Context

contracts/MeridianVaultERC4626.sol is an ERC-4626 vault wrapper used by on-chain strategies. ERC-4626 share-price monotonicity + rounding direction are the top sources of vault exploits (e.g. Cream, Euler inflation attack). We have no Foundry invariants.

Scope

Files to touch:

• test/invariants/VaultInvariants.t.sol (new).
• Handler + invariants:
  • sharePrice is non-decreasing under deposits/withdraws (no donate-inflation).
  • previewDeposit(x) <= deposit(x) (rounding in favor of vault).
  • totalAssets() >= sum(convertToAssets(balanceOf(user))) for tracked users.
• Include an inflation-attack scenario as a separate unit test asserting it's mitigated.

Acceptance criteria

• Invariants pass on current implementation.
• Temporarily breaking rounding direction causes the invariant to fail (documented in PR).
• Runs in CI.

Estimated effort

L — ERC-4626 invariants are a known hard problem; ~2 days.

— kcolbchain / Abhishek Krishna