commit 8d67e9519c3604fcbfb229d0652ca3faaa5b0fd2
Author: mrwulf <mrwulf.cleaner@gmail.com>
Date:   Fri Jul 10 23:58:00 2026 +0200

    L1+L2: hashing shapes, domain separation, MTH/Root/ConsRec with termination
    
    Accumulator pyramid layers 1-2, mechanizing paper SS5.3/SS6 groundwork:
    - gen/LTLAcc/HashExternal.lean: the single sanctioned axiom, opaque
      sha256 (no properties assumed - the soundness theorems downstream are
      constructive collision extractors).
    - Proofs/Basic.lean: hleaf/hnode (0x00/0x01 domain stamps); Lemma 1
      (domsep) proven AXIOM-FREE; kbelow (largest power of two below n)
      with pos/lt/le-two bound lemmas; MTH, Root (Option = rejection),
      ConsRec (four cases, b-flag, pinned anchor) - all with kernel-checked
      termination via the kbelow bounds.
    - check.sh: estate discipline (stub audit, axiom-smuggling gate,
      lean-guard compilation, boundary-exact per-certificate cone audit).
      All green; observed cones pinned exactly.
    
    Zero contact with the live LTL: no appends, no server, accumulator
    frozen at 12 leaves throughout this project.
    
    Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..b15c5b9
--- /dev/null
+++ b/README.md
@@ -0,0 +1,33 @@
+# ltl-accumulator-verified
+
+Lean 4 mechanization of the security analysis (§6) of the paper
+"The Lean Transparency Log" (https://ltl.zkdefi.org/paper): the Merkle
+accumulator's own correctness and soundness theorems, kernel-checked, in
+the same discipline as the four `*-ed25519-verified` subject corpora.
+
+## Status: layer scaffold (work in progress — honest ledger below)
+
+| layer | content | status |
+|---|---|---|
+| L1 | bytes, hleaf/hnode, domain separation (Lemma 1) | **done** (domsep: axiom-free) |
+| L2 | MTH, Root, ConsRec definitions + termination | **done** (cones: propext, LTLAcc.sha256, Quot.sound) |
+| L3 | inclusion completeness (Theorem 1) | pending |
+| L4 | frontier hash-fold + root binding (Lemma 2) | pending |
+| L5 | inclusion/consistency soundness as collision extractors (Theorems 2, 3) | pending |
+| L6 | pin-store state machine safety (Proposition 1) | pending |
+
+## Discipline (identical to the subject corpora)
+
+- `verification/Proofs/` contains ZERO `axiom` declarations; the single
+  sanctioned axiom site is `verification/gen/` — here, one opaque
+  function: SHA-256. The theorems are constructive collision extractors,
+  so collision resistance is never assumed, only interpreted.
+- `verification/check.sh` is THE button: compiles every file through
+  `lean-guard` (memory cap, core pinning, timeout, single-flight lock)
+  and axiom-audits every certificate against its documented exact cone.
+- Expected boundary: `propext, Classical.choice, Quot.sound` plus
+  `LTLAcc.sha256` for hash-touching certificates — documented per
+  certificate in `check.sh`, audited both directions.
+
+The finished certificates are destined for the LTL itself as attestation
+leaves: the log carrying kernel-checked proofs of its own machinery.
