What motivated you to submit this feature request?
We need a reliable way to verify whether recent write operations are visible to queries. The use of vector count comparison fails when insert/delete operations offset each other (e.g., inserting 5 and deleting 5 documents leaves the count unchanged). An LSN in index statistics would provide more robust verification of freshness.

Describe the solution you'd like
Expose the index lsn (x-pinecone-max-indexed-lsn) in describe_index_stats()

Describe alternatives you've considered
We currently use vector count comparison to detect ingestion freshness

write operations (upsert/delete) code:

# Store the count before write operation
initial_count = (
  index.describe_index_stats()
  .get("namespaces", {})
  .get(namespace, {})
  .get("vector_count", None)
)

index.upsert(...)  

Search code:

count = (
  index.describe_index_stats()
  .get("namespaces", {})
  .get(namespace, {})
  .get("vector_count", None)
)

if count == initial_count:
  LOGGER.warning(
      "Recently ingested documents may not yet be visible to queries "
      "due to Pinecone's indexing delay."
  )
  # Potentially followed by a sleep to await visibility.