Decagon vs Sierra: Pricing, Resolution Billing and Which One Fits (2026)

Decagon and Sierra both price by the conversation or its outcome rather than by the minute, and neither publishes a rate card. That shared choice drives most of the difference between them and a per-minute platform, and most of the questions to ask before you sign. Here is how each one prices, what each counts as a billable unit, and when a per-minute platform is the better fit.

Retell AI publishes this comparison and is one of the options compared. Every Sierra and Decagon fact below comes from that vendor's own website, product pages, blog or trust center, checked in October 2026, and where a vendor does not publish something we say so. We did not benchmark or score the platforms, so each section ends with who each one fits rather than a winner.

At first glance, Sierra and Decagon look like siblings. They are not the same size any more. Sierra announced in May 2026 that it was raising $950 million, led by Tiger Global and GV, at a valuation of over $15 billion, and it reported over $150 million in ARR in February 2026. Decagon announced a $250 million Series D in January 2026, led by Coatue Management and Index Ventures, tripling its valuation to $4.5 billion. Both sell to enterprise customer experience teams, and neither publishes a public price. Pick the wrong one and you are not out a few hundred dollars in trial credits. You are out a contract term and an implementation cycle.

This comparison is not another feature grid. It covers setup, voice, pricing models, conversation design, integrations and compliance, using what each vendor publishes. We also included Retell AI as a third reference point. Retell is an AI voice agent platform for automating phone calls, and it sits in a different commercial category: published per-minute pricing, self-serve signup, and agents your own team configures instead of a managed implementation. Teams that need phone volume handled this quarter, and that want to own the configuration, should have it on the shortlist from the start, especially if they are already comparing voice automation tools.

Quick Answer: Who Should Pick What

Retell AI fits teams whose main channel is the phone and who want to build and run the agent themselves. Retell voice agents are priced from $0.07 per minute, with no platform fees and no minimums or contracts, and new accounts start with $10 in free credits. Retell's BAA is available for self-signing, so a HIPAA workload does not wait on a contract negotiation. Retell AI publishes its rates on its pricing page, so you can price the configuration you actually build before you talk to anyone.

Sierra fits large consumer brands that want one branded agent across channels, with governance at the center and the patience for a sales-led, partner-style engagement. Sierra's strengths are brand voice, governance and enterprise reach. It says it works with 40% of the Fortune 50 and names ADT, Chime, Cigna, Next, Nordstrom, Nubank, Minted, Ramp, Rocket Mortgage, SiriusXM, Singtel and Wayfair among its brands.

Decagon fits teams whose support volume sits mostly in chat and email and who want to write workflows as Agent Operating Procedures (AOPs) in natural language. Decagon prices per conversation or per resolution and does not publish rates. Voice is newer than the chat and email backbone, but it is no longer an afterthought. Voice 2.0 in September 2025 added outbound calling and cross-channel memory, a March 2026 outbound release added branded calling identities, voicemail detection, redialing and Missions for campaign management, and Voice 3 in October 2026 runs on Decagon's own speech model, Chord, in 70+ languages.

Now the details.

1. Setup and Time to First Live Call

This matters because a rollout that drags past the pilot window is where enterprise AI projects stall, and the platform that ships sooner earns the renewal.

Sierra pairs its software with its own agent development team.

Sierra sells a "long-term partnership, priced by outcomes" and says its agent development team "has supported hundreds of deployments." Engineers can work in the Sierra Agent SDK, and CX teams can build and manage agents without code in Agent Studio.

Sierra publishes no pricing, and sierra.ai/pricing returned a 404 when checked in October 2026. Sierra describes its model as outcome-based pricing, covered in section 3.

Sierra's Ghostwriter builds agents from uploaded SOPs, raw transcripts or audio interviews with subject matter experts, or from a description of how you want the agent to behave, and Sierra's product page promises you can "Deploy in weeks." Assume weeks, not days, and assume a sales cycle in front of it.

Decagon puts workflow building in CX hands, but still starts with sales.

Decagon's Agent Operating Procedures let teams define agent behavior in natural language, the same way they would write SOPs for human agents. In March 2026 Decagon introduced Duet, an agent-building partner that generates AOPs from past customer interactions, flags gaps in AOPs and guardrails, and generates tests. Duet Autopilot then turns production signals into proposed agent updates, each staged for human review. If you last evaluated Decagon in 2025, the build experience has changed materially.

Decagon says its integrations work "with no custom code required" and that AOPs let CX teams build "without engineering or vendor bottlenecks." Rates are not published, and the site's call to action is a demo request rather than a self-serve signup.

Retell can go live the same day.

You sign up with $10 in free credits, pick the use-case template closest to your scenario, whether that is receptionists or lead qualification, adjust the prompt, attach a phone number, and test in the dashboard. There is no sales call, no SOW, and no implementation team required.

