You are an expert Lean4 and formal verification agent proving a Lean4 theorem. Your output **must** strictly adhere to the specified format.

### Input Information
You will receive the following components, relevant to the target theorem:
* <all_available_defs>: Definitions available from imported modules (either from the current Lean repository or from Mathlib)
* <all_available_lemmas>: Lemmas/theorems available that may assist the proof.
* <local_ctx>...</local_ctx>: The local file context (imports, namespaces, definitions, comments, etc.) from the top of the file up to—but not including—the target theorem or any previously defined local lemmas/theorems.
* <target_theorem>...</target_theorem>: The target theorem statement, ending with `:=`.

**Notes**
1. Definitions include their full bodies, but for definitions whose bodies contain proofs, the proof parts are replaced by `admit` (i.e., admit /- proof elided -/), while the rest of the definition is kept unchanged; lemmas include only their statements.
2. You may freely reference any definition or lemma contained in these tags without redefining them.
3. The tags for available definitions and lemmas (all_available_defs, all_available_lemmas) may be omitted if empty.

### Output Format & Requirements
Your output MUST contain a complete, syntactically correct Lean 4 proof for the target theorem.

**Strict Output Structure:**
<reasoning> 
...
</reasoning> 

<lean4_invented_lemmas>
-- each lemma is a full Lean 4 declaration with a complete proof
...
</lean4_invented_lemmas>

<lean4_proof>
-- Lean 4 proof body of the target theorem
...
</lean4_proof>

**Requirements:**
1. <reasoning> and <lean4_invented_lemmas> are OPTIONAL. Include them only if they aid proof construction.
2. <lean4_proof> MUST contain only the proof body (tactics/terms), starting by "by", NOT the theorem declaration.
3. <lean4_invented_lemmas> (if present) MUST contain syntactically correct lemma declarations that type checks AND complete proof bodies. Defining a lemma using `axiom` is NOT allowed.
4. <reasoning> contains high-level proof planning.
5. If you create a lemma under <lean4_invented_lemmas> whose name is namespaced (e.g., X.Y.Z), you MUST always refer to it using its fully qualified name. Do NOT rely on shortened names. For example, write rw [X.Y.Z], not rw [Z] for invented lemmas.
6. All Lean 4 code MUST be syntactically correct. No `sorry`, `admit`, or non-Lean text. Comments allowed using `--` or `/- ... -/`.
7. Follow the tags and structure EXACTLY. No extra text before, between, or after the sections.
8. Do NOT wrap invented lemmas in a `mutual` block unless they have genuine mutual recursion. Declare each lemma independently.

### Examples are provided here (example input are under "User Prompt", and example assistant response are under "Agent Response"):
Example 1 ------------------- 
User Prompt:
<all_available_defs>
structure BitVec (w : Nat) where
  /-- Construct a `BitVec w` from a number less than `2^w`.
  O(1), because we use `Fin` as the internal representation of a bitvector. -/
  ofFin ::

  /-- Interpret a bitvector as a number less than `2^w`.
  O(1), because we use `Fin` as the internal representation of a bitvector. -/
  toFin : Fin (hPow 2 w)
</all_available_defs>

<all_available_lemmas>
theorem List.getElem_append_left{α : Type u_1} {l₁ l₂ : List α} {i : Nat} (hn : i < l₁.length) : (l₁ ++ l₂)[i] = l₁[i]
theorem getElem_eq_testBit_toNat (x : BitVec w) (i : Nat) (h : i < w) :
  x[i] = x.toNat.testBit i := rfl
@[simp, grind =] theorem toNat_cons (b : Bool) (x : BitVec w) :
    (cons b x).toNat = (b.toNat <<< w) ||| x.toNat
@[simp, grind =] theorem getLsbD_of_ge (x : BitVec w) (i : Nat) (ge : w ≤ i) : getLsbD x i = false
theorem testBit_toNat (x : BitVec w) : x.toNat.testBit i = x.getLsbD i
</all_available_lemmas>

<local_ctx>
import Mathlib.Computability.NFA
import Mathlib.Data.FinEnum
import Mathlib.Data.Rel
import Mathlib.Data.Vector.Basic
import Blase.AutoStructs.ForLean

open Set
open Mathlib
open SetRel

-- this is better because card is defeq to n
instance (α : Type) : Inter (Language α) := ⟨Set.inter⟩
instance (α : Type) : Union (Language α) := ⟨Set.union⟩

/--
The set of `n`-tuples of bit vectors of an arbitrary width.
-/
structure BitVecs (n : Nat) where
  w : Nat
  bvs : List.Vector (BitVec w) n

def BitVecs.cast (bvs : BitVecs n) (h : n = n') : BitVecs n' :=
  { w := bvs.w, bvs := h ▸ bvs.bvs }

abbrev BitVecs.empty : BitVecs n := ⟨0, List.Vector.replicate n .nil⟩
abbrev BitVecs.singleton {w : Nat} (bv : BitVec w) : BitVecs 1 := ⟨w, bv ::ᵥ .nil⟩
abbrev BitVecs.pair {w : Nat} (bv1 bv2 : BitVec w) : BitVecs 2 := ⟨w, bv1 ::ᵥ bv2 ::ᵥ .nil⟩

/--
The set of `n`-tuples of bit vectors of an arbitrary width, encoded as a list of
bit vectors of width `n`. The width of the encoded bit vectors is the length of
the list.
-/
abbrev BitVecs' (n : Nat) := List (BitVec n)

@[simps]
def dec (bvs' : BitVecs' n) : BitVecs n where
  w := bvs'.length
  bvs := List.Vector.ofFn fun k => BitVec.ofFn fun i => bvs'[i].getLsbD k

@[simp]
</local_ctx>

<target_theorem>
lemma dec_snoc n (bvs' : BitVecs' n) (a : BitVec n) :
  dec (bvs' ++ [a]) =
    { w := bvs'.length + 1
      bvs := List.Vector.ofFn fun k =>
        BitVec.cons (a.getLsbD k) ((dec bvs').bvs.get k) } :=
</target_theorem>

Agent Response:
<reasoning> 
The goal is to understand what `dec` does after appending one more bitvector `a` to `bvs'`. By definition, `dec` builds a width `= length` and a vector of bitvectors whose `i`-th bit at position `k` is `bvs'[i].getLsbD k`. So for `bvs' ++ [a]`, we expect the width to increase by 1 and each resulting bitvector to be `BitVec.cons` of the new bit coming from `a`.

First, I use `ext` twice: once on the record to focus on the `bvs` field, and once on the resulting bitvector. This reduces everything to a pointwise statement:
for fixed `k` and `i` with `i < bvs'.length + 1`,
the bit `(bvs' ++ [a])[i].getLsbD k` should match the bit at index `i` of `BitVec.cons (a.getLsbD k) ((dec bvs').bvs.get k)`.

At this point I need a clean description of indexing into `BitVec.cons`: if we have `x : BitVec n`, then `(cons b x)[i]` should give `b` at the new “last” index `n` and `x[i]` otherwise. That motivates an auxiliary lemma `getElem_cons` expressing exactly this behavior, proved via the `testBit`/`toNat` characterization and a case split on `i < n`, `i = n`, `i > n`.

Using `getElem_cons`, the RHS becomes an `if` on whether `i = bvs'.length`. So I split into cases:
- If `i = bvs'.length`, then `(bvs' ++ [a])[i]` is the appended `a`, so both sides reduce to `a.getLsbD k`.
- If `i ≠ bvs'.length`, the bound `i < bvs'.length + 1` forces `i < bvs'.length`. Then `(bvs' ++ [a])[i] = bvs'[i]` by `List.getElem_append_left`, and the RHS takes the “else” branch and likewise gives the bit from `bvs'[i]`. In both subcases, `simp` (plus the definition of `dec`) finishes.

So the whole proof is: `ext` to bit level, unfold `dec` with `simp_all`, rewrite with `getElem_cons`, split on the boundary index `i = length bvs'`, and in the “< length” branch use `List.getElem_append_left` and bounds to line up both sides.
</reasoning> 

<lean4_invented_lemmas>
@[grind =]
theorem getElem_cons {b : Bool} {n} {x : BitVec n} {i : Nat} (h : i < n + 1) :
    (cons b x)[i] = if h : i = n then b else x[i] := by
  simp only [BitVec.getElem_eq_testBit_toNat, BitVec.toNat_cons, Nat.testBit_or]
  rw [Nat.testBit_shiftLeft]
  rcases Nat.lt_trichotomy i n with i_lt_n | i_eq_n | n_lt_i
  · have p1 : ¬(n ≤ i) := by omega
    have p2 : i ≠ n := by omega
    simp [p1, p2]
  · simp only [i_eq_n, ge_iff_le, Nat.le_refl, decide_true, Nat.sub_self, Nat.testBit_zero,
    Bool.true_and, BitVec.testBit_toNat, BitVec.getLsbD_of_ge, Bool.or_false]
    cases b <;> trivial
  · have p1 : i ≠ n := by omega
    have p2 : i - n ≠ 0 := by omega
    simp [p1, p2, Nat.testBit_bool_toNat]
</lean4_invented_lemmas>

<lean4_proof>
by
  ext k i hi <;> simp_all
  rw [getElem_cons]
  split
  next heq => simp_all
  next h =>
    have hlt : i < List.length bvs' := by simp at hi; omega
    rw [List.getElem_append_left hlt]
    simp
</lean4_proof>

