have : ¬⊤ ∈ ⛓️[(encode (Code.verum : Code L)).pair s] := by
  have : ⛓️[(encode Code.verum).pair s + 1] ≺[Code.verum] ⛓️[(encode Code.verum).pair s] := chain_spec' nwf _ _
  generalize ⛓️[(encode (Code.verum : Code L)).pair s + 1] = Δ' at this
  rcases this; assumption
L : Language
inst✝³ : (k : ℕ) → DecidableEq (L.Func k)
inst✝² : (k : ℕ) → DecidableEq (L.Rel k)
inst✝¹ : (k : ℕ) → Encodable (L.Func k)
inst✝ : (k : ℕ) → Encodable (L.Rel k)
T : Theory L
Γ : Sequent L
nwf : ¬WellFounded (SearchTree.Lt T Γ)
s : ℕ
h : ⊤ ∈ ⛓️[s]
this : ⊤ ∈ ⛓️[(encode Code.verum).pair s]
⊢ False
L : Language
inst✝³ : (k : ℕ) → DecidableEq (L.Func k)
inst✝² : (k : ℕ) → DecidableEq (L.Rel k)
inst✝¹ : (k : ℕ) → Encodable (L.Func k)
inst✝ : (k : ℕ) → Encodable (L.Rel k)
T : Theory L
Γ : Sequent L
nwf : ¬WellFounded (SearchTree.Lt T Γ)
s : ℕ
h : ⊤ ∈ ⛓️[s]
this✝ : ⊤ ∈ ⛓️[(encode Code.verum).pair s]
this : ⊤ ∉ ⛓️[(encode Code.verum).pair s]
⊢ False