Let us encode $λ$-expressions into interaction nets as

with both abstraction and application nodes being interaction combinator $γ$.

For sharing nodes, let us choose such an agent $ψ$ that

$$ ψ[γ(x, y), γ(z, t)] \bowtie γ[δ(x, z), δ(y, t)] $$

and

$$ ψ[δ(x, y), δ(z, t)] \bowtie δ[ψ(x, z), ψ(y, t)], $$

with interaction combinator $δ$ involved.

Please provide a counterexample to the resulting interaction system's optimality by Levy.