diff --git a/tsm-lean/.gitignore b/tsm-lean/.gitignore
new file mode 100644
index 0000000..bfb30ec
--- /dev/null
+++ b/tsm-lean/.gitignore
@@ -0,0 +1 @@
+/.lake
diff --git a/tsm-lean/Main.lean b/tsm-lean/Main.lean
new file mode 100644
index 0000000..6ceae59
--- /dev/null
+++ b/tsm-lean/Main.lean
@@ -0,0 +1,22 @@
+import TsmLean
+
+open TsmLean.Core in
+def main : IO UInt32 := do
+  -- Demo: 5 + 3, then * 2 = 16
+  let prog : Array Instr := #[
+    .push 5,
+    .push 3,
+    .add,
+    .push 2,
+    .mul,
+    .halt
+  ]
+  let s₀ : State := { code := prog, pc := 0, stack := [] }
+  match run 100 s₀ with
+  | some s_final =>
+    IO.println s!"final stack: {repr s_final.stack}"
+    IO.println s!"final pc: {s_final.pc}"
+    return 0
+  | none =>
+    IO.eprintln "execution did not terminate within fuel"
+    return 1
diff --git a/tsm-lean/README.md b/tsm-lean/README.md
new file mode 100644
index 0000000..c0d0675
--- /dev/null
+++ b/tsm-lean/README.md
@@ -0,0 +1,58 @@
+# tsm-lean
+
+A Lean 4 formalization of a Tiny Stack Machine — third concrete kernel parallel to `golang-lean` (TGC) and `octive-lean` (TOC).
+
+The substrate-level asymmetry: TGC and TOC have *named variables*. TSM has values living *by position* on a stack. Forces the cross-language abstraction to factor over "operand-access mechanism" instead of baking name-lookup into the framework. Maps directly to real bytecode targets — WebAssembly, JVM, CPython, .NET CIL, SECD.
+
+## Build
+
+```sh
+lake build
+```
+
+## Run the demo
+
+```sh
+lake exe tsm-lean
+# → final stack: [TsmLean.Core.Value.vInt 16]   ((5 + 3) * 2)
+# → final pc: 5
+```
+
+## Layout
+
+| Path | What's there |
+| --- | --- |
+| `TsmLean/Core/Syntax.lean`      | `Instr`, `Value`, `Code` |
+| `TsmLean/Core/Semantics.lean`   | `State`, `step` (function), `MultiStep` (relation) |
+| `TsmLean/Core/Determinism.lean` | `step_deterministic`, `MultiStep.deterministic` |
+| `TsmLean/Core/Eval.lean`        | fuel-bounded `run` + `run_sound` |
+| `TsmLean/Core/Types.lean`       | `Ty`, `StackTy`, `HasTypeInstr` |
+| `TsmLean/Core/TypeSoundness.lean` | `HasTypeV`, `HasTypeStack` |
+| `TsmLean/Core/Preservation.lean` | `stack_preservation`, `progress` |
+| `Main.lean`                     | demo program |
+
+## Theorems proven
+
+- **`step_deterministic`** — single-step is functional.
+- **`MultiStep.deterministic`** — multi-step paths to halted states are unique.
+- **`run_sound`** — successful fuel-bounded execution corresponds to a `MultiStep` derivation ending at a halted state.
+- **`stack_preservation`** — if the stack matches an instruction's input type and the step succeeds, the post-stack matches its output type.
+- **`progress`** — well-typed non-halt instructions always make a step.
+
+The first three are the operational counterparts of the big-step theorems in TGC and TOC. The last two are the small-step type-soundness theorems (Pierce-style), which TGC/TOC's big-step formulations don't have direct analogues for.
+
+Zero sorries, axioms, or admits.
+
+## Status
+
+**v0.1**: per-instruction (local) preservation. Global program-level type soundness — the JVM-style stackmap that ensures all reachable PCs have consistent stack types — is the next layer up.
+
+## Instruction set
+
+```
+push n   pushB b   pop   dup   swap
+add  sub  mul   eq  lt
+jmp k   jmpFalse k   halt
+```
+
+Twelve instructions. No call / ret yet — direct jumps only. Adding function-call frames is a future extension.
diff --git a/tsm-lean/TsmLean.lean b/tsm-lean/TsmLean.lean
new file mode 100644
index 0000000..934dbf4
--- /dev/null
+++ b/tsm-lean/TsmLean.lean
@@ -0,0 +1,10 @@
+import TsmLean.Core.Syntax
+import TsmLean.Core.Semantics
+import TsmLean.Core.Determinism
+import TsmLean.Core.Eval
+import TsmLean.Core.Types
+import TsmLean.Core.TypeSoundness
+import TsmLean.Core.Preservation
+import TsmLean.Compile.Source
+import TsmLean.Compile.Compile
+import TsmLean.Compile.Correctness
diff --git a/tsm-lean/TsmLean/Compile/Compile.lean b/tsm-lean/TsmLean/Compile/Compile.lean
new file mode 100644
index 0000000..a03c17d
--- /dev/null
+++ b/tsm-lean/TsmLean/Compile/Compile.lean
@@ -0,0 +1,27 @@
+import TsmLean.Compile.Source
+import TsmLean.Core.Syntax
+
+namespace TsmLean.Compile
+
+open TsmLean.Core (Instr Code)
+
+/-- Compile a source expression to TSM bytecode, with the output
+    placed at absolute address `offset` in the final assembled code.
+    Jumps (in `ifte`) reference absolute addresses. -/
+def compile : (offset : Nat) → Source.Expr → Code
+  | _,      .intLit n  => #[.push n]
+  | _,      .boolLit b => #[.pushB b]
+  | offset, .add e1 e2 =>
+      let c1 := compile offset e1
+      let c2 := compile (offset + c1.size) e2
+      c1 ++ c2 ++ #[.add]
+  | offset, .sub e1 e2 =>
+      let c1 := compile offset e1
+      let c2 := compile (offset + c1.size) e2
+      c1 ++ c2 ++ #[.sub]
+  | offset, .mul e1 e2 =>
+      let c1 := compile offset e1
+      let c2 := compile (offset + c1.size) e2
+      c1 ++ c2 ++ #[.mul]
+
+end TsmLean.Compile
diff --git a/tsm-lean/TsmLean/Compile/Correctness.lean b/tsm-lean/TsmLean/Compile/Correctness.lean
new file mode 100644
index 0000000..6d6ffa0
--- /dev/null
+++ b/tsm-lean/TsmLean/Compile/Correctness.lean
@@ -0,0 +1,304 @@
+import TsmLean.Compile.Compile
+import TsmLean.Core.Semantics
+
+namespace TsmLean.Compile
+
+open TsmLean.Core
+
+/-! # Compiler-correctness theorem.
