Sonex Labs vs Sarvam AI: which fits your Indian voice product?

Why are teams comparing Sarvam and Sonex Labs now?

Teams building Indian voice products usually shortlist Sarvam early: it is India-focused, has its own speech recognition, text to speech and voice agents, and prices in rupees. Two October 2026 changes have pushed many of those teams to look again. On 13 October Sarvam launched Bulbul V4 Flash at ₹20 per 10,000 characters. A day later its changelog announced that Bulbul V3 reaches end of life on Voice Agents on 10 November 2026, and that every agent speaking with V3 has to move to Bulbul V4 before then. V3 stays available on the text to speech API.

A new voice model changes how your agent sounds, so you'll be re-listening to calls either way, which makes it a sensible moment to test an alternative on the same scripts. This article compares the two on language and dialect coverage, latency, total cost at your volume, and what each agent platform includes. Every Sarvam fact below links to Sarvam's own pages, checked on 24 October 2026.

What are Sonex Labs and Sarvam AI?

Sonex Labs is a voice AI platform for multilingual calls. Our Pāṇini text to speech speaks 250+ languages in 34 writing systems, including 36+ Indian languages and dialects, with 120 platform voices. Valmiki speech recognition covers 100+ languages. Sonex Flows, our voice agent product, bundles recognition, synthesis and telephony on Sonex numbers into one per-minute price, with the language model chosen separately. Prices are in US dollars on our pricing page.

Sarvam AI is an Indian company that sells speech and language models for Indian languages as APIs and as a managed voice agent product. Its text to speech family is Bulbul: Bulbul V3 covers 10 Indian languages plus Indian English, and Bulbul V4 Flash covers Hindi, English, an English–Hindi code-mix style, Bengali, Gujarati, Kannada, Marathi, Punjabi, Tamil and Telugu. Its speech recognition model, Saaras, transcribes 22 Indian languages plus English. The API is priced per character and per minute; the voice agent product is priced per minute with the speech, language and voice models included.

What should decide the choice?

Start with who is on the other end of the call. If your callers speak Hindi, Tamil or Bengali in their standard forms, most vendors cover you. If they speak Bhojpuri, Marwari or Garhwali at home, or call from outside India, coverage is the first filter, and a voice in the wrong variety costs you more in dropped calls than any per-character saving.

Then look at the audio path. Phone calls carry narrowband 8 kHz audio, so a voice that sounds good in a demo can sound thin on a call. Latency matters too: ITU-T G.114 recommends keeping one-way delay under 150 ms for most conversational use, and an agent adds recognition, model and synthesis time on top of the network. After that comes total cost at your real volume, with the language model, telephony and every language you need included, then who owns the phone numbers.

How do Sonex Labs and Sarvam compare at a glance?

Which covers the languages your customers actually speak?

Pāṇini speaks 250+ languages in 34 writing systems, and the full list is on our languages page. For India that is 36+ languages and dialects, including Bhojpuri, Marwari, Haryanvi, Garhwali, Maithili, Chhattisgarhi, Mewari, Saraiki, Bundeli, Braj, Angika and Bhili, and Dogri, Konkani, Tulu and Santali. Sarvam's voices speak 10 Indian languages plus English on Bulbul V3, its docs note that Malayalam and Odia are not yet offered on V4 Flash, and it does not list any dialects for text to speech. If a real share of your callers speak a dialect at home, this is the factor most likely to decide it, because a dialect speaker notices within a sentence when the voice is speaking the standard form instead.

Coverage also runs beyond India: the same 250+ languages are billed at one rate, so a business with customers in several countries runs one vendor and one price. That includes Arabic in Modern Standard Arabic and nine dialects: Gulf, Egyptian, Levantine, Najdi, Iraqi, Moroccan, Algerian, Tunisian and Sudanese. For mixed-language speech, Pāṇini reads Hinglish and other mixed text naturally in one voice (Hinglish), and one voice, or one clone, can speak across languages. Sarvam's speech recognition supports code-mixed audio, and Bulbul V4 Flash offers an English–Hindi code-mix style on some voices. Test your own mixed-language scripts on both, on our language playgrounds and on Sarvam's.

