# 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` → **156/156** (9 suites: handler, middleware, sxtp,
router, feed, relations, blog, server, ledger). Phases 1 & 2 DONE; Phase 3 cut-over
landed (50% off Quart). **The host now serves live HTTP** — `lib/host/server.sx`
bridges the native `http-listen` server to the Dream app and `lib/host/serve.sh`
boots it (verified: GET /health, /feed, /feed?actor=, relations get-children/
get-parents all serve real JSON on a host port; unknown→404). Remaining: golden
harness vs live Quart, internal-HMAC middleware, docker stack + Caddy subdomain.

## 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
- [x] `router.sx` — `host/make-app` assembles per-domain route groups + a built-in
      `/health` probe into one Dream router (reuses Dream's `dr/flatten-routes`)
- [x] `handler.sx` — JSON envelope (`host/ok`/`host/ok-status`/`host/error`),
      status-carrying `host/json-status` (Dream's `dream-json` is 200-only), and
      `host/query-int`. A host handler IS a Dream handler (request -> response).
- [x] migrate ONE read endpoint: `GET /feed` (`lib/host/feed.sx`) reads
      `feed/all` + stream combinators, serialises recent-first; `?actor=` filter,
      `?limit=` cap. Golden test asserts body == subsystem recent stream + envelope.
- [x] `conformance.sh` (mirrors `lib/dream`'s runner) — 28/28

## Phase 2 — Middleware + SXTP
- [x] `middleware.sx` — composable layers as `handler->handler`: `host/wrap-errors`
      (JSON 500), `host/require-auth` (bearer -> principal, JSON 401, INJECTED token
      resolver), `host/require-permission` (ACL `acl/permit?` gate, JSON 403,
      INJECTED resource extractor), `host/pipeline` (first = outermost). Reuses
      Dream's `dream-bearer-token` + `dream-catch-with`; calls lib/acl public API.
      Mute/prefs layer deferred (no blocker, add when a domain needs it).
- [x] `sxtp.sx` — host↔subsystem wire format (per `applications/sxtp/spec.sx`).
      Message algebra (`sxtp/request`/`response`/`condition`/`event` + status
      helpers `sxtp/ok`/`created`/`not-found`/`forbidden`/`invalid`/`fail`) as
      string-keyed dicts; verb/status/type as symbols (ride the wire bare). Codec:
      `sxtp/serialize` (dict → `text/sx` list form, deterministic field order,
      nested messages in their own list form, no `:msg` leak) and `sxtp/parse`
      (`text/sx` → dict, deep keyword-token→string normaliser). Dream bridge:
      `sxtp/from-dream` (HTTP req → SXTP req, method→verb, query→params) and
      `sxtp/to-dream` (SXTP resp → HTTP resp, status→code, body→`text/sx`).
- [x] migrate a write endpoint (auth + permission + action): `POST /feed`
      (`host/feed-write-routes resolve`) — auth ∘ ACL("post","feed") ∘ wrap-errors
      over `host/feed-create`, which parses the JSON body and `feed/post`s it (201);
      non-object body -> 400. Created activity is readable back via `GET /feed`.

## Phase 3 — Strangler migration ledger
- [x] enumerate Quart endpoints; track migrated vs proxied — `ledger.sx`: a
      catalogue of every endpoint (domain, method, path, Quart original, status
      `:native`/`:migrated`/`:proxied`, SX handler) + queries (by-status/by-domain,
      `host/ledger-find`, `host/ledger-served?`, distinct domains) and
      `host/ledger-coverage` (off-Quart % = (migrated+native)/total). Seeded with
      the live state: feed reads+writes migrated, `/health` native, the
      internal-only `relations`/`likes` data+action endpoints proxied.
- [ ] golden-response harness vs the live Quart responses
- [x] cut over a whole domain (`relations`) as proof — the CONTAINER relations are
      fully on the host (`lib/host/relations.sx`): reads `GET .../get-children` +
      `/get-parents` → `relations/children`/`parents`; writes `POST
      .../attach-child` + `/detach-child` → `relations/relate`/`unrelate`, behind
      the auth+ACL pipeline (mirrors POST /feed). Node model: graph atom = symbol
      `"type:id"`, edge = relation-type; `child`/`parent-type` params filter by
      `"type:"` prefix. Closed-loop test: attach → visible via get-children →
      detach → gone. The TYPED actions (`relate`/`unrelate`/`can-relate`) stay
      proxied by design — registry + cardinality validation lib/relations lacks.

