt-5.4-nano", "reasoningEffort": "low", "verbosity": "low" } },
  "tts": { "default": { "provider": "upliftai", "voiceId": "helpdesk-agent", "outputFormat": "MP3_22050_32" } }
}

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Why these

• STT: soniox. Native streaming, so no chunking tricks. Built for Urdu, and the language hint doesn’t lock it in: English and Punjabi words your callers mix in still come through.
• LLM: gpt-5.4-nano, reasoning and verbosity low. Fast, cheap, and it follows a script. low verbosity matters on voice: a chatty model is a slow call.
• TTS: upliftai. 80+ voices tuned for Urdu and regional languages, and first audio in 100–200ms. It’s the only part of the stack we own end to end. Start with helpdesk-agent.

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When to step up

• Calls that need more judgment (objection handling, open questions): move the LLM to gpt-5.4-mini. It’s the default for campaign assistants on the portal.
• Latency above all: gemini-2.5-flash is the fastest model we run. gemini-3.5-flash is a good balance of intelligence and speed. Mind the thinking knobs — see How it works.