The first release that got far enough to report its own failure said
EADDRINUSE 127.0.0.1:4101: the CultNet private command plane. I gave the
HTTP listener a candidate bind and never noticed Heimdall has a second
listener on a fixed port, so the candidate collided with the incumbent and
died before it could warm.
A fixed private port makes coexistence impossible, which is the premise the
whole warm-then-cutover rests on. The private plane belongs to the same
generation as the HTTP listener, so under Idunn its port is derived from
the assigned candidate port with a fixed offset. Each generation gets its
own pair, and the published command-boundary endpoint stays truthful
because it reads the same config value. Outside Idunn the configured port
is unchanged.
The offset is large enough that a derived port cannot land inside the
route's candidate range and collide with another generation's HTTP
listener.
57 tests, 56 pass and the machine-id-bound one skipped on Windows.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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