The situation:
With `convex` 1.29.2 (and 1.29.3), `convex deploy` against a self-hosted backend fails with `Error: Unable to start push to http://the loopback address:3210` / `Error fetching POST http://the loopback address:3210/api/deploy2/evaluate_push 404 Not Found`. The identical command works with 1.29.1.
What actually fixes it (verified in the thread):
Update your self-hosted backend , Convex shipped a new backend release that resolves this; both reporters confirmed deploys succeed against the updated backend. The fix was backend-side, so updating the CLI alone (1.29.3) did not help. Immediate workaround: pin `convex` to 1.29.1. Source: https://github.com/get-convex/convex-js/issues/105