Implementation Strategy

Overview

Quick start

1. Identify the surface you are changing: released public API, unreleased branch-local API, internal helper, persisted schema, wire protocol, CLI/config/env surface, or docs/examples only.
2. Determine the latest release boundary from

   origin

   first, and only fall back to local tags when remote tags are unavailable:
   bash

   LATEST_RELEASE_TAG="$(
     git ls-remote --tags --refs origin 'v*' 2>/dev/null |
       awk -F/ '{print $3}' |
       sort -V -r |
       head -n1
   )"
   if [ -z "$LATEST_RELEASE_TAG" ]; then
     LATEST_RELEASE_TAG="$(git tag -l 'v*' --sort=-v:refname | head -n1)"
   fi
   printf '%s\n' "$LATEST_RELEASE_TAG"

3. Judge breaking-change risk against that latest release tag, not against unreleased branch churn or post-tag changes already on

   main

   . If the command fell back to local tags, treat the result as potentially stale and say so.
4. Prefer the simplest implementation that satisfies the current task. Update callers, tests, docs, and examples directly instead of preserving superseded unreleased interfaces.
5. Add a compatibility layer only when there is a concrete released consumer, an otherwise supported durable external state that requires it, or when the user explicitly asks for a migration path.

Compatibility boundary rules

• Released public API or documented external behavior: preserve compatibility or provide an explicit migration path.
• Persisted schema, serialized state, wire protocol, CLI flags, environment variables, and externally consumed config: treat as compatibility-sensitive once they are released or otherwise have a supported external consumer. Unreleased post-tag formats that only exist on the current branch can still be rewritten directly.
• Interface changes introduced only on the current branch: not a compatibility target. Rewrite them directly.
• Interface changes present on

  main

  but added after the latest release tag: not a semver breaking change by themselves. Rewrite them directly unless they already back a released or otherwise supported durable format.
• Internal helpers, private types, same-branch tests, fixtures, and examples: update them directly instead of adding adapters.

Default implementation stance

• Prefer deletion or replacement over aliases, overloads, shims, feature flags, and dual-write logic when the old shape is unreleased.
• Do not preserve a confusing abstraction just because it exists in the current branch diff.
• If review feedback claims a change is breaking, verify it against the latest release tag and actual external impact before accepting the feedback.
• If a change truly crosses the latest released contract boundary, call that out explicitly in the ExecPlan, changeset, and user-facing summary.

When to stop and confirm

• The change would alter behavior shipped in the latest release tag.
• The change would modify durable external data or protocol formats that are already released or otherwise supported.
• The user explicitly asked for backward compatibility, deprecation, or migration support.

Output expectations

• Compatibility boundary: latest release tag v0.x.y; branch-local interface rewrite, no shim needed.

• Compatibility boundary: latest release tag v0.x.y; unreleased RunState snapshot rewrite, no shim needed.

• Compatibility boundary: released RunState schema; preserve compatibility and add migration coverage.