Bring Your Own Key using JWT Signing Keys fails - custom JWTs return "Invalid API key" despite correct parsing

# Bug report - [x] I confirm this is a bug with Supabase, not with my own application. - [x] I confirm I have searched the [Docs](https://docs.supabase.com), GitHub [Discussions](https://github.com/supabase/supabase/discussions), and [Discord](https://discord.supabase.com). ## Describe the bug JWT authentication fails when using the new "Bring Your Own Key" feature via JWT Signing Keys in Supabase Dashboard. Custom JWTs signed with keys generated by `supabase gen signing-key` return `postgrest.exceptions.APIError: {'message': 'JSON could not be generated', 'code': 401, 'hint': 'Refer to full message for details', 'details': 'b\'{"message":"Invalid API key","hint":"Double check your Supabase `anon` or `service_role` API key."}\''}`, even though: 1. The keys were generated using Supabase's official CLI 2. The JWT is correctly parsed by Supabase (visible in logs) 3. The user is identified (`auth_user` field populated in logs) 4. The same code works with the legacy/default JWT secret 5. I have disabled JWT-based API keys ## To Reproduce ```bash Step 1: Generate Keys Using Supabase CLI # Generate ES256 signing key pair as per Supabase documentation supabase gen signing-key --algorithm ES256 Step 2: Import Public Key to Supabase Dashboard 1. Go to Dashboard → Settings → JWT Keys → JWT Signing Keys 2. Add the public key generated by supabase gen signing-key 3. Algorithm: ES256 (as generated) 4. Key ID: Auto-assigned (e.g., [your-kid]) 5. Status shows: Active Step 3: Code That Should Work But Fails import jwt import json from jwcrypto import jwk from supabase import create_async_client # Using the private key generated by: supabase gen signing-key --algorithm ES256 PRIVATE_KEY_JSON = "your_private_key" # Parse the key generated by Supabase CLI private_key_data = json.loads(PRIVATE_KEY_JSON) private_key = jwk.JWK(**private_key_data) pem_key = private_key.export_to_pem(private_key=True, password=None) # C…