feat(agglayer): store and use metadata hash for bridge-out leaves

[mmagician]

Summary

• Store pre-computed keccak256(abi.encode(name, symbol, decimals)) metadata hash in faucet storage (2 value slots)
• Read it via FPI during bridge-out leaf construction instead of pushing zeros
• Add MetadataHash::from_token_info and encode_token_metadata Rust helpers with Solidity ABI encoding compatibility
• Regenerate Solidity MMR test vectors with real metadata hash values

Context

When a user calls claimAsset() on PolygonZkEVMBridgeV2, they pass the raw metadata bytes as a parameter. The flow is:

1. Leaf verification: The bridge reconstructs the merkle leaf using keccak256(metadata) as the metadataHash field, and verifies the merkle proof against the exit root. If the hash doesn't match what's in the leaf, the proof fails.
2. Token lookup: The bridge computes tokenInfoHash = keccak256(abi.encodePacked(originNetwork, originTokenAddress)) and checks tokenInfoToWrappedToken[tokenInfoHash] to see if a wrapped token already exists.
3. If no wrapped token exists:
   • Calls _deployWrappedToken(tokenInfoHash, metadata) which:
     • Deploys a transparent proxy via CREATE2 using tokenInfoHash as the salt (making the address deterministic across chains)
     • Decodes the metadata: (string name, string symbol, uint8 decimals) = abi.decode(metadata, (string, string, uint8))
     • Calls initialize(name, symbol, decimals) on the proxy to set up the ERC20
   • Mints tokens to the destination address
   • Stores bidirectional mappings: tokenInfoHash -> wrappedAddress and wrappedAddress -> {originNetwork, originTokenAddress}
4. If wrapped token already exists: Just mints more tokens to the destination address. The metadata is still verified via the merkle proof but not used for deployment.

The key point: the metadata bytes serve to initialize the wrapped token. The claimer/relayer must provide the correct raw metadata as part of the claim process (they can get the individual elements from the Miden faucet storage), and it its hash must match what is added to the leaf in LET upon bridging out Miden -> EVM.

The metadata hash is computed off-chain at faucet creation time and stored in two storage slots. For future onchain verification during token registration see #2586.

Test plan

• MetadataHash::from_token_info("Test Token", "TEST", 18) matches Solidity test vector hash 0x4d0d9fb7...
• All 39 agglayer integration tests pass (bridge_in, bridge_out, config, MMR, etc.)
• Bridge-out leaf values match regenerated Solidity MMR frontier vectors
• make lint passes (clippy, format, typos, toml, machete)

Closes #2453

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds end-to-end support for Solidity-compatible token metadata hashing in the AggLayer flow by storing a precomputed metadata hash on the faucet and retrieving it via FPI during bridge-out leaf construction, with corresponding updates to test vectors and dependencies.

Changes:

• Add MetadataHash (keccak256 over Solidity abi.encode(name, symbol, decimals)) and store it in two faucet storage slots.
• Update bridge-out MASM to fetch the faucet’s metadata hash via FPI and include it in leaf data / MMR computation.
• Refresh Solidity tests + JSON vectors and update Rust tests/call sites for the new faucet constructor parameter.

Reviewed changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
deny.toml	Allow CC0-1.0 license for newly introduced dependencies.
crates/miden-testing/tests/agglayer/faucet_helpers.rs	Update faucet creation in tests to provide MetadataHash.
crates/miden-testing/tests/agglayer/bridge_out.rs	Update bridge-out tests to pass MetadataHash into faucet creation.
crates/miden-testing/tests/agglayer/bridge_in.rs	Update faucet creation in tests to pass metadata hash from leaf data.
crates/miden-agglayer/src/lib.rs	Thread metadata_hash through faucet account creation helpers.
crates/miden-agglayer/src/faucet.rs	Add metadata-hash storage slots and persist hash into faucet component storage.
crates/miden-agglayer/src/eth_types/metadata_hash.rs	Implement Solidity ABI encoding + keccak hashing, plus compatibility tests.
crates/miden-agglayer/solidity-compat/test/MMRTestVectors.t.sol	Generate vectors using a real metadata hash instead of zero.
crates/miden-agglayer/solidity-compat/test-vectors/mmr_frontier_vectors.json	Update expected leaves/roots to match new metadata hash behavior.
crates/miden-agglayer/Cargo.toml	Add alloy-sol-types, miden-crypto, and dev deps for new tests.
crates/miden-agglayer/asm/components/faucet.masm	Re-export get_metadata_hash from the faucet component.
crates/miden-agglayer/asm/agglayer/faucet/mod.masm	Add storage constants and implement get_metadata_hash procedure.
crates/miden-agglayer/asm/agglayer/bridge/bridge_out.masm	Fetch metadata hash via FPI and write it into leaf data before hashing/MMR update.
crates/miden-agglayer/asm/agglayer/bridge/bridge_config.masm	Add TODO note about verification on faucet registration.
CHANGELOG.md	Document the new metadata-hash behavior in AggLayer faucet/bridge-out.
Cargo.toml	Add workspace dependency definition for alloy-sol-types.
Cargo.lock	Lock new transitive dependencies pulled in by alloy-sol-types and related crates.

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