Recent changes in asyncmy break MariaDB MCP

Recent commits in asyncmy (https://github.com/long2ice/asyncmy/commits/main) have changed internal connection fields accessed by MariaDB MCP. The MCP server starts up, but any tool call generates the following exception:

ERROR - Unexpected error during query execution (Connection: not acquired): 'SafeConnection' object has no attribute '_reader'
Traceback (most recent call last):
  File "/home/user/mariadb-mcp/src/server.py", line 259, in _execute_query
    async with self.pool.acquire() as conn:
  File "/home/user/mariadb-mcp/.venv/lib/python3.11/site-packages/asyncmy/contexts.py", line 75, in __aenter__
    self._conn = await self._coro
                 ^^^^^^^^^^^^^^^^
  File "asyncmy/pool.pyx", line 118, in _acquire
  File "asyncmy/pool.pyx", line 120, in asyncmy.pool.Pool._acquire
  File "/home/user/mariadb-mcp/src/custom_connection.py", line 72, in fill_free_pool
    if conn._reader.at_eof() or conn._reader.exception():
       ^^^^^^^^^^^^
AttributeError: 'SafeConnection' object has no attribute '_reader'
2026-08-07 12:07:48,816 - config - ERROR - TOOL ERROR: list_databases failed: An unexpected error occurred: 'SafeConnection' object has no attribute '_reader'
Traceback (most recent call last):
  File "/home/user/mariadb-mcp/src/server.py", line 259, in _execute_query
    async with self.pool.acquire() as conn:
  File "/home/user/mariadb-mcp/.venv/lib/python3.11/site-packages/asyncmy/contexts.py", line 75, in __aenter__
    self._conn = await self._coro
                 ^^^^^^^^^^^^^^^^
  File "asyncmy/pool.pyx", line 118, in _acquire
  File "asyncmy/pool.pyx", line 120, in asyncmy.pool.Pool._acquire
  File "/home/user/mariadb-mcp/src/custom_connection.py", line 72, in fill_free_pool
    if conn._reader.at_eof() or conn._reader.exception():
       ^^^^^^^^^^^^
AttributeError: 'SafeConnection' object has no attribute '_reader'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/user/mariadb-mcp/src/server.py", line 379, in list_databases
    results = await self._execute_query(sql)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/mariadb-mcp/src/server.py", line 295, in _execute_query
    raise RuntimeError(f"An unexpected error occurred: {e}") from e

I can confirm that downgrading asyncmy to 0.2.11 "solves" the problem, so the issue must be caused by recent changes to asyncmy.

Start in src/custom_connection.py at fill_free_pool, especially the access to conn._reader, and compare that assumption with the recent asyncmy connection changes. Reproduce the failure through a database tool such as list_databases and verify that pool acquisition and tool calls work with the affected asyncmy version without the AttributeError.