gRPC runs over HTTP/2. A PROTOCOL_ERROR (RST_STREAM code 1) means the peer rejected the stream at the HTTP/2 layer: typically the target is not a real gRPC server, or a proxy/load balancer between them does not speak HTTP/2 end to end.
What this error means
A call fails with "14 UNAVAILABLE: ... Received RST_STREAM with code 1 (PROTOCOL_ERROR)" or "stream terminated by RST_STREAM with error code: PROTOCOL_ERROR", often through an ingress or proxy.
gRPC
Error: 14 UNAVAILABLE: Received RST_STREAM with code 1 (PROTOCOL_ERROR)
at Object.callErrorFromStatus (.../call.js)
Diagnose it: produced, uploaded, or mapped?
Third-party integrations fail at one of three points, and the symptom is the same for all of them: the report was never produced, the upload was rejected, or the service could not map the paths back to your repository.
Terminal
ls -la <report-dir>/ && head -5 <report-file>
grep -c . <report-file> || echo "empty report"
# absolute paths in a report break server-side file mapping
grep -m3 -E "^(SF:|<file)" <report-file>
Common causes
The target is not a gRPC/HTTP/2 server
The client connected to an HTTP/1.1 endpoint or a wrong port, so the HTTP/2 frames the server returns are rejected as a protocol error.
A proxy that does not preserve HTTP/2
A load balancer or ingress terminates or downgrades HTTP/2, breaking the end-to-end protocol gRPC requires.
How to fix it
Point the client at a real gRPC endpoint
Confirm the target port serves gRPC (HTTP/2), not an HTTP/1.1 app.
If a proxy sits in between, configure it for end-to-end HTTP/2 (h2c or gRPC mode).
Verify with grpcurl against the same address.
Terminal
grpcurl -plaintext localhost:50051 list # confirms it speaks gRPC
Enable HTTP/2 through the proxy
Set the proxy/ingress backend protocol to gRPC or HTTP/2 so frames are not downgraded.
YAML
# nginx ingress: backend must speak gRPC end to endnginx.ingress.kubernetes.io/backend-protocol:"GRPC"
How to prevent it
Connect only to ports that serve gRPC over HTTP/2.
Configure proxies and ingress for end-to-end HTTP/2.
Smoke-test the endpoint with grpcurl before the suite.
Frequently asked questions
What causes gRPC "PROTOCOL_ERROR" over HTTP/2 in CI?
There are 2 common causes: the target is not a grpc/http/2 server and a proxy that does not preserve http/2. The client connected to an HTTP/1.1 endpoint or a wrong port, so the HTTP/2 frames the server returns are rejected as a protocol error.
How do I fix gRPC "PROTOCOL_ERROR" over HTTP/2 in CI?
There are 2 fixes depending on which cause you have: point the client at a real grpc endpoint and enable http/2 through the proxy. Work through them in order, since the first is the most common.
What does gRPC "PROTOCOL_ERROR" over HTTP/2 in CI actually mean?
A call fails with "14 UNAVAILABLE: ...
How do I stop gRPC "PROTOCOL_ERROR" over HTTP/2 in CI happening again?
Connect only to ports that serve gRPC over HTTP/2. The prevention section lists 3 changes that keep it from recurring.
