This was interesting, so I wanted to try to reproduce it, and it’s true. Please excuse the old versions.

jstimpson@myhost:~$ ./bin/myapp remote
Erlang/OTP 25 [erts-13.2.2.15] [source] [64-bit] [smp:2:2] [ds:2:2:10] [async-threads:1] [jit:ns]

Interactive Elixir (1.15.8) - press Ctrl+C to exit (type h() ENTER for help)
iex(myapp@myhost)1> spawn_link(fn -> :timer.sleep(100000000) end)
#PID<0.5573.0>
iex(myapp@myhost)2> :erlang.is_process_alive(pid(0, 5573, 0))
true
iex(myapp@myhost)3>
BREAK: (a)bort (A)bort with dump (c)ontinue (p)roc info (i)nfo
       (l)oaded (v)ersion (k)ill (D)b-tables (d)istribution
a
jstimpson@myhost:~$ ./bin/myapp remote
Erlang/OTP 25 [erts-13.2.2.15] [source] [64-bit] [smp:2:2] [ds:2:2:10] [async-threads:1] [jit:ns]

Interactive Elixir (1.15.8) - press Ctrl+C to exit (type h() ENTER for help)
iex(myapp@myhost)1> :erlang.is_process_alive(pid(0, 5573, 0))
true

The behavior in the remote shell case is surprising to me personally, since my background is mostly in Erlang, in which it’s different. To demonstrate:

Terminal A:

~ ❯❯❯ iex --sname server # or `erl -sname server`
Erlang/OTP 27 [erts-15.2.6] [source] [64-bit] [smp:10:10] [ds:10:10:10] [async-threads:1] [jit]

Interactive Elixir (1.18.3) - press Ctrl+C to exit (type h() ENTER for help)
iex(server@Mac)1>

Terminal B:

~ ❯❯❯ erl -remsh server
Erlang/OTP 27 [erts-15.2.6] [source] [64-bit] [smp:10:10] [ds:10:10:10] [async-threads:1] [jit]

Eshell V15.2.6 (press Ctrl+G to abort, type help(). for help)
(server@Mac)1> spawn_link(fun() -> timer:sleep(1000000000) end).
<0.127.0>
(server@Mac)2>
BREAK: (a)bort (A)bort with dump (c)ontinue (p)roc info (i)nfo
       (l)oaded (v)ersion (k)ill (D)b-tables (d)istribution
a
~ ❯❯❯ erl -remsh server
Erlang/OTP 27 [erts-15.2.6] [source] [64-bit] [smp:10:10] [ds:10:10:10] [async-threads:1] [jit]

Eshell V15.2.6 (press Ctrl+G to abort, type help(). for help)
(server@Mac)1> is_process_alive(pid(0,127,0)).
false
(server@Mac)2>

Coming from Erlang, I had a natural expectation that halting an iex remote shell would trigger links on processes that were started in that shell. My expectation turned out to be wrong, but I can see how this would end up causing unexpected system behavior during debugging sessions. I will attempt a PR to the iex docs to explain the behavior, as I don’t see anything in there currently (although I might have missed it!)

Edit: doc change merged to elixir main

Found the explanation while discussing with Claude LLM, and the answer is as simple as possible: when shutting down IEx with “Ctrl + C” and “a” the process exits normally, so the link is not triggered, because it is not a crash.