“Together: write the letter to this friendship's future — and co-sign it.”

A set-piece. One table, two pens, the same evening, one joint artefact. These are the pages people photograph.

Why this question

Start with the one sentence you'd both want in it — the thing we want to make sure we never forget — and build from there.

And once you’ve both answered

Sign it, both of you, with the date. Read it again in ten years and report back.

Answering it honestly

One table, two pens, the same evening. This one doesn't work by correspondence.
Argue about the details out loud before anything gets written down. The arguing is part of the artefact.
Finish in the sitting. A half-built set-piece has a way of staying half-built.

And the house rule, whatever the mode: leave a blank rather than write a lie. A blank can be filled later; a lie sits in the archive forever, and you both have to live with the paperwork.