diff --git a/verification/Proofs/AxiomCheck.lean b/verification/Proofs/AxiomCheck.lean
new file mode 100644
index 0000000..669e2f3
--- /dev/null
+++ b/verification/Proofs/AxiomCheck.lean
@@ -0,0 +1,9 @@
+/- Axiom-cone observation for the audit (Phase 3 of check.sh). -/
+import Proofs.Basic
+#print axioms LTLAcc.domsep
+#print axioms LTLAcc.kbelow_pos
+#print axioms LTLAcc.kbelow_lt
+#print axioms LTLAcc.le_two_kbelow
+#print axioms LTLAcc.MTH
+#print axioms LTLAcc.Root
+#print axioms LTLAcc.ConsRec
diff --git a/verification/Proofs/AxiomCheck.olean b/verification/Proofs/AxiomCheck.olean
new file mode 100644
index 0000000..c21ff1c
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diff --git a/verification/Proofs/Basic.lean b/verification/Proofs/Basic.lean
new file mode 100644
index 0000000..0cf4bf1
--- /dev/null
+++ b/verification/Proofs/Basic.lean
@@ -0,0 +1,151 @@
+/- L1 + L2 of the accumulator pyramid: byte-level hashing shapes, domain
+   separation (paper Lemma 1), the split point, and the three §5.3
+   definitions (MTH, Path-dual Root, ConsRec) with their termination.
+
+   Everything here is stated over the opaque `sha256` of gen/ — no
+   property of the hash is used anywhere in this file. -/
+import LTLAcc.HashExternal
+
+namespace LTLAcc
+
+abbrev Bytes := List UInt8
+
+/-- Leaf hash: `H(0x00 ‖ d)` (paper §5.3). -/
+noncomputable def hleaf (d : Bytes) : Bytes := sha256 (0x00 :: d)
+
+/-- Node hash: `H(0x01 ‖ x ‖ y)` (paper §5.3). -/
+noncomputable def hnode (x y : Bytes) : Bytes := sha256 (0x01 :: (x ++ y))
+
+/-- **Lemma 1 (Domain separation), preimage form**: no leaf preimage
+    equals a node preimage as a byte string — the first byte differs. -/
+theorem domsep (d x y : Bytes) :
+    (0x00 : UInt8) :: d ≠ (0x01 : UInt8) :: (x ++ y) := by
+  intro h
+  injection h with h0 _
+  exact absurd h0 (by decide)
+
+/-- Largest power of two STRICTLY below `n`, for `n ≥ 2` (RFC 9162's
+    split point `k`; values at `n ≤ 1` are irrelevant and default to 1). -/
+def kbelow (n : Nat) : Nat :=
+  if n ≤ 2 then 1
+  else 2 * kbelow ((n + 1) / 2)
+termination_by n
+decreasing_by omega
+
+theorem kbelow_pos (n : Nat) : 0 < kbelow n := by
+  induction n using kbelow.induct with
+  | case1 n h => rw [kbelow]; simp [h]
+  | case2 n h ih => rw [kbelow]; simp [h]; omega
+
+theorem kbelow_lt (n : Nat) (h : 2 ≤ n) : kbelow n < n := by
+  induction n using kbelow.induct with
+  | case1 n hle => rw [kbelow]; simp only [if_pos hle]; omega
+  | case2 n hgt ih =>
+      rw [kbelow]
+      simp only [if_neg hgt]
+      have h2 : 2 ≤ (n + 1) / 2 := by omega
+      have := ih h2
+      omega
+
+theorem le_two_kbelow (n : Nat) (h : 2 ≤ n) : n ≤ 2 * kbelow n := by
+  induction n using kbelow.induct with
+  | case1 n hle => rw [kbelow]; simp only [if_pos hle]; omega
+  | case2 n hgt ih =>
+      rw [kbelow]
+      simp only [if_neg hgt]
+      have h2 : 2 ≤ (n + 1) / 2 := by omega
+      have := ih h2
+      omega
+
+/-- `MTH` (paper §5.3): the RFC 9162 tree head over a leaf-data list.
