From e6378e844e7a8cd82473a23b714ac979361132a3 Mon Sep 17 00:00:00 2001
From: svlandeg <sofie.vanlandeghem@gmail.com>
Date: Fri, 13 Mar 2026 15:06:04 +0100
Subject: [PATCH] update body type to allow bytes and cast appropriately

---
 fastapi/dependencies/utils.py | 6 +++---
 fastapi/routing.py            | 4 +++-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/fastapi/dependencies/utils.py b/fastapi/dependencies/utils.py
index edaaee48cb..3b763ab42b 100644
--- a/fastapi/dependencies/utils.py
+++ b/fastapi/dependencies/utils.py
@@ -598,7 +598,7 @@ async def solve_dependencies(
     *,
     request: Request | WebSocket,
     dependant: Dependant,
-    body: dict[str, Any] | FormData | None = None,
+    body: dict[str, Any] | FormData | bytes | None = None,
     background_tasks: StarletteBackgroundTasks | None = None,
     response: Response | None = None,
     dependency_overrides_provider: Any | None = None,
@@ -950,7 +950,7 @@ async def _extract_form_body(
 
 async def request_body_to_args(
     body_fields: list[ModelField],
-    received_body: dict[str, Any] | FormData | None,
+    received_body: dict[str, Any] | FormData | bytes | None,
     embed_body_fields: bool,
 ) -> tuple[dict[str, Any], list[dict[str, Any]]]:
     values: dict[str, Any] = {}
@@ -981,7 +981,7 @@ async def request_body_to_args(
     for field in body_fields:
         loc = ("body", get_validation_alias(field))
         value: Any | None = None
-        if body_to_process is not None:
+        if body_to_process is not None and not isinstance(body_to_process, bytes):
             try:
                 value = body_to_process.get(get_validation_alias(field))
             # If the received body is a list, not a dict
diff --git a/fastapi/routing.py b/fastapi/routing.py
index e791f7bba9..36acb6b89d 100644
--- a/fastapi/routing.py
+++ b/fastapi/routing.py
@@ -26,6 +26,7 @@ from typing import (
     Annotated,
     Any,
     TypeVar,
+    cast,
 )
 
 import anyio
@@ -75,6 +76,7 @@ from starlette import routing
 from starlette._exception_handler import wrap_app_handling_exceptions
 from starlette._utils import is_async_callable
 from starlette.concurrency import iterate_in_threadpool, run_in_threadpool
+from starlette.datastructures import FormData
 from starlette.exceptions import HTTPException
 from starlette.requests import Request
 from starlette.responses import JSONResponse, Response, StreamingResponse
@@ -455,7 +457,7 @@ def get_request_handler(
         solved_result = await solve_dependencies(
             request=request,
             dependant=dependant,
-            body=body,  # ty: ignore[invalid-argument-type]
+            body=cast(dict[str, Any] | FormData | bytes | None, body),
             dependency_overrides_provider=dependency_overrides_provider,
             async_exit_stack=async_exit_stack,
             embed_body_fields=embed_body_fields,