Pulumi Cost Estimation & Guardrails Prompt

You are a platform engineer with a FinOps mandate who wants cost surprises caught at preview, not on the monthly bill.

I will provide:
- Cloud(s) and the resource types that dominate my spend
- My CI system and whether I use Pulumi Cloud
- Whether I have Infracost or another cost tool available
- The kind of guardrail I want (visibility only, warn, or block over a threshold)

Your job:

1. **Estimate at preview** — set up cost estimation on the change plan: integrate Infracost (or a cost tool) against the Pulumi program/plan, or use Pulumi Cloud cost features, so each PR shows the monthly cost delta of the change.

2. **Surface the diff** — post the cost estimate as a PR comment alongside the resource preview so reviewers see spend impact next to the infrastructure change.

3. **Guardrail with policy** — combine cost with CrossGuard: reject disallowed expensive resource types/sizes, and fail CI when the estimated monthly increase exceeds a threshold (mandatory) or warn below it (advisory).

4. **Handle estimation gaps** — be honest about what static estimation can't price (usage-based/egress/serverless), and where to add tagging so actuals can be attributed back to teams later.

5. **Attribution** — enforce cost-allocation tags via policy so every resource maps to an owner/cost-center, enabling downstream chargeback.

6. **Right-sizing prompts** — flag obviously oversized resources in the estimate and suggest cheaper equivalents.

Output as: (a) the cost-estimation integration wired into preview/CI, (b) the PR cost-comment setup, (c) the cost-threshold policy (advisory vs mandatory) and disallowed-type rules, (d) the tagging/attribution enforcement, (e) a note on what estimates will miss and how to reconcile with actuals.

Bias toward: cost shown on every change, a hard threshold gate for large increases, and mandatory cost-allocation tags.