+    `MTH [] = H(ε)`, `MTH [d] = hleaf d`, and for `n ≥ 2` the split at
+    `k = kbelow n`. -/
+noncomputable def MTH (D : List Bytes) : Bytes :=
+  if _h0 : D.length = 0 then sha256 []
+  else if _h1 : D.length = 1 then hleaf (D.headD [])
+  else
+    hnode (MTH (D.take (kbelow D.length))) (MTH (D.drop (kbelow D.length)))
+termination_by D.length
+decreasing_by
+  · -- take-branch: k < n
+    simp only [List.length_take]
+    have h2 : 2 ≤ D.length := by omega
+    have hk := kbelow_lt D.length h2
+    omega
+  · -- drop-branch: n - k < n
+    simp only [List.length_drop]
+    have h2 : 2 ≤ D.length := by omega
+    have hk := kbelow_lt D.length h2
+    have hp := kbelow_pos D.length
+    omega
+
+/-- `Root` (paper §5.3 / Appendix B): the consumer's root reconstruction.
+    `none` = rejection on any length mismatch, exactly as deployed. -/
+noncomputable def Root (v : Bytes) (m n : Nat) (P : List Bytes) : Option Bytes :=
+  if n = 1 then
+    match P with
+    | [] => some v
+    | _ => none
+  else if n = 0 then none
+  else
+    match P.getLast? with
+    | none => none
+    | some s =>
+        let k := kbelow n
+        if m < k then
+          match Root v m k P.dropLast with
+          | none => none
+          | some x => some (hnode x s)
+        else
+          match Root v (m - k) (n - k) P.dropLast with
+          | none => none
+          | some x => some (hnode s x)
+termination_by n
+decreasing_by
+  · have h2 : 2 ≤ n := by omega
+    exact kbelow_lt n h2
+  · have := kbelow_pos n
+    omega
+
+/-- `ConsRec` (paper §5.3): the recursive consistency verifier. Returns
+    the reconstructed pair (old root, new root); `none` = shape
+    mismatch. The flag `b` records whether the size-`n₀` subtree root is
+    carried implicitly (the pinned root `r`) or explicitly in `C`. -/
+noncomputable def ConsRec (n₀ n : Nat) (C : List Bytes) (b : Bool) (r : Bytes) :
+    Option (Bytes × Bytes) :=
+  if n₀ = n then
+    if b then
+      match C with
+      | [] => some (r, r)
+      | _ => none
+    else
+      match C with
+      | [s] => some (s, s)
+      | _ => none
+  else if n₀ > n ∨ n₀ = 0 ∨ n ≤ 1 then none
+  else
+    match C.getLast? with
+    | none => none
+    | some s =>
+        let k := kbelow n
+        if n₀ ≤ k then
+          match ConsRec n₀ k C.dropLast b r with
+          | none => none
+          | some (x, y) => some (x, hnode y s)
+        else
+          match ConsRec (n₀ - k) (n - k) C.dropLast false r with
+          | none => none
+          | some (x, y) => some (hnode s x, hnode s y)
+termination_by n
+decreasing_by
+  · have h2 : 2 ≤ n := by omega
+    exact kbelow_lt n h2
+  · have := kbelow_pos n
+    omega
+
+/-- The consumer's acceptance predicate for a consistency proof between
+    pinned head `(n₀, r₀)` and offered head `(n₁, r₁)` (paper §5.3). -/
+def acceptCons (n₀ n₁ : Nat) (r₀ r₁ : Bytes) (C : List Bytes) : Prop :=
+  n₀ = 0 ∨ ConsRec n₀ n₁ C true r₀ = some (r₀, r₁)
+
+end LTLAcc
diff --git a/verification/Proofs/Basic.olean b/verification/Proofs/Basic.olean
new file mode 100644
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diff --git a/verification/check.sh b/verification/check.sh
new file mode 100755
index 0000000..8e86693
--- /dev/null
+++ b/verification/check.sh
@@ -0,0 +1,105 @@
+#!/usr/bin/env bash
+# ─────────────────────────────────────────────────────────────────────────────
+# check.sh — THE button (accumulator corpus). Same discipline as the
+# *-ed25519-verified repos: compiles every shipped .lean through lean-guard
+# and axiom-audits every certificate against its DOCUMENTED exact cone,
+# both directions.
