Move retry backoff into codex-async-utils (#46330)

Move the exponential backoff helper into `codex-async-utils` so
`codex-cloud-config` can use it without a runtime dependency on `codex-core`.
Keep `codex-core` as a development dependency for cloud-config tests.

Preserve the existing retry delays and jitter, and re-export `backoff` from
`codex_core::util` for existing callers.

GitOrigin-RevId: 338f3194e166e77003da532310ff5be78a0eac9e

codex-rs/Cargo.lock

@@ -2478,6 +2478,7 @@ name = "codex-async-utils"
 version = "0.0.0"
 dependencies = [
  "pretty_assertions",
+ "rand 0.9.3",
  "tokio",
  "tokio-util",
 ]
@@ -2696,6 +2697,7 @@ dependencies = [
  "base64 0.22.1",
  "chrono",
  "codex-agent-identity",
+ "codex-async-utils",
  "codex-backend-client",
  "codex-config",
  "codex-core",

codex-rs/async-utils/Cargo.toml

@@ -8,6 +8,7 @@ license.workspace = true
 workspace = true
 
 [dependencies]
+rand = { workspace = true }
 tokio = { workspace = true, features = ["macros", "rt", "rt-multi-thread", "time"] }
 tokio-util.workspace = true
 

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

@@ -0,0 +1,17 @@
+//! Shared exponential retry delays with jitter.
+
+use std::time::Duration;
+
+use rand::Rng;
+
+const INITIAL_DELAY_MS: u64 = 200;
+const BACKOFF_FACTOR: f64 = 2.0;
+
+/// Return a retry delay starting at 200 ms and doubling on each subsequent attempt,
+/// with up to 10% jitter. Attempts zero and one both use the initial delay.
+pub fn backoff(attempt: u64) -> Duration {
+    let exp = BACKOFF_FACTOR.powi(attempt.saturating_sub(1) as i32);
+    let base = (INITIAL_DELAY_MS as f64 * exp) as u64;
+    let jitter = rand::rng().random_range(0.9..1.1);
+    Duration::from_millis((base as f64 * jitter) as u64)
+}

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

@@ -1,3 +1,7 @@
+mod backoff;
+
+pub use backoff::backoff;
+
 use std::future::Future;
 use tokio_util::sync::CancellationToken;
 

codex-rs/cloud-config/Cargo.toml

@@ -10,10 +10,10 @@ workspace = true
 [dependencies]
 base64 = { workspace = true }
 chrono = { workspace = true, features = ["serde"] }
+codex-async-utils = { workspace = true }
 codex-backend-client = { workspace = true }
 codex-config = { workspace = true }
 codex-http-client = { workspace = true }
-codex-core = { workspace = true }
 codex-login = { workspace = true }
 codex-otel = { workspace = true }
 codex-protocol = { workspace = true }
@@ -27,6 +27,7 @@ tracing = { workspace = true }
 
 [dev-dependencies]
 codex-agent-identity = { workspace = true }
+codex-core = { workspace = true }
 pretty_assertions = { workspace = true }
 tempfile = { workspace = true }
 tokio = { workspace = true, features = ["macros", "rt", "test-util", "time"] }

codex-rs/cloud-config/src/service.rs

@@ -13,11 +13,11 @@ use crate::metrics::emit_fetch_attempt_metric;
 use crate::metrics::emit_fetch_final_metric;
 use crate::metrics::emit_load_metric;
 use crate::validation::validate_bundle;
+use codex_async_utils::backoff;
 use codex_config::AbsolutePathBuf;
 use codex_config::CloudConfigBundle;
 use codex_config::CloudConfigBundleLoadError;
 use codex_config::CloudConfigBundleLoadErrorCode;
-use codex_core::util::backoff;
 use codex_login::AuthManager;
 use codex_login::CodexAuth;
 use codex_login::RefreshTokenError;

codex-rs/core/src/util.rs

@@ -1,11 +1,6 @@
-use std::time::Duration;
-
-use rand::Rng;
+pub use codex_async_utils::backoff;
 use tracing::error;
 
-const INITIAL_DELAY_MS: u64 = 200;
-const BACKOFF_FACTOR: f64 = 2.0;
-
 /// Emit structured feedback metadata as key/value pairs.
 ///
 /// This logs a tracing event with `target: "feedback_tags"`. If
@@ -83,13 +78,6 @@ pub(crate) fn emit_feedback_auth_recovery_tags(
     );
 }
 
-pub fn backoff(attempt: u64) -> Duration {
-    let exp = BACKOFF_FACTOR.powi(attempt.saturating_sub(1) as i32);
-    let base = (INITIAL_DELAY_MS as f64 * exp) as u64;
-    let jitter = rand::rng().random_range(0.9..1.1);
-    Duration::from_millis((base as f64 * jitter) as u64)
-}
-
 pub(crate) fn error_or_panic(message: impl std::string::ToString) {
     if cfg!(debug_assertions) {
         panic!("{}", message.to_string());