diff --git a/codex-rs/app-server/tests/suite/v2/thread_inject_items.rs b/codex-rs/app-server/tests/suite/v2/thread_inject_items.rs
index 14acdf7be9..9ec91072dc 100644
--- a/codex-rs/app-server/tests/suite/v2/thread_inject_items.rs
+++ b/codex-rs/app-server/tests/suite/v2/thread_inject_items.rs
@@ -16,6 +16,8 @@ use codex_protocol::models::ResponseItem;
 use codex_protocol::protocol::InitialHistory;
 use codex_protocol::protocol::RolloutItem;
 use core_test_support::responses;
+use core_test_support::responses::strip_response_item_id;
+use core_test_support::responses::strip_response_item_ids_from_json;
 use serde_json::Value;
 use std::path::Path;
 use tempfile::TempDir;
@@ -89,7 +91,7 @@ async fn thread_inject_items_adds_raw_response_items_to_thread_history() -> Resu
         resumed_history
             .history
             .iter()
-            .any(|item| matches!(item, RolloutItem::ResponseItem(response_item) if responses::strip_metadata(response_item.clone()) == injected_item)),
+            .any(|item| matches!(item, RolloutItem::ResponseItem(response_item) if strip_response_item_id(responses::strip_metadata(response_item.clone())) == injected_item)),
         "injected item should be persisted in rollout history"
     );
 
@@ -116,7 +118,12 @@ async fn thread_inject_items_adds_raw_response_items_to_thread_history() -> Resu
     .await??;
 
     let injected_value = serde_json::to_value(&injected_item)?;
-    let model_input = response_mock.single_request().input();
+    let model_input: Vec<Value> = response_mock
+        .single_request()
+        .input()
+        .into_iter()
+        .map(strip_response_item_ids_from_json)
+        .collect();
     let environment_context_index =
         response_item_text_position(&model_input, "<environment_context>")
             .expect("environment context should be injected before the first user turn");
@@ -247,11 +254,19 @@ async fn thread_inject_items_adds_raw_response_items_after_a_turn() -> Result<()
     let requests = response_mock.requests();
     assert_eq!(requests.len(), 2);
     assert!(
-        !requests[0].input().contains(&injected_value),
+        !requests[0]
+            .input()
+            .into_iter()
+            .map(strip_response_item_ids_from_json)
+            .any(|item| item == injected_value),
         "injected item should not be sent before it is injected"
     );
     assert!(
-        requests[1].input().contains(&injected_value),
+        requests[1]
+            .input()
+            .into_iter()
+            .map(strip_response_item_ids_from_json)
+            .any(|item| item == injected_value),
         "injected item should be sent after being injected into existing history"
     );
 
diff --git a/codex-rs/app-server/tests/suite/v2/web_search.rs b/codex-rs/app-server/tests/suite/v2/web_search.rs
index 0327c65d53..f4893d3a1c 100644
--- a/codex-rs/app-server/tests/suite/v2/web_search.rs
+++ b/codex-rs/app-server/tests/suite/v2/web_search.rs
@@ -24,6 +24,7 @@ use codex_app_server_protocol::WebSearchAction;
 use codex_app_server_protocol::WebSearchItem;
 use codex_config::types::AuthCredentialsStoreMode;
 use core_test_support::responses;
+use core_test_support::responses::strip_response_item_ids_from_json;
 use pretty_assertions::assert_eq;
 use serde_json::Value;
 use serde_json::json;
@@ -228,7 +229,9 @@ async fn standalone_web_search_round_trips_output() -> Result<()> {
     );
 
     assert_eq!(
-        responses::strip_metadata_from_json(requests[1].function_call_output(call_id)),
+        strip_response_item_ids_from_json(responses::strip_metadata_from_json(
+            requests[1].function_call_output(call_id),
+        )),
         json!({
             "type": "function_call_output",
             "call_id": call_id,
diff --git a/codex-rs/cli/src/main.rs b/codex-rs/cli/src/main.rs
index 8d52a6282b..20244f896e 100644
--- a/codex-rs/cli/src/main.rs
+++ b/codex-rs/cli/src/main.rs
@@ -4133,6 +4133,16 @@ mod tests {
         assert_eq!(overrides, vec!["features.enable_fanout=true".to_string(),]);
     }
 
+    #[test]
+    fn feature_toggles_accept_removed_item_ids_flag() {
+        let toggles = FeatureToggles {
+            enable: vec!["item_ids".to_string()],
+            disable: Vec::new(),
+        };
+        let overrides = toggles.to_overrides().expect("valid features");
+        assert_eq!(overrides, vec!["features.item_ids=true".to_string()]);
+    }
+
     #[test]
     fn feature_toggles_unknown_feature_errors() {
         let toggles = FeatureToggles {
diff --git a/codex-rs/core/src/agent/control_tests.rs b/codex-rs/core/src/agent/control_tests.rs
index 6d4cbc7ebd..32b93d00bd 100644
--- a/codex-rs/core/src/agent/control_tests.rs
+++ b/codex-rs/core/src/agent/control_tests.rs
@@ -56,6 +56,7 @@ use codex_thread_store::LocalThreadStore;
 use codex_thread_store::LocalThreadStoreConfig;
 use codex_thread_store::ThreadStore;
 use codex_utils_path_uri::PathUri;
+use core_test_support::responses::strip_response_item_ids;
 use pretty_assertions::assert_eq;
 use tempfile::TempDir;
 use tokio::time::Duration;
@@ -1340,8 +1341,8 @@ async fn spawn_agent_can_fork_parent_thread_history_with_sanitized_items() {
         },
     ];
     assert_eq!(
-        history.raw_items(),
-        &expected_history,
+        strip_response_item_ids(history.raw_items()),
+        strip_response_item_ids(&expected_history),
         "full-history forked child history should replace parent usage hints with the child subagent hint while filtering non-final assistant/tool chatter"
     );
     assert_eq!(
diff --git a/codex-rs/core/src/client.rs b/codex-rs/core/src/client.rs
index 7dde771cf7..025796de6a 100644
--- a/codex-rs/core/src/client.rs
+++ b/codex-rs/core/src/client.rs
@@ -207,7 +207,6 @@ struct ModelClientState {
     enable_request_compression: bool,
     include_timing_metrics: bool,
     beta_features_header: Option<String>,
-    item_ids_enabled: bool,
     concurrent_reasoning_summaries_enabled: bool,
     include_attestation: bool,
     attestation_provider: Option<Arc<dyn AttestationProvider>>,
@@ -421,7 +420,6 @@ impl ModelClient {
         enable_request_compression: bool,
         include_timing_metrics: bool,
         beta_features_header: Option<String>,
-        item_ids_enabled: bool,
         concurrent_reasoning_summaries_enabled: bool,
         attestation_provider: Option<Arc<dyn AttestationProvider>>,
         http_client_factory: HttpClientFactory,
@@ -445,7 +443,6 @@ impl ModelClient {
                 enable_request_compression,
                 include_timing_metrics,
                 beta_features_header,
-                item_ids_enabled,
                 concurrent_reasoning_summaries_enabled,
                 include_attestation,
                 attestation_provider,
@@ -583,7 +580,7 @@ impl ModelClient {
             text,
             ..
         } = request;
-        self.prepare_response_items_for_request(&mut input, /*store*/ false);
+        self.prepare_response_items_for_request(&mut input);
         let payload = ApiCompactionInput {
             model: &model,
             input: &input,
@@ -908,20 +905,12 @@ impl ModelClient {
         Ok(request)
     }
 
-    fn prepare_response_items_for_request(&self, input: &mut [ResponseItem], store: bool) {
-        for item in input.iter_mut() {
+    fn prepare_response_items_for_request(&self, input: &mut [ResponseItem]) {
+        for item in input {
             if item.id().is_some_and(|id| !id.is_prefixed()) {
                 item.set_id(/*new_id*/ None);
             }
         }
-
-        if self.state.item_ids_enabled || store {
-            return;
-        }
-
-        for item in input {
-            item.set_id(/*new_id*/ None);
-        }
     }
 