The no-code builder and the developer SDK sit in the same product, so a solo operator can prototype on Monday and an engineer can harden it with custom functions on Tuesday, whether the agent handles customer support or scheduling.

Who this matters for: Solo founders and mid-market ops teams. Enterprise buyers with a dedicated implementation budget care less about setup speed and more about governance.

Best for: Retell AI if you need a working agent this week without a contract. Decagon if your CX team wants to own natural-language workflows after a sales-led start. Sierra if you want a vendor team building alongside you and can plan in weeks.

2. Voice Quality and Latency

On phone calls, callers notice pauses and talk-over far more than chat users notice a slow reply. This comparison does not include latency figures, because we did not benchmark the three platforms and vendor-reported numbers are not comparable. Judge voice quality on your own test calls, not on any vendor's adjectives.

Sierra launched voice in October 2024 as an extension of its digital platform.

Sierra Voice AI handles inbound and outbound calls in over 55 languages, can collect card and ACH payments over the phone with no IVR handoff, and is validated with voice simulations before launch, according to its voice page. In a Casper customer story on Sierra's site, Casper's VP of Operations says its AI agent gives the company 24/7 availability in any language, which it could not offer before.

A year after launch, Sierra said it handles more phone calls than chats. In August 2026 it shipped Voice Personas, which lets an agent adjust pacing, respond to interruptions and switch voices or languages mid-conversation, powered by a constellation of voice models chosen per persona, language and use case. Sierra is a genuine voice competitor now, not a chat platform with a phone bolt-on. The real difference is the commercial model and who can get their hands on it.

Decagon Voice is on its third version.

Voice 2.0 in September 2025 added outbound calling and cross-channel memory, and a March 2026 outbound release added branded calling identities, voicemail detection, redialing at set cadences and Missions for managing campaigns. Voice 3, announced in October 2026, speaks through Chord, a speech model trained by Decagon Labs, in 70+ languages. Voice connects through Amazon Connect, RingCentral and SIP trunking.

Decagon describes chat, voice and email as one "single intelligence layer," so voice shares the same AOPs and integrations as text. For companies whose support volume is primarily text, that makes voice a natural extension. For phone-first operations, test it on your own call mix.

Retell is voice-first by design.

Retell agents run on a choice of voice providers: Retell's platform voices, MiniMax, Cartesia, Inworld, Fish Audio, ElevenLabs and OpenAI. You can configure fallback voices so an agent keeps speaking during a TTS provider outage, and choose GPT, Claude or Gemini models or connect your own LLM.

Who this matters for: Any team where inbound phone is the primary channel. Sierra's and Decagon's voice layers are credible for brands that do mixed-channel CX. For voice-first deployments like healthcare scheduling, insurance intake, or EV support, run the same test calls on every platform you shortlist and compare what you hear.

Best for: Sierra if you need many languages and phone payments inside one branded agent. Decagon if voice extends an existing Decagon chat and email deployment. Retell AI if you want to choose and swap the voice, speech and LLM providers yourself.

3. Pricing: What Each Vendor Publishes and How Each Bills

Sierra and Decagon do not bill per minute and do not publish rates, so an honest annual cost model is not possible from public information. What each vendor does publish is how it bills, and that shapes your contract more than any estimate. decagon.ai/pricing, like sierra.ai/pricing, returned a 404 when checked in October 2026.

Outcome pricing deserves harder scrutiny than it usually gets. Sierra bills on outcomes against criteria agreed upfront, and says that when a conversation is unresolved or escalated, in most cases there is no charge. Sierra also offers a blended approach, such as consumption pricing for routing or greeter-style interactions. That sounds risk free until you succeed: the better your agent gets, the more you pay, and the definition of an outcome is a commercial negotiation rather than a technical fact. Decagon makes a similar point about its own category. It offers both per-conversation and per-resolution pricing and says the majority of its customers choose per-conversation pricing, partly to avoid arguing over what counts as a successful outcome. Per-minute pricing has a different shape. Your unit cost does not climb because the agent got good, and a finance team can model it in a spreadsheet before signing. Run a low-cost pilot first and let the volume data, not an outcome definition, set the contract. Retell publishes its pricing, so you can do that math before a sales call.

The costs worth asking about: how Sierra's contract defines each outcome and what "in most cases" excludes, how Decagon's per-conversation rate behaves during volume spikes such as Black Friday or a product launch, and what implementation work each vendor bills separately. Retell's extras are published: Retell phone numbers are $2 per month, concurrency beyond the 20 free concurrent calls is $8 per concurrent call per month, and knowledge bases beyond the first 10 are $8 per month each, plus $0.005 per minute when an agent uses a knowledge base.

