diff --git a/codex-rs/Cargo.lock b/codex-rs/Cargo.lock
index 80ab9016a6..70cb064d0f 100644
--- a/codex-rs/Cargo.lock
+++ b/codex-rs/Cargo.lock
@@ -3850,6 +3850,7 @@ dependencies = [
  "codex-protocol",
  "codex-protocol-test-support",
  "codex-utils-absolute-path",
+ "codex-utils-model-facing-id",
  "pretty_assertions",
  "schemars 0.8.22",
  "serde",
diff --git a/codex-rs/app-server-protocol/schema/precomputed/app-server-exports-stable.json.zst b/codex-rs/app-server-protocol/schema/precomputed/app-server-exports-stable.json.zst
index 29094221fa..6bffcd663e 100644
Binary files a/codex-rs/app-server-protocol/schema/precomputed/app-server-exports-stable.json.zst and b/codex-rs/app-server-protocol/schema/precomputed/app-server-exports-stable.json.zst differ
diff --git a/codex-rs/core/src/agent/control_tests.rs b/codex-rs/core/src/agent/control_tests.rs
index 9c65c797b8..0c26ab4482 100644
--- a/codex-rs/core/src/agent/control_tests.rs
+++ b/codex-rs/core/src/agent/control_tests.rs
@@ -2716,6 +2716,7 @@ async fn spawn_agent_fork_sanitizes_inherited_compaction_metadata() {
 
     let (parent_thread_id, parent_thread) = harness.start_paginated_thread().await;
     let parent_resume_metadata = codex_history::CompactionResumeMetadata {
+        next_item_ordinal: None,
         rejected_audio_file_ids: Default::default(),
         dynamic_tools: None,
         multi_agent_version: Some(MultiAgentVersion::V2),
@@ -3881,6 +3882,7 @@ async fn spawn_agent_full_fork_legacy_compaction_rebuilds_child_instructions_onc
                 compaction_response_id: None,
                 latest_token_usage_record: None,
                 resume_metadata: Some(codex_history::CompactionResumeMetadata {
+                    next_item_ordinal: None,
                     rejected_audio_file_ids: Default::default(),
                     dynamic_tools: None,
                     multi_agent_version: Some(MultiAgentVersion::V2),
@@ -4017,6 +4019,7 @@ async fn spawn_agent_full_fork_legacy_compaction_rebuilds_child_instructions_onc
         assert_eq!(
             inherited_state,
             Some(codex_history::CompactionResumeMetadata {
+                next_item_ordinal: None,
                 rejected_audio_file_ids: Default::default(),
                 dynamic_tools: None,
                 multi_agent_version: Some(MultiAgentVersion::V2),
diff --git a/codex-rs/core/src/context_manager/history.rs b/codex-rs/core/src/context_manager/history.rs
index e6e8a0e27a..4c07b7fb3f 100644
--- a/codex-rs/core/src/context_manager/history.rs
+++ b/codex-rs/core/src/context_manager/history.rs
@@ -389,7 +389,16 @@ impl ContextManager {
     }
 
     pub(crate) fn record_retained_context(&mut self, event: &RetainedContextEvent) -> bool {
-        if !Arc::make_mut(&mut self.retained_context).record(event, &self.item_id_generator) {
+        self.record_retained_context_for_persistence(&mut event.clone())
+    }
+
+    pub(crate) fn record_retained_context_for_persistence(
+        &mut self,
+        event: &mut RetainedContextEvent,
+    ) -> bool {
+        if !Arc::make_mut(&mut self.retained_context)
+            .record_and_capture(event, &self.item_id_generator)
+        {
             return false;
         }
         match event {
diff --git a/codex-rs/core/src/context_manager/history_tests.rs b/codex-rs/core/src/context_manager/history_tests.rs
index 5aff78bb7f..62bd597a8e 100644
--- a/codex-rs/core/src/context_manager/history_tests.rs
+++ b/codex-rs/core/src/context_manager/history_tests.rs
@@ -203,6 +203,7 @@ fn delivered_assistant_context_invalidates_reviews_without_changing_authorizatio
     let before_delivery = history.conversation_history_snapshot();
     let authorization = before_delivery.user_message_revision();
     let event = RetainedContextEvent::DeliveredAssistantMessage {
+        retained_source: None,
         message: codex_history::RetainedUserMessage {
             origin: codex_history::UserInputOrigin::User,
             turn_id: "turn".to_owned(),
diff --git a/codex-rs/core/src/session/mod.rs b/codex-rs/core/src/session/mod.rs
index ce93060cd4..ea95f784bd 100644
--- a/codex-rs/core/src/session/mod.rs
+++ b/codex-rs/core/src/session/mod.rs
@@ -4959,6 +4959,7 @@ impl Session {
                 compaction_response_id: metadata.compaction_response_id,
