Make proxy error-path test independent of TCP refusal timing.

The streaming, credentials, and logging assertions had already passed.
The failure occurred in the final check, which expected HTTP 502 after
reconnecting to a closed upstream port.

The test assumes connection refusal completes quickly. Windows TCP
retry behavior can exceed the test's two-second deadline. Both the
client and proxy use that deadline, so the client can time out before
receiving an error response. Linux and macOS passed in the linked run.

The local upstream fixture now accepts the final request and closes
without responding, producing an upstream error without depending on
connection-refusal timing.

See: https://github.com/asimov-platform/asimov-sdk/actions/runs/37508505937/job/112423220048

Author: artob

rust/TODO.md

@@ -61,6 +61,11 @@ reproductions and build results are distinguished from source-review findings.
 
 ## P2: Build, feature, and facade correctness
 
+- [ ] **Confirm the proxy HTTP 502 fixture fix on Windows CI.**
+  Run 37508505937 timed out while reconnecting to a closed upstream port in
+  `lib/asimov-proxy/src/openai.rs`. The fixture now accepts and closes the final
+  request without responding; local tests pass on macOS.
+
 - [ ] **Make the no-std contract hold on a target without std.**
   Host `--no-default-features` checks pass, but `asimov-core` fails for
   `thumbv7em-none-eabihf`: default-enabled `know` pulls `serde_json/std` and

rust/lib/asimov-proxy/src/openai.rs

@@ -356,6 +356,12 @@ mod tests {
                 .write_all(b"e\r\ndata: second\n\n\r\n0\r\n\r\n")
                 .await
                 .unwrap();
+            drop(socket);
+
+            // Close the next request without a response to trigger HTTP 502.
+            // Connecting to a closed port can outlast the deadline on Windows.
+            let (mut socket, _) = upstream.accept().await.unwrap();
+            read_request_headers(&mut socket).await;
         });
 
         // Use a local cleartext upstream to exercise the entire serving path.
@@ -433,11 +439,11 @@ mod tests {
                 .unwrap()
                 .contains("data: second")
         );
-        upstream_task.await.unwrap();
 
-        // The completed upstream listener is gone; errors become HTTP 502.
+        // The upstream closes without responding; errors become HTTP 502.
         let failed = client.get(&url).send().await.unwrap();
         assert_eq!(failed.status(), StatusCode::BAD_GATEWAY);
+        upstream_task.await.unwrap();
         stop.send(()).unwrap();
         tokio::time::timeout(Duration::from_secs(2), server)
             .await