Who this matters for: Pilot buyers who need a price before a sales call can only get one from Retell, the one of the three with published rates. Mid-market teams should evaluate Decagon if they are chat-heavy. Enterprise buyers with dedicated CX budgets and outcome-based ROI models should include all three.

Best for: Sierra if you want to pay on outcomes and can negotiate the definitions. Decagon if you want a choice between per-conversation and per-resolution billing. Retell AI if your finance team needs to forecast cost from a published rate.

4. Conversation Design and Flexibility

Sierra gives developers the Agent SDK and CX teams Agent Studio.

The Agent SDK is where engineers build agent logic in code, and Sierra's August 2026 Voice Personas release added SDK controls for pacing, interruptions and mid-call voice or language switching. Agent Studio is where CX teams build journeys, connect knowledge and set branding without code, and Sierra's Experiments feature runs multivariate tests on conversation design.

Agent Studio gives CX teams no-code control over journeys, knowledge management, 40+ pre-built integrations configurable inside Studio, and Simulations for regression testing. Ghostwriter adds a prompt-based way to build or modify agents. The remaining dependency is commercial rather than technical: you reach those tools through an enterprise contract, not a signup form.

Decagon's AOPs are the center of its product.

Agent Operating Procedures let a non-technical support manager write "if a customer asks for a refund over $100, verify their purchase date and escalate to billing," and the agent follows that as a workflow. AOPs are the capability Decagon leads with, and Duet now generates, tests and refines them from real conversations. The caveat is that writing good AOPs is real work: operations with undocumented logic have to document it first.

Around the AOPs, Watchtower reviews every conversation against criteria you define in natural language, and technical teams can version AOPs with Git-based tracking.

Retell runs a drag-and-drop conversational flow builder on top of full developer access.

Warm call transfer that briefs the person taking the call, calendar connections to Cal.com and Calendly to book appointments, and a knowledge base that can re-crawl your website every 24 hours are part of the platform.

All three platforms now ship simulation testing. Sierra runs Simulations and Voice Sims in Agent Studio and tests Voice Personas against thousands of simulated interactions before deployment. Decagon's Simulations are its integrated testing suite, with tests that Duet can generate. The difference is access, not existence: Retell's simulation testing is available on the self-serve pay-as-you-go plan, billed at the same rates as production calls, while Sierra's and Decagon's sit behind an enterprise contract.

One caveat on Retell: an agent sounds only as natural as its prompt, so expect prompt tuning, and non-technical teams can hit a learning curve when they move beyond basic scripts into multi-step call flows with fallbacks.

Who this matters for: CX teams that iterate weekly on agent logic should evaluate Decagon's AOPs seriously. Teams that need brand-heavy, deeply governed conversations default to Sierra. Teams iterating on voice that want to test before a sales call can use Retell's simulation testing on the self-serve plan.

Best for: Decagon for natural-language workflow control in chat and email. Sierra for governed, brand-heavy agents built with a vendor team. Retell AI for a visual flow builder and code access in one self-serve product.

5. Integrations and Developer Experience

Sierra integrates deeply, through its own framework.

Sierra's Agent Studio lists 40+ pre-built integrations to third-party knowledge bases, systems of record and contact centers, plus an integration framework for custom connections to proprietary systems, configurable directly in Agent Studio.

For human agents, Sierra sells Live Assist, which suggests real-time responses drawn from the operating procedures and knowledge bases your care representatives are trained on, and lets representatives take action with the same tools that power the AI agent.

Decagon has prebuilt help desk and CPaaS connectors, plus Decagon Assist for human reps.

Decagon's integrations page names Salesforce, Intercom and Zendesk for tickets and customer data, Confluence, Contentful and Kustomer for knowledge, and Amazon Connect and RingCentral for voice, plus SIP trunking, MCP and self-serve APIs for anything else.

Decagon Assist gives human agents automated summaries, suggested responses and in-tool actions, and Decagon says it works inside the systems teams already use, including Salesforce, Zendesk and Front. If help for human reps matters more than an autonomous agent, our Cresta alternatives comparison covers vendors built around agent assist.

Retell connects its integrations from the dashboard.

Retell's integrations cover CRMs including HubSpot, Salesforce, Microsoft Dynamics 365, GoHighLevel and Zoho CRM, Zendesk for support tickets, Google Drive, Microsoft OneDrive and Notion for knowledge bases, and Calendly, Cal.com and GoHighLevel for scheduling. You connect a provider once on the Integrations page, and every agent in the workspace can use its tools.

Telephony options include Retell numbers, Twilio, Telnyx and Vonage over SIP trunking, any other carrier through custom SIP trunking, and a web SDK for browser-based voice that requires no telephony at all. Developers also get custom functions and webhooks for everything else.

