First contact
Read Varro as a chain, not a vocabulary list.
Start with a real source statement: someone has written a requirement, policy, diagram, or code rule. Varro turns the checkable part of that source material into VSL so a tool can reject wrong structure. Helios comes later, after the contract checks, to build and run surfaces from it.
Plain meanings used here
- Specification
- A statement of what a system, product, or workflow is meant to be or do. It may include prose, diagrams, code, policies, examples, and checkable contract structure.
- Authoritative sources
- The prose requirements, diagrams, source code, policies, and standards that own the truth. Varro should reflect these sources, not replace them.
- Source of truth
- The artifact that wins when two surfaces disagree. In this course, source artifacts outrank Varro pages, agent answers, and caller preferences.
- Varro
- The governed specification layer that turns source-backed system structure into a checkable VSL contract.
- VSL
- Varro Specification Language: the language used to describe systems, types, fields, enums, actions, workflows, routes, context, and runtime settings.
- Checkable contract
- A specification structure that a tool can validate and reject. The point is not more prose; the point is a contract that can fail when it is wrong.
- Helios
- The build and run engine that ingests the checked contract, generates operational surfaces, and hosts governed runtime services.
Follow one example through the diagram
- 1Source says the rule
A course policy says every tutor answer must cite the source it used.
- 2Varro captures the checkable shape
The source-backed rule becomes a VSL contract with the entities, allowed states, and actions the checker can reject.
- 3Helios builds from the checked contract
Only after the contract checks does the build/run layer generate routes, services, and runtime surfaces.
- 4The live system follows the guardrails
The running service uses the checked structure when it answers requests and handles state.
- 5Agents and learners use governed surfaces
A tutor, dashboard, CLI, or web page can use the system, but it still cites sources rather than becoming the source of truth.
Learner path
Start with source authority, then move toward running systems.
The reference modules are organised by construct. This path is organised by what a new reader needs to know first: where authority lives, what Varro checks, what Helios does with the checked contract, and how live systems and agents sit on top.
1Authority foundationSources are the truth
2Varro / VSLSpecification that can fail
3HeliosBuild and run engine
4Live systemGoverned runtime
5Agents & surfacesPeople and agents use it
The teachable sequence
01 · Authoritative sources
Start with one real source.
Before the reference modules, identify the source artifact and ask which part can be checked. Varro is the governed specification layer; VSL is the language for the checkable contract.
Terms introduced
- Specification
- A statement of what a system, product, or workflow is meant to be or do. It may include prose, diagrams, code, policies, examples, and checkable contract structure.
- Authoritative sources
- The prose requirements, diagrams, source code, policies, and standards that own the truth. Varro should reflect these sources, not replace them.
- Source of truth
- The artifact that wins when two surfaces disagree. In this course, source artifacts outrank Varro pages, agent answers, and caller preferences.
- Varro
- The governed specification layer that turns source-backed system structure into a checkable VSL contract.
- VSL
- Varro Specification Language: the language used to describe systems, types, fields, enums, actions, workflows, routes, context, and runtime settings.
- Checkable contract
- A specification structure that a tool can validate and reject. The point is not more prose; the point is a contract that can fail when it is wrong.
- Authority stack
- The ordering rule for disagreements: authoritative sources first, Varro as the window, callers and agents last.
Concepts to read next
Varro
VSL
Authority Stack
You are ready to continue when you can
- point to the source artifact behind a Varro claim
- state what Varro is not allowed to replace
- explain what it means for one part of a specification to be checkable
Reference pages
02 · Varro: VSL -> checkable contract
Learn the VSL core contract shape.
The first concrete Varro idea is not the command verbs. It is the structure of a checked contract: a system with types, fields, and closed enums.
Assumed terms
Terms introduced
- Varro
- The governed specification layer that turns source-backed system structure into a checkable VSL contract.
- VSL
- Varro Specification Language: the language used to describe systems, types, fields, enums, actions, workflows, routes, context, and runtime settings.