For speech recognition, Valmiki covers 100+ languages and detects the spoken language automatically, which helps when a caller answers in a different language from the one you expected. Sarvam's list is explicit about India: Saaras covers 22 Indian languages plus English, naming Dogri, Konkani, Bodo, Santali, Manipuri and Kashmiri. With V3 leaving Sarvam Voice Agents on 10 November, Sarvam customers should also check every language their agents speak on Bulbul V4 before they migrate.

How do they sound and respond on phone calls?

Pāṇini is trained for 8 kHz phone audio. Sarvam's Bulbul API can output 8 kHz among other sample rates, the rate phone lines carry. On latency, we report under 200 ms to first byte for Pāṇini, and about 300 ms for a full Sonex agent from the caller stopping to the agent starting. Sarvam reports that Bulbul V4 Flash delivers under 250 ms time to first audio in production, and doesn't publish an end-to-end response figure for its voice agents as of 24 October 2026. All of these are vendor-reported, and your network path will matter as much as the gap.

Neither vendor publishes a usable quality benchmark. Sarvam's launch post describes the V4 Flash voices as richer than V3 without MOS scores or method, and we don't publish a MOS or word-error-rate figure for Pāṇini or Valmiki either. Native listeners rating the same sentences from both, over a real phone line, will tell you more than any published score. You can start without an account: every language page, such as Bhojpuri, has a live playground under text to speech.

Cloning works on both. Ours takes a 10-second sample, the clone carries across languages, and one clone is included in the free tier. Sarvam's instant voice cloning is in beta, recommends a 10–15 second reference clip and can speak a language different from the clip's. For stock voices in a single major language, Sarvam offers more: its docs list over 200 persona voices for V4 Flash (its launch post counts 83, depending on how styles are counted), against our 120.

What does each cost once telephony and languages are included?

We charge $0.03125 per 1,000 characters for every one of our 250+ languages, or $0.028125 on the $5/month plan, so Bhojpuri and Garhwali cost the same as Hindi. As of 24 October 2026, Sarvam charges ₹3.00 per 1,000 characters for Bulbul V3, which at ₹96 to the dollar is exactly our rate. Sarvam is cheaper on Bulbul V4 Flash, at ₹2.00 on pay as you go, ₹1.85 on Pro and ₹1.70 on Growth and Business, about $0.021 per 1,000 characters; cloned voices are ₹2.00 on every plan. For that difference you get the dialects and non-Indian languages Bulbul doesn't offer at any price. Sarvam's plans cost ₹9,999 (Pro), ₹49,999 (Growth) and ₹1,99,999 (Business) a month, and its API page doesn't make clear how the fee offsets usage, so the tables use pay-as-you-go rates.

Speech recognition is close. We charge $0.00525 per minute of audio, billed by the second, so a 40-second call costs 40 seconds. Sarvam charges ₹0.49 per minute on pay as you go, about $0.0051, and ₹0.41 on Growth; its API page doesn't state its rounding, so compare on a week of your own traffic.

Voice agent prices include different things. Our $0.055 a minute ($0.050 on the monthly plan) includes speech to text, text to speech and telephony on Sonex numbers. If you bring your own telephony, no minute charge applies to it, and if you bring your own LLM key, the model is billed by your provider at zero markup from us. Sarvam's voice agents cost ₹3.50 a minute on pay as you go, ₹3.25 on Pro from 3,000 minutes, ₹3.15 on Growth from 16,000 and ₹3.00 on Business from 65,000, with the speech, language and voice models included. Calls on Sarvam's own telephony add ₹0.20 per 30-second pulse, a number costs ₹59 every 30 days, and agent minutes are billed in 60-second pulses rounded up per call. For the table we assume calls on each vendor's own numbers, one phone number, and Vyas as our model at an illustrative 12,000 input and 300 output tokens per call minute: about $0.0038 a minute on pay as you go ($0.30 and $0.60 per million tokens) and $0.0025 on the monthly plan ($0.20 and $0.40). Real token use depends on prompt length and turns.