### Your task:
<all_available_defs>
Nat in Init.Prelude
Fin in Init.Prelude
Subspace in Mathlib.Algebra.Module.Submodule.Basic
Set in Mathlib.Data.Set.Defs
Set.Ico in Mathlib.Order.Interval.Set.Defs
Submodule in Mathlib.Algebra.Module.Submodule.Defs
Submodule.span in Mathlib.LinearAlgebra.Span.Defs
Polynomial.C in Mathlib.Algebra.Polynomial.Basic
Algebra in Mathlib.Algebra.Algebra.Defs
Field in Mathlib.Algebra.Field.Defs
IsLinearMap in Mathlib.Algebra.Module.LinearMap.Defs
toFun in ToMathlib.Control.Monad.Hom
Submodule.map in Mathlib.Algebra.Module.Submodule.Map
Module.Basis in Mathlib.LinearAlgebra.Basis.Defs
Disjoint in Mathlib.Order.Disjoint
Fact in Mathlib.Logic.Basic
LinearEquiv in Mathlib.Algebra.Module.Equiv.Defs
LinearEquiv.ofBijective in Mathlib.Algebra.Module.Submodule.Equiv
LinearIndependent in Mathlib.LinearAlgebra.LinearIndependent.Defs
LinearMap in Mathlib.Algebra.Module.LinearMap.Defs
LinearMap.codRestrict in Mathlib.Algebra.Module.Submodule.LinearMap
LinearMap.ker in Mathlib.Algebra.Module.Submodule.Ker
Module.Basis.span in Mathlib.LinearAlgebra.Basis.Basic
Set.range in Mathlib.Data.Set.Operations
Submodule.subtype in Mathlib.Algebra.Module.Submodule.LinearMap
Subtype in Init.Prelude
Finsupp in Mathlib.Data.Finsupp.Defs
Finsupp.equivFunOnFinite in Mathlib.Data.Finsupp.Defs
Finset in Mathlib.Data.Finset.Defs
Finset.univ in Mathlib.Data.Fintype.Defs
Ne in Init.Core
NeZero in Init.Data.NeZero
DecidableEq in Init.Prelude
Inhabited in Init.Prelude
Repr in Init.Data.Repr
Fin.cast in Init.Data.Fin.Basic
Fintype in Mathlib.Data.Fintype.Defs
Fintype.card in Mathlib.Data.Fintype.Card
algebraMap in Mathlib.Algebra.Algebra.Defs
Fin.foldl in Init.Data.Fin.Fold
context in Examples.FrankingProtocol
Polynomial in Mathlib.Algebra.Polynomial.Basic
Decidable in Init.Prelude
Eq in Init.Prelude
id in Init.Prelude
reduceDIte in Lean.Meta.Tactic.Simp.BuiltinSimprocs.Core
Module in Mathlib.Algebra.Module.Defs
Nat.succ in Init.Prelude
Polynomial.eval in Mathlib.Algebra.Polynomial.Eval.Defs

def getBit (k n : Nat) : Nat := (n >>> k) &&& 1

noncomputable def sDomain (i : Fin r) : Subspace 𝔽q L :=
  let W_i_norm := normalizedW 𝔽q β i
  let h_W_i_norm_is_additive : IsLinearMap 𝔽q (fun x : L => W_i_norm.eval x) :=
    AdditiveNTT.normalizedW_is_additive 𝔽q β i
  Submodule.map (polyEvalLinearMap W_i_norm h_W_i_norm_is_additive)
    (U 𝔽q β ⟨ℓ + R_rate, h_ℓ_add_R_rate⟩)

noncomputable def normalizedW (i : Fin r) : L[X] :=
  C (1 / (W 𝔽q β i).eval (β i)) * W 𝔽q β i

noncomputable def W (i : Fin r) : L[X] :=
  ∏ u : U 𝔽q β i, (X - C u.val)

def U (i : Fin r) : Subspace 𝔽q L := Submodule.span 𝔽q (β '' (Set.Ico 0 i))

noncomputable def polyEvalLinearMap {L 𝔽q : Type*} [Field L] [Field 𝔽q] [Algebra 𝔽q L]
  (p : L[X]) (hp_add : IsLinearMap 𝔽q (fun x : L => p.eval x)) : L →ₗ[𝔽q] L :=
{
  toFun    := fun x => p.eval x,
  map_add' := hp_add.map_add,
  map_smul' := hp_add.map_smul
}

noncomputable def sDomain_basis (i : Fin r) (h_i : i < ℓ + R_rate) :
    Basis (Fin (ℓ + R_rate - i)) 𝔽q (
      sDomain 𝔽q β h_ℓ_add_R_rate i) :=

def sBasis (i : Fin r) (h_i : i < ℓ + R_rate) : Fin (ℓ + R_rate - i) → L :=
  fun k => β ⟨i + k.val, by admit /- proof elided -/
  ⟩

def binaryFinMapToNat {n : ℕ} (m : Fin n → ℕ) (h_binary : ∀ j: Fin n, m j ≤ 1) : Fin (2^n) :=

def symm (eqv : Equiv pSpec pSpec') : Equiv pSpec' pSpec where
  round_eq := eqv.round_eq.symm
  dir_eq := fun i => by admit /- proof elided -/

@[ext]
structure Equiv {m n : ℕ} (pSpec : ProtocolSpec m) (pSpec' : ProtocolSpec n) where
  round_eq : m = n
  dir_eq : ∀ i, pSpec.dir i = pSpec'.dir (Fin.cast round_eq i)
  typeEquiv : ∀ i, pSpec.«Type» i ≃ pSpec'.«Type» (Fin.cast round_eq i)

@[ext]
structure ProtocolSpec (n : ℕ) where
   
  dir : Fin n → Direction
   
  «Type» : Fin n → Type
deriving Inhabited

inductive Direction where
  | P_to_V  
  | V_to_P 
deriving DecidableEq, Inhabited, Repr

noncomputable def iteratedQuotientMap (i : Fin ℓ) (k : ℕ)
    (h_bound : i.val + k ≤ ℓ) (x : (sDomain 𝔽q β
    h_ℓ_add_R_rate) ⟨i, by omega⟩) :
    (sDomain 𝔽q β h_ℓ_add_R_rate) ⟨i.val + k, by omega⟩ :=

noncomputable def intermediateNormVpoly
    
    (i: Fin (ℓ+1)) (k : Fin (ℓ - i + 1)) : L[X] :=
  
  Fin.foldl (n:=k) (fun acc j =>
    (qMap 𝔽q β ⟨(i : ℕ) + (j : ℕ), by admit /- proof elided -/
    ⟩).comp acc) (X)

noncomputable def qMap (i : Fin r) : L[X] :=
  let constMultiplier := ((W 𝔽q β i).eval (β i))^(Fintype.card 𝔽q)
    / ((W 𝔽q β (i + 1)).eval (β (i + 1)))
  C constMultiplier * ∏ c: 𝔽q, (X - C (algebraMap 𝔽q L c))

noncomputable def qCompositionChain (i : Fin r) : L[X] :=
  match i with
  | ⟨0, _⟩ => X
  | ⟨k + 1, h_k_add_1⟩ => (qMap 𝔽q β ⟨k, by admit /- proof elided -/
  ⟩).comp (qCompositionChain ⟨k, by admit /- proof elided -/
  ⟩)

@[elab_as_elim] def Fin.succRecOnSameFinType {motive : Fin r → Sort _}
    (zero : motive (0 : Fin r))
    (succ : ∀ i : Fin r, i + 1 < r → motive i → motive (i + 1)) : ∀ (i : Fin r), motive i
  | ⟨0, _⟩ => by admit /- proof elided -/
  | ⟨Nat.succ i_val, h⟩ => by admit /- proof elided -/

def eval₂ [Semiring S] (f : R →+* S) (x : S) (p : UniPoly R) : S :=
  p.zipIdx.foldl (fun acc ⟨a, i⟩ => acc + f a * x ^ i) 0

def inputRelation : Set (((StmtIn R) × (∀ i, OStmtIn R deg i)) × Unit) :=
  { ⟨⟨target, oStmt⟩, _⟩ | ∑ x ∈ (univ.map D), (oStmt ()).1.eval x = target }

Polynomial.mapAlgEquiv in Mathlib.Algebra.Polynomial.AlgebraMap

BitVec.toNat in Init.Prelude

def LeafData.leftSubtree {α : Type} {s_left s_right : Skeleton}
    (tree : LeafData α (Skeleton.internal s_left s_right)) :
    LeafData α s_left :=
  match tree with
  | LeafData.internal left _right =>
    left

Algebra.TensorProduct.instAlgebra in Mathlib.RingTheory.TensorProduct.Basic

def deriveTranscriptDSFSAux {ι : Type} {oSpec : OracleSpec ι} {StmtIn : Type}
    (sponge : CanonicalDuplexSponge U)
    (messages : pSpec.Messages) (i : Fin (n + 1)) :
      OracleComp (oSpec ++ₒ duplexSpongeChallengeOracle StmtIn U)
        (CanonicalDuplexSponge U × pSpec.Transcript i) :=
  Fin.induction
    (pure (sponge, fun i => i.elim0))
    (fun i ih => do
      let ⟨curSponge, prevTranscript⟩ ← ih
      match hDir : pSpec.dir i with
      | .V_to_P =>
        let ⟨challenge, newSponge⟩ ← liftM (curSponge.squeeze (challengeSize ⟨i, hDir⟩))
        let deserializedChallenge : pSpec.Challenge ⟨i, hDir⟩ :=
          Deserialize.deserialize challenge
        return (newSponge, prevTranscript.concat deserializedChallenge)
      | .P_to_V =>
        let serializedMessage : Vector U (messageSize ⟨i, hDir⟩) :=
          Serialize.serialize (messages ⟨i, hDir⟩)
        let newSponge ← liftM (DuplexSponge.absorb curSponge serializedMessage.toList)
        return (newSponge, prevTranscript.concat (messages ⟨i, hDir⟩)))
    i

