Compare Lab
Hume AI vs Synthflow
Hume AI is positioned as hume TTS and EVI API sunset: announced access end November 13, 2026 at 05:01 UTC. Retained for historical comparison and migration research. Synthflow is positioned as a visual voice-agent workflow platfor
Hume AI is positioned as hume TTS and EVI API sunset: announced access end November 13, 2026 at 05:01 UTC. Retained for historical comparison and migration research. Synthflow is positioned as a visual voice-agent workflow platform sold through scoped deployments and partner delivery. Start by deciding who owns the missing layers, then inspect the documented differences below.
Voice Engines and Full Platforms are different product categories. An underlying engine or framework is not a complete substitute for a deployed agent workflow.
14 jointly documented catalog fields. This measures evidence coverage, not equivalent quality or an overall winner.
TTS + EVI API sunset · Announced end: 13 Nov 2026, 05:01 UTC. Read notice & sources →
Test opening hours, booking conflicts and an unanswered transfer.
Start where the records differ.
Values and evidence states are compared together. Shared facts follow the differences; Unknown never means No.
| Decision point | Hume AI | Synthflow |
|---|---|---|
| Billing modelDifferent records | monthly-bundle | custom-sales-led |
| Billing unitDifferent records | Monthly subscription + EVI minutes / TTS characters / supplemental LLM usage | Contract minimum per year; call seconds aggregate to minutes; five AI chat messages count as one usage minute |
| Bring your telephonyDifferent records | Yes | Yes |
| Bring your modelDifferent records | Yes | Yes |
| Warm transferDifferent records | Unknown | Yes |
| HIPAA pathShared state | Yes | Yes |
Your requirements & next steps
Your requirements
Ready-made / AI receptionist · Strict evidence mode
No personal requirements yet. Add criteria in Advanced Filter to prioritize this comparison.
Subscription includes TTS/EVI/Voice allowances; overage and managed external LLM usage add cost.
Sales-ledcontract;call usage metered but exact unitrates and allowances negotiated.
Free plan exists; paid entry is not a complete phone-call bill.
Starting commitment; complete contract cost remains unknown.
Incompatible product allowances are not collapsed into one all-in minute price.
Rates,allowances andsimulationbilling come fromaccountagreement.
First-month Creator promotion is separate from regular price; Enterprise custom.
No complete current public contract rate and allowance schedule was established.
Plan-scoped EVI allowance; does not include every third-party carrier/model charge.
No complete current public contract rate and allowance schedule was established.
TTS characters, EVI minutes and supplemental model usage remain separate.
No complete current public contract rate and allowance schedule was established.
Reviewed current public offer; retain original billing scope and units.
Not yet researched against this buyer-critical field standard.
No complete current public contract rate and allowance schedule was established.
No complete current public contract rate and allowance schedule was established.
Research conclusion about cost completeness, not a vendor capability.
Anyone with this link can view the encoded decision criteria.
Vendor documentation establishes a claim. Public model benchmarks are separate context, not measurements of these platforms.
Open saved comparison ↗What to verify together.
Hume AI
VoiceAgent.best recommends evaluating migration options rather than starting a new long-term TTS or EVI API deployment. This is our editorial judgment; replacement compatibility has not been established.
$3/month Starter; included EVI minutes and overage depend on plan · V3.3 evidence review · Starter subscription reference; EVI 40 minutes; external LLM/telephony extra
Excluded / confirm: Complete cost cannot be established from this reference. Selected external LLM, carrier, token/character consumption and overages prevent a complete cost ceiling from monthly minutes alone. · Hume-managed external LLM usage extra; BYO key/custom model paid outside Hume; Twilio separate
Subscription includes TTS/EVI/Voice allowances; overage and managed external LLM usage add cost.
Synthflow
Do not apply old self-service rates to a new contract.
Enterprise contracts from $30,000 annually · V3.3 evidence review · Enterprise contract starting annual commitment; scoped quote required
Excluded / confirm: Complete cost cannot be established from this reference. No complete current public contract rate and allowance schedule was established. · Account agreement and carrier/add-on terms require quote
Sales-ledcontract;call usage metered but exact unitrates and allowances negotiated.
The evidence overlap.
Both records have documented values for Product type, Call direction, Technical setup, Pricing model, Twilio, OpenAI models, Interruption controls, Silence handling, Transcripts, Zapier, Webhooks, Official product documentation and additional fields shown in Compare. Matching availability does not measure behavior under your call conditions.
Run the same booking, tool failure and unsuccessful human-transfer cases. Record both outcomes and billable units before signing a deployment agreement.
Review Hume API sunset & migration guidance →