Function flush_pty_batch 

fn flush_pty_batch(
    broker: &Broker,
    block_id: &str,
    data: &[u8],
    osc_events: &[OscEvent],
    filestore: Option<&Arc<FileStore>>,
    line_buf: &mut Vec<u8>,
    translator: Option<&mut ClaudeTranslator>,
)

Do the actual per-batch work the read loop used to do per-read: write through to the FileStore, broadcast the raw bytes, publish any OSC activity, and (for agent panes) feed the JSON-stream translator. Called once per coalesced batch instead of once per (up to 4KB) PTY read.