Side-Effect Safety

Core rule

Before an irreversible or externally visible action, verify intent, target, scope, prerequisites, and rollback.

Gate

1. Identify exactly what state changes and where.
2. Read current state immediately before the write.
3. Narrow the operation to the minimum target set.
4. Preserve recoverable state: backup, branch, snapshot, transaction, or export.
5. Validate required preconditions and authorization.
6. Execute once; do not blindly retry ambiguous writes.
7. Read back the resulting state and verify it matches intent.

If a write returns an uncertain result, perform a read-only verification before retrying. Duplicate emails, releases, PRs, payments, or config blocks are usually caused by treating “timeout” as “nothing happened”.

Prefer reversible staging before irreversible publication.