diff --git a/.gas-snapshot b/.gas-snapshot
index 323dd5c..e7bfe77 100644
--- a/.gas-snapshot
+++ b/.gas-snapshot
@@ -34,11 +34,11 @@ TimeLockTest:test_OnlyAdmin_CanQueue() (gas: 16143)
 TimeLockTest:test_QueueThenExecute() (gas: 55711)
 TimeLockTest:test_Queue_RevertOnDuplicate() (gas: 46068)
 TokenTest:testFuzz_Approve(address,uint256) (runs: 1000, μ: 36452, ~: 36831)
-TokenTest:testFuzz_Transfer_PreservesTotalSupply(uint256) (runs: 1000, μ: 47212, ~: 47844)
-TokenTest:test_Approve_AndTransferFrom() (gas: 72961)
-TokenTest:test_InfiniteAllowance_NotDecremented() (gas: 69946)
+TokenTest:testFuzz_Transfer_PreservesTotalSupply(uint256) (runs: 1000, μ: 47249, ~: 47882)
+TokenTest:test_Approve_AndTransferFrom() (gas: 73017)
+TokenTest:test_InfiniteAllowance_NotDecremented() (gas: 70002)
 TokenTest:test_Metadata() (gas: 21459)
-TokenTest:test_Transfer() (gas: 44638)
+TokenTest:test_Transfer() (gas: 44676)
 TokenTest:test_TransferFrom_RevertOnInsufficientAllowance() (gas: 39482)
 TokenTest:test_Transfer_RevertOnInsufficientBalance() (gas: 15571)
 TokenTest:test_Transfer_RevertOnZeroAddress() (gas: 11220)
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index fd31995..4156064 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,6 +18,9 @@ jobs:
       - name: Install Foundry
         uses: foundry-rs/foundry-toolchain@v1
 
+      - name: Check formatting
+        run: forge fmt --check
+
       - name: Install dependencies
         run: forge install
 
@@ -30,5 +33,5 @@ jobs:
       - name: Run invariant tests
         run: forge test -vvv --match-contract Invariant
 
-      - name: Gas snapshot
+      - name: Gas snapshot (informational)
         run: forge snapshot
diff --git a/.gitignore b/.gitignore
index d517577..24646bb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,7 +2,6 @@
 out/
 cache/
 broadcast/
-lib/
 .env
 .env.*
 !.env.example
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..888d42d
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "lib/forge-std"]
+	path = lib/forge-std
+	url = https://github.com/foundry-rs/forge-std
diff --git a/README.md b/README.md
index 8230eab..cf51801 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # foundry-testing
 
-Foundry workspace built around three small contracts. The interesting part is the test suite: unit tests, fuzz tests, and a stateful invariant suite with a handler. Full suite runs in ~130ms across 13 tests, including 256 invariant runs and 3,840 random calls.
+Foundry workspace built around seven small contracts. The interesting part is the test suite: unit tests, fuzz tests, and stateful invariant suites with handlers. The full suite runs in under 200ms across 51 tests, including invariant runs that exercise thousands of random call sequences.
 
