diff --git a/tests/_m11b2d_scratch.py b/tests/_m11b2d_scratch.py
new file mode 100644
index 0000000..ba92bed
--- /dev/null
+++ b/tests/_m11b2d_scratch.py
@@ -0,0 +1,113 @@
+import sys
+sys.path.insert(0, "/d/pipeline/workspaces/0/sdlc_general/modules/world_sync/tests")
+import _m11b2_compat as c
+
+_orig = c._default_clause
+
+
+def patched(fd):
+    dv = fd.get("default")
+    if isinstance(dv, str) and dv.strip() == "":
+        return " DEFAULT ''"
+    return _orig(fd)
+
+
+c._default_clause = patched
+
+e = c.RuntimeEngine()
+c.install(e)
+r = c.apply(tenant_id=7, world_id=11, session_id=22, event_type="unit.move",
+            payload={"dx": 1}, state_updates=[{"entity_id": "e1", "state": {"hp": 2}}],
+            client_event_id="ev-1", actor_id="u1")
+print("R1", r)
+print("trace", c.trace_kinds(e))
+print("counts", e.count(c.EVENT_TABLE), e.count(c.STATE_TABLE))
+print("updates", c.update_statements(e))
+print("inserts_event", len(c.insert_statements(e, c.EVENT_TABLE)))
+print("broadcasts", len(e.broadcasts), e.broadcasts[0]["channel"] if e.broadcasts else None)
+print("read", c.read(tenant_id=7, session_id=22))
+
+e.seed_state(7, 22, "e9", '{"hp":1}', state_version=3)
+r2 = c.apply(tenant_id=7, world_id=11, session_id=22, event_type="unit.move",
+             payload={"dx": 2}, state_updates=[{"entity_id": "e9", "state": {"hp": 5}}],
+             client_event_id="ev-2", actor_id="u2", base_version=3)
+print("R2", r2)
+print("state row", e.query("SELECT * FROM pbl_entity_state WHERE entity_id='e9'"))
+print("stmt counts r1/r2", r["stmt_count"], r2["stmt_count"])
+
+r3 = c.apply(tenant_id=7, world_id=11, session_id=22, event_type="unit.move",
+             payload={"dx": 2}, state_updates=[{"entity_id": "e9", "state": {"hp": 9}}],
+             client_event_id="ev-2", actor_id="u2")
+print("R3 dedup", r3)
+print("counts after dedup", e.count(c.EVENT_TABLE), e.count(c.STATE_TABLE))
+print("trace", c.trace_kinds(e))
+print("broadcasts n", len(e.broadcasts))
+
+try:
+    c.apply(tenant_id=7, world_id=11, session_id=22, event_type="unit.move",
+            payload={"dx": 3}, state_updates=[{"entity_id": "e9", "state": {"hp": 99}}],
+            client_event_id="ev-4", base_version=1)
+except Exception as exc:
+    print("CONFLICT", type(exc).__name__, getattr(exc, "code", None), str(exc)[:140])
+print("trace tail", c.trace_kinds(e)[-4:])
+print("counts after conflict", e.count(c.EVENT_TABLE), e.count(c.STATE_TABLE))
+print("state after conflict", e.query("SELECT state_version FROM pbl_entity_state WHERE entity_id='e9'"))
+
+r5 = c.apply(tenant_id=7, world_id=11, session_id=22, event_type="snap",
+             payload={}, state_updates=[], client_event_id="ev-5",
+             snapshot={"reason": "reconnect", "entities": {"e9": {"hp": 5}}})
+print("R5", {k: r5[k] for k in ("ok", "seq", "state_rows", "stmt_count", "channel")})
+print("snap count", e.count(c.SNAPSHOT_TABLE))
+
+try:
+    c.apply(tenant_id=None, world_id=11, session_id=22, event_type="x")
+except Exception as exc:
+    print("TENANT", type(exc).__name__, getattr(exc, "code", None))
+try:
+    c.apply(tenant_id=7, world_id=None, session_id=22, event_type="x")
+except Exception as exc:
+    print("PARAM", type(exc).__name__, getattr(exc, "code", None))
+try:
+    c.apply(tenant_id=7, world_id=11, session_id=22, event_type="x", state_updates="no")
+except Exception as exc:
+    print("PARAM2", type(exc).__name__, getattr(exc, "code", None))
+try:
+    c.apply(tenant_id=7, world_id=11, session_id=22, event_type="x",
+            state_updates=[{"state": {"a": 1}}])
+except Exception as exc:
+    print("PARAM3", type(exc).__name__, getattr(exc, "code", None))
+try:
+    c.apply(tenant_id=7, world_id=11, session_id=22, event_type="x",
+            state_updates=[{"entity_id": "e1"}])
+except Exception as exc:
+    print("PARAM4", type(exc).__name__, getattr(exc, "code", None))
+print("trace after validation", c.trace_kinds(e)[-3:])
+
+try:
+    c.build_row(c.EVENT_TABLE, {"no_such_col": 1})
+except Exception as exc:
+    print("UNKNOWN", getattr(exc, "code", None), str(exc)[:90])
+try:
+    c.build_row(c.STATE_TABLE, {"tenant_id": "t1"})
+except Exception as exc:
+    print("MISSING", getattr(exc, "code", None), str(exc)[:140])
+try:
+    c.build_row(c.STATE_TABLE, {"state_json": "{}", "created_at": "x"}, strict=True, full_row=False)
+except Exception as exc:
+    print("IMMUTABLE", getattr(exc, "code", None), str(exc)[:140])
+try:
+    c.assert_append_only("UPDATE", c.EVENT_TABLE)
+except Exception as exc:
+    print("APPEND", getattr(exc, "code", None), str(exc)[:90])
+try:
+    c.assert_append_only("DELETE", "world")
+except Exception as exc:
+    print("BASE", getattr(exc, "code", None), str(exc)[:90])
+print("percentile empty", c.percentile([], 99), "single", c.percentile([5], 99),
+      "range99", c.percentile(list(range(100)), 99))
+print("ERR codes", c.ERR_STATE_CONFLICT, c.ERR_APPEND_ONLY, c.ERR_UNKNOWN_COLUMN,
+      c.ERR_MISSING_NOT_NULL, c.ERR_IMMUTABLE_COLUMN, c.ERR_TENANT_MISSING, c.ERR_BAD_PARAM,
+      c.ERR_BROADCAST_AFTER_COMMIT)
+print("tables", c.EVENT_TABLE, c.STATE_TABLE, c.SNAPSHOT_TABLE)
+c.uninstall()
+print("OK DONE")