ENG-8961: Single port is only prod option

[adhami3310]

No description provided.

[codspeed-hq]

Merging this PR will not alter performance

✅ 9 untouched benchmarks

---

_{Comparing single-port-is-only-prod-option (12da11b) with main (08ee62a)}

[greptile-apps]

Greptile Summary

This PR enforces single-port as the only production option, removing the ability to run the frontend and backend on separate ports in --env prod. The backend now mounts compiled frontend static files directly (via REFLEX_MOUNT_FRONTEND_COMPILED_APP) so both are served from one port, and run_granian_backend_prod switches from a subprocess to the direct Granian Python API.

• The --single-port CLI flag is kept for backward compatibility but no longer changes behavior — production now always uses a single port regardless of whether the flag is passed.

Confidence Score: 5/5

This PR is safe to merge — the prod single-port enforcement is logically consistent and all previously flagged P1 issues have been resolved.

All prior P0/P1 findings (always-truthy enum guard, loglevel silently dropped in Granian prod, ProcessPoolExecutor leak) are resolved in the current code. The only remaining finding is a P2 UX note that --single-port is now a no-op and could benefit from a deprecation warning. No correctness or reliability issues remain.

reflex/reflex.py — the --single-port flag validation block is now redundant and could mislead users or deploy scripts that relied on the flag to opt into single-port mode.

Vulnerabilities

No security concerns identified. The static file serving via Starlette StaticFiles is standard, and the Granian direct-API switch does not introduce new attack surface.

Important Files Changed

Filename	Overview
reflex/reflex.py	Adds --single-port flag (now redundant with prod always using single port) and updates _run/_run_prod to enforce single-port in production; guard logic and enum comparisons are correct.
reflex/utils/exec.py	Adds run_frontend_prod and _frontend_prod_app for frontend-only prod serving; run_granian_backend_prod switches to direct Granian API and correctly passes loglevel.value as the env-var default.
scripts/integration.sh	Prod mode now only waits for one port (3000) instead of two (3000 and 8000), consistent with single-port production.
reflex/app.py	Mounts compiled frontend static files in the backend ASGI app when REFLEX_MOUNT_FRONTEND_COMPILED_APP is set, enabling single-port fullstack prod serving.
tests/units/test_prerequisites.py	Adds test for PackageJson.Commands.get_prod_command with various frontend_path values; looks correct.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[reflex run] --> B{env?}
    B -- dev --> C[_run_dev]
    B -- prod --> D{ports conflict?}
    D -- yes --> E[SystemExit: must use same port]
    D -- no --> F[resolve single port]
    F --> G[_run_prod]
    G --> H[config: frontend_port = backend_port = port]
    H --> I{running_mode?}
    I -- has_backend --> J[run_backend_prod\nmount_frontend_compiled_app=has_frontend]
    I -- frontend only --> K[run_frontend_prod]
    J --> L{granian?}
    L -- yes --> M[run_granian_backend_prod\nGranian direct API]
    L -- no --> N[run_uvicorn_backend_prod]
    K --> L
    C --> O[run_frontend dev port]
    C --> P[run_backend dev port]

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_{Reviews (3): Last reviewed commit: "fix autosetters" | Re-trigger Greptile}

[linear]

ENG-8961 Make --single-port default and only mode for env prod

[masenf]

@greptile-apps re-review this PR

[masenf]

@greptile-apps re-review this PR

[masenf]

ship it, with optional/follow-on feedback