Sierra
Also known as: Sierra AI
Enterprise agent platform whose agents are composed from skills into workflows with tunable determinism, deployed once across chat, phone, email, SMS and messaging, running on a supervised constellation of models and executing end-to-end transactions inside the customer's systems of record.
Sierra is an enterprise conversational AI platform that builds branded, autonomous customer-experience agents. It was founded in 2023 by Bret Taylor (former co-CEO of Salesforce and current chair of OpenAI's board) and Clay Bavor, who previously led Google Labs and Google's VR efforts. The San Francisco company crossed $100M in ARR in under two years (reportedly $150M+ by early 2026) and counts more than 40% of the Fortune 50 among its customers, including Prudential, Cigna, Blue Cross Blue Shield, and Rocket Mortgage.
The platform, branded Agent OS, lets companies build, test, deploy, and continuously improve AI agents that operate across chat, voice, email, SMS, and WhatsApp in 30+ languages. Its model-agnostic 'constellation' architecture orchestrates multiple LLMs (OpenAI, Anthropic, Google, Meta) per task, with Sierra rather than the customer choosing the models.
Agent OS 2.0 spans roughly eight products, including Agent Studio for configuration (with no-code Journeys, Workspaces, and an Integration Library), an Agent Data Platform for persistent memory and context, and Live Assist for human escalation. Sierra is a Level 1 PCI-compliant conversational AI platform, so its agents can complete end-to-end commercial transactions (collections, renewals, and purchases), not just resolve support tickets.
In March 2026 Sierra launched Ghostwriter, an 'agent that builds agents': a business user describes what they need in plain English, or uploads SOPs, transcripts, and recordings, and Ghostwriter generates a production-ready agent, lowering the barrier to deployment for non-technical teams. Sierra prices on outcomes, charging only when an agent resolves an issue, saves a cancellation, or completes an upsell. It has raised over $1.58 billion total, most recently a $950 million Series E (May 2026) led by Tiger Global and GV at a $15.8 billion valuation.
Vendor details
Canonical URL
https://sierra.ai
Category
Customer support agent
Subcategory
Enterprise conversational AI / customer experience agent platform
Funding status
Sierra has raised $1.58B+ over 4 rounds. Its $950M Series E (May 2026) was led by Tiger Global and GV (Google Ventures) at a $15.8B post-money valuation, following $350M at $10B (Sept 2025) and $175M at $4.5B (Oct 2024). ARR is reported at $150M+, and Sierra crossed $100M ARR in under two years. It has about 165 employees.
Company status
independent
Use cases & customers
Primary use cases
Target customers
Deployment options
Integrations
Sierra's model-agnostic 'constellation' architecture orchestrates multiple LLMs (OpenAI, Anthropic, Google, Meta) per task, with Sierra rather than the customer choosing the models. Agents operate across chat, voice, email, SMS, and WhatsApp in 30+ languages, with native contact-center integration and distribution through ChatGPT. A declarative Agent SDK plus Agent Studio's Integration Library connect to enterprise systems, and the platform is Level 1 PCI-compliant, enabling end-to-end commercial transactions.
In practice
Your support agent can answer questions but can't actually complete a transaction. Sierra is PCI Level 1 compliant, so its agents handle collections, renewals, and purchases end to end, not just tickets.
Building a production agent usually needs engineers. Sierra's Ghostwriter takes a plain-English description or your SOPs and transcripts and generates a production-ready agent.
You'd rather pay for results than software seats. Sierra prices on outcomes, charging when an agent resolves an issue, saves a cancellation, or completes an upsell.
