make sure running prod backend only uses backend port

[adhami3310]

previously it would try frontend port, introduced in the single port PR

[greptile-apps]

Greptile Summary

This PR fixes a regression introduced by a "single port" change where running a production backend-only server would incorrectly select from frontend port values (including falling back to DefaultPorts.FRONTEND_PORT) instead of backend port values. The fix splits the port-selection logic in _run for the prod path into three branches based on running_mode, ensuring each mode uses the correct port config and fallback default.

Confidence Score: 5/5

Safe to merge — targeted one-function fix with no new dependencies or logic regressions.

The change is narrow, directly addresses the stated bug (BACKEND_ONLY prod mode using frontend port/fallback), and preserves existing FULLSTACK behavior. No new test surface area is introduced, all branches are simple assignments.

No files require special attention.

Important Files Changed

Filename	Overview
reflex/reflex.py	Port-selection logic in the prod branch of _run is split by running_mode so each mode reads the correct port config and falls back to the correct default port.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["_run() — prod path"] --> B{running_mode?}
    B -->|BACKEND_ONLY| C["requested_port = backend_port or config.backend_port\nfallback_port = DefaultPorts.BACKEND_PORT"]
    B -->|FRONTEND_ONLY| D["requested_port = frontend_port or config.frontend_port\nfallback_port = DefaultPorts.FRONTEND_PORT"]
    B -->|FULLSTACK| E["requested_port = frontend_port or backend_port\n  or config.frontend_port or config.backend_port\nfallback_port = DefaultPorts.FRONTEND_PORT"]
    C --> F["handle_port(port = requested_port or fallback_port,\nauto_increment = requested_port is None)"]
    D --> F
    E --> F
    F --> G["_run_prod(running_mode, port, backend_host)"]

Loading

_{Reviews (1): Last reviewed commit: "make sure running prod backend only uses..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 9 untouched benchmarks

---

_{Comparing make-sure-running-prod-backend-only-uses-backend-port (f9d2199) with main (b977e62)}