Use the async stack budget for approval reviews (#41840)

## What changed

- Define the shared 16 MiB thread stack budget in `codex-async-utils`.
- Use it for both the async main/runtime threads and the dedicated approval-review thread.

GitOrigin-RevId: c825669e1545bcfaeaaaa07066dc63874f46630f

codex-rs/Cargo.lock

@@ -2271,6 +2271,7 @@ version = "0.0.0"
 dependencies = [
  "anyhow",
  "codex-apply-patch",
+ "codex-async-utils",
  "codex-exec-server",
  "codex-install-context",
  "codex-linux-sandbox",

codex-rs/arg0/Cargo.toml

@@ -15,6 +15,7 @@ workspace = true
 [dependencies]
 anyhow = { workspace = true }
 codex-apply-patch = { workspace = true }
+codex-async-utils = { workspace = true }
 codex-exec-server = { workspace = true }
 codex-install-context = { workspace = true }
 codex-linux-sandbox = { workspace = true }

codex-rs/arg0/src/lib.rs

@@ -5,6 +5,7 @@ use std::path::Path;
 use std::path::PathBuf;
 
 use codex_apply_patch::CODEX_CORE_APPLY_PATCH_ARG1;
+use codex_async_utils::THREAD_STACK_SIZE_BYTES;
 #[cfg(unix)]
 use codex_exec_server::CODEX_ARG0_EXEC_HELPER_ARG1;
 use codex_exec_server::CODEX_FS_HELPER_ARG1;
@@ -22,7 +23,6 @@ const MISSPELLED_APPLY_PATCH_ARG0: &str = "applypatch";
 #[cfg(unix)]
 const EXECVE_WRAPPER_ARG0: &str = "codex-execve-wrapper";
 const LOCK_FILENAME: &str = ".lock";
-const TOKIO_WORKER_STACK_SIZE_BYTES: usize = 16 * 1024 * 1024;
 
 #[derive(Clone, Debug, Default, Eq, PartialEq)]
 pub struct Arg0DispatchPaths {
@@ -232,7 +232,7 @@ where
     // top-level future on the caller's OS stack.
     let handle = std::thread::Builder::new()
         .name("codex-main".to_string())
-        .stack_size(TOKIO_WORKER_STACK_SIZE_BYTES)
+        .stack_size(THREAD_STACK_SIZE_BYTES)
         .spawn(move || {
             let runtime = build_runtime()?;
             runtime.block_on(run_main_with_arg0_guard(
@@ -290,7 +290,7 @@ fn linux_sandbox_exe_path(
 fn build_runtime() -> anyhow::Result<tokio::runtime::Runtime> {
     let mut builder = tokio::runtime::Builder::new_multi_thread();
     builder.enable_all();
-    builder.thread_stack_size(TOKIO_WORKER_STACK_SIZE_BYTES);
+    builder.thread_stack_size(THREAD_STACK_SIZE_BYTES);
     Ok(builder.build()?)
 }
 

codex-rs/async-utils/src/lib.rs

@@ -1,6 +1,9 @@
 use std::future::Future;
 use tokio_util::sync::CancellationToken;
 
+/// Stack budget for threads that poll Codex async work.
+pub const THREAD_STACK_SIZE_BYTES: usize = 16 * 1024 * 1024;
+
 #[derive(Debug, PartialEq, Eq)]
 pub enum CancelErr {
     Cancelled,

codex-rs/core/src/guardian/review.rs

@@ -5,6 +5,7 @@ use codex_analytics::GuardianReviewFailureReason;
 use codex_analytics::GuardianReviewTerminalStatus;
 use codex_analytics::GuardianReviewTrackContext;
 use codex_analytics::GuardianReviewedAction;
+use codex_async_utils::THREAD_STACK_SIZE_BYTES;
 use codex_core_plugins::PluginCommandAttribution;
 use codex_extension_api::ThreadIdleCause;
 use codex_features::Feature;
@@ -806,6 +807,7 @@ pub(crate) fn spawn_approval_request_review(
     let runtime = session.services.runtime_handle.clone();
     let spawn_result = std::thread::Builder::new()
         .name("codex-approval-review".to_string())
+        .stack_size(THREAD_STACK_SIZE_BYTES)
         .spawn(move || {
             let decision = runtime.block_on(run_guardian_review(
                 session, context, review_id, request, reasons, options,