proofs
Provedalphabaguettebaguette-zv2

Attention-sublayer increment ≤ (row ℓ₁ norm of W_o) × (value bound), for the existing architecture

For all T,d∈N\htmlData{mx=1}{T, d \in \htmlData{mx=0}{\mathbb{N}}}, w:Fin⁡ T→R\htmlData{mx=5}{w : \htmlData{mx=2}{\htmlData{mx=0}{\operatorname{Fin}}\,\htmlData{mx=1}{T}} \mathrel{\htmlData{mx=4}{\to}} \htmlData{mx=3}{\mathbb{R}}}, V:Fin⁡ T→Fin⁡ d→R\htmlData{mx=9}{V : \htmlData{mx=2}{\htmlData{mx=0}{\operatorname{Fin}}\,\htmlData{mx=1}{T}} \mathrel{\htmlData{mx=8}{\to}} \htmlData{mx=5}{\htmlData{mx=3}{\operatorname{Fin}}\,\htmlData{mx=4}{d}} \mathrel{\htmlData{mx=7}{\to}} \htmlData{mx=6}{\mathbb{R}}}, Wo:Fin⁡ d→R\htmlData{mx=5}{\mathit{Wo} : \htmlData{mx=2}{\htmlData{mx=0}{\operatorname{Fin}}\,\htmlData{mx=1}{d}} \mathrel{\htmlData{mx=4}{\to}} \htmlData{mx=3}{\mathbb{R}}} and M∈R\htmlData{mx=1}{M \in \htmlData{mx=0}{\mathbb{R}}}, if ∀j, 0≤w(j)\htmlData{mx=4}{\forall j,\ 0 \mathrel{\htmlData{mx=3}{\leq}} \htmlData{mx=2}{\htmlData{mx=0}{w}(\htmlData{mx=1}{j})}}, ∑jw(j)=1\htmlData{mx=3}{\sum_{j} \htmlData{mx=2}{\htmlData{mx=0}{w}(\htmlData{mx=1}{j})}} \mathrel{\htmlData{mx=4}{=}} 1 and ∀j,k, ∣V(j,k)∣≤M\htmlData{mx=7}{\forall j, k,\ \htmlData{mx=4}{\left\lvert \htmlData{mx=3}{\htmlData{mx=0}{V}(\htmlData{mx=1}{j}, \htmlData{mx=2}{k})} \right\rvert} \mathrel{\htmlData{mx=6}{\leq}} \htmlData{mx=5}{M}}, then

∣∑kWo(k)⋅∑jw(j)⋅V(j,k)∣≤(∑k∣Wo(k)∣)⋅M\htmlData{mx=14}{\left\lvert \htmlData{mx=13}{\sum_{k} \htmlData{mx=12}{\htmlData{mx=2}{\htmlData{mx=0}{\mathit{Wo}}(\htmlData{mx=1}{k})} \cdot \htmlData{mx=11}{\sum_{j} \htmlData{mx=10}{\htmlData{mx=5}{\htmlData{mx=3}{w}(\htmlData{mx=4}{j})} \cdot \htmlData{mx=9}{\htmlData{mx=6}{V}(\htmlData{mx=7}{j}, \htmlData{mx=8}{k})}}}}} \right\rvert} \mathrel{\htmlData{mx=22}{\leq}} \htmlData{mx=21}{\left(\htmlData{mx=19}{\sum_{k} \htmlData{mx=18}{\left\lvert \htmlData{mx=17}{\htmlData{mx=15}{\mathit{Wo}}(\htmlData{mx=16}{k})} \right\rvert}}\right) \cdot \htmlData{mx=20}{M}}
What the notation means · or point at any symbol
NNatural numbers
The natural numbers 0, 1, 2, …. In Lean they start at 0. (ℕ)
x ∈ TVariables
T, d range over natural numbers: the statement must hold for every choice. ((T d : ℕ))
Fin
Fin: a definition from the library, not special notation. Its name is its meaning; open it in Lean to see how it is defined. (Fin)
f(x)Function application
Fin applied to T. Lean writes f x; papers write f(x). (Fin T)
⟹Implies
If Fin(T), then ℝ. (Between types, A → B is the type of functions from A to B.) (Fin T → ℝ)
∀For all
The statement after the comma holds for every j. (∀ j, 0 ≤ w j)
∑Summation
Add up w(j) for every j. (∑ j, w j)
=Equality
∑ j, w(j) and 1 are the same. (∑ j, w j = 1)
≤At most
0 is less than or equal to w(j). (0 ≤ w j)
|x|Absolute value
The size of V(j, k) without its sign. (|V j k|)
RReal numbers
The real numbers: every point on the number line. (ℝ)
·Multiplication
w(j) times V(j, k). (w j * V j k)

Composes the convex-combination and row-sum bounds: with softmax weights and |V| ≤ M, each output coordinate of attention followed by W_o is ≤ (Σ_k|W_o,k|)·M. Here M ≤ (row ℓ₁ norm of W_v)·√n by the RMSNorm coordinate bound. A runtime residual certificate for Baguette as it is, computable from weight row sums in the optimizer, with no architecture change. Part of 'Baguette-Z v2' (revision after the hostile review).

How it was proved

Proved
3 October 2026
By
Ajax, with the agent “Baguette math & proofs (Claude Code, 2026-10-03)”
Checked by
Lean's kernel (Lean 4.33.1, with Mathlib); the proof is signed and replays offline
Axioms
Classical.choice, Quot.sound, propext
Proof
23 lines of Lean
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