diff --git a/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb/Internal/LocalDbSchema.cs b/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb/Internal/LocalDbSchema.cs
new file mode 100644
index 0000000..b0b5528
--- /dev/null
+++ b/ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb/Internal/LocalDbSchema.cs
@@ -0,0 +1,105 @@
+using Microsoft.Data.Sqlite;
+
+namespace ZB.MOM.WW.LocalDb.Internal;
+
+/// <summary>
+/// Creates/migrates the library's own bookkeeping tables. Idempotent; runs in one transaction.
+/// </summary>
+internal static class LocalDbSchema
+{
+    private const string Ddl = """
+        CREATE TABLE IF NOT EXISTS __localdb_meta (
+          id INTEGER PRIMARY KEY CHECK (id = 1),
+          node_id TEXT NOT NULL,
+          hlc_high_water INTEGER NOT NULL DEFAULT 0,
+          schema_version INTEGER NOT NULL
+        );
+        CREATE TABLE IF NOT EXISTS __localdb_oplog (
+          seq INTEGER PRIMARY KEY AUTOINCREMENT,
+          table_name TEXT NOT NULL,
+          pk_json TEXT NOT NULL,
+          row_json TEXT NULL,
+          hlc INTEGER NOT NULL,
+          node_id TEXT NOT NULL,
+          is_tombstone INTEGER NOT NULL DEFAULT 0
+        );
+        CREATE INDEX IF NOT EXISTS __localdb_oplog_hlc ON __localdb_oplog(table_name, pk_json, hlc);
+        CREATE TABLE IF NOT EXISTS __localdb_peer_state (
+          id INTEGER PRIMARY KEY CHECK (id = 1),
+          peer_node_id TEXT NULL,
+          last_acked_seq INTEGER NOT NULL DEFAULT 0,
+          last_applied_remote_seq INTEGER NOT NULL DEFAULT 0,
+          last_seen_hlc INTEGER NOT NULL DEFAULT 0,
+          needs_snapshot INTEGER NOT NULL DEFAULT 0,
+          last_sync_utc TEXT NULL
+        );
+        -- WITHOUT ROWID: the (table_name, pk_json) key IS the lookup path for every LWW conflict compare.
+        CREATE TABLE IF NOT EXISTS __localdb_row_version (
+          table_name TEXT NOT NULL,
+          pk_json TEXT NOT NULL,
+          hlc INTEGER NOT NULL,
+          node_id TEXT NOT NULL,
+          is_tombstone INTEGER NOT NULL DEFAULT 0,
+          tombstone_utc TEXT NULL,
+          PRIMARY KEY (table_name, pk_json)
+        ) WITHOUT ROWID;
+        -- Single-row DB-scoped guard the applier toggles inside its txn so capture triggers skip replicated applies.
+        CREATE TABLE IF NOT EXISTS __localdb_applying (
+          id INTEGER PRIMARY KEY CHECK (id = 1),
+          applying INTEGER NOT NULL DEFAULT 0
+        );
+        CREATE TABLE IF NOT EXISTS __localdb_dead_letter (
+          id INTEGER PRIMARY KEY AUTOINCREMENT,
+          received_utc TEXT NOT NULL,
+          table_name TEXT NOT NULL,
+          pk_json TEXT NOT NULL,
+          row_json TEXT NULL,
+          hlc INTEGER NOT NULL,
+          node_id TEXT NOT NULL,
+          error TEXT NOT NULL
+        );
+        INSERT INTO __localdb_applying (id, applying) SELECT 1, 0 WHERE NOT EXISTS (SELECT 1 FROM __localdb_applying);
+        INSERT INTO __localdb_peer_state (id) SELECT 1 WHERE NOT EXISTS (SELECT 1 FROM __localdb_peer_state);
+        """;
+
+    public static void EnsureCreated(SqliteConnection connection)
+    {
+        using var transaction = connection.BeginTransaction();
+
+        using (var ddl = connection.CreateCommand())
+        {
+            ddl.Transaction = transaction;
+            ddl.CommandText = Ddl;
+            ddl.ExecuteNonQuery();
+        }
+
+        using (var meta = connection.CreateCommand())
+        {
+            meta.Transaction = transaction;
+            meta.CommandText =
+                "INSERT INTO __localdb_meta (id, node_id, schema_version) " +
+                "SELECT 1, $nodeId, 1 WHERE NOT EXISTS (SELECT 1 FROM __localdb_meta)";
+            meta.Parameters.AddWithValue("$nodeId", Guid.NewGuid().ToString("D"));
+            meta.ExecuteNonQuery();
+        }
+
+        transaction.Commit();
+    }
+
+    internal static (string NodeId, long HlcHighWater) ReadMeta(SqliteConnection connection)
+    {
+        using var cmd = connection.CreateCommand();
+        cmd.CommandText = "SELECT node_id, hlc_high_water FROM __localdb_meta WHERE id = 1";
+        using var reader = cmd.ExecuteReader();
+        reader.Read();
+        return (reader.GetString(0), reader.GetInt64(1));
+    }
+
+    internal static void FlushHlcHighWater(SqliteConnection connection, long value)
