workflows: a host-agnostic Rust engine for agentic workflows (open source)

Workflows is a Rust library crate (not a hosted service; the crate name on crates.io/GitHub is tinyflows) that models an automation as a WorkflowGraph: a directed graph of typed nodes and edges. You build or generate that graph, it gets structurally validated, compiled into an opaque CompiledWorkflow, and lowered — once per run — onto tinyagents, a state-graph execution engine, via engine::run. model::WorkflowGraph -> validate -> compiler::compile -> engine::run (typed graph) (structural) (validated handle) (lowers onto tinyagents, drives to done) Run state is a single JSON value shaped like { "run": { "trigger": … }, "nodes": { "": { "items": [ … ] } } }. A merge reducer folds each node's output under its own id, so independent branches never collide — which is what keeps parallel fan-out deterministic. The node catalog Kind What it does trigger Entry node that starts the workflow (exactly one per graph); firing mode is host-driven agent Runs an LLM agent turn, with optional chat-model / memory / tool / output-parser sub-ports tool_call Invokes one specific integration action deterministically, no LLM involved http_request Outbound HTTP request code Sandboxed user code (JavaScript or Python) output_parser Parses/validates an upstream agent's output into a structured shape sub_workflow Runs another workflow as a nested sub-graph and returns its output condition Two-way IF, emits on true/false switch Multi-way branch keyed by an expression result merge Fan-in barrier — waits for every wired predecessor before running split_out Fan-out — emits one item per element of a list transform Pure, expression-based field mapping over the run state Data flows between nodes as arrays of items shaped { json, binary?, paired_item? } — closer to n8n's item-based model than a plain function-composition DAG — and node config can reference the run scope with =-prefixed expressions like =item.name. The part I actually want to talk about: host-agnosticism Every place this engine would n