+#
+# Phases: 0 resource/integrity · 1 stub+axiom-smuggling audit ·
+#         2 compile manifest · 3 boundary-exact axiom audit
+# ─────────────────────────────────────────────────────────────────────────────
+set -euo pipefail
+source ~/aeneas-toolchain/env.sh
+HERE="$(cd "$(dirname "$0")" && pwd)"
+AENEAS_LEAN="$AENEAS_HOME/backends/lean"
+TIMEOUT="${LEAN_TIMEOUT:-600}"
+export LEAN_MEM_MB="${LEAN_MEM_MB:-4096}"
+CORES="${LEAN_MAX_CORES:-0-3}"
+
+GEN_MODULES=( LTLAcc/HashExternal )
+PROOFS=( Basic )
+
+# Certificates and their exact expected cones (observed at first green
+# compile, 2026-07-10; any drift in EITHER direction is a failure).
+declare -A CONES=(
+  [LTLAcc.domsep]=""
+  [LTLAcc.kbelow_pos]="propext, Quot.sound"
+  [LTLAcc.kbelow_lt]="propext, Quot.sound"
+  [LTLAcc.le_two_kbelow]="propext, Quot.sound"
+  [LTLAcc.MTH]="propext, LTLAcc.sha256, Quot.sound"
+  [LTLAcc.Root]="propext, LTLAcc.sha256, Quot.sound"
+  [LTLAcc.ConsRec]="propext, LTLAcc.sha256, Quot.sound"
+)
+
+free -m | awk '/Mem:/{if($7<2048){print "FATAL: <2GB RAM available — refusing to compile"; exit 1}}'
+echo "=== Phase 0: source integrity ==="
+for f in "$HERE"/gen/LTLAcc/*.lean "$HERE"/Proofs/*.lean; do
+  [ -f "$f" ] || continue
+  if ! grep -qE '^(/-|import |namespace |theorem |def |noncomputable |open |set_option |--|abbrev )' "$f"; then
+    echo "CORRUPTED: $f is not Lean source. Restore: git checkout HEAD -- $f"; exit 1
+  fi
+done
+echo "  all sources valid"
+
+echo "=== Phase 1: stub + axiom-smuggling audit ==="
+if grep -rn 'by trivial' "$HERE"/Proofs/*.lean 2>/dev/null; then
+  echo "STUB DETECTED"; exit 1; fi
+if grep -rn ' : True :=' "$HERE"/Proofs/*.lean 2>/dev/null; then
+  echo "STUB DETECTED: True-target theorem"; exit 1; fi
+if grep -rnE '^(private |protected |noncomputable )*axiom ' "$HERE"/Proofs/*.lean 2>/dev/null; then
+  echo "AXIOM SMUGGLING DETECTED: axiom under Proofs/ — gen/ is the only sanctioned site."; exit 1
+fi
+echo "  clean"
+
+echo "=== Phase 2: compile ==="
+LOG=$(mktemp /tmp/acc-check-XXXX.log)
+cd "$AENEAS_LEAN"
+lake env bash -c "
+  set -euo pipefail
+  cd '$HERE/gen' && export LEAN_PATH=\"\$LEAN_PATH:\$PWD:$HERE\"
+  compile() {
+    echo \"  · \$1\"
+    LEAN_TIMEOUT=$TIMEOUT LEAN_MAX_CORES=$CORES '$HERE/lean-guard' \"\${1}.lean\" 2>&1 | tee -a '$LOG' || { echo \"FAIL: \$1\"; exit 1; }
+  }
+  for m in ${GEN_MODULES[*]}; do compile \"\$m\"; done
+  cd '$HERE'
+  for m in ${PROOFS[*]}; do
+    [ -f \"Proofs/\$m.lean\" ] || { echo \"MISSING: Proofs/\$m.lean\"; exit 1; }
+    compile \"Proofs/\$m\"
+  done
+  for f in Proofs/*.lean; do
+    b=\$(basename \"\$f\" .lean)
+    [ \"\$b\" = AxiomCheck ] && continue
+    case \" ${PROOFS[*]} \" in (*\" \$b \"*) ;; (*) echo \"DEAD FILE: \$f\"; exit 1;; esac
+  done
+"
+if grep -q "uses 'sorry'" "$LOG"; then echo "STUB: sorry detected"; exit 1; fi
+rm -f "$LOG"
+
