Fail closed on ambiguous simple links

docs/releases/0.2.0.md

@@ -30,7 +30,7 @@
 - **Match rules:** explicit-type create match-rule enforcement scoped to Level 2+.
 - **Datetime portability:** `settings.timezone` added; applies to `now()`/`today()` and naive comparisons.
 - **Expressions:** `reduce()` requires explicit `init`; list methods `value/index/acc` shadow frontmatter fields.
-- **Links:** `ambiguous_link` is an error on ID ambiguity, warning after tiebreakers.
+- **Links:** `ambiguous_link` fails closed for duplicate ID or filename matches; providers do not choose an arbitrary target.
  - **Non-scalar ordering:** `order_by` on lists/objects now specifies deterministic ordering rules.
 
 ## Removed / Deprecated

tests/level-4/links-non-markdown.yaml

@@ -349,10 +349,10 @@ groups:
               field: "assignee"
 
   # =============================================================================
-  # Group 6: Tiebreaker resolution order (§8.4)
+  # Group 6: Ambiguous simple-name resolution fails closed (§8.4)
   # =============================================================================
 
-  - name: "simple name link tiebreaker resolution"
+  - name: "ambiguous simple name link resolution"
     spec_ref: "§8.4"
 
     setup:
@@ -370,7 +370,7 @@ groups:
           ---
 
     tests:
-      - name: "tiebreaker prefers same directory"
+      - name: "same-directory duplicate does not create an implicit preference"
         setup:
           files:
             tasks/source.md: |
@@ -394,9 +394,9 @@ groups:
           path: "tasks/source.md"
           field: "ref"
         expect:
-          resolved_path: "tasks/readme.md"
+          resolved_path: null
 
-      - name: "tiebreaker prefers shortest path when no same-dir match"
+      - name: "shorter duplicate path does not create an implicit preference"
         setup:
           files:
             tasks/source.md: |
@@ -420,9 +420,9 @@ groups:
           path: "tasks/source.md"
           field: "ref"
         expect:
-          resolved_path: "docs/readme.md"
+          resolved_path: null
 
-      - name: "tiebreaker uses alphabetical as final fallback"
+      - name: "lexical order does not create an implicit preference"
         setup:
           files:
             root-source.md: |
@@ -446,7 +446,7 @@ groups:
           path: "root-source.md"
           field: "ref"
         expect:
-          resolved_path: "aaa/target.md"
+          resolved_path: null
 
   # =============================================================================
   # Group 7: Markdown link resolution — relative to containing file (§8.2.2)

tests/level-4/links-resolution.yaml

@@ -366,10 +366,10 @@ groups:
           resolved_path: "people/alice.md"
 
   # =============================================================================
-  # Group 6: Tiebreaker rules for simple name resolution
+  # Group 6: Ambiguous simple-name resolution fails closed
   # =============================================================================
 
-  - name: "simple name tiebreakers"
+  - name: "same-directory ambiguity"
     spec_ref: "§8.4"
 
     setup:
@@ -400,15 +400,15 @@ groups:
           ---
 
     tests:
-      - name: "tiebreaker prefers same directory"
+      - name: "same-directory duplicate remains ambiguous"
         operation: resolve_link
         input:
           path: "tasks/source.md"
           field: ref
         expect:
-          resolved_path: "tasks/target.md"
+          resolved_path: null
 
-  - name: "simple name tiebreaker - shortest path"
+  - name: "path-length ambiguity"
     spec_ref: "§8.4"
 
     setup:
@@ -439,15 +439,15 @@ groups:
           ---
 
     tests:
-      - name: "tiebreaker prefers shortest path when not in same directory"
+      - name: "shorter path does not win an ambiguous simple name"
         operation: resolve_link
         input:
           path: "source.md"
           field: ref
         expect:
-          resolved_path: "a/target.md"
+          resolved_path: null
 
-  - name: "simple name tiebreaker - alphabetical"
+  - name: "lexical-order ambiguity"
     spec_ref: "§8.4"
 
     setup:
@@ -478,13 +478,13 @@ groups:
           ---
 
     tests:
-      - name: "tiebreaker uses alphabetical order for equal-length paths"
+      - name: "lexical order does not win an ambiguous simple name"
         operation: resolve_link
         input:
           path: "source.md"
           field: ref
         expect:
-          resolved_path: "alpha/target.md"
+          resolved_path: null
 
   # =============================================================================
   # Group 7: Ambiguous link detection

v0.2/08-links.md

@@ -167,11 +167,15 @@ Given a link value and the path of the file containing it:
      - If exactly one match, resolve to it
      - If multiple matches, resolution MUST fail with `ambiguous_link`
    - **Filename match pass**: If no `id_field` match exists, search scoped **markdown files (records)** by filename
-   - If multiple filename candidates match, apply tiebreakers in order:
-     a. **Same directory**: Prefer a file in the same directory as the referring file
-     b. **Shortest path**: Prefer the file with the shortest path (closest to collection root)
-     c. **Alphabetical**: Sort candidate paths lexicographically and take the first
-   - If multiple candidates remain after all tiebreakers, resolve to `null` and emit an `ambiguous_link` warning
+     - If exactly one match exists, resolve to it
+     - If multiple matches exist, resolution MUST fail closed: resolve to `null` and emit `ambiguous_link`
+
+   Implementations MUST NOT choose among duplicate simple-name matches by
+   referring directory, path length, scan order, or lexical order. Those
+   choices are unstable across providers and can silently bind a relationship
+   to a different record after an unrelated move or import. Authors can make
+   the target unambiguous with a path, a unique `id_field`, or a narrower typed
+   target constraint.
 
    > **Note:** Non-markdown files are not records and are not candidates for simple name matching (per [§2.9](./02-collection-layout.md)). A wikilink `[[diagram]]` will not match `diagram.png` — only markdown files are searched by `id_field` and filename. Non-markdown files are only resolved when explicitly referenced by path (with extension or relative path).
 

v0.2/appendix-c-error-codes.md

@@ -63,7 +63,7 @@ This appendix defines standard error codes for validation issues and operation e
 | `invalid_link` | Link cannot be parsed | Malformed wikilink |
 | `link_not_found` | Link target doesn't exist | Target "[[missing]]" not found |
 | `link_wrong_type` | Target is wrong type | Expected person, found task |
-| `ambiguous_link` | Multiple candidates for a simple-name link (error on ID ambiguity, warning if still ambiguous after tiebreakers) | "[[note]]" matches notes/note.md and archive/note.md |
+| `ambiguous_link` | Multiple candidates exist at the first populated simple-name lookup priority; resolution fails closed | "[[note]]" matches notes/note.md and archive/note.md |
 
 ### Date/Time Errors