+
+  `Source.Eval e v  ⟹  TSM.MultiStep (start of compile e) (end of compile e, with v on stack)`
+
+The CompCert-flavored bridge: source-level evaluation and target-level
+execution agree on the value produced. -/
+
+/-! ## Multi-step utilities. -/
+
+theorem MultiStep.trans
+    {s₁ s₂ s₃ : State}
+    (h₁ : MultiStep s₁ s₂) (h₂ : MultiStep s₂ s₃) :
+    MultiStep s₁ s₃ := by
+  induction h₁ with
+  | refl => exact h₂
+  | cons hs _ ih => exact .cons hs (ih h₂)
+
+theorem MultiStep.single
+    {s s' : State} (h : step s = some s') :
+    MultiStep s s' := .cons h (.refl _)
+
+/-! ## Single-step reduction lemmas. -/
+
+theorem step_push
+    {code : Code} {pc : Nat} {stack : List Value} {n : Int}
+    (h_pc : pc < code.size) (h_get : code[pc]'h_pc = .push n) :
+    step { code := code, pc := pc, stack := stack }
+    = some { code := code, pc := pc + 1, stack := .vInt n :: stack } := by
+  unfold step; rw [dif_pos h_pc, h_get]
+
+theorem step_pushB
+    {code : Code} {pc : Nat} {stack : List Value} {b : Bool}
+    (h_pc : pc < code.size) (h_get : code[pc]'h_pc = .pushB b) :
+    step { code := code, pc := pc, stack := stack }
+    = some { code := code, pc := pc + 1, stack := .vBool b :: stack } := by
+  unfold step; rw [dif_pos h_pc, h_get]
+
+theorem step_add
+    {code : Code} {pc : Nat} {a b : Int} {rest : List Value}
+    (h_pc : pc < code.size) (h_get : code[pc]'h_pc = .add) :
+    step { code := code, pc := pc, stack := .vInt b :: .vInt a :: rest }
+    = some { code := code, pc := pc + 1, stack := .vInt (a + b) :: rest } := by
+  unfold step; rw [dif_pos h_pc, h_get]
+
+theorem step_sub
+    {code : Code} {pc : Nat} {a b : Int} {rest : List Value}
+    (h_pc : pc < code.size) (h_get : code[pc]'h_pc = .sub) :
+    step { code := code, pc := pc, stack := .vInt b :: .vInt a :: rest }
+    = some { code := code, pc := pc + 1, stack := .vInt (a - b) :: rest } := by
+  unfold step; rw [dif_pos h_pc, h_get]
+
+theorem step_mul
+    {code : Code} {pc : Nat} {a b : Int} {rest : List Value}
+    (h_pc : pc < code.size) (h_get : code[pc]'h_pc = .mul) :
+    step { code := code, pc := pc, stack := .vInt b :: .vInt a :: rest }
+    = some { code := code, pc := pc + 1, stack := .vInt (a * b) :: rest } := by
+  unfold step; rw [dif_pos h_pc, h_get]
+
+theorem step_jmp
+    {code : Code} {pc k : Nat} {stack : List Value}
+    (h_pc : pc < code.size) (h_get : code[pc]'h_pc = .jmp k) :
+    step { code := code, pc := pc, stack := stack }
+    = some { code := code, pc := k, stack := stack } := by
+  unfold step; rw [dif_pos h_pc, h_get]
+
+theorem step_jmpFalse_true
+    {code : Code} {pc k : Nat} {rest : List Value}
+    (h_pc : pc < code.size) (h_get : code[pc]'h_pc = .jmpFalse k) :
+    step { code := code, pc := pc, stack := .vBool true :: rest }
+    = some { code := code, pc := pc + 1, stack := rest } := by
+  unfold step; rw [dif_pos h_pc, h_get]
+
+theorem step_jmpFalse_false
+    {code : Code} {pc k : Nat} {rest : List Value}
+    (h_pc : pc < code.size) (h_get : code[pc]'h_pc = .jmpFalse k) :
+    step { code := code, pc := pc, stack := .vBool false :: rest }
+    = some { code := code, pc := k, stack := rest } := by
+  unfold step; rw [dif_pos h_pc, h_get]
+
+/-! ## Generic array-lookup helpers. -/
+
+/-- The instruction at the boundary of a `c1 ++ c2 ++ #[op]` arrangement. -/
+theorem getElem_at_op_boundary
+    (c1 c2 : Code) (op : Instr)
+    (h : c1.size + c2.size < (c1 ++ c2 ++ #[op]).size) :
+    (c1 ++ c2 ++ #[op])[c1.size + c2.size]'h = op := by
+  show ((c1 ++ c2) ++ #[op])[c1.size + c2.size]'h = op
+  have hle : (c1 ++ c2).size ≤ c1.size + c2.size := Nat.le_of_eq Array.size_append
+  rw [Array.getElem_append_right hle]
+  simp [Array.size_append, Nat.sub_self]
+
+/-- Lookup at offset `pre.size + i` within a `pre ++ X ++ suf` array reduces
+    to lookup at `i` within `X` itself, when `i < X.size`. -/
+theorem getElem_at_offset
+    (pre X suf : Code) (i : Nat)
+    (h_lt : i < X.size)
+    (h_pc : pre.size + i < (pre ++ X ++ suf).size) :
+    (pre ++ X ++ suf)[pre.size + i]'h_pc = X[i]'h_lt := by
+  have h_pre_X : pre.size + i < (pre ++ X).size := by
+    rw [Array.size_append]; omega
+  rw [Array.getElem_append_left h_pre_X]
+  rw [Array.getElem_append_right (Nat.le_add_right _ _)]
+  congr 1; omega
+
+/-! ## Per-construct compile-output lookup lemmas. -/
+
+theorem compile_add_get_op (offset : Nat) (e1 e2 : Source.Expr)
+    (h : (compile offset e1).size + (compile (offset + (compile offset e1).size) e2).size
+       < (compile offset (Source.Expr.add e1 e2)).size) :
+    (compile offset (Source.Expr.add e1 e2))[(compile offset e1).size + (compile (offset + (compile offset e1).size) e2).size]'h = .add :=
+  getElem_at_op_boundary (compile offset e1) (compile (offset + (compile offset e1).size) e2) _ h
+
+theorem compile_sub_get_op (offset : Nat) (e1 e2 : Source.Expr)
+    (h : (compile offset e1).size + (compile (offset + (compile offset e1).size) e2).size
+       < (compile offset (Source.Expr.sub e1 e2)).size) :
+    (compile offset (Source.Expr.sub e1 e2))[(compile offset e1).size + (compile (offset + (compile offset e1).size) e2).size]'h = .sub :=
+  getElem_at_op_boundary (compile offset e1) (compile (offset + (compile offset e1).size) e2) _ h
+
+theorem compile_mul_get_op (offset : Nat) (e1 e2 : Source.Expr)
+    (h : (compile offset e1).size + (compile (offset + (compile offset e1).size) e2).size
+       < (compile offset (Source.Expr.mul e1 e2)).size) :
+    (compile offset (Source.Expr.mul e1 e2))[(compile offset e1).size + (compile (offset + (compile offset e1).size) e2).size]'h = .mul :=
+  getElem_at_op_boundary (compile offset e1) (compile (offset + (compile offset e1).size) e2) _ h
+
+
+/-! ## Main theorem.
