bug: backend down on Render after vision.py additions — imagehash/Pillow import crash on startup

[ankitrmishra01]

Bug report

Live app: https://green-lens-tau.vercel.app/
Backend: https://greenlens-backend-n3ws.onrender.com
Reported after: commits by cypher redye adding vision.py + imagehash features

Errors observed (browser console)

• greenlens-backend-n3ws.onrender.com/api/auth/register → 401
• greenlens-backend-n3ws.onrender.com/api/auth/register → 422
• greenlens-backend-n3ws.onrender.com/api/organizations → 400

What's actually happening

All endpoints return "Host not in allowlist" / 403 from Render's proxy.
This is NOT a CORS issue and NOT an auth issue. It means the FastAPI app
never starts — Render's router has nothing to forward requests to, so it
serves this error itself.

Verified by hitting the root endpoint directly:
curl https://greenlens-backend-n3ws.onrender.com/
→ "Host not in allowlist" (Render proxy error, not FastAPI)

---

Root cause

Cypher Redye's recent commits added vision.py and the following new imports to main.py:

import imagehash
from vision import scan_receipt_or_food, get_image_hash

vision.py also imports:
from PIL import Image
import imagehash

These two packages (Pillow, ImageHash) were added to requirements.txt but
Render only installs dependencies on a fresh build/deploy. If the deploy
did not complete successfully, the running container is missing these packages
and the app crashes at import time before it can bind to a port.

Expected crash log on Render:
ModuleNotFoundError: No module named 'imagehash'
or
ModuleNotFoundError: No module named 'PIL'

This causes a startup crash → Render returns 403 for all requests → every
API call from the frontend fails, including register and login.

---

Steps to verify

1. Go to Render Dashboard → greenlens-backend service → Logs
2. Look for ModuleNotFoundError near the top of the most recent deploy log
3. Confirm the app never reaches "Application startup complete"

---

Fix

Step 1 — Trigger a manual redeploy on Render

Render Dashboard → greenlens-backend → Manual Deploy → Deploy latest commit

This forces a fresh pip install -r requirements.txt which will install
Pillow and ImageHash correctly.

Step 2 — Confirm requirements.txt has both packages

Already present in the file:
Pillow>=10.0.0
ImageHash>=4.3.1

No code changes needed — a clean redeploy should be enough.

Step 3 — Verify after deploy

curl https://greenlens-backend-n3ws.onrender.com/

Expected response after fix:
{
"message": "GreenLens API v2.0.0 — Track Your Carbon. Change Your Campus.",
"status": "healthy",
"cors_patched": true
}

---

Why previous diagnosis was wrong

Earlier analysis pointed to VITE_API_URL being blank and the Axios
interceptor attaching stale tokens. While those are real minor issues,
they are NOT the cause of registration being broken. The backend is
completely unreachable — no request ever reaches FastAPI code at all.

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Labels

bug, backend, render, deployment, vision