Function sequence_model_at 

pub fn sequence_model_at(
    text: &str,
    offset: usize,
    info: Option<&ContextSequenceInfo>,
) -> Option<SequenceModel>

Locate the Handler enclosing offset in text and build its sequence model. info is the owning unit’s cross-context/agent table — None degrades classification to capabilities only (still correct; just unable to recognise agent/cross-context lifelines), which happens for a unit sequence_info has no entry for (a commons file, or one this round never reached because the pipeline bailed before it).