Concepts
Cayu is an open-source Python framework for building and running domain-specific long-horizon agents, with a durable runtime built in.
Your harness is the domain-specific system you assemble around the model: instructions, context, tools, policies, memory and verification. The integrated runtime executes that system and records its state. The resulting agent is your product for a defined job.
The framework and its components
Section titled “The framework and its components”| Term | Role |
|---|---|
| Framework | Cayu’s Python APIs, components and defaults for building and running agents |
| Harness | The domain-specific system assembled from those components |
| Runtime | The integrated execution subsystem for sessions, state, authority, workers, budgets and recovery |
| Agent | The resulting application that performs a defined job |
| Cloud | Optional deployment and shared operation of Cayu agents |
Use the framework for models and structured output, tools and integrations, context and memory, web/browser capabilities, multi-agent coordination, workspaces, verification and evals. The runtime executes those components within the stores, policies and execution boundaries you configure. See Build agents for implementation paths and the capability comparison for versioned public evidence.
Keep ownership clear
Section titled “Keep ownership clear”| Owner | Responsibility |
|---|---|
| Application | User interface, customer identity, business authorization, domain rules and completion criteria |
| Cayu runtime | Sessions, model/tool execution, recorded events, checkpoints, limits and configured recovery |
| Model provider | Model inference and provider-specific capabilities |
| Downstream service | Its actual external effect and idempotency/receipt contract |
| Human or policy authority | The decision that authorizes a consequential action |
The operator dashboard exposes runtime state; your application owns the customer experience. Cayu Cloud is an optional operating workspace.
Learn in order
Section titled “Learn in order”Start with the execution model, then sessions and runs, durability and authority. The runtime learning path teaches these through concrete examples and checks your understanding.
When you need exact fields, use Python reference. When you need an implementation path, use Build agents.