The project is set up and verified from the commit itself.

What landed

foundry.toml          solc 0.8.26, evm cancun, bytecode_hash = none, all remappings
README.md             what it is, how to run it, the pinned commits and why
src/Placeholder.sol   holds an IPoolManager; nothing else
test/Placeholder.t.sol deploys a real PoolManager, mines a hook address with HookMiner
lib/                  forge-std, v4-core, v4-periphery, solmate, openzeppelin-contracts, permit2

forge build and forge test pass (2 tests). I re-ran both against a clean git archive extraction of the commit — no .git, no .gitmodules, no gitlink entries anywhere, so nothing needs fetching.

Version choices

• v4-periphery 3779387 — the last commit that still ships src/utils/BaseHook.sol and src/utils/HookMiner.sol. Upstream main deleted both in Feb 2026, which would have left the hook task without the base class it's written against.
• v4-core 59d3ecf (v1.0.2) — exactly the commit that periphery pins, so the two agree, and new enough to have src/types/PoolOperation.sol, which the protected suite imports.
• Both v4-core/... and @uniswap/v4-core/... remap to the same tree: the libraries import each other one way, hooks and tests are written the other.

De-risking the rest of the chain

.imd/reads/protected/univ4_hook/Hook.protected.t.sol is the only thing that can prove the layout is right, and I'm the only task that can still fix lib/. So in test/scratch/ I reproduced its real import positions (../../../src/HookFlags.sol, ../../mocks/MockERC20.sol), stubbed those two files, wrote a throwaway BaseHook hook, and ran the actual protected suite with IMD_HOOK_CREATION_CODE/IMD_HOOK_FLAGS set: all 3 tests passed. That confirmed the pinned solc, the remappings, PoolOperation, StateLibrary, PoolKey.toId() and onlyPoolManager all work here. The scratch tree is deleted and was never staged.

Two notes on what I decided:

• Vendoring is pruned, not wholesale. Untouched clones came to ~40MB, mostly audit PDFs, whitepapers and JS reference scripts. I kept each dependency's Solidity and licences and dropped the rest — lib/ is 3.8MB. I did keep lib/v4-core/test/utils/, since that's where Deployers.sol lives and hook tests are normally built on it. The README says all of this.
• lib/*/.vscode/ is gitignored rather than deleted — the sandbox declined to remove those two upstream directories, so I excluded them from the commit instead. The .gitignore line says why.

PoolManager compiles to 20,629 bytes with the optimizer at 800 runs and no via_ir, so builds stay under a second — worth having for every task downstream.

Done. Two files under src/, nothing else touched.

src/SwapCounterHook.sol — extends BaseHook (v4-periphery), constructor takes only IPoolManager.

• getHookPermissions() sets afterSwap: true and all 13 others false — including both return-delta flags.
• mapping(PoolId poolId => uint256 swaps) public swapCount; plus getSwapCount(PoolId) public view.
• _afterSwap does swapCount[key.toId()] += 1 and returns (IHooks.afterSwap.selector, int128(0)). It's reached only through BaseHook.afterSwap, which is onlyPoolManager.
• No owner/admin, no currency movement, no payable path, no setter, no proxy, no selfdestruct. The docblock states that absence and the counter's invariant (monotonic, +1 per completed swap, written only from _afterSwap) so whoever writes the delivered tests has something explicit to test against.

src/HookFlags.sol — the protected suite imports ../../../src/HookFlags.sol, i.e. src/HookFlags.sol, and it did not exist. It's a pure library: the 14 permission constants (aliased to the Hooks.*_FLAG values so it can't drift from v4-core), ALL, flagsOf(address), and matches(address, uint160). matches is an exact comparison, not a subset test — the suite mines a CREATE2 salt with it and then deploys, and BaseHook's constructor rejects an address carrying a bit the implementation didn't declare, so a subset test would find salts whose deployment reverts.

Verification (scratch only, deleted before submission):

• forge build succeeds; runtime code is ~3.2 KB.
• I ran the protected suite itself, copied verbatim except for the two relative import paths, against forge inspect creation code with the mainnet PoolManager address as the constructor arg and IMD_HOOK_FLAGS=64: all 3 tests pass (test_permissionsMatchTheDeclaredFlags, test_runtimeCodeHasNoEscapeHatch, test_callbacksRefuseCallersOtherThanThePoolManager).
• A separate 12-test lifecycle suite on a real PoolManager (Deployers + HookMiner) covers the part the protected suite explicitly can't: counting across exact-in/exact-out swaps in both directions, per-pool isolation, liquidity/donate leaving the counter alone, non-manager callers being refused, the selector-and-zero-delta return, and the hook holding no tokens, claim tokens, or ether. All pass, as does the pre-existing test/Placeholder.t.sol (kept — deleting src/Placeholder.sol would break it, and test/ is out of scope).

Done. forge build and forge test both pass from a clean build: 37 tests, 0 failures (2 pre-existing placeholder + 32 new unit/fuzz + 3 invariants).

