fix(mcp): Normalize legacy ProviderName format and fix credential optionality

- Add model_validator on CredentialsMetaInput to auto-normalize old
  "ProviderName.MCP" format to "mcp" at the model level, eliminating
  the need for string parsing hacks in every consumer.

- Fix aggregate_credentials_inputs to check block schema defaults when
  determining if credentials are required, not just node metadata.
  MCP blocks with default={} are always optional regardless of metadata.

autogpt_platform/backend/backend/data/graph.py

@@ -578,8 +578,17 @@ class GraphModel(Graph, GraphMeta):
 
         for graph in [self] + self.sub_graphs:
             for node in graph.nodes:
-                # Track if this node requires credentials (credentials_optional=False means required)
-                node_required_map[node.id] = not node.credentials_optional
+                # A node's credentials are optional if either:
+                # 1. The node metadata says so (credentials_optional=True), or
+                # 2. All credential fields on the block have defaults (not required by schema)
+                block_required = node.block.input_schema.get_required_fields()
+                creds_required_by_schema = any(
+                    fname in block_required
+                    for fname in node.block.input_schema.get_credentials_fields()
+                )
+                node_required_map[node.id] = (
+                    not node.credentials_optional and creds_required_by_schema
+                )
 
                 for (
                     field_name,

autogpt_platform/backend/backend/data/model.py

@@ -29,6 +29,7 @@ from pydantic import (
     GetCoreSchemaHandler,
     SecretStr,
     field_serializer,
+    model_validator,
 )
 from pydantic_core import (
     CoreSchema,
@@ -499,6 +500,25 @@ class CredentialsMetaInput(BaseModel, Generic[CP, CT]):
     provider: CP
     type: CT
 
+    @model_validator(mode="before")
+    @classmethod
+    def _normalize_legacy_provider(cls, data: Any) -> Any:
+        """Fix ``ProviderName.X`` format from Python 3.13 ``str(Enum)`` bug.
+
+        Python 3.13 changed ``str(StrEnum)`` to return ``"ClassName.MEMBER"``
+        instead of the plain value.  Old stored credential references may have
+        ``provider: "ProviderName.MCP"`` instead of ``"mcp"``.
+        """
+        if isinstance(data, dict):
+            prov = data.get("provider", "")
+            if isinstance(prov, str) and prov.startswith("ProviderName."):
+                member = prov.removeprefix("ProviderName.")
+                try:
+                    data = {**data, "provider": ProviderName[member].value}
+                except KeyError:
+                    pass
+        return data
+
     @classmethod
     def allowed_providers(cls) -> tuple[ProviderName, ...] | None:
         return get_args(cls.model_fields["provider"].annotation)

autogpt_platform/backend/backend/executor/manager.py

@@ -275,6 +275,7 @@ async def execute_node(
             isinstance(field_value, dict) and not field_value.get("id")
         ):
             continue  # No credentials configured — block runs without
+
         credentials_meta = input_type(**field_value)
         credentials, lock = await creds_manager.acquire(user_id, credentials_meta.id)
         creds_locks.append(lock)