Done. src/Hook.sol is the only file changed.

What the hook does now

• getHookPermissions() sets beforeSwap: true; everything else stays false (no return-delta flags).
• mapping(PoolId => uint256) private _swapCount, keyed by pool id — the hook is a singleton across pools, so the tally has to be per-pool.
• _beforeSwap increments the counter for key.toId() and returns (IHooks.beforeSwap.selector, BeforeSwapDeltaLibrary.ZERO_DELTA, 0) — no delta, no fee override. Direction is not read, so one swap counts once either way.
• swapCount(PoolId) public view returns (uint256) exposes it.

I also fixed two doc lines in the header that referenced a HOOK_FLAGS constant the test harness no longer has (it derives the address from getHookPermissions itself).

Verification — forge build clean, forge test 8/8 passing on the existing suite. In test/scratch/ I added 10 throwaway tests, all passing:

• counter starts at zero, counts buys, sells (oneForZero), and exact-output swaps, one per swap
• two pools sharing the hook keep separate tallies
• adds, removes and donates do not bump it
• against a hookless control pool with identical liquidity and fee tier, a buy produces byte-identical deltas — the hook takes nothing, and the hook holds zero ETH and zero token afterwards
• the zero-liquidity case matches a hookless pool exactly (both return a zero delta; note it does not revert in v4 with the default price limit, so the swap counts — a swap call happened)

One consequence worth flagging, from the harness rather than the hook: BaseHookTest.poolFee() returns DYNAMIC_FEE_FLAG only while the hook declares no permissions, so enabling beforeSwap flips the test pool to the 0.30% static tier. That is the template's intended behavior, and the existing tests still pass under it.

Done. forge build and forge test both pass from clean: 32 tests, 0 failures, with only test/Hook.t.sol modified.

What the tests cover

I kept the six inherited tests intact and added 26, in four groups:

Permissions — exactly one flag is set and it is beforeSwap; beforeSwapReturnDelta and afterSwap are explicitly off; every other callback still reverts HookNotImplemented even when the manager itself asks; and beforeSwap is called directly (impersonating the manager) to read its three return values — selector, ZERO_DELTA, fee override 0.

Counting — buys, sells, exact-output swaps, arbitrary hookData, swaps from a third-party sender, and a fuzz over 1–15 swaps.

Per-pool keying — a second pool on the same hook counts separately; an unknown pool id reads zero; a pool with no hook installed is never counted.

Failure paths (the count must not move):

• a forged direct beforeSwap call reverts NotPoolManager and leaves the count at zero
• a swap that reverts after the hook has already incremented (PriceLimitAlreadyExceeded) rolls the increment back
• a zero-amount swap is rejected upstream of the hook
• initialization, liquidity add/remove, and donations do not count

"Changes nothing else" — each operation runs against twin pools identical but for the hook, asserting results match to the wei: swaps (both directions, exact-in and exact-out), liquidity withdrawal with earned fees, donations, and empty-pool no-ops. Plus: the hook holds no ETH, no token, and no ERC-6909 claims after trading.

I mutation-tested the suite in test/scratch/ against five broken hooks (no counting, one global counter, double counting, one-direction-only, and one that skims 1%). Every mutant failed — the global-counter mutant is caught by exactly the two per-pool tests, and the skimming mutant by the permissions test plus all three twin-pool comparisons. A sixth mutant (unguarded callback) turned out not to be expressible: BaseHook.beforeSwap is non-virtual, so the guard cannot be dropped while the hook extends BaseHook.

One finding reported

.imd-findings.json records one low: swapCount counts beforeSwap invocations, not trades. Two measured repros — 50 consecutive 1-wei swaps on the launch pool give swapCount == 50 for 50 wei and zero token received; and a swap against a liquidity-free pool returns BalanceDelta(0, 0), refunds the full 1 ETH, and still counts.

The code matches the brief's literal wording ("increment once per swap"); what the brief doesn't settle is whether a call that trades nothing is a swap. Because a fix would have to choose a rule, I deliberately made no count assertion in test_SwapsAgainstAnEmptyPoolAreNoOpsAsTheyAreWithoutTheHook — it pins only the pool-level behaviour (zero deltas, full refund, identical to the hookless twin) and leaves the counting semantics to the report rather than blessing them.

Review complete. Wrote one substantiated low-severity finding to .imd-findings.json.

Validation passed: forge fmt --check, forge build, and all 32 tests. No source or test files were changed.

Done. launch.json is the only file added.

What I verified first — the hook was already implemented by an earlier contributor (src/Hook.sol), so this job was the manifest. I pinned every claim the manifest makes with a scratch test (test/scratch/ManifestFacts.t.sol, excluded from the repo via .git/info/exclude) rather than reading them off the source:

• getHookPermissions() returns beforeSwap: true and all 13 other fields false — flagsOf(p) == BEFORE_SWAP_FLAG exactly
• the pool key is native ETH / LaunchToken, fee 3000, tickSpacing 60, hooks = the hook (fee is the static tier, not dynamic, because BaseHookTest.poolFee() switches once the hook declares any flag)
• the getter is swapCount(PoolId), ABI signature swapCount(bytes32)

forge build compiles clean; forge test is 35/35 passing (32 inherited + 3 scratch). jq -e . parses the manifest.

The manifest names the two contracts, mirrors all 14 permission fields verbatim, and describes the pool as its v4 PoolKey. It carries no supply, ownership, allocation or price field — the starting tick and the full-supply seeding live in the test harness and belong to the launch policy, so they are deliberately absent.

One assumption worth flagging: the launch manifest schema is not in this working tree, and the sandbox confines me to the repo, so I could not validate against it mechanically. I inferred the shape from the task's three named requirements — hook contract, token contract, declared permissions, and the pool — as top-level hook / token / pool objects plus a name and description. The content is verified against the code; the key names are my best reading of the schema. If the gate rejects it on structure, the field values should all carry over unchanged to whatever the real key names are.