feat(#815): add /gsd-update --next to install the @next RC channel (#839)

Adds an opt-in --next (alias --rc) flag to /gsd-update targeting the @next RC dist-tag (ADR #660), with a {latest,next} allowlist enforced at three layers, channel-aware version check + banner, and byte-for-byte unchanged default @latest behavior.

Closes #815

gsd-core/bin/check-latest-version.cjs

@@ -37,18 +37,64 @@ const CHECK_REASON = Object.freeze({
 
 const SEMVER_RE = /^\d+\.\d+\.\d+(?:[-+][0-9A-Za-z.-]+)?$/;
 
+// #815: the one RC channel ADR #660 sanctions, plus the stable default.
+// An allowlist (not a free string) keeps a typo from silently resolving
+// `npm view` to an empty or foreign dist-tag.
+const ALLOWED_TAGS = Object.freeze(['latest', 'next']);
+
+/**
+ * Build the `npm view` args for a dist-tag. `latest` keeps the bare package
+ * spec so the default invocation is byte-for-byte identical to before tag
+ * support existed (#815); any other allowlisted tag appends `@<tag>` so
+ * `npm view @opengsd/gsd-core@next version` resolves the RC channel (#660).
+ */
+function buildViewArgs(tag = 'latest') {
+  if (!ALLOWED_TAGS.includes(tag)) {
+    throw new RangeError(`invalid dist-tag '${tag}'; allowed: ${ALLOWED_TAGS.join(', ')}`);
+  }
+  const spec = tag === 'latest' ? PACKAGE_NAME : `${PACKAGE_NAME}@${tag}`;
+  return ['view', spec, 'version'];
+}
+
+/**
+ * Resolve the requested dist-tag from argv. Defaults to `latest` (no flag =>
+ * no behavior change). Restricted to ALLOWED_TAGS so a typo can't silently
+ * resolve to an empty/foreign tag (#815 alternative 1).
+ */
+function resolveTag(argv) {
+  let val;
+  const eq = argv.find((a) => typeof a === 'string' && a.startsWith('--tag='));
+  if (eq !== undefined) {
+    val = eq.slice('--tag='.length);
+  } else {
+    const i = argv.indexOf('--tag');
+    if (i === -1) return 'latest';
+    val = argv[i + 1];
+  }
+  if (!val || !ALLOWED_TAGS.includes(val)) {
+    throw new RangeError(
+      `invalid --tag '${val || ''}'; allowed: ${ALLOWED_TAGS.join(', ')}`,
+    );
+  }
+  return val;
+}
+
 /**
  * Pure-ish: takes an injected spawn function so tests don't actually run npm.
  * In production, defaults to execNpm() from the shell-projection seam.
  */
 function checkLatestVersion(opts = {}) {
+  const tag = opts.tag || 'latest';
+  if (!ALLOWED_TAGS.includes(tag)) {
+    throw new RangeError(`invalid dist-tag '${tag}'; allowed: ${ALLOWED_TAGS.join(', ')}`);
+  }
   // Default path routes through the shell-projection seam (execNpm owns the
   // Windows shell-flag policy and timeout default). The injection point
   // remains spawnSync-shaped for test compatibility — the adapter below
   // translates { exitCode } → { status } so the consumer logic is unchanged.
   // Bounded at 15s so a hung registry doesn't block /gsd-update (#2993 CR).
   const defaultSpawn = () => {
-    const r = execNpm(['view', PACKAGE_NAME, 'version'], { timeout: 15_000 });
+    const r = execNpm(buildViewArgs(tag), { timeout: 15_000 });
     return {
       status: r.exitCode,
       stdout: r.stdout,
@@ -90,8 +136,16 @@ function checkLatestVersion(opts = {}) {
 }
 
 function main() {
-  const json = process.argv.includes('--json');
-  const r = checkLatestVersion();
+  const argv = process.argv.slice(2);
+  const json = argv.includes('--json');
+  let tag;
+  try {
+    tag = resolveTag(argv);
+  } catch (e) {
+    process.stderr.write(`check-latest-version: ${e.message}\n`);
+    return 2;
+  }
+  const r = checkLatestVersion({ tag });
   if (json) {
     process.stdout.write(JSON.stringify(r) + '\n');
   } else if (r.ok) {
@@ -104,4 +158,4 @@ function main() {
 
 if (require.main === module) runMain(main);
 
-module.exports = { checkLatestVersion, CHECK_REASON, PACKAGE_NAME };
+module.exports = { checkLatestVersion, CHECK_REASON, PACKAGE_NAME, ALLOWED_TAGS, buildViewArgs, resolveTag };

gsd-core/workflows/help/modes/full.md

@@ -550,11 +550,12 @@ Usage: `/gsd:help --full`
 Usage: `/gsd:help debug`
 Usage: `/gsd:help --brief debug`
 
-**`/gsd:update [--sync] [--reapply]`**
+**`/gsd:update [--sync] [--reapply] [--next | --rc]`**
 Update GSD to latest version with changelog preview.
 
