fix(backend): use discriminator for credential matching in run_block

When executing blocks via the chat interface (run_block tool), the credential
matching logic was not using the discriminator_mapping to determine the correct
provider based on the selected model value.

For example, when a user ran AITextGeneratorBlock with model='gpt-4o-mini':
- The code matched against ALL supported providers (ollama, openai, anthropic...)
- Ollama credentials were always first in the list (since they don't require API key)
- So the FAKE_API_KEY from Ollama was used instead of the actual OpenAI key

This fix:
- Passes input_data to _check_block_credentials
- Uses field_info.discriminate() to narrow to the correct provider
- Matches credentials only for the discriminated provider

Fixes credential mismatch errors like:
'Error code: 401 - invalid_api_key: FAKE_API_KEY'

autogpt_platform/backend/backend/api/features/chat/tools/run_block.py

@@ -73,15 +73,22 @@ class RunBlockTool(BaseTool):
         self,
         user_id: str,
         block: Any,
+        input_data: dict[str, Any] | None = None,
     ) -> tuple[dict[str, CredentialsMetaInput], list[CredentialsMetaInput]]:
         """
         Check if user has required credentials for a block.
 
+        Args:
+            user_id: User ID
+            block: Block to check credentials for
+            input_data: Input data for the block (used to determine provider via discriminator)
+
         Returns:
             tuple[matched_credentials, missing_credentials]
         """
         matched_credentials: dict[str, CredentialsMetaInput] = {}
         missing_credentials: list[CredentialsMetaInput] = []
+        input_data = input_data or {}
 
         # Get credential field info from block's input schema
         credentials_fields_info = block.input_schema.get_credentials_fields_info()
@@ -94,14 +101,27 @@ class RunBlockTool(BaseTool):
         available_creds = await creds_manager.store.get_all_creds(user_id)
 
         for field_name, field_info in credentials_fields_info.items():
-            # field_info.provider is a frozenset of acceptable providers
-            # field_info.supported_types is a frozenset of acceptable types
+            # Use discriminator to narrow down provider if available
+            # This ensures we match credentials for the correct provider based on
+            # the actual model/value selected (e.g., gpt-4o-mini -> openai)
+            effective_field_info = field_info
+            if field_info.discriminator and field_info.discriminator_mapping:
+                discriminator_value = input_data.get(field_info.discriminator)
+                if discriminator_value and discriminator_value in field_info.discriminator_mapping:
+                    effective_field_info = field_info.discriminate(discriminator_value)
+                    logger.debug(
+                        f"Discriminated provider for {field_name}: "
+                        f"{discriminator_value} -> {effective_field_info.provider}"
+                    )
+
+            # effective_field_info.provider is a frozenset of acceptable providers
+            # effective_field_info.supported_types is a frozenset of acceptable types
             matching_cred = next(
                 (
                     cred
                     for cred in available_creds
-                    if cred.provider in field_info.provider
-                    and cred.type in field_info.supported_types
+                    if cred.provider in effective_field_info.provider
+                    and cred.type in effective_field_info.supported_types
                 ),
                 None,
             )
@@ -115,8 +135,8 @@ class RunBlockTool(BaseTool):
                 )
             else:
                 # Create a placeholder for the missing credential
-                provider = next(iter(field_info.provider), "unknown")
-                cred_type = next(iter(field_info.supported_types), "api_key")
+                provider = next(iter(effective_field_info.provider), "unknown")
+                cred_type = next(iter(effective_field_info.supported_types), "api_key")
                 missing_credentials.append(
                     CredentialsMetaInput(
                         id=field_name,
@@ -184,10 +204,10 @@ class RunBlockTool(BaseTool):
 
         logger.info(f"Executing block {block.name} ({block_id}) for user {user_id}")
 
-        # Check credentials
+        # Check credentials (pass input_data to use discriminator for provider selection)
         creds_manager = IntegrationCredentialsManager()
         matched_credentials, missing_credentials = await self._check_block_credentials(
-            user_id, block
+            user_id, block, input_data
         )
 
         if missing_credentials: