A hook client that could not join because the active daemon runs a
DIFFERENT build reported the conflict on stderr only - and stdout is
the only hook channel Claude Code surfaces, so in-session the result
was eternal silent skips. Worse, the connect-failure path classified a
conflicted daemon as ABSENT and suggested 'daemon start', which cannot
heal a build conflict. This is the rc.1-over-0.9.0 experience in
#1388/#1335: install the new build, the old warm daemon keeps running,
and every hook goes quiet.
Both failure sites now emit a throttled stdout systemMessage naming the
real state (active daemon runs a different build) with the actionable
step ('daemon stop', next command starts a matching daemon). The
version-cohort conflict path keeps its unconditional stderr detail; the
connect-conflict path now prints the formatted conflict to stderr too.
Test infrastructure: a CBM_ENABLE_TEST_SEAMS-only env override
(CBM_TEST_HOOK_CLIENT_BUILD) lets one binary present a foreign build
fingerprint as a hook client, so the conflict is reproducible without a
second build. tests/test_hook_conflict_notice.sh (scripts/test.sh step
5d, on the step-5 TEST_SEAMS binary) asserts fail-open exit 0 + the
stderr conflict + the stdout systemMessage with restart guidance. RED
before the fix (empty stdout), GREEN after, RED again on revert.
Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>
Martin Vogel
716f1d683c