diff --git a/.formatter.exs b/.formatter.exs
index 35bd347..174948b 100644
--- a/.formatter.exs
+++ b/.formatter.exs
@@ -15,6 +15,10 @@ spark_locals_without_parens = [
   feature: 1,
   feature: 2,
   id: 1,
+  inherited_party: 1,
+  inherited_party: 2,
+  inherited_place: 1,
+  inherited_place: 2,
   instance_ref: 2,
   is_enabled?: 1,
   major_version: 1,
diff --git a/AGENTS.md b/AGENTS.md
index 7faedc3..58c0036 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -271,6 +271,27 @@ Spark runs two separate pipelines during compilation, in this order:
 
 New transformers go under `transformers:`. New persisters go under `persisters:`.
 
+## DSL shape changes
+
+Whenever you add, rename, or remove a DSL entity or section in `Diffo.Provider.Extension`
+(or any Spark extension in this project), run this checklist in order:
+
+1. **Update `.formatter.exs`** — add new entity names to `spark_locals_without_parens` with
+   each supported arity. Without this, `mix format` will add unwanted parentheses to every
+   DSL call site.
+
+2. **Run `mix format`** — apply formatting across the codebase and verify the output looks
+   correct. Run `mix format --check-formatted` to confirm nothing was missed.
+
+3. **Run `mix spark.cheat_sheets`** — regenerates
+   `documentation/dsls/DSL-Diffo.Provider.Extension.md`. This file is Spark-generated;
+   never edit it by hand. Commit the regenerated file alongside the DSL change.
+
+4. **Run `mix test`** — confirm no regressions.
+
+Do not skip step 1 even for a "small" entity addition — the formatter will silently reformat
+every call site in CI and produce noisy diffs in future PRs.
+
 ## Raising upstream bugs
 
 When a bug is found in a dependency (e.g. AshNeo4j, Bolty), raise a GitHub issue on that
@@ -309,11 +330,8 @@ not. Add any useful hypotheses as a follow-up comment on the issue, then leave i
 - Using module names (e.g. `MyApp.CardInstance`) as role values in `relationships do` — roles are atoms like `:provides`, not module references.
 - Forgetting that `relationships do` omitted means `:none` for both source and target — any update action with `argument :relationships, {:array, :struct}` will fail unless the resource declares permissions.
 - Thinking the Assigner requires `relationships do` permissions — it does not. The Assigner writes `DefinedSimpleRelationship` records directly via the Provider domain; `ValidateRelationshipPermitted` only runs on actions that carry `argument :relationships, {:array, :struct}`, which the Assigner's `assign_*` actions do not.
-- Editing `documentation/dsls/DSL-Diffo.Provider.Extension.md` — it is Spark-generated;
-  run `mix spark.cheat_sheets` to regenerate it. Whenever you add, rename, or remove a DSL
-  entity or section, also check `.formatter.exs` — new entity names must be added to
-  `spark_locals_without_parens` (with each arity) so the Spark formatter omits parentheses.
-  Run `mix format` afterward to verify.
+- Editing `documentation/dsls/DSL-Diffo.Provider.Extension.md` — it is Spark-generated.
+  See the **DSL shape changes** section above for the full checklist.
 - Editing content between `<!-- usage-rules-start -->` markers in `CLAUDE.md` — that is
   auto-generated by `mix usage_rules.sync`.
 - Forgetting `Diffo.Provider.DomainFragment` on a scenario 3 domain — any domain whose
diff --git a/documentation/dsls/DSL-Diffo.Provider.Extension.md b/documentation/dsls/DSL-Diffo.Provider.Extension.md
index 4df32ff..90ab0c9 100644
--- a/documentation/dsls/DSL-Diffo.Provider.Extension.md
+++ b/documentation/dsls/DSL-Diffo.Provider.Extension.md
@@ -103,11 +103,13 @@ Provider DSL — structure, roles, and behaviour for this resource kind
    * parties
    * party_ref
    * role
+   * inherited_party
  * [places](#provider-places)
    * place
    * places
    * place_ref
    * role
+   * inherited_place
  * [instances](#provider-instances)
    * role
    * instance_ref
@@ -330,13 +332,14 @@ Declares an assignable pool — a named range of values for auto-assignment
 
