plans: six subsystem outline plans for the SX rewrite (store, commerce, identity, content, events, host)

Gap analysis from the five-subsystem set (acl/feed/flow/mod/search):
- store-on-sx: event-sourcing foundation the others fake with in-memory lists (build first)
- commerce-on-sx: catalog/cart/pricing/orders on miniKanren (+ store + flow)
- identity-on-sx: OAuth2/sessions/membership on Erlang (the core acl assumes)
- content-on-sx: documents/blocks/CRDT on Smalltalk
- events-on-sx: calendar/ticketing on Datalog + flow-driven delivery
- host-on-sx: the web boundary — off Quart onto native server+SXTP now, dream-on-sx next

All DRAFT outlines; substrate choices proposed, not final.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plans/host-on-sx.md

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+# host-on-sx: The SX web host — off Quart, onto the kernel (Dream-bound)
+
+> **DRAFT outline.** The integration boundary that turns the subsystem libraries
+> into running services, and the strangler path off Python/Quart. This is the
+> dependency hub — it imports every subsystem. Decision recorded below: native
+> server + SXTP **now**, `dream-on-sx` framework layer **next**, Python only at the
+> external-integration edges.
+
+The subsystems (`feed`, `search`, `acl`, `mod`, `flow`, `commerce`, `identity`,
+`content`, `events`) are libraries. Something has to receive an HTTP request, route
+it, call the right subsystem, and serialize the response. Today that's Python/Quart
+— the one large non-SX component in the stack: separate runtime, deploy, and
+failure mode. The goal is to move the web/host/domain layer onto the SX substrate
+and retire Quart, **incrementally (strangler-fig), never big-bang.**
+
+This is already underway: a native OCaml HTTP server is live in prod on
+`sx.rose-ash.com` (~3ms cached, ~323 req/s, ~2MB RSS), `defhandler`/`defpage`
+exist, and a partial **SXTP** protocol is specced. That is the unblocked near-term
+host — no `ocaml-on-sx` dependency.
+
+## Two layers, two timelines
+
+1. **Now (unblocked): native server + SXTP adapter + SX handlers.** Route rose-ash
+   endpoints onto the SX host one at a time. Each migrated endpoint is an SX
+   handler dispatching to a subsystem; Quart proxies the rest until cut over.
+2. **Next: `dream-on-sx` as the framework layer.** Dream gives Quart-grade
+   ergonomics — typed routing, middleware stacks, sessions, CSRF. It is gated on
+   `ocaml-on-sx` Phases 1–5 + minimal stdlib. **This plan is the concrete target
+   user that un-parks `dream-on-sx`** (see `plans/dream-on-sx.md`): "the subsystems
+   need an HTTP front door" is the real feature pulling Dream. Until then, do not
+   block migration on Dream — the native server is sufficient.
+3. **Always: Python only at the edges.** External integrations — SumUp payments,
+   Ghost CMS, ActivityPub crypto, IPFS/Kubo — ride Python libraries today. They
+   stay as thin injected adapters (Python/FFI) behind subsystem interfaces until
+   native replacements exist. "Drop Quart" ≠ "drop every line of Python."
+
+## Status (rolling)
+
+`bash lib/host/conformance.sh` → **0/0** (not yet started)
+
+## Ground rules
+
+- **Scope:** `lib/host/**` and `plans/host-on-sx.md`. May **import** every subsystem
+  + the kernel's server/SXTP surface. Do **not** edit `spec/`, `hosts/`, `shared/`,
+  or subsystem internals — wire to their public APIs only. Host-primitive / server
+  changes belong in `hosts/` (out of scope) → Blockers.
+- **Architecture:** a route maps (method, path) → handler; a handler is an SX fn
+  `request -> response` that calls subsystem APIs; middleware is composed handlers
+  (auth via `identity`, permission via `acl`, mute via subsystem prefs). SXTP is the
+  wire format between host and subsystem-as-service.
+- **Migration discipline:** each endpoint moved must be behavior-equivalent to its
+  Quart original (golden-response test before flip). Keep a migration ledger.
+- **Commits:** one feature per commit. Progress log + tick boxes.
+
+## Architecture sketch
+
+```
+HTTP request                            HTTP response
+        │                                       ▲
+        ▼                                       │
+native OCaml http server (prod)  ──────►  lib/host/router.sx
+   (hosts/ — out of scope)                  — (method,path) → handler
+        │                                       ▲
+        ▼                                       │
+lib/host/middleware.sx                  lib/host/handler.sx
+  — auth(identity) ∘ acl ∘ mute ∘ ...     — request → subsystem call → response
+        │                                       ▲
+        ▼                                       │
+lib/host/sxtp.sx                        subsystem APIs (feed/search/commerce/…)
+  — wire format, host↔service             — called via public interfaces
+        │
+        └── external edges: SumUp / Ghost / AP / IPFS  → injected Python/FFI adapters
+```
+
+## Phase 1 — Router + handler + one real endpoint
+- [ ] `router.sx` — route table, (method,path) match
+- [ ] `handler.sx` — request/response model, subsystem dispatch
+- [ ] migrate ONE read endpoint (e.g. a feed timeline) end-to-end, golden test
+- [ ] `conformance.sh` + scoreboard
+
+## Phase 2 — Middleware + SXTP
+- [ ] `middleware.sx` — composable auth/acl/mute/error layers
+- [ ] `sxtp.sx` — host↔subsystem wire format (align with existing spec)
+- [ ] migrate a write endpoint (auth + permission + action)
+
+## Phase 3 — Strangler migration ledger
+- [ ] enumerate Quart endpoints; track migrated vs proxied
+- [ ] golden-response harness vs the live Quart responses
+- [ ] cut over a whole domain (smallest: `likes` or `relations`) as proof
+
+## Phase 4 — Dream framework layer (gated)
+- [ ] gate: `ocaml-on-sx` Phases 1–5 + minimal stdlib green
+- [ ] adopt `dream-on-sx` routing/middleware/session ergonomics over the same handlers
+- [ ] re-home external adapters as native where replacements land
+
+## Progress log
+(loop fills this in)
+
+## Blockers
+(loop fills this in)