Bugfix: loops checkpointed before 2026.10.22 could not resume

HISTORY.rst

@@ -1,6 +1,14 @@
 =======
 History
 =======
+2026.10.22.1 -- Bugfix: loops checkpointed before 2026.10.22 could not resume
+    * A job with a loop that was checkpointed before 2026.10.22 refused to resume
+      unless its cores per iteration was changed to automatic. It now resumes
+      unchanged too (needs seamm 2026.10.22.1). Its other settings of how the
+      iterations run must still be as they were.
+    * The user guide now says that a resume refused because a setting changed runs
+      nothing, rather than starting the job from the top.
+
 2026.10.22 -- Bugfix: a parallel loop's iterations share the job's cores
     * A parallel loop gave each iteration one core by default, so four replicas in a
       64-core job ran on four cores (job 5368). "Cores per iteration" now defaults to

docs/user_guide/index.rst

@@ -156,8 +156,11 @@ own checkpoints. An iteration whose evaluator was killed while the job ran on
 
 The settings above that say only how the iterations run -- iterations at once,
 cores, memory and time per iteration, and where the calculations run -- can be
-changed before resuming, e.g. to give the iterations more cores; changing any
-other setting makes the job start again from the top.
+changed before resuming, e.g. to give the iterations more cores. Changing any
+other setting stops the resume: nothing is run, and ``job.out`` says why. A job
+checkpointed before seamm 2026.10.22 resumes only with these settings as they
+were, except that cores per iteration 1, the default then, may be set to
+automatic.
 
 Index
 =====

loop_step/loop_parameters.py

@@ -238,6 +238,8 @@ class LoopParameters(seamm.Parameters):
         "cores per iteration": {
             "resource": True,
             "default": "automatic",
+            # Until 2026.10.22: checkpoints written then still resume
+            "former defaults": ("1",),
             "kind": "integer",
             "default_units": "",
             "enumeration": ("automatic",),

requirements.txt

@@ -1,4 +1,4 @@
 molsystem>=2026.10.17
 psutil
-seamm>=2026.10.22
+seamm>=2026.10.22.1
 seamm-exec>=2026.10.5

tests/test_loop_step.py

@@ -55,3 +55,5 @@ def test_resource_parameters_are_marked():
     ):
         assert P[key]._data.get("resource") is True, key
     assert P["cores per iteration"].default == "automatic"
+    # Its default until 2026.10.22, for checkpoints written then
+    assert P["cores per iteration"]._data.get("former defaults") == ("1",)