compact

Garbage-collect tombstoned elements that are causally stable under the eviction-safe causal-stability barrier (ADR-003 addendum v3, #262).

A tombstoned element with dot (r, sᵢ) is purged iff all hold:

1. Tombstoned — implied (only tombstones are candidates).

2. Causally stable — sᵢ ≤ stableCut[r]: every live peer has delivered it.

3. Frontier-complete — ∀x: delivered[x] ≥ frontierMax[x]: this replica has delivered every op below every known frontier, so condition 4 below is complete (any concurrent Insert(_, after=id) that exists anywhere has been delivered locally and is therefore visible to condition 4).

4. No surviving local successor — no surviving RgaOp.Insert has after == id, preserving the structural-predecessor invariant.

Conditions 2 and 3 are the author-independent barrier the prior scalar watermark silently assumed: a concurrent Insert(J, after=I) minted by a different author cannot coexist with a frontierMax this replica has fully delivered. See the ADR for the by-construction safety argument against the #272 (author-independence) and #275 (eviction) probes.

Parameters