                 latest_token_usage_record: state.latest_token_usage_record.clone(),
                 resume_metadata: Some(CompactionResumeMetadata {
+                    next_item_ordinal: None,
                     rejected_audio_file_ids: state.history.rejected_audio_file_ids(),
                     dynamic_tools: Some(Box::new(DynamicToolsSnapshot {
                         thread_id: self.thread_id(),
diff --git a/codex-rs/core/src/session/retained_context.rs b/codex-rs/core/src/session/retained_context.rs
index 6572cbb811..eb344f50e6 100644
--- a/codex-rs/core/src/session/retained_context.rs
+++ b/codex-rs/core/src/session/retained_context.rs
@@ -156,7 +156,6 @@ impl Session {
     }
 
     pub(crate) async fn record_retained_context(&self, mut event: RetainedContextEvent) {
-        event.bound();
         // Share the checkpoint persistence lock so a fact cannot land on the wrong side
         // of the checkpoint/suffix boundary. Ephemeral threads use the same live state.
         let _guard = thread_settings::acquire_persistence_lock(self).await;
@@ -165,7 +164,7 @@ impl Session {
             .lock()
             .await
             .history
-            .record_retained_context(&event)
+            .record_retained_context_for_persistence(&mut event)
         {
             self.persist_rollout_items(&[RolloutItem::RetainedContext(event)])
                 .await;
@@ -211,10 +210,12 @@ impl Session {
             let mut state = session.state.lock().await;
             let mut event = RetainedContextEvent::DeliveredAssistantMessage {
                 message,
+                retained_source: None,
                 acceptance_order: state.history.reserve_input_order(),
             };
-            event.bound();
-            state.history.record_retained_context(&event);
+            state
+                .history
+                .record_retained_context_for_persistence(&mut event);
             let mut pending = session
                 .code_mode_message_tasks
                 .pending_persistence
diff --git a/codex-rs/core/src/session/rollout_reconstruction_tests.rs b/codex-rs/core/src/session/rollout_reconstruction_tests.rs
index 37683e4a08..96181f9f9a 100644
--- a/codex-rs/core/src/session/rollout_reconstruction_tests.rs
+++ b/codex-rs/core/src/session/rollout_reconstruction_tests.rs
@@ -1642,6 +1642,7 @@ async fn bounded_replay_matches_full_replay_after_empty_turn_compactions(
                     compaction_response_id: None,
                     latest_token_usage_record: None,
                     resume_metadata: current.then(|| codex_history::CompactionResumeMetadata {
+                        next_item_ordinal: None,
                         rejected_audio_file_ids: Default::default(),
                         dynamic_tools: None,
                         multi_agent_version: None,
diff --git a/codex-rs/core/src/session/tests.rs b/codex-rs/core/src/session/tests.rs
index 39dcd3cd54..08131fc76d 100644
--- a/codex-rs/core/src/session/tests.rs
+++ b/codex-rs/core/src/session/tests.rs
@@ -2631,6 +2631,25 @@ async fn inter_agent_communication_waits_for_confirmed_delivery_persistence() {
         ]
     );
     let live = session.clone_history().await;
+    let replayed = session
+        .reconstruct_history_from_rollout(&replay_turn, &resumed.history)
+        .await;
+    let delivery_sources = |context: &codex_history::RetainedContext| {
+        context
+            .ordered_entries()
+            .filter_map(|(_, entry)| match entry {
+                codex_history::RetainedContextEntry::AssistantMessage(_) => Some(
+                    context
+                        .source(entry)
+                        .expect("confirmed delivery has a revision"),
+                ),
+                _ => None,
+            })
+            .collect::<Vec<_>>()
+    };
+    let expected = delivery_sources(live.retained_context());
+    assert_eq!(expected.len(), 2);
+    assert_eq!(delivery_sources(&replayed.retained_context), expected);
     let communication = live
         .annotated_items()
         .iter()
@@ -6219,6 +6238,7 @@ async fn compaction_persists_resume_metadata_and_companion_records() {
 
     session.multi_agent_version = std::sync::OnceLock::from(MultiAgentVersion::V2);
