papers/lp-210-block-stm/sections/05-composition.tex

\section{Composition With Sibling LPs}

\begin{table}[h]
\centering
\small
\begin{tabular}{@{}lp{9cm}@{}}
\toprule
\textbf{LP} & \textbf{Composition} \\
\midrule
LP-010 & Block-STM 3.0 / QuasarSTM (GPU lane-aware variant; LP-210 is the CPU floor) \\
LP-022 & ZAP wire protocol (tx ZAP frame format read by LP-210) \\
LP-200 & ZAP Stack umbrella; LP-210 instantiates the layer-7 executor \\
LP-202 & MVCC primitives, atomic commit, speculative execution contract \\
LP-203 & GPU-native verify (the LP-209 wave LP-210 consumes inherits cert-tier wall-clock from LP-203's GB10 sm\_120 measurements) \\
LP-204 & Per-L1 LP-210 instantiation per chain-VM \\
LP-208 & DAG mempool / header DAG (substrate that produces the txs) \\
LP-209 & Mysticeti-style total-order on DAG (the wave commit contract LP-210 executes) \\
LP-211 & Cross-shard atomic Polaris cert (cross-shard Phase-4 staging) \\
\bottomrule
\end{tabular}
\caption{Composition of LP-210 with sibling LPs.}
\label{tab:composition}
\end{table}

\subsection{With LP-202}

LP-210's speculative execute IS LP-202's speculative execution
pattern applied at the per-tx granularity instead of per-block. The
MVCC snapshot is the same primitive; the unwind on conflict is the
same \texttt{txn.Discard()}; the atomic commit at end-of-wave is the
same overlay commit. LP-210 is one specific use of LP-202's
primitives -- the canonical execution-layer use.

\subsection{With LP-209}

LP-209 commits a wave; LP-210 executes the wave's txs. The contract:

\begin{table}[h]
\centering
\small
\begin{tabular}{@{}p{6.5cm}p{6.5cm}@{}}
\toprule
\textbf{LP-209 produces} & \textbf{LP-210 consumes} \\
\midrule
Totally ordered tx list with \texttt{tx\_index} per tx & the execution order tiebreak for re-execution in Phase~3 \\
Wave's prior-root ZapDB pointer & the snapshot from which all goroutines start \\
Wave's tx count $N$ & the goroutine pool size $=$ \texttt{min(GOMAXPROCS, $N$)} \\
\bottomrule
\end{tabular}
\caption{LP-209 / LP-210 contract.}
\label{tab:lp209-210}
\end{table}

LP-209 produces a wave; LP-210 produces a new ZapDB root + a per-tx
verdict slice. The cert at LP-217 covers the new root, NOT the
verdict slice -- the verdicts are reproducible from the wave bytes +
prior root by any conformant LP-210 implementation, so they are not
part of the cert payload.

\subsection{With LP-211 (cross-shard)}

When a wave contains cross-shard tx groups (LP-211), LP-210 executes
the per-shard portions independently up through Phase~4 (atomic
commit). At Phase~4, instead of committing immediately, the
cross-shard portions \textbf{stage} their overlays and emit
prepare-acks per LP-211. The actual commit happens when the
parent-L1 cross-shard cert at LP-211 finalizes; if any sibling shard
refuses, all participating shards' overlays are unwound via LP-202.

\begin{table}[h]
\centering
\small
\begin{tabular}{@{}p{2.5cm}p{4cm}p{5cm}@{}}
\toprule
\textbf{Phase 4 mode} & \textbf{Trigger} & \textbf{Action} \\
\midrule
Local-commit & wave contains no cross-shard txs & apply overlay to ZapDB immediately \\
Staged-prepare & wave contains 1+ cross-shard txs & stage overlay; emit \texttt{CrossShardPrepareAck} per cross-shard tx; intra-shard txs in the same wave still local-commit \\
\bottomrule
\end{tabular}
\caption{Phase-4 modes.}
\label{tab:phase4}
\end{table}

The same wave can contain a mix of intra-shard and cross-shard txs.
The intra-shard txs commit immediately under local-commit; the
cross-shard portions stage and wait. This is the canonical
Block-STM $\times$ 2PC composition -- no special tx-type at the
LP-210 layer beyond the \texttt{cross\_shard} envelope kind.

\section{Failure Modes}

\begin{table}[h]
\centering
\small
\begin{tabular}{@{}p{3cm}p{3cm}p{4cm}p{3.5cm}@{}}
\toprule
\textbf{Failure} & \textbf{Trigger} & \textbf{Effect} & \textbf{Recovery} \\
\midrule
Tx execution traps & tx logic (out-of-gas, opcode error) & write\_set empty; marked invalid; no commit & tx dropped; no state change \\
Tx signature invalid & LP-208 normally catches; LP-210 re-checks & marked invalid & dropped \\
Goroutine panics during execute & bug in VM opcode handler & per-goroutine recover; tx marked invalid & dropped; bug filed; chain continues \\
All txs conflict (worst-case contention) & adversarial; one hot key & Phase~3 serializes wave & commits at single-threaded rate \\
ZapDB commit fails (disk full, I/O) & infrastructure & LP-202 atomic unwind; ZapDB root unchanged & node halts at last committed wave; bootstrap recovery \\
Wave is cross-shard, sibling rolls back & LP-211 refuses commit & per-shard rollback; LP-210 per-tx writes unwound & cross-shard group dropped; per-shard waves move forward \\
\bottomrule
\end{tabular}
\caption{Failure modes.}
\label{tab:failures}
\end{table}

\section{Activation Marker}

\begin{verbatim}
activates:      2025-12-25T16:20:00-08:00
activates-unix: 1766708400
\end{verbatim}

\section{Backwards Compatibility}

None. Applies to wave execution from the genesis block of the new
final Lux network onward.