     /// Returns whether the Responses-over-WebSocket transport is active for this session.
@@ -1439,9 +1428,8 @@ impl ModelClientSession {
                 service_tier.clone(),
                 responses_metadata,
             )?;
-            let store = request.store;
             self.client
-                .prepare_response_items_for_request(&mut request.input, store);
+                .prepare_response_items_for_request(&mut request.input);
             let request_session_telemetry =
                 session_telemetry_for_request(session_telemetry, &request);
             let inference_trace_attempt = inference_trace.start_attempt();
@@ -1620,10 +1608,9 @@ impl ModelClientSession {
                 Some((response_id, items)) => (Some(response_id), Some(items)),
                 None => (None, None),
             };
-            let store = request.store;
             let original_item_ids = if let Some(incremental_items) = &mut incremental_items {
                 self.client
-                    .prepare_response_items_for_request(incremental_items, store);
+                    .prepare_response_items_for_request(incremental_items);
                 None
             } else {
                 let original_item_ids = request
@@ -1632,7 +1619,7 @@ impl ModelClientSession {
                     .map(|item| item.id().cloned())
                     .collect::<Vec<_>>();
                 self.client
-                    .prepare_response_items_for_request(&mut request.input, store);
+                    .prepare_response_items_for_request(&mut request.input);
                 Some(original_item_ids)
             };
             let ws_payload = ResponseCreateWsRequest {
diff --git a/codex-rs/core/src/client_tests.rs b/codex-rs/core/src/client_tests.rs
index 3f33aff1a5..fb7c4f6136 100644
--- a/codex-rs/core/src/client_tests.rs
+++ b/codex-rs/core/src/client_tests.rs
@@ -104,7 +104,6 @@ fn test_model_client_with_thread_id(
         /*enable_request_compression*/ false,
         /*include_timing_metrics*/ false,
         /*beta_features_header*/ None,
-        /*item_ids_enabled*/ false,
         /*concurrent_reasoning_summaries_enabled*/ false,
         /*attestation_provider*/ None,
         HttpClientFactory::new(OutboundProxyPolicy::ReqwestDefault),
@@ -150,7 +149,6 @@ async fn compact_uses_bearer_after_agent_identity_session_fallback() -> anyhow::
         /*enable_request_compression*/ false,
         /*include_timing_metrics*/ false,
         /*beta_features_header*/ None,
-        /*item_ids_enabled*/ false,
         /*concurrent_reasoning_summaries_enabled*/ false,
         /*attestation_provider*/ None,
         HttpClientFactory::new(OutboundProxyPolicy::ReqwestDefault),
@@ -825,7 +823,6 @@ fn model_client_with_counting_attestation(
         /*enable_request_compression*/ false,
         /*include_timing_metrics*/ false,
         /*beta_features_header*/ None,
-        /*item_ids_enabled*/ false,
         /*concurrent_reasoning_summaries_enabled*/ false,
         Some(Arc::new(CountingAttestationProvider {
             calls: attestation_calls.clone(),
diff --git a/codex-rs/core/src/compact.rs b/codex-rs/core/src/compact.rs
index e69655c5ba..4e777fb9ff 100644
--- a/codex-rs/core/src/compact.rs
+++ b/codex-rs/core/src/compact.rs
@@ -368,7 +368,6 @@ async fn run_compact_task_inner_impl(
         }
     };
     sess.replace_compacted_history(
-        turn_context.as_ref(),
         new_history,
         reference_context_item,
         world_state_baseline,
diff --git a/codex-rs/core/src/compact_remote.rs b/codex-rs/core/src/compact_remote.rs
index 91716ff78e..09d54b75d1 100644
--- a/codex-rs/core/src/compact_remote.rs
+++ b/codex-rs/core/src/compact_remote.rs
@@ -279,7 +279,6 @@ async fn run_remote_compact_task_inner_impl(
         });
     }
     sess.replace_compacted_history(
-        compaction_turn_context.as_ref(),
         new_history,
         reference_context_item,
         world_state_baseline,
diff --git a/codex-rs/core/src/compact_remote_v2.rs b/codex-rs/core/src/compact_remote_v2.rs
index 86b827731d..db79083c72 100644
--- a/codex-rs/core/src/compact_remote_v2.rs
+++ b/codex-rs/core/src/compact_remote_v2.rs
@@ -300,7 +300,6 @@ async fn run_remote_compact_task_inner_impl(
         });
     }
     sess.replace_compacted_history(
-        compaction_turn_context.as_ref(),
         new_history,
         reference_context_item,
         world_state_baseline,
diff --git a/codex-rs/core/src/session/mod.rs b/codex-rs/core/src/session/mod.rs
index 88cac6dc9d..96aed20dd0 100644
--- a/codex-rs/core/src/session/mod.rs
+++ b/codex-rs/core/src/session/mod.rs
@@ -1324,9 +1324,7 @@ impl Session {
             }
             InitialHistory::Forked(mut rollout_items) => {
                 let turn_context = self.new_default_turn().await;
-                if turn_context.item_ids_enabled() {
-                    Self::assign_missing_rollout_response_item_ids(&mut rollout_items);
-                }
+                Self::assign_missing_rollout_response_item_ids(&mut rollout_items);
                 self.apply_rollout_reconstruction(&turn_context, &rollout_items)
                     .await;
 
@@ -2807,11 +2805,7 @@ impl Session {
         for item in items.to_mut() {
             item.set_turn_id_if_missing(&turn_context.sub_id);
         }
-        if turn_context.item_ids_enabled() {
-            Self::assign_missing_response_item_ids(items)
-        } else {
-            items
-        }
+        Self::assign_missing_response_item_ids(items)
     }
 
     fn assign_missing_response_item_ids(items: Cow<'_, [ResponseItem]>) -> Cow<'_, [ResponseItem]> {
@@ -3057,17 +3051,12 @@ impl Session {
 
     pub(crate) async fn replace_compacted_history(
         &self,
-        turn_context: &TurnContext,
         items: Vec<ResponseItem>,
         reference_context_item: Option<TurnContextItem>,
         world_state_baseline: Option<Arc<WorldState>>,
         metadata: CompactedHistoryMetadata,
     ) {
-        let items = if turn_context.item_ids_enabled() {
-            Self::assign_missing_response_item_ids(Cow::Owned(items)).into_owned()
-        } else {
-            items
-        };
+        let items = Self::assign_missing_response_item_ids(Cow::Owned(items)).into_owned();
         let compacted_item = CompactedItem {
             message: metadata.message,
             replacement_history: Some(items.clone()),
@@ -3556,7 +3545,6 @@ impl Session {
             .await;
         let turn_context_item = turn_context.to_turn_context_item();
         self.replace_compacted_history(
-            turn_context,
             context_items,
             Some(turn_context_item),
             Some(world_state),
diff --git a/codex-rs/core/src/session/session.rs b/codex-rs/core/src/session/session.rs
index 89cb0c8d9f..87d635b736 100644
--- a/codex-rs/core/src/session/session.rs
+++ b/codex-rs/core/src/session/session.rs
@@ -522,13 +522,7 @@ impl Session {
             session_configuration.thread_source.as_ref(),
             Some(ThreadSource::Subagent)
         );
-        if (config.features.enabled(Feature::ItemIds)
-            || matches!(
-                session_configuration.history_mode,
-                ThreadHistoryMode::Paginated
-            ))
-            && let InitialHistory::Forked(items) = &mut initial_history
-        {
+        if let InitialHistory::Forked(items) = &mut initial_history {
             Self::assign_missing_rollout_response_item_ids(items);
         }
         let multi_agent_version = multi_agent_version.map(OnceLock::from).unwrap_or_default();
@@ -1120,11 +1114,6 @@ impl Session {
                     config.features.enabled(Feature::EnableRequestCompression),
                     config.features.enabled(Feature::RuntimeMetrics),
                     Self::build_model_client_beta_features_header(config.as_ref()),
-                    /*item_ids_enabled*/ config.features.enabled(Feature::ItemIds)
-                        || matches!(
-                            session_configuration.history_mode,
-                            ThreadHistoryMode::Paginated
-                        ),
                     /*concurrent_reasoning_summaries_enabled*/ config
                         .features
                         .enabled(Feature::ConcurrentReasoningSummaries),
diff --git a/codex-rs/core/src/session/tests.rs b/codex-rs/core/src/session/tests.rs
index 55babc759f..b2d13e4cf7 100644
--- a/codex-rs/core/src/session/tests.rs
+++ b/codex-rs/core/src/session/tests.rs
@@ -67,7 +67,6 @@ use codex_protocol::permissions::FileSystemSandboxPolicy;
 use codex_protocol::permissions::FileSystemSpecialPath;
 use codex_protocol::protocol::NonSteerableTurnKind;
 use codex_protocol::protocol::SandboxPolicy;
-use codex_protocol::protocol::ThreadHistoryMode;
 use codex_protocol::protocol::TurnEnvironmentSelections;
 use codex_protocol::request_permissions::PermissionGrantScope;
 use codex_protocol::request_permissions::RequestPermissionProfile;
@@ -163,6 +162,8 @@ use core_test_support::responses::mount_sse_once;
 use core_test_support::responses::sse;
 use core_test_support::responses::start_mock_server;
 use core_test_support::responses::strip_metadata_from_items;
+use core_test_support::responses::strip_response_item_ids;
+use core_test_support::responses::strip_response_item_ids_from_json;
 use core_test_support::test_codex::local;
 use core_test_support::test_codex::test_codex;
 use core_test_support::test_path_buf;
@@ -261,9 +262,8 @@ fn assign_missing_response_item_ids_assigns_additional_tools_ids() {
 }
 
