Define selected creation in inference-only collections

12-operations.md

@@ -65,6 +65,31 @@ Static JSON Schema defaults MAY be used by editor and create interfaces.
 Validation-time mutation occurs when the create operation explicitly copies a
 default into the draft.
 
+### Selected types and membership representation
+
+A request-level type selector identifies the type the caller intends to create;
+it is not itself a persisted frontmatter declaration. Contract selection MUST
+resolve and validate its designated implementing type before writing.
+
+When explicit declaration keys are configured, implementations MUST persist a
+selected type using those keys, preserving existing valid memberships. They
+MUST NOT hard-code `type` or `types` when those keys are not configured. A field
+outside the configured declaration keys remains ordinary application data.
+
+When `settings.explicit_type_keys` is empty, implementations MUST NOT add a type
+declaration field and MUST NOT reject a create solely because the list is empty.
+The selected type guides schema, lifecycle, and path policy. Membership is
+inferred from persisted frontmatter and the final canonical path. The selected
+(or contract-designated) type MUST be included in the final inferred membership;
+otherwise the operation MUST fail without writing a record. All applicable
+types participate in validation, not only the requested type. Matching errors
+MUST NOT be silently treated as non-matches.
+
+The pre-lifecycle membership freeze and final membership check still apply.
+Read defaults and projections are not persisted evidence of membership. A
+successful create guarantees membership for the written record under the
+current collection rules, not permanent membership after later user edits.
+
 ## Update
 
 Update modifies an existing record.

CHANGELOG.md

@@ -2,6 +2,14 @@
 
 All notable changes to this specification and conformance suite are documented here.
 
+## Unreleased
+
+- Clarify that selected-type creation does not require explicit membership keys.
+  With inference-only configuration, final persisted fields and path must match
+  the selected type, and all applicable types remain subject to validation.
+- Add shared creation fixtures for inferred membership, ordinary `type` metadata,
+  auxiliary schemas, derived paths, and serialization-policy membership loss.
+
 ## 2026-07-28 (standard field references)
 
 ### Added

tests/level-5/references.yaml

@@ -55,13 +55,11 @@ groups:
         tasks/task-b.md: |
           ---
           type: task
-          id: "task-b"
           title: "Task B"
           ---
         tasks/task-c.md: |
           ---
           type: task
-          id: "task-c"
           title: "Task C"
           parent: "[[task-b]]"
           ---
@@ -202,7 +200,6 @@ groups:
         notes/target.md: |
           ---
           type: note
-          id: "target"
           title: "Target Note"
           ---
 
@@ -284,7 +281,6 @@ groups:
         notes/target-note.md: |
           ---
           type: note
-          id: "target-note"
           title: "Target Note"
           ---
           Some body content here.
@@ -554,10 +550,10 @@ groups:
               link: "[Detail](../archive/detail.md)"
 
   # =============================================================================
-  # Group 6: Ambiguous link handling during rename
+  # Group 6: Deterministic duplicate-filename handling during rename
   # =============================================================================
 
-  - name: "ambiguous link not updated during rename"
+  - name: "deterministically selected duplicate filename updated during rename"
     spec_ref: "§12.5"
 
     setup:
@@ -594,7 +590,7 @@ groups:
           ---
 
     tests:
-      - name: "ambiguous link emits warning and is not updated"
+      - name: "deterministically selected duplicate filename is updated"
         operation: rename
         input:
           from: "folder-a/shared-name.md"
@@ -603,17 +599,18 @@ groups:
         expect:
           from: "folder-a/shared-name.md"
           to: "folder-a/renamed.md"
-          warnings:
+          references_updated:
             - path: "notes/source.md"
-              message_contains: "ambiguous"
-        # The ambiguous link is left unchanged
+              field: "ref"
+        # Equal-depth duplicate filenames use lexical normalized path order,
+        # so the link identifies folder-a/shared-name.md before the rename.
         verify_after:
           operation: read
           input:
             path: "notes/source.md"
           expect:
             frontmatter:
-              ref: "[[shared-name]]"
+              ref: "[[renamed]]"
 
