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2026-11-10 aspnetcore kestrel http2

How to accept HTTP/2 over cleartext (h2c) in Kestrel behind nginx on .NET 10

Kestrel on .NET 10 only speaks h2c on an endpoint set to HttpProtocols.Http2, and only to clients that use prior knowledge. Http1AndHttp2 without TLS silently falls back to HTTP/1.1, Upgrade: h2c is ignored, and nginx needs proxy_http_version 2 (1.29.4+, stable 1.30) or grpc_pass to talk HTTP/2 upstream. Checked with curl and HttpClient on ASP.NET Core 10.0.10.

2026-10-21 errors httpclient http2

Fix: HttpProtocolException: The HTTP/2 server reset the stream. HTTP/2 error code 'PROTOCOL_ERROR'

A peer sent RST_STREAM with PROTOCOL_ERROR for one request. HttpClient never retries it. Find which hop reset the stream, fix the request it rejected, retry only idempotent calls, or drop that hop to HTTP/1.1.