fix(api): accept resolved file types in custom bucket on history replay

A Chatflow file uploaded into the CUSTOM type slot is coerced to its
detected type by _resolve_file_type (PNG -> IMAGE), and MessageFile.type
persists that resolved type. On history replay, build_from_message_file
rebuilds mapping["type"] from MessageFile.type, so a file that passed
round 1 (mapping["type"]=="custom") was rejected on round 2
(mapping["type"]=="image") even though the workflow config was unchanged.

- Refactor is_file_valid_with_config with bucket semantics: CUSTOM acts
  as a fallback bucket gated by allowed_file_extensions, compared case-
  and dot-insensitively. This also fixes a parallel mismatch where a
  user whitelist of [".PNG", "png", "JPG", ...] failed to match the
  upload-side ".png" (always lowercase with leading dot).
- Skip re-validation when rehydrating files from conversation history in
  TokenBufferMemory and BaseAgentRunner; history files were validated at
  upload time, mirroring build_file_from_stored_mapping.

api/core/agent/base_agent_runner.py

@@ -529,10 +529,11 @@ class BaseAgentRunner(AppRunner):
         image_detail_config = file_extra_config.image_config.detail if file_extra_config.image_config else None
         image_detail_config = image_detail_config or ImagePromptMessageContent.DETAIL.LOW
 
+        # History files were validated on upload; replaying does not re-validate.
         file_objs = file_factory.build_from_message_files(
             message_files=files,
             tenant_id=self.tenant_id,
-            config=file_extra_config,
+            config=None,
             access_controller=_file_access_controller,
         )
         if not file_objs:

api/core/memory/token_buffer_memory.py

@@ -86,12 +86,13 @@ class TokenBufferMemory:
 
         detail = ImagePromptMessageContent.DETAIL.HIGH
         if file_extra_config and app_record:
-            # Build files directly without filtering by belongs_to
+            # History files were validated on upload; replaying does not re-validate.
+            # See models/utils/file_input_compat.py for the same pattern.
             file_objs = [
                 file_factory.build_from_message_file(
                     message_file=message_file,
                     tenant_id=app_record.tenant_id,
-                    config=file_extra_config,
+                    config=None,
                     access_controller=_file_access_controller,
                 )
                 for message_file in message_files

api/factories/file_factory/validation.py

@@ -2,9 +2,22 @@
 
 from __future__ import annotations
 
+from collections.abc import Iterable
+
 from graphon.file import FileTransferMethod, FileType, FileUploadConfig
 
 
+def _normalize_extension(extension: str) -> str:
+    if not extension:
+        return ""
+    s = extension.strip().lower()
+    return s if s.startswith(".") else "." + s
+
+
+def _extension_matches(extension: str, whitelist: Iterable[str]) -> bool:
+    return _normalize_extension(extension) in {_normalize_extension(e) for e in whitelist}
+
+
 def is_file_valid_with_config(
     *,
     input_file_type: str,
@@ -12,22 +25,27 @@ def is_file_valid_with_config(
     file_transfer_method: FileTransferMethod,
     config: FileUploadConfig,
 ) -> bool:
-    # FIXME(QIN2DIM): Always allow tool files (files generated by the assistant/model)
-    # These are internally generated and should bypass user upload restrictions
+    """Return whether the file is allowed by the upload config.
+
+    ``allowed_file_types`` lists the buckets a file may fall into; ``CUSTOM`` is
+    a fallback bucket gated by ``allowed_file_extensions`` (case- and
+    dot-insensitive). Tool-generated files bypass user-facing config.
+    """
     if file_transfer_method == FileTransferMethod.TOOL_FILE:
         return True
 
-    if (
-        config.allowed_file_types
-        and input_file_type not in config.allowed_file_types
-        and input_file_type != FileType.CUSTOM
-    ):
+    allowed_types = config.allowed_file_types or []
+    custom_allowed = FileType.CUSTOM in allowed_types
+    type_allowed = not allowed_types or input_file_type in allowed_types
+
+    if not type_allowed and not custom_allowed:
         return False
 
+    in_custom_bucket = input_file_type == FileType.CUSTOM or not type_allowed
     if (
-        input_file_type == FileType.CUSTOM
-        and config.allowed_file_extensions is not None
-        and file_extension not in config.allowed_file_extensions
+        in_custom_bucket
+        and config.allowed_file_extensions
+        and not _extension_matches(file_extension, config.allowed_file_extensions)
     ):
         return False
 

