assets

assets example

Important

PREVIEW ONLY This package is provided as a preview for feedback only. APIs are unstable and the design is subject to change.

A Cloudflare Worker + Durable Object that turns a text prompt into an image and hands back a shareable link. One shot: POST /prompt, get a URL.

The Durable Object runs the prompt through a Workers AI text-to-image model, writes the generated PNG into its Workspace, then uploads that file to R2 and returns a presigned URL through @cloudflare/computer/assets.

Note

This is a production-only example. The presigner needs R2 S3 credentials, and the image model runs on Cloudflare's network, so wrangler dev against a local stack won't produce a working link. Deploy it and hit the deployed URL.

Architecture

client ─► Worker POST /prompt
            │  (DO RPC call)
            ▼
      AssetWorkspace DO ──► env.AI.run(flux)        generate the image
                        ──► Workspace.fs.writeFile  store it in the VFS
                        ──► createAssets(...).share  upload to R2 + presign
            │
            ▼
      { path, url }

1. The Worker accepts POST /prompt and forwards the prompt to a single AssetWorkspace Durable Object.
2. The DO holds a backend-less Workspace — it only needs the filesystem, not a shell. It runs the prompt through the FLUX.2 [klein] 9B model on env.AI, which returns the image as base64.
3. The DO decodes the image, writes it to /workspace/<uuid>.png, then calls createAssets(...).share to upload the file to R2 and presign a GET URL.
4. The response is { path, url }. The link is valid for one hour.

Configuration

The bucket binding alone can't mint a presigned URL, so the presigner needs R2 S3 credentials. Create an R2 API token scoped to the bucket. The credential names are listed in .dev.vars.example; copy it to .dev.vars to fill them in, then set the same values as secrets for production:

wrangler secret put R2_ACCESS_KEY_ID
wrangler secret put R2_SECRET_ACCESS_KEY
wrangler secret put CLOUDFLARE_ACCOUNT_ID

The bucket name is supplied to the assets client through the ASSETS_BUCKET_NAME var in wrangler.jsonc; keep it in step with the bucket_name on the ASSETS binding.

Create the bucket once before the first deploy:

wrangler r2 bucket create computer-assets-example

HTTP surface

POST /prompt   { "prompt": "..." }
               → { "path": "/workspace/<uuid>.png", "url": "https://..." }

Deploy and run

npm run deploy --workspace @example/computer-assets

curl -X POST https://computer-assets-example.<your-subdomain>.workers.dev/prompt \
  -H 'content-type: application/json' \
  -d '{"prompt":"a sunset over the alps, oil painting"}'

The response carries a url; open it to see the generated image. The link expires after an hour, after which the object stays in the bucket but the URL stops working. See the assets interface for the cleanup story.

Layout

examples/assets/
  wrangler.jsonc      Worker + DO + AI + R2 bindings
  .dev.vars.example   R2 S3 credential names; copy to .dev.vars
  src/index.ts        Worker handler + DO (AssetWorkspace)