ADR-0004: Sequencing: single sequencer + forced inclusion from day one

Launch with a single operator sequencer, stated plainly as a liveness and ordering monopoly — made survivable, not custodial, by forced inclusion shipped in the same release (hard ceiling ≤ 24 h, then…

Status: accepted. Dated 2026-08-13.

Status: accepted (2026-08-13) · Prompt: §5 D4, §6 C2/C8, Appendix E2–E3

Decision

Launch with a single operator sequencer, stated plainly as a liveness and ordering monopoly — made survivable, not custodial, by forced inclusion shipped in the same release (hard ceiling ≤ 24 h, then derivation includes the transaction regardless of the sequencer).

Ordering accountability from the start:

• Signed receipts per accepted order/transaction {hash, batch, position, l2_slot, sig}; equivocation (two receipts for one position, or batch contradicting receipt) is provable by the holder and slashable.
• Published per-market ordering rule (App. E3): a deterministic function of published data — FBA per slot, or FCFS with cancel priority. "We order fairly" is not a policy.

Rejected

• Shared/based sequencing at launch — forfeits the latency accountability story for markets (App. E10) and adds a dependency while the core is unproven.
• PoS sequencer set at launch — decentralisation theatre before proofs enforce is risk without benefit; it arrives with staking+slashing when Stage criteria say so (§9).

Reversal trigger

Stage progression per §9: rotating set → bonded set, each gated on published criteria.

Confirmed 2026-09-02 (owner decision)

The system class stays a rollup (ADR-0001 stands). The staked sequencer set is the next stage and the only "validator set" Solieum will have: it decides ordering, never finality. Finality stays with Solana via the settlement program and fraud proofs; an L2 validator set deciding state would make Solieum a sidechain and is out of scope.