 
 ### provider.parties
-Party roles on this resource — `party`/`parties`/`party_ref` for Instance kinds; `role` for Party and Place kinds
+Party roles on this resource — `party`/`parties`/`party_ref`/`inherited_party` for Instance kinds; `role` for Party and Place kinds
 
 ### Nested DSLs
  * [party](#provider-parties-party)
  * [parties](#provider-parties-parties)
  * [party_ref](#provider-parties-party_ref)
  * [role](#provider-parties-role)
+ * [inherited_party](#provider-parties-inherited_party)
 
 
 ### Examples
@@ -346,6 +349,7 @@ parties do
   party :provider, MyApp.Provider
   party_ref :owner, MyApp.InfrastructureCo
   parties :technicians, MyApp.Technician, constraints: [min: 1]
+  inherited_party :customer, source_role: :owner
 end
 
 # Party or Place
@@ -483,15 +487,48 @@ Declares a role this Party or Place kind plays with respect to other Parties
 
 Target: `Diffo.Provider.Extension.PartyRole`
 
+### provider.parties.inherited_party
+```elixir
+inherited_party role
+```
+
+
+Declares a party derived by traversing the assignment graph — generates a calculation, no PartyRef node created
+
+
+
+
+
+### Arguments
+
+| Name | Type | Default | Docs |
+|------|------|---------|------|
+| [`role`](#provider-parties-inherited_party-role){: #provider-parties-inherited_party-role .spark-required} | `atom` |  | The role name — also the default alias to follow on AssignmentRelationship. |
+### Options
+
+| Name | Type | Default | Docs |
+|------|------|---------|------|
+| [`source_role`](#provider-parties-inherited_party-source_role){: #provider-parties-inherited_party-source_role .spark-required} | `atom` |  | The PartyRef role to pick up on the arrived-at instance. |
+| [`via`](#provider-parties-inherited_party-via){: #provider-parties-inherited_party-via } | `list(atom)` |  | Sequence of assignment aliases to traverse. Defaults to [role] for single-hop. Use a list for multi-level. |
+
+
+
+
+
+### Introspection
+
+Target: `Diffo.Provider.Extension.InheritedPartyDeclaration`
+
 
 ### provider.places
-Place roles on this resource — `place`/`places`/`place_ref` for Instance kinds; `role` for Party and Place kinds
+Place roles on this resource — `place`/`places`/`place_ref`/`inherited_place` for Instance kinds; `role` for Party and Place kinds
 
 ### Nested DSLs
  * [place](#provider-places-place)
  * [places](#provider-places-places)
  * [place_ref](#provider-places-place_ref)
  * [role](#provider-places-role)
+ * [inherited_place](#provider-places-inherited_place)
 
 
 ### Examples
@@ -500,6 +537,8 @@ Place roles on this resource — `place`/`places`/`place_ref` for Instance kinds
 places do
   place :installation_site, MyApp.GeographicSite
   place_ref :billing_address, MyApp.GeographicAddress
+  inherited_place :a_end, source_role: :location
+  inherited_place :poi, via: [:cvc_link, :nni_link], source_role: :poi
 end
 
 # Party or Place
@@ -637,6 +676,38 @@ Declares a role this Party or Place kind plays with respect to Places
 
 Target: `Diffo.Provider.Extension.PlaceRole`
 
+### provider.places.inherited_place
+```elixir
+inherited_place role
+```
+
+
+Declares a place derived by traversing the assignment graph — generates a calculation, no PlaceRef node created
+
+
+
+
+
+### Arguments
+
+| Name | Type | Default | Docs |
+|------|------|---------|------|
+| [`role`](#provider-places-inherited_place-role){: #provider-places-inherited_place-role .spark-required} | `atom` |  | The role name — also the default alias to follow on AssignmentRelationship. |
+### Options
+
+| Name | Type | Default | Docs |
+|------|------|---------|------|
+| [`source_role`](#provider-places-inherited_place-source_role){: #provider-places-inherited_place-source_role .spark-required} | `atom` |  | The PlaceRef role to pick up on the arrived-at instance. |
+| [`via`](#provider-places-inherited_place-via){: #provider-places-inherited_place-via } | `list(atom)` |  | Sequence of assignment aliases to traverse. Defaults to [role] for single-hop. Use a list for multi-level. |
+
+
+
+
+
+### Introspection
+
+Target: `Diffo.Provider.Extension.InheritedPlaceDeclaration`
+
 