 #[tokio::test]
-async fn paginated_turn_context_assigns_missing_response_item_ids_without_feature() {
-    let (session, mut turn_context) = make_session_and_context().await;
-    turn_context.history_mode = ThreadHistoryMode::Paginated;
+async fn default_turn_context_assigns_missing_response_item_ids() {
+    let (session, turn_context) = make_session_and_context().await;
     let response_item = user_message("hello");
 
     let items = session.prepare_conversation_items_for_history(
@@ -516,7 +516,6 @@ fn test_model_client_session() -> crate::client::ModelClientSession {
         /*enable_request_compression*/ false,
         /*include_timing_metrics*/ false,
         /*beta_features_header*/ None,
-        /*item_ids_enabled*/ false,
         /*concurrent_reasoning_summaries_enabled*/ false,
         /*attestation_provider*/ None,
         HttpClientFactory::new(OutboundProxyPolicy::ReqwestDefault),
@@ -1844,8 +1843,10 @@ async fn record_initial_history_reconstructs_resumed_transcript() {
 #[tokio::test]
 async fn record_conversation_items_stamps_missing_turn_id_and_preserves_existing_turn_id() {
     let (session, turn_context) = make_session_and_context().await;
-    let fresh_item = user_message("fresh");
+    let mut fresh_item = user_message("fresh");
+    fresh_item.set_id(Some(ResponseItemId::with_suffix("msg", "fresh")));
     let mut existing_item = assistant_message("existing");
+    existing_item.set_id(Some(ResponseItemId::with_suffix("msg", "existing")));
     existing_item.set_turn_id_if_missing("older-turn");
 
     session
@@ -1918,8 +1919,8 @@ async fn record_inter_agent_communication_sets_turn_id_in_rollout_and_resume() {
         .await;
 
     assert_eq!(
-        session.clone_history().await.raw_items(),
-        std::slice::from_ref(&expected_item)
+        strip_response_item_ids(session.clone_history().await.raw_items()),
+        strip_response_item_ids(std::slice::from_ref(&expected_item))
     );
 
     session.flush_rollout().await.expect("rollout should flush");
@@ -1949,8 +1950,8 @@ async fn record_inter_agent_communication_sets_turn_id_in_rollout_and_resume() {
         RolloutItem::ResponseItem(expected_item.clone()),
     ];
     assert_eq!(
-        serde_json::to_value(persisted_items).unwrap(),
-        serde_json::to_value(expected_persisted_items).unwrap()
+        strip_response_item_ids_from_json(serde_json::to_value(persisted_items).unwrap()),
+        strip_response_item_ids_from_json(serde_json::to_value(expected_persisted_items).unwrap())
     );
 
     let (resumed_session, _resumed_turn_context) = make_session_and_context().await;
@@ -1958,8 +1959,8 @@ async fn record_inter_agent_communication_sets_turn_id_in_rollout_and_resume() {
         .record_initial_history(InitialHistory::Resumed(resumed))
         .await;
     assert_eq!(
-        resumed_session.clone_history().await.raw_items(),
-        std::slice::from_ref(&expected_item)
+        strip_response_item_ids(resumed_session.clone_history().await.raw_items()),
+        strip_response_item_ids(std::slice::from_ref(&expected_item))
     );
 }
 
@@ -1968,9 +1969,7 @@ async fn record_inter_agent_communication_preserves_item_id_in_rollout_and_resum
     let (mut session, turn_context, _rx) = make_session_and_context_with_auth_and_config_and_rx(
         CodexAuth::from_api_key("Test API Key"),
         Vec::new(),
-        |config| {
-            let _ = config.features.enable(Feature::ItemIds);
-        },
+        |_| {},
     )
     .await;
     let rollout_path =
@@ -2017,9 +2016,7 @@ async fn record_inter_agent_communication_preserves_item_id_in_rollout_and_resum
         make_session_and_context_with_auth_and_config_and_rx(
             CodexAuth::from_api_key("Test API Key"),
             Vec::new(),
-            |config| {
-                let _ = config.features.enable(Feature::ItemIds);
-            },
+            |_| {},
         )
         .await;
     resumed_session
@@ -2040,9 +2037,7 @@ async fn prepares_image_failures_before_history_insertion() {
     let (session, turn_context, _rx) = make_session_and_context_with_auth_and_config_and_rx(
         CodexAuth::from_api_key("Test API Key"),
         Vec::new(),
-        |config| {
-            let _ = config.features.enable(Feature::ItemIds);
-        },
+        |_| {},
     )
     .await;
     let item = ResponseItem::FunctionCallOutput {
@@ -2274,7 +2269,10 @@ async fn resumed_history_injects_initial_context_on_first_context_update_only()
     let initial_context = build_initial_context(&session, &turn_context).await;
     expected.extend(initial_context);
     let history_after_seed = session.clone_history().await;
-    assert_eq!(expected, history_after_seed.raw_items());
+    assert_eq!(
+        strip_response_item_ids(&expected),
+        strip_response_item_ids(history_after_seed.raw_items())
+    );
 
     session
         .record_context_updates_and_set_reference_context_item(&step_context)
@@ -2880,7 +2878,10 @@ async fn record_initial_history_reconstructs_forked_transcript() {
         .await;
 
     let history = session.state.lock().await.clone_history();
-    assert_eq!(expected, history.raw_items());
+    assert_eq!(
+        strip_response_item_ids(&expected),
+        strip_response_item_ids(history.raw_items())
+    );
 }
 
 #[tokio::test]
@@ -2888,9 +2889,7 @@ async fn start_new_context_window_assigns_and_persists_item_ids() {
     let (mut session, turn_context, _rx) = make_session_and_context_with_auth_and_config_and_rx(
         CodexAuth::from_api_key("Test API Key"),
         Vec::new(),
-        |config| {
-            let _ = config.features.enable(Feature::ItemIds);
-        },
+        |_| {},
     )
     .await;
     let rollout_path =
@@ -2941,9 +2940,7 @@ async fn record_initial_history_assigns_and_persists_id_for_forked_response_item
     let (mut session, _turn_context, _rx) = make_session_and_context_with_auth_and_config_and_rx(
         CodexAuth::from_api_key("Test API Key"),
         Vec::new(),
-        |config| {
-            let _ = config.features.enable(Feature::ItemIds);
-        },
+        |_| {},
     )
     .await;
     let rollout_path =
@@ -3329,6 +3326,7 @@ async fn thread_rollback_fails_without_persisted_thread_history() {
     let initial_context = build_initial_context(&sess, &tc).await;
     sess.record_conversation_items(tc.as_ref(), &initial_context)
         .await;
+    let history_before_rollback = sess.clone_history().await;
 
     handlers::thread_rollback(&sess, "sub-1".to_string(), /*num_turns*/ 1).await;
 
@@ -3341,7 +3339,10 @@ async fn thread_rollback_fails_without_persisted_thread_history() {
         error_event.codex_error_info,
         Some(CodexErrorInfo::ThreadRollbackFailed)
     );
-    assert_eq!(sess.clone_history().await.raw_items(), initial_context);
+    assert_eq!(
+        sess.clone_history().await.raw_items(),
+        history_before_rollback.raw_items()
+    );
 }
 
 #[tokio::test]
@@ -3755,6 +3756,7 @@ async fn thread_rollback_fails_when_turn_in_progress() {
     let initial_context = build_initial_context(&sess, &tc).await;
     sess.record_conversation_items(tc.as_ref(), &initial_context)
         .await;
+    let history_before_rollback = sess.clone_history().await;
 
     *sess.active_turn.lock().await = Some(crate::state::ActiveTurn::default());
     handlers::thread_rollback(&sess, "sub-1".to_string(), /*num_turns*/ 1).await;
@@ -3766,7 +3768,7 @@ async fn thread_rollback_fails_when_turn_in_progress() {
     );
 
     let history = sess.clone_history().await;
-    assert_eq!(initial_context, history.raw_items());
+    assert_eq!(history_before_rollback.raw_items(), history.raw_items());
 }
 
 #[tokio::test]
@@ -3776,6 +3778,7 @@ async fn thread_rollback_fails_when_num_turns_is_zero() {
     let initial_context = build_initial_context(&sess, &tc).await;
     sess.record_conversation_items(tc.as_ref(), &initial_context)
         .await;
+    let history_before_rollback = sess.clone_history().await;
 
     handlers::thread_rollback(&sess, "sub-1".to_string(), /*num_turns*/ 0).await;
 
@@ -3787,7 +3790,7 @@ async fn thread_rollback_fails_when_num_turns_is_zero() {
     );
 
     let history = sess.clone_history().await;
-    assert_eq!(initial_context, history.raw_items());
+    assert_eq!(history_before_rollback.raw_items(), history.raw_items());
 }
 
