> For the complete documentation index, see [llms.txt](https://docs.zenml.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zenml.io/kitaru/core-concepts.md). # Core Concepts - [Overview](https://docs.zenml.io/kitaru/core-concepts/concepts.md): A handful of nouns and one verb, and how sessions, replays, evaluators, cohorts, experiments, investigations, and workers fit together. - [Agents & Sessions](https://docs.zenml.io/kitaru/core-concepts/agents-and-sessions.md): The agent is the identity, the session is the recording of every model call, tool call, and decision a run left behind. - [Investigations & Annotations](https://docs.zenml.io/kitaru/core-concepts/investigations.md): Where your judgment enters the system: your coding assistant maps the evidence, interviews you in context, and pins your answers to exact trace evidence as annotations. - [Replay](https://docs.zenml.io/kitaru/core-concepts/replay.md): Re-run a recorded session against your real code, unchanged for a faithful baseline or forked with one thing different. - [Evaluators & Evaluations](https://docs.zenml.io/kitaru/core-concepts/evaluators.md): Evaluators turn sessions into evaluations: the rows they write. Numbers average, words count, free text gets read. - [Analyzers & Insights](https://docs.zenml.io/kitaru/core-concepts/analyzers.md): Analyzers turn many sessions into insights: the aggregate read a single evaluator can't give you. - [Cohorts](https://docs.zenml.io/kitaru/core-concepts/cohorts.md): Named, versioned sets of sessions; the population an experiment replays, frozen so results stay comparable. - [Experiments](https://docs.zenml.io/kitaru/core-concepts/experiments.md): A named change, replayed across a cohort and evaluated. What improved, what regressed, before you ship. - [Workers](https://docs.zenml.io/kitaru/core-concepts/workers.md): The process that runs replays, imports, and evaluators as subprocesses in your environment, so your code and data never leave your systems. - [Under the Hood](https://docs.zenml.io/kitaru/core-concepts/under-the-hood.md): The machinery behind the loop: a FastAPI server on Postgres, workers claiming tasks, and where Kitaru sits beside your observability stack. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://docs.zenml.io/kitaru/core-concepts.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.