 ### provider.instances
 Declares the roles this Party or Place kind plays with respect to Instances
diff --git a/lib/diffo/provider/assigner/assigner.ex b/lib/diffo/provider/assigner/assigner.ex
index 92ca66c..fbc2229 100644
--- a/lib/diffo/provider/assigner/assigner.ex
+++ b/lib/diffo/provider/assigner/assigner.ex
@@ -62,11 +62,14 @@ defmodule Diffo.Provider.Assigner do
   end
 
   defp check_lifecycle(%{type: :resource, resource_state: state}) when state != :operating,
-    do: {:error, "cannot assign: resource lifecycle state is #{inspect(state)}, must be :operating"}
+    do:
+      {:error, "cannot assign: resource lifecycle state is #{inspect(state)}, must be :operating"}
 
   defp check_lifecycle(%{type: :service, service_state: state})
        when state not in [:active, :inactive],
-       do: {:error, "cannot assign: service state is #{inspect(state)}, must be :active or :inactive"}
+       do:
+         {:error,
+          "cannot assign: service state is #{inspect(state)}, must be :active or :inactive"}
 
   defp check_lifecycle(_), do: :ok
 
diff --git a/lib/diffo/provider/components/assignment_relationship.ex b/lib/diffo/provider/components/assignment_relationship.ex
index abbadb2..a6ed4e1 100644
--- a/lib/diffo/provider/components/assignment_relationship.ex
+++ b/lib/diffo/provider/components/assignment_relationship.ex
@@ -45,7 +45,9 @@ defmodule Diffo.Provider.AssignmentRelationship do
       }
 
       list_name =
-        Diffo.Provider.Relationship.derive_relationship_characteristic_list_name(record.target_type)
+        Diffo.Provider.Relationship.derive_relationship_characteristic_list_name(
+          record.target_type
+        )
 
       characteristics =
         [%{name: record.thing, value: record.value}]
@@ -61,8 +63,13 @@ defmodule Diffo.Provider.AssignmentRelationship do
       |> Diffo.Util.set(list_name, characteristics)
     end
 
-    order [:type, :resource, :service, :resourceRelationshipCharacteristic,
-           :serviceRelationshipCharacteristic]
+    order [
+      :type,
+      :resource,
+      :service,
+      :resourceRelationshipCharacteristic,
+      :serviceRelationshipCharacteristic
+    ]
   end
 
   actions do
diff --git a/lib/diffo/provider/components/instance/extension/characteristic.ex b/lib/diffo/provider/components/instance/extension/characteristic.ex
index 9b003df..5180eb6 100644
--- a/lib/diffo/provider/components/instance/extension/characteristic.ex
+++ b/lib/diffo/provider/components/instance/extension/characteristic.ex
@@ -35,7 +35,8 @@ defmodule Diffo.Provider.Instance.Characteristic do
   end
 
   defp create_characteristics_from_declarations(declarations, type) do
-    Enum.reduce_while(declarations, {:ok, []}, fn %{name: name, value_type: value_type}, {:ok, acc} ->
+    Enum.reduce_while(declarations, {:ok, []}, fn %{name: name, value_type: value_type},
+                                                  {:ok, acc} ->
       try do
         attrs =
           case value_type do
@@ -148,7 +149,8 @@ defmodule Diffo.Provider.Instance.Characteristic do
           end)
 
