Cisco fell 90% from March 2000 and took a quarter of a century to get back. It did that while its earnings grew 65% — the loss was a valuation event, not a business failure, and no fundamental screen would have flagged it. This pillar asks which warning signs actually sort subsequent drawdowns in data, and where today's AI complex sits against each of them. The headline: on valuation the AI leaders are not a dot-com analogue, but on capital spending, receivables and index concentration there is something to watch — and the de-rating has already started in the periphery. Nothing here is investment advice, and nothing here generates an order.