Issue Review: cloudflare/workers-sdk#4247

Summary

R2 bindings .put fails with 500 error when passing request.body ReadableStream via unstable_dev in Jest tests.

Findings

• Created: 2023-10-20
• Updated: 2025-10-30
• Version: 3.14.0 → 4.60.0 (current)
• Component: wrangler/R2/miniflare
• Labels: bug
• Comments: 0

Key Evidence

1. Bug still reproduces on wrangler 4.60.0 with a slightly different error message:

   • Original error (2023): Can't read from request stream after response has been sent
   • Current error (2026): Provided readable stream must have a known length (request/response body or readable half of FixedLengthStream)

2. Duplicate/Related issues exist:

   • #6425 (Aug 2024): "R2ObjectBody body ReadableStream not valid for put parameter" - Same error, same root cause
   • #4373 (Jun 2023): "[Miniflare] Consider buffering all requests" - Upstream tracking issue
   • #6504 (Aug 2024): "getPlatformProxy does not accept Node ReadableStreams"

3. Root cause analysis (from #6425 comments):

   • Error originates from workerd runtime, not workers-sdk
   • The workerd RPC requires known length for R2 operations
   • Workaround: Use FixedLengthStream wrapper or buffer the content to a string first

4. No fix PRs found directly referencing #4247 or addressing this underlying issue.

5. No changelog entries mentioning this issue number.

Recommendation

Status: CLOSE (as duplicate)

Reasoning: This issue is a duplicate of #6425, which was filed later (Aug 2024) but has more engagement (8 comments), better diagnosis of the root cause, and includes workarounds. The underlying issue is a limitation in workerd/miniflare that requires ReadableStreams to have a known length for R2 put operations. Both issues describe the same fundamental bug.

Action: Close as duplicate of #6425, which is the more active and better-documented tracking issue for this problem.

Suggested Comment

Thank you for reporting this issue. After investigation, this appears to be a duplicate of #6425, which tracks the same underlying problem: R2's .put() operation in local development (via miniflare/workerd) requires ReadableStreams to have a known length.

The root cause is in the workerd runtime, not workers-sdk specifically. Workarounds include:

1. Buffering the content first: const text = await request.text(); await env.BUCKET.put(key, text);
2. Using FixedLengthStream to wrap streams with known sizes

I'm closing this as a duplicate - please follow #6425 for updates on this issue.