Sanitize legacy context compaction history

codex-rs/core/src/context_manager/history.rs

@@ -359,6 +359,8 @@ impl ContextManager {
     /// 2. every output has a corresponding call entry
     /// 3. when images are unsupported, image content is stripped from messages and tool outputs
     fn normalize_history(&mut self, input_modalities: &[InputModality]) {
+        normalize_legacy_context_compaction_items(&mut self.items);
+
         // all function/tool calls must have a corresponding output
         normalize::ensure_call_outputs_present(&mut self.items);
 
@@ -390,6 +392,11 @@ impl ContextManager {
                 name: name.clone(),
                 output: truncate_function_output_payload(output, policy_with_serialization_budget),
             },
+            ResponseItem::ContextCompaction {
+                encrypted_content: Some(encrypted_content),
+            } => ResponseItem::Compaction {
+                encrypted_content: encrypted_content.clone(),
+            },
             ResponseItem::Message { .. }
             | ResponseItem::Reasoning { .. }
             | ResponseItem::LocalShellCall { .. }
@@ -454,6 +461,21 @@ impl ContextManager {
     }
 }
 
+fn normalize_legacy_context_compaction_items(items: &mut Vec<ResponseItem>) {
+    *items = std::mem::take(items)
+        .into_iter()
+        .filter_map(|item| match item {
+            ResponseItem::ContextCompaction {
+                encrypted_content: Some(encrypted_content),
+            } => Some(ResponseItem::Compaction { encrypted_content }),
+            ResponseItem::ContextCompaction {
+                encrypted_content: None,
+            } => None,
+            item => Some(item),
+        })
+        .collect();
+}
+
 pub(crate) fn truncate_function_output_payload(
     output: &FunctionCallOutputPayload,
     policy: TruncationPolicy,
@@ -490,9 +512,14 @@ fn is_api_message(message: &ResponseItem) -> bool {
         | ResponseItem::WebSearchCall { .. }
         | ResponseItem::ImageGenerationCall { .. }
         | ResponseItem::Compaction { .. }
-        | ResponseItem::ContextCompaction { .. } => true,
-        ResponseItem::CompactionTrigger => false,
-        ResponseItem::Other => false,
+        | ResponseItem::ContextCompaction {
+            encrypted_content: Some(_),
+        } => true,
+        ResponseItem::ContextCompaction {
+            encrypted_content: None,
+        }
+        | ResponseItem::CompactionTrigger
+        | ResponseItem::Other => false,
     }
 }
 

codex-rs/core/src/context_manager/history_tests.rs

@@ -306,6 +306,46 @@ fn for_prompt_preserves_inter_agent_assistant_messages() {
     assert_eq!(history.for_prompt(&default_input_modalities()), vec![item]);
 }
 
+#[test]
+fn legacy_context_compaction_items_are_not_sent_to_prompt() {
+    let legacy_compaction = ResponseItem::ContextCompaction {
+        encrypted_content: Some("encrypted-legacy-context".to_string()),
+    };
+    let lifecycle_marker = ResponseItem::ContextCompaction {
+        encrypted_content: None,
+    };
+    let history = create_history_with_items(vec![legacy_compaction, lifecycle_marker]);
+
+    assert_eq!(
+        history.raw_items(),
+        vec![ResponseItem::Compaction {
+            encrypted_content: "encrypted-legacy-context".to_string(),
+        }]
+    );
+
+    let user = user_msg("after compaction");
+    let mut history = ContextManager::new();
+    history.replace(vec![
+        ResponseItem::ContextCompaction {
+            encrypted_content: Some("encrypted-legacy-context".to_string()),
+        },
+        ResponseItem::ContextCompaction {
+            encrypted_content: None,
+        },
+        user.clone(),
+    ]);
+
+    assert_eq!(
+        history.for_prompt(&default_input_modalities()),
+        vec![
+            ResponseItem::Compaction {
+                encrypted_content: "encrypted-legacy-context".to_string(),
+            },
+            user,
+        ]
+    );
+}
+
 #[test]
 fn drop_last_n_user_turns_treats_inter_agent_assistant_messages_as_instruction_turns() {
     let first_turn = user_input_text_msg("first");