## Phase 4 — Live wiring + Dream framework layer
- [x] native `http-listen` ↔ Dream-app bridge (`lib/host/server.sx`:
      `host/native-handler`/`host/serve`) + `lib/host/serve.sh` launcher. Serves
      real HTTP on a host port — verified live (health/feed/relations reads + 404).
- [x] promote into the docker stack + a Caddy subdomain — **LIVE at
      `https://blog.rose-ash.com`** (reusing a down Quart subdomain). New compose
      service `sx_host` (`docker-compose.dev-sx-host.yml`, container
      `sx-dev-sx_host-1`) runs `serve.sh` on `externalnet`; Caddy reverse-proxies
      `blog.rose-ash.com` → `sx-dev-sx_host-1:8000`. Required a `hosts/` fix:
      `http-listen` bound `inet_addr_loopback` only — added `SX_HTTP_HOST` env
      (default loopback; stack sets `0.0.0.0`) in `sx_server.ml`, rebuilt this
      worktree's binary. Verified: `/health`, `/feed`, relations reads serve real
      JSON through Cloudflare→Caddy; `/` 404 (no root route yet). `rose-ash.com`
      untouched. (Inode-pinned bind-mount gotcha: editing `/root/caddy/Caddyfile`
      via a tool swaps its inode so the container kept the old content — loaded live
      via reload-from-non-bind-path, then RECONCILED by restarting Caddy so the
      bind re-points to the corrected file. Verified post-restart: blog serves, and
      `sx.rose-ash.com`/`rose-ash.com` survived.)
- [x] blog published-post read endpoint — `lib/host/blog.sx`: `GET /<slug>/`
      renders a content-on-sx `CtDoc` to HTML via `content/html` (anonymous,
      world-visible). In-memory slug→doc registry now (swap `host/blog-lookup` for
      a persist-backed content stream later, handler/route unchanged). `:slug`
      catch-all mounted LAST so domain routes win. **LIVE**: `blog.rose-ash.com/
      welcome/` renders real HTML through Caddy. Needs Smalltalk+persist+content
      preloads + `(st-bootstrap-classes!)`+`(content/bootstrap!)` (self-bootstraps
      at load).
- [ ] proxy-to-Quart fallback for un-migrated paths (strangler requirement before
      a real subdomain fronts users).
- [ ] internal-HMAC middleware on `/internal/*` (service-to-service auth; protocol
      checks native, signature check needs an HMAC-SHA256 kernel prim — absent today).
- [ ] (gated) adopt `dream-on-sx` session/CSRF ergonomics; re-home external
      adapters as native where replacements land.

## Progress log

- **Phase 1 (DONE, 28/28).** `lib/host/{handler,router,feed}.sx` + three test
  suites + `conformance.sh`. The host is a thin wiring layer: a host handler is a
  Dream handler that calls a subsystem public API and serialises the result via a
  shared JSON envelope. First migrated endpoint: `GET /feed`.
  - **Decision — build on Dream from Phase 1, not a throwaway native model.** The
    plan front-matter gated Dream to Phase 4, but `dream-on-sx` is merged
    (commit fe958bda) and its gate (`ocaml-on-sx` P1–5+P6) is green (480/480), so
    reinventing request/response + routing would be pure duplication. Host reuses
    Dream's `types.sx` (request/response dicts), `json.sx` (encode), and
    `router.sx` (`dream-router`/`dream-get`/`dr/flatten-routes`). Phase 4's
    "adopt Dream ergonomics" is therefore largely already satisfied; what remains
    for Phase 4 is the live wiring against the real OCaml HTTP server + session.
  - The OCaml server handing a `dream-request`-shaped dict to SX handlers is a
    `hosts/` change (out of scope) — tracked under Blockers as the eventual
    live-wiring step. For now the host layer is exercised purely via conformance.

- **Phase 2 (middleware + write endpoint DONE, 43/43).** `lib/host/middleware.sx`
  + a guarded `POST /feed`. Middleware is plain function composition over Dream's
  primitives; auth/permission *policy* is injected (token resolver, resource
  extractor) so the layer is policy-free and testable. ACL authorisation runs
  against lib/acl's public `acl/permit?` (string atoms work — no symbol coercion
  needed). The write path proves the auth ∘ permission ∘ action stack end-to-end:
  401 unauth, 403 unpermitted, 201 + readback on success, 400 on bad body.
- **Phase 2 COMPLETE (82/82).** `lib/host/sxtp.sx` adds the SXTP codec + Dream
  bridge (39-test suite). Key representation calls, learned by probing the runtime:
  keywords are strings at eval time but the `serialize` primitive renders
  string-keyed dicts back as `{:k v}` and symbols bare — so messages are
  string-keyed dicts with verb/status/type as symbols, and a small str-based
  emitter produces wire-faithful list form. `parse` needs a deep normaliser
  because parsed keyword tokens are a distinct type (not `=` to string literals).
  `unquote-splicing` is unreliable here, so the serializer is str-based, not
  quasiquote-based.
  - **Next: Phase 3 — strangler migration ledger.** Enumerate the Quart endpoints
    (use the `rose-ash-services` `svc_routes` MCP tool), track migrated vs proxied,
    and stand up a golden-response harness against the live Quart responses. Then
    cut over the smallest whole domain (`likes` or `relations`) as proof.

