A Vault is not a Yield Router Vaults get judged by their APY, which tells you where the yield comes from and nothing about the vault's actual mechanism. Two vaults can quote the same number and behave nothing alike the moment the market moves. The mechanism is what a vault actually is: how your downside is capped, how much leverage you carry, whether you sit junior or senior to another holder, and how it behaves when conditions turn bad. That set of choices is the vault, APY is just the yield it routes. A vault is an SPV. In traditional finance a special purpose vehicle is the legal entity you stand up to ring-fence a specific set of risks and payoffs into one clean claim, and it takes lawyers, a trustee, and weeks. Onchain, a vault is that same vehicle as a contract: programmable, composable, and live in an afternoon. That is the superpower, and it has nothing to do with yield. The large majority of onchain vaults use a programmable SPV to express one boring structure, the linear long. You deposit, you earn yield on your stake, and your downside is just the underlying's downside. A lending vault, a liquid-staking vault, a yield aggregator, and a curated lending vault: different sources of yield, identical mechanism. The vaults that use the SPV for real structure are each a small, separate niche. Pendle splits a yield-bearing position into a fixed leg and a floating leg. The option vaults sell a covered call, trading the upside above a strike for premium, a capped payoff. Leveraged vaults amplify the linear long. Each expresses one structure, and none of them compose, so you cannot ask a single vault for "protected, capped upside, senior to a first-loss buffer" and have it built for you. Routing capital to good, risk-adjusted yield is real work, and the curator wave has made it much better. But that work tunes the yield, while the mechanism is the part that survives a bad week. So the more useful question about a vault is not what it yields but what it does when the market turns. Can it protect the principal, floor a loss, lever with a stop, put someone else in front of your risk?