@sproutboat/runtime

The sprout runtime as a unit: the binding and trigger wrapper, handler source validation, both transports (broker and embedded), and the native-fetch prelude. These move as one because wrap.ts locates the prelude and transports by file URL beside itself.

bun add @sproutboat/runtime

import { preludePath, transportPath, wrapNativeFetchHandler } from "@sproutboat/runtime";
import { validateHttpSyncSource } from "@sproutboat/runtime";

API

• wrapNativeFetchHandler(...) turns a user's export default { fetch } into a native-fetch module with bindings, triggers, and env installed. Bindings, EMPTY_BINDINGS, readVarsFromEnv, readBindingsFromEnv, and neutraliseExports travel with it.
• preludePath / transportPath(transport) locate the prelude and the broker / embedded transports on disk. The prelude is read as text and prepended before compilation, never imported.
• TRANSPORT_MARKER, BASELINE_COMPATIBILITY_DATE, Transport type.
• validateHttpSyncSource(source) checks a bundled handler module (SourceValidation), used by project checks on both sides.

The prelude shims the Web API surface handlers expect (URL, Response, crypto random values, binding shims, trigger dispatch) and is identical for both transports, which is what lets one conformance suite hold them honest.

R2 multipart uploads

R2 bindings implement the Cloudflare multipart method shape for objects that are larger than one safe request body:

const upload = env.FILES.createMultipartUpload("archive.tar", {
  httpMetadata: { contentType: "application/x-tar" },
  customMetadata: { source: "backup" },
});

const parts = [];
parts.push(await upload.uploadPart(1, firstChunk));

const resumed = env.FILES.resumeMultipartUpload(upload.key, upload.uploadId);
parts.push(await resumed.uploadPart(2, finalChunk));

const object = await resumed.complete(parts);

Part numbers must be between 1 and 10,000. Parts must be supplied to complete() in ascending order. Every part except the last must have the same size, and the last cannot be larger. Sproutboat permits parts smaller than Cloudflare R2's 5 MiB minimum so the default 1 MiB request-body limit remains useful. Keep each part below the configured request-body limit.

Each part is persisted independently. Standalone completion copies parts into the finished object through a fixed 64 KiB native buffer, so final object size does not determine peak Porffor heap use. A single put() still buffers its whole value; use multipart for larger objects. Call abort() to remove an unfinished upload and its parts.

Completed objects use immutable, etag-addressed blob generations. The metadata row switches to a fully written generation before the previous file is removed. If a metadata update fails, readers continue seeing the previous generation with its matching size and etag.

Unfinished uploads expire after seven days. The broker removes expired parts when another multipart upload starts; a standalone binary removes them when it initializes its embedded store.