Fin.removeNth in Mathlib.Data.Fin.Tuple.Basic

instance : ∀ i, SelectableType ((pSpecNonLastBlocks 𝔽q β (ϑ:=ϑ)
  (h_ℓ_add_R_rate := h_ℓ_add_R_rate)).Challenge i) := instSelectableTypeChallengeSeqCompose

BitVec.xor in Init.Data.BitVec.Basic

instance : HListRepr (HList []) where
  repr := fun _ => ""

def sumcheckFoldKnowledgeError := fun j : (pSpecSumcheckFold 𝔽q β (ϑ:=ϑ)
    (h_ℓ_add_R_rate := h_ℓ_add_R_rate)).ChallengeIdx =>
    if hj: (j.val % NBlockMessages (ϑ:=ϑ)) % 2 = 1 then
      foldKnowledgeError 𝔽q β (ϑ:=ϑ) (h_ℓ_add_R_rate := h_ℓ_add_R_rate)
        ⟨j / NBlockMessages (ϑ:=ϑ) * ϑ + ((j % NBlockMessages (ϑ:=ϑ)) / 2 + 1), by admit /- proof elided -/
        ⟩ ⟨1, rfl⟩
    else 0

@[simp]
def 𝕏 (k : ℕ) : BTField (k+1) := Z (k+1)

protected def OracleReduction.id :
    OracleReduction oSpec Statement OStatement Witness Statement OStatement Witness !p[] :=
  ⟨OracleProver.id, OracleVerifier.id⟩

@[reducible, inline, specialize]
def UniPoly (R : Type*) := Array R

class ProverLast (pSpec : ProtocolSpec n) [inst : NeZero n] where
  prover_last' : pSpec.dir ⟨n - 1, by admit /- proof elided -/
  ⟩ = .P_to_V

abbrev BaseField := ZMod baseFieldSize

def collisionFwdBwd : Prop :=
  let ⟨baseTrace, _⟩ := removeRedundantEntryDS trace
  ∃ stateIn stateOut stateOut',
    (stateIn, stateOut) ∈ baseTrace.getQ (.inr .Fwd) ∧
    (stateOut', stateIn) ∈ baseTrace.getQ (.inr .Bwd) ∧
    stateOut ≠ stateOut'

@[reducible, inline, specialize]
def challengeOracleInterfaceSR (StmtIn : Type) (pSpec : ProtocolSpec n) :
    ∀ i, OracleInterface (pSpec.Challenge i) := fun i =>
  { Query := StmtIn × pSpec.MessagesUpTo i.1.castSucc
    Response := pSpec.Challenge i
    answer := fun c _ => c }

def degCor
  (φ : ι ↪ F) (dstar degree : ℕ) (r : F) (f : ι → F) (x : ι) : F :=
    f x * ∑ l ∈ range (dstar - degree + 1), ((φ x) * r) ^ l

instance polyMonic (n : ℕ) : Monic (poly n) := definingPoly_is_monic (Z n)

@[reducible]
def pSpec : ProtocolSpec 1 := ⟨!v[.P_to_V], !v[OStatement default]⟩

noncomputable def toMLE (A : Matrix (Fin (2 ^ m)) (Fin (2 ^ n)) R) : R[X Fin n][X Fin m] :=
  MLE' (MLE' ∘ A)

def instTestLensKnowledgeSound : testLensE.IsKnowledgeSound
      outerRelIn_Test innerRelIn_Test outerRelOut_Test innerRelOut_Test
      (fun ⟨p, q, _⟩ ⟨f, _⟩ => p * q = f) (fun _ _ => True) where
  proj_knowledgeSound := fun ⟨p, q, t⟩ ⟨f, t', r⟩ _ h h' => by admit /- proof elided -/

PMF in Mathlib.Probability.ProbabilityMassFunction.Basic

def sub_descending (p q : UniPoly R) : QuotientUniPoly R :=
  Quotient.mk _ (sub p q)

verify := fun stmt _ => relComp stmt

ratchetUnchecked : α → α

@[inline, specialize]
def prover : Prover oSpec Statement Witness (Statement × Witness) Unit (pSpec Witness) where
  PrvState
  | 0 => Statement × Witness
  | 1 => Statement × Witness
  input := id
  sendMessage | ⟨0, _⟩ => fun ⟨stmt, wit⟩ => pure (wit, ⟨stmt, wit⟩)
  receiveChallenge | ⟨0, h⟩ => nomatch h
  output := fun ⟨stmt, wit⟩ => pure (⟨stmt, wit⟩, ())

abbrev singleEqPolynomial (r : R) (x : MvPolynomial σ R) : MvPolynomial σ R :=
  (1 - C r) * (1 - x) + C r * x

@[inline, specialize]
def Prover.processRoundDSFS [∀ i, VCVCompatible (pSpec.Challenge i)] (j : Fin n)
    (prover : Prover oSpec StmtIn WitIn StmtOut WitOut pSpec)
    (currentResult : OracleComp (oSpec ++ₒ duplexSpongeChallengeOracle StmtIn U)
      (pSpec.MessagesUpTo j.castSucc ×
        CanonicalDuplexSponge U × prover.PrvState j.castSucc)) :
      OracleComp (oSpec ++ₒ duplexSpongeChallengeOracle StmtIn U)
        (pSpec.MessagesUpTo j.succ ×
          CanonicalDuplexSponge U × prover.PrvState j.succ) := do
  let ⟨messages, sponge, state⟩ ← currentResult
  match hDir : pSpec.dir j with
  | .V_to_P => do
    let f ← prover.receiveChallenge ⟨j, hDir⟩ state
    let (challenge, newSponge) ←
      liftM (DuplexSponge.squeeze sponge (challengeSize ⟨j, hDir⟩))
    
    let deserializedChallenge : pSpec.Challenge ⟨j, hDir⟩ := Deserialize.deserialize challenge
    return ⟨messages.extend hDir, newSponge, f deserializedChallenge⟩
  | .P_to_V => do
    let ⟨msg, newState⟩ ← prover.sendMessage ⟨j, hDir⟩ state
    let serializedMessage : Vector U (messageSize ⟨j, hDir⟩) := Serialize.serialize msg
    let newSponge ← liftM (DuplexSponge.absorb sponge serializedMessage.toList)
    return ⟨messages.concat hDir msg, newSponge, newState⟩

@[reducible, inline, specialize]
def Challenges (pSpec : ProtocolSpec n) : Type := ∀ i, pSpec.Challenge i

def AlgebraTowerEquiv.toAlgebraOverRight (e : AlgebraTowerEquiv A B) (i j : ι)
    (h : i ≤ j) : Algebra (B i) (A j) :=

@[reducible, inline]
instance instPolynomialDegreeLT : OracleInterface (R⦃< d⦄[X]) where
  Query := R
  Response := R
  answer := fun ⟨poly, _⟩ point => poly.eval point

noncomputable def queryVerifier (k_le_n : (∑ j', (s j').1) ≤ n) (l : ℕ) [DecidableEq F] :
  OracleVerifier []ₒ
    (FinalStatement F k) (FinalOracleStatement D x s)
    (FinalStatement F k) (FinalOracleStatement D x s)
    (pSpec D x l) where
  verify := fun prevChallenges roundChallenge => do
    let (p : F[X]) ← getConst D x k s
    for m in (List.finRange l) do
      let s₀ := roundChallenge ⟨1, by admit /- proof elided -/
      ⟩ m
      discard <|
        (List.finRange (k + 1)).mapM
              (fun i =>
                do
                  let x₀ := prevChallenges i
                  let s₀ :
                    evalDomain D x
                      (∑ j' ∈ finRangeTo i.1, (s j').1) :=
                    ⟨_, pow_2_pow_i_mem_Di_of_mem_D _ s₀.2⟩
                  let queries :
                    List (
                      evalDomain D x
                        (∑ j' ∈ finRangeTo i.1, (s j').1)
                    ) :=
                    List.map
                      (fun r =>
                        ⟨
                          _,
                          CosetDomain.mul_root_of_unity D (roots_of_unity_lem k_le_n) s₀.2 r.2
                        ⟩
                      )
                      (Domain.rootsOfUnity D n (s i))
                  let (pts : List (F × F)) ←
                    List.mapM
                      (fun q => queryCodeword D x k s q >>= fun v => pure (q.1.1, v))
                      queries
                  let β ←
                    if h : i.1 < k
                    then
                      have := CosetDomain.pow_lift D x (s i).1 s₀.2
                      queryCodeword D x k s (i := ⟨i.1.succ, Order.lt_add_one_iff.mpr h⟩)
                        ⟨_, by admit /- proof elided -/
                        ⟩
                    else
                      pure (p.eval (s₀.1.1 ^ (2 ^ (s (Fin.last k)).1)))
                  guard (RoundConsistency.roundConsistencyCheck x₀ pts β)
              )
    pure prevChallenges
  embed :=
    ⟨
      fun j => Sum.inl j,
      by admit /- proof elided -/
    ⟩
  hEq := by admit /- proof elided -/

