Centralize compacted rollout item construction (#34533)

## What changed

- Pass only compaction message and window metadata into
  `Session::replace_compacted_history`.
- Build the persisted `CompactedItem` there after assigning any missing response
  item IDs, so its replacement history matches the live history without callers
  cloning or assembling it themselves.

GitOrigin-RevId: a6106c33b6d3eef39ac0b563a50e17f6782970dc

codex-rs/core/src/compact.rs

@@ -18,6 +18,7 @@ use crate::session::session::Session;
 use crate::session::step_context::StepContext;
 use crate::session::turn::get_last_assistant_message_from_turn;
 use crate::session::turn_context::TurnContext;
+use crate::state::AutoCompactWindowIds;
 use crate::util::backoff;
 use codex_analytics::CodexCompactionEvent;
 use codex_analytics::CompactionImplementation;
@@ -35,7 +36,6 @@ use codex_protocol::models::ContentItem;
 use codex_protocol::models::InternalChatMessageMetadataPassthrough;
 use codex_protocol::models::ResponseInputItem;
 use codex_protocol::models::ResponseItem;
-use codex_protocol::protocol::CompactedItem;
 use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::RawResponseCompletedEvent;
 use codex_protocol::protocol::TurnStartedEvent;
@@ -72,6 +72,16 @@ pub(crate) enum InitialContextInjection {
     DoNotInject,
 }
 
+/// Metadata for a new compaction checkpoint, kept separate from its replacement history.
+///
+/// `Session::replace_compacted_history` assigns missing item IDs before constructing the persisted
+/// `CompactedItem`, ensuring the live and persisted histories remain identical.
+pub(crate) struct CompactedHistoryMetadata {
+    pub(crate) message: String,
+    pub(crate) window_number: u64,
+    pub(crate) window_ids: AutoCompactWindowIds,
+}
+
 pub(crate) async fn build_compaction_initial_context(
     sess: &Session,
     initial_context_injection: &InitialContextInjection,
@@ -357,20 +367,16 @@ async fn run_compact_task_inner_impl(
             Some(turn_context.to_turn_context_item())
         }
     };
-    let compacted_item = CompactedItem {
-        message: summary_text.clone(),
-        replacement_history: Some(new_history.clone()),
-        window_number: Some(window_number),
-        first_window_id: Some(window_ids.first_window_id.to_string()),
-        previous_window_id: window_ids.previous_window_id.map(|id| id.to_string()),
-        window_id: Some(window_ids.window_id.to_string()),
-    };
     sess.replace_compacted_history(
         turn_context.as_ref(),
         new_history,
         reference_context_item,
         world_state_baseline,
-        compacted_item,
+        CompactedHistoryMetadata {
+            message: summary_text,
+            window_number,
+            window_ids,
+        },
     )
     .await;
     sess.recompute_token_usage(&turn_context).await;

codex-rs/core/src/compact_remote.rs

@@ -1,6 +1,7 @@
 use std::sync::Arc;
 use std::sync::OnceLock;
 
+use crate::compact::CompactedHistoryMetadata;
 use crate::compact::CompactionAnalyticsAttempt;
 use crate::compact::CompactionAnalyticsDetails;
 use crate::compact::InitialContextInjection;
@@ -32,7 +33,6 @@ use codex_protocol::models::BaseInstructions;
 use codex_protocol::models::FunctionCallOutputBody;
 use codex_protocol::models::FunctionCallOutputPayload;
 use codex_protocol::models::ResponseItem;
-use codex_protocol::protocol::CompactedItem;
 use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::TurnStartedEvent;
 use codex_rollout_trace::CompactionCheckpointTracePayload;
@@ -269,14 +269,6 @@ async fn run_remote_compact_task_inner_impl(
             Some(compaction_turn_context.to_turn_context_item())
         }
     };
-    let compacted_item = CompactedItem {
-        message: String::new(),
-        replacement_history: Some(new_history.clone()),
-        window_number: Some(new_window_number),
-        first_window_id: Some(new_window_ids.first_window_id.to_string()),
-        previous_window_id: new_window_ids.previous_window_id.map(|id| id.to_string()),
-        window_id: Some(new_window_ids.window_id.to_string()),
-    };
     // Install is the semantic boundary where the compact endpoint's output becomes live
     // thread history. Keep it distinct from the later inference request so the reducer can
     // still represent repeated developer/context prefix items exactly as the model saw them.
@@ -291,7 +283,11 @@ async fn run_remote_compact_task_inner_impl(
         new_history,
         reference_context_item,
         world_state_baseline,
-        compacted_item,
+        CompactedHistoryMetadata {
+            message: String::new(),
+            window_number: new_window_number,
+            window_ids: new_window_ids,
+        },
     )
     .await;
     sess.recompute_token_usage(compaction_turn_context).await;