+    {
+        using var cmd = connection.CreateCommand();
+        cmd.CommandText = "UPDATE __localdb_meta SET hlc_high_water = $value WHERE id = 1";
+        cmd.Parameters.AddWithValue("$value", value);
+        cmd.ExecuteNonQuery();
+    }
+}
diff --git a/ZB.MOM.WW.LocalDb/tests/ZB.MOM.WW.LocalDb.Tests/LocalDbSchemaTests.cs b/ZB.MOM.WW.LocalDb/tests/ZB.MOM.WW.LocalDb.Tests/LocalDbSchemaTests.cs
new file mode 100644
index 0000000..55598e8
--- /dev/null
+++ b/ZB.MOM.WW.LocalDb/tests/ZB.MOM.WW.LocalDb.Tests/LocalDbSchemaTests.cs
@@ -0,0 +1,123 @@
+using Microsoft.Data.Sqlite;
+using ZB.MOM.WW.LocalDb.Internal;
+
+namespace ZB.MOM.WW.LocalDb.Tests;
+
+public sealed class LocalDbSchemaTests : IDisposable
+{
+    private readonly string _path = Path.Combine(Path.GetTempPath(), Guid.NewGuid() + ".db");
+
+    public void Dispose()
+    {
+        SqliteConnection.ClearAllPools();
+        if (File.Exists(_path))
+            File.Delete(_path);
+    }
+
+    private SqliteConnection Open()
+    {
+        var conn = new SqliteConnection($"Data Source={_path}");
+        conn.Open();
+        return conn;
+    }
+
+    private static long ScalarLong(SqliteConnection conn, string sql)
+    {
+        using var cmd = conn.CreateCommand();
+        cmd.CommandText = sql;
+        return Convert.ToInt64(cmd.ExecuteScalar());
+    }
+
+    private static string ScalarString(SqliteConnection conn, string sql)
+    {
+        using var cmd = conn.CreateCommand();
+        cmd.CommandText = sql;
+        return (string)cmd.ExecuteScalar()!;
+    }
+
+    [Fact]
+    public void EnsureCreated_CreatesAllObjects()
+    {
+        using var conn = Open();
+        LocalDbSchema.EnsureCreated(conn);
+
+        using var cmd = conn.CreateCommand();
+        cmd.CommandText = "SELECT name FROM sqlite_master WHERE type='table'";
+        var tables = new List<string>();
+        using (var reader = cmd.ExecuteReader())
+            while (reader.Read())
+                tables.Add(reader.GetString(0));
+
+        foreach (var expected in new[]
+                 {
+                     "__localdb_meta", "__localdb_oplog", "__localdb_peer_state",
+                     "__localdb_row_version", "__localdb_applying", "__localdb_dead_letter"
+                 })
+            Assert.Contains(expected, tables);
+    }
+
+    [Fact]
+    public void EnsureCreated_IsIdempotent()
+    {
+        using var conn = Open();
+        LocalDbSchema.EnsureCreated(conn);
+        LocalDbSchema.EnsureCreated(conn);
+
+        Assert.Equal(1, ScalarLong(conn, "SELECT COUNT(*) FROM __localdb_meta"));
+        Assert.Equal(1, ScalarLong(conn, "SELECT COUNT(*) FROM __localdb_applying"));
+        Assert.Equal(1, ScalarLong(conn, "SELECT COUNT(*) FROM __localdb_peer_state"));
+    }
+
+    [Fact]
+    public void Meta_NodeId_MintedOnceAndStable()
+    {
+        string first;
+        using (var conn = Open())
+        {
+            LocalDbSchema.EnsureCreated(conn);
+            first = ScalarString(conn, "SELECT node_id FROM __localdb_meta WHERE id=1");
+        }
+
+        using (var conn = Open())
+        {
+            LocalDbSchema.EnsureCreated(conn);
+            var second = ScalarString(conn, "SELECT node_id FROM __localdb_meta WHERE id=1");
+            Assert.Equal(first, second);
+        }
+
+        Assert.True(Guid.TryParse(first, out _));
+    }
+
+    [Fact]
+    public void Applying_SeededWithZeroRow()
+    {
+        using var conn = Open();
+        LocalDbSchema.EnsureCreated(conn);
+
+        Assert.Equal(0, ScalarLong(conn, "SELECT applying FROM __localdb_applying WHERE id=1"));
+    }
+
+    [Fact]
+    public void ReadMeta_ReturnsNodeIdAndHighWater()
+    {
+        using var conn = Open();
+        LocalDbSchema.EnsureCreated(conn);
+
+        var (nodeId, highWater) = LocalDbSchema.ReadMeta(conn);
+
+        Assert.True(Guid.TryParse(nodeId, out _));
+        Assert.Equal(0, highWater);
+    }
+
+    [Fact]
+    public void FlushHlcHighWater_RoundTrips()
+    {
+        using var conn = Open();
+        LocalDbSchema.EnsureCreated(conn);
+
+        LocalDbSchema.FlushHlcHighWater(conn, 123_456_789L);
+
+        var (_, highWater) = LocalDbSchema.ReadMeta(conn);
+        Assert.Equal(123_456_789L, highWater);
+    }
+}