 ## Stack
 
@@ -29,15 +29,26 @@ forge snapshot
 forge test --gas-report
 ```
 
+Formatting and the gas baseline are enforced in CI:
+
+```bash
+forge fmt --check
+forge snapshot --check
+```
+
 ## What's in here
 
-| Contract | Test types |
-|---|---|
-| `src/Counter.sol` | unit, fuzz |
-| `src/Vault.sol` | unit, fuzz, invariant (with `VaultHandler.sol`) |
-| `src/Staking.sol` | unit, fuzz |
+| Contract | Description | Test types |
+|---|---|---|
+| `src/Counter.sol` | Trivial counter | unit, fuzz |
+| `src/Token.sol` | Minimal ERC20-style token | unit, fuzz |
+| `src/NFT.sol` | Minimal ERC721-style NFT | unit, fuzz |
+| `src/Vault.sol` | ETH vault | unit, fuzz, invariant |
+| `src/Staking.sol` | ETH staking | unit, fuzz, invariant |
+| `src/TimeLock.sol` | Queue/execute/cancel timelock | unit, fuzz |
+| `src/Ownable.sol` | Two-step ownership mixin | unit |
 
-Tests live in `test/`. The invariant handler in `test/VaultHandler.sol` constrains the random call surface so invariants converge instead of bouncing off reverts.
+Tests live in `test/`. The invariant handler in `test/VaultInvariant.t.sol` constrains the random call surface (bounded amounts, a fixed actor set) so invariants converge instead of bouncing off reverts, and it tracks ghost variables to cross-check the contract's own accounting.
 
 ## Why Foundry over Hardhat
 
diff --git a/foundry.lock b/foundry.lock
new file mode 100644
index 0000000..7521bfd
--- /dev/null
+++ b/foundry.lock
@@ -0,0 +1,8 @@
+{
+  "lib/forge-std": {
+    "tag": {
+      "name": "v1.16.1",
+      "rev": "620536fa5277db4e3fd46772d5cbc1ea0696fb43"
+    }
+  }
+}
\ No newline at end of file
diff --git a/foundry.toml b/foundry.toml
index d497abf..a0889af 100644
--- a/foundry.toml
+++ b/foundry.toml
@@ -3,6 +3,7 @@ src = "src"
 out = "out"
 libs = ["lib"]
 solc = "0.8.24"
+evm_version = "cancun"
 optimizer = true
 optimizer_runs = 200
 
diff --git a/lib/forge-std b/lib/forge-std
new file mode 160000
index 0000000..620536f
--- /dev/null
+++ b/lib/forge-std
@@ -0,0 +1 @@
+Subproject commit 620536fa5277db4e3fd46772d5cbc1ea0696fb43
diff --git a/src/NFT.sol b/src/NFT.sol
index 76e6eab..22072e2 100644
--- a/src/NFT.sol
+++ b/src/NFT.sol
@@ -35,7 +35,9 @@ contract NFT {
         require(to != address(0), "NFT: mint to zero");
         require(_owners[tokenId] == address(0), "NFT: already minted");
         _owners[tokenId] = to;
-        unchecked { _balances[to] += 1; }
+        unchecked {
+            _balances[to] += 1;
+        }
         emit Transfer(address(0), to, tokenId);
     }
 
@@ -56,9 +58,7 @@ contract NFT {
         address owner = ownerOf(tokenId);
         require(owner == from, "NFT: from is not owner");
         require(
-            msg.sender == owner ||
-                isApprovedForAll[owner][msg.sender] ||
-                getApproved[tokenId] == msg.sender,
+            msg.sender == owner || isApprovedForAll[owner][msg.sender] || getApproved[tokenId] == msg.sender,
             "NFT: not authorized"
         );
 
diff --git a/src/TimeLock.sol b/src/TimeLock.sol
index 9936d8e..f895cdc 100644
--- a/src/TimeLock.sol
+++ b/src/TimeLock.sol
@@ -33,7 +33,11 @@ contract TimeLock {
         return keccak256(abi.encode(target, value, data, salt));
     }
 
-    function queue(address target, uint256 value, bytes calldata data, bytes32 salt) external onlyAdmin returns (bytes32 id) {
+    function queue(address target, uint256 value, bytes calldata data, bytes32 salt)
+        external
+        onlyAdmin
+        returns (bytes32 id)
+    {
         id = hashOp(target, value, data, salt);
         if (queuedAt[id] != 0) revert AlreadyQueued();
         uint256 eta = block.timestamp + delay;
@@ -47,7 +51,12 @@ contract TimeLock {
         emit Cancelled(id);
     }
 
-    function execute(address target, uint256 value, bytes calldata data, bytes32 salt) external payable onlyAdmin returns (bytes memory) {
+    function execute(address target, uint256 value, bytes calldata data, bytes32 salt)
+        external
+        payable
+        onlyAdmin
+        returns (bytes memory)
+    {
         bytes32 id = hashOp(target, value, data, salt);
         uint256 eta = queuedAt[id];
         if (eta == 0) revert NotQueued();
diff --git a/test/Token.t.sol b/test/Token.t.sol
index d2263f0..e0f536d 100644
--- a/test/Token.t.sol
+++ b/test/Token.t.sol
@@ -14,7 +14,7 @@ contract TokenTest is Test {
     function setUp() public {
         token = new Token("Test", "TST", INITIAL);
         // Move the entire supply to alice so tests start from a known state
-        token.transfer(alice, INITIAL);
+        assertTrue(token.transfer(alice, INITIAL));
     }
 
     function test_Metadata() public view {
@@ -26,7 +26,7 @@ contract TokenTest is Test {
 
     function test_Transfer() public {
         vm.prank(alice);
-        token.transfer(bob, 100 ether);
+        assertTrue(token.transfer(bob, 100 ether));
 
         assertEq(token.balanceOf(alice), INITIAL - 100 ether);
         assertEq(token.balanceOf(bob), 100 ether);
@@ -50,7 +50,7 @@ contract TokenTest is Test {
         assertEq(token.allowance(alice, bob), 50 ether);
 
         vm.prank(bob);
-        token.transferFrom(alice, bob, 30 ether);
+        assertTrue(token.transferFrom(alice, bob, 30 ether));
 
         assertEq(token.balanceOf(bob), 30 ether);
         assertEq(token.allowance(alice, bob), 20 ether);
@@ -70,7 +70,7 @@ contract TokenTest is Test {
         token.approve(bob, type(uint256).max);
 
         vm.prank(bob);
-        token.transferFrom(alice, bob, 100 ether);
+        assertTrue(token.transferFrom(alice, bob, 100 ether));
 
         // Infinite allowance should be preserved across transfers
         assertEq(token.allowance(alice, bob), type(uint256).max);
@@ -79,7 +79,7 @@ contract TokenTest is Test {
     function testFuzz_Transfer_PreservesTotalSupply(uint256 amount) public {
         amount = bound(amount, 0, INITIAL);
         vm.prank(alice);
-        token.transfer(bob, amount);
+        assertTrue(token.transfer(bob, amount));
 
         assertEq(token.balanceOf(alice) + token.balanceOf(bob), INITIAL);
         assertEq(token.totalSupply(), INITIAL);
diff --git a/test/VaultInvariant.t.sol b/test/VaultInvariant.t.sol
index 9dd36dd..cc07c85 100644
--- a/test/VaultInvariant.t.sol
+++ b/test/VaultInvariant.t.sol
@@ -67,10 +67,7 @@ contract VaultInvariantTest is Test {
 
     /// Ghost accounting: net flow (deposits - withdrawals) must equal contract balance
     function invariant_netFlowEqualsBalance() public view {
-        assertEq(
-            address(vault).balance,
-            handler.ghostTotalDeposits() - handler.ghostTotalWithdrawals()
-        );
+        assertEq(address(vault).balance, handler.ghostTotalDeposits() - handler.ghostTotalWithdrawals());
     }
 
     /// totalAssets() is a thin view but should never lie