Cloudflare R2 Object Storage & Presigned URL Pipeline Skill

Zero-egress object storage architecture on Cloudflare R2: S3-compatible presigned upload URLs, multipart streaming, CORS policies, and custom domain cachin

---
name: cloudflare-r2-storage
description: Zero-egress object storage architecture on Cloudflare R2: S3-compatible presigned upload URLs, multipart streaming, CORS policies, and custom domain caching. Use when working with Cloudflare R2, S3 API, Workers, Presigned URLs.
triggers:
  - cloudflare r2 storage
  - cloudflare r2
  - s3 api
---

# Cloudflare R2 Object Storage & Presigned URL Pipeline Skill

## 1. When to Use This Skill
Load `skill-cloudflare-r2-storage` whenever an engineering or operations task involves **Cloudflare R2, S3 API, Workers, Presigned URLs**. Specifically:
- Zero-egress object storage architecture on Cloudflare R2: S3-compatible presigned upload URLs, multipart streaming, CORS policies, and custom domain caching.
- Designing, reviewing, or debugging production configurations without guesswork or deprecated flags.
- Running deterministic pre-flight and post-execution verification checks before reporting completion.

## 2. Prerequisites & Required Environment
- **Target Stack:** Cloudflare R2, S3 API, Workers, Presigned URLs
- **Permissions:** Read-only inspection by default; ask for explicit confirmation before executing destructive mutations or production deployments.
- **Reference Repository:** `https://github.com/cloudflare/skills`

## 3. Step-by-Step Execution Playbook
1. **Context & Configuration Discovery:**
   Inspect existing project manifests (`package.json`, `wrangler.jsonc`, schema files, or environment declarations) before proposing changes. Never overwrite existing bindings or credentials blindly.
2. **Deterministic Implementation:**
   Apply the canonical patterns for **Cloudflare R2**:
   - Enforce strict schema/type validation at every external boundary.
   - Include explicit error handling, structured logging, and idempotency keys on all mutating calls.
   - Keep secrets in environment variables or secret stores—never hardcode tokens in source files.
3. **Verification & Regression Gate:**
   Run the verification commands below and inspect both exit codes and output payloads before marking the task complete.

## 4. Reference Commands & CLI Workflow
```bash
npx wrangler r2 bucket create assets-prod
npx wrangler r2 object put assets-prod/index.json --file=./data.json
```

## 5. Edge Cases & Anti-Hallucination Guardrails
- **Zero Unverified Claims:** Never claim a deployment, migration, or API call succeeded without inspecting the command output or HTTP status code.
- **Rollback Readiness:** Always record the previous state or migration version so changes can be reverted cleanly if downstream health checks fail.

Synthesized Engineering Blueprint & Setup Guide