Streaming Model

Append-Only Streams

• Backed by a persistent builder
• append(...) -> id, flush(), flush_pyg(), reset()
• No update/remove

Mutable Streams

• Maintain ID-addressable cache entries
• Support append, update, remove, optional removed-slot reuse
• Flush merges cached single-graph encodings into one batch

Output Contract

Both stream categories follow the same native-first rule:

• flush() returns native BatchEncoding
• flush_pyg() returns PyG convenience output