From 32b1795ff4700c6d16bdea8d4a74c3c3262eee08 Mon Sep 17 00:00:00 2001
From: jif-oai <jif@openai.com>
Date: Wed, 14 Jan 2026 16:25:40 +0000
Subject: [PATCH] chore: clamp min yield time for empty write_stdin (#9156)

After evals, 0 impact on performance
---
 codex-rs/core/src/unified_exec/mod.rs             |  2 ++
 codex-rs/core/src/unified_exec/process_manager.rs | 11 ++++++++++-
 codex-rs/core/tests/suite/unified_exec.rs         |  8 ++++----
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/codex-rs/core/src/unified_exec/mod.rs b/codex-rs/core/src/unified_exec/mod.rs
index e84b63098..a30ba364c 100644
--- a/codex-rs/core/src/unified_exec/mod.rs
+++ b/codex-rs/core/src/unified_exec/mod.rs
@@ -45,6 +45,8 @@ pub(crate) use errors::UnifiedExecError;
 pub(crate) use process::UnifiedExecProcess;
 
 pub(crate) const MIN_YIELD_TIME_MS: u64 = 250;
+// Minimum yield time for an empty `write_stdin`.
+pub(crate) const MIN_EMPTY_YIELD_TIME_MS: u64 = 5_000;
 pub(crate) const MAX_YIELD_TIME_MS: u64 = 30_000;
 pub(crate) const DEFAULT_MAX_OUTPUT_TOKENS: usize = 10_000;
 pub(crate) const UNIFIED_EXEC_OUTPUT_MAX_BYTES: usize = 1024 * 1024; // 1 MiB
diff --git a/codex-rs/core/src/unified_exec/process_manager.rs b/codex-rs/core/src/unified_exec/process_manager.rs
index 80f0a4841..a50efeb70 100644
--- a/codex-rs/core/src/unified_exec/process_manager.rs
+++ b/codex-rs/core/src/unified_exec/process_manager.rs
@@ -26,6 +26,8 @@ use crate::truncate::approx_token_count;
 use crate::truncate::formatted_truncate_text;
 use crate::unified_exec::ExecCommandRequest;
 use crate::unified_exec::MAX_UNIFIED_EXEC_PROCESSES;
+use crate::unified_exec::MAX_YIELD_TIME_MS;
+use crate::unified_exec::MIN_EMPTY_YIELD_TIME_MS;
 use crate::unified_exec::ProcessEntry;
 use crate::unified_exec::ProcessStore;
 use crate::unified_exec::UnifiedExecContext;
@@ -263,7 +265,14 @@ impl UnifiedExecProcessManager {
         }
 
         let max_tokens = resolve_max_tokens(request.max_output_tokens);
-        let yield_time_ms = clamp_yield_time(request.yield_time_ms);
+        let yield_time_ms = {
+            let time_ms = clamp_yield_time(request.yield_time_ms);
+            if request.input.is_empty() {
+                time_ms.clamp(MIN_EMPTY_YIELD_TIME_MS, MAX_YIELD_TIME_MS)
+            } else {
+                time_ms
+            }
+        };
         let start = Instant::now();
         let deadline = start + Duration::from_millis(yield_time_ms);
         let collected = Self::collect_output_until_deadline(
diff --git a/codex-rs/core/tests/suite/unified_exec.rs b/codex-rs/core/tests/suite/unified_exec.rs
index 2e2fd34e6..1bb4ba8ad 100644
--- a/codex-rs/core/tests/suite/unified_exec.rs
+++ b/codex-rs/core/tests/suite/unified_exec.rs
@@ -902,21 +902,21 @@ async fn unified_exec_terminal_interaction_captures_delayed_output() -> Result<(
     // and a final long poll to capture the second marker.
     let first_poll_call_id = "uexec-delayed-poll-1";
     let first_poll_args = json!({
-        "chars": "",
+        "chars": "x",
         "session_id": 1000,
         "yield_time_ms": 10,
     });
 
     let second_poll_call_id = "uexec-delayed-poll-2";
     let second_poll_args = json!({
-        "chars": "",
+        "chars": "x",
         "session_id": 1000,
         "yield_time_ms": 4000,
     });
 
     let third_poll_call_id = "uexec-delayed-poll-3";
     let third_poll_args = json!({
-        "chars": "",
+        "chars": "x",
         "session_id": 1000,
         "yield_time_ms": 6000,
     });
@@ -1037,7 +1037,7 @@ async fn unified_exec_terminal_interaction_captures_delayed_output() -> Result<(
             .iter()
             .map(|ev| ev.stdin.as_str())
             .collect::<Vec<_>>(),
-        vec!["", "", ""],
+        vec!["x", "x", "x"],
         "terminal interactions should reflect the three stdin polls"
     );