diff --git a/.github/workflows/claim.yml b/.github/workflows/claim.yml
new file mode 100644
index 0000000..fa69c68
--- /dev/null
+++ b/.github/workflows/claim.yml
@@ -0,0 +1,53 @@
+# `/claim` and `/unclaim` on issues (CONTRIBUTING.md, "Before you start: claim an issue"), and a
+# daily sweep that frees claims with no visible progress for 14 days. A pull request that
+# references an issue (`Closes #N`, `<summary> (#N)`) claims it too. The logic is in
+# scripts/claim/claim.js (tested in ci.yml).
+name: Claim
+
+on:
+  issue_comment:
+    types: [created]
+  # pull_request_target so PRs from forks can label and assign. It runs the base branch's
+  # scripts/claim and only reads the PR's title, body and author; the PR's code is never checked out.
+  pull_request_target:
+    types: [opened, reopened]
+  schedule:
+    - cron: '17 5 * * *'
+  workflow_dispatch:
+
+permissions:
+  contents: read # to check out scripts/claim
+  issues: write
+  pull-requests: read
+
+# One run at a time per issue, so two simultaneous /claim comments can't both win.
+concurrency:
+  group: claim-${{ github.event.issue.number || github.event.pull_request.number || 'sweep' }}
+  cancel-in-progress: false
+
+jobs:
+  claim:
+    name: Claim bot
+    runs-on: ubuntu-24.04
+    timeout-minutes: 10
+    if: >-
+      github.event_name != 'issue_comment' ||
+      (!github.event.issue.pull_request && github.event.comment.user.type != 'Bot' &&
+      (startsWith(github.event.comment.body, '/claim') || startsWith(github.event.comment.body, '/unclaim')))
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          sparse-checkout: scripts/claim
+      - uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        with:
+          script: |
+            const claim = require('./scripts/claim/claim.js');
+            if (context.eventName === 'issue_comment') {
+              await claim.handleComment({ github, context });
+            } else if (context.eventName === 'pull_request_target') {
+              const claimed = await claim.handlePull({ github, context });
+              core.info(`Claimed: ${claimed.join(', ') || 'none'}`);
+            } else {
+              const released = await claim.sweep({ github, context });
+              core.info(`Released: ${released.join(', ') || 'none'}`);
+            }
diff --git a/scripts/claim/claim.js b/scripts/claim/claim.js
new file mode 100644
index 0000000..38a5933
--- /dev/null
+++ b/scripts/claim/claim.js
@@ -0,0 +1,414 @@
+// The /claim bot's logic, used by .github/workflows/claim.yml through actions/github-script.
+// Everything takes the github-script `github` client and `context`, so the tests can pass fakes.
+'use strict';
+
+// CONTRIBUTING.md, "Before you start: claim an issue": a claimed issue is assigned and labelled
+// `claimed`; `in progress` marks the core team's own work and can't be claimed; contributors pick
+// issues labelled `help wanted` or `good first issue`; no visible progress for 14 days frees it.
+const LABEL = 'claimed';
+const LABEL_COLOR = '0052cc';
+const LABEL_DESCRIPTION = 'Assigned to a contributor; see CONTRIBUTING.md';
+const CORE = 'in progress';
+const OPEN = ['help wanted', 'good first issue'];
+const CLAIM_DAYS = 14;
+const DAY = 24 * 3600 * 1000;
+
+function parseCommand(body) {
+  const text = String(body || '').trimStart();
+  if (/^\/claim(\s|$)/.test(text)) return 'claim';
+  if (/^\/unclaim(\s|$)/.test(text)) return 'unclaim';
+  return null;
+}
+
+function fmt(date) {
+  return new Date(date).toISOString().slice(0, 16).replace('T', ' ') + ' UTC';
+}
+
+function repoArgs(context) {
+  return { owner: context.repo.owner, repo: context.repo.repo };
+}
+
+async function isMaintainer(github, context, login, cache) {
+  if (login === context.repo.owner) return true;
+  if (cache && cache.has(login)) return cache.get(login);
+  let result = false;
+  try {
+    const { data } = await github.rest.repos.getCollaboratorPermissionLevel({
+      ...repoArgs(context),
+      username: login,
+    });
+    result =
+      ['admin', 'write', 'maintain'].includes(data.permission) ||
+      ['admin', 'maintain', 'write'].includes(data.role_name);
+  } catch (e) {
+    result = false;
+  }
+  if (cache) cache.set(login, result);
+  return result;
+}
+
+async function ensureLabel(github, context) {
+  try {
+    await github.rest.issues.getLabel({ ...repoArgs(context), name: LABEL });
+  } catch (e) {
+    if (e.status !== 404) throw e;
+    try {
+      await github.rest.issues.createLabel({
+        ...repoArgs(context),
+        name: LABEL,
+        color: LABEL_COLOR,
+        description: LABEL_DESCRIPTION,
+      });
+    } catch (e2) {
+      if (e2.status !== 422) throw e2; // created meanwhile
+    }
+  }
+}
+
+// When the label was last added, from the timeline; the issue's update time if it can't be found.
