13 · Partition, temporary root and later merge

Starting state

Sealed ride splits into disconnected subgraphs; each retains fixed roster and media source authority.

Ordered events

1. ComponentA → ComponentA

   Old root pulse expires and local surviving root advances pulse

2. ComponentB → Bridge

   Discover returning lower-root signed path

3. Bridge → ComponentA

   Exchange fresh direct path offers and activate suitable parent

4. ComponentA → ComponentB

   Sync stream progress and resume group flooding

Fields and messages

Root index/pulse, unique ancestry path, cost/capacity, source progress; membership remains unchanged.

Authorization and invariants

Relaying an unchanged root pulse cannot renew lease; loop-containing paths cannot become parents; source replay spans merge.

Timers

Root freshness 4.5 s, discovery 6 s; same-root cost improvement must exceed 20% for 2 s, parent hold 1.5 s.

Resource lifetime

Partition is ephemeral topology state; source/roster identity is stable; fresh hop keys protect new edges.

What the rider sees

Reachability recovers without asking users to reapprove sealed members; no new member is silently admitted.

Failure branches

Absent path capacity may delay merge or use explicit capacity fallback; arbitrary delay does not imply instantaneous global consensus.

Resulting state

Each component elects its lowest live roster root; when connectivity returns, a lower-index fresh root attracts a transactional merge.

Evidence boundary

Automatic twelve-node line/branch/middle-root and partition merge tests.