diff --git a/.github/scripts/build_payload.py b/.github/scripts/build_payload.py
index 82c2064..81c860c 100644
--- a/.github/scripts/build_payload.py
+++ b/.github/scripts/build_payload.py
@@ -4,10 +4,10 @@
 plus the package README, resolves the download URL from the GitHub
 release's .zip asset, and writes two API content files:
 
-* ``payload-create.json`` for POST /extensions (includes the ``id`` the
+* ``payload-create.json`` for POST /extensions (includes the ``identifier`` the
   API requires on create),
 * ``payload-update.json`` for PUT /extensions/{id} (identical except the
-  ``id``, which that endpoint rejects as an unknown field).
+  ``identifier``, which that endpoint rejects as an unknown field).
 
 The new release entry is keyed by the plain version (``"0.8.9"``), not the
 git tag (``"branding-v0.8.9"``): the API sorts and compares releases
@@ -271,7 +271,7 @@ def main() -> None:
         content["homepage_url"] = meta["homepage_url"]
 
     create_content = dict(content)
-    create_content["id"] = ext_id
+    create_content["identifier"] = ext_id
 
     size = len(json.dumps(create_content, ensure_ascii=False, separators=(",", ":")).encode("utf-8"))
     if size > MAX_CONTENT_BYTES:
diff --git a/.github/scripts/test_build_payload.py b/.github/scripts/test_build_payload.py
index edad533..86d6117 100644
--- a/.github/scripts/test_build_payload.py
+++ b/.github/scripts/test_build_payload.py
@@ -47,15 +47,19 @@ def build(self, history=None):
 
     def test_preserves_manifest_metadata_and_compound_requirements(self):
         create, update = self.build()
+        self.assertEqual(create["identifier"], self.meta["id"])
+        self.assertNotIn("id", create)
+        self.assertNotIn("identifier", update)
         for field in self.meta:
-            self.assertEqual(create[field], self.meta[field])
+            if field != "id":
+                self.assertEqual(create[field], self.meta[field])
         self.assertNotIn("website", create)
         self.assertNotIn("homepage_url", create)
         self.assertNotIn("id", update)
         self.assertEqual(create["releases"][0]["requires"], self.meta["requires"])
         self.assertNotIn("min_fossbilling_version", create["releases"][0])
         self.assertEqual(create["readme"], "# Example\n")
-        self.assertEqual(create, {**update, "id": "example_module"})
+        self.assertEqual(create, {**update, "identifier": "example_module"})
 
     def test_optional_homepage_and_icon(self):
         self.meta["homepage_url"] = "https://example.com"
diff --git a/.github/scripts/test_publish_contract.py b/.github/scripts/test_publish_contract.py
index 1050688..1a79203 100644
--- a/.github/scripts/test_publish_contract.py
+++ b/.github/scripts/test_publish_contract.py
@@ -111,7 +111,7 @@ def test_build_uses_trusted_sibling_imports_despite_pythonpath(self):
             result = subprocess.run(['bash', '-e', '-c', workflow_run('Build extension payload')], cwd=release, env=env, capture_output=True, text=True)
             self.assertFalse((release / 'hostile-imported').exists(), 'Tagged module imported via PYTHONPATH')
             self.assertEqual(result.returncode, 0, result.stderr)
-            self.assertEqual(json.loads((release / 'payload-create.json').read_text())['id'], 'branding')
+            self.assertEqual(json.loads((release / 'payload-create.json').read_text())['identifier'], 'branding')
 
     def test_create_and_update_accept_the_merged_api_statuses(self):
         for exists, method, code in [(False, "POST", 201), (True, "PUT", 202)]:
diff --git a/README.md b/README.md
index f8e4076..579559f 100644
--- a/README.md
+++ b/README.md
@@ -58,3 +58,6 @@ The client authenticates with `client_credentials` and is bound to the
 extensions v2 README, "Machine publishing"). If a publish fails with 409,
 a revision is already pending review — a moderator resolves it in the
 review queue, then re-run the workflow.
+
+Directory creation sends the manifest’s public `id` as `identifier`. Developer
+publisher bindings use the UUID `id` returned by the developer profile API.