fix: bind uvicorn to Railway's dynamic $PORT (prod deploy healthcheck failure)

[DevanshuNEU]

Problem

Production backend (api.opencodeintel.com) was returning 502 Application failed to respond on every route. The browser surfaced it as a CORS error (no Access-Control-Allow-Origin), but the API was simply not reachable: no healthy Railway replica.

Root cause

The Railway deploy was failing at the healthcheck step, not at boot. Deploy logs show the app starts fine (Uvicorn running on http://0.0.0.0:8000, Application startup complete), but /health returns "service unavailable" on all 11 attempts.

backend/Dockerfile hardcoded --port 8000. Railway assigns a dynamic $PORT and runs its platform healthcheck (healthcheckPath: /health in railway.json) against that port. Nothing listens there, so the healthcheck never passes and the deploy is rejected.

This was a latent bug: healthcheckPath was added to railway.json after the last good deploy (#293), so #293 served fine on 8000 with no healthcheck enforcing reachability. Every deploy since (#316, #318) hit this and failed silently for days; prod only stayed up on the stale #293 image until that replica was replaced.

Fix

Bind uvicorn to ${PORT:-8000} (fallback preserves local/docker-compose), and make the internal Docker healthcheck read the same port. exec keeps uvicorn as PID 1 for graceful SIGTERM shutdown.

CMD exec uvicorn main:app --host 0.0.0.0 --port ${PORT:-8000} --proxy-headers

Note for reviewer / on merge

This fix unblocks the deploy pipeline, so merging it will deploy the backend changes from #316 (durable repo-state) and #318 (eval harness) to prod for the first time — they were merged to main but never actually shipped because of this bug. Both passed CI/CodeRabbit; flagging so the first green deploy is expected to carry that code.

Testing

• ${PORT:-8000} expansion verified (set -> dynamic port, unset -> 8000).
• Real validation is the next Railway deploy's healthcheck passing.

Summary by CodeRabbit

• Chores
  • Updated backend container configuration to support dynamic port assignment, enabling the service to adapt to hosting platforms that dynamically allocate ports at runtime. This ensures reliable operation across different deployment environments.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 61f93919-10c8-4db4-ba0e-d67c753522c3

📥 Commits

Reviewing files that changed from the base of the PR and between 022ef14 and 1ce41ee.

📒 Files selected for processing (1)

• backend/Dockerfile

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📝 Walkthrough

Walkthrough

The pull request modifies backend/Dockerfile to support Railway's dynamic runtime port assignment. The healthcheck now queries http://localhost:$PORT/health instead of hardcoding port 8000, and the startup command uses shell-expanded ${PORT:-8000} to bind uvicorn to the provided port environment variable with 8000 as fallback.

Changes

Dynamic Port Support

Layer / File(s)	Summary
Healthcheck and startup command for runtime port binding backend/Dockerfile	Healthcheck probes use the $PORT environment variable with 8000 fallback; startup command changed to shell form with proper variable expansion for --port ${PORT:-8000} binding instead of hardcoded port configuration.

Estimated Code Review Effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly Related PRs

• OpenCodeIntel/opencodeintel#310: Both PRs address Railway port/healthcheck boot behavior by adjusting how uvicorn binds to the correct $PORT and passes the /health probe on startup.

Poem

🐰 A port that shifts with the Railway wind,
No hardcoded eight-thou will pin us in,
The health check hops, the startup flies,
Dynamic binding—how the server thrives! 🚂✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly addresses the main change: binding uvicorn to Railway's dynamic $PORT environment variable to fix a production deployment healthcheck failure. It is specific, concise, and accurately reflects the core problem being solved.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
opencodeintel	Ignored	Preview	Jun 11, 2026 9:04pm