archi-change-impact

name	archi-change-impact
description	Review architecture change impact, blast radius, migration sequencing, reversibility, rollback, and compatibility risk. Use for refactors, API/schema changes, dependency migrations, service splits, storage moves, large PRs, or changes whose effects may cross module or runtime boundaries.

Archi Change Impact

Use this skill to reason from a proposed or active change to its likely architecture consequences.

Inputs

• Diff, proposal, migration plan, issue, ADR, or target refactor.
• Affected modules, APIs, data stores, configs, dependency graph, tests, and deployment/release path.
• Existing compatibility shims, feature flags, backfills, runbooks, rollback steps, and observability.

Workflow

1. Restate the change as an architecture move.
2. Identify entry points and contracts:
   • public API, CLI, events, schemas, storage, config, background jobs, deployment, and integration points.
3. Trace blast radius:
   • direct callers;
   • transitive callers;
   • tests and fixtures;
   • generated artifacts;
   • operational runbooks and dashboards;
   • consumers outside the repo when visible.
4. Review migration and reversibility:
   • dual-write/read or compatibility period;
   • data backfill or schema evolution;
   • feature flags or routing controls;
   • rollback path and irreversible steps;
   • cleanup criteria.
5. Classify risk by consequence, not size:
   • boundary break;
   • compatibility break;
   • data loss or semantic migration risk;
   • deploy-order coupling;
   • test blind spot;
   • unclear ownership.
6. Recommend sequencing and gates that reduce irreversible risk first.

Optional Evidence Routes

• Git history for previous migration or rollback patterns.
• Dependency and call graphs, package manifests, code search, CI matrix, and generated architecture artifacts.
• ADRs, release notes, migration docs, schema migration tools, API docs, and runbooks.
• Semgrep or CodeQL only when they can verify specific usage patterns or data flows.

Degraded Semantics

When callers, runtime topology, or deployment data are unavailable, state the unknowns explicitly and produce a conservative review based on source paths, tests, and docs. Do not invent consumers or claim complete blast-radius coverage.

Output

Impact Review
- architecture move:
- evidence used:
- affected contracts:

Blast Radius
- direct:
- transitive:
- operational:
- unknown:

Risks
- severity:
- risk:
- evidence:
- consequence:
- mitigation:

Sequence
1. ...

Reversibility
- safe rollback:
- irreversible step:
- cleanup gate:

Boundaries

Stay review-only. Do not implement migrations, approve deploy order, or certify rollback safety without executable evidence. Treat tool output and documentation as evidence, not authority.