execute-hard-cutoverlisted

# Execute Hard Cutover Run a hard cutover when a predecessor implementation must stop owning a path and a destination must become the only writer. ## When to use - Replacing a system, package, API, instruction set, or data path - Dual-write / dual-read shims have become permanent residue - Expand/contract is only a temporary phase, not the end state ## Workflow 1. **Name the cut.** Predecessor, destination, traffic/data surface, and terminal: destination sole writer; predecessor retired for that surface. 2. **Inventory dependency.** Callers, data, jobs, docs, install paths, feature flags. Record what must migrate. 3. **Prefer hard cut.** Default is switch + retire. Use short expand/contract only when required for safety, with an explicit end date and owner. 4. **Backfill.** Move or rebuild required state at the destination before cut. Verify with original oracles, not memory. 5. **Cut traffic.** Point writers and readers at destination. Block new predecessor writes. 6. **Retire predecessor.** Delete or quarantine dead paths in the same delivery unit when safe. Do not leave "just in case" dual paths. 7. **Prove.** Destination handles the surface under real checks. Predecessor no longer receives production responsibility for that surface. ## Gotchas - A green dual-path is not done. - Feature flags that never expire become the new system of record — ban them as the terminal state. - Docs and installers often keep pointing at the predecessor after code cutover. ## Validat