Read the current value of a checkpoint by key. Returns the latest stored JSON value, its version, and update timestamp. Returns {"status": "not_found"} if key doesn't exist.

Atomically write a checkpoint with optional version guard. Pass expected_version from a prior get_state call. expected_version=0 → create-only (fails if key exists). expected_version=N → update only if stored version matches (conflict-safe). Omit expected_version or pass -1 → unconditional write. Use force_set_state for simpler unconditional writes.

Unconditionally write a checkpoint value. Always succeeds. Prefer for single-writer workflows. For concurrent writers, use set_state with expected_version.

List checkpoint keys matching a pattern (SQL LIKE syntax). Pass '%' or omit for all keys. Returns key, version, and updated_at for each match.

Remove a checkpoint key and its value permanently.