+echo "=== Phase 3: boundary-exact axiom audit ==="
+AUD=$(mktemp /tmp/acc-audit-XXXX.log)
+cd "$AENEAS_LEAN"
+lake env bash -c "
+  cd '$HERE' && export LEAN_PATH=\"\$LEAN_PATH:$HERE/gen:$HERE\"
+  LEAN_TIMEOUT=300 LEAN_MAX_CORES=$CORES '$HERE/lean-guard' Proofs/AxiomCheck.lean
+" > "$AUD" 2>&1 || { cat "$AUD"; exit 1; }
+FAIL=0
+for cert in "${!CONES[@]}"; do
+  want="${CONES[$cert]}"
+  if [ -z "$want" ]; then
+    exp="'$cert' does not depend on any axioms"
+  else
+    exp="'$cert' depends on axioms: [$want]"
+  fi
+  if ! grep -qF "$exp" "$AUD"; then
+    echo "  CONE DRIFT: $cert"
+    echo "    expected: $exp"
+    echo "    observed: $(grep -F "'$cert'" "$AUD" || echo '(missing)')"
+    FAIL=1
+  else
+    echo "  ✓ $cert  [$want]"
+  fi
+done
+rm -f "$AUD"
+[ "$FAIL" = 0 ] || exit 1
+echo "=== ALL GREEN ==="
diff --git a/verification/gen/LTLAcc/HashExternal.lean b/verification/gen/LTLAcc/HashExternal.lean
new file mode 100644
index 0000000..349c344
--- /dev/null
+++ b/verification/gen/LTLAcc/HashExternal.lean
@@ -0,0 +1,12 @@
+/- The single sanctioned axiom site of this corpus (mirrors the role of
+   gen/ in the *-ed25519-verified repos): SHA-256 as an opaque function.
+   No properties are assumed of it — in particular NOT collision
+   resistance. The soundness theorems downstream are constructive: they
+   EXHIBIT two distinct preimages with equal image. Believing such a
+   pair cannot be found is the reader's interpretation step, exactly as
+   documented in the paper (§6, Remark 1). -/
+namespace LTLAcc
+
+axiom sha256 : List UInt8 → List UInt8
+
+end LTLAcc
diff --git a/verification/gen/LTLAcc/HashExternal.olean b/verification/gen/LTLAcc/HashExternal.olean
new file mode 100644
index 0000000..7377445
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diff --git a/verification/lean-guard b/verification/lean-guard
new file mode 100755
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--- /dev/null
+++ b/verification/lean-guard
@@ -0,0 +1,189 @@
+#!/usr/bin/env bash
+# ────────────────────────────────────────────────────────────────────────────
+# lean-guard — HARD-CAPPED Lean compiler wrapper.
+#
+# Successor to lean-safe after the 2026-07-02 OOM incident: a single `lean`
+# elaboration (tactic-search blowup: simp[*]/scalar_tac over a ~60-hypothesis
+# context with 2^256-scale literals) grew to 12.2GB RSS and was killed by the
+# GLOBAL kernel OOM killer, taking the driving session down with it.
+# lean-safe's guards (timeout + affinity + PREFLIGHT headroom) cannot stop
+# that: the process passes preflight, then balloons inside its timeout.
+#
+# NEW GUARDS (in addition to all lean-safe guards):
+#   A. lean -M <MB>                  — Lean's internal cap: elaboration aborts
+#                                      with a clean "maximum memory exceeded"
+#                                      error. First line of defense; graceful.
