What this is
The same 2-of-3 setup as rung 4 — but one of the three keys is held by a collaborative-custody company (Unchained, Casa, Nunchuk, The Bitcoin Adviser, and others). They hold one key and help coordinate spending, recovery, and inheritance. They cannot move your funds — they only hold one of three, and you hold the other two. You keep unilateral control. What you outsource is complexity, not custody.
What it’s good at
- Much less to manage. Typically five items instead of seven — for many holders, the difference between “manageable” and “overwhelming.”
- Convenient spending. Sign with one key, ask the partner to co-sign; your second key stays untouched in its secure spot.
- A safety net. Lose a key and the partner can help you recover to a fresh setup — they can only help when asked, never spend alone.
- Inheritance gets dramatically simpler. Your heirs contact the partner, prove who they are, and get help — no PSBT wrangling.
What it costs you
- A partner is now in the loop. You’ve disclosed that you hold Bitcoin, and usually a rough amount — a privacy trade-off.
- Counterparty longevity. What if they go out of business? (See the sovereign-recovery note.)
- Ongoing cost. Free tiers exist, but assisted service runs hundreds to thousands per year for larger balances.
Sovereign recovery is the make-or-break test The one criterion that matters most when choosing a partner: can you still spend using your two keys plus the wallet descriptor if the partner vanishes tomorrow? Reputable partners publish open-source recovery tools that prove yes. Verify this before you commit — it’s the difference between a helper and a dependency.
Who should use it
Holders with substantial exposure who honestly recognise that they themselves are their own biggest risk — and who’d rather outsource complexity than build operational discipline from scratch. Especially attractive when your inheritance situation is non-trivial (substantial estate, multiple heirs, complex family), where the partner’s standing process adds real value.
Where the partners differ
Unchained White-glove partnership; documented inheritance protocols; attorney coordination.
Casa Multi-key architecture and tools first; lighter partner role.
Nunchuk Sovereignty and minimum trust; minimal disclosure (“don’t rely on us”).
The Bitcoin Adviser Estate-planning end; multisig as infrastructure for a broader inheritance plan.
None is “correct” — they serve different clients. Evaluate each on its sovereign-recovery story, multi-vendor hardware support, and exactly what happens to your setup if they disappear.
Planning for inheritance
This is the rung’s biggest strength. Your heirs contact the partner — who holds one key, the descriptor, and the expertise — prove their identity, and are walked through accessing one of your two keys. A far lower bar than DIY multisig, and the reason inheritance often tips a holder from rung 4 to rung 5.
When to climb
Most people should stop here or at rung 4. Only step up to 3-of-5 (rung 6) if you have a genuine multi-party or multi-jurisdiction need — otherwise it adds complexity without buying you meaningful safety.