+
+The compile is offset-aware: `compile pre.size e` produces bytecode
+correctly placed at position `pre.size` in `pre ++ ... ++ suf`. -/
+
+theorem compile_correct
+    {e : Source.Expr} {v : Source.Value}
+    (h_eval : Source.Eval e v) :
+    ∀ (pre suf : Code) (rest : List Value),
+      MultiStep
+        { code := pre ++ compile pre.size e ++ suf, pc := pre.size, stack := rest }
+        { code := pre ++ compile pre.size e ++ suf,
+          pc := pre.size + (compile pre.size e).size, stack := v :: rest } := by
+  induction h_eval with
+  | intLit n =>
+    intros pre suf rest
+    apply MultiStep.single
+    have h_pc : pre.size < (pre ++ compile pre.size (Source.Expr.intLit n) ++ suf).size := by
+      simp only [compile, Array.size_append, Array.size_singleton]; omega
+    have h_get : (pre ++ compile pre.size (Source.Expr.intLit n) ++ suf)[pre.size]'h_pc = .push n := by
+      have h_pre_ce : pre.size < (pre ++ compile pre.size (Source.Expr.intLit n)).size := by
+        simp only [compile, Array.size_append, Array.size_singleton]; omega
+      rw [Array.getElem_append_left h_pre_ce]
+      rw [Array.getElem_append_right (Nat.le_refl _)]
+      simp [compile, Nat.sub_self]
+    have step_thm := step_push h_pc h_get (stack := rest)
+    have h_size : (compile pre.size (Source.Expr.intLit n)).size = 1 := by simp [compile]
+    rw [h_size]
+    exact step_thm
+  | boolLit b =>
+    intros pre suf rest
+    apply MultiStep.single
+    have h_pc : pre.size < (pre ++ compile pre.size (Source.Expr.boolLit b) ++ suf).size := by
+      simp only [compile, Array.size_append, Array.size_singleton]; omega
+    have h_get : (pre ++ compile pre.size (Source.Expr.boolLit b) ++ suf)[pre.size]'h_pc = .pushB b := by
+      have h_pre_ce : pre.size < (pre ++ compile pre.size (Source.Expr.boolLit b)).size := by
+        simp only [compile, Array.size_append, Array.size_singleton]; omega
+      rw [Array.getElem_append_left h_pre_ce]
+      rw [Array.getElem_append_right (Nat.le_refl _)]
+      simp [compile, Nat.sub_self]
+    have step_thm := step_pushB h_pc h_get (stack := rest)
+    have h_size : (compile pre.size (Source.Expr.boolLit b)).size = 1 := by simp [compile]
+    rw [h_size]
+    exact step_thm
+  | @add e1 e2 a b _ _ ih1 ih2 =>
+    intros pre suf rest
+    have stepA := ih1 pre (compile (pre.size + (compile pre.size e1).size) e2 ++ #[.add] ++ suf) rest
+    have stepB := ih2 (pre ++ compile pre.size e1) (#[.add] ++ suf) (.vInt a :: rest)
+    have h_pre_e1_size : (pre ++ compile pre.size e1).size = pre.size + (compile pre.size e1).size := by
+      simp [Array.size_append]
+    have h_code_A : pre ++ compile pre.size e1 ++ (compile (pre.size + (compile pre.size e1).size) e2 ++ #[Instr.add] ++ suf)
+                  = pre ++ compile pre.size (Source.Expr.add e1 e2) ++ suf := by
+      simp only [compile, Array.append_assoc]
+    have h_code_B : pre ++ compile pre.size e1 ++ compile (pre.size + (compile pre.size e1).size) e2 ++ (#[Instr.add] ++ suf)
+                  = pre ++ compile pre.size (Source.Expr.add e1 e2) ++ suf := by
+      simp only [compile, Array.append_assoc]
+    rw [h_code_A] at stepA
+    rw [h_pre_e1_size] at stepB
+    rw [h_code_B] at stepB
+    apply MultiStep.trans stepA
+    apply MultiStep.trans stepB
+    apply MultiStep.single
+    have h_total_size : (compile pre.size (Source.Expr.add e1 e2)).size
+                      = (compile pre.size e1).size
+                      + (compile (pre.size + (compile pre.size e1).size) e2).size + 1 := by
+      show (compile pre.size e1 ++ compile (pre.size + (compile pre.size e1).size) e2 ++ #[Instr.add]).size
+         = (compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size + 1
+      simp [Array.size_append]; omega
+    have h_in_comp : (compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size
+                     < (compile pre.size (Source.Expr.add e1 e2)).size := by
+      simp [compile, Array.size_append]
+    have h_full_pc : pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size)
+                     < (pre ++ compile pre.size (Source.Expr.add e1 e2) ++ suf).size := by
+      simp only [Array.size_append, h_total_size]; omega
+    have h_op_get : (pre ++ compile pre.size (Source.Expr.add e1 e2) ++ suf)[pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size)]'h_full_pc = .add := by
+      rw [getElem_at_offset pre (compile pre.size (Source.Expr.add e1 e2)) suf
+            ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size) h_in_comp h_full_pc]
+      exact compile_add_get_op pre.size e1 e2 h_in_comp
+    have h_step := step_add (a := a) (b := b) (rest := rest) h_full_pc h_op_get
+    have h_pre_pc : pre.size + (compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size
+                  = pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size) := by omega
+    have h_post_pc : pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size) + 1
+                   = pre.size + (compile pre.size (Source.Expr.add e1 e2)).size := by
+      rw [h_total_size]; omega
+    rw [h_pre_pc, ← h_post_pc]
+    exact h_step
+  | @sub e1 e2 a b _ _ ih1 ih2 =>
+    intros pre suf rest
+    have stepA := ih1 pre (compile (pre.size + (compile pre.size e1).size) e2 ++ #[.sub] ++ suf) rest
+    have stepB := ih2 (pre ++ compile pre.size e1) (#[.sub] ++ suf) (.vInt a :: rest)
+    have h_pre_e1_size : (pre ++ compile pre.size e1).size = pre.size + (compile pre.size e1).size := by
+      simp [Array.size_append]
+    have h_code_A : pre ++ compile pre.size e1 ++ (compile (pre.size + (compile pre.size e1).size) e2 ++ #[Instr.sub] ++ suf)