+async function labeledAt(github, context, issue, timeline) {
+  const events = timeline || (await getTimeline(github, context, issue.number));
+  let at = null;
+  for (const ev of events) {
+    if (ev.event === 'labeled' && ev.label && ev.label.name === LABEL) at = ev.created_at;
+  }
+  return new Date(at || issue.updated_at).getTime();
+}
+
+function getTimeline(github, context, number) {
+  return github.paginate(github.rest.issues.listEventsForTimeline, {
+    ...repoArgs(context),
+    issue_number: number,
+    per_page: 100,
+  });
+}
+
+// Open pull requests that mention the issue, from the timeline's cross-references.
+function linkedPulls(timeline) {
+  const seen = new Map();
+  for (const ev of timeline) {
+    const src = ev.event === 'cross-referenced' && ev.source && ev.source.issue;
+    if (src && src.pull_request && src.state === 'open') seen.set(src.number, src);
+  }
+  return [...seen.values()];
+}
+
+async function lastPush(github, context, pr) {
+  const { data } = await github.rest.pulls.get({ ...repoArgs(context), pull_number: pr.number });
+  const { data: commit } = await github.rest.repos.getCommit({
+    ...repoArgs(context),
+    ref: data.head.sha,
+  });
+  return new Date(commit.commit.committer.date).getTime();
+}
+
+// Where a claimed issue stands: when it lapses, and whether it is free to release now.
+async function claimStatus(github, context, issue, now) {
+  const timeline = await getTimeline(github, context, issue.number);
+  const since = await labeledAt(github, context, issue, timeline);
+  const pulls = linkedPulls(timeline);
+  if (pulls.length === 0) {
+    const expires = since + CLAIM_DAYS * DAY;
+    return { pulls, since, expires, release: now >= expires, reason: 'no PR' };
+  }
+  let newest = since;
+  for (const pr of pulls) newest = Math.max(newest, await lastPush(github, context, pr));
+  const expires = newest + CLAIM_DAYS * DAY;
+  return { pulls, since, expires, release: now >= expires, reason: 'idle PR' };
+}
+
+async function react(github, context, content) {
+  await github.rest.reactions.createForIssueComment({
+    ...repoArgs(context),
+    comment_id: context.payload.comment.id,
+    content,
+  });
+}
+
+async function reply(github, context, body) {
+  await github.rest.issues.createComment({
+    ...repoArgs(context),
+    issue_number: context.payload.issue.number,
+    body,
+  });
+}
+
+function labelNames(issue) {
+  return (issue.labels || []).map((l) => (typeof l === 'string' ? l : l.name));
+}
+
+function hasLabel(issue, name = LABEL) {
+  return labelNames(issue).includes(name);
+}
+
+// Open to contributors: labelled `help wanted` or `good first issue`, and not the core team's.
+function claimable(issue) {
+  const names = labelNames(issue);
+  return !names.includes(CORE) && OPEN.some((n) => names.includes(n));
+}
+
+async function release(github, context, issue, assignees) {
+  if (assignees.length) {
+    await github.rest.issues.removeAssignees({
+      ...repoArgs(context),
+      issue_number: issue.number,
+      assignees,
+    });
+  }
+  try {
+    await github.rest.issues.removeLabel({
+      ...repoArgs(context),
+      issue_number: issue.number,
+      name: LABEL,
+    });
+  } catch (e) {
+    if (e.status !== 404) throw e;
+  }
+}
+
+async function claim(github, context, now) {
+  const issue = context.payload.issue;
+  const user = context.payload.comment.user.login;
+  const n = issue.number;
+  const cache = new Map();
+  const assignees = (issue.assignees || []).map((a) => a.login);
+
+  if (assignees.includes(user)) {
+    await react(github, context, '+1'); // already theirs
+    return;
+  }
+
+  if (hasLabel(issue, CORE)) {
+    await react(github, context, 'eyes');
+    await reply(github, context, `The core team is working on this one (\`${CORE}\`), so it can't be claimed.`);
+    return;
+  }
+  if (!claimable(issue) && !(await isMaintainer(github, context, user, cache))) {
+    await react(github, context, 'eyes');
+    await reply(
+      github,
+      context,
+      `Only issues labelled \`help wanted\` or \`good first issue\` can be claimed, @${user}. ` +
+        'Say here what you would like to do and a maintainer will open it up or assign it to you.',
+    );
+    return;
+  }
+
+  // Someone else is assigned: theirs unless the claim has lapsed (never for a maintainer).
