diff --git a/gitnexus/test/helpers/r-rename-verdict.ts b/gitnexus/test/helpers/r-rename-verdict.ts
index 2a39debc9..4d6d52507 100644
--- a/gitnexus/test/helpers/r-rename-verdict.ts
+++ b/gitnexus/test/helpers/r-rename-verdict.ts
@@ -1,7 +1,8 @@
 /**
  * Run the R rename provider's safety check on real parsed sources and a real knowledge graph.
  * `localDefs` are read off the sources the way the indexer would list plain top-level functions
- * (`name <- function`), so a function defined in another file is visible to the checks.
+ * (`name <- function`, `name <<- function` and `name = function`), so a function defined in
+ * another file is visible to the checks.
  */
 import Parser from 'tree-sitter';
 import R from '@eagleoutice/tree-sitter-r';
@@ -21,7 +22,7 @@ export interface RVerdictInput {
   readonly targetFile?: string;
 }
 
-const FUNCTION_DEF = /^(`[^`\n]+`|[A-Za-z.][A-Za-z0-9._]*)\s*<-\s*function/gm;
+const FUNCTION_DEF = /^(`[^`\n]+`|[A-Za-z.][A-Za-z0-9._]*)\s*(?:<-|<<-|=(?!=))\s*function/gm;
 
 /** The issue the provider reports (`code`, `message`), or null when it accepts the rename. */
 export function rIssue(input: RVerdictInput): { code: string; message: string } | null {
diff --git a/gitnexus/test/unit/r-rename-collisions.test.ts b/gitnexus/test/unit/r-rename-collisions.test.ts
index 068deeb2c..85ca81109 100644
--- a/gitnexus/test/unit/r-rename-collisions.test.ts
+++ b/gitnexus/test/unit/r-rename-collisions.test.ts
@@ -48,6 +48,28 @@ describe('R rename: a new name that already exists', () => {
     ).toBe('name_collision');
   });
 
+  it.each(['<-', '<<-', '='])(
+    'lists a function defined with %s, so another file defining the new name is refused',
+    (op) => {
+      expect(
+        rIssue({
+          files: { 'a.R': HELPER, 'b.R': `assist ${op} function(v) v * 2\n` },
+          newName: 'assist',
+        })?.code,
+      ).toBe('name_collision');
+    },
+  );
+
+  it('sees a generic defined with = when it guards against a new S3 method name', () => {
+    // `to_json = function(x) x` makes `to_json.foo` an S3 method of an indexed function.
+    expect(
+      rIssue({
+        files: { 'a.R': HELPER, 'b.R': 'to_json = function(x) x\n' },
+        newName: 'to_json.foo',
+      })?.code,
+    ).toBe('unsupported_occurrence');
+  });
+
   it('refuses a <<- to the new name from inside a function', () => {
     expect(verdict('install <- function() { assist <<- 3 }\n')).toBe('name_collision');
     expect(verdict('install <- function() { 3 ->> assist }\n')).toBe('name_collision');