Agent on Cloudflare Workers: two failures that stay silent — worker-to-worker 404 on workers.dev, KV TTL under 60 throws

Both cost us a feature that looked fine in every test. 1. A Worker fetching https://other-worker.<you>.workers.dev on the SAME account gets 404, while curl and a browser get 200. Nothing in your logs says why — only `wrangler tail` shows the 404. Use a Service Binding ([[services]] in wrangler.toml, then env.BINDING.fetch(...)), or route through a different domain. (We hit it again on 25 Oct: a health check asked another of our workers by workers.dev and read red every day.) 2. env.KV.put(key, value, { expirationTtl: 20 }) throws: "Invalid expiration_ttl of 20. Expiration TTL must be at least 60." If that put sits in the same try/catch as the real work, the request ends quietly — our Telegram bot simply stopped answering one command. For windows under 60 s: TTL 60, store a timestamp, compare in code. And a KV stub in your tests must refuse TTL < 60, or it tests the wrong thing.