fix(fault-proof): follow genesis-rooted catch-up chains to their tip#927
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After a long L2 finalized-head stall, the proposer can prune its cache down to the anchor game and rebuild the backlog as a genesis-rooted chain (parent = u32::MAX, since the contract reverts when a new game's parent is the current anchor). compute_canonical_head pinned the head to the root of that alternative chain instead of following it to the tip, so the canonical head could not advance and game creation stalled until the anchor caught up. Follow each qualifying alternative-chain root (genesis-rooted, or a lower parent index than the anchor head) to its highest-block tip. Extract the selection into ProposerState::select_canonical_head and cover it with unit tests.
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KamiD
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Jun 11, 2026
…inctlabs#927 Upstream replaced succinctlabs#926 with succinctlabs#927, adding two increments on top of the same core selection logic: - Emit a tracing::debug! when the canonical head is chosen from a catch-up chain outside the anchor subtree, so operators can tell the proposer is recovering on a non-descendant lineage. - Cover the multi-chain case in a new unit test (multiple_catchup_chains_select_highest_tip): after repeated stall/recovery cycles, several genesis-rooted catch-up chains can sit in the cache, and the head must be the highest tip pooled across all of them, not the tip of the chain whose root sits highest.
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Supersedes #926.
#926 is a cross-repo PR from
celo-org:seolaoh/proposer-canonical-head-catchup-upstream, and CI on cross-repo PRs does not receive the required env/secrets. The source fork branch has also since been deleted. This PR re-opens the same change from a same-repo branch so CI can run with full secrets.What's preserved
seolaoh's original #926 commit is included unchanged:
fix(fault-proof): follow genesis-rooted catch-up chains to their tipWhat's added
test(fault-proof): cover canonical head selection across multiple catch-up chains— addsmultiple_catchup_chains_select_highest_tipto thecanonical_headunit tests. Repeated stall/recovery cycles can leave several genesis-rooted chains in the cache at once, andselect_canonical_headmust return the highest tip across all qualifying chains pooled together; the original five tests only cover a single alternative chain.chore(fault-proof): log catch-up chain head selection at debug level— adds atracing::debug!inProposerState::select_canonical_headwhen the override path selects the head, so operators can tell from logs that the proposer is following a catch-up chain outside the anchor subtree.Verification
cargo fmt --all -- --checkcargo check -p op-succinct-fp --libcargo test -p op-succinct-fp --lib— 52/52 pass, including all 6canonical_headtestscargo clippy --all-features --all-targets -- -D warnings -A incomplete-features— zero warningsCredit
Original PR by @seolaoh: #926. Equivalent change merged on Celo's side as celo-org#144 and soaked on their internal testnet.