Fix multi-file uploads tripping the per-IP concurrency guard (#1346) (#1362)

* Stop multi-file uploads from tripping the per-IP concurrency guard

The /api/upload concurrency check summed its condition over `files`, but the
condition didn't reference the loop variable — so it collapsed to len(files)
whenever the IP had any recent upload. A single multi-file batch sent right
after another upload therefore counted itself as N concurrent uploads and hit
max_concurrent_uploads (3), returning 429. The browser swallows the 429 (no
`files` in the body) and sends the chat with no attachments, so the model
"doesn't even see" them (issue #1346).

Count genuine recent upload events instead, via a pure count_recent_uploads()
helper, independent of the current batch's file count. save_upload still
enforces the per-minute sliding-window rate limit per file, so throttling is
preserved.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Also reconcile the per-minute upload rate limit with the batch cap

Follow-up within #1346: even after the concurrency-guard fix, a 6+ file batch
still failed because save_upload() counts each file against upload_rate_limit
(was 5/min) while the composer allows MAX_FILES=10 per batch — the reporter saw
"5 attachments work, 6 fail". Raise the per-minute file cap to 60 so a single
full batch (and a few of them) isn't self-rejected; burst abuse stays bounded by
max_concurrent_uploads. Add a real 6-file regression + a config guard that the
cap exceeds the frontend MAX_FILES.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

routes/upload_routes.py

@@ -8,6 +8,7 @@ from typing import List
 import logging
 from core.middleware import require_admin
 from src.auth_helpers import get_current_user
+from src.upload_handler import count_recent_uploads
 
 logger = logging.getLogger(__name__)
 
@@ -25,14 +26,17 @@ def setup_upload_routes(upload_handler):
         client_ip = request.client.host if request.client else "unknown"
         out = []
 
-        # Limit concurrent uploads per IP
-        ip_upload_count = sum(
-            1 for f in files 
-            if client_ip in upload_handler.upload_rate_log and 
-            any(now > time.time() - 10 for now in upload_handler.upload_rate_log[client_ip][-len(files):])
+        # Limit concurrent uploads per IP. Count genuine recent upload events —
+        # NOT the number of files in this batch. The previous check summed over
+        # `files`, so a single multi-file request counted itself as N concurrent
+        # uploads and tripped the limit (issue #1346: "attach more than one file
+        # → the model doesn't even see them"). save_upload still enforces the
+        # per-minute sliding-window rate limit per file.
+        recent_uploads = count_recent_uploads(
+            upload_handler.upload_rate_log.get(client_ip, []), time.time()
         )
 
-        if ip_upload_count >= upload_handler.max_concurrent_uploads:
+        if recent_uploads >= upload_handler.max_concurrent_uploads:
             raise HTTPException(
                 status_code=429,
                 detail=f"Maximum concurrent uploads ({upload_handler.max_concurrent_uploads}) exceeded"

src/upload_handler.py

@@ -43,6 +43,18 @@ def is_valid_upload_id(upload_id: str) -> bool:
     return UPLOAD_ID_RE.fullmatch(upload_id or "") is not None
 
 
+def count_recent_uploads(timestamps, now: float, window: float = 10.0) -> int:
+    """Number of upload events in *timestamps* within the last *window* seconds.
+
+    Used by the per-IP concurrency guard. The count is of genuine prior upload
+    events — it must NOT scale with how many files are in the *current* request,
+    or a single multi-file batch would reject itself (issue #1346)."""
+    if not timestamps:
+        return 0
+    cutoff = now - window
+    return sum(1 for t in timestamps if t > cutoff)
+
+
 class UploadHandler:
     def __init__(self, base_dir: str, upload_dir: str):
         self.base_dir = base_dir
@@ -50,7 +62,13 @@ class UploadHandler:
         self.max_upload_size = 10 * 1024 * 1024  # 10MB
         self.max_concurrent_uploads = 3
         self.cleanup_days = 30
-        self.upload_rate_limit = 5  # Max 5 uploads per minute per IP
+        # Per-IP per-minute cap. save_upload() counts EACH file, and the chat
+        # composer lets a user attach up to MAX_FILES (10, static/js/fileHandler.js)
+        # in one batch — so this must comfortably exceed 10, or a single 6+ file
+        # attach is rejected mid-batch (issue #1346: "5 work, 6 fail"). Burst abuse
+        # is separately bounded by max_concurrent_uploads. Headroom for a few full
+        # batches per minute.
+        self.upload_rate_limit = 60  # max 60 file-uploads per minute per IP
         self.upload_rate_window = 60  # 60 seconds
         
