# flow-on-sx Scoreboard

**All tests pass: 49 / 49 across 2 suites.**

`bash lib/flow/conformance.sh`

## Per-suite breakdown

| Suite | Passing | Covers |
|-------|--------:|--------|
| basic |     18  | Phase 1: single nodes, linear sequence, data-flow threading, defflow, parallel fan/join, nested composition, publish-shaped flow |
| control |  31  | Phase 2: `branch` (6); error model `fail`/`failed?`/`fail-reason` (6); `try-catch` (6); `retry n` (6); `timeout` cooperative step budget (7) |

## Architecture

Flow combinators are a **Scheme prelude** (`lib/flow/spec.sx`) loaded onto
`scheme-standard-env`. A flow is a Scheme procedure `input -> output`. The whole
flow executes inside the Scheme interpreter, so Phase 3's `suspend` (call/cc) will
capture the flow continuation directly.

- `lib/flow/spec.sx` — combinators: `flow-node`, `flow-id`, `flow-const`,
  `sequence`, `parallel`, `defflow`; `flow-load-combinators!`.
- `lib/flow/api.sx` — `flow/start` (Scheme); `flow-make-env`, `flow-run`,
  `flow-run-in` (SX helpers).
- `lib/flow/tests/basic.sx` — 18 cases.
- `lib/flow/conformance.sh` — loads substrate + flow layer, runs suites.

## Semantics notes

- **node** = 1-arg Scheme procedure; the upstream value is the argument. A node
  ignoring its argument is effectively a thunk.
- **sequence** threads left-to-right; empty sequence = identity.
- **parallel** fans the same input to every branch and joins results into a list.
  Evaluation is **sequential** for now; true concurrency arrives in Phase 3.

## Phases

- [x] Phase 1 — Declarative DAG + sequential execution (combinators + 18 tests, `flow/start`)
- [x] Phase 2 — Control flow + error handling (branch, error model, try-catch, retry, timeout)
- [ ] Phase 3 — Suspend / resume (the showcase)
- [ ] Phase 4 — Distributed nodes via fed-sx