CI flake: C# quickstart client misses Alice output on Windows

[clockwork-labs-bot]

Detected by CI Gremlin after a failed GitHub Actions attempt succeeded on rerun.

Tests:

• cluster::quickstart::test_quickstart_csharp

Error:
thread 'cluster::quickstart::test_quickstart_csharp' (3240) panicked at crates\smoketests\tests\cluster\quickstart.rs:866:25:
C# quickstart test failed: Expected output to contain 'Alice', but got:

Failed job runs:

• https://github.com/clockworklabs/SpacetimeDB/actions/runs/33429922470/job/99618213606 (Smoketests (Windows 3/4), attempt 1 -> 2)

Timeout detection:

• none

Context:

• none

[clockwork-labs-bot]

Exact-attempt diagnosis:

The linked job is Smoketests (Windows 3/4), run 33429922470, job 99618213606, attempt 1. The ticket says attempt 1 -> 2, and the job API reports run_attempt: 1.

The job ran on Windows runner ghr-1366c2fd for PR #5850 (bot/reject-direct-public-release), head SHA 9e45a5ef8d907d0eda0df99895732e1f2dcb1492. Checkout, Rust setup, .NET setup, Node/pnpm setup, Emscripten setup, psql install, artifact download, and archive extraction all succeeded. The failure was inside Run smoketest partition (Windows).

Failure signature:

• cluster::quickstart::test_quickstart_csharp ran for 60.664s and failed.
• The quickstart harness first ran the C# client with an empty input. That client connected, then printed Failed to send message : Messages must not be empty.
• The harness then ran the C# client with /name Alice; that second client connected, but its captured output ended after Connected and did not contain Alice.
• The Rust harness panicked at crates\smoketests\tests\cluster\quickstart.rs:866:25 with C# quickstart test failed: Expected output to contain 'Alice', but got:.

Root cause visible in this exact attempt: the local server and both C# clients started successfully, but the C# quickstart interaction did not observe the expected /name Alice result before the harness checked captured output. This looks like a C# quickstart client/server interaction timing or subscription-output flake on Windows, not a setup failure, compile failure, missing dependency, or runner-loss/no-log incident. The Node 20/24 deprecation warnings were incidental; the failing step was the Rust smoketest partition.

Suggested updated title:
CI flake: C# quickstart client misses Alice output on Windows

Duplicate analysis:

• Exact and fallback public searches for test_quickstart_csharp, C# quickstart test failed, Expected output to contain Alice, Messages must not be empty, quickstart-chat-csharp, and C# quickstart/Alice smoketest terms found no older close duplicate in clockworklabs/SpacetimeDB.
• Test Flakes has broad public Windows smoketest neighbors, but the close ones I checked are different mechanisms: Chocolatey/psql setup failures (CI flake: Smoketests (Windows 3/4) #5744, CI flake: Smoketests (Windows 3/4) #5757), runner-loss/no-log failures (CI flake: Smoketests (Windows 3/4) #5802, CI flake: Smoketests (Windows 3/4) #5821, CI flake: Smoketests (Windows 3/4) #5832), Windows release-download TLS/fallback failures (CI flake: Windows TLS trust failure when fetching release from GitHub #5724), and unrelated C# publish/download failures (CI flake: C# smoketests fail during pre_publish with Broken pipe #5688, CI flake: Test Suite / tests::test_basic_invariants_spacetime_module_csharp #5733, CI flake: Smoketests (Windows) / smoketests::csharp_aot_module::test_build_csharp_module_aot #5312).

Top duplicate candidate: none. Similar Windows and C# smoketest tickets exist, but none are close enough to mark as duplicates.

Leaving this ticket open.