Decide hall URI, static renderer sibling, and allowlist trust.

HOH-WP-0002 T01–T03. Public slug is frontmatter id. Rendering lives in
hall-render. T04 still needs the operator corpus call.

Assistant: grok
Assistant-Session: 01a09dc1-b21e-77e1-919e-fcad2f82b267

docs/adr/0001-hall-uri-and-renderer-boundary.md

@@ -0,0 +1,61 @@
+# ADR 0001 — Hall URI identifier, service shape, and renderer trust
+
+Status: accepted
+Date: 2026-09-14
+Workplan: HOH-WP-0002-T01, T02, T03
+
+## T01 — URI identifier
+
+The public path is:
+
+```
+https://helix.coulomb.social/hall-of-helix/<id>
+```
+
+`<id>` is the seat frontmatter `id` **verbatim** (example:
+`hall-worker-codex-statehub-snapshot-and-signature`). Uniqueness is already
+enforced by `make check`. The filename is not the URI and may be renamed.
+
+The `hall-worker-` prefix stays. Stripping it would require a second
+uniqueness domain; an opaque extra id would be a third name to keep.
+
+`id` is URL-safe `[A-Za-z0-9-]+` (mixed case is allowed; several existing
+Claude session ids use it). Once `status` is not `draft`, `id` is frozen.
+Corrections edit the body, not the identifier.
+
+`?renderer=` is optional; omitting it equals `renderer=default`.
+
+## T02 — Where the service lives
+
+This repo stays a **publication** corpus. Rendering is a sibling tooling
+repo, conventionally `hall-render`. Do not execute renderer code from this
+repository.
+
+First delivery is **static generation**: `hall-render` reads this repo at a
+pinned commit and emits HTML. The renderer set is known at build time.
+Dynamic on-request execution is declined for v1 (publication classification
+plus XSS surface).
+
+Deployment target: reef-railiance k3s, private/static objects behind the
+existing Traefik ingress. DNS `helix.coulomb.social` is a railiance-infra /
+railiance-cluster record, not owned by this publication repo. No live
+publish until T04 (operator corpus disposition).
+
+## T03 — Renderer contract and trust
+
+`renderer` is user-controlled input that selects code. Rules:
+
+1. Resolve only through a **fixed allowlist** in `hall-render`. Never treat
+   the parameter as a path, module, package, or URL.
+2. Unknown values return 404 (static: missing artifact). Do not fetch or
+   import.
+3. A renderer receives parsed Markdown plus frontmatter and returns markup.
+   No credentials, filesystem, or network.
+4. Output is sanitised before it is a page. HTML from a renderer is an XSS
+   sink.
+
+Registration is an in-repo allowlist in `hall-render`, not reuse-surface
+(that catalog is capability discovery, not a safe code-execution index).
+
+Input: `{frontmatter, markdown, entry_id}`. Output: `{html}`. Default
+renderer is named `default` and is the only one in the first allowlist.