+  let held = assignees.length > 0 || hasLabel(issue);
+  let status = null;
+  if (held) {
+    let maintained = false;
+    for (const a of assignees) maintained = maintained || (await isMaintainer(github, context, a, cache));
+    if (!maintained) {
+      status = await claimStatus(github, context, issue, now);
+      if (status.release) held = false;
+    }
+    if (held) {
+      await react(github, context, 'eyes');
+      const who = assignees.length ? assignees.map((a) => '@' + a).join(', ') + ' has' : 'Someone has';
+      const when = maintained || !status ? '' : ` The claim lapses on ${fmt(status.expires)} unless there's progress.`;
+      await reply(github, context, `${who} claimed this already.${when}`);
+      return;
+    }
+  } else {
+    // Not claimed, but someone's open PR may already cover it.
+    const timeline = await getTimeline(github, context, n);
+    const other = linkedPulls(timeline).find((p) => p.user && p.user.login !== user);
+    if (other) {
+      await react(github, context, 'eyes');
+      await reply(github, context, `#${other.number} already covers this one.`);
+      return;
+    }
+  }
+
+  // Free (or lapsed): hand it to the commenter. Clear a lapsed claimant first.
+  if (assignees.length) {
+    await github.rest.issues.removeAssignees({ ...repoArgs(context), issue_number: n, assignees });
+  }
+  await ensureLabel(github, context);
+  await github.rest.issues.addLabels({ ...repoArgs(context), issue_number: n, labels: [LABEL] });
+  try {
+    await github.rest.issues.addAssignees({
+      ...repoArgs(context),
+      issue_number: n,
+      assignees: [user],
+    });
+  } catch (e) {
+    // Assignment can be refused; the label and the reply naming them still stand.
+  }
+  await react(github, context, '+1');
+  await reply(
+    github,
+    context,
+    `Claimed by @${user}. Please open a draft PR early with \`Closes #${n}\`; the claim lapses after ${CLAIM_DAYS} days without visible progress. \`/unclaim\` releases it.`,
+  );
+}
+
+async function unclaim(github, context) {
+  const issue = context.payload.issue;
+  const user = context.payload.comment.user.login;
+  const assignees = (issue.assignees || []).map((a) => a.login);
+  if (!hasLabel(issue) && assignees.length === 0) {
+    await react(github, context, '+1'); // nothing to release
+    return;
+  }
+  const allowed = assignees.includes(user) || (await isMaintainer(github, context, user));
+  if (!allowed) {
+    await react(github, context, 'eyes');
+    await reply(github, context, `Only the person who claimed this, or a maintainer, can release it, @${user}.`);
+    return;
+  }
+  await release(github, context, issue, assignees);
+  await react(github, context, '+1');
+  await reply(github, context, `Released. This one is free again, so anyone can \`/claim\` it.`);
+}
+
+// The comment event.
+async function handleComment({ github, context, now = Date.now() }) {
+  const { issue, comment } = context.payload;
+  if (!issue || issue.pull_request || !comment) return 'skip';
+  if (issue.state !== 'open' || issue.locked) return 'skip';
+  if (comment.user.type === 'Bot' || comment.user.login.endsWith('[bot]')) return 'skip';
+  const cmd = parseCommand(comment.body);
+  if (!cmd) return 'skip';
+  if (cmd === 'claim') await claim(github, context, now);
+  else await unclaim(github, context);
+  return cmd;
+}
+
+// Issue numbers a PR claims: `#N` in its title (`<summary> (#N)`) and closing keywords in its body.
+const MAX_REFS = 5;
+function referencedIssues(title, body) {
+  const found = new Set();
+  for (const m of String(title || '').matchAll(/(?:^|[\s(])#(\d{1,7})\b/g)) found.add(Number(m[1]));
+  const closing = /\b(?:close[sd]?|fix(?:e[sd])?|resolve[sd]?)\s*:?\s+#(\d{1,7})\b/gi;
+  for (const m of String(body || '').matchAll(closing)) found.add(Number(m[1]));
+  return [...found].filter((n) => n > 0).slice(0, MAX_REFS);
+}
+
+// A pull request was opened: it claims each open-for-contributors issue it references that nobody
+// holds yet. The core team's PRs claim nothing (their issues carry `in progress` instead).
