Container App UI API Url Wiring

Container App UI-to-API URL Wiring

Pattern

When deploying a React SPA alongside a .NET API in the same Azure Container App with azd, use relative URLs for API calls to avoid hardcoding FQDNs.

Why This Matters

Azure Container Apps FQDNs are assigned AFTER azd provision completes. If the UI needs the API URL at build time (e.g., for Vite import.meta.env.VITE_API_URL), there is a timing problem:

• Preprovision hook runs BEFORE provisioning → CA FQDN unknown
• UI build happens inside dotnet publish → needs config at that time
• Postprovision hook runs AFTER provisioning → too late for build-time config

Solution: Same-Origin Relative URLs

If the UI is served FROM the same Container App as the API, use relative URLs.

Files Modified (This Project)

• scripts/preprovision.ps1 — Added VITE_API_URL= to SPA env file generation
• scripts/preprovision.sh — Added VITE_API_URL= to SPA env file generation
• src/aipolicyengine-ui/.env.production.local — Generated file (git-ignored)

Reference

• Symptom: User reported dashboard timing out on API calls, no inbound requests in container logs
• Root cause: UI had stale hardcoded API URL from previous CA deployment
• Fix: Switched to same-origin relative URLs, regenerated config, redeployed
• Validation: curl confirmed API reachable, UI now calls correct endpoint