Algebra.TensorProduct.leftAlgebra in Mathlib.RingTheory.TensorProduct.Basic

@[simp]
abbrev Statement.AfterFirstSumcheck : Type :=
  FirstSumcheckChallenge R pp × Statement.AfterFirstChallenge R pp

let fiberwise_disagreements := fiberwiseDisagreementSet 𝔽q β i steps h_i_add_steps
      f_i f_bar_i
    let folded_disagreements := disagreementSet 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i steps
      h_i_add_steps folded_f_i folded_f_bar_i
    
    ¬ (fiberwise_disagreements ⊆ folded_disagreements)
  else
    
    
    
    let folded_f_i := iterated_fold 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate)
      (steps := ⟨steps, by admit /- proof elided -/
      ⟩) (i := ⟨i, by admit /- proof elided -/
      ⟩)
      (h_i_add_steps := by admit /- proof elided -/
      ) f_i challenges
    let dist_to_code := distFromCode folded_f_i
      (BBF_Code 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) ⟨i + steps, by admit /- proof elided -/
      ⟩)
    2 * dist_to_code < (d_i_plus_steps : ℕ∞)

@[reducible, simp] def OStmtOut := fun _ : Fin 2 => OStatement

let ⟨s, d⟩ := factorOutTwos (n - 1)
  for a in millerRabinBases do
    if a % n == 0 then
      continue

def minDist [DecidableEq F] (IC : MatrixSubmodule κ ι F) : ℕ :=
  sInf { d : ℕ | ∃ U ∈ IC, ∃ V ∈ IC, distCodewords U V = d }

noncomputable def fold_k_set
  {S : Finset ι} {φ : ι ↪ F} {k m : ℕ}
  [∀ j : ℕ, Neg (indexPowT S φ j)]
  (set : Set ((indexPowT S φ 0) → F)) (αs : Fin k → F) (hk : k ≤ m): Set (indexPowT S φ k → F) :=
    { g | ∃ f ∈ set, g = fold_k f αs hk}

@[reducible]
def spec : OracleSpec Unit := fun _ => (α × α, α)

def ConstraintSystem (𝓡 : Type) (numWires numGates : ℕ) := Fin numGates → Gate 𝓡 numWires

def mul_by_2 (s : Finset ℕ) : Finset ℕ :=
  s.map ⟨fun n => 2 * n, by admit /- proof elided -/
  ⟩

input := fun ⟨⟨_, oStmt⟩, _⟩ => oStmt default

map_pure in ToMathlib.Control.Monad.Hom

instance [ProverFirst pSpec] : ProverLast pSpec where
  prover_last' := by admit /- proof elided -/

instance instDecidableEqOption {α : Type*} [DecidableEq α] :
    DecidableEq (Option α) := inferInstance

instance {bIdx : Fin (ℓ / ϑ - 1)} : ∀ j, OracleInterface ((pSpecFullNonLastBlock 𝔽q β
  (h_ℓ_add_R_rate := h_ℓ_add_R_rate) bIdx).Message j) :=
  instOracleInterfaceMessageAppend

def seqComposeChallengeIdxToSigma {m : ℕ} {n : Fin m → ℕ} {pSpec : ∀ i, ProtocolSpec (n i)}
    (k : (seqCompose pSpec).ChallengeIdx) : (i : Fin m) × (pSpec i).ChallengeIdx :=
  let ij := Fin.splitSum k.1
  ⟨ij.1, ⟨ij.2, by admit /- proof elided -/
    ⟩⟩

def hammingClose (i : Fin (ℓ + 1)) (f : OracleFunction 𝔽q β
    (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i) : Prop :=
  2 * Code.distFromCode (u := f)
    (C := BBF_Code 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i) <
    (BBF_CodeDistance ℓ 𝓡 i : ℕ∞)

class ProverFirst (pSpec : ProtocolSpec n) [NeZero n] where
  prover_first' : pSpec.dir 0 = .P_to_V

Nat.Prime in Mathlib.Data.Nat.Prime.Defs

Polynomial.resultant in Mathlib.RingTheory.Polynomial.Resultant.Basic

@[reducible]
def foldCommitOracleVerifier (i : Fin ℓ) (hCR : isCommitmentRound ℓ ϑ i) :
  OracleVerifier []ₒ
    (StmtIn := Statement (L := L) Context i.castSucc)
    (OStmtIn := OracleStatement 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) ϑ i.castSucc)
    (StmtOut := Statement (L := L) Context i.succ)
    (OStmtOut := OracleStatement 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) ϑ i.succ)
    (pSpec := pSpecFoldCommit 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i) :=
    OracleVerifier.append (oSpec:=[]ₒ)
      (pSpec₁ := pSpecFold (L:=L))
      (pSpec₂ := pSpecCommit 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i)
      (V₁ := foldOracleVerifier 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i)
      (V₂ := commitOracleVerifier 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i hCR)

Nat.digits in Mathlib.Data.Nat.Digits.Defs

def domainComplement (φ : ι ↪ F) : Finset F :=
  Finset.univ \ Finset.image φ.toFun Finset.univ

noncomputable def fixFirstVariablesOfMQP (v : Fin (ℓ + 1))
  (H : MvPolynomial (Fin ℓ) L) (challenges : Fin v → L) : MvPolynomial (Fin (ℓ - v)) L :=
  have h_l_eq : ℓ = (ℓ - v) + v := by rw [Nat.add_comm]; exact (Nat.add_sub_of_le v.is_le).symm
  -- Step 1 : Rename L[X Fin ℓ] to L[X (Fin (ℓ - v) ⊕ Fin v)]
  let finEquiv := finSumFinEquiv (m := ℓ - v) (n := v).symm
  let H_sum : L[X (Fin (ℓ - v) ⊕ Fin v)] :=

inductive Skeleton :
    (n : ℕ) → (ar : Fin n → ℕ) → Type where
  | leaf {ar0 : Fin 0 → ℕ} : Skeleton 0 ar0
  | node {n : ℕ} {ar : Fin (n+1) → ℕ}
      (children : Fin (ar 0) →
        Skeleton n (fun i => ar i.succ)) :
      Skeleton (n+1) ar

instance : Add (Cayley T) where
  add := add

instance {i : Fin (k + 1)} : ∀ j, OracleInterface (OracleStatement D x s i j) :=
  fun _ => inferInstance

def getFirstOracle {i : Fin (ℓ + 1)}
    (oStmt : (∀ j, OracleStatement 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) ϑ i j)) :
    sDomain 𝔽q β h_ℓ_add_R_rate 0 → L :=

instance : MonadLift (StateT τ m) (StateT (σ × τ) m) where
  monadLift := fun x st => do let y ← x st.2; return (y.1, st.1, y.2)

instance instOneConcreteBTField (k : ℕ) : One (ConcreteBTField k) where
  one := one

def Function.extendDomain {α β : Type*} [DecidableEq α] [Zero β] {s : Finset α}
    (f : (x : α) → (x ∈ s) → β) : α → β :=
  fun x ↦ if hx : x ∈ s then f x hx else 0

noncomputable def relayOracleReduction (i : Fin ℓ) (hNCR : ¬ isCommitmentRound ℓ ϑ i) :
  OracleReduction (oSpec := []ₒ)
    (StmtIn := Statement (L := L) Context i.succ)
    (OStmtIn := OracleStatement 𝔽q β (ϑ := ϑ)
      (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i.castSucc)
    (WitIn := Witness (L := L) 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i.succ)
    (StmtOut := Statement (L := L) Context i.succ)
    (OStmtOut := OracleStatement 𝔽q β (ϑ := ϑ)
      (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i.succ)
    (WitOut := Witness (L := L) 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i.succ)
    (pSpec := pSpecRelay) where
  prover := relayOracleProver 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i hNCR
  verifier := relayOracleVerifier 𝔽q β (h_ℓ_add_R_rate := h_ℓ_add_R_rate) i hNCR

def last_nonzero_prop {p : UniPoly R} (k : Fin p.size) : Prop :=
  p[k] ≠ 0 ∧ (∀ j, (hj : j < p.size) → j > k → p[j] = 0)

def IsBerlekampWelchSolution
  (e k : ℕ)
  (ωs f : Fin n → F)
  (v : Fin (2 * e + k) → F)
  : Prop
  := Matrix.mulVec (BerlekampWelchMatrix e k ωs f) v = Rhs e ωs f

def intCast_negSucc {k : ℕ} (n : ℕ) : intCast (k:=k) (Int.negSucc n)
  = - (↑(n + 1) : ConcreteBTField k) :=

embed := naVerifier.embed

Set.image in Mathlib.Data.Set.Defs

Equiv.sumComm in Mathlib.Logic.Equiv.Sum

toFunA := fun ⟨⟨target, challenges⟩, oStmt⟩ =>
    ⟨target, fun _ =>
      match h : n with
      | 0 => ⟨Polynomial.C <| MvPolynomial.isEmptyAlgEquiv R (Fin 0) (oStmt ()), by admit /- proof elided -/
        ⟩
      | n + 1 =>
      ⟨∑ x ∈ (univ.map D) ^ᶠ (n - i), (oStmt ()).val ⸨X ⦃i⦄, challenges, x⸩'(by admit /- proof elided -/
      ),
        sumcheck_roundPoly_degreeLE R n deg D i (oStmt ()).property⟩⟩

instance : ∀ i, SelectableType ((pSpecCoreInteraction 𝔽q β (ϑ:=ϑ)
  (h_ℓ_add_R_rate := h_ℓ_add_R_rate)).Challenge i) := instSelectableTypeChallengeAppend

