Sierra rebuilds Agent Studio around Ghostwriter, its agent for building agents

Ghostwriter follows you through Agent Studio

Sierra describes Ghostwriter as an always-on teammate that helps build agents, understands how they are performing, suggests improvements in Slack and Teams, and pushes live whatever a user approves. Agent Studio is the shared place where that work happens: investigating problems, working on improvements, testing changes and deciding what ships.

Until now, according to Sierra, that meant moving between the separate parts of Agent Studio used to edit journeys, run simulations and review performance. In the redesign, Ghostwriter stays with the user throughout and sees what they are looking at, whether that is a journey, a simulation or a dashboard. If something looks wrong, a user can ask about it or have Ghostwriter fix it directly, without explaining the context first.

Ghostwriter also combines what used to be spread across Explorer, Sierra Assistant and other specialized agents. Sierra says users no longer need to know which tool does what.

Sessions and multi-agent projects

Each piece of work now runs in its own session. Sierra compares this to a chat thread in ChatGPT or Claude: the conversation with Ghostwriter is kept together with the changes it makes. Those changes stay in the session until someone reviews and merges them. A team can investigate why more customers are asking for a support associate in one session and build a new journey in another, without the two interfering.

Sessions are also meant to help collaboration. Users can share a session to work through a problem together, or fork one to pick up where a colleague left off. Before a merge, they can ask Ghostwriter to review a teammate's changes.

Agent Studio now also groups related agents into a single project, together with the data and channels they share, so they can be tested and released together. Sierra gives the example of a lender. One agent collects documents from applicants, and another manages the application and follows up until the loan closes. When the lender adds a new document requirement, Ghostwriter updates what the first agent asks for and how the second follows up, all in one session.

Review and release controls

Sierra says that as Ghostwriter does more of the editing, reviewing its work matters more. The redesign includes several tools for that:

• Line-by-line comparisons that show exactly what changed.
• Preview Chat and Simulations to test behavior before a merge.
• Release governance with required approvals and controlled rollouts, so nothing reaches customers until the team approves it.

The evidence, changes and test results stay together for the team to review before anything goes live.

What it means for teams building agents

Sierra frames the change as part of a broader shift in how software gets made. The company says that a year ago almost all code was written by engineers, and that today few tech companies write more than five percent of their code by hand. In its view, agent building is following the same path, from code to clicks to prompts.

For teams using Sierra, the practical effect described in the announcement is fewer tool switches and a single record of an investigation, a change and its tests, with human approval kept in place before release. The company's stated aim is that Ghostwriter keeps finding ways to improve agents while Agent Studio keeps the team in control of every change.