diff --git a/libraries/liblmdb/Doxyfile b/libraries/liblmdb/Doxyfile
index 8c577f83db..22fd690aab 100644
--- a/libraries/liblmdb/Doxyfile
+++ b/libraries/liblmdb/Doxyfile
@@ -576,7 +576,7 @@ WARN_LOGFILE           =
 # directories like "/usr/src/myproject". Separate the files or directories
 # with spaces.
 
-INPUT                  = lmdb.h midl.h mdb.c midl.c module.c intro.doc
+INPUT                  = lmdb.h midl.h mdb.c midl.c module.c intro.doc upgrading.doc
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding, which is
diff --git a/libraries/liblmdb/lmdb.h b/libraries/liblmdb/lmdb.h
index 0fb30528c3..df072d1669 100644
--- a/libraries/liblmdb/lmdb.h
+++ b/libraries/liblmdb/lmdb.h
@@ -15,6 +15,8 @@
  *	database integrity cannot be corrupted by stray pointer writes from
  *	application code.
  *
+ *	<B>See @ref upgrading if you used LMDB 0.9 previously.</b>
+ *
  *	The library is fully thread-aware and supports concurrent read/write
  *	access from multiple processes and threads. Data pages use a copy-on-
  *	write strategy so no active data pages are ever overwritten, which
diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 57d5ddfe10..e159c10886 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -3373,7 +3373,6 @@ mdb_txn_renew0(MDB_txn *txn)
 #endif
 		txn->mt_child = NULL;
 		txn->mt_rdonly_child_count = 0;
-		pthread_mutex_init(&txn->mt_child_mutex, NULL);
 		txn->mt_loose_pgs = NULL;
 		txn->mt_loose_count = 0;
 		if (env->me_flags & MDB_WRITEMAP) {
@@ -3560,6 +3559,7 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
 				return ENOMEM;
 			}
 			txn->mt_u.dirty_list[0].mid = 0;
+			pthread_mutex_init(&txn->mt_child_mutex, NULL);
 		}
 		txn->mt_txnid = parent->mt_txnid;
 		txn->mt_dirty_room = parent->mt_dirty_room;
@@ -6388,6 +6388,7 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode
 #endif
 				txn->mt_dbxs = env->me_dbxs;
 				txn->mt_flags = MDB_TXN_FINISHED;
+				pthread_mutex_init(&txn->mt_child_mutex, NULL);
 				env->me_txn0 = txn;
 			} else {
 				rc = ENOMEM;
@@ -6439,7 +6440,10 @@ mdb_env_close_active(MDB_env *env, int excl)
 	}
 	}
 #endif
-	free(env->me_txn0);
+	if (env->me_txn0) {
+		pthread_mutex_destroy(&env->me_txn0->mt_child_mutex);
+		free(env->me_txn0);
+	}
 	mdb_midl_free(env->me_free_pgs);
 
 	if (env->me_flags & MDB_ENV_TXKEY) {
diff --git a/libraries/liblmdb/upgrading.doc b/libraries/liblmdb/upgrading.doc
new file mode 100644
index 0000000000..c7f8d936d8
--- /dev/null
+++ b/libraries/liblmdb/upgrading.doc
@@ -0,0 +1,104 @@
+/*
+ * Copyright 2026 Howard Chu, Symas Corp.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+/** @page upgrading Upgrading From Release 0.9
+
+The on-disk file format has changed in LMDB 1.0 and versions 0.9
+and 1.0 are mutually incompatible. You must use v0.9 #mdb_dump
+to export your old DBs, and import with v1.0 #mdb_load if you
+want to migrate your existing data to use LMDB 1.0. There is
+no support in LMDB 1.0 for operating directly on v0.9 DB files.
+Including such support would only bloat the library so it will
+not be done.
+
+@section features New Features
+
+New features in LMDB 1.0 include:
+	\li support for incremental backup
+	\li support for page-level checksums and encryption
+	\li support for DB on raw block devices
+	\li support for 2-phase commit
+	\li support for page sizes up to 64KB
+
+plus other minor additions to the API.
+
+@subsection backup Incremental Backup
+
+One of the changes to the disk format is the addition of the
+txnID to the page headers. This means every page now explicitly
+identifies which txn wrote it. The incremental backup function
+utilizes this feature and copies only pages with txnIDs newer
+than a given value. The <a href="man1/mdb_dump_1.html">mdb_dump</a>
+and <a href="man1/mdb_load_1.html">mdb_load</a> tools can be used
+to invoke this feature from the commandline. The #mdb_env_incr_dumpfd()
+and #mdb_env_incr_loadfd() functions can be used to perform an
+incremental backup or restore programmatically.
+
+@subsection encryption Page-Level Checksums and Encryption
+
+Page-level checksums and/or encryption can be enabled, to allow
+detection of corruption or tampering in the data, or to provide
+encryption-at-rest. These features can be enabled independently
+or together, using #mdb_env_set_checksum() and #mdb_env_set_encrypt().
+Simple checksumming can be used to detect corrupted data storage.
+The checksum support also allows for an optional key, for use
+with keyed hashes (e.g. HMAC) for protection against malicious
+tampering. The encryption support can use basic ciphers for
+simple encryption, or authenticated encryption mechanisms for
+encryption with built in integrity protection. The page number
+and txnID are used as the initialization vector (IV) for ciphers
+which need them.
+
+While the above two functions can be used directly on an environment,
+there is a dynamic module interface that's the preferred mechanism,
+because it will allow the command line tools to operate on encrypted
+environments as well. @ref crypto 
+An example of how to use the module interface
+is provided in crypto.c in the LMDB source.
+
+@subsection blockdev Raw Block Devices
+
+On Linux and other systems that support mmap on block devices,
+LMDB can be used directly on these devices, avoiding the overhead
+of any filesystem. Many modern filesystems now use copy-on-write
+mechanisms, just like LMDB, and it is redundant to do this in
+both the DB and the filesystem. Using the raw block device means
+that writes are always synchronous, so there is no need to do
+any fsyncs when committing a transaction. LMDB support for
+block devices is implicit; if you specify a block device as the
+path in mdb_env_open() LMDB will just do the right thing. It
+will act as if #MDB_NOSUBDIR was specified, and the lockfile it
+creates will just be the pathname with "-lock" appended.
+
+@subsection twophase Two Phase Commit
+
+Supporting two-phase commit (2PC) allows LMDB to be integrated
+with distributed transaction coordinators. The new function
+mdb_txn_prepare() is used to prepare a transaction, which then
+can be finalized with mdb_txn_commit() (as usual). In the rare
+case where a transaction was successfully committed but needs
+to be rolled back due to failures elsewhere in a distributed
+system, mdb_env_rollback() may be used. In LMDB, preparing a
+transaction just means writing all of the transaction's data
+except for the final metapage update, which is still just done
+in the final commit.
+
+@subsection pagesize Larger Page Sizes
+
+The page size LMDB uses can now be set explicitly, instead of
+just using the OS's page size. While Linux still defaults to
+4KB pages, larger pages may yield better performance, depending
+on the data being stored. Also, e.g. Apple Silicon machines use
+16KB pages by default. Page sizes up to 64KB are supported, and
+can be set using mdb_env_set_pagesize().
+
+*/