The 'cli push' and disconnect-robustness scenarios bound a fixed loopback port, so two e2e binaries running at once — the ordinary case under a parallel build or a busy CI runner — collided on it and one push exited non-zero, failing an unrelated-looking assertion. The failure was invisible because the assertion reported only the child's exit code and discarded its stderr.

Each scenario now draws a fresh port from the kernel (bind :0, read back the assigned port, release) and waits for the child to accept before driving it, the same approach freshLoopbackPort takes for the Fossil smoke tests. The push assertion now surfaces the child's stderr on failure, so the next divergence is diagnosable rather than merely counted.

Verified on Linux under the exact condition that reproduced the flake: two 'zig build e2e' runs in parallel, ten rounds, x86_64 and aarch64 — 20 of 20 green on each, where the fixed-port version failed intermittently. check-in: b4a5886252 user: dmestas tags: trunk