ADR-058: Fusion Mechanism

Status: Implemented Date: 2026-05-27 Deciders: Ravi Chavali

Context

Fission (ADR-057) allows a community to split into two. Fusion is the symmetric inverse — two communities voluntarily merge into one. Both mechanisms complete the community lifecycle toolkit in the v10.0 Trust Network arc.

Decision

Fusion is bilateral and consensual at every step:

1. Proposal: Admin A initiates, naming the merged community and providing a rationale.
2. Acceptance: Admin B accepts or rejects the proposal.
3. Discussion: Both admins can discuss before opening the vote.
4. Parallel vote: Each community votes independently; both must pass 60% quorum + 60% approval (trust-weighted).
5. Execution: Either admin executes. A new merged community is created with all members, trust, and karma from both originals.

On execution:

• All active members are added to the merged community.
• Trust edges from both originals are copied with 0.70 carry factor (maintains normalization constraint: user_id_a < user_id_b).
• Karma records from both communities are copied into the merged community.
• Original communities receive status='merged'.
• Two fusion_origin community_links are created: (merged↔A) and (merged↔B).

Trust Carry Factor (0.70)

Fission uses 0.40 — low, because the split severs relationships. Fusion uses 0.70 — higher, because the merge is consensual and the member base is actively choosing to come together. Trust history should be preserved with high fidelity.

Database Schema

Two new tables in the communities schema:

• fusion_proposals — lifecycle record for each proposal (status: pending_acceptance → discussion → voting → approved → executed | rejected)
• fusion_votes — per-member, per-community votes with prestige weighting

The community_links.link_type CHECK constraint is extended to include 'fusion_origin'.

Rationale

• Bilateral consent ensures no community is absorbed against its will.
• Parallel votes preserve each community's democratic sovereignty.
• New merged community (rather than absorption) is symmetric with fission and avoids privileging one community's identity over the other.
• Trust and karma inheritance reduces the activation energy for fusion, making it a viable governance tool rather than a last resort.
• Auto-approval (status advances to approved when both tallies pass) eliminates the need for a polling background job.