HOST131: Response headers rejected
What this means
A proxy in front of the store rejects the server's responses for having too many headers.
A cache or proxy layer (commonly Varnish) enforces a limit on response header count or size. The store's lightweight endpoints fit, but full API responses exceed the limit and come back as 503s from the proxy, not from WordPress. The limit must be raised on that layer.
What to do
Export diagnostics and contact support. Retry after making the change above; retrying without it will fail the same way.
Your data
No order or product data is affected.
Troubleshoot
- On Varnish, raise http_max_hdr (header count) and http_resp_hdr_len / http_resp_size (sizes).
- Ask the host which proxy layer returns the 503 — the WordPress error log will show nothing because the request never fails there.
- A quick check: the store's /wcpos/v2/ping answers fine while data endpoints 503.
Where to look
When WCPOS can save this error, it is recorded on the device that raised it. Open Store health → Logs (the heart-pulse icon at the bottom of the navigation drawer), find the entry marked with this code and expand it: the expanded row shows the plain-language reason and the context captured at the moment of failure. For a store request, that context may include the server’s own error code (serverCode), the HTTP status or the endpoint; the fields shown depend on where the failure occurred. When reporting a problem, use Copy debug info at the top of the Logs screen (Share debug info on phones and tablets) rather than screenshots: it bundles the app version, connection state and the most recent errors. Logs are kept for at most 30 days, so collect them while the problem is fresh. Also copy any browser-console error that appeared before the POS was able to write its own log entry.
Details
- Code:
HOST131(RESPONSE_HEADERS_REJECTED) - Severity: error
- Introduced in: WCPOS 1.10.0