Remove stale checkpoints to prevent The Clash

Author: americalexander

activitysim/core/calibration.py

@@ -1484,6 +1484,13 @@ def _run_in_configured_mode(
             # downstream code can reference it by name.
             if not state.checkpoint.store_is_open():
                 state.checkpoint.restore(resume_after="_")
+            # Truncate checkpoint history to only the current restored state.
+            # Without this, model names from a prior complete run remain in
+            # self.checkpoints and trigger DuplicateWorkflowNameError when
+            # those models need to re-run later in the calibration loop
+            # (Runner's "good to go" fast-path skips the truncation that
+            # checkpoint.restore normally provides).
+            state.checkpoint.checkpoints = state.checkpoint.checkpoints[-1:]
             state.checkpoint.add(original_last_model)
             return
 
@@ -1573,6 +1580,14 @@ def _restore_parent_state_from_pipeline(state: workflow.State) -> None:
         state.checkpoint.close_store()
     state.checkpoint.restore(resume_after="_")
 
+    # Truncate checkpoint history to only the current restored state.
+    # Without this, model-level checkpoint names from a prior run remain
+    # visible in self.checkpoints.  When Runner.__call__ later takes its
+    # "good to go" fast-path (skipping checkpoint.restore and its built-in
+    # history truncation), _pre_run_step sees those stale names and raises
+    # DuplicateWorkflowNameError for models that legitimately need to re-run.
+    state.checkpoint.checkpoints = state.checkpoint.checkpoints[-1:]
+
     # After restore, all tables are clean (status=False). Mark them dirty so
     # the next checkpoint.add() writes them to disk at a known checkpoint name.
     # This ensures apportion subprocesses find table files at a single,