 #[tokio::test]
@@ -5465,7 +5468,6 @@ pub(crate) async fn make_session_and_context() -> (Session, TurnContext) {
             config.features.enabled(Feature::EnableRequestCompression),
             config.features.enabled(Feature::RuntimeMetrics),
             Session::build_model_client_beta_features_header(config.as_ref()),
-            /*item_ids_enabled*/ config.features.enabled(Feature::ItemIds),
             /*concurrent_reasoning_summaries_enabled*/
             config
                 .features
@@ -7625,7 +7627,6 @@ where
             config.features.enabled(Feature::EnableRequestCompression),
             config.features.enabled(Feature::RuntimeMetrics),
             Session::build_model_client_beta_features_header(config.as_ref()),
-            /*item_ids_enabled*/ config.features.enabled(Feature::ItemIds),
             /*concurrent_reasoning_summaries_enabled*/
             config
                 .features
@@ -8946,7 +8947,10 @@ async fn record_context_updates_and_set_reference_context_item_injects_full_cont
         .await;
     let history = session.clone_history().await;
     let initial_context = build_initial_context(&session, &turn_context).await;
-    assert_eq!(history.raw_items().to_vec(), initial_context);
+    assert_eq!(
+        strip_response_item_ids(history.raw_items()),
+        strip_response_item_ids(&initial_context)
+    );
 
     let current_context = session.reference_context_item().await;
     assert_eq!(
@@ -8996,7 +9000,10 @@ async fn record_context_updates_and_set_reference_context_item_reinjects_full_co
     let mut expected_history = vec![compacted_summary];
     let initial_context = build_initial_context(&session, &turn_context).await;
     expected_history.extend(initial_context);
-    assert_eq!(history.raw_items().to_vec(), expected_history);
+    assert_eq!(
+        strip_response_item_ids(history.raw_items()),
+        strip_response_item_ids(&expected_history)
+    );
 }
 
 #[tokio::test]
@@ -9748,7 +9755,8 @@ async fn task_finish_emits_turn_item_lifecycle_for_leftover_pending_user_input()
         internal_chat_message_metadata_passthrough: None,
     };
     assert!(
-        strip_metadata_from_items(history.raw_items()).contains(&expected),
+        strip_response_item_ids(&strip_metadata_from_items(history.raw_items()))
+            .contains(&expected),
         "expected pending input to be persisted into history on turn completion"
     );
 
diff --git a/codex-rs/core/src/session/turn.rs b/codex-rs/core/src/session/turn.rs
index 58706d52f5..ac3686aef5 100644
--- a/codex-rs/core/src/session/turn.rs
+++ b/codex-rs/core/src/session/turn.rs
@@ -1930,7 +1930,9 @@ fn assign_missing_streamed_response_item_id(
         return;
     }
 
-    let active_item_id = active_item.map(|item| ResponseItemId::from_server(item.id()));
+    let active_item_id = active_item
+        .map(|item| ResponseItemId::from_server(item.id()))
+        .filter(|item_id| !item_id.is_empty());
     item.set_id(active_item_id);
     Session::assign_missing_response_item_id(item);
 }
@@ -2051,9 +2053,7 @@ async fn try_run_sampling_request(
         match event {
             ResponseEvent::Created => {}
             ResponseEvent::OutputItemDone(mut item) => {
-                if turn_context.item_ids_enabled() {
-                    assign_missing_streamed_response_item_id(&mut item, active_item.as_ref());
-                }
+                assign_missing_streamed_response_item_id(&mut item, active_item.as_ref());
                 if let Some((_, mut consumer)) = active_tool_argument_diff_consumer.take()
                     && let Ok(Some(event)) = consumer.finish()
                 {
@@ -2148,9 +2148,7 @@ async fn try_run_sampling_request(
                 }
             }
             ResponseEvent::OutputItemAdded(mut item) => {
-                if turn_context.item_ids_enabled() {
-                    assign_missing_streamed_response_item_id(&mut item, /*active_item*/ None);
-                }
+                assign_missing_streamed_response_item_id(&mut item, /*active_item*/ None);
                 if let ResponseItem::CustomToolCall {
                     call_id,
                     name,
diff --git a/codex-rs/core/src/session/turn_context.rs b/codex-rs/core/src/session/turn_context.rs
index 07a6fdb005..fbb6f96493 100644
--- a/codex-rs/core/src/session/turn_context.rs
+++ b/codex-rs/core/src/session/turn_context.rs
@@ -162,11 +162,6 @@ enum TurnMultiAgentRuntime {
 }
 
 impl TurnContext {
-    pub(crate) fn item_ids_enabled(&self) -> bool {
-        self.config.features.enabled(Feature::ItemIds)
-            || matches!(self.history_mode, ThreadHistoryMode::Paginated)
-    }
-
     pub(crate) fn collaboration_mode(&self) -> CollaborationMode {
         CollaborationMode {
             mode: self.mode,
diff --git a/codex-rs/core/src/thread_manager_tests.rs b/codex-rs/core/src/thread_manager_tests.rs
index 2c3bfd80ea..2c41fd34e2 100644
--- a/codex-rs/core/src/thread_manager_tests.rs
+++ b/codex-rs/core/src/thread_manager_tests.rs
@@ -31,6 +31,7 @@ use codex_utils_path_uri::PathUri;
 use core_test_support::PathBufExt;
 use core_test_support::PathExt;
 use core_test_support::responses::mount_models_once;
+use core_test_support::responses::strip_response_item_ids_from_json;
 use pretty_assertions::assert_eq;
 use std::time::Duration;
 use tempfile::tempdir;
@@ -1782,8 +1783,9 @@ async fn interrupted_fork_snapshot_does_not_synthesize_turn_id_for_legacy_histor
         rollout_items
             .iter()
             .filter(|item| {
-                serde_json::to_value(item).expect("serialize rollout item")
-                    == interrupted_marker_json
+                strip_response_item_ids_from_json(
+                    serde_json::to_value(item).expect("serialize rollout item"),
+                ) == interrupted_marker_json
             })
             .count(),
         1,
@@ -1986,8 +1988,9 @@ async fn interrupted_fork_snapshot_uses_persisted_mid_turn_history_without_live_
         forked_rollout_items
             .iter()
             .filter(|item| {
-                serde_json::to_value(item).expect("serialize forked rollout item")
-                    == interrupted_marker_json
+                strip_response_item_ids_from_json(
+                    serde_json::to_value(item).expect("serialize forked rollout item"),
+                ) == interrupted_marker_json
             })
             .count(),
         1,
@@ -2021,8 +2024,9 @@ async fn interrupted_fork_snapshot_uses_persisted_mid_turn_history_without_live_
         reforked_rollout_items
             .iter()
             .filter(|item| {
-                serde_json::to_value(item).expect("serialize re-forked rollout item")
-                    == interrupted_marker_json
+                strip_response_item_ids_from_json(
+                    serde_json::to_value(item).expect("serialize re-forked rollout item"),
+                ) == interrupted_marker_json
             })
             .count(),
         1,
diff --git a/codex-rs/core/src/tools/handlers/extension_tools.rs b/codex-rs/core/src/tools/handlers/extension_tools.rs
index 7d31f08c21..2f799e912a 100644
--- a/codex-rs/core/src/tools/handlers/extension_tools.rs
+++ b/codex-rs/core/src/tools/handlers/extension_tools.rs
@@ -183,6 +183,8 @@ mod tests {
     use codex_tools::ExtensionTurnItem;
     use codex_utils_absolute_path::test_support::PathExt;
     use codex_utils_absolute_path::test_support::test_path_buf;
+    use core_test_support::responses::strip_response_item_id;
+    use core_test_support::responses::strip_response_item_ids;
     use pretty_assertions::assert_eq;
     use serde_json::json;
     use tokio::sync::Mutex;
@@ -357,7 +359,10 @@ mod tests {
         let EventMsg::RawResponseItem(raw_history_item) = raw_history_event.msg else {
             panic!("expected raw response item event");
         };
-        assert_eq!(raw_history_item.item, expected_history_item);
+        assert_eq!(
+            strip_response_item_id(raw_history_item.item),
+            expected_history_item
+        );
         let step_context = StepContext::for_test(Arc::clone(&turn));
         let invocation = ToolInvocation {
             session,
@@ -397,8 +402,8 @@ mod tests {
             expected_sandbox_cwds
         );
         assert_eq!(
-            captured_call.conversation_history.items(),
-            std::slice::from_ref(&expected_history_item)
+            strip_response_item_ids(captured_call.conversation_history.items()),
+            vec![expected_history_item]
         );
         match captured_call.payload {
             ToolPayload::Function { arguments } => {
diff --git a/codex-rs/core/src/tools/router_tests.rs b/codex-rs/core/src/tools/router_tests.rs
index 52a0208e72..1dc8328d09 100644
--- a/codex-rs/core/src/tools/router_tests.rs
+++ b/codex-rs/core/src/tools/router_tests.rs
@@ -26,6 +26,7 @@ use codex_tools::ResponsesApiNamespaceTool;
 use codex_tools::ToolName;
 use codex_tools::ToolSpec;
 use codex_tools::default_namespace_description;
+use core_test_support::responses::strip_response_item_ids_from_json;
 use pretty_assertions::assert_eq;
 use serde_json::json;
 use tokio_util::sync::CancellationToken;
@@ -439,13 +440,13 @@ async fn extension_tool_executors_are_model_visible_and_dispatchable() -> anyhow
             let value: serde_json::Value =
                 serde_json::from_str(&text).expect("extension tool output should be json");
             assert_eq!(
-                value,
-                json!({
+                strip_response_item_ids_from_json(value),
+                strip_response_item_ids_from_json(json!({
                     "arguments": { "message": "hello" },
                     "callId": "call-extension",
                     "conversationHistory": [expected_history_item],
                     "ok": true,
-                })
+                }))
             );
         }
         other => panic!("expected function call output, got {other:?}"),
diff --git a/codex-rs/core/tests/common/context_snapshot.rs b/codex-rs/core/tests/common/context_snapshot.rs
index 1a236e1aac..5afee0c4c7 100644
--- a/codex-rs/core/tests/common/context_snapshot.rs
+++ b/codex-rs/core/tests/common/context_snapshot.rs
@@ -5,6 +5,7 @@ use similar::TextDiff;
 use std::sync::OnceLock;
 