- System
- The top-level VSL container for a governed domain. It names the mission, authority, maturity, context, type model, behavior, and surfaces.
- Type
- A named record shape made of typed fields. In VSL, types describe data shape and do not own behavior.
- Field
- A named value inside a type, with a kind and a required or optional presence rule.
- Enum
- A closed set of allowed values. New values are not silently accepted at use sites.
Concepts to read next
You are ready to continue when you can
- identify a VSL system as the top-level contract container
- explain why a type is a data shape rather than a class with methods
- explain why closed enums make invalid states fail
Reference pages
03 · Varro behavior
Add behavior without losing governance.
After the data shape, learn how the contract describes governed operations, read-only queries, and ordered workflows.
Assumed terms
Terms introduced
- Action
- A governed operation that can change state. It carries inputs, risk, and lowering information, and is run under preview-by-default.
- Query
- A read contract that declares what information can be asked for and which authority it reads from. A query does not mutate state.
- Workflow
- An ordered sequence of governed steps. The order is part of the contract.
- Preview-by-default
- The safety principle that governed actions describe their effects before committing them. Execution is explicit rather than accidental.
Concepts to read next
action
query
workflow
preview-by-default
You are ready to continue when you can
- distinguish a mutating action from a read-only query
- explain why workflow order is load-bearing
- state why preview-by-default is safer than direct mutation
Reference pages
04 · Helios: build and run engine
See what happens after the contract checks.
A checked contract becomes operational only when it can be lowered, built, and run. This is where compile targets, routes, views, context, runtime, and Helios enter the story.
Assumed terms
Terms introduced
- Helios
- The build and run engine that ingests the checked contract, generates operational surfaces, and hosts governed runtime services.
- Compile
- The VSL lowering step that produces a typed downstream artifact for a named target.
- Route
- A named address in the governed Helios resource space. It is not just an HTTP endpoint label.
- View
- A declared way to render or project a selected part of system state.
- Context
- The governed resource root that anchors how routes, views, and runtime surfaces are resolved.
- Runtime
- The configured execution environment and settings that govern how a checked contract is hosted and operated.
Concepts to read next
compile
route
view
context
runtime
You are ready to continue when you can
- describe Helios as the build/run layer rather than the source of truth
- explain why a route is a governed address, not just an HTTP endpoint
- explain how context and runtime anchor generated surfaces
Reference pages
05 · Live system and agents
Use the running system through governed surfaces.
Only after the contract and build/run path are clear should the reader learn the interaction verbs and the agent/product surfaces that consume the live system.
Assumed terms
Terms introduced
- Live system
- The running governed system after a checked contract has been built, deployed, and connected to services and data.
- Agent surface
- A product, API, tutor, dashboard, CLI, or AI-agent interface that consumes the governed system without becoming the source of truth.
Concepts to read next
ask
show
check
run
create
agent
Varro
You are ready to continue when you can
- explain what each of the five verbs does at the surface
- distinguish a product or agent surface from the source of truth
- describe how an agent can cite sources without becoming authoritative
Reference pages
06 · Hardening and proof
Place maturity and crystallisation last.
The maturity ladder and crystallisation phases are useful after the reader knows what is being hardened. They describe how intent moves from draft to checked, bound, hardened, and eventually toward proof-oriented artifacts.
Assumed terms
Terms introduced
- Maturity
- A rung in the specification lifecycle, such as draft, checked, bound, or hardened.
- Crystallisation
- The hardening path from loose intent to more formal and checked artifacts, described here with phases such as Plasma, Gas, Liquid, Solid, and Crystal.
- Lean
- A theorem-proving environment used in the broader hardening story. In this course it appears as part of the Crystal/proof end of the model, not as a prerequisite for starting Varro.
Concepts to read next
draft
checked
bound
hardened
Plasma
Gas
Liquid
Solid
Crystal
You are ready to continue when you can
- explain why checked does not yet mean hardened
- place Plasma, Gas, Liquid, Solid, and Crystal in increasing formalisation order
- state why proof tooling belongs at the hardening end, not at the first learner step
Reference pages