     let expected = CompactionResumeMetadata {
+        next_item_ordinal: None,
         rejected_audio_file_ids: Default::default(),
         dynamic_tools: Some(Box::new(DynamicToolsSnapshot {
             thread_id: session.thread_id(),
diff --git a/codex-rs/ext/guardian-v3/tests/evidence.rs b/codex-rs/ext/guardian-v3/tests/evidence.rs
index 0ca967a661..e39d331299 100644
--- a/codex-rs/ext/guardian-v3/tests/evidence.rs
+++ b/codex-rs/ext/guardian-v3/tests/evidence.rs
@@ -130,6 +130,7 @@ Approved action: {"action":{"command":"write /workspace/report.txt"},"outcome":"
         acceptance_order: Some(2),
     });
     let delivered = RolloutItem::RetainedContext(RetainedContextEvent::DeliveredAssistantMessage {
+        retained_source: None,
         message: RetainedUserMessage {
             turn_id: "turn-1".into(),
             message_id: Some("delivered-1".into()),
diff --git a/codex-rs/history/Cargo.toml b/codex-rs/history/Cargo.toml
index b43dc52698..f090e69cc3 100644
--- a/codex-rs/history/Cargo.toml
+++ b/codex-rs/history/Cargo.toml
@@ -15,6 +15,7 @@ workspace = true
 [dependencies]
 codex-protocol = { workspace = true }
 codex-utils-absolute-path = { workspace = true }
+codex-utils-model-facing-id = { workspace = true }
 schemars = { workspace = true }
 serde = { workspace = true, features = ["derive"] }
 serde_json = { workspace = true }
diff --git a/codex-rs/history/src/compaction_resume_metadata.rs b/codex-rs/history/src/compaction_resume_metadata.rs
index 6368889632..94768545af 100644
--- a/codex-rs/history/src/compaction_resume_metadata.rs
+++ b/codex-rs/history/src/compaction_resume_metadata.rs
@@ -18,6 +18,9 @@ use std::sync::Arc;
 /// compactions that did not.
 #[derive(Clone, Debug, PartialEq, Serialize, Deserialize, JsonSchema)]
 pub struct CompactionResumeMetadata {
+    /// Next ordinal in the producing thread's seeded item ID sequence at this checkpoint.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub next_item_ordinal: Option<u64>,
     /// Immutable file references rejected before this checkpoint.
     #[serde(default, skip_serializing_if = "BTreeSet::is_empty")]
     pub rejected_audio_file_ids: Arc<BTreeSet<String>>,
diff --git a/codex-rs/history/src/lib.rs b/codex-rs/history/src/lib.rs
index 28ad371cde..54792bf89b 100644
--- a/codex-rs/history/src/lib.rs
+++ b/codex-rs/history/src/lib.rs
@@ -290,6 +290,8 @@ impl JsonSchema for RolloutItem {
 }
 
 mod guardian_history;
+mod model_id_ordinals;
+pub use model_id_ordinals::next_model_id_ordinals;
 mod reconciled_retained_context;
 mod retained_context;
 mod sender_user_messages;
diff --git a/codex-rs/history/src/model_id_ordinals.rs b/codex-rs/history/src/model_id_ordinals.rs
new file mode 100644
index 0000000000..41e397e9d1
--- /dev/null
+++ b/codex-rs/history/src/model_id_ordinals.rs
@@ -0,0 +1,70 @@
+//! Recovers seeded allocation positions from a compaction checkpoint and subsequent thread items.
+
+use codex_protocol::ResponseItemId;
+use codex_utils_model_facing_id::ModelFacingId;
+
+use crate::RetainedContextEvent;
+use crate::RolloutItem;
+
+/// Next item and window ordinals. Legacy strings have no allocation provenance.
+pub fn next_model_id_ordinals(records: &[RolloutItem]) -> (u64, u64) {
+    let mut item = None;
+    let mut window = None;
+    for record in records {
+        match record {
+            RolloutItem::SessionMeta(meta) => {
+                if let Some(initial) = &meta.meta.context_window {
+                    window = window.max(initial.window_id.allocation().map(ModelFacingId::ordinal));
+                }
+            }
+            RolloutItem::Compacted(checkpoint) => {
+                if let Some(next) = checkpoint
+                    .resume_metadata
+                    .as_ref()
+                    .and_then(|m| m.next_item_ordinal)
+                {
+                    item = next.checked_sub(1);
+                }
+                if let Some(id) = &checkpoint.window_id {
+                    window = window.max(id.allocation().map(ModelFacingId::ordinal));
+                }
+            }
+            RolloutItem::ResponseItem(envelope) => {
+                item = item.max(envelope.item.id().and_then(item_ordinal));
+                // The retained revision is local. Guardian delivery metadata quotes other threads.
