HIP-1342 Impact Analysis

Impact analysis for HIP-1342 — Ignore Trailing Calldata for System Contract.

HIP-1342 proposes allowing Hedera system contracts (HTS, HAS, HSS) to accept and silently ignore trailing bytes in calldata beyond what the ABI-defined parameters require. This is a consensus rule change: transactions that currently revert due to strict calldata decoding will succeed after the HIP is activated.

This repository contains the final report, data, queries, and scripts used to quantify mainnet exposure and support the backwards-compatibility section of the HIP.

Quickstart

npm install
npm start

Workflow

The analysis runs in three stages:

1. Query the mirror node database

Run the SQL in network-data/sql-queries.sql against the Hedera mirror node PostgreSQL instance. Two result sets are produced:

• ethereum-direct-calls.csv — Ethereum transactions that called a system contract address directly and carried a CONTRACT_REVERT_EXECUTED result. Columns: ethereum_tx_consensus_timestamp, to_address_hex, payer_account, error_message.
• ethereum-nested-calls.csv — Nested contract actions (call depth > 0) that targeted a system contract and returned a revert result code. Columns: consensus_timestamp, sender, receiver, result_data.

System contract addresses queried:

Contract	Address
HTS	0x0000000000000000000000000000000000000167
HAS	0x000000000000000000000000000000000000016a
HSS	0x000000000000000000000000000000000000016b

2. Confirm CONTRACT_EXECUTION_EXCEPTION

bash scripts/check-contract-execution-exceptions.sh

Reads both CSV files, de-duplicates timestamps, resolves each one via the mirror node REST API (with an RPC fallback), and writes only the rows confirmed as CONTRACT_EXECUTION_EXCEPTION to network-data/contract-execution-exceptions.csv.

3. Detect trailing calldata

npm install
node scripts/check-trailing-calldata.js network-data/contract-execution-exceptions.csv \
  [--mirror-node <mirror-base-url>] \
  [--output results.csv]

For each confirmed exception, fetches the full function_parameters from the mirror node, decodes them against the known system-contract ABIs, re-encodes the decoded arguments to canonical form, and reports the difference as trailing_bytes.

Output columns: consensus_timestamp, transaction_id, eth_hash, to_contract, contract_name, selector, function_name, calldata_bytes, canonical_bytes, trailing_bytes, status.

Testnet Verification

scripts/test-hip-1342.js sends eight transactions to Hedera testnet to document the current (pre-HIP) behavior:

• Steps 1–4: createFungibleToken, EOA-direct and via an intermediate contract, with and without 32 trailing bytes.
• Steps 5–8: transferToken, same EOA-direct / via-contract / with-trailing-bytes matrix.

After all steps complete, the script always writes network-data/test-hip-1342-results.csv. Pass --csv <file> to override the output path.

Before running, create a .env file:

OPERATOR_KEY=<hex-encoded-ECDSA-private-key>
NETWORK_RPC_URL=https://testnet.hashio.io/api        # optional, this is the default
MIRROR_BASE=https://testnet.mirrornode.hedera.com    # optional, this is the default

Run the test and then feed the results through check-trailing-calldata.js to verify calldata lengths:

npm install
npm test

Expected output of the verification step:

  ...
  [1/8] 0xba522ec5454bbde9b7105c89b387633e52223d1e82b5326b9061b3d7eaadde8d … createFungibleToken → 0 trailing bytes [SUCCESS]
  [2/8] 0xc2cf744f20cd0fe65c6004a4d83633d035af4e5fbba0ae212935ab589b178e14 … createFungibleToken → 32 trailing bytes (0xdeadbeefcafebabedeadbeefcafebabedeadbeefcafebabedeadbeefcafebabe = "................................") [CONTRACT_EXECUTION_EXCEPTION]
  [3/8] 0xd572837d6eecdc2e4e699ab5773e005743e193b07a581f905fb27560fcb3603c … createFungibleToken → 0 trailing bytes [SUCCESS]
  [4/8] 0x9600ed68ad607aa85717357f27abefeadd71b403f00376e5f40cb97908d52574 … createFungibleToken → 32 trailing bytes (0xdeadbeefcafebabedeadbeefcafebabedeadbeefcafebabedeadbeefcafebabe = "................................") [SUCCESS → INVALID_OPERATION]
  [5/8] 0x94c5ab4be7e331c8a9f255186d8a1793eb5ac874fd8334dab4b10d94ff36250d … transferToken → 0 trailing bytes [SUCCESS]
  [6/8] 0x94adab9bf3ca08e4213fdbd5c48aae394eb680ba1c8add3b2dba9a07591eee0e … transferToken → 32 trailing bytes (0xdeadbeefcafebabedeadbeefcafebabedeadbeefcafebabedeadbeefcafebabe = "................................") [CONTRACT_EXECUTION_EXCEPTION]
  [7/8] 0xd291804c0cfc76570ac437095334478ebb9b672ba61cce6368ed1722e00238c1 … transferToken → 0 trailing bytes [SUCCESS]
  [8/8] 0x027efcbe69c6b4d94ad3bcec35314d184f2332e628998a016d89dd213b206525 … transferToken → 32 trailing bytes (0xdeadbeefcafebabedeadbeefcafebabedeadbeefcafebabedeadbeefcafebabe = "................................") [SUCCESS → INVALID_OPERATION]

Note: For indirect calls (steps 3, 4, 7, 8) the outer transaction targets the Hip1342Caller contract, not HTS directly. The Hip1342Caller is calling the HTS system contract injecting the trailing data.

Repository Layout

docs/
  breaking-change-impact-analisys.md   Process document: how to run a breaking-change impact analysis
  impact-analysis-hip-1342.md          Results of the impact analysis for HIP-1342

network-data/
  analysis-results.csv                 Final list of transactions impacted by HIP-1342
  contract-execution-exceptions.csv    Resolved transactions confirmed as CONTRACT_EXECUTION_EXCEPTION or CONTRACT_REVERT_EXECUTED + INVALID_OPERATION.
  ethereum-direct-calls.csv            EOA → system-contract calls that failed (CONTRACT_EXECUTION_EXCEPTION). Extracted June 10, 2026.
  ethereum-nested-calls.csv            Contract → system-contract nested calls that failed. Extracted June 10, 2026.
  sql-queries.sql                      Queries run against the mirror node PostgreSQL database
  test-hip-1342-results.csv            (not committed) Generated by test-hip-1342.js; input for check-trailing-calldata.js

scripts/
  check-contract-execution-exceptions.sh   Check transactions and move them when compatible exceptions emerge
  check-trailing-calldata.js               Detects trailing bytes in each transaction's calldata
  test-hip-1342.js                         Live testnet test: correct vs. trailing-byte calls to HTS

Additional Links

• HIP-1342 discussion