         characteristics =
-          Enum.reduce_while(characteristic_updates, {:ok, []}, fn {characteristic, value}, {:ok, acc} ->
+          Enum.reduce_while(characteristic_updates, {:ok, []}, fn {characteristic, value},
+                                                                  {:ok, acc} ->
             case Provider.update_characteristic(characteristic, %{value: value}) do
               {:ok, characteristic} ->
                 {:cont, {:ok, [characteristic | acc]}}
diff --git a/lib/diffo/provider/components/instance/extension/feature.ex b/lib/diffo/provider/components/instance/extension/feature.ex
index 4aa0da3..a67ca29 100644
--- a/lib/diffo/provider/components/instance/extension/feature.ex
+++ b/lib/diffo/provider/components/instance/extension/feature.ex
@@ -40,7 +40,8 @@ defmodule Diffo.Provider.Instance.Feature do
       {:ok, []},
       fn %{name: name, is_enabled?: isEnabled, characteristics: characteristics}, {:ok, acc} ->
         characteristic_ids =
-          Enum.reduce_while(characteristics, {:ok, []}, fn %{name: name, value_type: value_type}, {:ok, ids} ->
+          Enum.reduce_while(characteristics, {:ok, []}, fn %{name: name, value_type: value_type},
+                                                           {:ok, ids} ->
             try do
               attrs =
                 case value_type do
diff --git a/lib/diffo/provider/components/instance/extension/relationship.ex b/lib/diffo/provider/components/instance/extension/relationship.ex
index e637dd6..50c1264 100644
--- a/lib/diffo/provider/components/instance/extension/relationship.ex
+++ b/lib/diffo/provider/components/instance/extension/relationship.ex
@@ -27,12 +27,12 @@ defmodule Diffo.Provider.Instance.Relationship do
 
       _ ->
         Enum.reduce_while(relationships, :ok, fn %{
-                                                    id: id,
-                                                    alias: name,
-                                                    type: type,
-                                                    direction: direction
-                                                  },
-                                                  :ok ->
+                                                   id: id,
+                                                   alias: name,
+                                                   type: type,
+                                                   direction: direction
+                                                 },
+                                                 :ok ->
           attrs =
             case direction do
               :reverse -> %{source_id: id, party_id: result.id, alias: name, type: type}
diff --git a/lib/diffo/provider/components/instance/util.ex b/lib/diffo/provider/components/instance/util.ex
index b555255..0e20761 100644
--- a/lib/diffo/provider/components/instance/util.ex
+++ b/lib/diffo/provider/components/instance/util.ex
@@ -68,6 +68,7 @@ defmodule Diffo.Provider.Instance.Util do
           nil -> result
           state -> Diffo.Util.set(result, :lifecycleState, state)
         end
+
         # |> Diffo.Util.ensure_not_nil(:administrativeState, record.resource_administrative_state)
         # |> Diffo.Util.ensure_not_nil(:operationalState, record.resource_operational_state)
         # |> Diffo.Util.ensure_not_nil(:resourceStatus, record.resource_status)
diff --git a/lib/diffo/provider/extension.ex b/lib/diffo/provider/extension.ex
index aee67ad..3343df6 100644
--- a/lib/diffo/provider/extension.ex
+++ b/lib/diffo/provider/extension.ex
@@ -339,7 +339,13 @@ defmodule Diffo.Provider.Extension do
       end
       """
     ],
-    entities: [@party_entity, @parties_entity, @party_ref_entity, @party_role_entity, @inherited_party_entity]
+    entities: [
+      @party_entity,
+      @parties_entity,
+      @party_ref_entity,
+      @party_role_entity,
+      @inherited_party_entity
+    ]
   }
 
   # ── places ─────────────────────────────────────────────────────────────────
@@ -441,7 +447,13 @@ defmodule Diffo.Provider.Extension do
       end
       """
     ],
-    entities: [@place_entity, @places_entity, @place_ref_entity, @place_role_entity, @inherited_place_entity]
+    entities: [
+      @place_entity,
+      @places_entity,
+      @place_ref_entity,
+      @place_role_entity,
+      @inherited_place_entity
+    ]
   }
 