+#   B. systemd-run --user --scope
+#        -p MemoryMax / MemorySwapMax — kernel cgroup cap around the process:
+#                                      if Lean's own accounting misses (C-level
+#                                      allocations), the cgroup kills ONLY this
+#                                      lean, never the session, never the box.
+#   C. flock on /tmp/lean-guard.lock — machine-wide single-flight: at most ONE
+#                                      lean compile at a time, regardless of
+#                                      how many agents/scripts are active.
+#
+# Env knobs (defaults for this 14GB / 8-core ThinkPad):
+#   LEAN_TIMEOUT      per-file wall clock seconds        (default 400)
+#   LEAN_MEM_MB       lean -M internal cap, MB           (default 4096)
+#   LEAN_CGROUP_MB    cgroup MemoryMax, MB               (default LEAN_MEM_MB+1024)
+#   LEAN_MAX_CORES    taskset core range                 (default 0-3)
+#   LEAN_MIN_FREE_MB  preflight available-RAM floor      (default 3072)
+#   LEAN_LOCK_WAIT    max seconds to wait for the lock   (default 7200)
+#
+# Usage:  lean-guard <file.lean> [extra lean args...]
+# The .olean output path is always computed as ${file%.lean}.olean.
+# Requires: lean on PATH (caller sources the toolchain env; typically run
+# inside `lake env` so LEAN_PATH is set — this wrapper does NOT clobber env).
+# ────────────────────────────────────────────────────────────────────────────
+set -uo pipefail
+
+# No core dumps: hitting the memory cap makes lean (and uutils `timeout`) abort;
+# those aborts are EXPECTED and their core dumps only trigger Ubuntu apport
+# popups and fill /var/crash. ulimit applies to this shell and every child.
+ulimit -c 0 2>/dev/null || true
+
+TIMEOUT_SEC=${LEAN_TIMEOUT:-400}
+MEM_MB=${LEAN_MEM_MB:-4096}
+CGROUP_MB=${LEAN_CGROUP_MB:-$((MEM_MB + 1024))}
+CORES=${LEAN_MAX_CORES:-0-3}
+MIN_FREE_MB=${LEAN_MIN_FREE_MB:-3072}
+LOCK_WAIT=${LEAN_LOCK_WAIT:-7200}
+LOCK_FILE=/tmp/lean-guard.lock
+LOG_FILE="${HOME}/.lean-guard.log"
+
+if ! command -v lean &>/dev/null; then
+    echo "FATAL: lean not on PATH — source ~/aeneas-toolchain/env.sh (and run inside lake env)"
+    exit 1
+fi
+if [ $# -eq 0 ]; then
+    echo "Usage: lean-guard <file.lean> [lean args...]"
+    exit 1
+fi
+
+LEAN_FILE="$1"; shift || true
+
+# ── Guard 1: source integrity (anti olean-clobber) ──────────────────────────
+if [ ! -f "$LEAN_FILE" ]; then
+    echo "MISSING: $LEAN_FILE"; exit 1
+fi
+if ! grep -qE '^[[:space:]]*(/-|import |namespace |theorem |def |open |set_option |--)' "$LEAN_FILE" 2>/dev/null; then
+    echo "FATAL: $LEAN_FILE is not Lean source (binary/olean data?)."
+    echo "  Restore: git checkout HEAD -- $LEAN_FILE"
+    exit 1
+fi
+
+# ── Guard 2: output path ─────────────────────────────────────────────────────
+case "$LEAN_FILE" in
+  *.lean) ;;
+  *) echo "FATAL: input lacks .lean extension"; exit 1 ;;
+esac
+OLEAN_FILE="${LEAN_FILE%.lean}.olean"
+[ "$OLEAN_FILE" = "$LEAN_FILE" ] && { echo "FATAL: output would clobber source"; exit 1; }
+
+# ── Guard C: machine-wide single-flight ─────────────────────────────────────
+exec 9>"$LOCK_FILE"
+if ! flock -w "$LOCK_WAIT" 9; then
+    echo "FATAL: could not acquire lean-guard lock within ${LOCK_WAIT}s (another compile stuck?)"
