Block building fails after runtime upgrade with polkadot-stable2512 (setValidationData 2-arg format + slot mismatch)

[manuelmauro]

Description

After upgrading a runtime from a pre-stable2512 version to a stable2512-based runtime using chopsticks, block building fails with two issues:

1. Cannot decode parent block validation data after upgrade

After the runtime upgrade, chopsticks tries to read the parent block's parachainSystem.setValidationData extrinsic to extract validation data, but fails because the API metadata has changed to the new 2-argument format while the parent block uses the old 1-argument format:

WARN: Failed to get validation data from block 15521320 Error: createType(GenericExtrinsic):: createType(ExtrinsicV4):: createType(Call):: Call: failed decoding parachainSystem.setValidationData:: Struct: failed on args: {"data":"...","inbound_messages_data":"..."}

2. Relay slot mismatch causes runtime panic

After the upgrade, the relay chain slot and parachain timestamp become out of sync by 1 slot, causing a runtime panic:

Runtime has aborted: "panicked at pallets/async-backing/src/lib.rs:137:3:
assertion `left == right` failed: The parachain timestamp slot must match the relay chain slot.
  left: Slot(295523947)
  right: Slot(295523948)"

The +1 relay slot adjustment from #959 seems to cause the relay slot and parachain timestamp to diverge after a runtime upgrade.

Reproduction

1. Fork a live Moonbase Alpha chain using chopsticks 1.2.7
2. Apply a runtime upgrade from a pre-stable2512 runtime to a stable2512 runtime
3. Try to create blocks after the upgrade

Related

• Block building fails due to recent parachain-system changes #940 (original setValidationData 2-arg support)
• Update deps and support new setValidationData format #941 (fix merged in 1.2.0)
• Can't build block on KAH/PAH with new runtime #958 (KAH/PAH block building failure)
• Fix(parachain): Add Fallback for Validation Data Retrieval and Adjust Relay Slot #959 (fallback mechanism + slot adjustment)

Versions

• chopsticks: 1.2.7
• Runtime: Moonbeam stable2512 (specVersion 4300)
• polkadot-sdk: stable2512