build(ui): bump nginx to 1.31-alpine

[aharden]

TLDR

Problem this solves:

• upgrades nginx to current version; v1.27 stopped receiving security updates on 24 Jun 2025
• reference: https://endoflife.date/nginx

How it solves it:

• updates nginx version reference in ui/Dockerfile

Relevant issues

Linear ticket

Pre-Submission checklist

Please complete all items before asking a LiteLLM maintainer to review your PR

• I have added meaningful tests
• My PR passes all CI/CD checks (e.g., lint, format, unit tests)
• My PR's scope is as isolated as possible; it only solves 1 specific problem
• I have received a Greptile Confidence Score of at least 4/5 before requesting a maintainer review (Greptile reviews automatically once the PR is opened; only comment @greptileai to re-request a review after pushing changes)

Delays in PR merge?

If you're seeing a delay in your PR being merged, ping the LiteLLM Team on Slack (#pr-review).

Screenshots / Proof of Fix

docker build -f ui/Dockerfile -t litellm-ui:nginx129-test .
docker run --rm --name litellm-ui-test -d -p 3000:3000 litellm-ui:nginx129-test
docker exec litellm-ui-test nginx -v
curl -I http://localhost:3000/
docker logs litellm-ui-test
docker stop litellm-ui-test

What to look for:

• nginx -v should print nginx version: nginx/1.31.x
• the curl -I should return HTTP/1.1 200 OK and serve the static export headers cleanly
• docker logs should show no startup errors/warnings from nginx

Type

🚄 Infrastructure

Changes

Upgrades nginx from 1.27.5 to 1.31.x (current)

Final Attestation

• The tests check the right things, including the edge cases, and regressions in the respective real-world customer use-cases are not possible after this PR

[greptile-apps]

Greptile Summary

Updates the UI runtime container from nginx:1.27-alpine to nginx:1.31-alpine.

Confidence Score: 5/5

The PR appears safe to merge with no actionable defects identified.

The change is isolated to the nginx runtime image tag, and the repository's UI configuration does not rely on version-specific modules, directives, or image internals that would make the upgrade incorrect.

Important Files Changed

Filename	Overview
ui/Dockerfile	Updates only the nginx runtime image version; the existing configuration uses standard nginx directives with no identified incompatibility.

_{Reviews (1): Last reviewed commit: "build(ui): bump nginx to 1.31-alpine" | Re-trigger Greptile}

[ryan-crabbe-berri]

Thank you!

[devin-ai-integration]

Superseded by #38541, which re-applied this change on current staging with the conflict resolved and is now merged. Thanks!