 use crate::responses::ResponsesRequest;
+use crate::responses::strip_response_item_ids_from_json;
 use codex_protocol::protocol::APPS_INSTRUCTIONS_OPEN_TAG;
 use codex_protocol::protocol::PLUGINS_INSTRUCTIONS_OPEN_TAG;
 use codex_protocol::protocol::SKILLS_INSTRUCTIONS_OPEN_TAG;
@@ -25,6 +26,7 @@ pub struct ContextSnapshotOptions {
     render_mode: ContextSnapshotRenderMode,
     strip_capability_instructions: bool,
     strip_agents_md_user_context: bool,
+    strip_response_item_ids: bool,
 }
 
 impl Default for ContextSnapshotOptions {
@@ -33,6 +35,7 @@ impl Default for ContextSnapshotOptions {
             render_mode: ContextSnapshotRenderMode::RedactedText,
             strip_capability_instructions: false,
             strip_agents_md_user_context: false,
+            strip_response_item_ids: false,
         }
     }
 }
@@ -52,6 +55,11 @@ impl ContextSnapshotOptions {
         self.strip_agents_md_user_context = true;
         self
     }
+
+    pub fn strip_response_item_ids(mut self) -> Self {
+        self.strip_response_item_ids = true;
+        self
+    }
 }
 
 pub fn format_request_input_snapshot(
@@ -267,6 +275,11 @@ fn format_request_body_snapshot(
     options: &ContextSnapshotOptions,
 ) -> String {
     let mut body = crate::responses::strip_metadata_from_json(request.body_json());
+    if options.strip_response_item_ids
+        && let Some(input) = body.get_mut("input")
+    {
+        *input = strip_response_item_ids_from_json(std::mem::take(input));
+    }
     canonicalize_json_snapshot_value(&mut body, options);
     serde_json::to_string_pretty(&body).expect("request body should serialize")
 }
diff --git a/codex-rs/core/tests/common/responses.rs b/codex-rs/core/tests/common/responses.rs
index 8fe2380d69..2b0c178b80 100644
--- a/codex-rs/core/tests/common/responses.rs
+++ b/codex-rs/core/tests/common/responses.rs
@@ -109,6 +109,43 @@ pub fn strip_metadata_from_items(items: &[ResponseItem]) -> Vec<ResponseItem> {
     items.iter().cloned().map(strip_metadata).collect()
 }
 
+/// Returns a response item without its Responses API item ID for semantic assertions.
+pub fn strip_response_item_id(mut item: ResponseItem) -> ResponseItem {
+    item.set_id(/*new_id*/ None);
+    item
+}
+
+/// Returns response items without their Responses API item IDs for semantic assertions.
+pub fn strip_response_item_ids(items: &[ResponseItem]) -> Vec<ResponseItem> {
+    items.iter().cloned().map(strip_response_item_id).collect()
+}
+
+/// Returns JSON without IDs on recognized Responses API items.
+pub fn strip_response_item_ids_from_json(value: Value) -> Value {
+    match value {
+        Value::Array(values) => Value::Array(
+            values
+                .into_iter()
+                .map(strip_response_item_ids_from_json)
+                .collect(),
+        ),
+        Value::Object(mut map) => {
+            let is_response_item =
+                serde_json::from_value::<ResponseItem>(Value::Object(map.clone()))
+                    .is_ok_and(|item| !matches!(item, ResponseItem::Other));
+            if is_response_item {
+                map.remove("id");
+            }
+            Value::Object(
+                map.into_iter()
+                    .map(|(key, value)| (key, strip_response_item_ids_from_json(value)))
+                    .collect(),
+            )
+        }
+        value => value,
+    }
+}
+
 /// Returns JSON without internal transport metadata for semantic assertions.
 pub fn strip_metadata_from_json(value: Value) -> Value {
     match value {
diff --git a/codex-rs/core/tests/responses_headers.rs b/codex-rs/core/tests/responses_headers.rs
index 604c0a1d3f..b94f7ed49d 100644
--- a/codex-rs/core/tests/responses_headers.rs
+++ b/codex-rs/core/tests/responses_headers.rs
@@ -130,7 +130,6 @@ async fn responses_stream_includes_subagent_header_on_review() {
         /*enable_request_compression*/ false,
         /*include_timing_metrics*/ false,
         /*beta_features_header*/ None,
-        /*item_ids_enabled*/ false,
         /*concurrent_reasoning_summaries_enabled*/ false,
         /*attestation_provider*/ None,
         config.http_client_factory(),
@@ -266,7 +265,6 @@ async fn responses_stream_includes_subagent_header_on_other() {
         /*enable_request_compression*/ false,
         /*include_timing_metrics*/ false,
         /*beta_features_header*/ None,
-        /*item_ids_enabled*/ false,
         /*concurrent_reasoning_summaries_enabled*/ false,
         /*attestation_provider*/ None,
         config.http_client_factory(),
@@ -387,7 +385,6 @@ async fn responses_respects_model_info_overrides_from_config() {
         /*enable_request_compression*/ false,
         /*include_timing_metrics*/ false,
         /*beta_features_header*/ None,
-        /*item_ids_enabled*/ false,
         /*concurrent_reasoning_summaries_enabled*/ false,
         /*attestation_provider*/ None,
         config.http_client_factory(),
diff --git a/codex-rs/core/tests/suite/agent_websocket.rs b/codex-rs/core/tests/suite/agent_websocket.rs
index 328ad56d11..00e2f84bbd 100644
--- a/codex-rs/core/tests/suite/agent_websocket.rs
+++ b/codex-rs/core/tests/suite/agent_websocket.rs
@@ -257,6 +257,7 @@ async fn websocket_v2_test_codex_shell_chain() -> Result<()> {
 
     let call_id = "shell-command-call";
     let mut shell_command_call = ev_shell_command_call(call_id, "echo websocket");
+    shell_command_call["item"]["id"] = serde_json::json!("fc_shell_command_call");
     shell_command_call["item"]["internal_chat_message_metadata_passthrough"] =
         serde_json::json!({"turn_id": "turn-123"});
     let server = start_websocket_server(vec![vec![
diff --git a/codex-rs/core/tests/suite/client.rs b/codex-rs/core/tests/suite/client.rs
index 226b676fcd..d5dc15d551 100644
--- a/codex-rs/core/tests/suite/client.rs
+++ b/codex-rs/core/tests/suite/client.rs
@@ -71,6 +71,7 @@ use core_test_support::responses::mount_sse_sequence;
 use core_test_support::responses::sse;
 use core_test_support::responses::sse_failed;
 use core_test_support::responses::strip_metadata_from_json;
+use core_test_support::responses::strip_response_item_ids_from_json;
 use core_test_support::responses_metadata as test_responses_metadata;
 use core_test_support::skip_if_no_network;
 use core_test_support::test_codex::TestCodex;
@@ -250,7 +251,7 @@ async fn openai_stateless_responses_requests_preserve_item_turn_metadata_across_
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn non_openai_responses_requests_omit_item_passthrough_metadata() {
+async fn non_openai_responses_requests_include_item_ids_without_passthrough_metadata() {
     let server = MockServer::start().await;
     let response_mock = mount_sse_once(
         &server,
@@ -299,8 +300,8 @@ async fn non_openai_responses_requests_omit_item_passthrough_metadata() {
             "input item should omit internal chat message metadata passthrough: {item}"
         );
         assert!(
-            item.get("id").is_none(),
-            "input item should omit generated IDs: {item}"
+            item.get("id").and_then(serde_json::Value::as_str).is_some(),
+            "input item should include a generated ID: {item}"
         );
     }
 }
@@ -433,9 +434,7 @@ async fn response_item_ids_persist_across_resume_and_preserve_server_ids() -> an
         ],
     )
     .await;
-    let mut builder = test_codex().with_config(|config| {
-        let _ = config.features.enable(Feature::ItemIds);
-    });
+    let mut builder = test_codex();
     let initial = builder.build(&server).await?;
     let home = Arc::clone(&initial.home);
     let rollout_path = initial
@@ -451,9 +450,6 @@ async fn response_item_ids_persist_across_resume_and_preserve_server_ids() -> an
     })
     .await;
 