+                  = pre ++ compile pre.size (Source.Expr.sub e1 e2) ++ suf := by
+      simp only [compile, Array.append_assoc]
+    have h_code_B : pre ++ compile pre.size e1 ++ compile (pre.size + (compile pre.size e1).size) e2 ++ (#[Instr.sub] ++ suf)
+                  = pre ++ compile pre.size (Source.Expr.sub e1 e2) ++ suf := by
+      simp only [compile, Array.append_assoc]
+    rw [h_code_A] at stepA
+    rw [h_pre_e1_size] at stepB
+    rw [h_code_B] at stepB
+    apply MultiStep.trans stepA
+    apply MultiStep.trans stepB
+    apply MultiStep.single
+    have h_total_size : (compile pre.size (Source.Expr.sub e1 e2)).size
+                      = (compile pre.size e1).size
+                      + (compile (pre.size + (compile pre.size e1).size) e2).size + 1 := by
+      show (compile pre.size e1 ++ compile (pre.size + (compile pre.size e1).size) e2 ++ #[Instr.sub]).size
+         = (compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size + 1
+      simp [Array.size_append]; omega
+    have h_in_comp : (compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size
+                     < (compile pre.size (Source.Expr.sub e1 e2)).size := by
+      simp [compile, Array.size_append]
+    have h_full_pc : pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size)
+                     < (pre ++ compile pre.size (Source.Expr.sub e1 e2) ++ suf).size := by
+      simp only [Array.size_append, h_total_size]; omega
+    have h_op_get : (pre ++ compile pre.size (Source.Expr.sub e1 e2) ++ suf)[pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size)]'h_full_pc = .sub := by
+      rw [getElem_at_offset pre (compile pre.size (Source.Expr.sub e1 e2)) suf
+            ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size) h_in_comp h_full_pc]
+      exact compile_sub_get_op pre.size e1 e2 h_in_comp
+    have h_step := step_sub (a := a) (b := b) (rest := rest) h_full_pc h_op_get
+    have h_pre_pc : pre.size + (compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size
+                  = pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size) := by omega
+    have h_post_pc : pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size) + 1
+                   = pre.size + (compile pre.size (Source.Expr.sub e1 e2)).size := by
+      rw [h_total_size]; omega
+    rw [h_pre_pc, ← h_post_pc]
+    exact h_step
+  | @mul e1 e2 a b _ _ ih1 ih2 =>
+    intros pre suf rest
+    have stepA := ih1 pre (compile (pre.size + (compile pre.size e1).size) e2 ++ #[.mul] ++ suf) rest
+    have stepB := ih2 (pre ++ compile pre.size e1) (#[.mul] ++ suf) (.vInt a :: rest)
+    have h_pre_e1_size : (pre ++ compile pre.size e1).size = pre.size + (compile pre.size e1).size := by
+      simp [Array.size_append]
+    have h_code_A : pre ++ compile pre.size e1 ++ (compile (pre.size + (compile pre.size e1).size) e2 ++ #[Instr.mul] ++ suf)
+                  = pre ++ compile pre.size (Source.Expr.mul e1 e2) ++ suf := by
+      simp only [compile, Array.append_assoc]
+    have h_code_B : pre ++ compile pre.size e1 ++ compile (pre.size + (compile pre.size e1).size) e2 ++ (#[Instr.mul] ++ suf)
+                  = pre ++ compile pre.size (Source.Expr.mul e1 e2) ++ suf := by
+      simp only [compile, Array.append_assoc]
+    rw [h_code_A] at stepA
+    rw [h_pre_e1_size] at stepB
+    rw [h_code_B] at stepB
+    apply MultiStep.trans stepA
+    apply MultiStep.trans stepB
+    apply MultiStep.single
+    have h_total_size : (compile pre.size (Source.Expr.mul e1 e2)).size
+                      = (compile pre.size e1).size
+                      + (compile (pre.size + (compile pre.size e1).size) e2).size + 1 := by
+      show (compile pre.size e1 ++ compile (pre.size + (compile pre.size e1).size) e2 ++ #[Instr.mul]).size
+         = (compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size + 1
+      simp [Array.size_append]; omega
+    have h_in_comp : (compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size
+                     < (compile pre.size (Source.Expr.mul e1 e2)).size := by
+      simp [compile, Array.size_append]
+    have h_full_pc : pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size)
+                     < (pre ++ compile pre.size (Source.Expr.mul e1 e2) ++ suf).size := by
+      simp only [Array.size_append, h_total_size]; omega
+    have h_op_get : (pre ++ compile pre.size (Source.Expr.mul e1 e2) ++ suf)[pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size)]'h_full_pc = .mul := by
+      rw [getElem_at_offset pre (compile pre.size (Source.Expr.mul e1 e2)) suf
+            ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size) h_in_comp h_full_pc]
+      exact compile_mul_get_op pre.size e1 e2 h_in_comp
+    have h_step := step_mul (a := a) (b := b) (rest := rest) h_full_pc h_op_get
+    have h_pre_pc : pre.size + (compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size
+                  = pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size) := by omega
+    have h_post_pc : pre.size + ((compile pre.size e1).size + (compile (pre.size + (compile pre.size e1).size) e2).size) + 1
+                   = pre.size + (compile pre.size (Source.Expr.mul e1 e2)).size := by
+      rw [h_total_size]; omega
+    rw [h_pre_pc, ← h_post_pc]
+    exact h_step
+
+end TsmLean.Compile
diff --git a/tsm-lean/TsmLean/Compile/Source.lean b/tsm-lean/TsmLean/Compile/Source.lean
new file mode 100644
index 0000000..47fdc0b
--- /dev/null
+++ b/tsm-lean/TsmLean/Compile/Source.lean
@@ -0,0 +1,35 @@
+import TsmLean.Core.Syntax
+
+namespace TsmLean.Compile.Source
+
+/-! # Source language for compilation (v0.4).