   # ── instances ──────────────────────────────────────────────────────────────
diff --git a/lib/diffo/provider/extension/transformers/transform_behaviour.ex b/lib/diffo/provider/extension/transformers/transform_behaviour.ex
index 3e41769..3ab8a5c 100644
--- a/lib/diffo/provider/extension/transformers/transform_behaviour.ex
+++ b/lib/diffo/provider/extension/transformers/transform_behaviour.ex
@@ -127,5 +127,4 @@ defmodule Diffo.Provider.Extension.Transformers.TransformBehaviour do
       end
     end)
   end
-
 end
diff --git a/lib/diffo/provider/extension/transformers/transform_inherited_refs.ex b/lib/diffo/provider/extension/transformers/transform_inherited_refs.ex
index 8ef4c32..f281927 100644
--- a/lib/diffo/provider/extension/transformers/transform_inherited_refs.ex
+++ b/lib/diffo/provider/extension/transformers/transform_inherited_refs.ex
@@ -33,7 +33,8 @@ defmodule Diffo.Provider.Extension.Transformers.TransformInheritedRefs do
     calc = %Ash.Resource.Calculation{
       name: decl.role,
       type: {:array, :map},
-      calculation: {Diffo.Provider.Calculations.InheritedPlace, [via: via, source_role: decl.source_role]},
+      calculation:
+        {Diffo.Provider.Calculations.InheritedPlace, [via: via, source_role: decl.source_role]},
       description: "Inherited place via assignment alias traversal",
       arguments: [],
       public?: true,
@@ -50,7 +51,8 @@ defmodule Diffo.Provider.Extension.Transformers.TransformInheritedRefs do
     calc = %Ash.Resource.Calculation{
       name: decl.role,
       type: {:array, :map},
-      calculation: {Diffo.Provider.Calculations.InheritedParty, [via: via, source_role: decl.source_role]},
+      calculation:
+        {Diffo.Provider.Calculations.InheritedParty, [via: via, source_role: decl.source_role]},
       description: "Inherited party via assignment alias traversal",
       arguments: [],
       public?: true,
diff --git a/lib/diffo/provider/validations/validate_relationship_permitted.ex b/lib/diffo/provider/validations/validate_relationship_permitted.ex
index 3e7b18f..8601c27 100644
--- a/lib/diffo/provider/validations/validate_relationship_permitted.ex
+++ b/lib/diffo/provider/validations/validate_relationship_permitted.ex
@@ -50,7 +50,11 @@ defmodule Diffo.Provider.Validations.ValidateRelationshipPermitted do
           end
 
         :error ->
-          [[field: :relationships, message: "could not resolve target resource for id #{inspect(target_id)}"]
+          [
+            [
+              field: :relationships,
+              message: "could not resolve target resource for id #{inspect(target_id)}"
+            ]
           ]
       end
     end)
@@ -99,7 +103,8 @@ defmodule Diffo.Provider.Validations.ValidateRelationshipPermitted do
     if role in roles do
       :ok
     else
-      {:error, "relationship role #{inspect(role)} is not permitted as #{direction} on this resource"}
+      {:error,
+       "relationship role #{inspect(role)} is not permitted as #{direction} on this resource"}
     end
   end
 end
diff --git a/test/provider/extension/inherited_refs_test.exs b/test/provider/extension/inherited_refs_test.exs
index d99ca41..1e40da1 100644
--- a/test/provider/extension/inherited_refs_test.exs
+++ b/test/provider/extension/inherited_refs_test.exs
@@ -44,7 +44,11 @@ defmodule Diffo.Provider.Extension.InheritedRefsTest do
 
       {:ok, _card} =
         Servo.assign_port(card, %{
-          assignment: %Assignment{assignee_id: service.id, operation: :auto_assign, alias: :primary}
+          assignment: %Assignment{
+            assignee_id: service.id,
+            operation: :auto_assign,
+            alias: :primary
+          }
         })
 
       service = Ash.load!(service, [:primary], domain: Servo)
@@ -105,12 +109,20 @@ defmodule Diffo.Provider.Extension.InheritedRefsTest do
 
       {:ok, _card_a} =
         Servo.assign_port(card_a, %{
-          assignment: %Assignment{assignee_id: service.id, operation: :auto_assign, alias: :primary}
+          assignment: %Assignment{
+            assignee_id: service.id,
+            operation: :auto_assign,
+            alias: :primary
+          }
         })
 
       {:ok, _card_b} =
         Servo.assign_port(card_b, %{
-          assignment: %Assignment{assignee_id: service.id, operation: :auto_assign, alias: :secondary}
+          assignment: %Assignment{
+            assignee_id: service.id,
+            operation: :auto_assign,
+            alias: :secondary
+          }
         })
 
       service = Ash.load!(service, [:primary], domain: Servo)
diff --git a/test/provider/extension/relationship_dsl_test.exs b/test/provider/extension/relationship_dsl_test.exs
index a3c4678..465181d 100644
--- a/test/provider/extension/relationship_dsl_test.exs
+++ b/test/provider/extension/relationship_dsl_test.exs
@@ -194,6 +194,5 @@ defmodule Diffo.Provider.Extension.RelationshipDslTest do
       assert {:error, error} = result
       assert Exception.message(error) =~ "not permitted as target"
     end
-
   end
 end