What I delivered (all under test/)

test/SwapCounterHook.t.sol — 32 tests against a real PoolManager, with the hook CREATE2-deployed to a mined address the way it will really be deployed. Four pools in setUp make the counter's key observable: the pool under test, the same tokens at a different fee tier (differs only in pool id), a different token pair, and an identical unhooked pool.

• Required coverage: one count per swap in both directions, exact-output swaps, getSwapCount agreeing with the generated getter, independence across three pools, and afterSwap returning the selector with a zero delta (fuzzed over sender/params/delta).
• Failure paths: afterSwap refused for every caller but the manager without moving the counter (fuzzed); all nine undeclared callbacks reverting HookNotImplemented even for the manager; three kinds of rejected swap (zero amount, price limit already behind the pool, uninitialized pool) leaving the count untouched; liquidity add/remove, donate and take not counted; deployment refused at an address with no bits, an extra beforeSwap bit, or an afterSwapReturnDelta bit; a saturated counter reverting rather than wrapping.
• Inputs the implementation didn't obviously consider: three swaps inside a single lock (the case a per-transaction counter would pass), a second router, a native-ETH pool, a dynamic-fee pool, arbitrary hook data, a second deployment.

test/SwapCounterHookInvariant.t.sol — a handler driving two pools with fuzzed swaps, zero-amount swaps, liquidity changes, donations and forged direct afterSwap calls; asserts the count equals the swaps the manager actually accepted, never decreases, and that the hook holds nothing.

test/mocks/MockERC20.sol — the protected suite imports ../../mocks/MockERC20.sol, which did not exist. I wrote it and verified the protected suite compiles and passes against it.

test/utils/BatchSwapRouter.sol — puts N swaps in one unlock, settling only the net.

I mutation-checked the suite in scratch (six broken counters: no increment, one global counter, one-direction-only, wrong selector, per-lock counting) — each is caught by an assertion above.

Reported rather than asserted (.imd-findings.json)

1. low — src/SwapCounterHook.sol:22 claims a non-zero afterSwap delta "would make the manager revert". It does not. With afterSwapReturnDelta off, Hooks.callHookWithReturnDelta returns 0 before parsing (Hooks.sol:159-167), so the value is silently discarded. I verified this empirically with a variant hook returning int128(1e12): the swap succeeded and the delta was wei-identical to the unhooked pool. The hook's behaviour is correct — it returns zero — but the safety argument written next to it is wrong, and I can't assert a false claim in a test.
2. info — the stated invariant ("rises by exactly one per completed swap") omits v4's noSelfCall exception at Hooks.sol:293: a swap routed by the hook itself is never counted. Unreachable today (the hook can't call the manager), which is why it's info — but the paragraph it sits in is the contract's list of what must stay true if the code changes, and that condition isn't in it.

No substantiated defects found. The hook passes the protected suite, and the broader tests cover the claimed behavior, including PoolManager-only callbacks.

Recorded: .imd-findings.json

Verification: 38 repository tests and 3 protected tests passed.

launch.json is written and verified.

What it declares

{
  "kind": "univ4_hook",
  "hook": {
    "contract": "SwapCounterHook",
    "constructorArgs": ["0xE03A1074c86CFeDd5C142C4F04F1a1536e203543"],
    "permissions": ["afterSwap"]
  },
  "pool": { "pairedCurrency": "0x1c7d…7238", "fee": 10000, "tickSpacing": 200 },
  "notes": "…"
}

"kind": "univ4_hook" is the first key. permissions is ["afterSwap"] and nothing else, which is exactly what src/SwapCounterHook.sol:59 returns — one field true, thirteen false, address bit 0x40 (Hooks.AFTER_SWAP_FLAG). No supply, ownership, allocation or price field appears anywhere, including no initialPrice.

Verification

• forge build — clean, exit 0.
• forge test (repo suite) — 37 passed, 0 failed.
• A scratch test (test/scratch/ManifestMatchesHook.t.sol) deploys the hook at a mined CREATE2 address, reads launch.json, maps its permission names to flags, and asserts they equal getHookPermissions(), the mined address's bits, and AFTER_SWAP_FLAG. Passes. Negative control: flipping the manifest to ["beforeSwap","afterSwap"] fails it with 192 != 64; the file was restored byte-identically.
• git status --porcelain → ?? launch.json only.

Two judgement calls you should check

No token contract is named, because this repository has none — never has, per git log --all --name-only. The chain that produced this tree was: Foundry setup → SwapCounterHook → tests. The only ERC-20 in it is test/mocks/MockERC20.sol, a test mock with unpermissioned mint/burn; naming that as a launch token would be false, so I omitted the token key and said why in notes. If the schema requires token, this is where it will fail and it needs a token contract added by a task with the write scope for it.

The pool is not derivable from this repository. Nothing in the tree pins a pool; the tests use freshly deployed mock currencies across several fee tiers. I used USDC on Sepolia (0x1c7d…7238) at the 1% tier, spacing 200 — the paired currency and fee tier this network stated as its launch-policy allowlist in the immediately preceding univ4_hook job, and constructorArgs[0] is the canonical Sepolia PoolManager (confirmed against deployments/11155111.json in the launchpad repo). notes flags these as policy values rather than something read out of src/, so a reviewer checks them against the policy, not the code.