api/tests/unit_tests/factories/test_file_validation.py

@@ -0,0 +1,118 @@
+"""Unit tests for is_file_valid_with_config."""
+
+from __future__ import annotations
+
+import pytest
+
+from factories.file_factory.validation import is_file_valid_with_config
+from graphon.file import FileTransferMethod, FileType, FileUploadConfig
+
+
+def _validate(
+    *,
+    input_file_type: str,
+    file_extension: str = ".png",
+    file_transfer_method: FileTransferMethod = FileTransferMethod.LOCAL_FILE,
+    config: FileUploadConfig,
+) -> bool:
+    return is_file_valid_with_config(
+        input_file_type=input_file_type,
+        file_extension=file_extension,
+        file_transfer_method=file_transfer_method,
+        config=config,
+    )
+
+
+@pytest.mark.parametrize(
+    ("input_file_type", "file_extension", "allowed_file_types", "allowed_file_extensions", "expected"),
+    [
+        # round-1 happy path: literal "custom" mapping, ext whitelisted
+        ("custom", ".png", [FileType.CUSTOM], [".png"], True),
+        # round-2 replay: MessageFile.type is the resolved type, but config still allows CUSTOM
+        ("image", ".png", [FileType.CUSTOM], [".png"], True),
+        ("document", ".pdf", [FileType.CUSTOM], [".pdf"], True),
+        # mixed bucket [IMAGE, CUSTOM]: document falls into CUSTOM bucket via extension
+        ("document", ".pdf", [FileType.IMAGE, FileType.CUSTOM], [".pdf"], True),
+        ("document", ".exe", [FileType.IMAGE, FileType.CUSTOM], [".pdf"], False),
+        ("image", ".jpg", [FileType.IMAGE], [], True),
+        ("video", ".mp4", [FileType.IMAGE, FileType.DOCUMENT], [], False),
+        ("custom", ".exe", [FileType.CUSTOM], [".png"], False),
+        # empty allowed_file_types == no type restriction
+        ("video", ".mp4", [], [], True),
+    ],
+)
+def test_bucket_semantics(
+    input_file_type, file_extension, allowed_file_types, allowed_file_extensions, expected
+):
+    config = FileUploadConfig(
+        allowed_file_types=allowed_file_types,
+        allowed_file_extensions=allowed_file_extensions,
+    )
+    assert _validate(
+        input_file_type=input_file_type, file_extension=file_extension, config=config
+    ) is expected
+
+
+@pytest.mark.parametrize("whitelist_entry", [".png", ".PNG", "png", "PNG", " .Png ", "PnG"])
+def test_extension_match_is_case_and_dot_insensitive(whitelist_entry):
+    config = FileUploadConfig(
+        allowed_file_types=[FileType.CUSTOM],
+        allowed_file_extensions=[whitelist_entry],
+    )
+    assert _validate(input_file_type="custom", file_extension=".png", config=config) is True
+
+
+def test_extension_mismatch_still_rejected_after_normalization():
+    config = FileUploadConfig(
+        allowed_file_types=[FileType.CUSTOM],
+        allowed_file_extensions=[".png", ".jpg"],
+    )
+    assert _validate(input_file_type="custom", file_extension=".pdf", config=config) is False
+
+
+def test_mixed_case_whitelist_replicating_real_user_config():
+    config = FileUploadConfig(
+        allowed_file_types=[FileType.CUSTOM],
+        allowed_file_extensions=[".PNG", "png", "JPG", ".WEBP", "SVG", "GIF"],
+    )
+    for ext in (".png", ".jpg", ".webp", ".svg", ".gif"):
+        assert _validate(input_file_type="custom", file_extension=ext, config=config) is True
+
+
+def test_tool_file_always_passes():
+    config = FileUploadConfig(allowed_file_types=[FileType.CUSTOM], allowed_file_extensions=[".pdf"])
+    assert _validate(
+        input_file_type="image",
+        file_extension=".png",
+        file_transfer_method=FileTransferMethod.TOOL_FILE,
+        config=config,
+    ) is True
+
+
+def test_transfer_method_gate_for_non_image():
+    config = FileUploadConfig(
+        allowed_file_types=[FileType.DOCUMENT],
+        allowed_file_upload_methods=[FileTransferMethod.LOCAL_FILE],
+    )
+    assert _validate(
+        input_file_type="document",
+        file_extension=".pdf",
+        file_transfer_method=FileTransferMethod.LOCAL_FILE,
+        config=config,
+    ) is True
+    assert _validate(
+        input_file_type="document",
+        file_extension=".pdf",
+        file_transfer_method=FileTransferMethod.REMOTE_URL,
+        config=config,
+    ) is False
+
+
+def test_history_replay_matches_round_1_outcome_under_unchanged_config():
+    """A file that passes round 1 must pass history replay when config is unchanged."""
+    config = FileUploadConfig(
+        allowed_file_types=[FileType.CUSTOM],
+        allowed_file_extensions=[".png"],
+    )
+    assert _validate(input_file_type="custom", file_extension=".png", config=config) is True
+    assert _validate(input_file_type="image", file_extension=".png", config=config) is True