flowr 0.3.20260427

non-deterministic state machine specification to knead workflows

flowr

⚠️ Beta — do not install. This project is under active development with breaking changes in progress. The API, package structure, and configuration may change without notice until the first stable release.

Non-deterministic state machine specification to knead workflows.

flowr is a Python library and CLI for defining, validating, and visualising workflow state machines in YAML. Define your flows in a declarative format, validate them against the specification, query states and transitions, and export Mermaid diagrams — all from the terminal or programmatically.

Install

pip install flowr

Requires Python 3.13+.

Quick Start

Create a flow definition YAML file:

flow: deploy
version: 1.0.0
exits: [deployed, failed]

states:
  - id: prepare
    next:
      ready: execute

  - id: execute
    next:
      success: deployed
      error: failed

  - id: review
    next:
      approve:
        to: deployed
        when: { score: ">=80" }
      reject: failed

Validate it:

$ flowr validate deploy.yaml
valid: True

Query states and transitions:

$ flowr states deploy.yaml
prepare
execute
review

$ flowr next deploy.yaml review
state: review
next: approve (guarded)
next: reject

$ flowr transition deploy.yaml review approve --evidence score=85
from: review
trigger: approve
to: deployed

Export as Mermaid:

$ flowr mermaid deploy.yaml
stateDiagram-v2
    state "prepare" as prepare
    state "execute" as execute
    state "review" as review
    ...

CLI Reference

Command	Description
flowr validate <file>	Validate a flow definition
flowr states <file>	List all state ids
flowr check <file> <state> [<target>]	Show state details or transition conditions
flowr next <file> <state> [--evidence K=V]	Show valid next transitions
flowr transition <file> <state> <trigger> [--evidence K=V]	Compute next state
flowr mermaid <file>	Export as Mermaid state diagram

All commands accept --json for machine-readable output.

Evidence can be passed with --evidence key=value (repeatable) or --evidence-json '{"key": "value"}'.

Documentation

• flowr docs — hosted documentation
• Flow Definition Specification — authoritative YAML format reference (fields, conditions, subflows, validation rules)
• System Overview — architecture, domain model, module structure, and API
• Product Definition — product boundaries, users, and scope

Development

# Install with dev dependencies
uv sync --all-extras

# Run tests
uv run task test

# Fast tests (skip slow)
uv run task test-fast

# Full test suite with coverage
uv run task test-build

# Lint and format
uv run task lint

# Type checking
uv run task static-check

License

MIT