Sources & related URLs
Agentic Index coverage score
11.5 / 14 capabilities · 82%
| Integrations & Tool Calling | Full |
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Agents reach the customer's systems of record through integrations built on the Agent SDK, executing end-to-end transactions including card and ACH payments, returns, authentication and cancellation saves. Those system interactions are held deterministic and policy-bound. Integrations are engineered through the SDK rather than drawn from a published connector catalog, so breadth depends on the build. Sourcesierra.ai/product/agent-sdkread 2026-09-05 |
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| Workflow Orchestration | Full |
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Agents are composed by mixing and matching skills such as triage, respond and confirm into multi-step workflows executed for a specific use case. The degree of flexibility is set per workflow, so a customer dials between deterministic execution and open-ended reasoning on the same agent. Sourcesierra.ai/product/agent-sdkread 2026-09-05 |
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| Knowledge Grounding & RAG | Full |
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Agents ground on the customer's own content through retrieval built into Agent OS. The Agent Data Platform unifies that knowledge alongside customer context across systems, so answers draw on a maintained store rather than a per-conversation fetch. The ingestion and indexing mechanism is not documented publicly, so the maintained store is an inference from the platform layer's stated role. Sourcesierra.ai/product/agent-sdkread 2026-09-05 |
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| Human Oversight & Guardrails | Full |
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Sierra wraps its models in supervisory layers that check outputs against scope and policy before the agent responds, to reduce hallucination and prevent abuse. Access to systems of record is deterministic and controlled, so the customer's policies and security procedures are enforced outside the model rather than trusted to it. Workflow-level flexibility settings bound how far the agent may improvise. Sourcesierra.ai/product/trust-and-reliabilityread 2026-09-05 |
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| Security, Identity & Governance | Full |
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Sierra publishes commitments to SOC 2, ISO 27001, ISO 42001, PCI, HIPAA, GDPR, CCPA, CSA STAR and FedRAMP High. A trust portal at trust.sierra.ai carries the specific controls and policies, with documentation available on request. Sierra also states that customer data is never used to train models and that access to systems of record is deterministic and policy-bound rather than left to the model. Sourcesierra.ai/product/trust-and-reliabilityread 2026-09-05 |
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| Observability & Auditability | Full |
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The platform lets a developer understand and adjust agent behavior by inspecting API calls and logic traces, so the path a conversation took through the agent's reasoning and tool calls can be reconstructed rather than only summarized. Review and optimization surfaces check for on-brand and expected behavior. Sourcesierra.ai/product/agent-sdkread 2026-09-05 |
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| Memory & State Persistence | Full |
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The Agent Data Platform is a named platform layer whose stated job is unifying what the agent knows about a specific customer across sessions, channels and systems. Context persists between conversations rather than being rebuilt per interaction. No scope or retention lifetime is published for that store. Sourcesierra.ai/product/agent-sdkread 2026-09-05 |
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| Deployment & Data Residency | Partial |
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Sierra is delivered as Sierra-hosted SaaS. Residency is published per subprocessor through the trust portal rather than offered as a region the customer selects, and no VPC, single-tenant or on-premises option is documented. The FedRAMP High commitment implies segregated government infrastructure, but no residency menu the buyer chooses from is stated. Sourcesierra.ai/product/trust-and-reliabilityread 2026-09-05 |
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| Prebuilt Agents, Templates & Packs | Partial |
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The Agent SDK ships with a range of AI skills and systems integrations so customers go live faster, and skills such as triage, respond and confirm are reusable building blocks. These are composable primitives the customer assembles rather than named prebuilt agents, templates or an adoptable catalog, and no library or marketplace is published. Sourcesierra.ai/product/agent-sdkread 2026-09-05 |
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| Triggers & Channel Coverage | Full |
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One agent is built once and deployed across chat, phone, email, SMS and messaging, with the same skills and policies applying on each. Sierra positions a single agent working across every channel as the platform's design point. Sourcesierra.ai/product/agent-sdkread 2026-09-05 |
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| Model Flexibility & Routing | Partial |