+async function handlePull({ github, context }) {
+  const pull = context.payload.pull_request;
+  if (!pull || pull.state !== 'open') return [];
+  const author = pull.user && pull.user.login;
+  if (!author || pull.user.type === 'Bot' || author.endsWith('[bot]')) return [];
+  if (await isMaintainer(github, context, author)) return [];
+  const claimed = [];
+  for (const n of referencedIssues(pull.title, pull.body)) {
+    if (n === pull.number) continue;
+    let issue;
+    try {
+      ({ data: issue } = await github.rest.issues.get({ ...repoArgs(context), issue_number: n }));
+    } catch (e) {
+      if (e.status === 404 || e.status === 410) continue;
+      throw e;
+    }
+    if (issue.pull_request || issue.state !== 'open' || issue.locked) continue;
+    const assignees = (issue.assignees || []).map((a) => a.login);
+    if (assignees.includes(author)) {
+      if (!hasLabel(issue)) {
+        await ensureLabel(github, context);
+        await github.rest.issues.addLabels({ ...repoArgs(context), issue_number: n, labels: [LABEL] });
+      }
+      continue;
+    }
+    if (hasLabel(issue, CORE)) {
+      await github.rest.issues.createComment({
+        ...repoArgs(context),
+        issue_number: pull.number,
+        body: `#${n} is being worked on by the core team (\`${CORE}\`). Please ask on the issue before going further.`,
+      });
+      continue;
+    }
+    if (assignees.length || hasLabel(issue)) {
+      const who = assignees.length ? assignees.map((a) => '@' + a).join(', ') : 'someone else';
+      await github.rest.issues.createComment({
+        ...repoArgs(context),
+        issue_number: pull.number,
+        body: `#${n} is already claimed by ${who}. If this PR duplicates their work, please close it or offer to help there.`,
+      });
+      continue;
+    }
+    // An older open PR for the issue wins (lowest number), even if it never recorded its claim.
+    const timeline = await getTimeline(github, context, n);
+    const older = linkedPulls(timeline).find((p) => p.number < pull.number && p.user && p.user.login !== author);
+    if (older) {
+      await github.rest.issues.createComment({
+        ...repoArgs(context),
+        issue_number: pull.number,
+        body: `#${older.number} claimed #${n} first (the lowest-numbered open PR wins). Please close this one or offer to help there.`,
+      });
+      continue;
+    }
+    if (!claimable(issue)) {
+      await github.rest.issues.createComment({
+        ...repoArgs(context),
+        issue_number: pull.number,
+        body: `#${n} isn't open for contributors yet (no \`help wanted\` or \`good first issue\` label), so this PR doesn't claim it. A maintainer will reply on the issue.`,
+      });
+      continue;
+    }
+    await ensureLabel(github, context);
+    await github.rest.issues.addLabels({ ...repoArgs(context), issue_number: n, labels: [LABEL] });
+    try {
+      await github.rest.issues.addAssignees({ ...repoArgs(context), issue_number: n, assignees: [author] });
+    } catch (e) {
+      // Assignment can be refused; the label and the comment naming them still stand.
+    }
+    await github.rest.issues.createComment({
+      ...repoArgs(context),
+      issue_number: n,
+      body: `Claimed by @${author} through #${pull.number}. The claim lapses after ${CLAIM_DAYS} days without pushes.`,
+    });
+    claimed.push(n);
+  }
+  return claimed;
+}
+
+// The daily sweep over open issues labelled `claimed`.
+async function sweep({ github, context, now = Date.now() }) {
+  const issues = await github.paginate(github.rest.issues.listForRepo, {
+    ...repoArgs(context),
+    state: 'open',
+    labels: LABEL,
+    per_page: 100,
+  });
+  const cache = new Map();
+  const released = [];
+  for (const issue of issues) {
+    if (issue.pull_request || issue.locked || hasLabel(issue, CORE)) continue;
+    const assignees = (issue.assignees || []).map((a) => a.login);
+    let skip = false;
+    for (const a of assignees) skip = skip || (await isMaintainer(github, context, a, cache));
+    if (skip) continue;
+    const status = await claimStatus(github, context, issue, now);
+    if (!status.release) continue;
+    await release(github, context, issue, assignees);
+    await github.rest.issues.createComment({
+      ...repoArgs(context),
+      issue_number: issue.number,
+      body:
+        status.reason === 'no PR'
+          ? `No pull request showed up within ${CLAIM_DAYS} days, so this one is free again. Anyone can \`/claim\` it.`
+          : `Nothing has been pushed for ${CLAIM_DAYS} days, so this one is free again. Anyone can \`/claim\` it.`,
+    });
+    released.push(issue.number);
+  }
+  return released;
+}
+
+module.exports = {
+  LABEL,
+  CORE,
+  claimable,
+  parseCommand,
+  referencedIssues,
+  isMaintainer,
+  linkedPulls,
+  claimStatus,
+  handleComment,
+  handlePull,
+  sweep,
+};
diff --git a/scripts/claim/claim.test.js b/scripts/claim/claim.test.js
new file mode 100644
index 0000000..ed73fc1
--- /dev/null
+++ b/scripts/claim/claim.test.js
@@ -0,0 +1,331 @@
+'use strict';
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const claim = require('./claim.js');
+
+const NOW = Date.parse('2026-10-16T12:00:00Z');
+const H = 3600 * 1000;
+const D = 24 * H;
+const ago = (ms) => new Date(NOW - ms).toISOString();
+
+// A fake github-script client that records writes. `world` describes the repo.
