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Time: what held, and what mem7 believed

Since 03/10/2026 (mem7 0.8), every memory is a series of versions with two time axes:

Axis Columns Question it answers
Valid time valid_from, valid_to When did this hold in the world?
Transaction time tx_from, tx_to When did mem7 believe it?

A plain memory store/read works as before: a fact holds from the moment it is written, and reads return what mem7 believes now of what holds now.

Writing

memory_store takes two optional arguments, a date (2026-03-20, midnight UTC) or an RFC3339 time:

  • valid_from: when the fact starts to hold. In the past, it corrects history.
  • valid_to: when it stops holding.

A new version ends the versions it overlaps, and keeps what they said outside its own period:

2026-02-15  store event7:host "Railway"                      Railway    [02-15, …)
2026-03-20  store event7:host "Cloudflare"                   Railway    [02-15, 03-20)  Cloudflare [03-20, …)
2026-04-12  store event7:host "local only" valid_from=04-05  … Cloudflare [03-20, 04-05)  local only [04-05, …)

The last line is a correction of the past: what mem7 believed on 04-11 (Cloudflare until today) is no longer believed, but is still readable as_of that day.

memory_forget stops believing a key but does not erase the past, so a read as_of an earlier moment still sees it.

Reading

memory_recall, memory_search, memory_context and memory_list take:

  • valid_at: what held at that moment ("where was event7 on March 1st?")
  • as_of: what mem7 believed at that moment ("what did we know on April 11th?")

Used together, they give what mem7 believed on one day about another. A version with an explicit validity shows a Valid: from → to line (recall, search) or valid_from / valid_to / tx_from / tx_to fields (context); memory_history lists each write with the validity it declared.

Storage

The markdown workspace stays the source of truth: a store entry carries valid_from / valid_to when the caller gave them, under the hash chain. The index keeps every version. An index built before versions (one row per key) is rebuilt from the markdown when mem7 starts, keeping embeddings.

Out of scope for now: detecting that two different keys contradict each other.