The cross-language client e2e matrix failed for dotnet and Java. Both
failures were in the harness, not the client code.
1. Per-call toolchain cold-start. The matrix issues ~250 CLI calls per
client; it invoked `dotnet run` / `gradle :mxgateway-cli:run` every
time, rebuilding and cold-starting the toolchain per call. Build each
CLI once up front (`dotnet build`, `gradle :mxgateway-cli:installDist`)
and invoke the compiled artifact directly. This alone fixes dotnet.
2. Worker event-channel overflow. The per-tag advise loop advises every
discovered tag with no StreamEvents consumer attached, so change
events accumulate in the worker event channel
(MxGateway:Events:QueueCapacity) until FailFast faults the worker.
dotnet's faster loop slipped under the window; the Java CLI's
process-per-call JVM cold-start did not. Every -DrainEveryTags advised
tags (default 15) the loop connects a short StreamEvents drain; the
gateway's per-stream producer empties the channel the instant a
subscriber attaches, so a small bounded read suffices.
Full 5-client matrix (dotnet, go, rust, python, java) now passes with
-VerifyWrite against a live gateway.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Joseph Doherty
c1ff8c94e8