-    builder = builder.with_config(|config| {
-        let _ = config.features.enable(Feature::ItemIds);
-    });
     let resumed = builder.resume(&server, home, rollout_path).await?;
     resumed.submit_turn("after resume").await?;
 
@@ -532,9 +528,7 @@ async fn synthetic_call_output_id_is_stable_across_resumes() -> anyhow::Result<(
     )
     .await;
     let codex_home = Arc::new(TempDir::new()?);
-    let mut builder = test_codex().with_config(|config| {
-        let _ = config.features.enable(Feature::ItemIds);
-    });
+    let mut builder = test_codex();
     let first = builder
         .resume(&server, Arc::clone(&codex_home), session_path.clone())
         .await?;
@@ -550,9 +544,6 @@ async fn synthetic_call_output_id_is_stable_across_resumes() -> anyhow::Result<(
         "prompt-only repair should not be persisted to the rollout"
     );
 
-    builder = builder.with_config(|config| {
-        let _ = config.features.enable(Feature::ItemIds);
-    });
     let second = builder.resume(&server, codex_home, session_path).await?;
     second.submit_turn("second resume").await?;
 
@@ -606,7 +597,6 @@ async fn response_item_ids_are_sent_for_all_remote_v2_compaction_requests() -> a
     let test = test_codex()
         .with_auth(CodexAuth::create_dummy_chatgpt_auth_for_testing())
         .with_config(|config| {
-            let _ = config.features.enable(Feature::ItemIds);
             let _ = config.features.enable(Feature::RemoteCompactionV2);
         })
         .build(&server)
@@ -1503,7 +1493,6 @@ async fn send_request_with_provider(provider: ModelProviderInfo) {
         /*enable_request_compression*/ false,
         /*include_timing_metrics*/ false,
         /*beta_features_header*/ None,
-        /*item_ids_enabled*/ config.features.enabled(Feature::ItemIds),
         /*concurrent_reasoning_summaries_enabled*/
         config
             .features
@@ -3236,7 +3225,6 @@ async fn azure_responses_request_includes_store_and_prefixed_item_ids() {
         /*enable_request_compression*/ false,
         /*include_timing_metrics*/ false,
         /*beta_features_header*/ None,
-        /*item_ids_enabled*/ false,
         /*concurrent_reasoning_summaries_enabled*/ false,
         /*attestation_provider*/ None,
         config.http_client_factory(),
@@ -4107,7 +4095,9 @@ async fn history_dedupes_streamed_and_final_messages_across_turns() {
     let tail_len = r3_tail_expected.as_array().unwrap().len();
     let actual_tail = &r3_input_array[r3_input_array.len() - tail_len..];
     assert_eq!(
-        strip_metadata_from_json(serde_json::Value::Array(actual_tail.to_vec())),
+        strip_response_item_ids_from_json(strip_metadata_from_json(serde_json::Value::Array(
+            actual_tail.to_vec(),
+        ))),
         r3_tail_expected,
         "request 3 tail mismatch",
     );
diff --git a/codex-rs/core/tests/suite/client_websockets.rs b/codex-rs/core/tests/suite/client_websockets.rs
index d76970a190..a218e721d7 100755
--- a/codex-rs/core/tests/suite/client_websockets.rs
+++ b/codex-rs/core/tests/suite/client_websockets.rs
@@ -161,8 +161,7 @@ async fn responses_websocket_streams_request() {
 
     let harness = websocket_harness(&server).await;
     let mut client_session = harness.client.new_session();
-    let mut prompt = prompt_with_input(vec![message_item("hello")]);
-    prompt.input[0].set_id(Some(ResponseItemId::with_suffix("msg", "existing")));
+    let prompt = prompt_with_input(vec![message_item("hello")]);
 
     stream_until_complete(&mut client_session, &harness, &prompt).await;
 
@@ -174,7 +173,6 @@ async fn responses_websocket_streams_request() {
     assert_eq!(body["model"].as_str(), Some(MODEL));
     assert_eq!(body["stream"], serde_json::Value::Bool(true));
     assert_eq!(body["input"].as_array().map(Vec::len), Some(1));
-    assert_eq!(body["input"][0].get("id"), None);
     let handshake = server.single_handshake();
     assert_eq!(
         handshake.header(OPENAI_BETA_HEADER),
@@ -225,7 +223,7 @@ async fn responses_websocket_omits_unprefixed_item_ids_without_mutating_prompt()
         websocket_provider(&server),
         /*runtime_metrics_enabled*/ false,
         /*concurrent_reasoning_summaries_enabled*/ false,
-        /*enabled_features*/ &[Feature::ItemIds],
+        /*enabled_features*/ &[],
     )
     .await;
     let mut client_session = harness.client.new_session();
@@ -2389,7 +2387,6 @@ async fn websocket_harness_with_provider_options(
         /*enable_request_compression*/ false,
         runtime_metrics_enabled,
         /*beta_features_header*/ None,
-        /*item_ids_enabled*/ config.features.enabled(Feature::ItemIds),
         /*concurrent_reasoning_summaries_enabled*/
         config
             .features
diff --git a/codex-rs/core/tests/suite/compact.rs b/codex-rs/core/tests/suite/compact.rs
index b4e3076b2a..2d39c44f15 100644
--- a/codex-rs/core/tests/suite/compact.rs
+++ b/codex-rs/core/tests/suite/compact.rs
@@ -34,6 +34,7 @@ use core_test_support::hooks::trust_discovered_hooks;
 use core_test_support::responses;
 use core_test_support::responses::ev_reasoning_item;
 use core_test_support::responses::mount_models_once;
+use core_test_support::responses::strip_response_item_ids_from_json;
 use core_test_support::skip_if_no_network;
 use core_test_support::test_codex::local_selections;
 use core_test_support::test_codex::test_codex;
@@ -1225,6 +1226,7 @@ async fn multiple_auto_compact_per_task_runs_after_token_limit_hit() {
         values
             .iter()
             .filter_map(|value| {
+                let value = strip_response_item_ids_from_json(value.clone());
                 if value
                     .get("type")
                     .and_then(|ty| ty.as_str())
@@ -1251,9 +1253,9 @@ async fn multiple_auto_compact_per_task_runs_after_token_limit_hit() {
                     return None;
                 }
                 if role == Some("user") {
-                    return strip_agents_parts_from_user_message(value);
+                    return strip_agents_parts_from_user_message(&value);
                 }
-                Some(value.clone())
+                Some(value)
             })
             .collect()
     }
@@ -4078,7 +4080,8 @@ async fn auto_compact_allows_multiple_attempts_when_interleaved_with_other_turn_
     let mut builder = test_codex().with_config(move |config| {
         config.model_provider = model_provider;
         set_test_compact_prompt(config);
-        config.model_auto_compact_token_limit = Some(200);
+        // Leave enough headroom for per-item request metadata before the second compaction.
+        config.model_auto_compact_token_limit = Some(300);
     });
     let codex = builder.build(&server).await.unwrap().codex;
 
diff --git a/codex-rs/core/tests/suite/compact_remote.rs b/codex-rs/core/tests/suite/compact_remote.rs
index 36e9d7696e..4cb0e92c8d 100644
--- a/codex-rs/core/tests/suite/compact_remote.rs
+++ b/codex-rs/core/tests/suite/compact_remote.rs
@@ -872,7 +872,7 @@ async fn assert_remote_manual_compact_request_parity(
             &normal_request,
             "Remote /responses/compact Request",
             &compact_request,
-            &ContextSnapshotOptions::default(),
+            &ContextSnapshotOptions::default().strip_response_item_ids(),
         )
     );
 
diff --git a/codex-rs/core/tests/suite/compact_remote_parity.rs b/codex-rs/core/tests/suite/compact_remote_parity.rs
index d4042a8c2e..fd06a0b433 100644
--- a/codex-rs/core/tests/suite/compact_remote_parity.rs
+++ b/codex-rs/core/tests/suite/compact_remote_parity.rs
@@ -14,6 +14,7 @@ use codex_protocol::user_input::UserInput;
 use core_test_support::hooks::trust_discovered_hooks;
 use core_test_support::responses;
 use core_test_support::responses::ResponseMock;
+use core_test_support::responses::strip_response_item_ids_from_json;
 use core_test_support::skip_if_no_network;
 use core_test_support::test_codex::TestCodexHarness;
 use core_test_support::test_codex::test_codex;
@@ -762,17 +763,17 @@ fn compact_request_view(body: &Value, mode: Mode) -> Value {
     }
 
     let mut selected = selected_request_fields(body, SelectedFieldsMode::Compact);
-    selected["input"] = normalize_value(Value::Array(input));
+    selected["input"] = normalize_value(strip_response_item_ids_from_json(Value::Array(input)));
     canonical_json(&normalize_value(selected))
 }
 
 fn follow_up_request_view(body: &Value) -> Value {
     let mut selected = selected_request_fields(body, SelectedFieldsMode::FollowUp);
-    selected["input"] = normalize_value(
+    selected["input"] = normalize_value(strip_response_item_ids_from_json(
         body.get("input")
             .cloned()
             .expect("follow-up request should include input"),
-    );
+    ));
     canonical_json(&normalize_value(selected))
 }
 
