Implemented, reviewed, and documented ExpiringMerkleDistributor.sol.

• Self-contained; implements the specified claims, bitmap, expiry, sweeps, and safe transfers.
• forge build passed, including an offline build.
• forge test passed: 24 tests, including 256 fuzz cases.
• File scope verified. No deployment performed.

Wrote .imd-findings.json with one low-severity finding: the required test suite is absent.

Foundry compilation succeeds but executes no tests. No reproducible contract defect found. Contract files remain unchanged.

The findings file is excluded from git by the repository's own .git/info/exclude, so the harness collects it from disk rather than from a commit. That is expected. The work is complete.

Delivered: test/ExpiringMerkleDistributor.t.sol, a self-contained Foundry suite. The repository ships no forge-std and I may not add to lib/, so the file inlines a minimal Vm cheatcode interface and its own assertion helpers.

Results

What the suite covers

• Reference vector from the real StandardMerkleTree. I generated a six-leaf tree with @openzeppelin/merkle-tree in scratch and hardcoded root and proofs. That verifies the double-hash leaf encoding and sorted-pair hashing independently of any Solidity tree builder in the test file.
• Constructor. Zero token, zero sweepTo, expiry equal to now, in the past, zero, one second ahead, zero root, plus a fuzzed boundary.
• Claim failures. Double claim from same and different callers, wrong index, account or amount, proof for another leaf, empty, truncated, extended, reordered and bit-flipped proofs, a single-hashed leaf tree, an inner node presented as a leaf, claim one second past expiry, and expiry checked before proof.
• Bitmap. Indices 255 and 256 land in different words, max uint index, and a fuzz asserting only the claimed bit flips.
• Token behaviour. No-bool return tolerated for claim and sweep, false return rejected, revert surfaced as TokenTransferFailed with the bit rolled back, codeless token rejected, malformed return data of 1 and 31 bytes rejected, and a reentrant token that cannot double-claim but may claim a different leaf.
• Sweep. Reverts before and at expiry, works one second after from any caller, sends only the unclaimed remainder, repeats for late deposits, leaves the bitmap alone, and a fuzz proving exactly one of claim or sweep is open at any timestamp.

Defects: none found. The implementation matches the specification on every input I tried. I recorded two informational observations in .imd-findings.json rather than leaving them undocumented: a zero-balance sweep emits Swept(0) and performs a zero-value transfer, and the constructor accepts a token address with no code. Both are within spec and both are asserted by tests as the current behaviour.

I've written the README and three docs pages for ExpiringMerkleDistributor, based on the contract and tests that are actually in the repo. I committed README.md and docs/. artifacts/README.md is a copy of the README and is left untracked as asked (the local git exclude file ignores it).

Checks I ran. Foundry wasn't installed, so I installed forge 1.8.3. A fresh clone of the commit builds and passes all 63 tests. It needs network access the first time, to download solc; forge picked 0.8.37 because there's no foundry.toml pinning a version. I also ran the OpenZeppelin tree script from docs/merkle-tree.md with Node, and it reproduces the root and the leaf-0 proof hard-coded in the test file. Two README claims about edge cases (a leaf paying address(0), and tokens that reject zero-value transfers) I confirmed with throwaway tests in test/scratch, which aren't submitted.

What's in the docs:

• README.md: what the contract is, then a warning block near the top: never deployed, no deploy script, not audited, no admin or recovery, and some token types are unsafe. After that: build and test commands, the claim flow, cast examples, and a table of every entry point with who may call it and each revert.
• docs/reference.md: every function, event, error and storage variable, with the exact order of checks and the revert conditions.
• docs/merkle-tree.md: the leaf format and the tree-generation script.
• docs/security.md: the trust model, what the tests actually cover, 10 known hazards, and what to do before using it with real funds.

Where the code goes beyond or differs from the brief (listed in the README):

• It uses custom errors; the brief only said "reverts".
• The transfer helper rejects a token address with no code, but the constructor doesn't check this. So a wrong token address deploys fine and then every claim fails.
• sweep() on an empty contract emits Swept(0) rather than reverting.
• Zero-amount leaves can be claimed, and a leaf for address(0) is accepted.
• Events are emitted before the transfer; if the transfer fails the whole call, including the event, is rolled back.

Hazards for real funds (all flagged in the docs):

• Nothing checks that the contract holds enough to cover the tree.
• Fee-on-transfer and rebasing tokens can leave the last claimants unpaid.
• If the token blocklists sweepTo, leftover tokens are stuck forever.
• With tokens that reject zero-value transfers, zero-amount leaves can never be claimed.

Repo issues I documented but couldn't fix (they're outside the paths I'm allowed to change):

• There's no .gitignore, so out/ and cache/ show up as untracked after a build in a fresh clone.
• The compiler version floats because nothing pins it.
• One test comment says 64-byte return data is covered, but only the 32-byte case is tested.