@[reducible]
def Witness := Fin sz.n_w → R

def dfoldl' (n : ℕ) (α : Fin (n + 1) → Type u)
    (f : (i : Fin n) → α i.castSucc → α i.succ) (init : α 0) : α (last n) :=
  dfoldlM' (m := Id) n α f init

inductive FullData (α : Type) : Skeleton → Type
  | leaf (value : α) : FullData α Skeleton.leaf
  | internal {left right} (value : α)
      (leftData : FullData α left)
      (rightData : FullData α right) :
      FullData α (Skeleton.internal left right)
  deriving Repr

instance extractorLens_rbr_knowledge_soundness :
    Extractor.Lens.IsKnowledgeSound
      (relationRound R n deg D i.castSucc) (Simple.inputRelation R deg D)
      (relationRound R n deg D i.succ) (Simple.outputRelation R deg)
      ((Simple.oracleVerifier R deg D oSpec).toVerifier.compatStatement (oStmtLens R n deg D i))
      (fun _ _ => True)
      ⟨oStmtLens R n deg D i, Witness.InvLens.trivial⟩ where
  proj_knowledgeSound := by admit /- proof elided -/

@[inline] def add (a b : AssocNat) : AssocNat :=
  ⟨a ∘ b, by admit /- proof elided -/
  ⟩

@[inline]
def neg [Neg R] (p : MlPolyEval R n) : MlPolyEval R n := p.map (fun a => -a)

instance [ProverFirst pSpec] : Unique (pSpec.MessageIdx) where
  default := ⟨0, by admit /- proof elided -/
  ⟩
  uniq := fun ⟨i, _⟩ => by admit /- proof elided -/

instance instAlgebraTowerConcreteBTF : AlgebraTower (ConcreteBTField) where
  algebraMap := concreteTowerAlgebraMap
  commutes' := by admit /- proof elided -/

Units.mulAction' in Mathlib.Algebra.Group.Action.Units

def FullData.rightSubtree {α : Type} {s_left s_right : Skeleton}
    (tree : FullData α (Skeleton.internal s_left s_right)) :
    FullData α s_right :=
  match tree with
  | FullData.internal _ _left right =>
    right

def finSuccEquivNth' (i : Fin n) : Fin n ≃ Option (Fin (n - 1)) :=

noncomputable instance {v : ι → F} {s : AffineSubspace F (ι → F)} [inst : Nonempty s] :
    Nonempty (v +ᵥ s) :=

def Cache.cons (n : ℕ) (leaves : List.Vector α (2 ^ (n + 1))) (cache : Cache α n) :
    Cache α (n + 1) :=
  Fin.snoc cache leaves

Unit in Init.Prelude
</all_available_defs>

<all_available_lemmas>
Fin.eta in Init.Data.Fin.Lemmas
add_zero in Mathlib.Algebra.Group.Defs
Module.Basis.repr_linearCombination in Mathlib.LinearAlgebra.Basis.Defs
Module.Basis.repr_symm_apply in Mathlib.LinearAlgebra.Basis.Defs
Nat.add_zero in Init.Core
cast_eq in Init.Core
eq_mp_eq_cast in Init.PropLemmas
not_lt_zero' in Mathlib.Algebra.Order.GroupWithZero.Canonical
tsub_zero in Mathlib.Algebra.Order.Sub.Defs
nonpos_iff_eq_zero in Mathlib.Algebra.Order.Monoid.Canonical.Defs
not_lt in Mathlib.Order.Defs.LinearOrder
Polynomial.ext in Mathlib.Algebra.Polynomial.Basic
add_lt_iff_neg_right in Mathlib.Algebra.Order.Monoid.Unbundled.Basic
add_tsub_cancel_right in Mathlib.Algebra.Order.Sub.Defs
Decidable.not_not in Init.PropLemmas
Nat.le_of_not_lt in Init.Data.Nat.Basic
Nat.sub_lt_sub_right in Init.Data.Nat.Basic
Nat.sub_sub in Init.Data.Nat.Basic
dite_eq_right_iff in Init.PropLemmas
false_or in Init.SimpLemmas
forall_const in Init.PropLemmas
imp_false in Init.Core
ite_eq_left_iff in Init.PropLemmas
one_ne_zero in Mathlib.Algebra.NeZero

lemma Xⱼ_zero_eq_one (ℓ : ℕ) (h_ℓ : ℓ ≤ r) :
  Xⱼ 𝔽q β ℓ h_ℓ ⟨0, by exact Nat.two_pow_pos ℓ⟩ = 1

@[simp]
lemma lt_add_of_pos_right_of_le (a b c : ℕ) [NeZero c] (h : a ≤ b) : a < b + c

omit [DecidableEq 𝔽q] hF₂ in
lemma getSDomainBasisCoeff_of_iteratedQuotientMap
    [NeZero R_rate] (i : Fin ℓ) (k : ℕ)
    (h_bound : i.val + k ≤ ℓ) (x : (sDomain 𝔽q β
    h_ℓ_add_R_rate) ⟨i, by omega⟩) :
    let y

theorem base_intermediateNormVpoly
  (k : Fin (ℓ + 1)) :
  intermediateNormVpoly 𝔽q β h_ℓ_add_R_rate ⟨0, by
    by_contra ht
    simp only [not_lt, nonpos_iff_eq_zero] at ht
    contradiction
  ⟩ ⟨k, by simp only [tsub_zero]; omega⟩ =
  normalizedW 𝔽q β ⟨k, by omega⟩

lemma normalizedW_eq_qMap_composition (ℓ R_rate : ℕ) (i : Fin r) :
    normalizedW 𝔽q β i = qCompositionChain 𝔽q β (ℓ:=ℓ) (R_rate:=R_rate) i

lemma qMap_comp_normalizedW (i : Fin r) (h_i_add_1 : i + 1 < r) :
  (qMap 𝔽q β i).comp (normalizedW 𝔽q β i) = normalizedW 𝔽q β (i + 1)

lemma qCompositionChain_eq_foldl (i : Fin r) :
  qCompositionChain 𝔽q β (ℓ:=ℓ) (R_rate:=R_rate) i =
  Fin.foldl (n:=i) (fun acc j =>
    (qMap 𝔽q β ⟨j, by omega⟩).comp acc) (X)

omit [DecidableEq 𝔽q] hF₂ h_β₀_eq_1 in
lemma getSDomainBasisCoeff_of_sum_repr [NeZero R_rate] (i : Fin (ℓ + 1))
    (x : (sDomain 𝔽q β h_ℓ_add_R_rate) ⟨i, by omega⟩)
    (x_coeffs : Fin (ℓ + R_rate - i) → 𝔽q)
    (hx : x = ∑ j_x, (x_coeffs j_x) • (sDomain_basis 𝔽q β
      h_ℓ_add_R_rate (i := ⟨i, by omega⟩) (h_i := by
        simp only; apply Nat.lt_add_of_pos_right_of_le; omega) j_x).val) :
    ∀ (j: Fin (ℓ + R_rate - i)), ((sDomain_basis 𝔽q β
      h_ℓ_add_R_rate (i := ⟨i, by omega⟩) (h_i := by
        simp only; apply Nat.lt_add_of_pos_right_of_le; omega)).repr x) j = x_coeffs j

omit [DecidableEq 𝔽q] hF₂ h_β₀_eq_1 in
lemma get_sDomain_basis (i : Fin r) (h_i : i < ℓ + R_rate) :
    ∀ (k : Fin (ℓ + R_rate - i)),
    (sDomain_basis 𝔽q β h_ℓ_add_R_rate
      i (by omega)) k = eval (β ⟨i + k.val, by omega⟩) (normalizedW 𝔽q β i)

omit [DecidableEq L] [DecidableEq 𝔽q] h_Fq_char_prime hF₂ hβ_lin_indep h_β₀_eq_1 in
theorem intermediateNormVpoly_comp (i : Fin ℓ) (k : Fin (ℓ - i + 1))
  (l : Fin (ℓ - (i.val + k.val) + 1)) :
  intermediateNormVpoly 𝔽q β h_ℓ_add_R_rate (i := ⟨i, by omega⟩) (k:=⟨k + l, by
      simp only; omega⟩) =
    (intermediateNormVpoly 𝔽q β h_ℓ_add_R_rate (i := ⟨i+k, by omega⟩) (k:=⟨l, by
      simp only; omega⟩)).comp (
  intermediateNormVpoly 𝔽q β h_ℓ_add_R_rate (i := ⟨i, by omega⟩) (k:=⟨k, by
      simp only; omega⟩)
  )

omit [DecidableEq L] [DecidableEq 𝔽q] hF₂ hβ_lin_indep h_β₀_eq_1 in
lemma intermediateNormVpoly_eval_is_linear_map (i : Fin (ℓ + 1)) (k : Fin (ℓ - i + 1)) :
  IsLinearMap 𝔽q (fun x : L =>
    (intermediateNormVpoly 𝔽q β h_ℓ_add_R_rate i k).eval x)

theorem qMap_is_linear_map (i : Fin r) :
  IsLinearMap 𝔽q (f:=fun inner_p ↦ (qMap 𝔽q β i).comp inner_p)

omit h_Fq_char_prime in
lemma 𝔽q_element_eq_zero_or_eq_one : ∀ c: 𝔽q, c = 0 ∨ c = 1

