MercurALPHA
Sign inTry without an account

Troubleshooting

Grouped by what you see, with the exact text the relay returns.

I sent a request and nothing appeared in the log

Three causes, in order of likelihood:

  1. The endpoint runs in proxy mode. Proxy mode forwards without recording. Stop the endpoint and start it again in Log and Proxy if you want both.
  2. The list has not caught up yet. It polls every few seconds; Refresh above the list fetches immediately.
  3. The request never arrived. Run the request with curl -i and read the status. A recorded request always returns something from the relay, so a connection error means it did not reach us at all.

I get 204 No Content and my local service sees nothing

That is log mode working as designed: the relay records the request and answers 204 without forwarding. Restart the endpoint in Proxy mode or Log and Proxy to reach your machine.

I get 503 No agent for client

The relay has no live agent for that endpoint. Any of these produce it:

  • the desktop app is not running, or is signed out
  • the app lost its network, and the claim lapsed after 15 seconds without a heartbeat
  • the endpoint was started but the agent has not registered yet — wait a moment and retry
  • the hostname does not match an endpoint, usually a typo in the subdomain
  • the endpoint speaks a different protocol than the request, for example plain HTTP sent to a WebSocket endpoint

I get 503 Server is not running

The endpoint exists but is stopped, starting, or failed. Open it in the console and press Run Proxy. Seeing this immediately after pressing Run is normal for a moment, while the agent registers.

I get 403 Forbidden

The endpoint is not public and your address is not on its list. Add the caller's address to the IP whitelist, or set Public access to true. Remember that the caller is often not you — a webhook provider calls from its own ranges.

I get 429

You reached the monthly request quota for your plan and the body says Monthly HTTP request quota exceeded. Quotas reset monthly; see limits.

I get 503 Too many concurrent sessions

More connections were open at once than your plan allows. In-flight requests finish and free the slots. Long-lived requests hold a slot for their whole duration, so a slow endpoint reaches this sooner.

I get 502 with connect ECONNREFUSED 127.0.0.1:3000

The relay reached your machine and your machine refused the connection. Your local process is not listening, or is listening on a different port than the endpoint's Local port. Check with curl -i localhost:3000 first — if that fails, the problem is entirely local.

I get 502 Bad Gateway with no detail

The connection between the relay and your agent failed mid-request. Stop and start the endpoint, then retry.

My WebSocket or TCP connection is dropped without an error

Rejections before a WebSocket handshake completes close the socket without an HTTP response, so a client only reports a reset connection. The causes are the same as the HTTP list above: unknown host, stopped endpoint, address not allowed, no agent, quota, or session limit. Check the endpoint in the console to see which applies.

WebSocket and raw TCP also require a plan that includes them, which no purchasable plan does today.

The console will not let me run the endpoint

  • Server is in use by <hostname> — another machine holds this endpoint. Stop it there first.
  • Running this mode requires the Electron app with a connected device agent — forwarding needs the desktop app; the browser can run log mode only.
  • Server must be stopped before changing its run mode — stop it, then start it in the mode you want.
  • Device agent credential is invalid — sign in again in the desktop app so it registers the machine anew.

A response body is missing from a recorded request

Response recording is a separate setting from request recording, and it only applies in forwarding modes. Enable Save response body & headers when starting the endpoint. Log mode never has a response to store, because nothing is forwarded.

Old requests disappeared

Each plan caps how many requests an endpoint keeps, and the oldest are dropped past the cap. Everything is deleted 30 days after arrival regardless. See limits.