---
name: catalyst-stratus
description: "Catalyst Stratus — object storage service with upload/download, signed URLs, and multipart upload support. Stratus uses its own SDK-based APIs (not S3-API-compatible). Migrate from AWS S3 or GCS using the Stratus Migration Tool. Trigger on 'Stratus', 'object storage', 'upload file', 'signed URL', 'putObject', 'getObject', or 'bucket'."
metadata:
  version: "2.1.2"
---

## How It Works

1. **Bucket naming** — Bucket names are globally unique. Use `{app-name}-{project-id-prefix}` pattern to avoid collisions.
2. **Load `references/stratus-basics.md`** — for upload/download/delete patterns, the 250 GB single-upload limit, signed URL generation, and multipart setup.
3. **Large files** — Multipart upload is recommended (not required) for files ≥ 100 MB. Single-shot upload supports up to 250 GB per object. Load the multipart section of `stratus-basics.md`.
4. **Signed URLs** — For user-facing direct downloads/uploads, generate a signed URL server-side and return it to the client.

## Response Syntax Default

When writing function code that returns a Stratus result to the client, **default to native Node.js response syntax** — not Express. Advanced I/O exposes raw `http.ServerResponse`; `res.status()` and `res.json()` do not exist unless the user explicitly chose the Express template.

- Native (default): `res.writeHead(200, { 'Content-Type': 'application/json' }); res.end(JSON.stringify(data));`
- Express (opt-in only): only if the user has `express` installed and wired as middleware

## Triggers

Use this skill for: "Stratus", "object storage", "file storage", "upload file", "download file", "signed URL", "pre-signed URL", "multipart upload", `putObject`, `getObject`, "bucket", "Stratus bucket", "store files on Catalyst", "Stratus vs File Store", "250GB limit", or "file download link".

## References

| Reference | Load when the query is about… |
|-----------|-------------------------------|
| `references/stratus-basics.md` | Upload/download/delete, 250GB single-shot limit, multipart (recommended for ≥100 MB), signed URLs, busboy upload pattern, bucket naming rules |