@@ -800,7 +801,9 @@ fn replacement_history_from_rollout(path: &Path) -> Result<Value> {
     }
     let replacement_history =
         replacement_history.expect("expected compacted rollout replacement history");
-    Ok(canonical_json(&normalize_value(replacement_history)))
+    Ok(canonical_json(&normalize_value(
+        strip_response_item_ids_from_json(replacement_history),
+    )))
 }
 
 fn write_manual_compact_hooks(home: &Path) {
diff --git a/codex-rs/core/tests/suite/image_rollout.rs b/codex-rs/core/tests/suite/image_rollout.rs
index d84a5501cc..e74a81ee25 100644
--- a/codex-rs/core/tests/suite/image_rollout.rs
+++ b/codex-rs/core/tests/suite/image_rollout.rs
@@ -16,6 +16,8 @@ use core_test_support::responses::ev_completed;
 use core_test_support::responses::ev_response_created;
 use core_test_support::responses::sse;
 use core_test_support::responses::start_mock_server;
+use core_test_support::responses::strip_metadata;
+use core_test_support::responses::strip_response_item_id;
 use core_test_support::skip_if_no_network;
 use core_test_support::test_codex::TestCodex;
 use core_test_support::test_codex::local_selections;
@@ -181,7 +183,7 @@ async fn copy_paste_local_image_persists_rollout_request_shape() -> anyhow::Resu
         internal_chat_message_metadata_passthrough: None,
     };
 
-    assert_eq!(responses::strip_metadata(actual), expected);
+    assert_eq!(strip_response_item_id(strip_metadata(actual)), expected);
 
     Ok(())
 }
@@ -272,7 +274,7 @@ async fn drag_drop_image_persists_rollout_request_shape() -> anyhow::Result<()>
         internal_chat_message_metadata_passthrough: None,
     };
 
-    assert_eq!(responses::strip_metadata(actual), expected);
+    assert_eq!(strip_response_item_id(strip_metadata(actual)), expected);
 
     Ok(())
 }
diff --git a/codex-rs/core/tests/suite/items.rs b/codex-rs/core/tests/suite/items.rs
index 370c1a289c..c41c2bbf84 100644
--- a/codex-rs/core/tests/suite/items.rs
+++ b/codex-rs/core/tests/suite/items.rs
@@ -253,12 +253,7 @@ async fn missing_streamed_reasoning_id_is_reused_for_completion() -> anyhow::Res
     skip_if_no_network!(Ok(()));
 
     let server = start_mock_server().await;
-    let TestCodex { codex, .. } = test_codex()
-        .with_config(|config| {
-            let _ = config.features.enable(Feature::ItemIds);
-        })
-        .build_with_auto_env(&server)
-        .await?;
+    let TestCodex { codex, .. } = test_codex().build_with_auto_env(&server).await?;
 
     let mut reasoning_added = ev_reasoning_item_added("unused", &[]);
     reasoning_added["item"]
diff --git a/codex-rs/core/tests/suite/model_switching.rs b/codex-rs/core/tests/suite/model_switching.rs
index b33555814e..470709c746 100644
--- a/codex-rs/core/tests/suite/model_switching.rs
+++ b/codex-rs/core/tests/suite/model_switching.rs
@@ -681,11 +681,6 @@ async fn generated_image_is_replayed_for_image_capable_models() -> Result<()> {
         1,
         "expected generated image history to be replayed as an image_generation_call"
     );
-    assert_eq!(
-        image_generation_calls[0]["id"].as_str(),
-        None,
-        "expected the image generation call id to be omitted"
-    );
     assert_eq!(
         image_generation_calls[0]["result"].as_str(),
         Some("Zm9v"),
@@ -786,11 +781,6 @@ async fn model_change_from_generated_image_to_text_preserves_prior_generated_ima
         image_generation_calls.len() == 1,
         "second request should preserve the generated image call for text-only models"
     );
-    assert_eq!(
-        image_generation_calls[0]["id"].as_str(),
-        None,
-        "second request should omit the generated image call id"
-    );
     assert_eq!(
         image_generation_calls[0]["result"].as_str(),
         Some(""),
diff --git a/codex-rs/core/tests/suite/prompt_caching.rs b/codex-rs/core/tests/suite/prompt_caching.rs
index ee5531f4b5..9f74266f01 100644
--- a/codex-rs/core/tests/suite/prompt_caching.rs
+++ b/codex-rs/core/tests/suite/prompt_caching.rs
@@ -26,6 +26,7 @@ use core_test_support::responses::mount_sse_once;
 use core_test_support::responses::sse;
 use core_test_support::responses::start_mock_server;
 use core_test_support::responses::strip_metadata_from_json;
+use core_test_support::responses::strip_response_item_ids_from_json;
 use core_test_support::skip_if_no_network;
 use core_test_support::test_codex::TestCodex;
 use core_test_support::test_codex::local_selections;
@@ -55,10 +56,10 @@ fn text_user_input_parts(texts: Vec<String>) -> serde_json::Value {
     })
 }
 
-fn assert_eq_without_metadata(left: serde_json::Value, right: serde_json::Value) {
+fn assert_eq_without_metadata_or_item_ids(left: serde_json::Value, right: serde_json::Value) {
     assert_eq!(
-        strip_metadata_from_json(left),
-        strip_metadata_from_json(right)
+        strip_response_item_ids_from_json(strip_metadata_from_json(left)),
+        strip_response_item_ids_from_json(strip_metadata_from_json(right))
     );
 }
 
@@ -392,15 +393,18 @@ async fn prefixes_context_and_instructions_once_and_consistently_across_requests
         Some("input_text"),
         "expected environment context bundled after UI message in cached contextual message"
     );
-    assert_eq_without_metadata(input1[2].clone(), text_user_input("hello 1".to_string()));
+    assert_eq_without_metadata_or_item_ids(
+        input1[2].clone(),
+        text_user_input("hello 1".to_string()),
+    );
 
     let body2 = req2.single_request().body_json();
     let input2 = body2["input"].as_array().expect("input array");
-    assert_eq_without_metadata(
+    assert_eq_without_metadata_or_item_ids(
         serde_json::Value::Array(input2[..input1.len()].to_vec()),
         serde_json::Value::Array(input1.to_vec()),
     );
-    assert_eq_without_metadata(
+    assert_eq_without_metadata_or_item_ids(
         input2[input1.len()].clone(),
         text_user_input("hello 2".to_string()),
     );
@@ -533,7 +537,7 @@ async fn overrides_turn_context_but_keeps_cached_prefix_and_key_constant() -> an
     expected_body2.push(expected_permissions_msg_2);
     expected_body2.push(expected_env_msg_2);
     expected_body2.push(expected_user_message_2);
-    assert_eq_without_metadata(
+    assert_eq_without_metadata_or_item_ids(
         body2["input"].clone(),
         serde_json::Value::Array(expected_body2),
     );
@@ -823,7 +827,7 @@ async fn per_turn_overrides_keep_cached_prefix_and_key_constant() -> anyhow::Res
     expected_body2.push(expected_permissions_update_msg);
     expected_body2.push(expected_env_msg_2);
     expected_body2.push(expected_user_message_2);
-    assert_eq_without_metadata(
+    assert_eq_without_metadata_or_item_ids(
         body2["input"].clone(),
         serde_json::Value::Array(expected_body2),
     );
@@ -955,7 +959,7 @@ async fn send_user_turn_with_no_changes_does_not_send_environment_context() -> a
         expected_contextual_user_msg_1.clone(),
         expected_user_message_1.clone(),
     ]);
-    assert_eq_without_metadata(body1["input"].clone(), expected_input_1);
+    assert_eq_without_metadata_or_item_ids(body1["input"].clone(), expected_input_1);
 
     let expected_user_message_2 = text_user_input("hello 2".to_string());
     let expected_input_2 = serde_json::Value::Array(vec![
@@ -964,7 +968,7 @@ async fn send_user_turn_with_no_changes_does_not_send_environment_context() -> a
         expected_user_message_1,
         expected_user_message_2,
     ]);
-    assert_eq_without_metadata(body2["input"].clone(), expected_input_2);
+    assert_eq_without_metadata_or_item_ids(body2["input"].clone(), expected_input_2);
 
