Let me first look at how your application is loading the audio files to understand the CORS requirements.

[1 tool called]

Looking at your code, I can see the `TrackCache` module uses `fetch()` to cache audio files from `feed.falsefinish.club`. For this to work when your player is hosted on `echo-reality.com`, the server at `feed.falsefinish.club` needs to send proper CORS headers.

## What the owner of falsefinish.club needs to do

The server hosting the audio files must add these HTTP response headers:

```
Access-Control-Allow-Origin: https://echo-reality.com
Access-Control-Allow-Methods: GET, HEAD, OPTIONS
Access-Control-Expose-Headers: ETag, Last-Modified, Content-Length
```

The `Expose-Headers` part is important because your `TrackCache` reads `ETag` and `Last-Modified` headers for cache validation (lines 1539-1554 in your code).

### Server-specific configurations:

**Nginx:**
```nginx
location / {
    add_header 'Access-Control-Allow-Origin' 'https://echo-reality.com' always;
    add_header 'Access-Control-Allow-Methods' 'GET, HEAD, OPTIONS' always;
    add_header 'Access-Control-Expose-Headers' 'ETag, Last-Modified, Content-Length' always;
    
    # Handle preflight requests
    if ($request_method = 'OPTIONS') {
        add_header 'Access-Control-Allow-Origin' 'https://echo-reality.com';
        add_header 'Access-Control-Allow-Methods' 'GET, HEAD, OPTIONS';
        add_header 'Access-Control-Max-Age' 86400;
        add_header 'Content-Length' 0;
        return 204;
    }
}
```

**Apache (.htaccess):**
```apache
<IfModule mod_headers.c>
    Header set Access-Control-Allow-Origin "https://echo-reality.com"
    Header set Access-Control-Allow-Methods "GET, HEAD, OPTIONS"
    Header set Access-Control-Expose-Headers "ETag, Last-Modified, Content-Length"
</IfModule>
```

**Cloudflare (if used):** Add a Transform Rule or use a Cloudflare Worker to inject headers.

**S3/CloudFront:** Configure CORS in the bucket settings:
```json
[
    {
        "AllowedOrigins": ["https://echo-reality.com"],
        "AllowedMethods": ["GET", "HEAD"],
        "AllowedHeaders": ["*"],
        "ExposeHeaders": ["ETag", "Last-Modified", "Content-Length"],
        "MaxAgeSeconds": 86400
    }
]
```

### For development/testing

During development, you might want to allow multiple origins. Use a wildcard temporarily:
```
Access-Control-Allow-Origin: *
```

But for production, always specify the exact origin (`https://echo-reality.com`) for security.

### Why this matters for your code

Your `TrackCache.isStale()` function (lines 1519-1568) makes HEAD requests to check if files have changed. Without CORS headers:
1. The `fetch()` calls fail with CORS errors
2. Your code falls back to direct URLs (line 1753-1756), which works for playback but bypasses caching
3. The `ETag` and `Last-Modified` headers won't be readable even if fetches succeed partially

The current fallback behavior is good defensive code, but to enable actual caching benefits, those headers must be configured on `feed.falsefinish.club`.