When a background worker can't spawn because its cwd no longer exists, the job is marked permanently crashed instead of looping respawn attempts:
working directory no longer exists: <cwd>
[<reason> — this job cannot be respawned]The same path also fires the new tengu_bg_spawn_cwd_gone telemetry event.
Evidence
Background spawn cwd-gone (search for "working directory no longer exists:" and "this job cannot be respawned").
Strings lifted out of the shipped bundle, so the claim above can be checked against them.