Concepts overview

The mental model behind kdeps: how a workflow is shaped, how data moves between steps, and which pieces apply to each mode. Start with the two modes, then reach for the rest as you need them.

The two modes

Concept	What it is	Mode
Workflow mode	A DAG of resources that runs in dependency order and returns a response	Workflow
Agent loop mode	An LLM that calls workflows, components, and built-in tools to finish a task	Agent
Agencies	Several agents bundled under one agency.yaml, calling each other with agent:	Both
Components	Reusable resource bundles you install or build, invoked with component:	Both

Wiring data between steps

Concept	What it is	Mode
Expressions	expr-lang snippets in , before:/after:, and check:	Both
Expression helpers	Json(), Safe(), Debug(), default() and other utilities	Both
Data access	get()/set() plus the input and request shorthands	Both (input/request: workflow)
Tools (function calling)	Let a chat: resource call other resources mid-response	Workflow
Inline resources	chat/sql/python/... actions nested in a resource's before:/after:	Workflow

Control flow and input

Concept	What it is	Mode
Validation and control	The validations: block - skip, preflight check, route/method limits, input schema	Workflow
Error handling (onError)	Retry, fallback value, or fail on a resource error	Workflow
Items iteration	Run a resource once per list entry (for-each)	Both
While-loop	Repeat a resource while a condition holds; every: for scheduled tasks	Both
Input sources	Feed a workflow from an HTTP API, a chat bot, or a file	Workflow
Jinja2 templates	YAML preprocessing and project scaffolding	Both

State

Concept	What it is	Mode
Session storage	Values that persist across requests from the same caller	Workflow
Persistent memory	Project-scoped facts the agent recalls across sessions	Agent (tools also work in workflow)
Memory internals	Auto-extraction, the memory graph, and prompt injection	Agent