Let a plan name one task twice, and number its nodes

client/platform_client/eval_plan.py

@@ -164,6 +164,8 @@ class TaskNode(Cascade):
 
     task_id: TaskRef
     endpoints: list[Endpoint] | None = Field(default=None, min_length=1)
+    # This node's index in the plan's task list, stamped by `EvalPlan._number_the_nodes`.
+    position: int = Field(default=0, ge=0, exclude=True)
 
     @model_validator(mode='before')
     @classmethod
@@ -223,8 +225,15 @@ def _states_a_count(self) -> Self:
         return self
 
     @model_validator(mode='after')
-    def _each_task_appears_once(self) -> Self:
-        _require_unique_names([task.task_id for task in self.tasks], 'the plan')
+    def _number_the_nodes(self) -> Self:
+        """Stamp each node with its place in the list, which identifies it.
+
+        A plan may name one catalogue task twice, each node with its own scene, so `task_id` names
+        no single node and the position does. The stamp overwrites a value a caller sent: the index
+        is the only answer consistent with where the node sits.
+        """
+        for position, task in enumerate(self.tasks):
+            task.position = position
         return self
 
     @model_validator(mode='after')

client/platform_client/tests/test_eval_plan.py

@@ -240,15 +240,37 @@ def test_an_endpoint_says_whether_it_names_a_locator():
     assert Endpoint(name='baseline', url='wss://x/ws').names_a_locator is True
 
 
-def test_a_plan_names_each_task_and_each_endpoint_once():
-    with pytest.raises(ValidationError, match='more than once'):
-        a_plan(tasks=[SPOONS, SPOONS])
+def test_a_plan_names_each_endpoint_once():
     with pytest.raises(ValidationError, match='more than once'):
         a_plan(endpoints=[BASELINE, BASELINE])
     with pytest.raises(ValidationError, match='more than once'):
         TaskNode.model_validate({'task_id': SPOONS, 'endpoints': [{'name': 'e'}, {'name': 'e'}]})
 
 
+def test_a_plan_may_name_one_task_twice():
+    """Two nodes of one task, each with its own scene, is a plan the platform runs. The position
+    keeps them apart; the id cannot."""
+    plan = a_plan(tasks=[SPOONS, SPOONS])
+
+    assert [task.task_id for task in plan.tasks] == [SPOONS, SPOONS]
+    assert [task.position for task in plan.tasks] == [0, 1]
+
+
+def test_every_node_is_numbered_by_its_place_in_the_list():
+    plan = a_plan(tasks=[SPOONS, {'task_id': SPOONS, 'episodes_per_endpoint': 2}, SPOONS])
+
+    assert [task.position for task in plan.tasks] == [0, 1, 2]
+
+
+def test_a_position_a_caller_states_is_the_list_order_regardless():
+    """The index identifies the node, so a sent value cannot disagree with where it sits — and the
+    field never goes out on the wire for a caller to have sent one in the first place."""
+    plan = a_plan(tasks=[{'task_id': SPOONS, 'position': 7}, SPOONS])
+
+    assert [task.position for task in plan.tasks] == [0, 1]
+    assert 'position' not in plan.model_dump()['tasks'][0]
+
+
 def test_a_task_endpoint_naming_no_locator_names_one_the_plan_defines():
     with pytest.raises(ValidationError, match='name no endpoint the plan defines'):
         a_plan(tasks=[{'task_id': SPOONS, 'endpoints': ['elsewhere']}])

client/pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "positronic-platform-client"
-version = "0.7.0"
+version = "0.8.0"
 description = "Typed wire contract and HTTP client for the Positronic evaluation platform API"
 readme = "README.md"
 requires-python = ">=3.11"

pyproject.toml

@@ -39,7 +39,7 @@ dependencies = [
     # (.github/workflows/release.yaml). Pinned exactly, because that package guarantees no
     # backwards compatibility: a floating requirement would let a fresh install of THIS release
     # resolve a contract it was never built against.
-    "positronic-platform-client==0.7.0",
+    "positronic-platform-client==0.8.0",
     "psutil",  # `positronic-server` enumerates local interfaces to name a wildcard bind's addresses
     "pyarrow",
     "pydantic",