codex-rs/core/src/compact_remote_v2.rs

@@ -4,6 +4,7 @@ use crate::Prompt;
 use crate::ResponseStream;
 use crate::client::ModelClientSession;
 use crate::client_common::ResponseEvent;
+use crate::compact::CompactedHistoryMetadata;
 use crate::compact::CompactionAnalyticsAttempt;
 use crate::compact::CompactionAnalyticsDetails;
 use crate::compact::InitialContextInjection;
@@ -33,7 +34,6 @@ use codex_protocol::items::ContextCompactionItem;
 use codex_protocol::items::TurnItem;
 use codex_protocol::models::ContentItem;
 use codex_protocol::models::ResponseItem;
-use codex_protocol::protocol::CompactedItem;
 use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::TokenUsage;
 use codex_protocol::protocol::TruncationPolicy;
@@ -293,14 +293,6 @@ async fn run_remote_compact_task_inner_impl(
             Some(compaction_turn_context.to_turn_context_item())
         }
     };
-    let compacted_item = CompactedItem {
-        message: String::new(),
-        replacement_history: Some(new_history.clone()),
-        window_number: Some(new_window_number),
-        first_window_id: Some(new_window_ids.first_window_id.to_string()),
-        previous_window_id: new_window_ids.previous_window_id.map(|id| id.to_string()),
-        window_id: Some(new_window_ids.window_id.to_string()),
-    };
     if let Some(trace_input_history) = trace_input_history.as_deref() {
         compaction_trace.record_installed(&CompactionCheckpointTracePayload {
             input_history: trace_input_history,
@@ -312,7 +304,11 @@ async fn run_remote_compact_task_inner_impl(
         new_history,
         reference_context_item,
         world_state_baseline,
-        compacted_item,
+        CompactedHistoryMetadata {
+            message: String::new(),
+            window_number: new_window_number,
+            window_ids: new_window_ids,
+        },
     )
     .await;
     sess.recompute_token_usage(compaction_turn_context).await;

codex-rs/core/src/session/mod.rs

@@ -20,6 +20,7 @@ use crate::attestation::AttestationProvider;
 use crate::audio_preparation::prepare_response_items as prepare_audio_response_items;
 use crate::build_available_skills;
 use crate::compact;
+use crate::compact::CompactedHistoryMetadata;
 use crate::config::ManagedFeatures;
 use crate::config::resolve_tool_suggest_config_from_layer_stack;
 use crate::context::ApprovedCommandPrefixSaved;
@@ -3052,7 +3053,7 @@ impl Session {
         items: Vec<ResponseItem>,
         reference_context_item: Option<TurnContextItem>,
         world_state_baseline: Option<Arc<WorldState>>,
-        compacted_item: CompactedItem,
+        metadata: CompactedHistoryMetadata,
     ) {
         let items = if turn_context.item_ids_enabled() {
             Self::assign_missing_response_item_ids(Cow::Owned(items)).into_owned()
@@ -3060,8 +3061,15 @@ impl Session {
             items
         };
         let compacted_item = CompactedItem {
+            message: metadata.message,
             replacement_history: Some(items.clone()),
-            ..compacted_item
+            window_number: Some(metadata.window_number),
+            first_window_id: Some(metadata.window_ids.first_window_id.to_string()),
+            previous_window_id: metadata
+                .window_ids
+                .previous_window_id
+                .map(|id| id.to_string()),
+            window_id: Some(metadata.window_ids.window_id.to_string()),
         };
         // Compaction starts a new history window, so its WorldState baseline must be full.
         let mut world_state_item = None;
@@ -3544,13 +3552,10 @@ impl Session {
             context_items,
             Some(turn_context_item),
             Some(world_state),
-            CompactedItem {
+            CompactedHistoryMetadata {
                 message: String::new(),
-                replacement_history: None,
+                window_number,
-                window_number: Some(window_number),
+                window_ids,
-                first_window_id: Some(window_ids.first_window_id.to_string()),
-                previous_window_id: window_ids.previous_window_id.map(|id| id.to_string()),
-                window_id: Some(window_ids.window_id.to_string()),
             },
         )
         .await;