Dagger is an open-source runtime and developer platform for building containerized, programmable workflows—most commonly used for CI/CD pipelines, test orchestration, and increasingly for agentic automation. Instead of expressing pipelines in YAML (e.g., GitHub Actions/GitLab CI), Dagger provides SDKs that allow pipeline logic to be expressed as code that executes in containers with reproducibility, caching, and portability across environments (laptop, CI runner, dedicated infrastructure).
Dagger Cloud is the commercial offering that provides centralized observability and collaboration features such as module sharing and extended run history. Dagger Cloud is not a general CI hosting service; it integrates with existing CI runners.
Primary use cases targeted by Dagger:
- Replace YAML plus shell scripting with pipeline logic expressed as code (typed APIs, refactoring, reuse)
- Make pipelines locally testable (reduce iterative push-based debugging)
- Improve repeatability through containerization and deterministic inputs
- Enable composability via reusable modules/functions (the Dagger ecosystem)
Primary sources reviewed include the official site and the GitHub README, which describe the open-source runtime and containerized composable workflows.