- **Phase 3 — ledger module (DONE, 107/107).** `lib/host/ledger.sx` + a 25-test
  suite. Enumerated the endpoint surface via the `rose-ash-services` MCP
  (`svc_routes`/`svc_queries`/`svc_actions`): `likes` and `relations` have **no
  public blueprint routes** — they're internal-only, exposed as
  `/internal/data/{query}` + `/internal/actions/{action}` (HMAC-signed). The
  ledger is a pure-data catalogue keyed by (domain, method, path) carrying each
  endpoint's Quart original, status, and serving SX handler; coverage reports the
  off-Quart percentage. Cut-over target chosen: **`relations`** (already has a real
  SX subsystem `lib/relations` — children/parents reads + relate/unrelate writes
  map straight onto its public API); `likes` stays proxied (no SX lib to dispatch
  to). NEXT: migrate the `relations` read endpoints onto host handlers (flip their
  ledger status to `:migrated`) with golden tests.

- **Phase 3 — relations READ cut-over (DONE, 121/121).** `lib/host/relations.sx`
  + a 13-test golden suite; ledger flipped (off-Quart coverage 27% → 45%). The two
  internal read queries (`get-children`, `get-parents`) now dispatch to the
  `lib/relations` Datalog graph. Bridge: the Quart `(type, id)` node key maps to a
  graph atom `(string->symbol "type:id")` with relation-type as the edge kind;
  optional `child-type`/`parent-type` params filter the result list by `"type:"`
  prefix (verified live: composite-string nodes round-trip through
  `relations/relate` → `relations/children`). Golden discipline: `relations` is
  internal-only (no public Quart route — confirmed via `svc_routes`), so the golden
  is a **pinned fixture** (a known graph loaded in-test, asserted as
  `subsystem-call + envelope`) rather than a live Quart capture. Reads are
  unguarded for now — the signed-internal-auth gate is a separate middleware layer,
  same as the feed reads. NEXT: relations WRITE actions (`relate`/`unrelate`)
  behind the auth+ACL pipeline (mirroring POST /feed).

- **Phase 3 — relations WRITE cut-over (DONE, 132/132).** `lib/host/relations.sx`
  gains `host/relations-attach`/`-detach` (`POST .../attach-child` + `/detach-child`)
  and `host/relations-write-routes` — the write side of the container reads,
  dispatching to `relations/relate`/`unrelate` over the same `"type:id"` node
  model so an attach is immediately visible through `get-children`. Each runs
  behind the host pipeline `wrap-errors ∘ require-auth ∘ require-permission`
  (`"relate"`/`"unrelate"` on `"relations"`) — exactly the POST /feed stack. The
  relations test suite proves the closed loop end-to-end: 401 unauth, 403 authed-
  but-unpermitted (graph unchanged), 201 attach → child visible via the migrated
  read → 200 detach → child gone; 400 on bad/short payloads. The ledger now models
  the full relations surface (7 endpoints): container reads+writes `:migrated`,
  typed `relate`/`unrelate`/`can-relate` `:proxied` (registry/cardinality
  validation not in lib/relations). Off-Quart coverage 45% → **50%** (7/14).
  `relations` is the first whole *coherent feature* (container relations) fully
  off Quart. NEXT: golden-response harness vs live Quart, then survey the next
  domain (blog/likes proxied — likes needs an SX subsystem first).

- **Phase 4 — live wiring bridge (DONE, 145/145).** `lib/host/server.sx` adapts the
  native `http-listen` contract (string-keyed req `{"method" "path" "query"
  "headers" "body"}` → `{:status :headers :body}`) to the Dream app: `host/-native
  ->dream` reassembles `path`+`query` into a target `dream-request` parses;
  `host/-dream->native` is near-identity (dream-response is already `{:body
  :headers :status}`). `host/serve port groups` = `http-listen` over
  `host/native-handler (host/make-app groups)`. `lib/host/serve.sh` boots the full
  module set (mirrors conformance) and serves in the foreground (container-entry
  shaped). **Verified live** on a host port: `/health` 200 JSON, `/feed` recent-
  first seeded activities, `/feed?actor=` filtered, relations `get-children`/`get-
  parents` real JSON, unknown→404. Demo run was a standalone `sx_server.exe`
  process (NOT the docker stack) — killed by its own PID, never `pkill` (siblings
  share the binary). The standing "live wiring is a hosts/ change" Blocker is
  resolved for the SX side: the bridge is pure SX in `lib/host`; only the *launch*
  (docker stack + Caddy) remains. NEXT: golden harness, internal-HMAC, then promote
  into the stack behind a fresh subdomain.

## Blockers

- **Live wiring to the native OCaml HTTP server** (Phase 3/4): the prod server in
  `hosts/` must hand SX handlers a `dream-request` dict and serialise the returned
  `dream-response`. That is a `hosts/` change (out of scope for this loop, which is
  `lib/host/**` only). Until then, endpoints are verified via `conformance.sh`, not
  HTTP. Not blocking Phase 2 (middleware + SXTP + a write endpoint).
- **Worktree tooling:** in this `loops/host` worktree every sx-tree *write* tool
  (`sx_write_file`, `sx_replace_node`, …) raises `yojson "Expected string, got
  null"` at the MCP layer — same class as the `loops/dream` worktree gotcha, but
  here even `sx_write_file` fails. Read-side sx-tree tools work. New `.sx` files
  were created with the `Write` tool (the .sx hook is inactive in this worktree)
  and each validated afterwards with `sx_validate` to keep the parse guarantee.