Parlant vs Sierra
Parlant vs Sierra
Sierra is a customer-experience platform. Your team builds the agent on it, in the no-code Agent Studio or in code with the Agent SDK, often working with Sierra's own team, and Sierra runs it.
With Parlant, you build the agent yourself by describing it to your coding agent. The agent's code and the open-source engine it runs on are yours, and you choose its models and where it runs. Your coding agent does most of the work, so a change takes as long as describing it and testing the result.
Which one fits depends on what matters most to you. If you want a vendor team to deliver and look after the agent, Sierra fits. If you want to change the agent yourself, go beyond any platform's options, choose your models and hosting, and pay your model provider instead of a fee per outcome, Parlant fits, as long as someone on your team is comfortable working with a coding agent.
- What each option suits best, depending on what you're optimizing for
- What you can change in Parlant that Sierra's tools don't reach
- What you own with each, and what you could take with you
- Who changes the agent after launch, and how changes get tested
- What you take on in running cost and operations
These are the questions CX teams usually ask when weighing the two:
Sierra builds the agent with us. Why would we build our own?
Sierra brings together voice, chat, email, and WhatsApp, business-system integrations, testing, and monitoring. Its agent development team helps customers build and improve their agents. That's a strong fit when you'd rather a delivery partner take on the implementation with you.
Parlant makes sense when you want the agent to be yours. You describe its policies and procedures and the systems it should use, and your coding agent builds them, following docs written for it. You don't need an engineering department or an outside team for that. Parlant supplies a tested design for customer conversations, including optional checks on the agent's actions and replies.
What you gain is speed of change and control. You don't wait for a delivery cycle: you describe what you want, and your coding agent writes the policies, connects your systems, and runs test conversations. Parlant already provides the engine that keeps the agent on your rules, the chat widget, handoff to your team, analytics, and hosting, so nothing has to be built from scratch. You can change any part yourself: a connection, the model for each job, the exact way a sensitive situation is handled. What you take on is ownership: someone on your team checks what the coding agent builds and looks after the agent.
Sierra has Agent Studio and an Agent SDK. What more can we change in Parlant?
Sierra supports both business teams and engineers. Agent Studio gives business teams tools for building journeys, versioning changes, and configuring integrations. The Agent SDK lets developers build agents in code, in Sierra's declarative language, with version control, continuous integration, and releases they can roll back. So with Sierra, too, your agent can live in code and go through your development process.
The difference is what that code runs on. Sierra's SDK builds agents for Sierra's platform, which runs them on its own engine and its choice of models. In Parlant, the engine is open source and part of your project. Besides the agent itself, you can choose the model for each job, change how carefully it checks a sensitive reply, change how it stores customer data, or replace parts of the engine. The agent can use any system your code can reach, with your own sign-in and access rules.
If the changes you need fit Sierra's tools, that difference matters less. If you expect requirements that go beyond configuring an agent, it matters a lot.
What do we own, and what could we take with us?
With Parlant, your agent's code lives in your own Git repository: its policies, tools, connections, and configuration. The engine is open source under Apache 2.0, so you can run, change, and host it anywhere, with no usage limits. Two parts are not open source:
- The Dashboard is a paid service for testing, managed hosting, and monitoring. Your agent doesn't depend on it: you can self-host without it, and take on the hosting and monitoring yourself.
- Compass Pro is a commercially licensed set of engine plugins, including the built-in voice interface. If your agent uses it, you need that license to run it.
Sierra's public material doesn't say whether an agent built on it can be exported or run elsewhere. Ask what you could take with you if you left: the agent's definition, your SDK code, and your conversation history.
Who changes the agent after launch, and how do we test a change?
Sierra's platform has testing built in. It can turn real conversations into tests that run as simulations before each release, and releases are versioned, so a change can be rolled back. Changes go through Sierra's tools and, where you've arranged it, its team. Ask how a typical change is requested, tested, and released, and how long it takes.
With Parlant, you describe the change to your coding agent: a new rule, a different answer for a situation, an exception. Then you test it in the Dashboard with a simulation, a test conversation with your real agent where you play the customer. Your coding agent can run the test conversations too, and tell you what happened. When you're happy, it goes live with your next deployment, and Git keeps every earlier version. The same person who knows how the conversation should go can make and check the change, often in minutes.
If the agent promises a refund it hasn't issued, how do we find out why?
Sierra includes testing and automated monitoring, so visibility is already part of its offer. Ask to follow a failed refund through its tools: what the agent attempted, what the system returned, and why the customer received that reply.
In Parlant, you can turn on a reply check for situations like refunds. It compares the drafted reply with your instructions and with what actually happened, and has the agent write it again if they don't match. The check is itself a model, so it makes a wrong promise much less likely rather than impossible. When something still surprises you, Parlant's diagnostics show which rules applied, which actions ran, and what each check decided.
Both give you a way to investigate. Parlant's difference is that you can also change the mechanism you're investigating. Whether either gives better results for your refund policy needs a test with the same conversations and failure cases on both sides.
What would it cost, and who runs it?
Sierra uses outcome-based pricing: you pay for results such as resolved conversations, at rates agreed in your contract. Its prices aren't public, so we can't put a number on the difference here.
With Parlant, the engine is free, you pay your model provider directly with no markup, and the Dashboard is a flat monthly fee per workspace, free for development; see pricing. The worked example against Intercom Fin shows how flat pricing compares with paying per outcome at published rates.
Running cost isn't the whole cost. With Parlant, someone on your team owns the agent and its connections, with the coding agent doing the building. The Dashboard can run your agent with managed hosting, so you don't run servers; if you self-host, your team runs those too. Extra checks on replies add model work and response time on the conversations where you turn them on, and the built-in voice interface needs Compass Pro.
To compare, put an actual Sierra proposal next to Parlant's model usage, Dashboard plan, any Compass Pro license, and the time of the person who looks after the agent.
How do we compare them on our own service?
Choose one service procedure and build it in a Parlant test project, with your coding agent. Ask Sierra to demonstrate the same procedure with equivalent requirements. Include a customer who changes their request, a policy exception, and a refund that fails. Look at what each agent did as well as what it said.
Then change an approval rule. Note who can make the change, how it's tested and released, and how you'd find the cause if something broke. Compare correct outcomes, response time, total cost, and the effort to maintain it.
If you want to change the agent yourself and keep control of how it works, where it runs, and what it costs, Parlant is built for that. If you'd rather a vendor and delivery partner build and run it for you, Sierra is.
Comparison as of October 2026, based on Sierra's public product pages and blog. The capabilities described here are not a measured reliability ranking.