fix: preserve run budget across segment forks

crates/worker/src/worker.rs

@@ -2889,15 +2889,23 @@ impl<C: LlmClient, St: Store> Worker<C, St> {
             }),
             compacted_from: None,
         };
+        let mut initial_entries = vec![entry.clone()];
+        if let Some(checkpoint) =
+            active_run_checkpoint_entry(w.active_run_turn_count(), w.turn_count())
+        {
+            initial_entries.push(checkpoint);
+        }
         self.store
-            .create_segment(loc.session_id, fork_segment_id, &[entry.clone()])
+            .create_segment(loc.session_id, fork_segment_id, &initial_entries)
             .map_err(WorkerError::from)?;
         self.segment_state.set_location(SegmentLocation {
             session_id: loc.session_id,
             segment_id: fork_segment_id,
         });
-        self.segment_state.set_entries_written(1);
-        self.sink.reset_with_initial(entry);
+        self.segment_state
+            .set_entries_written(initial_entries.len());
+        self.sink
+            .reset_with_initial_entries(initial_entries.clone());
         if self.scope_allocation.is_some() {
             worker_allocation::update_segment(&self.manifest.worker.name, fork_segment_id)?;
         }
@@ -7031,6 +7039,65 @@ mod build_summary_prompt_tests {
         assert_eq!(restored.active_run_turn_count, None);
     }
 
+    #[tokio::test]
+    async fn auto_fork_checkpoints_interrupted_run_budget_for_restore() {
+        let dir = tempfile::tempdir().unwrap();
+        let store = session_store::FsStore::new(dir.path().join("sessions")).unwrap();
+        let mut worker = Worker::new(
+            minimal_manifest(),
+            Engine::new(NoopClient),
+            store,
+            WorkerWorkspaceContext::no_workspace(),
+            WorkerFilesystemAuthority::None,
+            Scope::empty(),
+        )
+        .await
+        .unwrap();
+        worker.ensure_segment_head().unwrap();
+        worker.engine_mut().set_turn_count(7);
+        worker.engine_mut().set_last_run_interrupted(true);
+        worker.engine_mut().set_active_run_turn_count(Some(3));
+
+        let session_id = worker.session_id();
+        let source_segment_id = worker.segment_id();
+        worker
+            .store()
+            .append(
+                session_id,
+                source_segment_id,
+                &LogEntry::Extension {
+                    ts: segment_log::now_millis(),
+                    domain: "test.auto_fork_drift".into(),
+                    payload: serde_json::json!({}),
+                },
+            )
+            .unwrap();
+
+        worker.ensure_segment_head().unwrap();
+
+        let fork_segment_id = worker.segment_id();
+        assert_ne!(fork_segment_id, source_segment_id);
+        let fork_entries = worker
+            .store()
+            .read_all(session_id, fork_segment_id)
+            .unwrap();
+        assert!(matches!(
+            fork_entries.as_slice(),
+            [
+                LogEntry::SegmentStart { .. },
+                LogEntry::ActiveRunCheckpoint {
+                    active_turn_count: 3,
+                    total_turn_count: 7,
+                    ..
+                }
+            ]
+        ));
+        let restored = session_store::collect_state(&fork_entries);
+        assert!(restored.last_run_interrupted);
+        assert_eq!(restored.turn_count, 7);
+        assert_eq!(restored.active_run_turn_count, Some(3));
+    }
+
     #[tokio::test]
     async fn flow_transition_feature_installs_runtime_local_coordinator() {
         let dir = tempfile::tempdir().unwrap();