From 8a400e7812b0c7488a2bf7963741dceb1aa2e693 Mon Sep 17 00:00:00 2001
From: jif <jif@openai.com>
Date: Thu, 1 Oct 2026 10:52:28 +0000
Subject: [PATCH] Cache the placeholder regex for MCP hook argument expansion
 (#49956)

Use `LazyLock` to compile the placeholder regex once and reuse it across
argument strings, avoiding repeated compilation during template expansion.
Preserve regex error propagation and placeholder substitution behavior.

GitOrigin-RevId: 2ac8aec86de3430335c068e47d09422dcd276f7c
---
 codex-rs/hooks/src/engine/mcp_runner.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/codex-rs/hooks/src/engine/mcp_runner.rs b/codex-rs/hooks/src/engine/mcp_runner.rs
index 7a8da53e4d..71bf050e0f 100644
--- a/codex-rs/hooks/src/engine/mcp_runner.rs
+++ b/codex-rs/hooks/src/engine/mcp_runner.rs
@@ -1,3 +1,4 @@
+use std::sync::LazyLock;
 use std::time::Duration;
 use std::time::Instant;
 
@@ -121,7 +122,9 @@ fn resolve_value(value: &Value, hook_event: &Value) -> Result<Value> {
 }
 
 fn resolve_string(text: &str, hook_event: &Value) -> Result<Value> {
-    let pattern = Regex::new(r"\$\{([^{}]+)\}")?;
+    static PLACEHOLDER_PATTERN: LazyLock<Result<Regex, regex::Error>> =
+        LazyLock::new(|| Regex::new(r"\$\{([^{}]+)\}"));
+    let pattern = PLACEHOLDER_PATTERN.as_ref().map_err(Clone::clone)?;
     let captures = pattern.captures_iter(text).collect::<Vec<_>>();
     if captures.is_empty() {
         return Ok(Value::String(text.to_string()));