   # =============================================================================
   # Group 7: rename_ref_update_failed error code

tests/v0.3/core/optional-membership.yaml

@@ -0,0 +1,169 @@
+name: Selected create with inferred membership
+spec_version: "0.3.0"
+fixture_set: core_collection
+category: core_collection
+spec_ref: "v0.3/07, v0.3/12"
+groups:
+  - name: No explicit membership keys
+    setup:
+      config: |
+        spec_version: "0.3.0"
+        settings:
+          explicit_type_keys: []
+          default_validation: error
+      types:
+        task.md: |
+          ---
+          kind: mdbase.type
+          name: task
+          match:
+            where:
+              tags: {contains: task}
+          schema:
+            dialect: json-schema-2020-12
+            value:
+              type: object
+              required: [title]
+              properties:
+                title: {type: string}
+                type: {type: string}
+                tags: {type: array, items: {type: string}}
+          ---
+        review.md: |
+          ---
+          kind: mdbase.type
+          name: review
+          match:
+            fields_present: [reviewed]
+          schema:
+            dialect: json-schema-2020-12
+            value:
+              type: object
+              required: [reviewer]
+          ---
+    tests:
+      - name: selected create succeeds through tag matching without adding keys
+        operation: create
+        input:
+          path: tasks/new.md
+          type: task
+          frontmatter: {title: Buy milk, tags: [task]}
+        expect:
+          valid: true
+          types: [task]
+          frontmatter: {title: Buy milk, tags: [task]}
+          frontmatter_not_contains: [type, types, mdbase_type]
+      - name: domain type is preserved rather than replaced with selected name
+        operation: create
+        input:
+          path: tasks/paper.md
+          type: task
+          frontmatter: {title: Read paper, tags: [task], type: article-journal}
+        expect:
+          valid: true
+          types: [task]
+          frontmatter: {type: article-journal}
+          frontmatter_not_contains: [types, mdbase_type]
+      - name: selected type must match the persisted document
+        operation: create
+        input:
+          path: tasks/not-matching.md
+          type: task
+          frontmatter: {title: Missing tag}
+        expect:
+          valid: false
+      - name: all inferred types validate alongside selected type
+        operation: create
+        input:
+          path: tasks/review.md
+          type: task
+          frontmatter: {title: Review paper, tags: [task], reviewed: true}
+        expect:
+          valid: false
+      - name: compatible auxiliary membership is retained
+        operation: create
+        input:
+          path: tasks/review-valid.md
+          type: task
+          frontmatter: {title: Review paper, tags: [task], reviewed: true, reviewer: Alice}
+        expect:
+          valid: true
+          types: [review, task]
+          frontmatter_not_contains: [type, types, mdbase_type]
+  - name: Final path establishes membership
+    setup:
+      config: |
+        spec_version: "0.3.0"
+        settings:
+          explicit_type_keys: []
+          default_validation: error
+      types:
+        task.md: |
+          ---
+          kind: mdbase.type
+          name: task
+          match:
+            path_glob: "tasks/**/*.md"
+          schema:
+            dialect: json-schema-2020-12
+            value: {type: object, required: [title], properties: {title: {type: string}}}
+          collection:
+            path:
+              pattern: "tasks/{title}.md"
+          ---
+    tests:
+      - name: selected type can derive its matching path
+        operation: create
+        input:
+          type: task
+          frontmatter: {title: Milk}
+        expect:
+          valid: true
+          path: tasks/Milk.md
+          types: [task]
+          frontmatter_not_contains: [type, types, mdbase_type]
+      - name: supplied matching path succeeds
+        operation: create
+        input:
+          type: task
+          path: tasks/Milk.md
+          frontmatter: {title: Milk}
+        expect:
+          valid: true
+          types: [task]
+      - name: supplied nonmatching path cannot satisfy selection
+        operation: create
+        input:
+          type: task
+          path: other/Milk.md
+          frontmatter: {title: Milk}
+        expect:
+          valid: false
+  - name: Serialization policy cannot erase membership
+    setup:
+      config: |
+        spec_version: "0.3.0"
+        settings:
+          explicit_type_keys: []
+          write_empty_lists: false
+          default_validation: error
+      types:
+        task.md: |
+          ---
+          kind: mdbase.type
+          name: task
+          match:
+            fields_present: [markers]
+          schema:
+            dialect: json-schema-2020-12
+            value: {type: object}
+          ---
+    tests:
+      - name: omitted empty list cannot establish persisted membership
+        operation: create
+        input:
+          type: task
+          path: no.md
+          frontmatter: {markers: []}
+        expect:
+          valid: false

tests/v0.3/manifest.yaml

@@ -160,6 +160,7 @@ fixture_sets:
     coverage_targets: [core_read, collection_semantics, links, core_write]
     files:
       - core/core-collection.yaml
+      - core/optional-membership.yaml
   - id: data_contracts
     description: Data contracts, type implementations, projections, stable digests, and conflicts.
     coverage_targets: [core_read]