 - `--sync` — sync managed GSD skills across runtime roots (replaces the former `gsd-sync-skills`)
 - `--reapply` — reapply local modifications after an update (replaces the former `gsd-reapply-patches`)
+- `--next` (alias `--rc`) — install/refresh from the `@next` RC dist-tag instead of `@latest` (ADR #660); omit for the stable channel
 
 - Shows installed vs latest version comparison
 - Displays changelog entries for versions you've missed

gsd-core/workflows/update.md

@@ -75,6 +75,25 @@ If multiple runtime installs are detected and the invoking runtime cannot be det
 **If VERSION file missing (version resolves to `0.0.0`):** report the installed version as Unknown and proceed to install (treated as `0.0.0` for comparison).
 </step>
 
+<step name="parse_update_channel">
+Determine the release channel from `$ARGUMENTS`. This selects which npm dist-tag the entire update flow targets — `latest` (stable) by default, or `next` (the RC channel established by ADR #660) when the user opts in with `--next`/`--rc`:
+
+```bash
+case " $ARGUMENTS " in
+  *" --next "*|*" --rc "*)
+    TAG="next"
+    CHANNEL_LABEL="next (RC)"
+    ;;
+  *)
+    TAG="latest"
+    CHANNEL_LABEL="latest (stable)"
+    ;;
+esac
+```
+
+`TAG` is restricted to `latest`/`next` by `check-latest-version.cjs` (it rejects any other value with exit 2), so no arbitrary dist-tag can leak through. Omitting `--next`/`--rc` reproduces the prior behavior exactly: `TAG=latest`.
+</step>
+
 <step name="check_latest_version">
 Check npm for latest version via the deterministic script. **Do NOT run `npm view` or `npm search` directly** — the package name must come from the script, not from a free choice at execution time. (#2992: LLM-driven prescriptions of npm package names produced wrong-package queries; moving the package name into a script constant closes that gap.)
 
@@ -91,7 +110,7 @@ if [ -z "$GSD_DIR" ]; then
   LATEST_VERSION=""
   LATEST_REASON="no_install_detected"
 else
-  LATEST_RESULT="$(node "$GSD_DIR/gsd-core/bin/check-latest-version.cjs" --json 2>/dev/null)"
+  LATEST_RESULT="$(node "$GSD_DIR/gsd-core/bin/check-latest-version.cjs" --json --tag "$TAG" 2>/dev/null)"
   LATEST_STATUS=$?
   # #2993 CR: when node is missing or the script doesn't exist, LATEST_RESULT
   # is empty and piping it to `jq` produces a parse error on stderr while
@@ -114,7 +133,7 @@ fi
 ```text
 Couldn't check for updates (reason: {LATEST_REASON}, exit: {LATEST_STATUS}).
 
-To update manually: `npx -y --package=@opengsd/gsd-core@latest -- gsd-core --global`
+To update manually: `npx -y --package=@opengsd/gsd-core@{TAG} -- gsd-core --global`
 ```
 
 Exit.
@@ -123,6 +142,14 @@ Exit.
 <step name="compare_versions">
 Compare installed vs latest:
 
+**Only when `TAG=next`** (the user passed `--next`/`--rc`), prepend a channel banner so they know they are leaving the stable line — add this line immediately after the `**Latest:**` line in whichever output block renders:
+
+**Channel:** {CHANNEL_LABEL}
+
+On the default stable channel (`TAG=latest`), do NOT add a channel line — the output must match the prior stable behavior exactly.
+
+When `TAG=next`, the "latest" value is the release candidate published under `@next` (e.g. `1.4.0-rc.1`). Apply standard semver precedence for prereleases (`1.4.0-rc.1` is newer than `1.3.1` but older than the final `1.4.0`). Do NOT treat an `-rc.N` suffix as a dev install or as "behind" — offer it as an available update.
+
 **If installed == latest:**
 ```
 ## GSD Update
@@ -327,17 +354,17 @@ RUNTIME_FLAG="--$TARGET_RUNTIME"
 
 **If LOCAL install:**
 ```bash
-npx -y --package=@opengsd/gsd-core@latest -- gsd-core "$RUNTIME_FLAG" --local
+npx -y --package=@opengsd/gsd-core@"$TAG" -- gsd-core "$RUNTIME_FLAG" --local
 ```
 
 **If GLOBAL install:**
 ```bash
-npx -y --package=@opengsd/gsd-core@latest -- gsd-core "$RUNTIME_FLAG" --global
+npx -y --package=@opengsd/gsd-core@"$TAG" -- gsd-core "$RUNTIME_FLAG" --global
 ```
 
 **If UNKNOWN install:**
 ```bash
-npx -y --package=@opengsd/gsd-core@latest -- gsd-core --claude --global
+npx -y --package=@opengsd/gsd-core@"$TAG" -- gsd-core --claude --global
 ```
 
 Capture output. If install fails, show error and exit.