From 10336068db594bdcf74b4a2512515ee412a071e5 Mon Sep 17 00:00:00 2001
From: Eric Traut <etraut@openai.com>
Date: Sat, 7 Feb 2026 08:55:42 -0800
Subject: [PATCH] Fix flaky windows CI test (#10993)

Hardens PTY Python REPL test and make MCP test startup deterministic

**Summary**
- `utils/pty/src/tests.rs`
- Added a REPL readiness handshake (`wait_for_python_repl_ready`) that
repeatedly sends a marker and waits for it in PTY output before sending
test commands.
  - Updated `pty_python_repl_emits_output_and_exits` to:
    - wait for readiness first,
    - preserve startup output,
    - append output collected through process exit.
- Reduces Windows/ConPTY flakiness from early stdin writes racing REPL
startup.

- `mcp-server/tests/suite/codex_tool.rs`
- Avoid remote model refresh during MCP test startup, reducing
timeout-prone nondeterminism.
---
 codex-rs/mcp-server/tests/suite/codex_tool.rs |  3 +
 codex-rs/utils/pty/src/tests.rs               | 60 ++++++++++++++++++-
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/codex-rs/mcp-server/tests/suite/codex_tool.rs b/codex-rs/mcp-server/tests/suite/codex_tool.rs
index edf2f1b02..c898b8f0d 100644
--- a/codex-rs/mcp-server/tests/suite/codex_tool.rs
+++ b/codex-rs/mcp-server/tests/suite/codex_tool.rs
@@ -505,6 +505,9 @@ base_url = "{server_uri}/v1"
 wire_api = "responses"
 request_max_retries = 0
 stream_max_retries = 0
+
+[features]
+remote_models = false
 "#
         ),
     )
diff --git a/codex-rs/utils/pty/src/tests.rs b/codex-rs/utils/pty/src/tests.rs
index 89e72eeb4..efbaaf6b8 100644
--- a/codex-rs/utils/pty/src/tests.rs
+++ b/codex-rs/utils/pty/src/tests.rs
@@ -93,6 +93,57 @@ async fn collect_output_until_exit(
     }
 }
 
+async fn wait_for_python_repl_ready(
+    writer: &tokio::sync::mpsc::Sender<Vec<u8>>,
+    output_rx: &mut tokio::sync::broadcast::Receiver<Vec<u8>>,
+    timeout_ms: u64,
+    newline: &str,
+) -> anyhow::Result<Vec<u8>> {
+    let mut collected = Vec::new();
+    let marker = "__codex_pty_ready__";
+    let deadline = tokio::time::Instant::now() + tokio::time::Duration::from_millis(timeout_ms);
+    let probe_window = tokio::time::Duration::from_millis(if cfg!(windows) { 750 } else { 250 });
+
+    while tokio::time::Instant::now() < deadline {
+        writer
+            .send(format!("print('{marker}'){newline}").into_bytes())
+            .await?;
+
+        let probe_deadline = tokio::time::Instant::now() + probe_window;
+        loop {
+            let now = tokio::time::Instant::now();
+            if now >= deadline || now >= probe_deadline {
+                break;
+            }
+            let remaining = std::cmp::min(
+                deadline.saturating_duration_since(now),
+                probe_deadline.saturating_duration_since(now),
+            );
+            match tokio::time::timeout(remaining, output_rx.recv()).await {
+                Ok(Ok(chunk)) => {
+                    collected.extend_from_slice(&chunk);
+                    if String::from_utf8_lossy(&collected).contains(marker) {
+                        return Ok(collected);
+                    }
+                }
+                Ok(Err(tokio::sync::broadcast::error::RecvError::Lagged(_))) => continue,
+                Ok(Err(tokio::sync::broadcast::error::RecvError::Closed)) => {
+                    anyhow::bail!(
+                        "PTY output closed while waiting for Python REPL readiness: {:?}",
+                        String::from_utf8_lossy(&collected)
+                    );
+                }
+                Err(_) => break,
+            }
+        }
+    }
+
+    anyhow::bail!(
+        "timed out waiting for Python REPL readiness in PTY: {:?}",
+        String::from_utf8_lossy(&collected)
+    );
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn pty_python_repl_emits_output_and_exits() -> anyhow::Result<()> {
     let Some(python) = find_python() else {
@@ -103,15 +154,20 @@ async fn pty_python_repl_emits_output_and_exits() -> anyhow::Result<()> {
     let env_map: HashMap<String, String> = std::env::vars().collect();
     let spawned = spawn_pty_process(&python, &[], Path::new("."), &env_map, &None).await?;
     let writer = spawned.session.writer_sender();
+    let mut output_rx = spawned.output_rx;
     let newline = if cfg!(windows) { "\r\n" } else { "\n" };
+    let startup_timeout_ms = if cfg!(windows) { 10_000 } else { 5_000 };
+    let mut output =
+        wait_for_python_repl_ready(&writer, &mut output_rx, startup_timeout_ms, newline).await?;
     writer
         .send(format!("print('hello from pty'){newline}").into_bytes())
         .await?;
     writer.send(format!("exit(){newline}").into_bytes()).await?;
 
     let timeout_ms = if cfg!(windows) { 10_000 } else { 5_000 };
-    let (output, code) =
-        collect_output_until_exit(spawned.output_rx, spawned.exit_rx, timeout_ms).await;
+    let (remaining_output, code) =
+        collect_output_until_exit(output_rx, spawned.exit_rx, timeout_ms).await;
+    output.extend_from_slice(&remaining_output);
     let text = String::from_utf8_lossy(&output);
 
     assert!(