Replit `.replit` run command execution after legacy runtime transition

Migrated Replit .replit run command behavior after legacy runtime transition

Likely explanation

The core engine treats a run block as the entry point for container startup. If the file contains a run section, the engine executes that command and injects any variables defined inside that block. Top‑level env entries outside a run block are ignored for the purpose of the container’s environment, so they do not affect the startup command.

Confirmed facts

• The current core engine still parses top‑level env keys, but they are only applied when the repl’s run command is invoked.
• A missing or malformed run section causes the engine to fall back to the default startup command, effectively resetting the environment and any custom behavior.
• Environment variables placed outside the run block are not injected into the container, leading to different startup conditions after migration.

Steps to verify behavior

1. Open the .replit file and confirm that a run section exists.
2. Ensure all env declarations are nested inside that run block, e.g.
   

   run:
     env:
       MY_VAR: value

3. Run the repl and inspect the container logs or execute printenv to verify that the expected variables are present.
4. Compare the startup logs before and after migration for the same .replit content to ensure identical behavior.

Missing diagnostic

Is there a run section defined in the .replit file? This determines whether the custom command is executed or the repl falls back to the default startup.