Fix proxy response causing false upload failures

StreamingResponse + forwarded content-length header was causing a
content-length mismatch (chunked vs explicit length), which made axios
reject the response even though doc-service had already saved the file.
Switch to Response, strip content-length/content-type from forwarded
response headers (FastAPI recalculates them correctly), and strip
accept-encoding from forwarded requests to prevent decompression
mismatches.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/routers/categories_proxy.py

@@ -8,7 +8,7 @@ import os
 
 import httpx
 from fastapi import APIRouter, Depends, HTTPException, Request
-from fastapi.responses import StreamingResponse
+from fastapi.responses import Response
 
 from app.deps import get_current_user
 from app.models.user import User
@@ -19,8 +19,7 @@ _client = httpx.AsyncClient(base_url=DOC_SERVICE_URL, timeout=30.0)
 
 router = APIRouter()
 
-_HOP_BY_HOP = frozenset(
-    [
+_HOP_BY_HOP = frozenset([
     "connection",
     "keep-alive",
     "proxy-authenticate",
@@ -30,8 +29,10 @@ _HOP_BY_HOP = frozenset(
     "transfer-encoding",
     "upgrade",
     "host",
-    ]
-)
+    "accept-encoding",
+])
+
+_STRIP_RESPONSE = frozenset([*_HOP_BY_HOP, "content-length", "content-type"])
 
 
 def _forward_headers(request: Request, user_id: str) -> dict:
@@ -50,7 +51,7 @@ async def proxy_categories(
     request: Request,
     current_user: User = Depends(get_current_user),
     path: str = "",
-) -> StreamingResponse:
+) -> Response:
     url = f"/categories/{path}" if path else "/categories"
     headers = _forward_headers(request, str(current_user.id))
     body = await request.body()
@@ -69,11 +70,11 @@ async def proxy_categories(
     resp_headers = {
         k: v
         for k, v in response.headers.items()
-        if k.lower() not in _HOP_BY_HOP
+        if k.lower() not in _STRIP_RESPONSE
     }
 
-    return StreamingResponse(
-        content=iter([response.content]),
+    return Response(
+        content=response.content,
         status_code=response.status_code,
         headers=resp_headers,
         media_type=response.headers.get("content-type"),

backend/app/routers/documents_proxy.py

@@ -3,26 +3,27 @@ Proxy all /api/documents/* requests to doc-service:8001/documents/*.
 
 Uses a module-level AsyncClient for connection pooling.
 Strips hop-by-hop headers that must not be forwarded.
-File downloads (/file endpoint) are streamed.
 """
 import os
 
 import httpx
 from fastapi import APIRouter, Depends, HTTPException, Request
-from fastapi.responses import StreamingResponse
+from fastapi.responses import Response
 
 from app.deps import get_current_user
 from app.models.user import User
 
 DOC_SERVICE_URL = os.environ.get("DOC_SERVICE_URL", "http://doc-service:8001")
 
-# Module-level client — reused across requests for connection pooling
 _client = httpx.AsyncClient(base_url=DOC_SERVICE_URL, timeout=120.0)
 
 router = APIRouter()
 
-_HOP_BY_HOP = frozenset(
-    [
+# Headers that must not be forwarded in either direction.
+# Also strip accept-encoding so doc-service never compresses responses —
+# httpx decompresses transparently but the content-encoding header would
+# then mismatch the already-decompressed body we forward to the browser.
+_HOP_BY_HOP = frozenset([
     "connection",
     "keep-alive",
     "proxy-authenticate",
@@ -32,8 +33,14 @@ _HOP_BY_HOP = frozenset(
     "transfer-encoding",
     "upgrade",
     "host",
-    ]
-)
+    "accept-encoding",
+])
+
+# Additional response headers we let FastAPI recalculate rather than forward.
+# content-length is set automatically from the response body size.
+# content-type is set via the media_type argument, so strip it from headers
+# to avoid duplicates.
+_STRIP_RESPONSE = frozenset([*_HOP_BY_HOP, "content-length", "content-type"])
 
 
 def _forward_headers(request: Request, user_id: str) -> dict:
@@ -52,11 +59,9 @@ async def proxy_documents(
     request: Request,
     current_user: User = Depends(get_current_user),
     path: str = "",
-) -> StreamingResponse:
+) -> Response:
     url = f"/documents/{path}" if path else "/documents"
     headers = _forward_headers(request, str(current_user.id))
-
-    # For multipart uploads, stream the body directly
     body = await request.body()
 
     try:
@@ -70,15 +75,14 @@ async def proxy_documents(
     except httpx.RequestError as exc:
         raise HTTPException(status_code=502, detail=f"doc-service unreachable: {exc}")
 
-    # Strip hop-by-hop from response headers
     resp_headers = {
         k: v
         for k, v in response.headers.items()
-        if k.lower() not in _HOP_BY_HOP
+        if k.lower() not in _STRIP_RESPONSE
     }
 
-    return StreamingResponse(
-        content=iter([response.content]),
+    return Response(
+        content=response.content,
         status_code=response.status_code,
         headers=resp_headers,
         media_type=response.headers.get("content-type"),