perf(l1): hold the rollup config in immutables instead of storage

[spalladino]

This is the bottom of the Fast Inbox stack: it targets project/fast-inbox directly and is independently mergeable — nothing in it depends on the inbox work above it.

Context

Every field of RollupConfig — vkTreeRoot, protocolContractsHash, version, feeAsset, feeAssetPortal, epochProofVerifier, inbox, outbox — is written exactly once in the Rollup's constructor and has no setter anywhere in src/. They were nonetheless kept in storage, so every read paid a cold SLOAD. propose paid one, submitEpochRootProof paid six.

Approach

Move all eight into immutables and drop config from RollupStore.

Libraries cannot read a contract's immutables, and the *ExtLib libraries here are external (delegatecalled), so they cannot either. The values are assembled into a memory RollupConfig by RollupCore._getRollupConfig() and threaded down as parameters: the full struct into the epoch-proof path, the IInbox into propose, and the fee asset into the reward claims. Propose needed its IInbox bundled with the existing checkBlob flag into a ProposeConfig struct — a seventh scalar parameter pushed ProposeLib.propose over the stack limit, and a memory struct costs one slot instead of two.

config was the last member of RollupStore, so tips, archives and tempCheckpointLogs keep slots 0–2 and every raw-slot consumer of keccak256("aztec.stf.storage") is unaffected — all of them use offsets ≤ +2. The two that used +3/+4 were RollupContract.getVkTreeRoot and getProtocolContractsHash in the TS client, which now call the contract getters that IRollup has exposed since #22563.

The second commit is bytecode budget, not gas. Each immutable read inlines a 32-byte push, which grew Rollup's runtime code to within 148 bytes of the EIP-170 limit. Rollup.validateHeaderWithAttestations was decoding seven parameters, building a ValidateHeaderArgs (which embeds a full ProposedHeader) in memory, resolving the mana min fee through two delegatecall hops, and re-encoding four arguments — all in the Rollup's own runtime code. Forwarding the parameters straight through and assembling the struct in RollupOperationsExtLib frees 629 bytes. The fee value is unchanged: RewardExtLib.summedMinFee and .getManaMinFeeComponentsAt are one-line forwarders to the FeeLib / ProposeLib functions the ExtLib now calls directly.

Gas

Benchmark	Before	After	Δ
propose (no validators)	199,366	197,433	−1,933
submitEpochRootProof (no validators)	991,032	980,225	−10,807
propose (100 validators)	327,774	325,847	−1,927
submitEpochRootProof (100 validators)	1,572,081	1,561,291	−10,790
aggregate3 (100 validators)	376,665	374,738	−1,927

The config getters lose their cold SLOAD outright — getInbox 2,543 → 878, getVersion 1,447 → 852, getOutbox 2,521 → 856. A handful of unrelated views move by 22–44 gas as the Rollup's selector dispatch shifts. Deployment also drops eight SSTOREs.

Rollup runtime bytecode ends at 23,799 against the 24,576 limit — 777 bytes of margin, against 886 before this change.

Note on the regenerated gas_report.json: call counts on a few entries drop by 36 because the three tests that fail only under FORGE_GAS_REPORT (testExtraBlobs, testRevertInvalidCoinbase, testRevertInvalidTimestamp — all failing identically on the base commit) abort at a slightly different point. Per-call gas for those entries is unchanged.

Node compatibility

Node binaries already in the field read vkTreeRoot and protocolContractsHash from raw slots +3/+4. Against a rollup deployed from this branch those slots are zero, so such a node's waitForCompatibleRollup reports a VK mismatch and sits in standby. #25313 lands the getter-based read on the v5 line so binaries cut from it work against a rollup deployed from either version; it does nothing for binaries already released, so this needs sequencing against any node rollout.

[AztecBot]

Flakey Tests

🤖 says: This CI run detected 1 tests that failed, but were tolerated due to a .test_patterns.yml entry.

\033FLAKED\033 (8;;http://ci.aztec-labs.com/c90cbaa08cce1b9c�c90cbaa08cce1b9c8;;�): yarn-project/kv-store/scripts/run_test.sh src/sqlite-opfs/internal/ordered-binary-browser.test.ts (1s) (code: 0)