Web UI fonts and lazy-loaded scripts ignore X-Forwarded-Prefix

[Warr1024]

LocalAI version:

LocalAI v4.7.1 (b224c96)

Docker image:
localai/localai@sha256:66c8824a4bd85f24c55c14b916ecac14550c684d64c7b8fcb5000952d665c30a

Environment, CPU architecture, OS, and Version:

Debian GNU/Linux 13 (trixie) x86_64

Linux internal-host 6.12.94+deb13-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.12.94-1 (2026-06-20) x86_64 GNU/Linux

Describe the bug

I am serving the LocalAI Web UI through nginx under /llm/.

nginx preserves the /llm/ path when proxying to LocalAI and sends:

X-Forwarded-Prefix: /llm/

Resources referenced directly by the initial HTML are correctly prefixed. However, some font files and lazy-loaded JavaScript chunks are later requested from the origin root.

The resulting 404s cause UI icons to appear as missing-glyph “tofu” characters and may prevent parts of the management UI from loading correctly.

A secondary cache-busted favicon request also returns 404, although that has no visible impact because the initial favicon loads successfully.

Reverse proxy configuration

The relevant nginx configuration is:

location = /llm {
    return 302 llm/;
}

location /llm/ {
    proxy_pass http://internal-host.local:47080;

    proxy_http_version 1.1;
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header X-Forwarded-Host $host:$server_port;
    proxy_set_header X-Forwarded-Prefix /llm/;
}

Because proxy_pass has no URI component, nginx forwards /llm/... upstream without stripping the prefix.

The public hostname is intentionally replaced with my.redacted.domain because the instance is not intended for public discovery or third-party testing.

To Reproduce

1. Run the LocalAI version and container image listed above.
2. Proxy LocalAI through nginx under /llm/ using the configuration above.
3. Open /llm/app.
4. Open the browser Network panel.
5. Navigate through the management UI to trigger lazy-loaded components.
6. Observe 404 responses for root-level JavaScript and font resources under /assets/....

Expected behavior

When X-Forwarded-Prefix: /llm/ is supplied, all same-origin Web UI resources should remain under /llm/, including resources loaded later from compiled JavaScript or CSS.

Actual behavior

The initial HTML is prefix-aware, but some URLs embedded in compiled assets or generated at runtime bypass /llm/ and return 404.

The JavaScript and font failures have visible usability impact. The favicon failure appears to be a related but low-impact symptom.
Logs

Additional context

Evidence

The initial HTML contains correctly prefixed URLs:

<base href="https://my.redacted.domain:443/llm/" />
<link rel="icon" type="image/svg+xml" href="/llm/favicon.svg" />
<script type="module" crossorigin src="/llm/assets/index-CUPsCTJ1.js"></script>
<link rel="modulepreload" crossorigin href="/llm/assets/chunk-Cyuzqnbw.js">
<link rel="modulepreload" crossorigin href="/llm/assets/jsx-runtime-xIJTzhZo.js">
<link rel="modulepreload" crossorigin href="/llm/assets/api-CbRzmvjD.js">
<link rel="stylesheet" crossorigin href="/llm/assets/index-B5EK2jBS.css">

These initial resources load successfully.

The loaded JavaScript subsequently requests additional chunks from paths such as:

/assets/<chunk>.js

rather than:

/llm/assets/<chunk>.js

Font resources are similarly requested from paths such as:

/assets/<font>.woff2

rather than:

/llm/assets/<font>.woff2

The root-level requests return 404. Missing font resources cause icons in the management UI to render as tofu characters.

There is also a lower-impact request after startup:

/favicon.svg?v=<timestamp>

It returns 404 because it omits /llm/. The favicon remains visible because the initial /llm/favicon.svg request succeeded.

Related prior work and likely cause

This appears related to #9145 and its fix in #9614.

The existing handling correctly prefixes references in the initial HTML, but the observed behavior suggests it does not cover:

• lazy-chunk URLs embedded in compiled JavaScript;
• font URLs embedded in compiled CSS;
• root-absolute URLs generated later by frontend JavaScript.

The frontend should consistently resolve runtime and compiled asset URLs against the configured base path rather than the origin root.