debridge-signing

Transaction Signing

PREREQUISITE: Read ../common/SKILL.md for environment detection, auth, and chain configuration.

Quick Reference

What Needs Signing

deBridge transactions from mcp__debridge__create_tx (cross-chain) or mcp__debridge__transaction_same_chain_swap (same-chain) return up to two transaction objects to sign:

1. Token approval tx (if allowance insufficient) — a standard EVM transaction calling approve() on the token contract.
2. Bridge/swap tx — an EVM transaction that may include EIP-712 typed data for DLN order creation.

Both are standard {to, data, value, chainId} objects. Sign and broadcast to the source chain RPC.

Signer Routing

Use the Signer value from WALLET_DISCOVERY to select the right reference:

Resolving env-privkey

When Signer = env-privkey, a private key exists but a signing library is still needed. Pick based on what is available:

1. Node.js + ethers or viem installed → sdk-signer.md
2. cast available → foundry-cast.md
3. None of the above → install one: npm install ethers is the fastest path.

Transaction Flow

After mcp__debridge__create_tx or mcp__debridge__transaction_same_chain_swap returns tx data:

Step 0: Preflight Checks

Before signing, the agent MUST verify:

1. Native balance for gas + fixFee — Parse fixFee (wei) and estimatedTransactionFee.total from the response. Check that the wallet’s native balance on the source chain covers both. If insufficient, stop and tell the user how much more they need.
2. ERC-20 allowance (EVM only, non-native tokens) — If the response does NOT include approveTx, the agent MUST still check the token’s allowance for the bridge contract (tx.to). Use scripts/erc20-approve.mjs to check and approve if needed. Do NOT assume the MCP always returns approveTx — it may not.
3. SOL rent/fees (Solana source) — Solana bridge txs require ~0.024 SOL for rent deposits + tx fees, on top of the bridge amount. Check SOL balance before signing.

Step 1: Check for Approval

If the response includes an approval transaction (approveTx):

1. Sign and send the approval tx first.
2. Wait for confirmation (1 block).
3. Proceed to Step 2.

If no approveTx but source token is ERC-20, run scripts/erc20-approve.mjs to check/approve (see Step 0).

Step 2: Sign and Send Bridge Transaction

1. Take the main tx object (tx field from create_tx response).
2. Sign with the detected signer.
3. Broadcast to the source chain RPC.
4. Record the transaction hash.

Step 3: Hand Off to Monitoring (cross-chain only)

For cross-chain bridges, pass the tx hash and order ID to ../swap/monitoring.md for order tracking. Same-chain swaps settle in a single transaction — no monitoring needed.

RPC Endpoints

Most signers need an RPC connection to the source chain:

• OWS: for EVM, ows sign tx handles signing locally — broadcast via RPC separately; for Solana, set SOLANA_RPC_URL or use the default public RPC
• ethers/viem: pass RPC URL to provider constructor
• cast: use --rpc-url flag
• browser wallet: uses the wallet’s connected RPC
• Privy MCP: handles RPC internally — no RPC URL needed from the agent

Use public RPCs or the user’s configured RPC. Prefer user-provided RPCs or environment variables ($ETH_RPC_URL, $RPC_URL) over hardcoded defaults. The balance query skills include public RPCs as fallback defaults — override them when the user has configured RPCs.

For programmatic RPC discovery from Chainlist, read ../common/rpc-discovery.md.

Common Errors

References

• ows-signing.md — OWS local self-custody signing (EVM, Solana, Tron)
• sdk-signer.md — ethers.js and viem signing
• foundry-cast.md — Foundry cast CLI signing
• metamask.md — Browser wallet signing
• privy-mcp.md — Privy embedded wallet signing via MCP