Issue Review: cloudflare/workers-sdk#6515

Summary

POST requests with body to a Worker/DO in local dev throw "Can't read from request stream after response has been sent" error.

Findings

• Created: 2024-08-16
• Updated: 2025-10-30
• Version: wrangler 3.72.0 → 4.61.0
• Component: wrangler
• Labels: bug
• Comments: 5

Key Evidence

• Reporter @threepointone (Cloudflare employee) found bug with POST requests to Durable Objects
• Error: "TypeError: Can't read from request stream after response has been sent"
• Related error in workerd: "kj/compat/http.c++:1989: failed: expected clean; can't read more data after a previous read didn't complete"
• Error appears with or without Content-Type header
• Workaround: Drain the body before sending response (e.g., await request.text())
• Local dev is "extremely fragile" - ~30% failure rate on simple benchmarks
• Repro repo provided: https://github.com/threepointone/durable-post-error

Recommendation

Status: KEEP OPEN

Reasoning: Valid bug affecting POST requests in local dev. Filed by Cloudflare employee with reproduction. The workaround (draining body) isn't always feasible. The ~30% failure rate and brittleness suggest deeper issues with request handling.

Action: Investigate request body handling in local dev, particularly for Durable Objects. Related to http stream management in workerd/miniflare.

Suggested Comment

N/A - Internal Cloudflare issue with clear reproduction; requires engineering investigation.