Configuration — the history block

The block lives next to the core options in the adapter's configuration (indexnowkit.history in the bundle, 'history' => [...] in config/indexnow.php, 'history' => [...] of the Yii2 component); HistoryConfig::OPTIONS lists its keys in dotted form and the adapters add them to the keys they accept. In plain PHP the stores are constructed directly (new PdoSubmissionStore($pdo), new Psr16SubmissionStore($cache, $prefix, $limit)).

Key	Default	Meaning
history.store	null	null: nothing is recorded (Submission\NullSubmissionStore). psr16: a ring buffer in the cache behind debounce.store. pdo: a database table.
history.limit	500	Records the psr16 ring buffer keeps; the oldest is overwritten.
history.key_prefix	debounce.key_prefix	Cache key prefix of the psr16 store (<prefix>history.index, <prefix>history.<n>); no {}()/\@:.
history.pdo.service	null	Which connection of the adapter gives the PDO: the bundle's doctrine.dbal.<name>_connection (default connection when null), a Laravel connection name (DB::connection(name)), a Yii2 db component id.
history.pdo.dsn	null	A PDO DSN when the history has its own database (sqlite:var/indexnow.sqlite, mysql:host=…;dbname=…); ignored when pdo.service resolves. Credentials go in the adapter's own PDO options, not here.
history.pdo.table	indexnow_submissions	The table; [A-Za-z_][A-Za-z0-9_]* — it is the one identifier that reaches SQL from the configuration. Create it with migrations.md.
history.retention_days	90	What indexnow:history --purge removes beyond.

An invalid block is one critical log line and nothing is recorded (HistoryConfig::loadOrDisabled()); check prints the error (history.store).