Core Lightning node not working, not available

Support and Troubleshooting
1

I downloaded the Core Lightning app about a year ago because they had implemented BOLT12. I only opened a few channels. I kept the app updated, but I never really used it. Now, today, I try to start the Core Lightning app and I am immediately faced with “Safari can’t open the page ‘Umbrel.local:2103’ because the server unexpectedly dropped the connection.” I also have RTL (Core) app, and this too reports that it cannot connect to the Core Lightning Server (error 503).

What gives? It worked the last time that I used it. The app is up-to-date, and I’ve restarted the app, and I’ve even restarted the whole Umbrel Home device. Bitcoin app and default Lightning Node app are both working just fine. The only thing I can think of is that I haven’t updated my Bitcoin node to the latest version, I’m currently on Bitcoin Core 28.1.0. But, why should that matter?

Does anybody have any suggestions? Edit: I just clicked on “troubleshoot” and I downloaded the Core Lightning log file. It’s attached here.

Edit 2: I suppose, in the meantime, I can just feed this log to ChatGPT. Maybe it can provide some useful insight.

Edit 3: ChatGPT’s response–

Short version: lightningd never comes up, so there is no RPC socket for the UI to talk to. Everything else is just waiting and then failing.

What the log shows

  • The app-proxy is waiting for the Core Lightning UI on port 2103, which never opens, so Safari drops the connection.

  • The REST layer starts, but immediately errors because it cannot connect to the Core Lightning RPC socket /root/.lightning/bitcoin/lightning-rpc → ECONNREFUSED. This repeats in a loop.

  • lightningd prints only its banner and two deprecation messages referencing options in your config, then nothing further. No “RPC ready” or similar comes after that.

    • **BROKEN** lightningd: DEPRECATED API USED experimental-offers

    • Config file … line 2: experimental-onion-messages: --experimental-onion-message is now enabled by default

  • The REST layer also notes it is looking for lightning-rpc and then tries the bitcoin subdir, again failing because the socket never appears.

Put together: the RPC socket never gets created, which means lightningd is aborting very early or never finishing startup. That is why RTL shows 503 and the UI on :2103 never comes up.

Likely cause

The only concrete hints from lightningd before it goes silent are the two deprecated options in your config (experimental-offers, experimental-onion-messages). Newer Core Lightning releases enabled or removed these flags, and keeping them in the config can cause early aborts on some builds. Since we do not see any later log lines from lightningd, pruning those options is the fastest, low-risk first fix.

Edit 4: Nevermind, ChatGPT identified the problem. I had added some lines to my config file and that was messing it up after I updated to the latest version. I backed-up and renamed the config file and now the app boots normally. Problem solved!

umbrel_core-lightning_2025-08-23_21-18.log (88.1 KB)