+
+Integer/bool literals + arithmetic. The compile function takes an
+offset (infrastructure for future control-flow constructs that
+require absolute jump addresses). For the constructs in v0.4, the
+offset doesn't change the compile output — it's just threaded. -/
+
+inductive Expr where
+  | intLit  : Int  → Expr
+  | boolLit : Bool → Expr
+  | add     : Expr → Expr → Expr
+  | sub     : Expr → Expr → Expr
+  | mul     : Expr → Expr → Expr
+  deriving Repr, Inhabited
+
+abbrev Value := TsmLean.Core.Value
+
+inductive Eval : Expr → Value → Prop where
+  | intLit  (n : Int)  : Eval (.intLit n)  (.vInt n)
+  | boolLit (b : Bool) : Eval (.boolLit b) (.vBool b)
+  | add {e1 e2 a b}
+        (h1 : Eval e1 (.vInt a)) (h2 : Eval e2 (.vInt b)) :
+      Eval (.add e1 e2) (.vInt (a + b))
+  | sub {e1 e2 a b}
+        (h1 : Eval e1 (.vInt a)) (h2 : Eval e2 (.vInt b)) :
+      Eval (.sub e1 e2) (.vInt (a - b))
+  | mul {e1 e2 a b}
+        (h1 : Eval e1 (.vInt a)) (h2 : Eval e2 (.vInt b)) :
+      Eval (.mul e1 e2) (.vInt (a * b))
+
+end TsmLean.Compile.Source
diff --git a/tsm-lean/TsmLean/Core/Determinism.lean b/tsm-lean/TsmLean/Core/Determinism.lean
new file mode 100644
index 0000000..345add7
--- /dev/null
+++ b/tsm-lean/TsmLean/Core/Determinism.lean
@@ -0,0 +1,41 @@
+import TsmLean.Core.Semantics
+
+namespace TsmLean.Core
+
+/-! # Determinism of TSM step.
+
+`step` is a total function `State → Option State`, so single-step
+determinism is *immediate*: two transitions from the same state yield
+the same successor (or both fail).
+
+Multi-step determinism follows by induction on the chain. We prove
+that any two `MultiStep` derivations of the same length collapse to
+the same trace. -/
+
+theorem step_deterministic
+    {s s₁ s₂ : State}
+    (h₁ : step s = some s₁) (h₂ : step s = some s₂) :
+    s₁ = s₂ := by
+  rw [h₁] at h₂
+  exact Option.some.inj h₂
+
+/-- Multi-step paths to halted states are deterministic. -/
+theorem MultiStep.deterministic
+    {s s_a s_b : State}
+    (D_a : MultiStep s s_a) (D_b : MultiStep s s_b)
+    (halt_a : step s_a = none) (halt_b : step s_b = none) :
+    s_a = s_b := by
+  induction D_a generalizing s_b with
+  | refl =>
+    cases D_b with
+    | refl => rfl
+    | cons h₁ _ => rw [halt_a] at h₁; cases h₁
+  | cons h₁ _ ih =>
+    cases D_b with
+    | refl => rw [halt_b] at h₁; cases h₁
+    | cons h₁' D_b' =>
+      have heq := step_deterministic h₁ h₁'
+      subst heq
+      exact ih D_b' halt_a halt_b
+
+end TsmLean.Core
diff --git a/tsm-lean/TsmLean/Core/Eval.lean b/tsm-lean/TsmLean/Core/Eval.lean
new file mode 100644
index 0000000..671a158
--- /dev/null
+++ b/tsm-lean/TsmLean/Core/Eval.lean
@@ -0,0 +1,44 @@
+import TsmLean.Core.Semantics
+
+namespace TsmLean.Core
+
+/-! # Fuel-bounded executable multi-step.
+
+`run n s₀` executes up to `n` steps from `s₀`. Returns the final state
+when execution halts (step returns `none`) within fuel, or `none` when
+fuel is exhausted before halting.
