core: mark auto-compaction fallback requests

codex-rs/core/src/auto_compact_fallback.rs

@@ -65,7 +65,7 @@ pub(crate) async fn run_auto_compact_fallback(
     let responses_metadata = restricted_turn.turn_metadata_state.to_responses_metadata(
         sess.installation_id.clone(),
         window_id,
-        CodexResponsesRequestKind::Turn,
+        CodexResponsesRequestKind::AutoCompactFallback,
     );
     let input = sess
         .clone_history()

codex-rs/core/src/responses_metadata.rs

@@ -114,6 +114,7 @@ impl CompactionTurnMetadata {
 #[derive(Clone, Copy, Debug)]
 pub(crate) enum CodexResponsesRequestKind {
     Turn,
+    AutoCompactFallback,
     Prewarm,
     Compaction(CompactionTurnMetadata),
     Memory,
@@ -123,6 +124,7 @@ impl CodexResponsesRequestKind {
     fn metadata(self) -> (&'static str, Option<CompactionTurnMetadata>) {
         match self {
             CodexResponsesRequestKind::Turn => ("turn", None),
+            CodexResponsesRequestKind::AutoCompactFallback => ("auto_compact_fallback", None),
             CodexResponsesRequestKind::Prewarm => ("prewarm", None),
             CodexResponsesRequestKind::Compaction(metadata) => ("compaction", Some(metadata)),
             CodexResponsesRequestKind::Memory => ("memory", None),

codex-rs/core/src/turn_metadata_tests.rs

@@ -736,6 +736,18 @@ fn turn_metadata_state_overlays_compaction_only_on_compaction_requests() {
     assert_eq!(regular_json["request_kind"].as_str(), Some("turn"));
     assert_eq!(regular_json[WINDOW_ID_KEY].as_str(), Some("thread-a:3"));
     assert!(regular_json.get("compaction").is_none());
+
+    let fallback_header = test_responses_metadata_json(
+        &state,
+        "thread-a:3",
+        CodexResponsesRequestKind::AutoCompactFallback,
+    );
+    let fallback_json: Value = serde_json::from_str(&fallback_header).expect("json");
+    assert_eq!(
+        fallback_json["request_kind"].as_str(),
+        Some("auto_compact_fallback")
+    );
+    assert!(fallback_json.get("compaction").is_none());
 }
 
 #[tokio::test]