Lifecycle reference - Fused

Root files under lifecycle/**/*.py add behavior around the agent. Harnest discovers decorated functions and ignores ordinary helpers.

Decorator index

Decorator	Allowed	Purpose	Guide
`@lifecycle.resource`	Many	Application dependency	Application resources
`@lifecycle.skills.source("name")`	Many, with unique names	Dynamic skill catalog	Agent Skills
`@context("name")`	Many	Publish a resource	Application resources
`@lifecycle.agent.before/after/on_error`	Many	Agent policy and observation	Invocation hooks
`@lifecycle.model.before/after/on_error`	Many	Model policy and observation	Invocation hooks
`@lifecycle.tool.before/after/on_error`	Many	Tool policy and observation	Invocation hooks
`@lifecycle.mcp.before/after/on_error`	Many	Governed remote-tool policy	Invocation hooks
`@lifecycle.http.before/after/on_error`	Many	HTTP request and response policy	Invocation hooks
`@lifecycle.output_policy`	Zero or one	Public SubAgent messages	Output policy
`@lifecycle.adk_plugin`	Many	ADK-native behavior	Native integrations
`@lifecycle.langgraph_middleware`	Many	LangGraph-native behavior	Native integrations
`@lifecycle.http_routes`	Many	Application HTTP routes	Custom HTTP endpoints
`@lifecycle.storage.sessions`	Exactly one	Sessions and transcripts	Sessions
`@lifecycle.storage.checkpoints`	Exactly one	In-progress execution	Checkpoints
`@lifecycle.storage.assets("name")`	Many, with unique names	Multimodal asset storage	Store and retrieve media
`@lifecycle.storage.custom("name")`	Many, with unique names	Domain repositories	Sessions and application storage
`@lifecycle.authenticate`	Zero or more	Request identity	Authentication
`@lifecycle.credential_provider`	Zero or one	Downstream credentials	Authentication
`@lifecycle.telemetry_exporter`	Many	Trace and log destination	Telemetry

Factory rules

Rule	Behavior
Signature	Synchronous and zero-argument unless it is a callback; `http_routes` receives one `AgentInvoker`
Return type	Must match the decorator’s resource or policy type
Duplicates	Single-owner factories reject duplicates
Ordering	Lower `order`, plugin dependency/source order, then source location
Ownership	Root agent only
Startup failure	Application does not serve
Shutdown	Harnest closes resources it owns

Lifecycle overview

Choose the extension type before opening its focused guide.