There is a critical issue here that will lead to an IndexError and a crash.

The compact_ids are generated based on the length of self._chunk_token_hash. The remove_chunks method evicts entries by setting them to None in this list, but it never reclaims the space or allows compact_ids to be reused.

As a result, len(self._chunk_token_hash) grows without bound. Since self._compact_id_to_slot has a fixed size of _TABLE_SIZE, this will inevitably cause an IndexError here when a cid is generated that is >= _TABLE_SIZE. This also constitutes a memory leak, as the list will fill with None values that are never removed.

To fix this, you should implement a mechanism to reuse compact_ids. A common pattern is to maintain a free list of evicted IDs. When registering new chunks, you can pull from this free list before generating a new ID by increasing the size of _chunk_token_hash.

The current implementation does not handle the case where the same token_hash is registered for multiple different chunks. This can lead to incorrect behavior and orphaned entries in the matcher.

If a token_hash is reused, the reverse-lookup maps (_token_hash_to_start and _token_hash_to_compact_id) are overwritten with the details of the latest registration. This can cause several problems:

• remove_chunks will only be able to evict the most recently registered chunk for a given hash, leaving earlier chunks with the same hash as orphans in the table.
• match_sub_sequence could return incorrect old_st positions for these orphaned chunks if they are matched, leading to data corruption downstream.

To ensure correctness, you should enforce that all registered token_hash values are unique. A straightforward way to enforce this is to check for existing hashes before registration and raise an error. This makes the requirement on the caller explicit.

        # Check for duplicates before modifying state
        for th in token_hashes:
            if th in self._token_hash_to_compact_id:
                raise ValueError(f"Attempted to register duplicate token hash: {th.hex()}")

        # Persist compact_id → token_hash, token_hash → start, and reverse maps
        for i in range(n):
            th = token_hashes[i]
            cid = int(compact_ids[i])
            slot = int(chunk_hashes[i]) & int(self._mask)
            self._chunk_token_hash.append(th)
            self._token_hash_to_start[th] = i * self.chunk_size
            self._compact_id_to_slot[cid] = slot
            self._token_hash_to_compact_id[th] = cid