plans: briefings for 5 language chisels + host/relations/artdag/dream

Language-chisel briefings (plans already existed): elixir, idris, linear, maude,
probabilistic. host-on-sx briefing (native server now, Dream framework layer next).
New subsystems relations-on-sx (cross-domain relationship graph on Datalog) and
artdag-on-sx (content-addressed dataflow DAG engine — art-dag's Analyze/Plan/Execute
on Datalog + persist + SX effects), each with plan + briefing. Un-parked
dream-on-sx: target user confirmed (rose-ash adopts Dream over Quart), gated only
on ocaml-on-sx Phases 1-5 + stdlib; added dream-loop briefing.

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

plans/agent-briefings/relations-loop.md

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+# relations-on-sx loop agent (single agent, queue-driven)
+
+Role: iterates `plans/relations-on-sx.md` forever. **Cross-domain relationship
+graph on Datalog** — the internal `relations` service. Where acl asks "may X do Y"
+on Datalog, relations asks "how is X connected to Y": children, ancestors,
+reachability, the connecting path, cycles. Sits on `lib/datalog/` (its public API);
+adds a relationship vocabulary on top. One feature per commit.
+
+```
+description: relations-on-sx queue loop
+subagent_type: general-purpose
+run_in_background: true
+isolation: worktree
+```
+
+## Prerequisites — check before starting
+
+1. **`lib/datalog/` present** with its public API (`lib/datalog/datalog.sx`).
+   relations imports it; it does not reimplement the engine.
+
+**Pre-flight:**
+```
+ls /root/rose-ash/lib/datalog/datalog.sx
+```
+If missing, stop and record a Blockers entry. (Investigate the Datalog public API —
+how to assert facts, add recursive rules, and run queries — before writing any
+relationship code; the plan cites `datalog.sx` as the entry point.)
+
+## Prompt
+
+You are the sole background agent working `/root/rose-ash/plans/relations-on-sx.md`,
+in an isolated git worktree on branch `loops/relations`, forever, one commit per
+feature. Push to `origin/loops/relations` after every commit. Never touch `main` or
+`architecture`.
+
+## Restart baseline — check before iterating
+
+1. Read `plans/relations-on-sx.md` — Roadmap + Progress log + Blockers.
+2. Run the pre-flight; record gaps in Blockers.
+3. `ls lib/relations/` — pick up from the most advanced file. No dir → Phase 1.
+4. If `lib/relations/tests/*.sx` exist, run them via `bash lib/relations/conformance.sh`
+   (`SX_SERVER=/root/rose-ash/hosts/ocaml/_build/default/bin/sx_server.exe`). Green
+   before new work.
+5. Read the `lib/datalog/` public API once — assert facts, recursive rules, queries.
+   The acl-on-sx engine (`lib/acl/engine.sx`) is a worked example of recursive
+   reachability on Datalog — read it for the *shape*, do not import it.
+
+## The queue
+
+Phase order per `plans/relations-on-sx.md`:
+
+- **Phase 1** — schema (`rel(Src, Dst, Kind)` facts) + assert/retract api + direct
+  children/parents/related queries + conformance harness
+- **Phase 2** — recursive reachability (ancestors/descendants/`reachable?`), roots/
+  leaves, **cycle detection** (`reachable(X,X)`)
+- **Phase 3** — typed relations coexisting + **path explanation** (the connecting
+  chain from the Datalog derivation) + distance / shortest path
+- **Phase 4** — federation (cross-instance links via mock fed-sx, peer-trust gating
+  like acl's non-transitive trust, revocation)
+
+Within a phase, pick the checkbox with the best tests-per-effort ratio.
+Every iteration: implement → test → commit → tick `[ ]` → Progress log → push → next.
+
+## relations-specific gotchas
+
+- **Reachability is the acl inheritance pattern.** `reach(X,Y) :- edge(X,Y).` /
+  `reach(X,Y) :- edge(X,Z), reach(Z,Y).` — recursive Datalog, bottom-up. Read
+  acl's engine for the worked shape; re-derive, don't import.
+- **Nodes are opaque ids.** relations is content-agnostic — a node is a string id;
+  domains own what ids mean. Don't bake in domain semantics.
+- **Kind isolation matters.** Reachability over `parent` must not leak through
+  `reply` edges unless asked — parameterize rules by kind, or filter the edge
+  relation per query.
+- **Cycles are real data, not errors.** Some graphs legitimately cycle; `cycle?`/
+  `acyclic?` are *queries*, not exceptions. Don't assume a DAG.
+- **The path IS the explanation** — Phase 3's connecting chain is relations' answer
+  to acl's proof tree; build it from the derivation, not by re-walking edges ad hoc.
+- **Federation trust is non-transitive and gated, not auto-applied** — a peer's link
+  binds only under a local trust fact (mirror acl; don't copy acl code).
+
+## Ground rules (hard)
+
+- **Scope:** only `lib/relations/**` and `plans/relations-on-sx.md`. Do **not** edit
+  `spec/`, `hosts/`, `shared/`, `lib/datalog/**` (read-only — import its public API),
+  `lib/acl/**` (read-only — reference for shape only), or other `lib/<lang>/`.
+- **Don't modify Datalog.** Shared-engine issues → failing test + Blockers entry.
+- **NEVER call `sx_build`** (600s watchdog). Broken `sx_server.exe` → Blockers, stop.
+- **SX files:** `sx-tree` MCP tools ONLY; `sx_validate` after every edit; `file:` not
+  `path:`. Never `Edit`/`Read`/`Write` on `.sx`.
+- **Worktree:** commit, then push `origin/loops/relations`. Never `main`/`architecture`.
+- **Commits:** one feature per commit (`relations: transitive ancestors + cycle? + 6 tests`).
+- **Plan file:** Progress log (newest first) + tick boxes every commit.
+- **Blocked 2 iterations on one issue → Blockers entry, move on.**
+- **acl convergence:** flag the shared recursive-reachability shape in the Progress
+  log if you see it, but **do not extract** — see the extraction note in
+  `plans/mod-on-sx.md` (extraction is the integrator's post-merge job, not a loop's).
+
+## 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`.
+- `let` is parallel — nest `let`s when one binding references an earlier one.
+- `env-bind!` creates a binding; `env-set!` mutates an existing one.
+- Namespace-prefix guest helpers (`relations/…`) — short/host-colliding names get shadowed.
+- Shell heredoc `||` gets eaten — escape or use `case`.
+
+## Style
+
+- No comments in `.sx` unless non-obvious. No new planning docs — update the plan.
+- Short, factual commit messages. One feature per iteration. Commit. Log. Push. Next.
+
+Go. Run the pre-flight. If `lib/datalog/` is missing, stop and report. Otherwise
+read the plan and the Datalog public API, find the first unchecked `[ ]`, implement it.