diff --git a/tools/test_reconcile_ledger.py b/tools/test_reconcile_ledger.py
new file mode 100644
index 000000000..791f03828
--- /dev/null
+++ b/tools/test_reconcile_ledger.py
@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+"""Targeted proof of the S45p7 reconcile-ledger fix in dedup_propagate.
+
+The full-propagation negative control did not fire (that run SUCCEEDED), so the guarded
+path was never executed. This exercises the mechanism directly:
+
+  1. take real overlay files, snapshot them
+  2. apply a REAL reconcile via dedup_propagate.reconcile_caller_extern (the same call the
+     --recover Part B path makes) -> files are now edited on disk
+  3. drive the ledger's undo the way the fixed code does when the fn leaves the plan
+  4. assert every file is byte-identical to its original
+
+Read-only w.r.t. git: it restores what it edits, and asserts it did.
+"""
+import sys, os, hashlib
+sys.path.insert(0, os.path.join(os.path.dirname(os.path.abspath(__file__)), '..', '..', 'tools'))
+sys.path.insert(0, 'tools')
+import dedup_propagate as dp
+
+
+def sha(p):
+    return hashlib.sha1(open(p, 'rb').read()).hexdigest()
+
+
+def main():
+    OV, ADDR = 'ov_SC07_010', 0x80146A6C     # the exact overlay+fn from tonight's breakage
+    files = [cp for cp, _ in dp.overlay_files(OV)]
+    before = {str(p): sha(p) for p in files}
+    print(f"[setup] {OV}: {len(files)} source files snapshotted")
+
+    # --- 1. apply a real reconcile (this WRITES) ---
+    snap, n = dp.reconcile_caller_extern(OV, ADDR)
+    after_edit = {str(p): sha(p) for p in files}
+    changed = [k for k in before if before[k] != after_edit.get(k)]
+    print(f"[apply] reconcile_caller_extern -> {n} edit(s); {len(changed)} file(s) changed on disk")
+    if n == 0 or not changed:
+        print("SKIP: this fn/overlay pair produced no reconcile edit — cannot exercise the path.")
+        return 3
+
+    # --- 2. drive the ledger undo exactly as the fixed code does ---
+    kept = [(ADDR, snap)]
+    drop = [r for r in kept if r[0] in {ADDR}]
+    for _a, _s in reversed(drop):
+        dp.restore_snapshot(_s)
+    print(f"[undo]  ledger restored {len(drop)} kept reconcile(s)")
+
+    # --- 3. the assertion ---
+    after = {str(p): sha(p) for p in files}
+    bad = [k for k in before if before[k] != after.get(k)]
+    if bad:
+        print("FAIL — files NOT restored byte-identically:")
+        for k in bad[:5]:
+            print("   ", k)
+        return 1
+    print(f"PASS — all {len(files)} file(s) byte-identical after the ledger undo "
+          f"(the orphan that broke 141/213 cannot survive this path)")
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())