channel shutdown error obtrudes on network errors

[benjaminp]

When a call on a gracefully-terminating ManagedClientChannel experiences a network error, the call is closed with a message suggesting the error is from channel closing rather than the network.

See my reproduction at https://github.com/benjaminp/grpc_shutdown_bug. The program in that repository

1. starts a server
2. makes a channel to the server
3. starts a server-streaming call on the channel
4. (optionally) shuts down the client channel
5. forcibly kills the server.

When the client channel is shutdown, the client sees a UNAVAILABLE: Channel shutdown invoked error on server death:

$ ./gradlew run
> Task :run
client: launching server: build/install/streaming-demo-client/bin/streaming-demo-server
client: server pid=234110 port=44637
client: creating channel
client: starting server-streaming RPC
client: reading 1 message
May 15, 2026 3:07:05 PM io.grpc.netty.TcpMetrics loadEpollInfo
INFO: Epoll available during static init of TcpMetrics:false
May 15, 2026 3:07:05 PM io.grpc.netty.TcpMetrics loadEpollInfo
INFO: Epoll available during static init of TcpMetrics:false
client: read: 0
client: shutting down channel (graceful)
client: channel.isShutdown=true isTerminated=false
client: reading another message
client: read: 1
client: server exited with 137
client: draining until error
client: drained with error: io.grpc.StatusException: UNAVAILABLE: Channel shutdown invoked
done

Contrast with the error when the channel is not shutdown:

$ ./gradlew run --args=--noshutdown

> Task :run
client: launching server: build/install/streaming-demo-client/bin/streaming-demo-server
client: server pid=234631 port=39449
client: creating channel
client: starting server-streaming RPC
client: reading 1 message
client: read: 0
client: shutting down channel (graceful)
client: channel.isShutdown=false isTerminated=false
client: reading another message
client: read: 1
client: server exited with 137
client: draining until error
client: drained with error: io.grpc.StatusException: UNAVAILABLE: Network closed for unknown reason
done

I believe the first case should also fail with UNAVAILABLE: Network closed for unknown reason.

[shivaspeaks]

We have Status precedence in ClientTransportLifecycleManager which is is designed to store the first shutdown status it receives. In the case of a graceful shutdown, the first status it receives is the one from the channel ("Channel shutdown invoked").

When a network error occurs (e.g., the server is killed), the transport's channelInactive method is triggered. It attempts to fail all active streams with a generic "Network closed for unknown reason" status. However, before reporting the error to the streams, it checks if the lifecycleManager already has a shutdownStatus.
Because the graceful shutdown was initiated first, the manager returns the "Channel shutdown invoked" status, and this message is reported to all active RPCs, even though they failed due to a network disconnection.