+                if let Some(source) = envelope
+                    .metadata
+                    .as_ref()
+                    .and_then(|m| m.retained_source.as_ref())
+                {
+                    item = item.max(item_ordinal(&source.revision));
+                }
+            }
+            RolloutItem::InterAgentCommunication(message) => {
+                item = item.max(message.id.as_ref().and_then(item_ordinal));
+            }
+            RolloutItem::RetainedContext(RetainedContextEvent::DeliveredAssistantMessage {
+                retained_source: Some(source),
+                ..
+            }) => {
+                item = item.max(item_ordinal(&source.revision));
+            }
+            RolloutItem::DynamicToolsUpdated { .. }
+            | RolloutItem::InterAgentCommunicationMetadata { .. }
+            | RolloutItem::TurnContext(_)
+            | RolloutItem::TokenUsageRecord(_)
+            | RolloutItem::WorldState(_)
+            | RolloutItem::SecurityRiskScore(_)
+            | RolloutItem::RetainedContext(_)
+            | RolloutItem::EventMsg(_)
+            | RolloutItem::RealtimeItem(_) => {}
+        }
+    }
+    let next = |last: Option<u64>| last.map_or(0, |ordinal| ordinal.wrapping_add(1));
+    (next(item), next(window))
+}
+
+fn item_ordinal(id: &ResponseItemId) -> Option<u64> {
+    id.allocation()
+        .map(|allocation| allocation.model_id.ordinal())
+}
diff --git a/codex-rs/history/src/retained_assistant_messages.rs b/codex-rs/history/src/retained_assistant_messages.rs
index b942f1decf..b4e75363ab 100644
--- a/codex-rs/history/src/retained_assistant_messages.rs
+++ b/codex-rs/history/src/retained_assistant_messages.rs
@@ -37,9 +37,20 @@ impl RetainedContext {
     /// Returns the captured source for the original envelope, independently of buffer eviction.
     pub fn record_assistant_message(
         &mut self,
-        mut message: RetainedUserMessage,
+        message: RetainedUserMessage,
         source: RetainedInputSource,
         item_id_generator: &ItemIdGenerator,
+    ) -> Option<RetainedSource> {
+        self.record_assistant_message_with_revision(message, source, || {
+            item_id_generator("retained")
+        })
+    }
+
+    pub(super) fn record_assistant_message_with_revision(
+        &mut self,
+        mut message: RetainedUserMessage,
+        source: RetainedInputSource,
+        revision: impl FnOnce() -> codex_protocol::ResponseItemId,
     ) -> Option<RetainedSource> {
         if source == RetainedInputSource::Local(None) {
             // Leave unsequenced sources to legacy transcript selection. Missing
@@ -72,10 +83,7 @@ impl RetainedContext {
         if empty {
             return None;
         }
-        let revision = message
-            .message_id
-            .as_ref()
-            .map(|_| item_id_generator("retained"));
+        let revision = message.message_id.as_ref().map(|_| revision());
         let entry = Ordered {
             revision,
             inherited,
diff --git a/codex-rs/history/src/retained_context.rs b/codex-rs/history/src/retained_context.rs
index f883348845..50782c183c 100644
--- a/codex-rs/history/src/retained_context.rs
+++ b/codex-rs/history/src/retained_context.rs
@@ -179,6 +179,9 @@ pub enum RetainedContextEvent {
         #[serde(flatten)]
         message: RetainedUserMessage,
         acceptance_order: u64,
+        /// The host-captured evidence revision. Older deliveries only persisted the call ID.
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        retained_source: Option<RetainedSource>,
     },
 }
 
@@ -477,16 +480,24 @@ impl RetainedContext {
         event: &RetainedContextEvent,
         item_id_generator: &ItemIdGenerator,
     ) -> bool {
-        let mut event = event.clone();
+        self.record_and_capture(&mut event.clone(), item_id_generator)
+    }
+
+    /// Records a host event and fills in its retained source for rollout persistence.
