The durable process behind one browser session.

One DurableStash.Session exists per browser session; every LiveView of that session reads and writes through it. State is partitioned per view module, and the single-process actor model gives a total order over writes — per-key last-write-wins with no timestamps needed.

State shape (string keys — it round-trips through JSON object storage):

%{
  "views" => %{
    "Elixir.My.View" => %{"vsn" => 1, "data" => %{"key" => value}}
  },
  "last_seen_at" => unix_millis | nil
}

Each view slice carries the vsn its writer declared. A write with a different vsn replaces the slice wholesale instead of merging — the adapter only does that with a full, migrated key set, so a version bump can never mix old- and new-shape keys.

Every accepted write returns :sync, so durability is guaranteed before a deploy can take the node down. Writes are rare UI state; the immediate object-store PUT is the point, not a cost.