# Upgrade Guide — vNEXT

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## What Changed

Root-cause fix for "how did ~20 features ship incompatible with the seamless
multi-machine goal?" (operator question, 2026-06-12 topic 13481): no review surface
ever asked. Now three do —

1. The instar-dev side-effects template gains mandatory **§7 Multi-machine posture**:
   every change declares replicated (named path) / proxied-on-read (named read) /
   machine-local BY DESIGN (with the reason). A silent single-machine assumption is a
   finding, not a posture. (Rollback cost renumbered §7→§8.)
2. spec-converge's integration/deployment reviewer charter makes the same check
   mandatory at spec time — a machine-blind spec is a MATERIAL finding that blocks
   convergence.
3. The Cross-Machine Coherence constitution article's "Applied through" is widened to
   name these gates (per-feature posture rule), giving the Standards Enforcement
   Coverage audit a verifiable surface.

Deployed agents receive the updated skill content via a new PostUpdateMigrator
migration (`migrateMultiMachinePostureReviewDimension`) — marker-sniffed,
fingerprint-guarded (operator-customized files left untouched + reported), idempotent,
following the migrateSpecConvergeFoundationAudit pattern.

## What to Tell Your User

- "The development process that builds my features now has a mandatory checkpoint: every new feature must declare, in writing, how it behaves when I run on more than one machine — it travels with me, it's readable from any machine, or it deliberately belongs to one machine for a stated reason. This is the structural fix for the batch of features that previously assumed a single machine."

## Summary of New Capabilities

| Capability | How to Use |
|-----------|-----------|
| Multi-machine posture is a mandatory review dimension | Automatic — enforced in the side-effects template + spec-converge reviews; deployed agents receive the updated review docs on their next update |

## Evidence

- `tests/unit/PostUpdateMigrator-mmPostureReviewDimension.test.ts` — 4 tests: bundled
  sources really carry the marker; stock installed copies upgraded + idempotent;
  customized copies untouched + reported; missing files skipped silently.
- `tsc --noEmit` clean; affected suites green.
- Side-effects artifact: `upgrades/side-effects/multi-machine-posture-review-dimension.md`.
- Plain-English overview: `docs/eli16/multi-machine-posture-review-dimension.md`.

## What Changed for the Review Process

This change's own side-effects artifact answers the new question about itself
(machine-local by design: per-machine installed skill content kept current by each
machine's update cycle) — the gate is dogfooded on the PR that introduces it.
