Description:
After upgrading from MySQL Workbench 8.0.x to 26.7.0, connections to pre-8.3 servers never open. The UI shows "Starting editor session..." with a spinner indefinitely and no error is displayed.
The connection itself succeeds. Immediately afterward, Workbench runs SET SESSION explain_json_format_version=2. That variable does not exist on servers older than 8.3, the statement fails with Error 1193, the service session thread exits, and the UI never recovers.
From mysqlsh.log:
Info: Shell.open_session: tid=0: CONNECTED: <host>:3306
Info: ClassicSession.run_sql: tid=75875: MySQL Error 1193 (HY000): Unknown system variable 'explain_json_format_version', SQL: SET SESSION explain_json_format_version=2
Error: [MSG] Thread ServiceSession-... exiting with code MySQL Error (1193): Unknown system variable 'explain_json_format_version'
Workbench: 26.7.0 (ba08183), MySQL Shell 26.7.1, libmysqlclient 26.7.0, macos15/arm64.
Server: MySQL 8.0 (pre-8.3). Connection uses SSL with ssl-mode=VERIFY_CA and client certificates.
How to repeat:
1. Install MySQL Workbench 26.7.0.
2. Create a connection to a MySQL 8.0 server.
3. Open the connection.
4. The UI hangs on "Starting editor session..."; mysqlsh.log shows Error 1193 for explain_json_format_version.
Suggested fix:
Only set explain_json_format_version when the server version is 8.3 or later, or treat a failure of that statement as a warning rather than fatal. If pre-8.3 servers are no longer supported, report that clearly in the UI instead of hanging.
