Snowbridge Referendum

Steps

1. Generate the preimage

Run the snowbridge preimage tool:

cd <snowbridge-control-dir>/preimage && cargo run --features <network> -- <subcommand> [extra-flags]

• The --features flag must match the network: polkadot, kusama, westend, or paseo.
• Capture the hex output (the line starting with 0x) from stdout.
• Capture the preimage hash and size from stderr (lines like Preimage hash: 0x... and Preimage size: N).
• Save the hex to preimage.txt in the opengov-cli project root.

2. Run opengov-cli

From the opengov-cli directory:

cargo run -- submit-referendum --proposal preimage.txt --network <network> --track <track> --output calldata

Parse the output to extract these hex values:

• Fellowship referendum call: line after "Open a Fellowship referendum to whitelist the call:" (only for whitelisted-caller track)
• Governance batch call: line after "Batch to submit on Polkadot Asset Hub:" (or the relevant chain)
• Collectives batch call: line after "Batch to submit on Polkadot Collectives Chain:" (only for whitelisted-caller track)

For --track root, there is no fellowship call or collectives batch.

3. Test with referenda-tester

This is the critical verification step. The referenda-tester simulates the full governance flow using Chopsticks.

Determine additional chains

If the preimage sends XCM to other chains (e.g. BridgeHub), add them via --additional-chains. This is essential for verifying the XCM roundtrip completes successfully.

Common patterns:

• Preimage contains PolkadotXcm::send to BridgeHub (e.g. mint, replay, upgrade commands): add BridgeHub
• Preimage is AH-local only (e.g. treasury spend, register asset): no additional chains needed

To determine this: check if the preimage tool's subcommand uses send_xcm_bridge_hub() in commands.rs. If so, BridgeHub is needed.

Whitelisted-caller track (default)

npx github:karolk91/polkadot-referenda-tester test \
  --governance-chain-url wss://asset-hub-polkadot-rpc.n.dwellir.com \
  --fellowship-chain-url wss://polkadot-collectives-rpc.polkadot.io \
  --call-to-create-governance-referendum '<governance-batch-hex>' \
  --call-to-create-fellowship-referendum '<collectives-batch-hex>' \
  --additional-chains wss://bridge-hub-polkadot-rpc.n.dwellir.com \
  --verbose

Root track

npx github:karolk91/polkadot-referenda-tester test \
  --governance-chain-url wss://asset-hub-polkadot-rpc.n.dwellir.com \
  --call-to-create-governance-referendum '<governance-batch-hex>' \
  --additional-chains wss://bridge-hub-polkadot-rpc.n.dwellir.com \
  --verbose

Omit --fellowship-chain-url and --call-to-create-fellowship-referendum for root track. Omit --additional-chains if the preimage doesn't send XCM to other chains.

Testnet URLs

4. Verify the referenda-tester output

Check the output for these success indicators:

Governance dispatch

• Both referenda executed successfully! (or single referendum for root track)
• Scheduler.Dispatched with result: success
• Whitelist.WhitelistedCallDispatched with result: success (whitelisted-caller track)

XCM to BridgeHub (if applicable)

• PolkadotXcm.Sent with destination Parachain: 1002 (BridgeHub)
• XcmpQueue.XcmpMessageSent on Asset Hub
• Outbound HRMP message to recipient 1002 in the Chopsticks logs

BridgeHub processing (if additional chain added)

• MessageQueue.Processed with origin: Sibling(1000) and success: true
• PolkadotXcm.Sent from BridgeHub back to AH (destination Parachain: 1000)
• XcmpQueue.XcmpMessageSent on BridgeHub
• Outbound HRMP message to recipient 1000 in the Chopsticks logs

For commands that mint/deposit assets (e.g. mint-feb2026, replay-sep2025), verify the return XCM contains:

• ReserveAssetDeposited with the correct asset and amount
• DepositAsset with the correct beneficiary
• The asset location should be the expected foreign asset (e.g. Ethereum ERC20)

Failure investigation

If the test fails:

• Check Scheduler.Dispatched result for errors
• Look for XcmpQueue.Fail or MessageQueue.ProcessingFailed events
• Check BridgeHub events for Transact failures
• Inspect the Chopsticks outboundHrmpMessage logs to see if XCM was sent

5. Report results

Print a summary including:

• Preimage hash and size
• Whether all referenda passed
• Whether XCM roundtrip completed (if applicable)
• The final call data for posting:
  • Governance batch (submit on Asset Hub)
  • Collectives batch (submit on Collectives, whitelisted-caller only)
• Any issues found during testing

If everything passes, the calls are ready for on-chain submission.