+function fake(world = {}) {
+  const calls = [];
+  const rec = (name) => async (args) => {
+    calls.push([name, args]);
+    if (world.fail && world.fail[name]) throw Object.assign(new Error(name), { status: world.fail[name] });
+    return { data: {} };
+  };
+  const github = {
+    paginate: async (fn, args) => (await fn(args)).data,
+    rest: {
+      repos: {
+        getCollaboratorPermissionLevel: async ({ username }) => {
+          const permission = (world.perms || {})[username] || 'none';
+          return { data: { permission } };
+        },
+        getCommit: async () => ({ data: { commit: { committer: { date: world.pushed || ago(H) } } } }),
+      },
+      pulls: { get: async () => ({ data: { head: { sha: 'abc' } } }) },
+      reactions: { createForIssueComment: rec('react') },
+      issues: {
+        getLabel: async () => {
+          if (world.labelMissing) throw Object.assign(new Error('nf'), { status: 404 });
+          return { data: {} };
+        },
+        createLabel: rec('createLabel'),
+        addLabels: rec('addLabels'),
+        removeLabel: rec('removeLabel'),
+        addAssignees: rec('addAssignees'),
+        removeAssignees: rec('removeAssignees'),
+        createComment: rec('comment'),
+        listForRepo: async () => ({ data: world.issues || [] }),
+        get: async ({ issue_number }) => {
+          const found = (world.byNumber || {})[issue_number];
+          if (!found) throw Object.assign(new Error('nf'), { status: 404 });
+          return { data: found };
+        },
+        listEventsForTimeline: async () => ({ data: world.timeline || [] }),
+      },
+    },
+  };
+  return { github, calls };
+}
+
+const names = (calls) => calls.map((c) => c[0]);
+const find = (calls, n) => calls.find((c) => c[0] === n);
+const labeled = (at) => ({ event: 'labeled', label: { name: 'claimed' }, created_at: at });
+const pr = (number, login = 'other', state = 'open') => ({
+  event: 'cross-referenced',
+  source: { issue: { number, state, pull_request: {}, user: { login } } },
+});
+
+function ctx(body, { assignees = [], labels = ['help wanted'], user = 'alice', extra = {} } = {}) {
+  return {
+    repo: { owner: 'tangency-labs', repo: 'fieldcraft' },
+    payload: {
+      issue: {
+        number: 7,
+        state: 'open',
+        locked: false,
+        updated_at: ago(1000 * H),
+        assignees: assignees.map((login) => ({ login })),
+        labels: labels.map((name) => ({ name })),
+        ...extra,
+      },
+      comment: { id: 99, body, user: { login: user, type: 'User' } },
+    },
+  };
+}
+
+test('parseCommand', () => {
+  assert.equal(claim.parseCommand('/claim'), 'claim');
+  assert.equal(claim.parseCommand('  /claim please'), 'claim');
+  assert.equal(claim.parseCommand('/unclaim'), 'unclaim');
+  assert.equal(claim.parseCommand('/claimed'), null);
+  assert.equal(claim.parseCommand('I would /claim this'), null);
+  assert.equal(claim.parseCommand(undefined), null);
+});
+
+test('claim on a free issue assigns, labels, reacts and replies', async () => {
+  const { github, calls } = fake({ labelMissing: true });
+  assert.equal(await claim.handleComment({ github, context: ctx('/claim'), now: NOW }), 'claim');
+  assert.deepEqual(find(calls, 'addAssignees')[1].assignees, ['alice']);
+  assert.deepEqual(find(calls, 'addLabels')[1].labels, ['claimed']);
+  assert.equal(find(calls, 'createLabel')[1].color, '0052cc');
+  assert.equal(find(calls, 'react')[1].content, '+1');
+  assert.match(find(calls, 'comment')[1].body, /^Claimed by @alice\. .*`Closes #7`.*14 days/);
+});
+
+test('claim still labels and replies when assignment is refused', async () => {
+  const { github, calls } = fake({ fail: { addAssignees: 422 } });
+  await claim.handleComment({ github, context: ctx('/claim'), now: NOW });
+  assert.ok(find(calls, 'addLabels'));
+  assert.match(find(calls, 'comment')[1].body, /@alice/);
+});
+
+test('claim by the current claimant is a quiet thumbs up', async () => {
+  const { github, calls } = fake();