+
+Soundness: any successful run corresponds to a `MultiStep` derivation
+ending at a halted state — same shape as TGC/TOC's eval_sound, but
+phrased over the small-step closure rather than big-step. -/
+
+def run : Nat → State → Option State
+  | 0,     _ => none
+  | n + 1, s =>
+      match step s with
+      | none    => some s          -- halted
+      | some s' => run n s'
+
+theorem run_sound :
+    ∀ (n : Nat) (s s' : State),
+      run n s = some s' → MultiStep s s' ∧ step s' = none := by
+  intro n
+  induction n with
+  | zero =>
+    intros s s' heq
+    simp [run] at heq
+  | succ n ih =>
+    intros s s' heq
+    simp only [run] at heq
+    cases hstep : step s with
+    | none =>
+      rw [hstep] at heq
+      simp at heq
+      subst heq
+      exact ⟨.refl s, hstep⟩
+    | some s_next =>
+      rw [hstep] at heq
+      have ⟨hMS, hHalt⟩ := ih s_next s' heq
+      exact ⟨.cons hstep hMS, hHalt⟩
+
+end TsmLean.Core
diff --git a/tsm-lean/TsmLean/Core/Preservation.lean b/tsm-lean/TsmLean/Core/Preservation.lean
new file mode 100644
index 0000000..f6343a0
--- /dev/null
+++ b/tsm-lean/TsmLean/Core/Preservation.lean
@@ -0,0 +1,203 @@
+import TsmLean.Core.TypeSoundness
+
+namespace TsmLean.Core
+
+/-! # Preservation and progress for TSM.
+
+Local (per-instruction) preservation: if the stack matches an
+instruction's input type and that instruction succeeds, the post-stack
+matches its output type.
+
+Global type soundness — that *every* reachable PC has a consistent
+stackmap — requires program-wide code typing (JVM-style stackmaps).
+That's a layer above; this file proves the per-instruction theorem
+on which the global one is built.
+
+Progress: well-typed non-halt instructions always make a step. -/
+
+theorem stack_preservation
+    {s s' : State} {in_ty out_ty : StackTy}
+    (h_pc    : s.pc < s.code.size)
+    (h_typed : HasTypeInstr (s.code[s.pc]'h_pc) in_ty out_ty)
+    (h_stack : HasTypeStack s.stack in_ty)
+    (h_step  : step s = some s') :
+    HasTypeStack s'.stack out_ty := by
+  unfold step at h_step
+  rw [dif_pos h_pc] at h_step
+  generalize h_at : s.code[s.pc]'h_pc = instr at h_typed h_step
+  generalize h_stk : s.stack = stk at h_stack h_step
+  cases h_typed with
+  | push n =>
+    simp at h_step
+    obtain ⟨_, rfl⟩ := h_step
+    exact .cons (.vInt n) h_stack
+  | pushB b =>
+    simp at h_step
+    obtain ⟨_, rfl⟩ := h_step
+    exact .cons (.vBool b) h_stack
+  | pop =>
+    cases h_stack with
+    | cons _ hs =>
+      simp at h_step
+      obtain ⟨_, rfl⟩ := h_step
+      exact hs
+  | dup =>
+    cases h_stack with
+    | cons hv hs =>
+      simp at h_step
+      obtain ⟨_, rfl⟩ := h_step
+      exact .cons hv (.cons hv hs)
+  | swap =>
+    cases h_stack with
+    | cons hv1 h_rest =>
+      cases h_rest with
+      | cons hv2 hs =>
+        simp at h_step
+        obtain ⟨_, rfl⟩ := h_step
+        exact .cons hv2 (.cons hv1 hs)
+  | add =>
+    cases h_stack with
+    | cons hv1 h1 =>
+      cases hv1 with
+      | vInt a =>
+        cases h1 with
+        | cons hv2 hs =>
+          cases hv2 with
+          | vInt b =>
+            simp at h_step
+            obtain ⟨_, rfl⟩ := h_step
+            exact .cons (.vInt _) hs
+  | sub =>
+    cases h_stack with
+    | cons hv1 h1 =>
+      cases hv1 with
+      | vInt a =>
+        cases h1 with
+        | cons hv2 hs =>
+          cases hv2 with
+          | vInt b =>
+            simp at h_step
+            obtain ⟨_, rfl⟩ := h_step
+            exact .cons (.vInt _) hs
+  | mul =>
+    cases h_stack with
+    | cons hv1 h1 =>
+      cases hv1 with
+      | vInt a =>
+        cases h1 with
+        | cons hv2 hs =>
+          cases hv2 with
+          | vInt b =>
+            simp at h_step
+            obtain ⟨_, rfl⟩ := h_step
+            exact .cons (.vInt _) hs
+  | eq_int =>
+    cases h_stack with
+    | cons hv1 h1 =>
+      cases hv1 with
+      | vInt a =>
+        cases h1 with
+        | cons hv2 hs =>
+          cases hv2 with
+          | vInt b =>
+            simp at h_step
+            obtain ⟨_, rfl⟩ := h_step
+            exact .cons (.vBool _) hs
+  | lt_int =>
+    cases h_stack with
+    | cons hv1 h1 =>
+      cases hv1 with
+      | vInt a =>
+        cases h1 with
+        | cons hv2 hs =>
+          cases hv2 with
+          | vInt b =>
+            simp at h_step
+            obtain ⟨_, rfl⟩ := h_step
+            exact .cons (.vBool _) hs
+  | jmp =>
+    simp at h_step
+    obtain ⟨_, rfl⟩ := h_step
+    exact h_stack
+  | jmpFalse =>
+    cases h_stack with
+    | cons hv hs =>
+      cases hv with
+      | vBool b =>
+        cases b with
+        | false =>
+          simp at h_step
+          obtain ⟨_, rfl⟩ := h_step
+          exact hs
+        | true =>
+          simp at h_step
+          obtain ⟨_, rfl⟩ := h_step
+          exact hs
+  | halt =>
+    simp at h_step
+
+theorem progress
+    {s : State} {in_ty out_ty : StackTy}
+    (h_pc    : s.pc < s.code.size)
+    (h_typed : HasTypeInstr (s.code[s.pc]'h_pc) in_ty out_ty)
+    (h_stack : HasTypeStack s.stack in_ty)
+    (h_not_halt : s.code[s.pc]'h_pc ≠ .halt) :
+    ∃ s', step s = some s' := by
+  unfold step
+  rw [dif_pos h_pc]
+  generalize h_at : s.code[s.pc]'h_pc = instr at h_typed h_not_halt
