`CALL start_ui_server()` triggers extension download in DuckDB 1.5.0

[sanjukeshavan]

After upgrading the DuckDB JDBC client to 1.5.0.0, calling CALL start_ui_server() now attempts to automatically download the ui extension from the internet, resulting in a SQLException.

java.sql.SQLException: Extension Autoloading Error: An error occurred while trying to
automatically install the required extension 'ui':
Failed to download extension "ui" at URL
"http://extensions.duckdb.org/v1.5.0/osx_arm64/ui.duckdb_extension.gz"

Environment

• DuckDB JDBC 1.5.0.0
• macOS ARM64 (Apple Silicon)

Steps to Reproduce

1. Add DuckDB JDBC 1.5.0.0 as a dependency in a Java project
2. Create a DuckDB connection and execute CALL start_ui_server()
3. Observe that DuckDB attempts to download the ui extension from http://extensions.duckdb.org/v1.5.0/osx_arm64/ui.duckdb_extension.gz
4. Call fails with SQLException: Extension Autoloading Error

Note: The ui extension and start_ui_server() were introduced in DuckDB 1.1.0. In versions prior to 1.5.0.0, start_ui_server() worked without triggering an extension download from the internet.

Expected

CALL start_ui_server() should not silently trigger an extension download. If the ui extension is not installed, it should fail with a clear error indicating the extension is missing — not attempt a
network download.

Request

Please advise on how to invoke start_ui_server() without triggering an automatic extension download, or provide a way to pre-bundle the ui extension for offline environments.

[staticlibs]

Hi, thanks for the report! autoinstall_known_extensions option is true by default (reference), you need to set it to false if automatic download it undesired.

This can be done in connection Properties config or by appending ;autoinstall_known_extensions=FALSE to connection URL.

provide a way to pre-bundle the ui extension

Please contact MotherDuck for questions about ui extension, it is developed and maintained by them.

[sanjukeshavan]

Thanks @staticlibs , Just wanted to understand if autoinstall_known_extensions was set to true by default in new release? Because we were not facing this issue in previous version of duckdb-java (before 1.5.0.0).
Also, I stumble upon this similar issue which occurred before as well - duckdb/duckdb#16616

[staticlibs]

@sanjukeshavan

Just wanted to understand if autoinstall_known_extensions was set to true by default in new release?

No, this flag was always true for both JDBC and CLI, since 1.2 at least.