+  await claim.handleComment({ github, context: ctx('/claim', { assignees: ['alice'], labels: ['help wanted', 'claimed'] }), now: NOW });
+  assert.deepEqual(names(calls), ['react']);
+});
+
+test('claim on an issue claimed by someone else names them and when it lapses', async () => {
+  const { github, calls } = fake({ timeline: [labeled(ago(10 * H))] });
+  await claim.handleComment({ github, context: ctx('/claim', { assignees: ['bob'], labels: ['help wanted', 'claimed'] }), now: NOW });
+  assert.equal(find(calls, 'react')[1].content, 'eyes');
+  const body = find(calls, 'comment')[1].body;
+  assert.match(body, /@bob/);
+  assert.match(body, /2026-10-30 02:00 UTC/); // 10 h ago + 14 days
+  assert.equal(find(calls, 'addAssignees'), undefined);
+});
+
+test('a lapsed claim is taken over', async () => {
+  const { github, calls } = fake({ timeline: [labeled(ago(15 * D))] });
+  await claim.handleComment({ github, context: ctx('/claim', { assignees: ['bob'], labels: ['help wanted', 'claimed'] }), now: NOW });
+  assert.deepEqual(find(calls, 'removeAssignees')[1].assignees, ['bob']);
+  assert.deepEqual(find(calls, 'addAssignees')[1].assignees, ['alice']);
+});
+
+test('a claim with a recent PR is not taken over', async () => {
+  const { github, calls } = fake({ timeline: [labeled(ago(30 * D)), pr(50, 'bob')], pushed: ago(2 * H) });
+  await claim.handleComment({ github, context: ctx('/claim', { assignees: ['bob'], labels: ['help wanted', 'claimed'] }), now: NOW });
+  assert.equal(find(calls, 'addAssignees'), undefined);
+});
+
+test('a maintainer\'s claim is never taken over', async () => {
+  const { github, calls } = fake({ timeline: [labeled(ago(500 * H))], perms: { carol: 'write' } });
+  await claim.handleComment({ github, context: ctx('/claim', { assignees: ['carol'], labels: ['help wanted', 'claimed'] }), now: NOW });
+  assert.equal(find(calls, 'addAssignees'), undefined);
+  assert.equal(find(calls, 'react')[1].content, 'eyes');
+});
+
+test('an unclaimed issue with someone else\'s open PR points at the PR', async () => {
+  const { github, calls } = fake({ timeline: [pr(42, 'bob')] });
+  await claim.handleComment({ github, context: ctx('/claim'), now: NOW });
+  assert.equal(find(calls, 'addAssignees'), undefined);
+  assert.match(find(calls, 'comment')[1].body, /#42/);
+});
+
+test('bots, locked issues, closed issues, PRs and other comments are ignored', async () => {
+  const { github, calls } = fake();
+  const bot = ctx('/claim');
+  bot.payload.comment.user = { login: 'dependabot[bot]', type: 'Bot' };
+  assert.equal(await claim.handleComment({ github, context: bot, now: NOW }), 'skip');
+  assert.equal(await claim.handleComment({ github, context: ctx('/claim', { extra: { locked: true } }), now: NOW }), 'skip');
+  assert.equal(await claim.handleComment({ github, context: ctx('/claim', { extra: { state: 'closed' } }), now: NOW }), 'skip');
+  assert.equal(await claim.handleComment({ github, context: ctx('/claim', { extra: { pull_request: {} } }), now: NOW }), 'skip');
+  assert.equal(await claim.handleComment({ github, context: ctx('hello'), now: NOW }), 'skip');
+  assert.equal(calls.length, 0);
+});
+
+test('unclaim by the claimant releases', async () => {
+  const { github, calls } = fake();
+  await claim.handleComment({ github, context: ctx('/unclaim', { assignees: ['alice'], labels: ['help wanted', 'claimed'] }), now: NOW });
+  assert.deepEqual(find(calls, 'removeAssignees')[1].assignees, ['alice']);
+  assert.equal(find(calls, 'removeLabel')[1].name, 'claimed');
+});
+
+test('unclaim by a maintainer releases, by a stranger does not', async () => {
+  let w = fake({ perms: { carol: 'admin' } });
+  await claim.handleComment({ github: w.github, context: ctx('/unclaim', { user: 'carol', assignees: ['bob'], labels: ['help wanted', 'claimed'] }), now: NOW });
+  assert.ok(find(w.calls, 'removeLabel'));
+  w = fake();
+  await claim.handleComment({ github: w.github, context: ctx('/unclaim', { user: 'mallory', assignees: ['bob'], labels: ['help wanted', 'claimed'] }), now: NOW });
+  assert.equal(find(w.calls, 'removeLabel'), undefined);