Who this matters for: Teams on HubSpot, Salesforce, Zendesk or GoHighLevel can connect Retell from the dashboard without a services engagement. Teams that want AI help for human reps inside Salesforce or Zendesk should look at Decagon Assist or Sierra Live Assist. Teams with legacy contact centers (Avaya, Genesys) should ask each vendor how the connection is built and who pays for that work.

Best for: Sierra for 40+ pre-built integrations and a vendor team for custom ones. Decagon for help desk and CPaaS connectors plus agent assist. Retell AI for self-serve CRM, help desk and telephony connections.

6. Compliance, Security, and Support

Sierra is built for regulated enterprise from day one.

Sierra's trust page lists SOC 2, HIPAA, GDPR, PCI, FedRAMP High, CCPA, CSA STAR, ISO 27001 and ISO 42001, and Sierra holds PCI DSS Level 1 Service Provider certification for payments. Personal information shared with the agent is automatically encrypted and masked. Sierra wraps its constellation of LLMs in supervisory layers to reduce hallucinations and switches between LLM providers if one has an outage.

Support is a partnership: Sierra says it keeps optimizing an agent's performance after deployment, and ties that work to its outcome-based model. The cost of that service sits inside an enterprise contract rather than a self-serve plan.

Decagon ships enterprise-grade compliance with usage-based access.

Decagon's security page shows SOC 2 Type 2, HIPAA, ISO 27001, GDPR, PCI and CCPA badges, and describes zero-data retention with AI providers such as OpenAI and Anthropic, automatic redaction of sensitive data, and a built-in supervisor that checks responses for hallucinations. Watchtower reviews every conversation against your criteria, and AOPs keep workflow logic readable in natural language.

Decagon said in its January 2026 funding announcement that more than 100 new global enterprise customers, including Avis Budget Group, Block and Deutsche Telekom, joined in its latest fiscal year.

Retell offers a self-signable BAA.

If you work in healthcare, financial services, or insurance, Retell's BAA and DPA are available for self-signing, without procurement involvement. Pine Park Health, a senior care provider using Retell for appointment reminders and scheduling, reports a 38% increase in NPS related to its scheduling experience in its case study.

Who this matters for: Healthcare, finance, and insurance teams should weight compliance heavily. Sierra lists the longest set of certifications, including FedRAMP High and ISO 42001, Decagon matches on the core certifications, and Retell's self-signable BAA removes a legal back-and-forth before a HIPAA pilot.

Best for: Sierra for the broadest compliance list, including public sector work. Decagon for the core certifications with conversation-based billing. Retell AI for starting a HIPAA workload without a contract negotiation.

Decision Framework

If you are running inbound customer support by phone and your ops team needs to iterate on scripts without a vendor in the loop, Retell is the most direct fit, because you can sign up, build and test without a sales cycle. Sierra and Decagon both sell capable voice agents, but through a sales-led contract.

If you are running high-volume outbound campaigns like appointment reminders, surveys, and lead follow-up, Retell handles most use cases cleanly because batch call functionality and outbound AI telemarketing are built into the core platform. Decagon's outbound voice, with Missions for campaigns, is worth piloting if you already run your chat and email on Decagon, and Sierra also supports outbound calls.

If you are a large consumer brand where the AI agent's tone, governance, and cross-channel consistency are brand-critical, Sierra is the default. You are buying a partnership with Sierra's agent development team, and an outcome-based contract is the price of that model.

If you are in a regulated industry like healthcare, finance, or insurance, Retell's self-signable BAA lets you start without a contract negotiation. Matic Insurance handled 8,000+ calls with AI on Retell in Q1 2025, and its average data-collection time dropped from 9 minutes to about 6, according to its case study.

If you are an agency managing voice agents for multiple clients, Retell is the one of the three where you can stand up a dedicated agent per client in minutes without a sales cycle. Sierra and Decagon both start with a sales conversation and unpublished pricing, which is hard to repeat for every small client.

If you are a mid-market support team whose volume is mostly chat and email with some voice, Decagon's AOPs were built for exactly that mix. The tradeoff is unpublished pricing and a sales-led start, which you are accepting for AOP-level control.

The Bottom Line

Sierra and Decagon are both legitimate platforms for the enterprise buyers they target. Sierra is the right answer for large consumer brands with deep CX budgets and a mandate to make the AI agent sound like the brand. Decagon is the right answer for tech companies doing primarily chat and email support who want natural-language workflow control. Both teams have built real products with real customers, and both will continue to win deals in their respective niches.

For teams whose volume is mostly phone calls, Retell AI is the option you can price and test before signing anything: published rates from $0.07 per minute, self-serve signup with $10 in free credits, and a self-signable BAA. The strongest test is to build the same basic agent on two platforms using free credits where available, run 20 real test calls, and see which one your team actually wants to keep using a week later.