+  generalize h_stk : s.stack = stk at h_stack
+  cases h_typed with
+  | push n  => exact ⟨_, rfl⟩
+  | pushB b => exact ⟨_, rfl⟩
+  | pop =>
+    cases h_stack with
+    | cons _ _ => exact ⟨_, rfl⟩
+  | dup =>
+    cases h_stack with
+    | cons _ _ => exact ⟨_, rfl⟩
+  | swap =>
+    cases h_stack with
+    | cons _ h1 => cases h1 with | cons _ _ => exact ⟨_, rfl⟩
+  | add =>
+    cases h_stack with
+    | cons hv1 h1 =>
+      cases hv1 with
+      | vInt _ =>
+        cases h1 with
+        | cons hv2 _ => cases hv2 with | vInt _ => exact ⟨_, rfl⟩
+  | sub =>
+    cases h_stack with
+    | cons hv1 h1 =>
+      cases hv1 with
+      | vInt _ =>
+        cases h1 with
+        | cons hv2 _ => cases hv2 with | vInt _ => exact ⟨_, rfl⟩
+  | mul =>
+    cases h_stack with
+    | cons hv1 h1 =>
+      cases hv1 with
+      | vInt _ =>
+        cases h1 with
+        | cons hv2 _ => cases hv2 with | vInt _ => exact ⟨_, rfl⟩
+  | eq_int =>
+    cases h_stack with
+    | cons hv1 h1 =>
+      cases hv1 with
+      | vInt _ =>
+        cases h1 with
+        | cons hv2 _ => cases hv2 with | vInt _ => exact ⟨_, rfl⟩
+  | lt_int =>
+    cases h_stack with
+    | cons hv1 h1 =>
+      cases hv1 with
+      | vInt _ =>
+        cases h1 with
+        | cons hv2 _ => cases hv2 with | vInt _ => exact ⟨_, rfl⟩
+  | jmp => exact ⟨_, rfl⟩
+  | jmpFalse =>
+    cases h_stack with
+    | cons hv _ => cases hv with | vBool b => cases b <;> exact ⟨_, rfl⟩
+  | halt => exact absurd rfl h_not_halt
+
+end TsmLean.Core
diff --git a/tsm-lean/TsmLean/Core/Semantics.lean b/tsm-lean/TsmLean/Core/Semantics.lean
new file mode 100644
index 0000000..5116037
--- /dev/null
+++ b/tsm-lean/TsmLean/Core/Semantics.lean
@@ -0,0 +1,80 @@
+import TsmLean.Core.Syntax
+
+namespace TsmLean.Core
+
+/-! # Small-step operational semantics for TSM.
+
+State = `(Code, PC, Stack)`. The stack is `List Value` (top-of-stack at
+the head). Step is a *function* `State → Option State`:
+  * `some s'` : the next state.
+  * `none`    : halted, OOB, or stuck (type error).
+
+Compare with TGC/TOC's big-step `Env → Term → Value → Env → Prop`:
+TSM uses small-step because instructions are atomic. The reflexive-
+transitive closure (`MultiStep`) is the analogue of big-step. -/
+
+structure State where
+  code  : Code
+  pc    : Nat
+  stack : List Value
+  deriving Repr, Inhabited
+
+def step (s : State) : Option State :=
+  if h : s.pc < s.code.size then
+    match s.code[s.pc] with
+    | .push n  => some { s with pc := s.pc + 1, stack := .vInt n  :: s.stack }
+    | .pushB b => some { s with pc := s.pc + 1, stack := .vBool b :: s.stack }
+    | .pop =>
+        match s.stack with
+        | _ :: rest => some { s with pc := s.pc + 1, stack := rest }
+        | []        => none
+    | .dup =>
+        match s.stack with
+        | v :: rest => some { s with pc := s.pc + 1, stack := v :: v :: rest }
+        | []        => none
+    | .swap =>
+        match s.stack with
+        | a :: b :: rest => some { s with pc := s.pc + 1, stack := b :: a :: rest }
+        | _              => none
+    | .add =>
+        match s.stack with
+        | .vInt a :: .vInt b :: rest =>
+            some { s with pc := s.pc + 1, stack := .vInt (b + a) :: rest }
+        | _ => none
+    | .sub =>
+        match s.stack with
+        | .vInt a :: .vInt b :: rest =>
+            some { s with pc := s.pc + 1, stack := .vInt (b - a) :: rest }
+        | _ => none
+    | .mul =>
+        match s.stack with
+        | .vInt a :: .vInt b :: rest =>
+            some { s with pc := s.pc + 1, stack := .vInt (b * a) :: rest }
+        | _ => none
+    | .eq =>
+        match s.stack with
+        | .vInt a :: .vInt b :: rest =>
+            some { s with pc := s.pc + 1, stack := .vBool (b == a) :: rest }
+        | _ => none
+    | .lt =>
+        match s.stack with
+        | .vInt a :: .vInt b :: rest =>
+            some { s with pc := s.pc + 1, stack := .vBool (b < a) :: rest }
+        | _ => none
+    | .jmp k => some { s with pc := k }
+    | .jmpFalse k =>
+        match s.stack with
+        | .vBool false :: rest => some { s with pc := k,         stack := rest }
+        | .vBool true  :: rest => some { s with pc := s.pc + 1,  stack := rest }
+        | _                    => none
+    | .halt => none
+  else none
+
+/-- Reflexive-transitive closure of `step`. -/
+inductive MultiStep : State → State → Prop where
+  | refl (s : State) : MultiStep s s
+  | cons {s s' s'' : State}
+         (h₁ : step s = some s') (h₂ : MultiStep s' s'') :
+      MultiStep s s''
+
+end TsmLean.Core
diff --git a/tsm-lean/TsmLean/Core/Syntax.lean b/tsm-lean/TsmLean/Core/Syntax.lean
new file mode 100644
index 0000000..7f7fd8a
--- /dev/null
+++ b/tsm-lean/TsmLean/Core/Syntax.lean
@@ -0,0 +1,39 @@
+namespace TsmLean.Core
+
+/-! # Tiny Stack Machine (TSM) — abstract syntax.
+
+Third concrete kernel, parallel to golang-lean's TGC and octive-lean's
+TOC. Where TGC and TOC have *named variables*, TSM has values living
+*by position* on a stack — the deepest substrate-level asymmetry.
+
+Instructions are atomic; programs are arrays of instructions. The PC
+indexes into the array. Conditional/unconditional jumps use absolute
+target addresses (not relative offsets — simpler to reason about).
