What actually defines a thread
- The channel: text, email and chat threads are separate by nature.
- The external identity: the number or address on the other end.
- The internal owner: who is accountable for replying.
- The linked record: lead, customer, job or none yet.
- The last activity time, which drives ordering and follow-up.
Why identity matching is harder than it looks
A phone number is a strong identifier because it is exact and normalisable — strip formatting, compare the last ten digits, and you either match or you do not. An email address is similar. Names are weak: two Smiths, a misspelling, or a spouse calling on behalf of the account holder all break name matching.
The honest design is a confidence ladder. Exact identifier match links automatically. Everything else is offered as a suggestion for a human to confirm. A system that silently merges two customers because the names looked similar creates a data problem far worse than an unlinked thread.
One person, many identities
Households and small businesses routinely use several numbers and addresses. The right model is that a contact can accumulate identities over time, not that every new number is a new person. When a second number appears, the practical move is to link it to the existing contact once a human confirms it, and to keep both threads visible under that contact.
Cross-channel merging — folding a text thread and an email thread into one continuous conversation — is a different and much stronger claim. Unless a system explicitly says it does that, assume threads stay per channel.