# flow-on-sx loop agent (single agent, queue-driven)

Role: iterates `plans/flow-on-sx.md` forever. **Durable workflows on Scheme** — the
call/cc + delimited continuation showcase that justifies pulling R7RS into
production. art-dag's natural successor: DAG-of-tasks with pause/resume across
process restarts. fed-sx extension turns local flows into distributed ones.

```
description: flow-on-sx queue loop
subagent_type: general-purpose
run_in_background: true
isolation: worktree
```

## Prompt

You are the sole background agent working `/root/rose-ash/plans/flow-on-sx.md`.
Isolated worktree, forever, one commit per feature. Push to `origin/loops/flow`
after every commit.

## Restart baseline — check before iterating

1. Read `plans/flow-on-sx.md` — roadmap + Progress log.
2. `ls lib/flow/` — pick up from the most advanced file.
3. If `lib/flow/tests/*.sx` exist, run them via `bash lib/flow/conformance.sh`. Green
   before new work.
4. If `lib/flow/scoreboard.md` exists, that's your baseline.
5. Read `lib/scheme/scheme.sx` public API once — that's your substrate.

## The queue

Phase order per `plans/flow-on-sx.md`:

- **Phase 1** — declarative DAG: `defflow`, `sequence`, `parallel`, sync runtime,
  basic api
- **Phase 2** — control flow + error handling: `cond`, `retry`, `timeout`,
  `try-catch`
- **Phase 3** — **THE SHOWCASE**: `suspend`/`resume` via `call/cc`, persistent
  store, crash recovery
- **Phase 4** — distributed nodes via fed-sx (remote-node, handoff, replication)

Within a phase, pick the checkbox that unlocks the most tests per effort.

Every iteration: implement → test → commit → tick `[ ]` → Progress log → next.

## Ground rules (hard)

- **Scope:** only `lib/flow/**` and `plans/flow-on-sx.md`. Do **not** edit `spec/`,
  `hosts/`, `shared/`, other `lib/<lang>/` dirs, `lib/stdlib.sx`, or `lib/` root.
  May **import** from `lib/scheme/` only (its public API).
- **NEVER call `sx_build`.** 600s watchdog. If sx_server binary broken → Blockers
  entry, stop.
- **Shared-file issues** → plan's Blockers with minimal repro.
- **SX files:** `sx-tree` MCP tools ONLY. `sx_validate` after edits.
- **Worktree:** commit, then push to `origin/loops/flow`. Never touch `main` or
  `architecture`.
- **Commit granularity:** one feature per commit. Short factual messages
  (`flow: retry combinator with exponential backoff + 6 tests`).
- **Plan file:** update Progress log + tick boxes every commit.

## flow-specific gotchas

- **Continuations must be re-entrant.** Phase 3's `suspend` captures a continuation
  that may be re-entered after a process restart. That means: no captured file
  descriptors, no captured sockets, no captured live runtime references that won't
  survive serialization. State referenced by the continuation must be plain SX data
  or live in the flow store.
- **call/cc, not call-with-escape-continuation.** R7RS distinguishes. Use the full
  call/cc for resume; escape-only continuations cannot be re-entered. Read
  `lib/scheme/r7rs.md` (or equivalent) to confirm semantics.
- **`parallel` in Phase 1 is sequential.** Don't try threading until Phase 3+. Just
  evaluate branches in order, collect results, return joined value. Document the
  semantics clearly so users don't assume true concurrency.
- **Retry doesn't retry continuations.** If a node has already suspended, retry on
  resume doesn't re-run it from scratch — it resumes. `retry` only applies to
  exceptions raised before suspend. Be explicit in the API.
- **Cancellation invalidates the continuation.** `(flow/cancel id)` must remove the
  stored continuation so a stale `resume` cannot wake it. Document semantics.
- **Timeouts in pure SX are tricky.** Without a scheduler, `timeout` is a budget on
  step count or wall-clock probed at safe points. Pick one approach (probably step
  budget for determinism) and document.

## General gotchas (all loops)

- SX `do` = R7RS iteration. Use `begin` for multi-expr sequences.
- `cond`/`when`/`let` clauses evaluate only the last expr — wrap multiples in `begin`.
- `env-bind!` creates a binding; `env-set!` mutates an existing one (walks scope chain).
- `sx_validate` after every structural edit.
- `list?` returns false on raw JS Arrays — host data must be SX-converted.

## Style

- No comments in `.sx` unless non-obvious.
- No new planning docs — update `plans/flow-on-sx.md` inline.
- Short, factual commit messages.
- One feature per iteration. Commit. Log. Push. Next.

Go. Start by reading the plan; find the first unchecked `[ ]`; implement it.