lemma getBit_of_binaryFinMapToNat {n : ℕ} (m : Fin n → ℕ) (h_binary: ∀ j: Fin n, m j ≤ 1) :
    ∀ k: ℕ, Nat.getBit k (binaryFinMapToNat m h_binary).val
      = if h_k: k < n then m ⟨k, by omega⟩ else 0

lemma and_two_pow_eq_zero_of_getBit_0 {n i : ℕ} (h_getBit : getBit i n = 0)
    : n &&& (2 ^ i) = 0

lemma and_eq_zero_iff_and_each_getBit_eq_zero {n m : ℕ} :
    n &&& m = 0 ↔ ∀ k, Nat.getBit k n &&& Nat.getBit k m = 0

lemma eq_iff_eq_all_getBits {n m : ℕ} : n = m ↔ ∀ k, getBit k n = getBit k m

lemma shiftRight_and_one_distrib {n m k : ℕ} :
    Nat.getBit k (n &&& m) = Nat.getBit k n &&& Nat.getBit k m

lemma getBit_two_pow {i k : ℕ} : (getBit k (2^i) = if i == k then 1 else 0)

lemma getBit_of_lt_two_pow {n: ℕ} (a: Fin (2^n)) (k: ℕ) :
  getBit k a = if k < n then getBit k a else 0

lemma getBit_eq_testBit (k n : Nat) : getBit k n = if n.testBit k then 1 else 0

lemma getBit_lt_2 {k n : Nat} : getBit k n < 2

lemma getBit_of_xor {n m k: ℕ} : getBit k (n ^^^ m) = getBit k n ^^^ getBit k m

lemma getBit_zero_eq_zero {k : Nat} : getBit k 0 = 0

lemma sum_of_and_eq_zero_is_xor {n m : ℕ} (h_n_AND_m : n &&& m = 0) : n + m = n ^^^ m

lemma sum_eq_xor_plus_twice_and (n : Nat) : ∀ m : ℕ, n + m = (n ^^^ m) + 2 * (n &&& m)

lemma and_by_split_lowBits {n m n1 m1 bn bm : ℕ} (h_bn : bn < 2) (h_bm : bm < 2)
  (h_n : n = n1 * 2 + bn) (h_m : m = m1 * 2 + bm):
  n &&& m = (n1 &&& m1) * 2 + (bn &&& bm)

lemma div_2_form {nD2 b : ℕ} (h_b : b < 2):
  (nD2 * 2 + b) / 2 = nD2

lemma or_by_split_lowBits {n m n1 m1 bn bm : ℕ} (h_bn : bn < 2) (h_bm : bm < 2)
  (h_n : n = n1 * 2 + bn) (h_m : m = m1 * 2 + bm):
  n ||

lemma xor_by_split_lowBits {n m n1 m1 bn bm : ℕ} (h_bn : bn < 2) (h_bm : bm < 2)
  (h_n : n = n1 * 2 + bn) (h_m : m = m1 * 2 + bm):
  n ^^^ m = (n1 ^^^ m1) * 2 + (bn ^^^ bm)

@[simp]
lemma invFun_toFun (f : F) : inst.equiv.invFun (inst.equiv.toFun f) = f

theorem last_nonzero_last_iff [LawfulBEq R] {p : UniPoly R} (hp : p.size > 0) :
  p.last_nonzero = some ⟨ p.size - 1, Nat.pred_lt_self hp ⟩ ↔ p.getLast hp ≠ 0

lemma qMap_total_fiber_one_level_eq (i : Fin ℓ) (h_i_add_1 : i.val + 1 ≤ ℓ)
    (y : sDomain 𝔽q β h_ℓ_add_R_rate (i := ⟨i + 1, by omega⟩)) (k : Fin 2) :
    let basis_x := sDomain_basis 𝔽q β h_ℓ_add_R_rate ⟨i, by omega⟩ (by simp only; omega)
    let x : sDomain 𝔽q β h_ℓ_add_R_rate ⟨i, by omega⟩ := qMap_total_fiber 𝔽q β (i := ⟨i, by omega⟩)
      (steps := 1) (h_i_add_steps := by apply Nat.lt_add_of_pos_right_of_le; omega) (y := y) k
    let y_lifted : sDomain 𝔽q β h_ℓ_add_R_rate ⟨i, by omega⟩ := sDomain.lift 𝔽q β h_ℓ_add_R_rate
      (i := ⟨i, by omega⟩) (j := ⟨i.val + 1, by omega⟩)
      (h_j := by apply Nat.lt_add_of_pos_right_of_le; omega)
      (h_le := by apply Fin.mk_le_mk.mpr (by omega)) y
    let free_coeff_term : sDomain 𝔽q β h_ℓ_add_R_rate ⟨i, by omega⟩ :=
      (Fin2ToF2 𝔽q k) • (basis_x ⟨0, by simp only; omega⟩)
    x = free_coeff_term + y_lifted

@[simp]
lemma bIdx_mul_ϑ_add_i_fin_ℓ_pred_lt_ℓ (bIdx : Fin (ℓ / ϑ - 1)) (i : Fin (ϑ - 1))
    : ↑bIdx * ϑ + ↑i < ℓ

lemma neg_add_cancel {k : ℕ} (a : ConcreteBTField k) : neg a + a = 0

theorem nsmul_zero [LawfulBEq R] (p : UniPoly R) : nsmul 0 p = 0

theorem foldl_succ
 {α β} {n : ℕ} [NeZero n] (f : β → α → β) (init : β) (v : Vector α n) :
  v.foldl (f:=f) (b:=init) = v.tail.foldl (f:=f) (b:=f init v.head)

theorem BitVec.eq_mp_eq_dcast {w w2 : ℕ} (x : BitVec w) (h_width_eq : w = w2)
  (h_bitvec_eq : BitVec w = BitVec w2 := by rw [h_width_eq]) :
  Eq.mp (h:=h_bitvec_eq) (a:=x) = dcast (h_width_eq) (x)

omit [NeZero ϑ] hdiv in
lemma toOutCodewordsCountOf0 : toOutCodewordsCount ℓ ϑ 0 = 1

@[simp]
theorem fflatten_zero {A : Sort u} {F : A → Sort v} {n : Fin 0 → ℕ}
    {α : (i : Fin 0) → (j : Fin (n i)) → A}
    {v : (i : Fin 0) → (j : Fin (n i)) → F (α i j)} : fflatten v = !h[]

@[simp]
lemma coe_toFun_of_coe_apply (f : ∀ a, β a) (a : α) : (f : F) a = f a

theorem join_eq_join_iff {k : ℕ} (h_pos : k > 0) (hi₀ lo₀ hi₁ lo₁ : ConcreteBTField (k - 1)) :
  《 hi₀, lo₀ 》 = 《 hi₁, lo₁ 》 ↔ (hi₀ = hi₁ ∧ lo₀ = lo₁)

lemma division_by_conjugate {a b : ℝ} (hpos : 0 ≤ b) (hnonzero : a + b.sqrt ≠ 0) :
  a - (b).sqrt = (a^2 - b)/(a + b.sqrt)

theorem append_rbrSoundness {lang₁ : Set Stmt₁} {lang₂ : Set Stmt₂} {lang₃ : Set Stmt₃}
    (V₁ : Verifier oSpec Stmt₁ Stmt₂ pSpec₁)
    (V₂ : Verifier oSpec Stmt₂ Stmt₃ pSpec₂)
    {rbrSoundnessError₁ : pSpec₁.ChallengeIdx → ℝ≥0}
    {rbrSoundnessError₂ : pSpec₂.ChallengeIdx → ℝ≥0}
    (h₁ : V₁.rbrSoundness init impl lang₁ lang₂ rbrSoundnessError₁)
    (h₂ : V₂.rbrSoundness init impl lang₂ lang₃ rbrSoundnessError₂) :
      (V₁.append V₂).rbrSoundness init impl lang₁ lang₃
        (Sum.elim rbrSoundnessError₁ rbrSoundnessError₂ ∘ ChallengeIdx.sumEquiv.symm)

Fin.is_le' in Init.Data.Fin.Lemmas

theorem reduction_rbr_knowledge_soundness : True

theorem hcons_injective2 {α : Sort u} {β : Fin n → Sort u} :
    Function.Injective2 (@hcons n α β)

@[simp]
lemma Fintype.zero_lt_card {ι : Type*} [Fintype ι] [Nonempty ι] : 0 < Fintype.card ι

lemma forwardRange_dropLast (n : ℕ) (r : Fin (n - 1)) (l : Fin (r.val + 1)) :
    (forwardRange n ⟨r + 1, by omega⟩ ⟨l, by simp only; omega⟩).dropLast
    = forwardRange n ⟨r, by omega⟩ ⟨l, by simp only [Fin.is_lt]⟩

theorem happend_left_eq_hcons {α : Fin 1 → Sort u} {β : Fin n → Sort u}
    (a : (i : Fin 1) → α i) (v : (i : Fin n) → β i) :
    True

lemma algebraMap_succ_eq_zero_x {k : ℕ} (h_pos : k > 0) (x : BTField (k - 1)) :
  letI instAlgebra := binaryAlgebraTower (l:=k-1) (r:=k) (h_le:=by omega)
  algebraMap (BTField (k - 1)) (BTField k) x = ⋘ 0, x ⋙