+  assert.equal(find(w.calls, 'react')[1].content, 'eyes');
+});
+
+const issue = (number, assignees = ['bob'], extra = []) => ({
+  number,
+  locked: false,
+  updated_at: ago(1000 * H),
+  assignees: assignees.map((login) => ({ login })),
+  labels: [{ name: 'claimed' }, ...extra.map((name) => ({ name }))],
+});
+const repo = { owner: 'tangency-labs', repo: 'fieldcraft' };
+
+test('sweep releases a claim older than 14 days with no PR', async () => {
+  const { github, calls } = fake({ issues: [issue(7)], timeline: [labeled(ago(15 * D))] });
+  assert.deepEqual(await claim.sweep({ github, context: { repo }, now: NOW }), [7]);
+  assert.ok(find(calls, 'removeLabel'));
+  assert.deepEqual(find(calls, 'removeAssignees')[1].assignees, ['bob']);
+  assert.match(find(calls, 'comment')[1].body, /free again/);
+});
+
+test('sweep keeps a young claim and a claim with a fresh PR, using the latest label time', async () => {
+  let w = fake({ issues: [issue(7)], timeline: [labeled(ago(30 * D)), labeled(ago(5 * D))] });
+  assert.deepEqual(await claim.sweep({ github: w.github, context: { repo }, now: NOW }), []);
+  w = fake({ issues: [issue(7)], timeline: [labeled(ago(30 * D)), pr(9)], pushed: ago(3 * D) });
+  assert.deepEqual(await claim.sweep({ github: w.github, context: { repo }, now: NOW }), []);
+});
+
+test('sweep releases a claim whose PR has been idle for 14 days', async () => {
+  const w = fake({ issues: [issue(7)], timeline: [labeled(ago(30 * D)), pr(9)], pushed: ago(15 * D) });
+  assert.deepEqual(await claim.sweep({ github: w.github, context: { repo }, now: NOW }), [7]);
+  assert.match(find(w.calls, 'comment')[1].body, /14 days/);
+});
+
+test('sweep ignores a closed PR', async () => {
+  const w = fake({ issues: [issue(7)], timeline: [labeled(ago(15 * D)), pr(9, 'other', 'closed')] });
+  assert.deepEqual(await claim.sweep({ github: w.github, context: { repo }, now: NOW }), [7]);
+});
+
+test('sweep never touches core-team or maintainer-claimed issues', async () => {
+  const w = fake({
+    issues: [issue(1, ['bob'], ['in progress']), issue(2, ['carol']), issue(3, ['bob', 'carol'])],
+    timeline: [labeled(ago(900 * H))],
+    perms: { carol: 'write' },
+  });
+  assert.deepEqual(await claim.sweep({ github: w.github, context: { repo }, now: NOW }), []);
+  assert.equal(w.calls.length, 0);
+});
+
+test('sweep is idempotent: a released issue is no longer listed', async () => {
+  const world = { issues: [issue(7)], timeline: [labeled(ago(15 * D))] };
+  const w = fake(world);
+  assert.deepEqual(await claim.sweep({ github: w.github, context: { repo }, now: NOW }), [7]);
+  world.issues = [];
+  assert.deepEqual(await claim.sweep({ github: w.github, context: { repo }, now: NOW }), []);
+});
+
+test('referencedIssues reads the title and closing keywords, capped', () => {
+  assert.deepEqual(claim.referencedIssues('Fillet: chain (#123)', 'Fixes #9, closes: #10, see #11'), [123, 9, 10]);
+  assert.deepEqual(claim.referencedIssues('no refs', 'mentions #4 only'), []);
+  assert.deepEqual(claim.referencedIssues('#1 #2 #3 #4 #5 #6 #7', ''), [1, 2, 3, 4, 5]);
+  assert.deepEqual(claim.referencedIssues(undefined, null), []);
+});
+
+const openIssue = (number, assignees = [], labels = ['help wanted']) => ({
+  number,
+  state: 'open',
+  locked: false,
+  assignees: assignees.map((login) => ({ login })),
+  labels: labels.map((name) => ({ name })),
+});
+const pullCtx = (number, title, body = '', login = 'alice') => ({
+  repo,
+  payload: { pull_request: { number, state: 'open', title, body, user: { login, type: 'User' } } },
+});
+
+test('a PR referencing a free issue claims it for the author', async () => {
+  const { github, calls } = fake({ byNumber: { 7: openIssue(7) } });
+  assert.deepEqual(await claim.handlePull({ github, context: pullCtx(50, 'Thing (#7)') }), [7]);
+  assert.deepEqual(find(calls, 'addAssignees')[1], { ...repo, issue_number: 7, assignees: ['alice'] });
+  assert.deepEqual(find(calls, 'addLabels')[1].labels, ['claimed']);
+  assert.match(find(calls, 'comment')[1].body, /Claimed by @alice through #50/);
