Stabilize subagent and unified exec test fixtures (#43936)

## What changed

- Match parent follow-up responses by tool call IDs in the grandchild context baseline test, and assert that the grandchild completes with `done`.
- Drive delayed terminal output with newline-delimited stdin instead of sleeps, keeping the process alive across three `write_stdin` calls and updating the expected stdin events.

GitOrigin-RevId: 433954e5ed5ecce920cf198d1bf1264e58178ba6

codex-rs/core/tests/suite/subagent_notifications.rs

@@ -67,7 +67,10 @@ use tokio::time::sleep;
 use tokio::time::timeout;
 use tracing::Level;
 use tracing_test::internal::MockWriter;
+use wiremock::Mock;
 use wiremock::MockServer;
+use wiremock::matchers::method;
+use wiremock::matchers::path;
 
 const SPAWN_CALL_ID: &str = "spawn-call-1";
 const MULTI_AGENT_V1_NAMESPACE: &str = "multi_agent_v1";
@@ -1264,14 +1267,17 @@ async fn grandchild_full_fork_preserves_context_baseline(
         ]),
     )
     .await;
-    let _parent_followups = mount_sse_sequence(
-        &server,
-        vec![
-            sse(vec![ev_completed("baseline-parent-finished-1")]),
-            sse(vec![ev_completed("baseline-parent-finished-2")]),
-        ],
-    )
-    .await;
+    Mock::given(method("POST"))
+        .and(path("/v1/responses"))
+        .and(|req: &wiremock::Request| {
+            body_contains(req, ROOT_CALL) || body_contains(req, CHILD_CALL)
+        })
+        .respond_with(sse_response(sse(vec![ev_completed(
+            "baseline-parent-finished",
+        )])))
+        .with_priority(/*p*/ 6)
+        .mount(&server)
+        .await;
     let test = test_codex()
         .with_history_mode(history_mode)
         .with_config(move |config| {
@@ -1337,6 +1343,12 @@ async fn grandchild_full_fork_preserves_context_baseline(
             }
         })
         .await?;
+        if agent_name == "/root/child/grandchild" {
+            assert_eq!(
+                thread.agent_status().await,
+                AgentStatus::Completed(Some("done".to_string()))
+            );
+        }
         descendant_requests.push(request);
     }
     let context_counts = [

codex-rs/core/tests/suite/unified_exec.rs

@@ -1588,8 +1588,8 @@ async fn unified_exec_emits_terminal_interaction_for_write_stdin(
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn unified_exec_terminal_interaction_captures_delayed_output() -> Result<()> {
-    // TODO(anp): Remove after timing fixtures use target-native commands.
-    skip_if_target_windows!(Ok(()), "uses a POSIX sleep/echo timing fixture");
+    // TODO(anp): Remove after interactive fixtures use target-native commands.
+    skip_if_target_windows!(Ok(()), "uses a POSIX read/printf fixture");
     skip_if_no_network!(Ok(()));
     skip_if_sandbox!(Ok(()));
 
@@ -1600,30 +1600,30 @@ async fn unified_exec_terminal_interaction_captures_delayed_output() -> Result<(
 
     let open_call_id = "uexec-delayed-open";
     let open_args = json!({
-        "cmd": "sleep 3 && echo MARKER1 && sleep 3 && echo MARKER2",
+        "cmd": r#"/bin/sh -c 'read -r input && read -r input && printf "MARKER1\n" && read -r input && printf "MARKER2\n"'"#,
         "yield_time_ms": 10,
         "tty": true,
     });
 
-    // Poll stdin three times: first for no output, second after the first marker,
-    // and a final long poll to capture the second marker.
+    // The second and third input lines produce the markers. Waiting for the third
+    // line keeps the process alive across all three write_stdin calls.
     let first_poll_call_id = "uexec-delayed-poll-1";
     let first_poll_args = json!({
-        "chars": "x",
+        "chars": "x\n",
         "session_id": 1000,
         "yield_time_ms": 10,
     });
 
     let second_poll_call_id = "uexec-delayed-poll-2";
     let second_poll_args = json!({
-        "chars": "x",
+        "chars": "x\n",
         "session_id": 1000,
         "yield_time_ms": 4000,
     });
 
     let third_poll_call_id = "uexec-delayed-poll-3";
     let third_poll_args = json!({
-        "chars": "x",
+        "chars": "x\n",
         "session_id": 1000,
         "yield_time_ms": 6000,
     });
@@ -1734,7 +1734,7 @@ async fn unified_exec_terminal_interaction_captures_delayed_output() -> Result<(
             .iter()
             .map(|ev| ev.stdin.as_str())
             .collect::<Vec<_>>(),
-        vec!["x", "x", "x"],
+        vec!["x\n", "x\n", "x\n"],
         "terminal interactions should reflect the three stdin polls"
     );