+    pub fn record_and_capture(
+        &mut self,
+        event: &mut RetainedContextEvent,
+        item_id_generator: &ItemIdGenerator,
+    ) -> bool {
         event.bound();
         match event {
             RetainedContextEvent::AcceptedFileAudio { evidence } => {
                 if !evidence.fits_record_budget()
-                    || self.accepted_file_audio.as_ref() == Some(&evidence)
+                    || self.accepted_file_audio.as_ref() == Some(evidence)
                 {
                     return false;
                 }
-                self.accepted_file_audio = Some(evidence);
+                self.accepted_file_audio = Some(Arc::clone(evidence));
                 true
             }
             RetainedContextEvent::VerifiedAnswer {
@@ -497,17 +508,17 @@ impl RetainedContext {
                     existing.value.turn_id == answer.turn_id
                         && existing.value.call_id == answer.call_id
                 }) {
-                    if self.verified_answers[index].value == answer {
+                    if self.verified_answers[index].value == *answer {
                         return false;
                     }
                     self.verified_answers.remove(index);
                 }
-                let order = self.record_order(acceptance_order);
+                let order = self.record_order(*acceptance_order);
                 self.verified_answers.push_back(Ordered {
                     revision: None,
                     inherited: false,
                     order,
-                    value: answer,
+                    value: answer.clone(),
                 });
                 bound_family(
                     &mut self.verified_answers,
@@ -518,19 +529,26 @@ impl RetainedContext {
             RetainedContextEvent::DeliveredAssistantMessage {
                 message,
                 acceptance_order,
+                retained_source,
             } => {
-                if self.assistant_messages.iter().any(|entry| {
+                if let Some(existing) = self.assistant_messages.iter().find(|entry| {
                     message.message_id.is_some()
                         && entry.value.message_id == message.message_id
-                        && entry.value == message
+                        && entry.value == *message
                         && !entry.inherited
                 }) {
+                    *retained_source = existing.source(RetainedSourceRole::Assistant);
                     return false;
                 }
-                self.record_assistant_message(
-                    message,
-                    RetainedInputSource::Local(Some(acceptance_order)),
-                    item_id_generator,
+                *retained_source = self.record_assistant_message_with_revision(
+                    message.clone(),
+                    RetainedInputSource::Local(Some(*acceptance_order)),
+                    || {
+                        retained_source.as_ref().map_or_else(
+                            || item_id_generator("retained"),
+                            |source| source.revision.clone(),
+                        )
+                    },
                 );
                 true
             }
diff --git a/codex-rs/history/src/retained_context_tests.rs b/codex-rs/history/src/retained_context_tests.rs
index 8d71cf59fa..aac0179ebc 100644
--- a/codex-rs/history/src/retained_context_tests.rs
+++ b/codex-rs/history/src/retained_context_tests.rs
@@ -51,6 +51,7 @@ fn publish_answer() -> RetainedContextEvent {
 
 fn delivered_message(id: &str, text: &str, acceptance_order: u64) -> RetainedContextEvent {
     RetainedContextEvent::DeliveredAssistantMessage {
+        retained_source: None,
         message: RetainedUserMessage {
             origin: crate::UserInputOrigin::User,
             turn_id: "turn-1".to_owned(),
diff --git a/codex-rs/history/src/rollout_payload.rs b/codex-rs/history/src/rollout_payload.rs
index 869195968b..bebb049358 100644
--- a/codex-rs/history/src/rollout_payload.rs
+++ b/codex-rs/history/src/rollout_payload.rs
@@ -218,6 +218,7 @@ impl<'a> From<&'a RolloutItem> for RolloutItemWire<'a> {
             RolloutItem::RetainedContext(RetainedContextEvent::DeliveredAssistantMessage {
                 message,
                 acceptance_order,
+                retained_source,
             }) => {
                 // Earlier clients preserve this as genuine assistant context, including across compaction.