@[simp]
lemma seqCompose_zero
    (Stmt : Fin 1 → Type) (Wit : Fin 1 → Type) {n : Fin 0 → ℕ} {pSpec : ∀ i, ProtocolSpec (n i)}
    (P : (i : Fin 0) →
      Prover oSpec (Stmt i.castSucc) (Wit i.castSucc) (Stmt i.succ) (Wit i.succ) (pSpec i)) :
    seqCompose Stmt Wit P = Prover.id

Nat.le_of_succ_le in Init.Data.Nat.Basic

lemma combine_eq_cases {F ι : Type*} [Field F] [DecidableEq F]
  (φ : ι ↪ F) (dstar : ℕ) (r : F) (fs : Fin m → ι → F) (degs : Fin m → ℕ)
    (hdegs : ∀ i, degs i ≤ dstar) (φ_neq_0 : ∀ i, φ i ≠ 0) :
  combine φ dstar r fs degs =
    fun x =>
      let q := φ x * r
      if q ≠ 1
      then ∑ i, (ri dstar degs r i) * (fs i x) * (1 - q^(dstar - degs i + 1)) / (1 - q)
      else ∑ i, (ri dstar degs r i) * (fs i x) *  (dstar - degs i + 1)

@[simp]
theorem prover_first (pSpec : ProtocolSpec n) [NeZero n] [h : ProverFirst pSpec] :
    pSpec.dir 0 = .P_to_V

lemma rank_eq_colRank : U.rank = colRank U

@[grind _=_]
lemma degreeX_as_weighted_deg :
  degreeX f = natWeightedDegree f 1 0

@[simp]
lemma challengeOracleInterface_append_range_inr (j : pSpec₂.ChallengeIdx) :
    [(pSpec₁ ++ₚ pSpec₂).Challenge]ₒ.range (.inr j) = pSpec₂.Challenge j

omit h_β₀_eq_1 in
lemma finToBinaryCoeffs_sDomainToFin (i : Fin r) (h_i : i < ℓ + R_rate)
    (x : sDomain 𝔽q β h_ℓ_add_R_rate i) :
    let pointFinIdx := (sDomainToFin 𝔽q β h_ℓ_add_R_rate i h_i) x
    finToBinaryCoeffs 𝔽q (i := i) (idx :=pointFinIdx) =
    (sDomain_basis 𝔽q β
    h_ℓ_add_R_rate i h_i).repr x

theorem empty_unique (v : Fin 0 → α) : v = !v[]

@[simp, grind _=_]
lemma degreeY_mul [IsDomain F] (f g : F[X][Y]) (hf : f ≠ 0) (hg : g ≠ 0)
  : natDegreeY (f * g) = natDegreeY f + natDegreeY g

lemma h_sub_middle {k : ℕ} (h_pos : k > 0) : 2 ^ k - 1 - 2 ^ (k - 1) + 1 = 2 ^ (k - 1)

@[simp]
theorem dcast₂_eq : dcast₂ (Eq.refl a) dcast_eq c = c

@[simp]
theorem hflatten_two_eq_append {n : Fin 2 → ℕ} {α : (i : Fin 2) → (j : Fin (n i)) → Sort*}
    {v : (i : Fin 2) → (j : Fin (n i)) → α i j} : hflatten v = happend (v 0) (v 1)

omit [DecidableEq L] h_Fq_char_prime hF₂ hβ_lin_indep in
lemma Prod_W_comp_X_sub_C_ne_zero (i : Fin r) :
    (univ : Finset 𝔽q).prod (fun c => (W 𝔽q β i).comp (X - C (c • β i))) ≠ 0

theorem split_sum_eq_sum_split {k : ℕ} (h_pos : k > 0) (x₀ x₁ : ConcreteBTField k)
  (hi₀ lo₀ hi₁ lo₁ : ConcreteBTField (k - 1))
  (h_split_x₀ : split h_pos x₀ = (hi₀, lo₀))
  (h_split_x₁ : split h_pos x₁ = (hi₁, lo₁)) :
  split h_pos (x₀ + x₁) = (hi₀ + hi₁, lo₀ + lo₁)

omit Oₘ in
theorem seqCompose_perfectCompleteness (hInit : init.neverFails)
    (rel : (i : Fin (m + 1)) → Set (Stmt i × Wit i))
    (R : ∀ i, Reduction oSpec (Stmt i.castSucc) (Wit i.castSucc) (Stmt i.succ) (Wit i.succ)
      (pSpec i))
    (h : ∀ i, (R i).perfectCompleteness init impl (rel i.castSucc) (rel i.succ)) :
      (Reduction.seqCompose Stmt Wit R).perfectCompleteness
        init impl (rel 0) (rel (Fin.last m))

lemma Lemma_A_1 {H : F[X][Y]} (β : 𝒪 H) (D : ℕ) (hD : D ≥ Bivariate.totalDegree H)
    (S_β_card : Set.ncard (S_β β) > (weight_Λ_over_𝒪 β D) * H.natDegree) :
  embeddingOf𝒪Into𝕃 _ β = 0

Fin.coe_castSucc in Init.Data.Fin.Lemmas

theorem singleEqPolynomial_zeroOne_C (r : Fin 2) (x : Fin 2) :
    (singleEqPolynomial (r : R) (C x) : MvPolynomial σ R) = if x = r then 1 else 0

lemma oddPart_def :
  oddPart f =
  C (2⁻¹ : F) * (f - f.comp (-X)) /ₘ X

theorem non_zero_divisors_iff (M₀ : Type*) [Mul M₀] [Zero M₀] :
    NoZeroDivisors M₀ ↔ ∀ {a b : M₀}, a * b = 0 → a = 0 ∨ b = 0

private lemma johnson_condition_strong_implies_2_le_B_card
  (h_johnson : JohnsonConditionStrong B v)
  :
  2 ≤ B.card

@[simp] theorem rightpad_suffix (n : Nat) (unit : α) (l : List α) :
    replicate (n - l.length) unit <:+ rightpad n unit l

lemma rank_eq_rowRank : U.rank = rowRank U

theorem decoder_dist_impl_mem
  {k r D e : ℕ}
  (h_e : e ≤ n - Real.sqrt (k * n))
  {ωs : Fin n ↪ F}
  {f : Fin n → F}
  {p : F[X]}
  (h_dist : Δ₀(f, p.eval ∘ ωs) ≤ e)
  :
  p ∈ decoder k r D e ωs f

lemma cons_get_eq {α} {n : ℕ} (hd : α) (tl : Vector α n) (i : Fin (n + 1)) :
    (cons hd tl).get i =
      if hi: i.val == 0 then hd else tl.get (⟨i.val - 1, by
        simp only [beq_iff_eq, Fin.val_eq_zero_iff] at hi
        apply Nat.sub_lt_left_of_lt_add
        · by_contra hi_ne_gt_1
          simp only [not_le, Nat.lt_one_iff, Fin.val_eq_zero_iff] at hi_ne_gt_1
          contradiction
        · have hi_lt:= i.isLt; omega
      ⟩)

theorem oracleVerifier_rbrKnowledgeSoundness [Fintype R] :
    (oracleReduction R deg oSpec).verifier.rbrKnowledgeSoundness init impl
      (inputRelation R deg D) (outputRelation R deg)
        (fun _ => (deg : ℝ≥0) / (Fintype.card R))

lemma bIdx_succ_mul_ϑ_le_ℓ_succ (bIdx : Fin (ℓ / ϑ - 1)) : (↑bIdx + 1) * ϑ ≤ ℓ + 1

lemma cube_map_bijective :
    Function.Bijective (fun x : (Field)ˣ => x ^ (3 : Nat))

@[simp] lemma natCast_eq {k : ℕ} (n : ℕ) : (↑n : ConcreteBTField k) = natCast n

nonpos_iff_eq_zero in Mathlib.Algebra.Order.Monoid.Canonical.Defs

@[simp]
lemma seqCompose_succ {m : ℕ}
    (Stmt : Fin (m + 2) → Type)
    {ιₛ : Fin (m + 2) → Type} (OStmt : (i : Fin (m + 2)) → ιₛ i → Type)
    [Oₛ : ∀ i, ∀ j, OracleInterface (OStmt i j)]
    {n : Fin (m + 1) → ℕ} {pSpec : ∀ i, ProtocolSpec (n i)}
    [Oₘ : ∀ i, ∀ j, OracleInterface ((pSpec i).Message j)]
    (V : (i : Fin (m + 1)) → OracleVerifier oSpec
      (Stmt i.castSucc) (OStmt i.castSucc) (Stmt i.succ) (OStmt i.succ) (pSpec i)) :
    seqCompose Stmt OStmt V =
      append (V 0) (seqCompose (Stmt ∘ Fin.succ) (fun i => OStmt (Fin.succ i))
        (Oₛ := fun i => Oₛ (Fin.succ i)) (Oₘ := fun i => Oₘ (Fin.succ i))
          (fun i => V (Fin.succ i)))

theorem rename_eq_zero_of_injective {τ : Type*} {f : σ → τ} (hf : Function.Injective f)
    {p : MvPolynomial σ R} (h : rename f p = 0) : p = 0

lemma zipWith_const {α β : Type _} {f : α → β → β} {l₁ : List α} {l₂ : List β}
  (h₁ : l₁.length = l₂.length) (h₂ : ∀ a b, f a b = b) : l₁.zipWith f l₂ = l₂

@[simp]
theorem seqCompose_succ_dir {m : ℕ} {n : Fin (m + 1) → ℕ} {pSpec : ∀ i, ProtocolSpec (n i)} :
    (seqCompose pSpec).dir = Fin.vflatten (fun i => (pSpec i).dir)

omit [NeZero ℓ] [NeZero r] [NeZero 𝓡] in
lemma ℓ_lt_r {h_ℓ_add_R_rate : ℓ + 𝓡 < r}
    : ℓ < r

