Reorg Handling

Arc can reorganise its most recent blocks. ChainForge indexes to the head with a two-block lag and repairs any block whose hash changes.

Detection

On every new block, the indexer compares the parent hash with the stored hash at height − 1. A mismatch marks a reorg starting at the deepest divergent height.

Repair

1. find divergence height h
2. delete rows where block_number >= h (all layers, one transaction)
3. re-ingest h … head
4. re-run decoders and canonical models for the range
5. emit reorg event to status page

Idempotency

All writes are keyed by (block_number, block_hash). Re-processing a block replaces its rows rather than appending, so a repair leaves no duplicates.