Buy vs build review

Buy vs Build Review

Review the diff for ownership choices, not just correctness. Prefer findings that reduce risk, code, dependencies, or vendor lock-in without weakening safety.

Workflow

1. Inspect changed files and dependency manifests.
2. Flag custom code that a built-in, native platform feature, already-installed dependency, mature open source package, or commercial service should replace.
3. Flag new dependencies or services that duplicate built-ins, installed packages, or tiny clear code.
4. Check that the choice was implemented well, not just chosen well. The right rung integrated badly is still a finding: a wrapper that re-does the work the dependency already does, an SSE/WebSocket/queue added without handling its real failure modes (reconnect, retry, backpressure, idempotency), or a "reuse" that grew more glue code than it removed. Confirm the change actually cut code, failure modes, and operating burden.
5. Preserve safety boundaries: validation, security, privacy, accessibility, observability, and explicit requirements.
6. Judge the decision note as the reviewable artifact. Where the diff makes a non-obvious or hard-to-reverse choice, the note (in the PR body or a docs/decisions/ ADR) should name the distinguishing requirement, the rejected option, and a revisit trigger. A missing or vague note is itself a finding — it is often the most valuable thing in the change, because it is what makes the tradeoff reviewable later.
7. Report findings first, ordered by severity, with file references when possible.

Output

Use this shape:

Findings
- [severity] file:line - Issue. Better option: <rung>. Tradeoff: <why>.

Integration
- [severity] file:line - Right option, but: <unused capability / unhandled failure mode / glue code that outweighs the reuse>.

Decision gaps
- Missing or vague decision note for <choice> — name the distinguishing requirement, rejected option, and revisit trigger.

If there are no issues, say so and list any residual dependency or ownership risks.