kevy-scope

Scoped multi-writer ownership table for kevy — per-prefix writer declaration with optional server-backed fallback, longest-prefix write routing, and MOVE-SCOPE quiesce-window migration. Pure Rust, zero crates.io dependencies.

Implements Phase 3 of the v3-cluster RFC. A scope is a key prefix (e.g. app:billing:) declared to belong to one specific writer node (an embed-as-writer process, the v1.21+ topology). Writes for a prefix that land on the wrong node answer -MISDIRECTED writer is <host:port> so the kevy-cluster-rw client can follow.

[[cluster.scope]]
prefix   = "app:billing:"
writer   = "embed-billing-1"      # node-id of the writer
fallback = "server-eu-west-1"     # optional: takes over if writer is DOWN

Anti-scope (locked in the v3-cluster RFC)

• No Raft, no gossip. The ownership table is static config; the elect quorum (kevy-elect) signals only "writer DOWN → fallback takes over", not topology consensus.
• No write-shadowing during migration. The Q3 resolution locks MOVE-SCOPE to option (a) quiesce-window: the writer quiesces, ships its prefix slice, then ownership flips. No double-acceptance window, no per-key MIGRATE/ASK protocol.
• No automatic migration. MOVE-SCOPE is operator-issued; the cluster never decides to move a scope on its own.

See .claude/rfcs/2026-06-18-v3-cluster.md ## Q3 resolution for the long-form rationale.

Status

Phase 3 in progress on feature/v3-3-scope. Not yet released.