                 let text = if message.complete {
@@ -256,6 +257,7 @@ impl<'a> From<&'a RolloutItem> for RolloutItemWire<'a> {
                         id_allocation: None,
                     },
                     metadata: Some(Cow::Owned(CodexHarnessMetadata {
+                        retained_source: retained_source.clone(),
                         delivered_assistant_message: Some(marker),
                         user_input_order: Some(*acceptance_order),
                         ..Default::default()
@@ -323,6 +325,7 @@ impl From<RolloutItemWire<'_>> for RolloutItem {
                                 phase: None,
                             },
                             acceptance_order,
+                            retained_source: metadata.retained_source.clone(),
                         },
                     );
                 }
diff --git a/codex-rs/history/src/tests.rs b/codex-rs/history/src/tests.rs
index 670388dc68..a8965d8e2e 100644
--- a/codex-rs/history/src/tests.rs
+++ b/codex-rs/history/src/tests.rs
@@ -1,5 +1,6 @@
 use anyhow::Result;
 use codex_protocol::ContextWindowId;
+use codex_protocol::ResponseItemId;
 use codex_protocol::models::AudioReference;
 use codex_protocol::models::ConfigurationReasoning;
 use codex_protocol::models::PermissionProfile;
@@ -366,7 +367,8 @@ fn delivered_assistant_rollout_survives_an_earlier_read_and_rewrite() -> Result<
     }
 
     for complete in [true, false] {
-        let original = RetainedContextEvent::DeliveredAssistantMessage {
+        let mut original = RetainedContextEvent::DeliveredAssistantMessage {
+            retained_source: None,
             message: RetainedUserMessage {
                 origin: crate::UserInputOrigin::User,
                 turn_id: "root-turn".to_owned(),
@@ -377,6 +379,14 @@ fn delivered_assistant_rollout_survives_an_earlier_read_and_rewrite() -> Result<
             },
             acceptance_order: 7,
         };
+        let sequence = std::sync::Mutex::new(
+            codex_utils_model_facing_id::ModelFacingIdGenerator::new(/*seed*/ 42, "item"),
+        );
+        let generator: codex_protocol::ItemIdGenerator = Arc::new(move |kind| {
+            ResponseItemId::generated(kind, sequence.lock().unwrap().fetch_next())
+        });
+        let mut live = RetainedContext::default();
+        assert!(live.record_and_capture(&mut original, &generator));
         let wire = serde_json::to_value(RolloutItem::RetainedContext(original.clone()))?;
         let earlier = serde_json::from_value::<EarlierRolloutItem>(wire)?;
         let EarlierRolloutItem::ResponseItem { payload, metadata } = &earlier;
@@ -432,6 +442,13 @@ fn delivered_assistant_rollout_survives_an_earlier_read_and_rewrite() -> Result<
             panic!("new readers need the model-invisible delivery event");
         };
         assert_eq!(restored, original);
+        let mut replayed = RetainedContext::default();
+        assert!(replayed.record(&restored, &generator));
+        assert_eq!(replayed, live);
+        assert_eq!(
+            crate::next_model_id_ordinals(&[RolloutItem::RetainedContext(restored)]),
+            (1, 0)
+        );
     }
     Ok(())
 }
@@ -679,6 +696,7 @@ fn compacted_replacement_history_stores_metadata_in_an_aligned_sidecar() -> Resu
 #[test]
 fn compacted_resume_metadata_presence_round_trips_empty_values() -> Result<()> {
     let resume_metadata = CompactionResumeMetadata {
+        next_item_ordinal: None,
         rejected_audio_file_ids: Default::default(),
         dynamic_tools: None,
         multi_agent_version: None,
@@ -792,6 +810,7 @@ fn compacted_metadata_remains_compatible_with_legacy_response_item_readers() ->
         compaction_response_id: None,
         latest_token_usage_record: None,
         resume_metadata: Some(CompactionResumeMetadata {
+            next_item_ordinal: None,
             rejected_audio_file_ids: Default::default(),
             dynamic_tools: None,
             multi_agent_version: Some(MultiAgentVersion::V2),
@@ -1158,6 +1177,46 @@ fn compacted_item_serializes_window_number_and_id() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn model_id_ordinals_resume_at_the_checkpoint_and_advance_for_local_items() -> Result<()> {
+    let record = |ordinal| {
+        json!({
+            "type": "response_item", "payload": {"type": "message", "role": "assistant", "content": [],
+            "id": "external", "id_allocation": {"salt": "item", "ordinal": ordinal, "value": 3}}
+        })
+    };
