A walkthrough of a web app

While filming this app, the client met 10 defects. The most serious: Database setup on Postgres fails unless an optional direct-connection URL is set. Each is below: what went wrong, why, and how to avoid it in your own software.

What went wrong, and how to avoid it

1. Database setup on Postgres fails unless an optional direct-connection URL is set Why: run-prisma.mjs switches the schema to postgresql and un-comments directUrl = env("LMS_DATABASE_DIRECT_URL"), but configureLmsDatabaseEnv() in scripts/lms-db-env.mjs only filled that variable from POSTGRES_* / DATABASE_URL fallbacks, never from LMS_DATABASE_URL itself.Avoid it: How it was fixed: scripts/lms-db-env.mjs: when no direct URL is configured for postgresql, use LMS_DATABASE_URL as LMS_DATABASE_DIRECT_URL. tests/lms-db-env.test.ts: new test. Add a test for the failing action and the edge case behind it, so a regression is caught before users meet it.
2. Local gateway serves LMS pages without their styles and scripts Why: packages/lms-gateway/src/dev-runner.mjs sent every /_next/* request to the engine (through the ai-proxy), but lms-commerce is a separate Next.js app with its own chunk names.Avoid it: How it was fixed: packages/lms-gateway/src/asset-fallback.mjs (new): try the engine first and stream the first answer that is not 404, else lms-commerce; dev-runner.mjs uses it for GET/HEAD /_next/*. Add a test for the failing action and the edge case behind it, so a regression is caught before users meet it.
3. AI tutoring chat fails for every message when the platform AI key is set on the engine server Why: packages/lms-ai-proxy/src/app/api/chat/route.ts split the model id on "/", but the engine sends "provider:model", so every request was treated as OpenAI; and when no LMS-stored key matched it refused with 400 instead of passing the request to the engine, whose server key works (the generate routes aAvoid it: How it was fixed: packages/lms-ai-proxy/src/lib/model-provider.ts (new): read "provider:model" and "provider/model"; chat/route.ts uses it and only refuses when the user chose their own keys and has. Add a test for the failing action and the edge case behind it, so a regression is caught before users meet it.
4. Publish and exam pages of a classroom show 404 behind the single-origin gateway Why: dev-runner.mjs and caddy.Caddyfile sent every /classroom/* path to the engine, which only serves /classroom/[id]; the deeper pages belong to lms-commerce.Avoid it: How it was fixed: packages/lms-gateway/src/dev-runner.mjs and caddy.Caddyfile: route /classroom/[id]/[anything] to lms-commerce. Add a test for the failing action and the edge case behind it, so a regression is caught before users meet it.

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