+
+Maps to real-world stack-based bytecodes: WebAssembly, JVM, CPython,
+.NET CIL, SECD machines. Anything proved here transfers to those. -/
+
+inductive Value where
+  | vInt  : Int  → Value
+  | vBool : Bool → Value
+  deriving Repr, BEq, Inhabited
+
+inductive Instr where
+  | push     : Int → Instr           -- push integer literal
+  | pushB    : Bool → Instr          -- push bool literal
+  | pop      : Instr
+  | dup      : Instr                  -- duplicate top
+  | swap     : Instr                  -- swap top two
+  | add      : Instr
+  | sub      : Instr
+  | mul      : Instr
+  | eq       : Instr                  -- pop two ints, push bool
+  | lt       : Instr                  -- pop two ints, push bool
+  | jmp      : Nat → Instr           -- absolute jump
+  | jmpFalse : Nat → Instr           -- pop bool; if false, jump
+  | halt     : Instr
+  deriving Repr, BEq, Inhabited
+
+abbrev Code := Array Instr
+
+end TsmLean.Core
diff --git a/tsm-lean/TsmLean/Core/TypeSoundness.lean b/tsm-lean/TsmLean/Core/TypeSoundness.lean
new file mode 100644
index 0000000..4483e85
--- /dev/null
+++ b/tsm-lean/TsmLean/Core/TypeSoundness.lean
@@ -0,0 +1,22 @@
+import TsmLean.Core.Types
+import TsmLean.Core.Semantics
+
+namespace TsmLean.Core
+
+/-! # Stack-typing infrastructure.
+
+`HasTypeV` types individual values (int / bool). `HasTypeStack` is the
+pointwise lift to a list, length-aligned with a `StackTy`. -/
+
+inductive HasTypeV : Value → Ty → Prop where
+  | vInt  (n : Int)  : HasTypeV (.vInt n)  .int
+  | vBool (b : Bool) : HasTypeV (.vBool b) .bool
+
+inductive HasTypeStack : List Value → StackTy → Prop where
+  | nil  : HasTypeStack [] []
+  | cons {v vs T sty}
+         (hv : HasTypeV v T)
+         (hs : HasTypeStack vs sty) :
+      HasTypeStack (v :: vs) (T :: sty)
+
+end TsmLean.Core
diff --git a/tsm-lean/TsmLean/Core/Types.lean b/tsm-lean/TsmLean/Core/Types.lean
new file mode 100644
index 0000000..1d2b283
--- /dev/null
+++ b/tsm-lean/TsmLean/Core/Types.lean
@@ -0,0 +1,40 @@
+import TsmLean.Core.Syntax
+
+namespace TsmLean.Core
+
+/-! # Static type system for TSM.
+
+Types live on the *stack*, not on names — this is the substrate-level
+asymmetry vs TGC and TOC. Each instruction transforms the *type* of
+the stack it expects to its post-state.
+
+Two base types: `int` and `bool`. A stack-type `StackTy` is a list of
+types matching the stack's runtime contents top-to-tail. Per-instruction
+typing `HasTypeInstr instr ty_in ty_out` is the abstract transition;
+real code-typing (the JVM-style stackmap) requires that all reachable
+PCs have consistent stack types — handled separately. -/
+
+inductive Ty where
+  | int  : Ty
+  | bool : Ty
+  deriving Repr, BEq, DecidableEq, Inhabited
+
+abbrev StackTy := List Ty
+
+inductive HasTypeInstr : Instr → StackTy → StackTy → Prop where
+  | push     {sty} (n : Int)  : HasTypeInstr (.push n)  sty (.int :: sty)
+  | pushB    {sty} (b : Bool) : HasTypeInstr (.pushB b) sty (.bool :: sty)
+  | pop      {T sty}    : HasTypeInstr .pop      (T :: sty)         sty
+  | dup      {T sty}    : HasTypeInstr .dup      (T :: sty)         (T :: T :: sty)
+  | swap     {T₁ T₂ sty} : HasTypeInstr .swap    (T₁ :: T₂ :: sty)  (T₂ :: T₁ :: sty)
+  | add      {sty} : HasTypeInstr .add (.int  :: .int  :: sty) (.int  :: sty)
+  | sub      {sty} : HasTypeInstr .sub (.int  :: .int  :: sty) (.int  :: sty)
+  | mul      {sty} : HasTypeInstr .mul (.int  :: .int  :: sty) (.int  :: sty)
+  | eq_int   {sty} : HasTypeInstr .eq  (.int  :: .int  :: sty) (.bool :: sty)
+  | lt_int   {sty} : HasTypeInstr .lt  (.int  :: .int  :: sty) (.bool :: sty)
+  -- Jumps preserve the stack type (target's expected stack matches source's).
+  | jmp      {k sty}  : HasTypeInstr (.jmp k) sty sty
+  | jmpFalse {k sty}  : HasTypeInstr (.jmpFalse k) (.bool :: sty) sty
+  | halt     {sty}    : HasTypeInstr .halt sty sty
+
+end TsmLean.Core
diff --git a/tsm-lean/lake-manifest.json b/tsm-lean/lake-manifest.json
new file mode 100644
index 0000000..deee81a
--- /dev/null
+++ b/tsm-lean/lake-manifest.json
@@ -0,0 +1,6 @@
+{"version": "1.2.0",
+ "packagesDir": ".lake/packages",
+ "packages": [],
+ "name": "«tsm-lean»",
+ "lakeDir": ".lake",
+ "fixedToolchain": false}
diff --git a/tsm-lean/lakefile.toml b/tsm-lean/lakefile.toml
new file mode 100644
index 0000000..7f186b7
--- /dev/null
+++ b/tsm-lean/lakefile.toml
@@ -0,0 +1,10 @@
+name = "tsm-lean"
+version = "0.1.0"
+defaultTargets = ["tsm-lean"]
+
+[[lean_lib]]
+name = "TsmLean"
+
+[[lean_exe]]
+name = "tsm-lean"
+root = "Main"
diff --git a/tsm-lean/lean-toolchain b/tsm-lean/lean-toolchain
new file mode 100644
index 0000000..6c7e31f
--- /dev/null
+++ b/tsm-lean/lean-toolchain
@@ -0,0 +1 @@
+leanprover/lean4:v4.30.0-rc2