+    exit 1
+fi
+
+# ── Guard 3: preflight headroom (after lock: serialized measurement) ────────
+AVAIL_MB=$(free -m | awk '/Mem:/{print $7}')
+if [ "$AVAIL_MB" -lt "$MIN_FREE_MB" ]; then
+    echo "FATAL: only ${AVAIL_MB}MB available (< ${MIN_FREE_MB}MB floor) — refusing to compile"
+    exit 1
+fi
+
+
+# ── Guard 3b: global-headroom clamp (2026-07-03 swap-pressure incident) ─────
+# A cap is a PROMISE of memory to lean; never promise more than the machine
+# can afford right now. Requested caps that exceed (available − floor) are
+# clamped, so raising LEAN_MEM_MB can no longer starve the rest of the system
+# into swap even when lean itself stays within its cap. Clamp, don't fail:
+# most compiles peak far below their cap (measure before raising — the
+# incident's 9G scopes served a file whose true peak was 753MB).
+REQ_MEM_MB=$MEM_MB
+WAS_CLAMPED=0
+MAX_AFFORD_MB=$(( AVAIL_MB - MIN_FREE_MB ))
+if [ "$MEM_MB" -gt "$MAX_AFFORD_MB" ]; then
+    echo "lean-guard: clamping -M ${MEM_MB} -> ${MAX_AFFORD_MB}MB (avail=${AVAIL_MB}MB, floor=${MIN_FREE_MB}MB)"
+    MEM_MB=$MAX_AFFORD_MB
+    CGROUP_MB=$(( MEM_MB + 1024 ))
+    WAS_CLAMPED=1
+fi
+if [ "$MEM_MB" -lt 1024 ]; then
+    echo "FATAL: headroom clamp would leave lean < 1024MB — machine too loaded to compile safely"
+    exit 1
+fi
+
+echo "[$(date -u +%F' '%T)] $LEAN_FILE (t=${TIMEOUT_SEC}s M=${MEM_MB}MB cg=${CGROUP_MB}MB cores=$CORES avail=${AVAIL_MB}MB)" >> "$LOG_FILE"
+
+# ── Compile under both caps ──────────────────────────────────────────────────
+run_leancmd() {
+    taskset -c "$CORES" \
+      timeout --signal=TERM --kill-after=15 "$TIMEOUT_SEC" \
+      lean -M "$MEM_MB" -o "$OLEAN_FILE" "$LEAN_FILE" "$@"
+}
+do_compile() {
+    if systemd-run --user --scope -p MemoryMax=10M --quiet -- /bin/true 2>/dev/null; then
+        # --scope runs the command as a child of THIS shell (env inherited),
+        # merely placing it in a fresh cgroup with the hard caps below.
+        systemd-run --user --scope --quiet \
+            -p MemoryMax="${CGROUP_MB}M" -p MemorySwapMax=256M \
+            -- taskset -c "$CORES" \
+               timeout --signal=TERM --kill-after=15 "$TIMEOUT_SEC" \
+               lean -M "$MEM_MB" -o "$OLEAN_FILE" "$LEAN_FILE" "$@"
+    else
+        echo "  (systemd-run unavailable — falling back to lean -M only)" >> "$LOG_FILE"
+        run_leancmd "$@"
+    fi
+}
+do_compile "$@"
+EXIT_CODE=$?
