Improvement A is a boundary-condition clarification, not a new validation layer. The current base says to compare the next segment with the remaining allowance before addition, but an explicit equality example removes a common off-by-one ambiguity: with one hundred twenty bytes already counted under an inclusive one hundred twenty-eight-byte ceiling, an eight-byte segment is accepted and leaves zero, while a nine-byte segment is rejected before addition. Its limitation is scope: the example is correct only after the contract has named an inclusive ceiling and the counter is observing the exact representation being limited. It does not decide whether transport framing, compression, or other transformations belong in that count.

Improvement B is an independent representation-identity check and recovery procedure. At the transport handoff, count and digest the exact bytes selected for transmission, then compare both with the retained or preflight body. A mismatch invalidates that attempt. Recovery should discard partially consumed streams and rebuild only from immutable replayable inputs while preserving the frozen boundary, headers, part order, charset, metadata, and transformation stage; semantic validation and exact body measurement must then run again before any retry. Its limitations are distinct from A: a matching count and digest can verify local byte identity at the observed handoff but cannot prove that a remote peer received or accepted the body. Recovery cannot make a non-replayable input replayable, and a retry after any bytes may have reached a peer also requires the surrounding operation to have a safe idempotency policy.

These conclusions are reasoned from the selected guidance and byte-stream invariants. No executable tests, packet capture, runtime transmission, external source, or review approval was used. Tests would still be needed for exact equality, one-byte overflow, handoff mismatch detection, partially consumed input handling, and retry behavior.

The selected published guidance correctly separates Unicode field semantics from the exact multipart body byte ceiling and requires measurement and transmission of the same representation. Two independent refinements appear useful. First, sharpen the inclusive boundary rule with a concrete segment example: after one hundred twenty bytes under a one hundred twenty-eight-byte maximum, an eight-byte next segment is accepted and leaves zero remaining, while a nine-byte segment is rejected before addition. This makes clear that equality is valid and also preserves the overflow-safe comparison. Second, add a verification and recovery procedure at the transport handoff: count and digest the exact body bytes selected for transmission, compare both values with the retained or preflight representation, and treat any mismatch as invalidating that body attempt. Recovery should discard partially consumed streams, reconstruct only from immutable replayable inputs with the boundary and serialization choices still frozen, then repeat semantic validation and exact body measurement before retrying. These are reasoned maintenance proposals; no executable test, packet capture, source citation, or review approval is claimed. Would both additions improve the procedure while keeping its representation boundary precise?