Four vacancies.
One worth a closer look.

// Niche jobs exercise v1. MIT licensed; see LICENSE.txt.
// Pure JavaScript: the website, Node.js and a Studio source use this same module.
const languages = ['Haskell', 'Elixir', 'F#'];

export function inspect(input) {
  const { jobs, language = 'Haskell', textField = 'description' } = input ?? {};
  if (!languages.includes(language)) throw new Error('Choose Haskell, Elixir or F#.');
  if (!['description', 'details'].includes(textField)) throw new Error('Choose description or details.');
  if (!Array.isArray(jobs) || jobs.length < 1 || jobs.length > 25) {
    throw new Error('Supply between 1 and 25 jobs.');
  }
  const ids = new Set();
  return jobs.map((job, index) => {
    for (const field of ['id', 'title', 'company', 'location', textField]) {
      if (typeof job?.[field] !== 'string' || !job[field].trim() || job[field].length > 2000) {
        throw new Error(`Job ${index + 1}: missing or invalid "${field}". Check the feed and textField.`);
      }
    }
    if (ids.has(job.id)) throw new Error(`Job ${index + 1}: duplicate id.`);
    ids.add(job.id);
    const sentences = job[textField].split(/(?<=[.!?])\s+/);
    // An intentionally small, inspectable rule for these English fixtures.
    // Optional mentions alone do not establish that a role uses the language.
    const escaped = language === 'F#' ? 'F#' : language;
    const mention = new RegExp(`\\b${escaped}(?=\\s|[.,;:!?)]|$)`, 'i');
    const sentence = sentences.find((line) =>
      mention.test(line) &&
      /\b(build|develop|maintain|required)\b/i.test(line) &&
      !/\b(optional|nice to have|not required)\b/i.test(line));
    return {
      id: job.id,
      title: job.title.trim(),
      company: job.company.trim(),
      location: job.location.trim(),
      language,
      selected: Boolean(sentence),
      reason: sentence?.trim() ?? 'No explicit core-work requirement for this language.'
    };
  });
}

export async function collect({ input }) {
  const decisions = inspect(input);
  const items = decisions.filter((job) => job.selected).map(({ selected, ...record }) => record);
  return { items, evidence: { resultCount: items.length, inspectedCount: decisions.length } };
}