On these assumptions Sarvam's agents cost about 28% less at 10,000 minutes and about a third less at 100,000, for agents that speak its listed languages. Short calls narrow the gap, since Sarvam rounds each call up to the minute and we bill recognition by the second. What the difference buys on our side is dialect and non-Indian coverage in the same agent and the choice of language model.

What does each agent platform include beyond the per-minute price?

Our platform capacity is 10,000 concurrent sessions; that is platform capacity rather than a figure for your account, so confirm your limit with us before a large campaign. Sarvam publishes per-plan concurrency on its voice agent pricing page, from 4 calls on pay as you go to 200 on Business, which makes capacity easier to plan from the page alone.

The language model is the biggest structural difference. We let you bring your own LLM key at zero markup, or use Vyas, our model with a 65,536-token context at $0.30 per million input and $0.60 per million output tokens, which matters if you've tuned prompts on a specific model or have a negotiated rate. Sarvam bundles the model into the per-minute price, and its voice agent pricing page doesn't say whether you can bring your own.

Around the call itself, Sonex agents can transfer a live call to a human agent, call your tools during the conversation, including over MCP, and connect to HubSpot, Salesforce, n8n, Zapier and Make. Calls can be recorded and transcribed, and outbound campaigns take calling windows, time zones and retry limits.

On telephony, our minute price includes Sonex numbers, and bring-your-own telephony carries no minute charge from us. Sarvam publishes a list of supported carriers (Exotel, Smartflo, Plivo, Twilio, Vobiz, InTalk and Pulse), with custom SIP on Business and Enterprise. Sarvam's Enterprise plan adds WhatsApp campaigns, custom tool authoring and forward-deployed engineering support, and its changelog added stereo call recordings and streaming voice cloning in October 2026.

When is Sonex Labs the better choice?

Choose Sonex Labs if your callers speak a dialect at home. A collections or loan-servicing campaign in Bihar reaches more people in Bhojpuri, Maithili or Angika than in standard Hindi; an agri-input or microfinance line in Rajasthan works better in Marwari or Mewari; a Haryana line can speak Haryanvi and a Chhattisgarh line Chhattisgarhi; an Uttarakhand rollout can speak Garhwali; and Bundeli, Braj and Bhili cover callers across northern, central and western India. Each is priced the same as Hindi.

Choose it if you run a support line in many languages and want one rate for all of them: Pāṇini covers 250+ languages and Valmiki 100+, on one bill. Choose it if your brand wants a cloned voice from a 10-second sample, or if you want about 300 ms agent response with telephony on Sonex numbers in the minute price. Choose it if your scripts mix Hindi and English, or your callers reach you from the Gulf, Egypt or North Africa as well as India. Choose it if your agents need to hand calls to a human agent, call your tools over MCP, connect to HubSpot or Salesforce, and run outbound campaigns inside calling windows with retry limits. Choose it if you want your own language model at zero markup, or your own telephony with no minute charge from us.

When is Sarvam the better choice?

Choose Sarvam if your callers speak the languages on Bulbul V4 Flash, the voices pass your listening test, and price per character or minute decides it: its V4 Flash rate and its agent minutes are both cheaper than ours. Choose it if you want the language model included in one rupee price, published per-plan concurrency, a speech recognition model that explicitly lists Bodo, Manipuri and Kashmiri, a long list of supported Indian carriers, or WhatsApp campaigns alongside the agent.

How should you test both before switching?

Run a short bake-off rather than trusting either vendor's page, ours included. Pick 30 to 50 sentences from your scripts, weighted toward what breaks: names, addresses, phone numbers, rupee amounts, dates and mixed-language lines. Generate each on Bulbul V4 Flash (or Bulbul V4 for Voice Agents) and on Pāṇini, and play them over the same phone line to native speakers who don't know which is which. Ask for a naturalness rating and any misheard word. Include your dialect sentences too, since that is where the two differ most.

For agents, put the same prompt behind both platforms and make at least 50 calls per language from real handsets. Measure the gap from caller stopping to agent starting at the caller's ear, including the slowest tenth of calls. Transcribe recorded calls on both and count errors on the entities your business depends on. Then price a full month of your real traffic on both, including the language model, telephony, rounding and every language you serve.