1. Introduction

Objective: open a sovereign channel’s writer set so that joining requires staking, not an incumbent vote. Today the set is the accredited_keys committee, rotating round-robin, changed only by incumbent threshold signature ([1.5.0] Mantle , [1.1.0][Overview] Bedrock Architecture ).

Conclusion up front:

• Admission moves to L2: lock a fixed amount through an L2 transaction, enter the registry; K locks = K rotation positions.
• Turn assignment stays the existing L1 rotation (companion survey: Turn-assignment Mechanisms for Channel Sequencing, Turn-assignment mechanisms for channel sequencing ]; this document cites its entries S1-S11).
• Enforcement stays the envelope floor plus objective-condition delisting.
• The only L1 revisions designed here are on the key-list update path, which open admission turns into the hot path (section 6).
• Admission is stake-gated from day one; it becomes fully permissionless once the admission counter-incentive (D-M3/D-M6) is designed and live. Until then registrations are still incumbent-executed (the T3 fork).

Binding requirements:

• The channel stays an envelope-only ordering service: never reads inscription bytes, never runs the state transition function (STF).
• L1 validation stays lightweight: the append check is ~one signature verify; additions must be comparably cheap; heavy machinery lives on L2.
• Follower validation load (the on-chain-mempool model) must not grow substantially.
• The log linearizes at append (parent == tip admits one successor), so selection owes liveness and attribution, not safety.
• No new cryptography is introduced, now or in a planned second iteration.
• Design point: N = 100-1000 sequencers (02/07/2026 discussion).

The two-layer spine:

• L1 (identical for every zone): accredited_keys; slot-clocked single-winner rotation with posting_timeout takeover; envelope check; CHANNEL_CONFIG. All EXISTS.
• L2 (per-zone, optional; a zone that keeps its committee permissioned adopts none of it): admission, registry, lifecycle, incentives, enforcement beyond the floor. All UNBUILT; this document’s work.
• Flow: L2 lock -> registry entry -> epoch-batched key-list update -> L1 list -> rotation assigns turns -> envelope check at append -> zone validates content, skips garbage.

Legend: * = needs an experiment. Tags: EXISTS (in code, master @ 56a74d2bb), UNBUILT (net-new); “rejected”/“deferred” qualify an option’s standing; “mixed” spans both. [RECOMMEND] = this document’s pick; [PROPOSE] = tentative, for review. N = registered sequencers; K = positions held by one sequencer.