Identity

Names are keys, so two spellings of one name are two people until something says otherwise, and an opaque platform id is nobody. Identity is a dictionary and stays one — hash lookups at ingest, no model on the per-line path.

Layers

1. Contacts. The address book loads into a dict (+19175551234 → Jordan) and resolves every inbound message before anything expensive runs. Contacts outrank everything below: a model guess cannot rename an address-book card, and two separate cards stay two people.
2. Stable platform ids. GroupMe and chat systems hand out opaque user ids; the display names are the unstable part and get ignored.
3. Explicit naming. memcal who covers the rest:

memcal who              # unnamed handles, assumed merges, open doubts
memcal who 12 "Jordan"  # name one by hand
memcal who --adopt      # take every name a platform already gave — free
memcal who --resolve    # one model call over the whole picture
memcal who --split 3    # undo an assumed merge, handle for handle
memcal who --confirm 3  # accept a merge, or act on a doubt

--resolve is the only step that costs anything: it sends every unnamed handle and every known person in one request, so a handle is matched against the whole roster rather than judged alone.

Assumed, not decided

What the model concludes is provisional: merges take effect immediately, are listed by number, and are reversible. It can also decline to decide, which records a question rather than a guess. "Alex" alone never resolves when two Alexes exist; "Alex" plus poker and "Alex" plus work resolve differently, from evidence.