load_game probes the version field and refuses anything but SAVE_VERSION with a legible message naming the pre-release policy and promising the old file and its backup survive (verified live against a v29 save: fresh run, file untouched). Deleted behind the gate: the v1-v30 migration ladder, five migration passes, six legacy-only types and their SaveState fields, the retired-mode and Knowledge serde aliases, the four-weight allocation pad, research's three-track arity layer, and twenty-four ladder tests - 2,026 lines removed, 108 added including the refusal test. Atomic writes, backup rotation, current-version consistency checks, and the canonical fingerprint are untouched. Defense: wiki/vision/player-contract.md continuity clause, pre-release rider (2026-07-16): development saves may break, and carrying thirty versions of legacy weight was the cost Cameron declined to keep paying. core.md (the owning save spec) carries the status note; sim-mechanics.md and the CLAUDE.md doorway are rewritten to the new policy in this commit.