diff --git a/src/specify_cli/bundler/commands_impl/catalog_config.py b/src/specify_cli/bundler/commands_impl/catalog_config.py
index f763a21c65..afd0357e66 100644
--- a/src/specify_cli/bundler/commands_impl/catalog_config.py
+++ b/src/specify_cli/bundler/commands_impl/catalog_config.py
@@ -198,9 +198,17 @@ def add_source(
         "priority": int(priority),
         "install_policy": install_policy.value,
     }
+    # Construct BEFORE writing. ``CatalogSource.from_dict`` already rejects an
+    # empty id, but it used to run after ``_write`` had persisted the entry, so
+    # a whitespace-only ``--id`` (or a url from which no id can be derived)
+    # reported "A catalog source is missing its 'id'" while leaving
+    # ``{"id": "", ...}`` behind in bundle-catalogs.yml. Every later command
+    # that loads the stack then failed with that same error, wedging the
+    # project's catalog config until the file was hand-edited.
+    source = CatalogSource.from_dict(entry, Scope.PROJECT)
     catalogs.append(entry)
     _write(project_root, catalogs)
-    return CatalogSource.from_dict(entry, Scope.PROJECT)
+    return source
 
 
 def remove_source(project_root: Path, id_or_url: str) -> str:
diff --git a/tests/unit/test_bundler_catalog_config.py b/tests/unit/test_bundler_catalog_config.py
index 46c333700a..0ff17e6370 100644
--- a/tests/unit/test_bundler_catalog_config.py
+++ b/tests/unit/test_bundler_catalog_config.py
@@ -89,6 +89,34 @@ def test_remove_source_accepts_relative_local_path(tmp_path: Path, monkeypatch):
         cc.remove_source(project, "sub/cat.json")
 
 
+def test_failed_add_does_not_persist_a_broken_entry(tmp_path: Path):
+    """A rejected `catalog add` must leave the config untouched.
+
+    `CatalogSource.from_dict` already rejects an empty id, but it ran *after*
+    `_write` had persisted the entry, so a whitespace-only `--id` reported
+    "A catalog source is missing its 'id'" while leaving `{"id": "", ...}`
+    behind — and every later command that loads the stack then failed with that
+    same error, wedging the project's catalog config.
+    """
+    from specify_cli.bundler.services.catalog_stack import load_source_stack
+
+    project = tmp_path / "proj"
+    (project / ".specify").mkdir(parents=True)
+
+    with pytest.raises(BundlerError, match="missing its 'id'"):
+        cc.add_source(
+            project,
+            "https://example.test/c.json",
+            source_id="   ",
+            policy="install-allowed",
+            priority=5,
+        )
+
+    assert cc._read(project) == []
+    # The stack must still load — this is what the stray entry used to break.
+    assert [source.id for source in load_source_stack(project)]
+
+
 def test_remove_by_id_does_not_also_delete_canonical_url_match(tmp_path: Path, monkeypatch):
     """`remove <id>` must remove only the exact-id source, not also a different
     source whose url happens to equal the id's canonicalized path. (_canonicalize_url