+
+# ── Guard 3a: lazy wait-and-retry after a clamped memory abort (pass 3) ─────
+# The clamp above protects the host, but under ambient memory pressure it
+# can cut a KNOWN-NEEDED cap (ReduceSpec peaks ~6.5G) and guarantee an
+# interpreter abort that reads like a proof regression. Lazy semantics keep
+# light files free: only when a CLAMPED run dies on memory (134 abort /
+# 137 cgroup kill) and LEAN_MEM_WAIT_SEC>0, wait — still under the
+# single-flight lock — until the ORIGINAL request is affordable, then retry
+# once at full cap. Default 0: behavior unchanged.
+MEM_WAIT_SEC=${LEAN_MEM_WAIT_SEC:-0}
+if [ "$WAS_CLAMPED" -eq 1 ] && [ "$MEM_WAIT_SEC" -gt 0 ]; then
+    WAITED=0
+    # Retry ladder: whenever headroom improves MATERIALLY (>= +1536MB over
+    # the cap that just died, or reaches the full request), retry at the
+    # new clamp. The full request may never be affordable on a loaded host
+    # even though the true peak is — climbing the ladder finds the passing
+    # clamp without knowing the peak. Monotone caps + deadline => bounded.
+    while { [ "$EXIT_CODE" -eq 134 ] || [ "$EXIT_CODE" -eq 137 ]; } \
+          && [ "$WAITED" -lt "$MEM_WAIT_SEC" ] && [ "$MEM_MB" -lt "$REQ_MEM_MB" ]; do
+        sleep 20; WAITED=$(( WAITED + 20 ))
+        AVAIL_MB=$(free -m | awk '/Mem:/{print $7}')
+        NEW_AFFORD=$(( AVAIL_MB - MIN_FREE_MB ))
+        if [ "$NEW_AFFORD" -ge "$REQ_MEM_MB" ] || [ "$NEW_AFFORD" -ge $(( MEM_MB + 1536 )) ]; then
+            MEM_MB=$(( NEW_AFFORD < REQ_MEM_MB ? NEW_AFFORD : REQ_MEM_MB ))
+            CGROUP_MB=$(( MEM_MB + 1024 ))
+            echo "lean-guard: clamped run died (rc=$EXIT_CODE); retrying at -M ${MEM_MB}MB after ${WAITED}s (avail=${AVAIL_MB}MB, request=${REQ_MEM_MB}MB)"
+            echo "[$(date -u +%F' '%T)] RETRY $LEAN_FILE (M=${MEM_MB}MB cg=${CGROUP_MB}MB avail=${AVAIL_MB}MB after ${WAITED}s)" >> "$LOG_FILE"
+            do_compile "$@"
+            EXIT_CODE=$?
+        fi
+    done
+    if [ "$EXIT_CODE" -eq 134 ] || [ "$EXIT_CODE" -eq 137 ]; then
+        echo "lean-guard: memory-death persists after ${WAITED}s of ladder retries (last -M ${MEM_MB}MB, request ${REQ_MEM_MB}MB) — keeping the failure"
+    fi
+fi
+
+case $EXIT_CODE in
+  0)   echo "  OK" >> "$LOG_FILE" ;;
+  124) echo "  TIMEOUT ${TIMEOUT_SEC}s" >> "$LOG_FILE"
+       echo "TIMEOUT: $LEAN_FILE exceeded ${TIMEOUT_SEC}s" ;;
+  137) echo "  KILLED (cgroup MemoryMax ${CGROUP_MB}MB hit)" >> "$LOG_FILE"
+       echo "KILLED: $LEAN_FILE hit the ${CGROUP_MB}MB cgroup cap (contained — machine unharmed)" ;;
+  *)   echo "  FAILED exit $EXIT_CODE (lean error, possibly '-M ${MEM_MB}MB exceeded')" >> "$LOG_FILE" ;;
+esac
+# stale partial olean from a failed compile must not poison later imports
+[ $EXIT_CODE -ne 0 ] && rm -f "$OLEAN_FILE"
+exit $EXIT_CODE