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+// A workflow node takes in and hands out typed artifacts (#1272). An artifact is a fact with a
+// revision, so "is it there" and "is it current" are two questions instead of one: a verdict carries
+// the SHA it judged, a check the SHA it ran on, a branch its head commit. The engine compares
+// revisions and refuses a stale input; it never invents a revision, and the provider named for a
+// kind is what reads the current one. Pure: no I/O, no clock, no GitHub.
+
+export const ARTIFACT_KINDS = [
+  'issue',
+  'issue.ready',
+  'branch',
+  'pr',
+  'verdict',
+  'check',
+  'risk',
+  'mergeable',
+  'merge-commit',
+  'release',
+  'doc',
+  'file',
+  'link',
+  'text',
+]
+
+// A kind that carries a name (`check:tests-ok`, `text:topic`): two of them on one card are two
+// different facts, so an unnamed one is not a spec.
+const NAMED_KINDS = new Set(['check', 'risk', 'doc', 'file', 'link', 'text'])
+
+// What the revision of each kind is. The engine compares revisions for equality; this table is
+// what a provider reads, and what a node's refusal names when it says the input moved.
+export const REVISION_RULES = {
+  issue: 'the issue number, as read',
+  'issue.ready': 'the labels and body the triage node saw',
+  branch: 'the branch head commit SHA',
+  pr: 'the pull request number and its headRefOid',
+  verdict: 'the SHA the verdict names',
+  check: 'the SHA the check ran on',
+  risk: 'the SHA the tier was computed on',
+  mergeable: 'the tip SHA it was computed against',
+  'merge-commit': 'the SHA the queue wrote to main',
+  release: 'the tag it published',
+  doc: 'the content hash of the document',
+  file: 'the content hash of the file',
+  link: 'the target the node recorded',
+  text: 'the text the node recorded',
+}
+
+// `check:tests-ok` -> `{ kind: 'check', name: 'tests-ok' }`, `issue.ready` -> `{ kind: 'issue.ready',
+// name: '' }`. Anything outside the vocabulary, a named kind without a name, or an unnamed part of
+// a named kind is not a spec: a definition that spells an artifact this way is invalid, not empty.
+export function parseArtifactSpec(spec) {
+  const raw = typeof spec === 'string' ? spec.trim() : ''
+  if (raw === '') return null
+  const cut = raw.indexOf(':')
+  const kind = cut === -1 ? raw : raw.slice(0, cut).trim()
+  const name = cut === -1 ? '' : raw.slice(cut + 1).trim()
+  if (!ARTIFACT_KINDS.includes(kind)) return null
+  if (NAMED_KINDS.has(kind)) return name === '' ? null : { kind, name }
+  return name === '' ? { kind, name: '' } : null
+}
+
+export function formatArtifactSpec(parsed) {
+  if (!parsed || !ARTIFACT_KINDS.includes(parsed.kind)) return null
+  const name = typeof parsed.name === 'string' ? parsed.name.trim() : ''
+  return name === '' ? parsed.kind : `${parsed.kind}:${name}`
+}
+
+export function isArtifactSpec(spec) {
+  return parseArtifactSpec(spec) !== null
+}
+
+// Revisions compare as text, with a SHA case-folded so `ABC1234` and `abc1234` are one revision.
+// Everything else (`1274@1519968b`, a tag, a content hash) is compared exactly.
+export function normaliseRevision(revision) {
+  if (revision === null || revision === undefined) return null
+  const text = String(revision).trim()
+  if (text === '') return null
+  return /^[0-9a-f]{6,40}$/i.test(text) ? text.toLowerCase() : text
+}
+
+export function sameRevision(a, b) {
+  const left = normaliseRevision(a)
+  return left !== null && left === normaliseRevision(b)
+}
+
+export function revisionRule(kind) {
+  return REVISION_RULES[kind] ?? null
+}
+
+// One instance of an artifact: what it is, which revision of it a node saw, and the value that
+// revision carried (a verdict's PASS / INC, a text's body). No revision, no artifact.
+export function artifact(spec, revision, extra = {}) {
+  const parsed = typeof spec === 'string' ? parseArtifactSpec(spec) : parseArtifactSpec(formatArtifactSpec(spec))
+  if (!parsed) return null
+  const at = normaliseRevision(revision)
+  if (at === null) return null
+  return {
+    spec: formatArtifactSpec(parsed),
+    kind: parsed.kind,
+    name: parsed.name,
+    revision: at,
+    value: extra.value === undefined ? null : extra.value,
+    by: extra.by === undefined ? null : extra.by,
+    at: extra.at === undefined ? null : extra.at,
+  }
+}
+
+// `check:tests-ok@abc1234` — the spelling a refusal and a card use, so a reader sees which
+// revision was present without opening the record.
+export function formatArtifact(input) {
+  if (!input || !input.spec) return null
+  return input.revision ? `${input.spec}@${input.revision}` : input.spec
+}
+
+export function sameArtifact(a, b) {
+  return Boolean(a && b && a.spec === b.spec) && sameRevision(a.revision, b.revision)
+}
+
+// Present is not current (#1272). The caller re-reads what produces the artifact and hands in the
+// revision that source holds now; a fact nobody could read is not a match either, so it refuses
+// with `unreadable` rather than pass on a guess (#1211).
+export function freshness(input, currentRevision) {
+  const now = normaliseRevision(currentRevision)
+  if (!input) return { fresh: false, reason: 'missing', have: null, now }
+  if (now === null) return { fresh: false, reason: 'unreadable', have: input.revision ?? null, now: null }
+  const fresh = sameRevision(input.revision, now)
+  return { fresh, reason: fresh ? 'current' : 'stale', have: input.revision ?? null, now }
+}
+
+export function artifactsBySpec(list) {
+  const map = {}
+  for (const item of Array.isArray(list) ? list : []) {
+    if (item && item.spec) map[item.spec] = item
+  }
+  return map
+}
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+// The `blank` preset (#1272): three nodes, one Bot each, no guards, no repository. It is here as
+// proof that a workflow is data — nothing in src/shared/workflow.js names these ids, and the same
+// JSON dropped in the workspace as `workflows/blank.json` is the whole definition.
+
+export const blankWorkflow = Object.freeze({
+  id: 'blank',
+  name: 'Blank',
+  version: 1,
+  inputs: ['text:topic'],
+  deliverables: ['link:published'],
+  nodes: [
+    {
+      id: 'draft',
+      name: 'Draft',
+      bot: 'Writer',
+      inputs: ['text:topic'],
+      outputs: ['text:draft'],
+      guards: [],
+      refusal: '{node} cannot start: it needs {spec} and has none.',
+    },
+    {
+      id: 'review',
+      name: 'Review',
+      bot: 'Editor',
+      inputs: ['text:draft'],
+      outputs: ['text:edited'],
+      guards: [],
+      refusal: '{node} cannot start: its input {input} is missing or stale.',
+    },
+    {
+      id: 'publish',
+      name: 'Publish',
+      bot: 'Publisher',
+      inputs: ['text:edited'],
+      outputs: ['link:published'],
+      guards: [],
+      refusal: '{node} cannot start: it needs {spec} and has none.',
+    },
+  ],
+  edges: [
+    { from: 'draft.text:draft', to: 'review.text:draft' },
+    { from: 'review.text:edited', to: 'publish.text:edited' },
+  ],
+  loops: [],
+})
+
+// The Bots the preset names, so a caller can pass them as the team without inventing a roster.
+export const BLANK_TEAM = Object.freeze(['Writer', 'Editor', 'Publisher'])