Both spawn paths (startHermes, spawnPoolBackend) duplicated the same
resolve -> log-fallback -> foreign-check -> throw dance. Collapse it into
adoptServedDashboardToken(baseUrl, spawnToken, {childAlive, label}) in
dashboard-token.cjs; childAlive is a thunk so liveness is sampled after
the fetch. Drop the redundant backendPool.delete in the pool's throw
path (the child exit/error handlers already own pool eviction).
Validated end-to-end against a real web_server.py backend, not just
units: token-injection regex vs the actual served index.html, foreign
refusal (dead child + live squatter), benign drift adoption, and the
401-vs-200 token auth split on /api/sessions.
The served-token fallback adopts whatever token the dashboard HTML
injects. That is correct when our own child regenerated the token (env
pin lost across a shell-wrapped spawn), but wrong when the readiness
probe answered from a process we did not spawn: /api/status is public,
so an orphaned dashboard squatting the port passes waitForHermes while
our child dies on the bind conflict. Silently adopting that process's
token would authenticate the renderer against a foreign backend,
possibly on the wrong profile.
Discriminate on child liveness: the desktop pins
HERMES_DASHBOARD_SESSION_TOKEN on every spawn, so a live child always
serves our token. Served-token mismatch + dead child = foreign backend;
fail the boot loudly instead of connecting. Mismatch + live child keeps
the adopt-served-token salvage from #43720.
