polycli_pos_exit-proof.md

polycli pos exit-proof

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Table of Contents

• Description
• Usage
• Flags
• See Also

Description

Generate a Polygon PoS exit proof for a burn transaction.

polycli pos exit-proof [flags]

Usage

polycli pos exit-proof

Generate the ABI-encoded exit payload required to withdraw tokens from Polygon PoS to Ethereum.

Usage

polycli pos exit-proof [flags]

Description

When a user burns tokens on the Polygon PoS sidechain, they must later submit a cryptographic proof to the Ethereum WithdrawManager contract to finalise the withdrawal. This command constructs that proof by:

1. Fetching the burn transaction receipt from L2 to determine the block number and transaction index.
2. Fetching all receipts for the burn block via eth_getBlockReceipts and reconstructing the receipts Merkle Patricia Trie (MPT).
3. Generating an MPT proof (sibling nodes from root to leaf) for the burn receipt.
4. Binary-searching the RootChain contract on L1 to find the checkpoint that covers the burn block.
5. Fetching the block headers for the checkpoint range and building a binary Merkle proof that the burn block hash is included.
6. ABI-encoding all of the above into the payload expected by startExitWithBurntTokens(bytes).

Flags

Flag	Required	Default	Description
--l1-rpc-url	yes	—	L1 (Ethereum) RPC URL
--l2-rpc-url	yes	—	L2 (Polygon PoS) RPC URL
--root-chain-address	yes	—	RootChain contract address on L1
--tx-hash	yes	—	burn transaction hash on L2
--checkpoint-stride	no	10000	number of L2 blocks per checkpoint; override for local testnets that use a smaller value
--log-index	no	0	index of the burn log within the receipt; 0 works for most ERC20 withdrawals — increase if the token emits extra logs before the burn event

Output

Writes 0x-prefixed ABI-encoded payload bytes to stdout. All progress and diagnostic messages go to stderr so the output can be captured directly in a shell variable.

Example

# Step 1: burn tokens on L2 (e.g., call ERC20 withdraw on the ChildToken contract)
# burn_tx_hash=0x...

# Step 2: wait for the checkpoint to be submitted (~30 min on mainnet)

# Step 3: generate the exit proof
payload=$(polycli pos exit-proof \
  --l1-rpc-url "${L1_RPC_URL}" \
  --l2-rpc-url "${L2_RPC_URL}" \
  --root-chain-address "${ROOT_CHAIN_ADDRESS}" \
  --tx-hash "${burn_tx_hash}")

# Step 4: start the exit on L1
cast send \
  --rpc-url "${L1_RPC_URL}" \
  --private-key "${PRIVATE_KEY}" \
  "${WITHDRAW_MANAGER_PROXY_ADDRESS}" \
  "startExitWithBurntTokens(bytes)" \
  "${payload}"

# Step 5: process the exit on L1
cast send \
  --rpc-url "${L1_RPC_URL}" \
  --private-key "${PRIVATE_KEY}" \
  "${WITHDRAW_MANAGER_PROXY_ADDRESS}" \
  "processExits(address)" \
  "${POL_TOKEN_ADDRESS}"

Flags

      --checkpoint-stride uint      number of L2 blocks per checkpoint (10000 on mainnet; override for local testnets) (default 10000)
  -h, --help                        help for exit-proof
      --l1-rpc-url string           Ethereum RPC URL
      --l2-rpc-url string           Polygon PoS RPC URL
      --log-index uint              index of the burn log within the receipt (0 works for most ERC20 withdrawals; increase if the token emits extra logs before the burn event)
      --root-chain-address string   RootChain contract address on L1
      --tx-hash string              burn transaction hash on L2

The command also inherits flags from parent commands.

      --config string      config file (default is $HOME/.polygon-cli.yaml)
      --pretty-logs        output logs in pretty format instead of JSON (default true)
  -v, --verbosity string   log level (string or int):
                             0   - silent
                             100 - panic
                             200 - fatal
                             300 - error
                             400 - warn
                             500 - info (default)
                             600 - debug
                             700 - trace (default "info")

See also

• polycli pos - Utilities for Polygon PoS.