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Agents are assembled from more than fifteen frontier, open-weight and proprietary models chosen per job, and Sierra switches between LLM providers automatically to optimize performance and maintain continuity during a provider outage. Sierra states as a selling point that the customer does not hand-pick the models or wire them. The routing happens inside Sierra, and neither customers nor admins choose the model. Sourcesierra.ai/blog/constellation-of-modelsread 2026-09-05 |
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| APIs, SDKs & MCP Extensibility | Full |
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A published Agent SDK is the developer surface for building, customizing and deploying agents, backed by documentation, interactive training and a development pipeline. Agent OS exposes out-of-the-box tooling for how agents are built, deployed and managed. No public API reference or MCP server for the platform itself is documented, so the developer surface is an SDK rather than an open API contract. Sourcesierra.ai/product/agent-sdkread 2026-09-05 |
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| Testing, Debugging & Optimization | Full |
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The Agent SDK verifies that an agent performs as expected across a wide range of scenarios and guards against regressions. Agent definitions are carried through a development pipeline rather than edited live. The artifact under test is the customer's own agent, and the result gates the change. Sourcesierra.ai/product/agent-sdkread 2026-09-05 |
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| Browser & Computer Use | Not documented |
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Agents act on the customer's systems through SDK-built API integrations held deterministic and policy-bound, and deploy across chat, phone, email, SMS and messaging. No browser control, virtual desktop or operation of software lacking a programmatic interface is documented. Sourcesierra.ai/product/agent-sdkread 2026-09-05 |
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The Agentic Index coverage score grades every vendor Full, Partial or Not documented against the same 14 buyer facing capabilities, from public evidence only. Each capability links to how all vendors in the index score on it. How this evidence is graded
Recent platform changes
Sierra achieved AIUC-1 certification after an independent audit by Schellman and testing by the Artificial Intelligence Underwriting Company.
Bears on: Security / enterprise
View sourceSierra introduced Agency, a new infrastructure primitive that provides secure and scalable sandboxes for its AI agents. The Agency environment allows agents to execute long-running, complex tasks with dedicated computing resources, maintaining state and data isolation without interruption.
Bears on: Agent capability
View sourceSierra acquired the AI startup Takeoff and introduced the Horizon Agent Platform. This new offering focuses on long-horizon AI agents designed to execute end-to-end tasks across sectors like lending and healthcare, rather than being limited to single-turn customer support conversations.
Bears on: Agent capability
View sourcePricing
Outcome-based (per resolution) · contact sales
outcome-based (per resolution/outcome)
What is public
Sierra prices on outcomes: customers are charged only when an agent resolves an interaction, saves a cancellation, or completes an upsell, with no per-seat fees. Pricing is sales-led and not publicly listed. Third-party reports and procurement filings estimate effective costs of roughly $0.50 to $2.00 per resolved conversation, translating to six-figure annual commitments that generally exclude SMB and most mid-market buyers.
Variable cost rationale
Charged per successful outcome (resolution, saved cancellation, completed upsell), so total cost scales directly with resolved volume. Third-party estimates cite roughly $0.50 to $2.00 per resolved conversation.
Sales call required
Yes, required for paid access
Commercial notes
Founded 2023 by Bret Taylor and Clay Bavor. Reached $150M+ ARR by early 2026 and raised a $950M Series E (May 2026) at a $15.8B valuation. More than 40% of the Fortune 50 among its customers.
Key ambiguities
No public per-resolution or per-seat rate. Figures are third-party estimates and vary by scope.
Missing data
Sierra does not publish per-resolution or per-seat pricing. Estimates come from integration partners and procurement filings.
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Alternatives to Sierra
The closest documented capability profiles to Sierra among customer support agents tracked by Agentic Index, ordered by similarity on the same 14 point evidence the rankings use. No vendor pays for placement.
- ASAPP11.5 / 14Matches Sierra across all 14 documented capabilities
- Delight.ai11.5 / 14Fuller documented coverage on Deployment & Data Residency
- Five911.5 / 14Fuller documented coverage on Prebuilt Agents, Templates & Packs
- Quiq11.5 / 14Fuller documented coverage on Model Flexibility & Routing
- Ada11.0 / 14Fuller documented coverage on Prebuilt Agents, Templates & PacksSierra vs Ada →
- Bland AI12.0 / 14Fuller documented coverage on Deployment & Data Residency and Prebuilt Agents, Templates & Packs
Similarity is computed from each vendor's Agentic Index coverage score evidence, axis by axis, not from the totals. How this evidence is graded