v4.2.0

chdb 4.2.0

Requires chdb-core>=26.5.0.

New

• chdb.agents.ChDBTool (beta/experimental) — the canonical Python agent tool for chDB, and the reference implementation of a cross-language contract (chdb/agents/CONTRACT.md). Query + introspection with engine-enforced read-only (readonly=2, keeps file()/s3()/url() usable), server-side parameter binding, result caps with an explicit truncated flag, error-to-model dispatch, optional query timeout, attach_file, an optional file allowlist, and a Python-only dataframe_query over Python(). A shared conformance fixture keeps other-language bindings in lock-step. The API is beta and may change in a minor release — pin a version if you depend on it.
• DataStore → ClickHouse writeback — to_clickhouse writes an in-memory DataFrame to a ClickHouse server (same- and cross-server).
• DataStore pandas 3.x — pd.col() expressions; lazy metadata (.columns/.dtypes/.shape/.index resolved without materializing).
• DataStore ergonomics — output_format="DataStore" dispatch and mirrored UDF surfaces from chdb-core.

Notes

All additions are backward-compatible. See the merged PRs since v4.1.9 (#561, #568, #570, #584, #591, #592, #594, #597).