     Ok(())
 }
@@ -1094,7 +1098,7 @@ async fn send_user_turn_with_changes_sends_environment_context() -> anyhow::Resu
         expected_contextual_user_msg_1.clone(),
         expected_user_message_1.clone(),
     ]);
-    assert_eq_without_metadata(body1["input"].clone(), expected_input_1);
+    assert_eq_without_metadata_or_item_ids(body1["input"].clone(), expected_input_1);
 
     let body1_input = body1["input"].as_array().expect("input array");
     let expected_settings_update_msg = body2["input"][body1_input.len()].clone();
@@ -1139,7 +1143,7 @@ async fn send_user_turn_with_changes_sends_environment_context() -> anyhow::Resu
         expected_env_update_msg,
         expected_user_message_2,
     ]);
-    assert_eq_without_metadata(body2["input"].clone(), expected_input_2);
+    assert_eq_without_metadata_or_item_ids(body2["input"].clone(), expected_input_2);
 
     Ok(())
 }
diff --git a/codex-rs/core/tests/suite/prompt_debug_tests.rs b/codex-rs/core/tests/suite/prompt_debug_tests.rs
index 74aeece04d..3d75f8f185 100644
--- a/codex-rs/core/tests/suite/prompt_debug_tests.rs
+++ b/codex-rs/core/tests/suite/prompt_debug_tests.rs
@@ -9,6 +9,7 @@ use codex_protocol::models::ContentItem;
 use codex_protocol::models::ResponseItem;
 use codex_protocol::user_input::UserInput;
 use core_test_support::responses::strip_metadata;
+use core_test_support::responses::strip_response_item_id;
 use pretty_assertions::assert_eq;
 use tempfile::TempDir;
 
@@ -53,7 +54,11 @@ async fn build_prompt_input_includes_context_and_user_message() -> Result<()> {
         internal_chat_message_metadata_passthrough: None,
     };
     assert_eq!(
-        input.last().cloned().map(strip_metadata),
+        input
+            .last()
+            .cloned()
+            .map(strip_metadata)
+            .map(strip_response_item_id),
         Some(expected_user_message)
     );
     assert!(input.iter().any(|item| {
diff --git a/codex-rs/core/tests/suite/subagent_notifications.rs b/codex-rs/core/tests/suite/subagent_notifications.rs
index cf42a7c2f5..3b2638788f 100644
--- a/codex-rs/core/tests/suite/subagent_notifications.rs
+++ b/codex-rs/core/tests/suite/subagent_notifications.rs
@@ -31,6 +31,7 @@ use core_test_support::responses::sse;
 use core_test_support::responses::sse_response;
 use core_test_support::responses::start_mock_server;
 use core_test_support::responses::strip_metadata_from_json;
+use core_test_support::responses::strip_response_item_ids_from_json;
 use core_test_support::skip_if_no_network;
 use core_test_support::test_codex::TestCodex;
 use core_test_support::test_codex::local_selections;
@@ -1435,7 +1436,9 @@ async fn encrypted_multi_agent_v2_spawn_sends_agent_message_to_child() -> Result
         sleep(Duration::from_millis(10)).await;
     };
     assert_eq!(
-        strip_metadata_from_json(Value::Array(child_request.inputs_of_type("agent_message"))),
+        strip_response_item_ids_from_json(strip_metadata_from_json(Value::Array(
+            child_request.inputs_of_type("agent_message"),
+        ))),
         Value::Array(vec![json!({
             "type": "agent_message",
             "author": "/root",
@@ -1623,7 +1626,9 @@ async fn plaintext_multi_agent_v2_completion_sends_agent_message(
         .pop()
         .expect("agent message request");
     assert_eq!(
-        strip_metadata_from_json(Value::Array(request.inputs_of_type("agent_message"))),
+        strip_response_item_ids_from_json(strip_metadata_from_json(Value::Array(
+            request.inputs_of_type("agent_message"),
+        ))),
         Value::Array(vec![json!({
             "type": "agent_message",
             "author": "/root/worker",
diff --git a/codex-rs/core/tests/suite/tools.rs b/codex-rs/core/tests/suite/tools.rs
index 71d7e6f9b8..9b9e4e99ba 100644
--- a/codex-rs/core/tests/suite/tools.rs
+++ b/codex-rs/core/tests/suite/tools.rs
@@ -27,6 +27,7 @@ use core_test_support::responses::mount_sse_once;
 use core_test_support::responses::mount_sse_sequence;
 use core_test_support::responses::sse;
 use core_test_support::responses::start_mock_server;
+use core_test_support::responses::strip_response_item_ids_from_json;
 use core_test_support::skip_if_no_network;
 use core_test_support::skip_if_sandbox;
 use core_test_support::test_codex::local;
@@ -226,9 +227,12 @@ async fn namespaced_custom_tool_call_preserves_namespace_through_dispatch_and_re
         .map(str::to_string)
         .expect("custom tool call should include turn metadata");
     assert_eq!(
-        (custom_tool_calls, request.custom_tool_call_output(call_id),),
         (
-            vec![json!({
+            strip_response_item_ids_from_json(Value::Array(custom_tool_calls)),
+            strip_response_item_ids_from_json(request.custom_tool_call_output(call_id)),
+        ),
+        (
+            Value::Array(vec![json!({
                 "type": "custom_tool_call",
                 "call_id": call_id,
                 "namespace": namespace,
@@ -237,7 +241,7 @@ async fn namespaced_custom_tool_call_preserves_namespace_through_dispatch_and_re
                 "internal_chat_message_metadata_passthrough": {
                     "turn_id": turn_id,
                 },
-            })],
+            })]),
             json!({
                 "type": "custom_tool_call_output",
                 "call_id": call_id,
diff --git a/codex-rs/features/src/lib.rs b/codex-rs/features/src/lib.rs
index e7a80495a3..f027f5c997 100644
--- a/codex-rs/features/src/lib.rs
+++ b/codex-rs/features/src/lib.rs
@@ -206,7 +206,7 @@ pub enum Feature {
     ImageGeneration,
     /// Removed compatibility flag for always-on centralized image preparation.
     ResizeAllImages,
-    /// Generate Responses API item IDs for client-created history items.
+    /// Removed compatibility flag for always-on response item IDs.
     ItemIds,
     /// Request sequential cutoff reasoning summary delivery.
     ConcurrentReasoningSummaries,
@@ -483,7 +483,7 @@ impl Features {
                 "tool_search" | "tool_search_always_defer_mcp_tools" | "apps_mcp_path_override" => {
                     continue;
                 }
-                "image_detail_original" | "resize_all_images" => {
+                "image_detail_original" | "resize_all_images" | "item_ids" => {
                     continue;
                 }
                 "plugin_hooks" => {
@@ -1198,8 +1198,8 @@ pub const FEATURES: &[FeatureSpec] = &[
     FeatureSpec {
         id: Feature::ItemIds,
         key: "item_ids",
-        stage: Stage::UnderDevelopment,
-        default_enabled: false,
+        stage: Stage::Removed,
+        default_enabled: true,
     },
     FeatureSpec {
         id: Feature::ConcurrentReasoningSummaries,
diff --git a/codex-rs/features/src/tests.rs b/codex-rs/features/src/tests.rs
index 898e5db268..46588295fe 100644
--- a/codex-rs/features/src/tests.rs
+++ b/codex-rs/features/src/tests.rs
@@ -274,6 +274,23 @@ fn from_sources_ignores_removed_resize_all_images_feature_key() {
     assert_eq!(features, Features::with_defaults());
 }
 
+#[test]
+fn from_sources_ignores_removed_item_ids_feature_key() {
+    let features_toml = FeaturesToml::from(BTreeMap::from([("item_ids".to_string(), false)]));
+
+    let features = Features::from_sources(
+        FeatureConfigSource {
+            features: Some(&features_toml),
+            ..Default::default()
+        },
+        FeatureConfigSource::default(),
+        FeatureOverrides::default(),
+    );
+
+    assert_eq!(features, Features::with_defaults());
+    assert_eq!(features.enabled(Feature::ItemIds), true);
+}
+
 #[test]
 fn from_sources_ignores_removed_undo_feature_key() {
     let features_toml = FeaturesToml::from(BTreeMap::from([("undo".to_string(), true)]));
diff --git a/codex-rs/memories/write/src/runtime.rs b/codex-rs/memories/write/src/runtime.rs
index 9219edaeb5..4e6f4c8cd9 100644
--- a/codex-rs/memories/write/src/runtime.rs
+++ b/codex-rs/memories/write/src/runtime.rs
@@ -260,7 +260,6 @@ impl MemoryStartupContext {
             config.features.enabled(Feature::EnableRequestCompression),
             config.features.enabled(Feature::RuntimeMetrics),
             /*beta_features_header*/ None,
-            config.features.enabled(Feature::ItemIds),
             /*concurrent_reasoning_summaries_enabled*/ false,
             /*attestation_provider*/ None,
             config.http_client_factory(),