+    let source = |ordinal| {
+        json!({
+            "id": {"turn_id": "turn", "message_id": "external", "role": "assistant"},
+            "revision": {"id": "retained_item007",
+                "id_allocation": {"prefix": "retained", "salt": "item", "ordinal": ordinal, "value": 7}},
+            "complete": true
+        })
+    };
+    let mut tail = record(24);
+    tail["metadata"] = json!({
+        "retained_source": source(25),
+        "guardian_sources": [source(300)],
+        "guardian_review_ids": [{"id": "review_item008",
+            "id_allocation": {"prefix": "review", "salt": "item", "ordinal": 301, "value": 8}}]
+    });
+    let records: Vec<RolloutItem> = serde_json::from_value(json!([
+        record(19),
+        {"type": "compacted", "payload": {
+            "message": "", "window_number": 4,
+            "window_id": {"salt": "window", "ordinal": 4, "value": 812},
+            "replacement_history": [record(8)["payload"]],
+            "resume_metadata": {"next_item_ordinal": 24}
+        }},
+        tail
+    ]))?;
+    assert_eq!(crate::next_model_id_ordinals(&[]), (0, 0));
+    assert_eq!(crate::next_model_id_ordinals(&records[1..2]), (24, 5));
+    assert_eq!(crate::next_model_id_ordinals(&records[1..]), (26, 5));
+    assert_eq!(crate::next_model_id_ordinals(&records), (26, 5));
+    Ok(())
+}
+
 #[test]
 fn structured_window_ids_round_trip_in_session_metadata_and_compaction() -> Result<()> {
     let uuid = "019020ef-10ff-7000-8000-000000000001";
diff --git a/codex-rs/thread-store/src/local/model_context_tests.rs b/codex-rs/thread-store/src/local/model_context_tests.rs
index 646c1f12ff..472d8b811f 100644
--- a/codex-rs/thread-store/src/local/model_context_tests.rs
+++ b/codex-rs/thread-store/src/local/model_context_tests.rs
@@ -95,6 +95,14 @@ async fn stops_at_newest_usable_compaction_and_keeps_companions() {
     let thread_id = ThreadId::from_string(&uuid.to_string()).expect("thread id");
     let world_state = RolloutItem::WorldState(WorldStateItem::full(Default::default()));
     let turn_context = turn_context(home.path(), "companion");
+    let checkpoint: RolloutItem = serde_json::from_value(serde_json::json!({
+        "type": "compacted", "payload": {
+            "message": "latest compaction", "replacement_history": [], "window_number": 2,
+            "window_id": {"salt": "window", "ordinal": 2, "value": 6},
+            "resume_metadata": {"next_item_ordinal": 24}
+        }
+    }))
+    .expect("seeded checkpoint");
     let path = write_paginated_rollout(
         home.path(),
         "2025-01-03T13-00-00",
@@ -103,7 +111,7 @@ async fn stops_at_newest_usable_compaction_and_keeps_companions() {
             user_message("older history"),
             compacted("older compaction", Some(Vec::new())),
             user_message("superseded suffix"),
-            compacted("latest compaction", Some(Vec::new())),
+            checkpoint.clone(),
             world_state.clone(),
             turn_context.clone(),
         ],
@@ -125,7 +133,7 @@ async fn stops_at_newest_usable_compaction_and_keeps_companions() {
         serde_json::to_value(context.items).expect("serialize context"),
         serde_json::to_value(vec![
             RolloutItem::SessionMeta(Box::new(session_meta)),
-            compacted("latest compaction", Some(Vec::new())),
+            checkpoint,
             world_state,
             turn_context,
         ])
@@ -272,6 +280,7 @@ async fn fork_version_stops_before_older_segments_once_resolved() {
             unreachable!();
         };
         compacted.resume_metadata = Some(codex_rollout::CompactionResumeMetadata {
+            next_item_ordinal: None,
             rejected_audio_file_ids: Default::default(),
             dynamic_tools: None,
             multi_agent_version: Some(MultiAgentVersion::V2),
diff --git a/codex-rs/thread-store/src/local/rollout_migration/rollback_plan.rs b/codex-rs/thread-store/src/local/rollout_migration/rollback_plan.rs
index 4b52fbe44d..12ae33c540 100644
--- a/codex-rs/thread-store/src/local/rollout_migration/rollback_plan.rs
+++ b/codex-rs/thread-store/src/local/rollout_migration/rollback_plan.rs
@@ -312,6 +312,7 @@ impl RollbackPlanner {
                 codex_rollout::RetainedContextEvent::DeliveredAssistantMessage {
                     message,
                     acceptance_order,
+                    ..
                 },
             ) => {
                 // Nested calls have no response item; match them to instructions by acceptance order.