Heroku Postgres upgrade results in unexplained connection timeouts after dyno restart

Goal: Identify whether the platform should provide a proactive compatibility check or require explicit user confirmation before performing a major version upgrade of Heroku Postgres that could break existing client‑library connections.

Constraints: Heroku Postgres upgrades via `heroku pg:upgrade` change the server version while preserving data, but the platform does not automatically update the client libraries bundled with an app’s buildpack. If the client library is older than the new server protocol, connections may fail with SSL handshake errors or timeouts, and the failure is only observed after the upgrade completes.

Uncertainty: The operational guidance does not specify a threshold for triggering a warning or a mandatory `heroku pg:wait` step, leaving users to discover incompatibility post‑upgrade.

Questions: What version‑compatibility heuristics does Heroku evaluate before allowing a Postgres upgrade? Should Heroku emit a warning when the detected client library is older than the target server version? Is there a supported method for users to verify compatibility without initiating the upgrade?