Make unbounded connection retries configurable (#38601)

## What changed

- Add the stable, default-enabled `unbounded_connection_retries` feature.
- Require the feature for unbounded sampling retries after connection failures.
  When disabled, connection failures use the existing bounded retry and
  transport fallback path.
- Expose the feature in the generated configuration schema.

GitOrigin-RevId: bd80d02ef065ba924f805c29b639752fc817ed64

codex-rs/core/config.schema.json

@@ -777,6 +777,9 @@
             "unavailable_dummy_tools": {
               "type": "boolean"
             },
+            "unbounded_connection_retries": {
+              "type": "boolean"
+            },
             "undo": {
               "type": "boolean"
             },
@@ -5434,6 +5437,9 @@
         "unavailable_dummy_tools": {
           "type": "boolean"
         },
+        "unbounded_connection_retries": {
+          "type": "boolean"
+        },
         "undo": {
           "type": "boolean"
         },

codex-rs/core/src/responses_retry.rs

@@ -7,6 +7,7 @@ use crate::session::session::Session;
 use crate::session::turn_context::TurnContext;
 use crate::util::backoff;
 use codex_client::RetryOperation;
+use codex_features::Feature;
 use codex_protocol::error::CodexErr;
 use codex_protocol::error::CodexErrorDetails;
 use codex_protocol::protocol::EventMsg;
@@ -54,7 +55,11 @@ pub(crate) async fn handle_retryable_response_stream_error(
         ResponsesStreamRequest::RemoteCompactionV2 => RetryOperation::RemoteCompactionV2,
     };
 
-    if matches!(request, ResponsesStreamRequest::Sampling)
+    if turn_context
+        .config
+        .features
+        .enabled(Feature::UnboundedConnectionRetries)
+        && matches!(request, ResponsesStreamRequest::Sampling)
         && matches!(err.details(), CodexErrorDetails::ConnectionFailed(_))
         && !turn_context.session_source.is_internal()
         && !turn_context.provider.info().is_amazon_bedrock()

codex-rs/features/src/lib.rs

@@ -157,6 +157,8 @@ pub enum Feature {
     Chronicle,
     /// Compress request bodies (zstd) when sending streaming requests to codex-backend.
     EnableRequestCompression,
+    /// Keep active sampling turns alive until a failed network connection recovers.
+    UnboundedConnectionRetries,
     /// Start the managed network proxy for sandboxed sessions.
     NetworkProxy,
     /// Respect host system proxy settings for Codex-owned network clients.
@@ -1054,6 +1056,12 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::Stable,
         default_enabled: true,
     },
+    FeatureSpec {
+        id: Feature::UnboundedConnectionRetries,
+        key: "unbounded_connection_retries",
+        stage: Stage::Stable,
+        default_enabled: true,
+    },
     FeatureSpec {
         id: Feature::NetworkProxy,
         key: "network_proxy",