+});
+
+test('a PR on an issue someone else holds comments on the PR and changes nothing', async () => {
+  const { github, calls } = fake({ byNumber: { 7: openIssue(7, ['bob'], ['help wanted', 'claimed']) } });
+  assert.deepEqual(await claim.handlePull({ github, context: pullCtx(50, 'Thing (#7)') }), []);
+  assert.equal(find(calls, 'addAssignees'), undefined);
+  const c = find(calls, 'comment')[1];
+  assert.equal(c.issue_number, 50);
+  assert.match(c.body, /@bob/);
+});
+
+test('the lowest-numbered open PR wins an unrecorded claim', async () => {
+  const { github, calls } = fake({ byNumber: { 7: openIssue(7) }, timeline: [pr(42, 'bob')] });
+  assert.deepEqual(await claim.handlePull({ github, context: pullCtx(50, 'Thing (#7)') }), []);
+  assert.match(find(calls, 'comment')[1].body, /#42 claimed #7 first/);
+});
+
+test('the claimant\'s own PR just makes sure the label is there', async () => {
+  const { github, calls } = fake({ byNumber: { 7: openIssue(7, ['alice']) } });
+  assert.deepEqual(await claim.handlePull({ github, context: pullCtx(50, 'Thing (#7)') }), []);
+  assert.deepEqual(names(calls), ['addLabels']);
+});
+
+test('PRs from bots, references to PRs, closed and missing issues are ignored', async () => {
+  const w = fake({
+    byNumber: { 7: { ...openIssue(7), pull_request: {} }, 8: { ...openIssue(8), state: 'closed' } },
+  });
+  assert.deepEqual(await claim.handlePull({ github: w.github, context: pullCtx(50, 'x (#7) (#8) (#9)') }), []);
+  const bot = pullCtx(51, 'x (#1)');
+  bot.payload.pull_request.user = { login: 'dependabot[bot]', type: 'Bot' };
+  assert.deepEqual(await claim.handlePull({ github: w.github, context: bot }), []);
+  assert.equal(w.calls.length, 0);
+});
+
+test('an issue the core team holds (`in progress`) cannot be claimed', async () => {
+  const { github, calls } = fake();
+  await claim.handleComment({ github, context: ctx('/claim', { labels: ['help wanted', 'in progress'] }), now: NOW });
+  assert.equal(find(calls, 'addAssignees'), undefined);
+  assert.match(find(calls, 'comment')[1].body, /core team/);
+});
+
+test('only help wanted / good first issue issues can be claimed, except by a maintainer', async () => {
+  let w = fake();
+  await claim.handleComment({ github: w.github, context: ctx('/claim', { labels: ['bug'] }), now: NOW });
+  assert.equal(find(w.calls, 'addAssignees'), undefined);
+  assert.match(find(w.calls, 'comment')[1].body, /help wanted/);
+  w = fake();
+  await claim.handleComment({ github: w.github, context: ctx('/claim', { labels: ['good first issue'] }), now: NOW });
+  assert.ok(find(w.calls, 'addAssignees'));
+  w = fake({ perms: { carol: 'write' } });
+  await claim.handleComment({ github: w.github, context: ctx('/claim', { user: 'carol', labels: [] }), now: NOW });
+  assert.deepEqual(find(w.calls, 'addAssignees')[1].assignees, ['carol']);
+});
+
+test('a PR on a core-team or not-yet-open issue comments on the PR and claims nothing', async () => {
+  const { github, calls } = fake({
+    byNumber: { 7: openIssue(7, [], ['help wanted', 'in progress']), 8: openIssue(8, [], ['bug']) },
+  });
+  assert.deepEqual(await claim.handlePull({ github, context: pullCtx(50, 'Thing (#7) (#8)') }), []);
+  assert.equal(find(calls, 'addLabels'), undefined);
+  const bodies = calls.filter((c) => c[0] === 'comment').map((c) => c[1].body);
+  assert.match(bodies[0], /core team/);
+  assert.match(bodies[1], /isn't open for contributors/);
+});
+
+test('a maintainer\'s PR claims nothing', async () => {
+  const { github, calls } = fake({ byNumber: { 7: openIssue(7) }, perms: { alice: 'admin' } });
+  assert.deepEqual(await claim.handlePull({ github, context: pullCtx(50, 'Thing (#7)') }), []);
+  assert.equal(calls.length, 0);
+});
+
+test('a claim whose PR is stale but which was claimed recently stands', async () => {
+  const w = fake({ issues: [issue(7)], timeline: [labeled(ago(2 * D)), pr(9)], pushed: ago(30 * D) });
+  assert.deepEqual(await claim.sweep({ github: w.github, context: { repo }, now: NOW }), []);
+});