From 18b17f442b045686bee420b81b3e889cb80fd71e Mon Sep 17 00:00:00 2001
From: YurenHao0426 <Blackhao0426@gmail.com>
Date: Mon, 27 Jul 2026 13:51:07 -0500
Subject: [PATCH 16/19] experiment: lock P2 source and cell registry

---
 crossover_grid.py | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/crossover_grid.py b/crossover_grid.py
index cbd9b98..4523250 100644
--- a/crossover_grid.py
+++ b/crossover_grid.py
@@ -180,6 +180,43 @@ def p2_jobs():
     ]
 
 
+def p2_registry_sha256(jobs):
+    encoded = json.dumps(
+        jobs, sort_keys=True, separators=(",", ":")).encode("utf-8")
+    return hashlib.sha256(encoded).hexdigest()
+
+
+def ensure_p2_launch(source, jobs):
+    path = os.path.join(ROOT, "runs", "plain-p2-launch.json")
+    immutable = {
+        "stage": "p2",
+        "source": source,
+        "selector_path": SELECTOR,
+        "selector_sha256": SELECTOR_SHA256,
+        "num_registered_cells": len(jobs),
+        "registry_sha256": p2_registry_sha256(jobs),
+        "jobs": jobs,
+    }
+    if os.path.exists(path):
+        with open(path, encoding="utf-8") as handle:
+            existing = json.load(handle)
+        for key, value in immutable.items():
+            if existing.get(key) != value:
+                raise RuntimeError(f"P2 launch lock drift in {key}")
+        return path
+    record = {**immutable, "created_unix_time": time.time()}
+    os.makedirs(os.path.dirname(path), exist_ok=True)
+    try:
+        descriptor = os.open(
+            path, os.O_WRONLY | os.O_CREAT | os.O_EXCL, 0o644)
+    except FileExistsError:
+        return ensure_p2_launch(source, jobs)
+    with os.fdopen(descriptor, "w", encoding="utf-8") as handle:
+        json.dump(record, handle, indent=2, sort_keys=True)
+        handle.write("\n")
+    return path
+
+
 def p2_command(method, architecture, rate):
     cli_method = {
         "bp": "backprop",
@@ -673,6 +710,9 @@ def main():
         raise ValueError("invalid shard")
     source = source_report()
     jobs = p1_jobs() if args.stage == "p1" else p2_jobs()
+    if args.stage == "p2" and not args.dry_run:
+        launch = ensure_p2_launch(source, jobs)
+        print(f"P2 launch lock: {launch}", flush=True)
     if args.method:
         jobs = [job for job in jobs if job["method"] == args.method]
     jobs = [
-- 
2.54.0