         # Track upload rates

tests/test_upload_multifile.py

@@ -0,0 +1,165 @@
+"""Regression tests for issue #1346 — attaching more than one file at once made
+the model "not even see" the attachments.
+
+Root cause: the per-IP concurrency guard in routes/upload_routes.py summed its
+condition over `files`, and the condition didn't depend on the loop variable, so
+it collapsed to `len(files)` whenever the IP had any recent upload. A multi-file
+batch sent right after a single upload (the reporter's exact flow) therefore
+counted itself as N concurrent uploads and tripped `max_concurrent_uploads`,
+returning 429. The browser swallowed the 429 (no `files` in the body) and sent
+the chat message with no attachments.
+
+The fix counts genuine recent upload *events*, independent of the current
+batch's file count. save_upload still enforces the per-minute rate limit.
+"""
+import io
+import re
+import types
+from pathlib import Path
+
+import pytest
+from fastapi import APIRouter
+
+from src.upload_handler import count_recent_uploads, UploadHandler
+import routes.upload_routes as up
+
+_REPO = Path(__file__).resolve().parent.parent
+
+
+def test_count_recent_uploads_ignores_batch_size():
+    now = 1_000.0
+    # No prior uploads -> zero, regardless of how big the incoming batch is.
+    assert count_recent_uploads([], now) == 0
+    # Only events inside the window are counted.
+    assert count_recent_uploads([now - 1, now - 2, now - 3], now, window=10) == 3
+    assert count_recent_uploads([now - 1, now - 50], now, window=10) == 1
+    assert count_recent_uploads([now - 11], now, window=10) == 0
+
+
+def _fake_handler():
+    h = types.SimpleNamespace()
+    h.upload_rate_log = {}
+    h.max_concurrent_uploads = 3
+
+    def save_upload(u, client_ip, owner=None):
+        # Mimic the real handler: every saved file logs a timestamp.
+        h.upload_rate_log.setdefault(client_ip, []).append(_NOW)
+        name = getattr(u, "filename", "f")
+        return {
+            "id": "0" * 32 + "." + "txt",
+            "name": name,
+            "mime": "text/plain",
+            "size": 1,
+            "hash": "h",
+            "uploaded_at": "now",
+            "width": None,
+            "height": None,
+            "is_duplicate": False,
+        }
+
+    h.save_upload = save_upload
+    return h
+
+
+_NOW = 5_000.0
+
+
+def _endpoint(router):
+    for r in router.routes:
+        if getattr(r, "path", None) == "/api/upload" and "POST" in getattr(r, "methods", set()):
+            return r.endpoint
+    raise AssertionError("upload endpoint not found")
+
+
+def _request(ip="1.2.3.4", user="tester"):
+    return types.SimpleNamespace(
+        client=types.SimpleNamespace(host=ip),
+        state=types.SimpleNamespace(current_user=user),
+    )
+
+
+def _files(n):
+    return [types.SimpleNamespace(filename=f"f{i}.txt") for i in range(n)]
+
+
+@pytest.fixture(autouse=True)
+def _reset_router(monkeypatch):
+    # Module-level router accumulates routes across setup calls; reset it.
+    monkeypatch.setattr(up, "router", APIRouter(prefix="/api/upload", tags=["upload"]))
+    # Freeze time so the seeded "recent upload" is deterministic.
+    monkeypatch.setattr(up.time, "time", lambda: _NOW)
+
+
+async def test_multifile_after_a_recent_upload_is_not_rejected():
+    """The bug: one prior upload + a 3-file batch -> 429. Must now succeed."""
+    h = _fake_handler()
+    h.upload_rate_log["1.2.3.4"] = [_NOW - 1]  # step 1: a single file moments ago
+    up.setup_upload_routes(h)
+    endpoint = _endpoint(up.router)
+
+    result = await endpoint(_request(), _files(3))
+
+    assert [f["name"] for f in result["files"]] == ["f0.txt", "f1.txt", "f2.txt"]
+
+
+async def test_fresh_multifile_upload_succeeds():
+    h = _fake_handler()
+    up.setup_upload_routes(h)
+    endpoint = _endpoint(up.router)
+
+    result = await endpoint(_request(), _files(5))
+
+    assert len(result["files"]) == 5
+
+
+async def test_genuine_recent_volume_still_throttled():
+    """The guard is preserved: enough genuine recent uploads still 429s."""
+    from fastapi import HTTPException
+
+    h = _fake_handler()
+    h.upload_rate_log["1.2.3.4"] = [_NOW - 1, _NOW - 2, _NOW - 3]  # 3 recent events
+    up.setup_upload_routes(h)
+    endpoint = _endpoint(up.router)
+
+    with pytest.raises(HTTPException) as ei:
+        await endpoint(_request(), _files(1))
+    assert ei.value.status_code == 429
+
+
+# ── #1346 follow-up: the per-minute rate limit must not reject a single
+# full multi-file batch. The reporter found "5 attachments work, 6 fail":
+# save_upload() counts each file against upload_rate_limit, which was 5 while
+# the composer allows MAX_FILES=10. ──────────────────────────────────────────
+
+def _max_files_from_frontend() -> int:
+    src = (_REPO / "static/js/fileHandler.js").read_text(encoding="utf-8")
+    m = re.search(r"MAX_FILES\s*=\s*(\d+)", src)
+    assert m, "MAX_FILES not found in fileHandler.js"
+    return int(m.group(1))
+
+
+def test_rate_limit_accommodates_a_full_batch():
+    # The per-minute file cap must comfortably exceed the frontend batch cap,
+    # or a single legitimate multi-file attach trips it (issue #1346).
+    h = UploadHandler.__new__(UploadHandler)
+    UploadHandler.__init__(h, base_dir="/tmp", upload_dir="/tmp/_odysseus_test_uploads_cfg")
+    assert h.upload_rate_limit >= _max_files_from_frontend()
+
+
+def test_six_file_batch_is_not_rate_limited(tmp_path):
+    from fastapi import HTTPException
+
+    h = UploadHandler(base_dir=str(tmp_path), upload_dir=str(tmp_path / "uploads"))
+    saved = 0
+    for i in range(6):
+        u = types.SimpleNamespace(
+            file=io.BytesIO(f"file number {i} unique content".encode()),
+            filename=f"f{i}.txt",
+        )
+        try:
+            meta = h.save_upload(u, client_ip="9.9.9.9", owner="tester")
+        except HTTPException as e:
+            raise AssertionError(f"file {i} rejected with {e.status_code}: {e.detail}")
+        assert meta and meta.get("id")
+        saved += 1
+    assert saved == 6