Diagnosing Costco Supplier Portal Connection Resets
Costco’s supplier portal is hosted on Salesforce’s Heroku cloud with Cloudflare as the CDN layer. The portal uses TLS 1.3 with ECH for all authenticated sessions. When suppliers access the portal from macOS Safari on corporate or ISP networks with SSL inspection, the ISP gateway resets the ECH-enabled ClientHello, preventing the TLS handshake from completing.
Heroku’s TLS configuration supports TLS 1.2 fallback, but Cloudflare’s edge policy only offers fallback when the client explicitly signals TLS 1.2 support. ISP gateways in certain regions strip this signal, causing Cloudflare to assume TLS 1.3-only support and reject the connection.
Browser Integrity Sync on Heroku-Clouflare Stack
Costco’s supplier portal uses browser integrity sync across Heroku’s application layer and Cloudflare’s CDN layer. When the TLS handshake is interrupted, the integrity sync fails at the Cloudflare layer, and Heroku’s backend interprets the failure as a potential security event, blocking the supplier’s access.
Fixing Costco Supplier Portal Connection Resets
Disabling SSL Inspection for Costco Domains
Configure your network proxy to bypass Costco domains. In macOS, navigate to System Settings → Network → Wi-Fi → Details → Proxy. Add *.costco.com, *.supplier.costco.com to the bypass list. This routes Costco traffic without SSL inspection, allowing ECH to function.
Using Firefox with TLS 1.2 Maximum
Download Firefox → navigate to about:config → security.tls.version.max → set to 3. Access Costco Supplier Portal in Firefox — TLS 1.2 does not require ECH, so the handshake completes through ISP gateways that block ECH.
Switching to Mobile Hotspot
Connect your Mac to a mobile hotspot and attempt to access Costco Supplier Portal. If the portal loads successfully over mobile data, the issue is your primary ISP’s infrastructure — the mobile carrier’s network supports ECH, while your primary ISP does not. Use the mobile hotspot for supplier portal access until your ISP upgrades their gateway infrastructure.
Call to Action
Use the webs.ninja network lab to verify connectivity to Costco’s supplier portal endpoints. The diagnostic identifies whether the reset is caused by your ISP’s gateway, a Cloudflare edge node failure, or Costco’s Heroku infrastructure, directing the fix to the correct layer.