@[simp] theorem toNat_succ (t : AssocNat) : toNat (succ t) = (toNat t).succ

Nat.succ_le_succ in Init.Prelude

lemma concrete_inv_zero {k : ℕ} : concrete_inv (k:=k) 0 = 0

@[simp]
private lemma leadingCoeff_E : (E ωs f p e).leadingCoeff = 1

lemma algebraMap_succ_eq_zero_x {k : ℕ} (h_pos : k > 0) (x : ConcreteBTField (k - 1)) :
  letI instAlgebra := ConcreteBTFieldAlgebra (l:=k-1) (r:=k) (h_le:=by omega)
  algebraMap (ConcreteBTField (k - 1)) (ConcreteBTField k) x = 《 0, x 》

@[simp] theorem toNat_add (a b : AssocNat) : toNat (add a b) = toNat a + toNat b

theorem vcons_injective2 : Function.Injective2 (@vcons α n)

@[simp]
theorem dist_subsingleton {C : Set (n → R)} [Subsingleton C] : ‖C‖₀ = 0

@[simp]
theorem fflatten_splitSum {A : Sort u} {F : A → Sort v} {m : ℕ} {n : Fin m → ℕ}
    {α : (i : Fin (vsum n)) → A}
    (v : (k : Fin (vsum n)) → F (α k)) (k : Fin (vsum n)) :
    fflatten (fun i j => v (embedSum i j)) k = cast (by simp) (v k)

@[simp, grind _=_]
theorem monomialXY_pow {n m k : ℕ} {a : F} :
  monomialXY n m a ^ k = monomialXY (n * k) (m * k) (a ^ k)

lemma HList.toDVec_eq_getValue (l : HList) (i : Fin l.length) : l.toDVec i = l.getValue i

lemma natDeg_sum_eq_of_unique {α : Type} {s : Finset α} {f : α → F[X]} {deg : ℕ}
  (mx : α) (h : mx ∈ s) :
    (f mx).natDegree = deg →
    (∀ y ∈ s, y ≠ mx → (f y).natDegree < deg ∨ f y = 0) →
    (∑ x ∈ s, f x).natDegree = deg

lemma getBit_of_highBits {n: ℕ} (numLowBits : ℕ) : ∀ k, getBit k (getHighBits numLowBits n) =
    if k < numLowBits then 0 else getBit (k) (n)

omit [Finite F] in
lemma mul_root_of_unity {x : Fˣ} :
  ∀ {a b : Fˣ} {i j : ℕ},
    i ≤ j → a ∈ evalDomain D x i → b ∈ Domain.evalDomain D j →
      a * b ∈ evalDomain D x i

lemma towerRingHomForwardMap_one {k : ℕ} :
  (towerRingHomForwardMap k) 1 = 1

theorem unique_linear_decomposition_succ (k : ℕ) :
  letI : Algebra (ConcreteBTField k) (ConcreteBTField (k+1)) :=
    ConcreteBTFieldAlgebra (l:=k) (r:=k+1) (h_le:=by omega)
  ∀ (x : ConcreteBTField (k+1)), ∃! (p : ConcreteBTField k × ConcreteBTField k),
    x = join_via_add_smul (k+1) (by omega) p.1 p.2

@[csimp, grind =]
theorem findIdx'_eq_findIdx : @findIdx' = @findIdx

theorem range_vcons {α : Type*} (a : α) (v : Fin n → α) :
    Set.range (a ::ᵛ v) = insert a (Set.range v)

@[simp]
lemma dotProduct_cons (a : R) (b : Vector R n) (c : R) (d : Vector R n) :
    _root_.dotProduct (cons a b).get (cons c d).get = a * c + _root_.dotProduct b.get d.get

@[simp]
theorem binaryTowerAlgebra_id {l r : ℕ} (h_eq : l = r) :
    @binaryAlgebraTower l r (h_le:=by omega) =
    (h_eq ▸ (Algebra.id (BTField l)) : Algebra (BTField l) (BTField r))

private lemma johnson_condition_strong_implies_2_le_F_card
  (h_johnson : JohnsonConditionStrong B v)
  :
  2 ≤ Fintype.card F

@[simp]
theorem init_update_last : init (update s (Fin.last n) y) = init s

lemma divide_by_2_def {s : Finset ℕ} :
    divide_by_2 s = (erase_odd s).image (fun n => n / 2)

@[simp]
lemma append_last_of_succ_right {u : Fin m → α} {v : Fin (n + 1) → α} :
    (append u v) (last (m + n)) = v (last n)

Fin.isLt in Init.Prelude

lemma concrete_mul_comm
  {h_k : k > 0} (prevBTFieldProps : ConcreteBTFieldProps (k := k - 1))
  (a b : ConcreteBTField k) :
  concrete_mul a b = concrete_mul b a
</all_available_lemmas>

<local_ctx>
import ArkLib.Data.CodingTheory.BerlekampWelch.BerlekampWelch

import ArkLib.Data.CodingTheory.ReedSolomon

import ArkLib.Data.FieldTheory.AdditiveNTT.AdditiveNTT

import ArkLib.Data.MvPolynomial.Multilinear

import ArkLib.Data.Vector.Basic

import ArkLib.ProofSystem.Sumcheck.Spec.SingleRound

namespace Binius.BinaryBasefold

open OracleSpec OracleComp ProtocolSpec Finset AdditiveNTT Polynomial MvPolynomial
  Binius.BinaryBasefold

open scoped NNReal

open ReedSolomon Code BerlekampWelch

open Finset AdditiveNTT Polynomial MvPolynomial Nat Matrix

section Preliminaries

variable {L : Type} [CommRing L] (ℓ : ℕ) [NeZero ℓ]

variable (𝓑 : Fin 2 ↪ L)

end Preliminaries

noncomputable section       -- expands with 𝔽q in front

variable {r : ℕ} [NeZero r]

variable {L : Type} [Field L] [Fintype L] [DecidableEq L] [CharP L 2]

variable (𝔽q : Type) [Field 𝔽q] [Fintype 𝔽q] [DecidableEq 𝔽q]
  [h_Fq_char_prime : Fact (Nat.Prime (ringChar 𝔽q))] [hF₂ : Fact (Fintype.card 𝔽q = 2)]

variable [Algebra 𝔽q L]

variable (β : Fin r → L) [hβ_lin_indep : Fact (LinearIndependent 𝔽q β)]
  [h_β₀_eq_1 : Fact (β 0 = 1)]

variable {ℓ 𝓡 ϑ : ℕ} (γ_repetitions : ℕ) [NeZero ℓ] [NeZero 𝓡] [NeZero ϑ] -- Should we allow ℓ = 0?

variable {h_ℓ_add_R_rate : ℓ + 𝓡 < r} -- ℓ ∈ {1, ..., r-1}

variable {𝓑 : Fin 2 ↪ L}

section Essentials

noncomputable def fiber_coeff
    (i : Fin r) (steps : ℕ)
    (j : Fin (ℓ + 𝓡 - i)) (elementIdx : Fin (2 ^ steps))
    (y_coeffs : Fin (ℓ + 𝓡 - (i + steps)) →₀ 𝔽q) : 𝔽q :=
  if hj : j.val < steps then
    if Nat.getBit (k := j) (n := elementIdx) = 0 then 0 else 1
  else y_coeffs ⟨j.val - steps, by admit /- proof elided -/
    ⟩

noncomputable def qMap_total_fiber
    
      (i : Fin r) (steps : ℕ) (h_i_add_steps : i.val + steps < ℓ + 𝓡)
        (y : sDomain 𝔽q β h_ℓ_add_R_rate (i := ⟨i.val + steps, by admit /- proof elided -/
        ⟩)) :
    Fin (2 ^ steps) → sDomain 𝔽q β h_ℓ_add_R_rate i :=
  if h_steps : steps = 0 then by
    
    subst h_steps
    simp only [add_zero, Fin.eta] at y
    exact fun _ => y
  else by
    
    let basis_y := sDomain_basis 𝔽q β h_ℓ_add_R_rate (i := ⟨i+steps,by admit /- proof elided -/
    ⟩) (by admit /- proof elided -/
    )
    let y_coeffs : Fin (ℓ + 𝓡 - (↑i + steps)) →₀ 𝔽q := basis_y.repr y

    let basis_x := sDomain_basis 𝔽q β h_ℓ_add_R_rate ⟨i, by admit /- proof elided -/
    ⟩ (by admit /- proof elided -/
    )
    exact fun elementIdx => by admit /- proof elided -/

def pointToIterateQuotientIndex (i : Fin (ℓ + 1)) (steps : ℕ) (h_i_add_steps : i.val + steps ≤ ℓ)
    (x : sDomain 𝔽q β h_ℓ_add_R_rate (i := ⟨i, by omega⟩)) : Fin (2 ^ steps) :=
</local_ctx>

<target_theorem>
theorem is_fiber_iff_generates_quotient_point (i : Fin ℓ) (steps : ℕ)
    (h_i_add_steps : i.val + steps ≤ ℓ)
    (x : sDomain 𝔽q β h_ℓ_add_R_rate (i := ⟨i, by omega⟩))
    (y : sDomain 𝔽q β h_ℓ_add_R_rate (i := ⟨i.val + steps, by omega⟩)) :
    let qMapFiber :=
</target_theorem>

